The Scientific World Journal: Communications http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Visual Quality Assessment after Network Transmission Incorporating NS2 and Evalvid Tue, 15 Apr 2014 13:55:23 +0000 http://www.hindawi.com/journals/tswj/2014/267403/ On the basis of Evalvid tool integrated in NS2 (Network Simulator version 2), the paper gets new set of tools, myEvalvid, to establish the simulation and evaluation platform for multimedia transmission. Then the paper investigates the effects of various influence factors when multimedia information is transmitted in the network and the relationships among these factors. Based on the analysis, the paper gets different evaluation models, respectively. In this paper, we study the impact on performance of several basic source and network parameters of video streams, namely, GOP (Group of Pictures) pattern, compression quantitative parameters, packet length, and packet error rate. Simulation results show that different parameters lead to different distortion levels which are calculated according to the reconstruction images at the receiver and the original images. The experimental results show that the video transmission and quality evaluation model we designed can evaluate multimedia transmission performance over complex environment very well. Zhengyou Wang, Wan Wang, Yanhui Xia, Zheng Wan, Jin Wang, Liying Li, and Cong Cai Copyright © 2014 Zhengyou Wang et al. All rights reserved. Adaptive Phase Rolling for Opportunistic Beamforming in OFDMA Systems with a Small Number of Users Mon, 14 Apr 2014 08:58:33 +0000 http://www.hindawi.com/journals/tswj/2014/625421/ The performance of opportunistic beamforming might be degraded if the number of users is small. This paper proposes an adaptive opportunistic beamforming technique for orthogonal frequency division multiple access systems, which can produce good results even with a small number of users. This paper also proposes a modified proportional fairness scheduling algorithm, which can further improve the performance of the proposed opportunistic beamforming technique. Minjoong Rim Copyright © 2014 Minjoong Rim. All rights reserved. Password-Only Authenticated Three-Party Key Exchange with Provable Security in the Standard Model Mon, 14 Apr 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/825072/ Protocols for password-only authenticated key exchange (PAKE) in the three-party setting allow two clients registered with the same authentication server to derive a common secret key from their individual password shared with the server. Existing three-party PAKE protocols were proven secure under the assumption of the existence of random oracles or in a model that does not consider insider attacks. Therefore, these protocols may turn out to be insecure when the random oracle is instantiated with a particular hash function or an insider attack is mounted against the partner client. The contribution of this paper is to present the first three-party PAKE protocol whose security is proven without any idealized assumptions in a model that captures insider attacks. The proof model we use is a variant of the indistinguishability-based model of Bellare, Pointcheval, and Rogaway (2000), which is one of the most widely accepted models for security analysis of password-based key exchange protocols. We demonstrated that our protocol achieves not only the typical indistinguishability-based security of session keys but also the password security against undetectable online dictionary attacks. Junghyun Nam, Kim-Kwang Raymond Choo, Junghwan Kim, Hyun-Kyu Kang, Jinsoo Kim, Juryon Paik, and Dongho Won Copyright © 2014 Junghyun Nam et al. All rights reserved. Characteristic Analysis on UAV-MIMO Channel Based on Normalized Correlation Matrix Mon, 14 Apr 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/206185/ Based on the three-dimensional GBSBCM (geometrically based double bounce cylinder model) channel model of MIMO for unmanned aerial vehicle (UAV), the simple form of UAV space-time-frequency channel correlation function which includes the LOS, SPE, and DIF components is presented. By the methods of channel matrix decomposition and coefficient normalization, the analytic formula of UAV-MIMO normalized correlation matrix is deduced. This formula can be used directly to analyze the condition number of UAV-MIMO channel matrix, the channel capacity, and other characteristic parameters. The simulation results show that this channel correlation matrix can be applied to describe the changes of UAV-MIMO channel characteristics under different parameter settings comprehensively. This analysis method provides a theoretical basis for improving the transmission performance of UAV-MIMO channel. The development of MIMO technology shows practical application value in the field of UAV communication. Gao Xi jun, Chen Zi li, and Hu Yong Jiang Copyright © 2014 Gao Xi jun et al. All rights reserved. Compressive Sensing Based Bayesian Sparse Channel Estimation for OFDM Communication Systems: High Performance and Low Complexity Thu, 10 Apr 2014 14:07:45 +0000 http://www.hindawi.com/journals/tswj/2014/927894/ In orthogonal frequency division modulation (OFDM) communication systems, channel state information (CSI) is required at receiver due to the fact that frequency-selective fading channel leads to disgusting intersymbol interference (ISI) over data transmission. Broadband channel model is often described by very few dominant channel taps and they can be probed by compressive sensing based sparse channel estimation (SCE) methods, for example, orthogonal matching pursuit algorithm, which can take the advantage of sparse structure effectively in the channel as for prior information. However, these developed methods are vulnerable to both noise interference and column coherence of training signal matrix. In other words, the primary objective of these conventional methods is to catch the dominant channel taps without a report of posterior channel uncertainty. To improve the estimation performance, we proposed a compressive sensing based Bayesian sparse channel estimation (BSCE) method which cannot only exploit the channel sparsity but also mitigate the unexpected channel uncertainty without scarifying any computational complexity. The proposed method can reveal potential ambiguity among multiple channel estimators that are ambiguous due to observation noise or correlation interference among columns in the training matrix. Computer simulations show that proposed method can improve the estimation performance when comparing with conventional SCE methods. Guan Gui, Li Xu, Lin Shan, and Fumiyuki Adachi Copyright © 2014 Guan Gui et al. All rights reserved. Code-Time Diversity for Direct Sequence Spread Spectrum Systems Thu, 10 Apr 2014 12:04:48 +0000 http://www.hindawi.com/journals/tswj/2014/146186/ Time diversity is achieved in direct sequence spread spectrum by receiving different faded delayed copies of the transmitted symbols from different uncorrelated channel paths when the transmission signal bandwidth is greater than the coherence bandwidth of the channel. In this paper, a new time diversity scheme is proposed for spread spectrum systems. It is called code-time diversity. In this new scheme, spreading codes are used to transmit one data symbol over successive symbols interval. The diversity order in the proposed scheme equals to the number of the used spreading codes multiplied by the number of the uncorrelated paths of the channel . The paper represents the transmitted signal model. Two demodulators structures will be proposed based on the received signal models from Rayleigh flat and frequency selective fading channels. Probability of error in the proposed diversity scheme is also calculated for the same two fading channels. Finally, simulation results are represented and compared with that of maximal ration combiner (MRC) and multiple-input and multiple-output (MIMO) systems. A. Y. Hassan Copyright © 2014 A. Y. Hassan. All rights reserved. A Complete Hierarchical Key Management Scheme for Heterogeneous Wireless Sensor Networks Thu, 10 Apr 2014 11:12:46 +0000 http://www.hindawi.com/journals/tswj/2014/816549/ Heterogeneous cluster-based wireless sensor networks (WSN) attracted increasing attention recently. Obviously, the clustering makes the entire networks hierarchical; thus, several kinds of keys are required for hierarchical network topology. However, most existing key management schemes for it place more emphasis on pairwise key management schemes or key predistribution schemes and neglect the property of hierarchy. In this paper, we propose a complete hierarchical key management scheme which only utilizes symmetric cryptographic algorithms and low cost operations for heterogeneous cluster-based WSN. Our scheme considers four kinds of keys, which are an individual key, a cluster key, a master key, and pairwise keys, for each sensor node. Finally, the analysis and experiments demonstrate that the proposed scheme is secure and efficient; thus, it is suitable for heterogeneous cluster-based WSN. Chien-Ming Chen, Xinying Zheng, and Tsu-Yang Wu Copyright © 2014 Chien-Ming Chen et al. All rights reserved. Reducing Side Effects of Hiding Sensitive Itemsets in Privacy Preserving Data Mining Thu, 10 Apr 2014 08:51:11 +0000 http://www.hindawi.com/journals/tswj/2014/235837/ Data mining is traditionally adopted to retrieve and analyze knowledge from large amounts of data. Private or confidential data may be sanitized or suppressed before it is shared or published in public. Privacy preserving data mining (PPDM) has thus become an important issue in recent years. The most general way of PPDM is to sanitize the database to hide the sensitive information. In this paper, a novel hiding-missing-artificial utility (HMAU) algorithm is proposed to hide sensitive itemsets through transaction deletion. The transaction with the maximal ratio of sensitive to nonsensitive one is thus selected to be entirely deleted. Three side effects of hiding failures, missing itemsets, and artificial itemsets are considered to evaluate whether the transactions are required to be deleted for hiding sensitive itemsets. Three weights are also assigned as the importance to three factors, which can be set according to the requirement of users. Experiments are then conducted to show the performance of the proposed algorithm in execution time, number of deleted transactions, and number of side effects. Chun-Wei Lin, Tzung-Pei Hong, and Hung-Chuan Hsu Copyright © 2014 Chun-Wei Lin et al. All rights reserved. In-Band Asymmetry Compensation for Accurate Time/Phase Transport over Optical Transport Network Thu, 10 Apr 2014 08:18:44 +0000 http://www.hindawi.com/journals/tswj/2014/408613/ The demands of precise time/phase synchronization have been increasing recently due to the next generation of telecommunication synchronization. This paper studies the issues that are relevant to distributing accurate time/phase over optical transport network (OTN). Each node and link can introduce asymmetry, which affects the adequate time/phase accuracy over the networks. In order to achieve better accuracy, protocol level full timing support is used (e.g., Telecom-Boundary clock). Due to chromatic dispersion, the use of different wavelengths consequently causes fiber link delay asymmetry. The analytical result indicates that it introduces significant time error (i.e., phase offset) within 0.3397 ns/km in C-band or 0.3943 ns/km in L-band depending on the wavelength spacing. With the proposed scheme in this paper, the fiber link delay asymmetry can be compensated relying on the estimated mean fiber link delay by the Telecom-Boundary clock, while the OTN control plane is responsible for processing the fiber link delay asymmetry to determine the asymmetry compensation in the timing chain. Sammy Siu, Wen-Hung Tseng, Hsiu-fang Hu, Shinn-Yan Lin, Chia-Shu Liao, and Yi-Liang Lai Copyright © 2014 Sammy Siu et al. All rights reserved. Content Patterns in Topic-Based Overlapping Communities Wed, 09 Apr 2014 09:19:51 +0000 http://www.hindawi.com/journals/tswj/2014/105428/ Understanding the underlying community structure is an important challenge in social network analysis. Most state-of-the-art algorithms only consider structural properties to detect disjoint subcommunities and do not include the fact that people can belong to more than one community and also ignore the information contained in posts that users have made. To tackle this problem, we developed a novel methodology to detect overlapping subcommunities in online social networks and a method to analyze the content patterns for each subcommunities using topic models. This paper presents our main contribution, a hybrid algorithm which combines two different overlapping sub-community detection approaches: the first one considers the graph structure of the network (topology-based subcommunities detection approach) and the second one takes the textual information of the network nodes into consideration (topic-based subcommunities detection approach). Additionally we provide a method to analyze and compare the content generated. Tests on real-world virtual communities show that our algorithm outperforms other methods. Sebastián A. Ríos and Ricardo Muñoz Copyright © 2014 Sebastián A. Ríos and Ricardo Muñoz. All rights reserved. Multichannel Broadcast Based on Home Channel for Cognitive Radio Sensor Networks Wed, 09 Apr 2014 09:07:09 +0000 http://www.hindawi.com/journals/tswj/2014/725210/ Considering the limited resources and the dynamic spectrum distribution in the cognitive radio sensor networks (CRSN), a half-duplex Multichannel broadcast protocol for CRSN is presented based on the home channel. This protocol maintains the networks topology only through the home channel, so there is no need for the public channel to transmit the control information and no need for the synchronization. After network initialization, node broadcasts data via home channel in half-duplex transmission way. The simulation results show that, compared with complete broadcast, the proposed protocol effectively reduces broadcast delay and overhead. Fanzi Zeng, Yuting Tang, and Jianjie Pu Copyright © 2014 Fanzi Zeng et al. All rights reserved. Separable and Error-Free Reversible Data Hiding in Encrypted Image with High Payload Sun, 06 Apr 2014 06:23:56 +0000 http://www.hindawi.com/journals/tswj/2014/604876/ This paper proposes a separable reversible data-hiding scheme in encrypted image which offers high payload and error-free data extraction. The cover image is partitioned into nonoverlapping blocks and multigranularity encryption is applied to obtain the encrypted image. The data hider preprocesses the encrypted image and randomly selects two basic pixels in each block to estimate the block smoothness and indicate peak points. Additional data are embedded into blocks in the sorted order of block smoothness by using local histogram shifting under the guidance of the peak points. At the receiver side, image decryption and data extraction are separable and can be free to choose. Compared to previous approaches, the proposed method is simpler in calculation while offering better performance: larger payload, better embedding quality, and error-free data extraction, as well as image recovery. Zhaoxia Yin, Bin Luo, and Wien Hong Copyright © 2014 Zhaoxia Yin et al. All rights reserved. Modeling and Simulation of Complex Network Attributes on Coordinating Large Multiagent System Thu, 03 Apr 2014 08:25:13 +0000 http://www.hindawi.com/journals/tswj/2014/412479/ With the expansion of distributed multiagent systems, traditional coordination strategy becomes a severe bottleneck when the system scales up to hundreds of agents. The key challenge is that in typical large multiagent systems, sparsely distributed agents can only communicate directly with very few others and the network is typically modeled as an adaptive complex network. In this paper, we present simulation testbed CoordSim built to model the coordination of network centric multiagent systems. Based on the token-based strategy, the coordination can be built as a communication decision problem that agents make decisions to target communications and pass them over to the capable agents who will potentially benefit the team most. We have theoretically analyzed that the characters of complex network make a significant difference with both random and intelligent coordination strategies, which may contribute to future multiagent algorithm design. Yang Xu, Xiang Li, and Ming Liu Copyright © 2014 Yang Xu et al. All rights reserved. Discovering the Influences of Complex Network Effects on Recovering Large Scale Multiagent Systems Wed, 02 Apr 2014 13:41:00 +0000 http://www.hindawi.com/journals/tswj/2014/407639/ Building efficient distributed coordination algorithms is critical for the large scale multiagent system design, and the communication network has been shown as a key factor to influence system performance even under the same coordination protocol. Although many distributed algorithm designs have been proved to be feasible to build their functions in the large scale multiagent systems as claimed, the performances may not be stable if the multiagent networks were organized with different complex network topologies. For example, if the network was recovered from the broken links or disfunction nodes, the network topology might have been shifted. Therefore, their influences on the overall multiagent system performance are unknown. In this paper, we have made an initial effort to find how a standard network recovery policy, MPLS algorithm, may change the network topology of the multiagent system in terms of network congestion. We have established that when the multiagent system is organized as different network topologies according to different complex network attributes, the network shifts in different ways. Those interesting discoveries are helpful to predict how complex network attributes influence on system performance and in turn are useful for new algorithm designs that make a good use of those attributes. Yang Xu, Pengfei Liu, Xiang Li, and Wei Ren Copyright © 2014 Yang Xu et al. All rights reserved. A Novel Joint Problem of Routing, Scheduling, and Variable-Width Channel Allocation in WMNs Wed, 02 Apr 2014 11:59:24 +0000 http://www.hindawi.com/journals/tswj/2014/754749/ This paper investigates a novel joint problem of routing, scheduling, and channel allocation for single-radio multichannel wireless mesh networks in which multiple channel widths can be adjusted dynamically through a new software technology so that more concurrent transmissions and suppressed overlapping channel interference can be achieved. Although the previous works have studied this joint problem, their linear programming models for the problem were not incorporated with some delicate constraints. As a result, this paper first constructs a linear programming model with more practical concerns and then proposes a simulated annealing approach with a novel encoding mechanism, in which the configurations of multiple time slots are devised to characterize the dynamic transmission process. Experimental results show that our approach can find the same or similar solutions as the optimal solutions for smaller-scale problems and can efficiently find good-quality solutions for a variety of larger-scale problems. Chun-Cheng Lin, Wan-Yu Liu, Chun-Hung Chou, and Der-Jiunn Deng Copyright © 2014 Chun-Cheng Lin et al. All rights reserved. A Coverage and Slicing Dependencies Analysis for Seeking Software Security Defects Wed, 02 Apr 2014 11:57:31 +0000 http://www.hindawi.com/journals/tswj/2014/463912/ Software security defects have a serious impact on the software quality and reliability. It is a major hidden danger for the operation of a system that a software system has some security flaws. When the scale of the software increases, its vulnerability has becoming much more difficult to find out. Once these vulnerabilities are exploited, it may lead to great loss. In this situation, the concept of Software Assurance is carried out by some experts. And the automated fault localization technique is a part of the research of Software Assurance. Currently, automated fault localization method includes coverage based fault localization (CBFL) and program slicing. Both of the methods have their own location advantages and defects. In this paper, we have put forward a new method, named Reverse Data Dependence Analysis Model, which integrates the two methods by analyzing the program structure. On this basis, we finally proposed a new automated fault localization method. This method not only is automation lossless but also changes the basic location unit into single sentence, which makes the location effect more accurate. Through several experiments, we proved that our method is more effective. Furthermore, we analyzed the effectiveness among these existing methods and different faults. Hui He, Dongyan Zhang, Min Liu, Weizhe Zhang, and Dongmin Gao Copyright © 2014 Hui He et al. All rights reserved. An Improved Clustering Algorithm of Tunnel Monitoring Data for Cloud Computing Wed, 02 Apr 2014 08:09:16 +0000 http://www.hindawi.com/journals/tswj/2014/630986/ With the rapid development of urban construction, the number of urban tunnels is increasing and the data they produce become more and more complex. It results in the fact that the traditional clustering algorithm cannot handle the mass data of the tunnel. To solve this problem, an improved parallel clustering algorithm based on k-means has been proposed. It is a clustering algorithm using the MapReduce within cloud computing that deals with data. It not only has the advantage of being used to deal with mass data but also is more efficient. Moreover, it is able to compute the average dissimilarity degree of each cluster in order to clean the abnormal data. Luo Zhong, KunHao Tang, Lin Li, Guang Yang, and JingJing Ye Copyright © 2014 Luo Zhong et al. All rights reserved. Identifying Network Public Opinion Leaders Based on Markov Logic Networks Tue, 01 Apr 2014 06:03:40 +0000 http://www.hindawi.com/journals/tswj/2014/268592/ Public opinion emergencies have important effect on social activities. Recognition of special communities like opinion leaders can contribute to a comprehensive understanding of the development trend of public opinion. In this paper, a network opinion leader recognition method based on relational data was put forward, and an opinion leader recognition system integrating public opinion data acquisition module, data characteristic selection, and fusion module as well as opinion leader discovery module based on Markov Logic Networks was designed. The designed opinion leader recognition system not only can overcome the incomplete data acquisition and isolated task of traditional methods, but also can recognize opinion leaders comprehensively with considerations to multiple problems by using the relational model. Experimental results demonstrated that, compared with the traditional methods, the proposed method can provide a more accurate opinion leader recognition and has good noise immunity. Weizhe Zhang, Xiaoqiang Li, Hui He, and Xing Wang Copyright © 2014 Weizhe Zhang et al. All rights reserved. SVM-Based Spectrum Mobility Prediction Scheme in Mobile Cognitive Radio Networks Sun, 30 Mar 2014 13:29:08 +0000 http://www.hindawi.com/journals/tswj/2014/395212/ Spectrum mobility as an essential issue has not been fully investigated in mobile cognitive radio networks (CRNs). In this paper, a novel support vector machine based spectrum mobility prediction (SVM-SMP) scheme is presented considering time-varying and space-varying characteristics simultaneously in mobile CRNs. The mobility of cognitive users (CUs) and the working activities of primary users (PUs) are analyzed in theory. And a joint feature vector extraction (JFVE) method is proposed based on the theoretical analysis. Then spectrum mobility prediction is executed through the classification of SVM with a fast convergence speed. Numerical results validate that SVM-SMP gains better short-time prediction accuracy rate and miss prediction rate performance than the two algorithms just depending on the location and speed information. Additionally, a rational parameter design can remedy the prediction performance degradation caused by high speed SUs with strong randomness movements. Yao Wang, Zhongzhao Zhang, Lin Ma, and Jiamei Chen Copyright © 2014 Yao Wang et al. All rights reserved. Trusted Measurement Model Based on Multitenant Behaviors Sun, 30 Mar 2014 10:05:09 +0000 http://www.hindawi.com/journals/tswj/2014/384967/ With a fast growing pervasive computing, especially cloud computing, the behaviour measurement is at the core and plays a vital role. A new behaviour measurement tailored for Multitenants in cloud computing is needed urgently to fundamentally establish trust relationship. Based on our previous research, we propose an improved trust relationship scheme which captures the world of cloud computing where multitenants share the same physical computing platform. Here, we first present the related work on multitenant behaviour; secondly, we give the scheme of behaviour measurement where decoupling of multitenants is taken into account; thirdly, we explicitly explain our decoupling algorithm for multitenants; fourthly, we introduce a new way of similarity calculation for deviation control, which fits the coupled multitenants under study well; lastly, we design the experiments to test our scheme. Zhen-Hu Ning, Chang-Xiang Shen, Yong Zhao, and Peng Liang Copyright © 2014 Zhen-Hu Ning et al. All rights reserved. Secure and Fair Cluster Head Selection Protocol for Enhancing Security in Mobile Ad Hoc Networks Thu, 27 Mar 2014 09:49:36 +0000 http://www.hindawi.com/journals/tswj/2014/608984/ Mobile ad hoc networks (MANETs) are wireless networks consisting of number of autonomous mobile devices temporarily interconnected into a network by wireless media. MANETs become one of the most prevalent areas of research in the recent years. Resource limitations, energy efficiency, scalability, and security are the great challenging issues in MANETs. Due to its deployment nature, MANETs are more vulnerable to malicious attack. The secure routing protocols perform very basic security related functions which are not sufficient to protect the network. In this paper, a secure and fair cluster head selection protocol (SFCP) is proposed which integrates security factors into the clustering approach for achieving attacker identification and classification. Byzantine agreement based cooperative technique is used for attacker identification and classification to make the network more attack resistant. SFCP used to solve this issue by making the nodes that are totally surrounded by malicious neighbors adjust dynamically their belief and disbelief thresholds. The proposed protocol selects the secure and energy efficient cluster head which acts as a local detector without imposing overhead to the clustering performance. SFCP is simulated in network simulator 2 and compared with two protocols including AODV and CBRP. B. Paramasivan and M. Kaliappan Copyright © 2014 B. Paramasivan and M. Kaliappan. All rights reserved. Robust Filtering for a Class of Complex Networks with Stochastic Packet Dropouts and Time Delays Thu, 27 Mar 2014 08:27:36 +0000 http://www.hindawi.com/journals/tswj/2014/560234/ The robust filtering problem is investigated for a class of complex network systems which has stochastic packet dropouts and time delays, combined with disturbance inputs. The packet dropout phenomenon occurs in a random way and the occurrence probability for each measurement output node is governed by an individual random variable. Besides, the time delay phenomenon is assumed to occur in a nonlinear vector-valued function. We aim to design a filter such that the estimation error converges to zero exponentially in the mean square, while the disturbance rejection attenuation is constrained to a given level by means of the performance index. By constructing the proper Lyapunov-Krasovskii functional, we acquire sufficient conditions to guarantee the stability of the state detection observer for the discrete systems, and the observer gain is also derived by solving linear matrix inequalities. Finally, an illustrative example is provided to show the usefulness and effectiveness of the proposed design method. Jie Zhang, Ming Lyu, Hamid Reza Karimi, Pengfei Guo, and Yuming Bo Copyright © 2014 Jie Zhang et al. All rights reserved. On the Improvement of Wiener Attack on RSA with Small Private Exponent Thu, 27 Mar 2014 07:43:29 +0000 http://www.hindawi.com/journals/tswj/2014/650537/ RSA system is based on the hardness of the integer factorization problem (IFP). Given an RSA modulus , it is difficult to determine the prime factors and efficiently. One of the most famous short exponent attacks on RSA is the Wiener attack. In 1997, Verheul and van Tilborg use an exhaustive search to extend the boundary of the Wiener attack. Their result shows that the cost of exhaustive search is bits when extending the Weiner's boundary r bits. In this paper, we first reduce the cost of exhaustive search from bits to bits. Then, we propose a method named EPF. With EPF, the cost of exhaustive search is further reduced to bits when we extend Weiner's boundary bits. It means that our result is 214 times faster than Verheul and van Tilborg's result. Besides, the security boundary is extended 7 bits. Mu-En Wu, Chien-Ming Chen, Yue-Hsun Lin, and Hung-Min Sun Copyright © 2014 Mu-En Wu et al. All rights reserved. Transition Characteristic Analysis of Traffic Evolution Process for Urban Traffic Network Thu, 27 Mar 2014 07:20:26 +0000 http://www.hindawi.com/journals/tswj/2014/603274/ The characterization of the dynamics of traffic states remains fundamental to seeking for the solutions of diverse traffic problems. To gain more insights into traffic dynamics in the temporal domain, this paper explored temporal characteristics and distinct regularity in the traffic evolution process of urban traffic network. We defined traffic state pattern through clustering multidimensional traffic time series using self-organizing maps and construct a pattern transition network model that is appropriate for representing and analyzing the evolution progress. The methodology is illustrated by an application to data flow rate of multiple road sections from Network of Shenzhen’s Nanshan District, China. Analysis and numerical results demonstrated that the methodology permits extracting many useful traffic transition characteristics including stability, preference, activity, and attractiveness. In addition, more information about the relationships between these characteristics was extracted, which should be helpful in understanding the complex behavior of the temporal evolution features of traffic patterns. Longfei Wang, Hong Chen, and Yang Li Copyright © 2014 Longfei Wang et al. All rights reserved. Novel Image Encryption Scheme Based on Chebyshev Polynomial and Duffing Map Wed, 26 Mar 2014 08:54:39 +0000 http://www.hindawi.com/journals/tswj/2014/283639/ We present a novel image encryption algorithm using Chebyshev polynomial based on permutation and substitution and Duffing map based on substitution. Comprehensive security analysis has been performed on the designed scheme using key space analysis, visual testing, histogram analysis, information entropy calculation, correlation coefficient analysis, differential analysis, key sensitivity test, and speed test. The study demonstrates that the proposed image encryption algorithm shows advantages of more than key space and desirable level of security based on the good statistical results and theoretical arguments. Borislav Stoyanov and Krasimir Kordov Copyright © 2014 Borislav Stoyanov and Krasimir Kordov. All rights reserved. Privacy-Preserving Location-Based Query Using Location Indexes and Parallel Searching in Distributed Networks Tue, 25 Mar 2014 08:59:12 +0000 http://www.hindawi.com/journals/tswj/2014/751845/ An efficient location-based query algorithm of protecting the privacy of the user in the distributed networks is given. This algorithm utilizes the location indexes of the users and multiple parallel threads to search and select quickly all the candidate anonymous sets with more users and their location information with more uniform distribution to accelerate the execution of the temporal-spatial anonymous operations, and it allows the users to configure their custom-made privacy-preserving location query requests. The simulated experiment results show that the proposed algorithm can offer simultaneously the location query services for more users and improve the performance of the anonymous server and satisfy the anonymous location requests of the users. Cheng Zhong, Lei Liu, and Jing Zhao Copyright © 2014 Cheng Zhong et al. All rights reserved. Assessment on Knowledge Network Sharing Capability of Industrial Cluster Based on Dempster-Shafer Theory of Evidence Mon, 24 Mar 2014 06:42:21 +0000 http://www.hindawi.com/journals/tswj/2014/810782/ Based on Theory of Evidence and reviewing research papers concerned, a concept model of knowledge sharing network among industrial cluster firms, which can be applied to assess knowledge sharing capacity, has been built. Next, the authors create a set of assessment index systems including twelve subindexes under four principle indexes. In this study, ten experts in the same field were invited to score all the indexes of knowledge sharing capacity concerning one certain industrial cluster. The research result shows relatively high knowledge network sharing capacity among the certain industrial cluster firms. Another conclusion is that the assessment method with Theory of Evidence is feasible to conduct such a research. Shengli Dai and Hailin Zhang Copyright © 2014 Shengli Dai and Hailin Zhang. All rights reserved. Modeling of Information Diffusion in Twitter-Like Social Networks under Information Overload Sun, 23 Mar 2014 13:20:50 +0000 http://www.hindawi.com/journals/tswj/2014/914907/ Due to the existence of information overload in social networks, it becomes increasingly difficult for users to find useful information according to their interests. This paper takes Twitter-like social networks into account and proposes models to characterize the process of information diffusion under information overload. Users are classified into different types according to their in-degrees and out-degrees, and user behaviors are generalized into two categories: generating and forwarding. View scope is introduced to model the user information-processing capability under information overload, and the average number of times a message appears in view scopes after it is generated by a given type user is adopted to characterize the information diffusion efficiency, which is calculated theoretically. To verify the accuracy of theoretical analysis results, we conduct simulations and provide the simulation results, which are consistent with the theoretical analysis results perfectly. These results are of importance to understand the diffusion dynamics in social networks, and this analysis framework can be extended to consider more realistic situations. Pei Li, Wei Li, Hui Wang, and Xin Zhang Copyright © 2014 Pei Li et al. All rights reserved. Dynamic Resource Allocation in Hybrid Access Femtocell Network Thu, 20 Mar 2014 07:07:11 +0000 http://www.hindawi.com/journals/tswj/2014/539720/ Intercell interference is one of the most challenging issues in femtocell deployment under the coverage of existing macrocell. Allocation of resources between femtocell and macrocell is essential to counter the effects of interference in dense femtocell networks. Advances in resource management strategies have improved the control mechanism for interference reduction at lower node density, but most of them are ineffective at higher node density. In this paper, a dynamic resource allocation management algorithm (DRAMA) for spectrum shared hybrid access OFDMA femtocell network is proposed. To reduce the macro-femto-tier interference and to improve the quality of service, the proposed algorithm features a dynamic resource allocation scheme by controlling them both centrally and locally. The proposed scheme focuses on Femtocell Access Point (FAP) owners’ satisfaction and allows maximum utilization of available resources based on congestion in the network. A simulation environment is developed to study the quantitative performance of DRAMA in hybrid access-control femtocell network and compare it to closed and open access mechanisms. The performance analysis shows that higher number of random users gets connected to the FAP without compromising FAP owners’ satisfaction allowing the macrocell to offload a large number of users in a dense heterogeneous network. Afaz Uddin Ahmed, Mohammad Tariqul Islam, Mahamod Ismail, and Mohammad Ghanbarisabagh Copyright © 2014 Afaz Uddin Ahmed et al. All rights reserved. An Improved Proportionate Normalized Least-Mean-Square Algorithm for Broadband Multipath Channel Estimation Thu, 20 Mar 2014 06:35:46 +0000 http://www.hindawi.com/journals/tswj/2014/572969/ To make use of the sparsity property of broadband multipath wireless communication channels, we mathematically propose an -norm-constrained proportionate normalized least-mean-square (LP-PNLMS) sparse channel estimation algorithm. A general -norm is weighted by the gain matrix and is incorporated into the cost function of the proportionate normalized least-mean-square (PNLMS) algorithm. This integration is equivalent to adding a zero attractor to the iterations, by which the convergence speed and steady-state performance of the inactive taps are significantly improved. Our simulation results demonstrate that the proposed algorithm can effectively improve the estimation performance of the PNLMS-based algorithm for sparse channel estimation applications. Yingsong Li and Masanori Hamamura Copyright © 2014 Yingsong Li and Masanori Hamamura. All rights reserved. Analyses of Crime Patterns in NIBRS Data Based on a Novel Graph Theory Clustering Method: Virginia as a Case Study Thu, 20 Mar 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/492461/ This paper suggests a novel clustering method for analyzing the National Incident-Based Reporting System (NIBRS) data, which include the determination of correlation of different crime types, the development of a likelihood index for crimes to occur in a jurisdiction, and the clustering of jurisdictions based on crime type. The method was tested by using the 2005 assault data from 121 jurisdictions in Virginia as a test case. The analyses of these data show that some different crime types are correlated and some different crime parameters are correlated with different crime types. The analyses also show that certain jurisdictions within Virginia share certain crime patterns. This information assists with constructing a pattern for a specific crime type and can be used to determine whether a jurisdiction may be more likely to see this type of crime occur in their area. Peixin Zhao, Marjorie Darrah, Jim Nolan, and Cun-Quan Zhang Copyright © 2014 Peixin Zhao et al. All rights reserved. Optical Frequency Upconversion Technique for Transmission of Wireless MIMO-Type Signals over Optical Fiber Sun, 16 Mar 2014 17:09:31 +0000 http://www.hindawi.com/journals/tswj/2014/170471/ The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF) technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO) signals feeding multiple antennas in the fiber wireless (FiWi) system. A novel optical frequency upconversion (OFU) technique is proposed to solve this problem. In this paper, the novel OFU approach is used to transmit three wireless MIMO signals over a 20 km standard single mode fiber (SMF). The OFU technique exploits one optical source to produce multiple wavelengths by delivering it to a LiNbO3 external optical modulator. The wireless MIMO signals are then modulated by LiNbO3 optical intensity modulators separately using the generated optical carriers from the OFU process. These modulators use the optical single-sideband with carrier (OSSB+C) modulation scheme to optimize the system performance against the fiber dispersion effect. Each wireless MIMO signal is with a 2.4 GHz or 5 GHz carrier frequency, 1 Gb/s data rate, and 16-quadrature amplitude modulation (QAM). The crosstalk between the wireless MIMO signals is highly suppressed, since each wireless MIMO signal is carried on a specific optical wavelength. R. Q. Shaddad, A. B. Mohammad, S. A. Al-Gailani, and A. M. Al-Hetar Copyright © 2014 R. Q. Shaddad et al. All rights reserved. Multidimensional Optimization of Signal Space Distance Parameters in WLAN Positioning Sun, 16 Mar 2014 11:24:42 +0000 http://www.hindawi.com/journals/tswj/2014/986061/ Accurate indoor localization of mobile users is one of the challenging problems of the last decade. Besides delivering high speed Internet, Wireless Local Area Network (WLAN) can be used as an effective indoor positioning system, being competitive both in terms of accuracy and cost. Among the localization algorithms, nearest neighbor fingerprinting algorithms based on Received Signal Strength (RSS) parameter have been extensively studied as an inexpensive solution for delivering indoor Location Based Services (LBS). In this paper, we propose the optimization of the signal space distance parameters in order to improve precision of WLAN indoor positioning, based on nearest neighbor fingerprinting algorithms. Experiments in a real WLAN environment indicate that proposed optimization leads to substantial improvements of the localization accuracy. Our approach is conceptually simple, is easy to implement, and does not require any additional hardware. Milenko Brković and Mirjana Simić Copyright © 2014 Milenko Brković and Mirjana Simić. All rights reserved. Channel Estimation in DCT-Based OFDM Thu, 13 Mar 2014 09:11:32 +0000 http://www.hindawi.com/journals/tswj/2014/813429/ This paper derives the channel estimation of a discrete cosine transform- (DCT-) based orthogonal frequency-division multiplexing (OFDM) system over a frequency-selective multipath fading channel. Channel estimation has been proved to improve system throughput and performance by allowing for coherent demodulation. Pilot-aided methods are traditionally used to learn the channel response. Least square (LS) and mean square error estimators (MMSE) are investigated. We also study a compressed sensing (CS) based channel estimation, which takes the sparse property of wireless channel into account. Simulation results have shown that the CS based channel estimation is expected to have better performance than LS. However MMSE can achieve optimal performance because of prior knowledge of the channel statistic. Yulin Wang, Gengxin Zhang, Zhidong Xie, and Jing Hu Copyright © 2014 Yulin Wang et al. All rights reserved. A Fast Overlapping Community Detection Algorithm with Self-Correcting Ability Thu, 13 Mar 2014 08:18:45 +0000 http://www.hindawi.com/journals/tswj/2014/738206/ Due to the defects of all kinds of modularity, this paper defines a weighted modularity based on the density and cohesion as the new evaluation measurement. Since the proportion of the overlapping nodes in network is very low, the number of the nodes’ repeat visits can be reduced by signing the vertices with the overlapping attributes. In this paper, we propose three test conditions for overlapping nodes and present a fast overlapping community detection algorithm with self-correcting ability, which is decomposed into two processes. Under the control of overlapping properties, the complexity of the algorithm tends to be approximate linear. And we also give a new understanding on membership vector. Moreover, we improve the bridgeness function which evaluates the extent of overlapping nodes. Finally, we conduct the experiments on three networks with well known community structures and the results verify the feasibility and effectiveness of our algorithm. Laizhong Cui, Lei Qin, and Nan Lu Copyright © 2014 Laizhong Cui et al. All rights reserved. WDM Network and Multicasting Protocol Strategies Wed, 12 Mar 2014 11:28:27 +0000 http://www.hindawi.com/journals/tswj/2014/581052/ Optical technology gains extensive attention and ever increasing improvement because of the huge amount of network traffic caused by the growing number of internet users and their rising demands. However, with wavelength division multiplexing (WDM), it is easier to take the advantage of optical networks and optical burst switching (OBS) and to construct WDM networks with low delay rates and better data transparency these technologies are the best choices. Furthermore, multicasting in WDM is an urgent solution for bandwidth-intensive applications. In the paper, a new multicasting protocol with OBS is proposed. The protocol depends on a leaf initiated structure. The network is composed of source, ingress switches, intermediate switches, edge switches, and client nodes. The performance of the protocol is examined with Just Enough Time (JET) and Just In Time (JIT) reservation protocols. Also, the paper involves most of the recent advances about WDM multicasting in optical networks. WDM multicasting in optical networks is given as three common subtitles: Broadcast and-select networks, wavelength-routed networks, and OBS networks. Also, in the paper, multicast routing protocols are briefly summarized and optical burst switched WDM networks are investigated with the proposed multicast schemes. Pinar Kirci and Abdul Halim Zaim Copyright © 2014 Pinar Kirci and Abdul Halim Zaim. All rights reserved. Motion Adaptive Vertical Handoff in Cellular/WLAN Heterogeneous Wireless Network Tue, 11 Mar 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/341038/ In heterogeneous wireless network, vertical handoff plays an important role for guaranteeing quality of service and overall performance of network. Conventional vertical handoff trigger schemes are mostly developed from horizontal handoff in homogeneous cellular network. Basically, they can be summarized as hysteresis-based and dwelling-timer-based algorithms, which are reliable on avoiding unnecessary handoff caused by the terminals dwelling at the edge of WLAN coverage. However, the coverage of WLAN is much smaller compared with cellular network, while the motion types of terminals can be various in a typical outdoor scenario. As a result, traditional algorithms are less effective in avoiding unnecessary handoff triggered by vehicle-borne terminals with various speeds. Besides that, hysteresis and dwelling-timer thresholds usually need to be modified to satisfy different channel environments. For solving this problem, a vertical handoff algorithm based on Q-learning is proposed in this paper. Q-learning can provide the decider with self-adaptive ability for handling the terminals’ handoff requests with different motion types and channel conditions. Meanwhile, Neural Fuzzy Inference System (NFIS) is embedded to retain a continuous perception of the state space. Simulation results verify that the proposed algorithm can achieve lower unnecessary handoff probability compared with the other two conventional algorithms. Limin Li, Lin Ma, Yubin Xu, and Yunhai Fu Copyright © 2014 Limin Li et al. All rights reserved. MWAHCA: A Multimedia Wireless Ad Hoc Cluster Architecture Tue, 11 Mar 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/913046/ Wireless Ad hoc networks provide a flexible and adaptable infrastructure to transport data over a great variety of environments. Recently, real-time audio and video data transmission has been increased due to the appearance of many multimedia applications. One of the major challenges is to ensure the quality of multimedia streams when they have passed through a wireless ad hoc network. It requires adapting the network architecture to the multimedia QoS requirements. In this paper we propose a new architecture to organize and manage cluster-based ad hoc networks in order to provide multimedia streams. Proposed architecture adapts the network wireless topology in order to improve the quality of audio and video transmissions. In order to achieve this goal, the architecture uses some information such as each node’s capacity and the QoS parameters (bandwidth, delay, jitter, and packet loss). The architecture splits the network into clusters which are specialized in specific multimedia traffic. The real system performance study provided at the end of the paper will demonstrate the feasibility of the proposal. Juan R. Diaz, Jaime Lloret, Jose M. Jimenez, and Sandra Sendra Copyright © 2014 Juan R. Diaz et al. All rights reserved. A Novel Complex Networks Clustering Algorithm Based on the Core Influence of Nodes Mon, 10 Mar 2014 09:05:44 +0000 http://www.hindawi.com/journals/tswj/2014/801854/ In complex networks, cluster structure, identified by the heterogeneity of nodes, has become a common and important topological property. Network clustering methods are thus significant for the study of complex networks. Currently, many typical clustering algorithms have some weakness like inaccuracy and slow convergence. In this paper, we propose a clustering algorithm by calculating the core influence of nodes. The clustering process is a simulation of the process of cluster formation in sociology. The algorithm detects the nodes with core influence through their betweenness centrality, and builds the cluster’s core structure by discriminant functions. Next, the algorithm gets the final cluster structure after clustering the rest of the nodes in the network by optimizing method. Experiments on different datasets show that the clustering accuracy of this algorithm is superior to the classical clustering algorithm (Fast-Newman algorithm). It clusters faster and plays a positive role in revealing the real cluster structure of complex networks precisely. Chao Tong, Jianwei Niu, Bin Dai, and Zhongyu Xie Copyright © 2014 Chao Tong et al. All rights reserved. Modeling and Performance Analysis of an Improved Movement-Based Location Management Scheme for Packet-Switched Mobile Communication Systems Sun, 09 Mar 2014 15:28:36 +0000 http://www.hindawi.com/journals/tswj/2014/812657/ One of the key technologies to support mobility of mobile station (MS) in mobile communication systems is location management which consists of location update and paging. In this paper, an improved movement-based location management scheme with two movement thresholds is proposed, considering bursty data traffic characteristics of packet-switched (PS) services. The analytical modeling for location update and paging signaling loads of the proposed scheme is developed thoroughly and the performance of the proposed scheme is compared with that of the conventional scheme. We show that the proposed scheme outperforms the conventional scheme in terms of total signaling load with an appropriate selection of movement thresholds. Yun Won Chung, Jae Kyun Kwon, and Suwon Park Copyright © 2014 Yun Won Chung et al. All rights reserved. A Lightweight Neighbor-Info-Based Routing Protocol for No-Base-Station Taxi-Call System Sun, 09 Mar 2014 09:59:42 +0000 http://www.hindawi.com/journals/tswj/2014/601913/ Since the quick topology change and short connection duration, the VANET has had unstable routing and wireless signal quality. This paper proposes a kind of lightweight routing protocol-LNIB for call system without base station, which is applicable to the urban taxis. LNIB maintains and predicts neighbor information dynamically, thus finding the reliable path between the source and the target. This paper describes the protocol in detail and evaluates the performance of this protocol by simulating under different nodes density and speed. The result of evaluation shows that the performance of LNIB is better than AODV which is a classic protocol in taxi-call scene. Xudong Zhu, Jinhang Wang, and Yunchao Chen Copyright © 2014 Xudong Zhu et al. All rights reserved. Performance Analysis of Relay Subset Selection for Amplify-and-Forward Cognitive Relay Networks Thu, 06 Mar 2014 13:54:46 +0000 http://www.hindawi.com/journals/tswj/2014/548082/ Cooperative communication is regarded as a key technology in wireless networks, including cognitive radio networks (CRNs), which increases the diversity order of the signal to combat the unfavorable effects of the fading channels, by allowing distributed terminals to collaborate through sophisticated signal processing. Underlay CRNs have strict interference constraints towards the secondary users (SUs) active in the frequency band of the primary users (PUs), which limits their transmit power and their coverage area. Relay selection offers a potential solution to the challenges faced by underlay networks, by selecting either single best relay or a subset of potential relay set under different design requirements and assumptions. The best relay selection schemes proposed in the literature for amplify-and-forward (AF) based underlay cognitive relay networks have been very well studied in terms of outage probability (OP) and bit error rate (BER), which is deficient in multiple relay selection schemes. The novelty of this work is to study the outage behavior of multiple relay selection in the underlay CRN and derive the closed-form expressions for the OP and BER through cumulative distribution function (CDF) of the SNR received at the destination. The effectiveness of relay subset selection is shown through simulation results. Kiran Sultan, Ijaz Mansoor Qureshi, Aqdas Naveed Malik, and Muhammad Zubair Copyright © 2014 Kiran Sultan et al. All rights reserved. Energy-Efficient Routing Control Algorithm in Large-Scale WSN for Water Environment Monitoring with Application to Three Gorges Reservoir Area Wed, 05 Mar 2014 16:44:43 +0000 http://www.hindawi.com/journals/tswj/2014/802915/ The typical application backgrounds of large-scale WSN (wireless sensor networks) for the water environment monitoring in the Three Gorges Reservoir are large coverage area and wide distribution. To maximally prolong lifetime of large-scale WSN, a new energy-saving routing algorithm has been proposed, using the method of maximum energy-welfare optimization clustering. Firstly, temporary clusters are formed based on two main parameters, the remaining energy of nodes and the distance between a node and the base station. Secondly, the algorithm adjusts cluster heads and optimizes the clustering according to the maximum energy-welfare of the cluster by the cluster head shifting mechanism. Finally, in order to save node energy efficiently, cluster heads transmit data to the base station in single-hop and multihop way. Theoretical analysis and simulation results show that the proposed algorithm is feasible and advanced. It can efficiently save the node energy, balance the energy dissipation of all nodes, and prolong the network lifetime. Yuanchang Zhong, Lin Cheng, Liang Zhang, Yongduan Song, and Hamid Reza Karimi Copyright © 2014 Yuanchang Zhong et al. All rights reserved. Cooperative Search and Rescue with Artificial Fishes Based on Fish-Swarm Algorithm for Underwater Wireless Sensor Networks Wed, 05 Mar 2014 06:35:22 +0000 http://www.hindawi.com/journals/tswj/2014/145306/ This paper presents a searching control approach for cooperating mobile sensor networks. We use a density function to represent the frequency of distress signals issued by victims. The mobile nodes’ moving in mission space is similar to the behaviors of fish-swarm in water. So, we take the mobile node as artificial fish node and define its operations by a probabilistic model over a limited range. A fish-swarm based algorithm is designed requiring local information at each fish node and maximizing the joint detection probabilities of distress signals. Optimization of formation is also considered for the searching control approach and is optimized by fish-swarm algorithm. Simulation results include two schemes: preset route and random walks, and it is showed that the control scheme has adaptive and effective properties. Wei Zhao, Zhenmin Tang, Yuwang Yang, Lei Wang, and Shaohua Lan Copyright © 2014 Wei Zhao et al. All rights reserved. Bandwidth Enhancement of a Dual Band Planar Monopole Antenna Using Meandered Microstrip Feeding Mon, 03 Mar 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/856504/ A meandered-microstrip fed circular shaped monopole antenna loaded with vertical slots on a high dielectric material substrate is proposed in this paper. The performance criteria of the proposed antenna have been experimentally verified by fabricating a printed prototype. The experimental results show that the proposed antenna has achieved wider bandwidth with satisfactory gain by introducing meandered-microstrip feeding in assistant of partial ground plane. It is observed that, the −10 dB impedance bandwidth of the proposed antenna at lower band is 44.4% (600 MHz–1 GHz) and at upper band is 28% (2.25 GHz–2.95 GHz). The measured maximum gains of −1.18 dBi and 4.87 dBi with maximum radiation efficiencies have been observed at lower band and upper band, respectively. The antenna configuration and parametric study have been carried out with the help of commercially available computer-aided EM simulator, and a good accordance is perceived in between the simulated and measured results. The analysis of performance criteria and almost consistent radiation pattern make the proposed antenna a suitable candidate for UHF RFID, WiMAX, and WLAN applications. M. R. Ahsan, M. T. Islam, M. Habib Ullah, and N. Misran Copyright © 2014 M. R. Ahsan et al. All rights reserved. Design of a Compact Tuning Fork-Shaped Notched Ultrawideband Antenna for Wireless Communication Application Sun, 02 Mar 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/874241/ A new compact planar notched ultrawideband (UWB) antenna is designed for wireless communication application. The proposed antenna has a compact size of where is the wavelength of the lowest operating frequency. The antenna is comprised of rectangular radiating patch, ground plane, and an arc-shaped strip in between radiating patch and feed line. By introducing a new Tuning Fork-shaped notch in the radiating plane, a stopband is obtained. The antenna is tested and measured. The measured result indicated that fabricated antenna has achieved a wide bandwidth of 4.33–13.8 GHz (at −10 dB return loss) with a rejection frequency band of 5.28–6.97 GHz (WiMAX, WLAN, and C-band). The effects of the parameters of the antenna are discussed. The experiment results demonstrate that the proposed antenna can well meet the requirement for the UWB communication in spite of its compactness and small size. M. N. Shakib, M. Moghavvemi, and W. N. L. Mahadi Copyright © 2014 M. N. Shakib et al. All rights reserved. Protocol Independent Adaptive Route Update for VANET Thu, 27 Feb 2014 16:17:19 +0000 http://www.hindawi.com/journals/tswj/2014/403918/ High relative node velocity and high active node density have presented challenges to existing routing approaches within highly scaled ad hoc wireless networks, such as Vehicular Ad hoc Networks (VANET). Efficient routing requires finding optimum route with minimum delay, updating it on availability of a better one, and repairing it on link breakages. Current routing protocols are generally focused on finding and maintaining an efficient route, with very less emphasis on route update. Adaptive route update usually becomes impractical for dense networks due to large routing overheads. This paper presents an adaptive route update approach which can provide solution for any baseline routing protocol. The proposed adaptation eliminates the classification of reactive and proactive by categorizing them as logical conditions to find and update the route. Asim Rasheed, Sana Ajmal, and Amir Qayyum Copyright © 2014 Asim Rasheed et al. All rights reserved. Secure Wireless Communications via Cooperative Transmitting Sun, 23 Feb 2014 13:59:13 +0000 http://www.hindawi.com/journals/tswj/2014/760175/ Information-theoretic secrecy is combined with cryptographic secrecy to create a secret-key exchange protocol for wireless networks. A network of transmitters, which already have cryptographically secured channels between them, cooperate to exchange a secret key with a new receiver at a random location, in the presence of passive eavesdroppers at unknown locations. Two spatial point processes, homogeneous Poisson process and independent uniformly distributed points, are used for the spatial distributions of transmitters and eavesdroppers. We analyse the impact of the number of cooperating transmitters and the number of eavesdroppers on the area fraction where secure communication is possible. Upper bounds on the probability of existence of positive secrecy between the cooperating transmitters and the receiver are derived. The closeness of the upper bounds to the real value is then estimated by means of numerical simulations. Simulations also indicate that a deterministic spatial distribution for the transmitters, for example, hexagonal and square lattices, increases the probability of existence of positive secrecy capacity compared to the random spatial distributions. For the same number of friendly nodes, cooperative transmitting provides a dramatically larger secrecy region than cooperative jamming and cooperative relaying. Toni Draganov Stojanovski and Ninoslav Marina Copyright © 2014 Toni Draganov Stojanovski and Ninoslav Marina. All rights reserved. Channel Selection Based on Trust and Multiarmed Bandit in Multiuser, Multichannel Cognitive Radio Networks Sun, 23 Feb 2014 12:08:12 +0000 http://www.hindawi.com/journals/tswj/2014/916156/ This paper proposes a channel selection scheme for the multiuser, multichannel cognitive radio networks. This scheme formulates the channel selection as the multiarmed bandit problem, where cognitive radio users are compared to the players and channels to the arms. By simulation negotiation we can achieve the potential reward on each channel after it is selected for transmission; then the channel with the maximum accumulated rewards is formally chosen. To further improve the performance, the trust model is proposed and combined with multi-armed bandit to address the channel selection problem. Simulation results validate the proposed scheme. Fanzi Zeng and Xinwang Shen Copyright © 2014 Fanzi Zeng and Xinwang Shen. All rights reserved. Hybrid Single-Packet IP Traceback with Low Storage and High Accuracy Sun, 23 Feb 2014 10:02:35 +0000 http://www.hindawi.com/journals/tswj/2014/239280/ Traceback schemes have been proposed to trace the sources of attacks that usually hide by spoofing their IP addresses. Among these methods, schemes using packet logging can achieve single-packet traceback. But packet logging demands high storage on routers and therefore makes IP traceback impractical. For lower storage requirement, packet logging and packet marking are fused to make hybrid single-packet IP traceback. Despite such attempts, their storage still increases with packet numbers. That is why RIHT bounds its storage with path numbers to guarantee low storage. RIHT uses IP header’s ID and offset fields to mark packets, so it inevitably suffers from fragment and drop issues for its packet reassembly. Although the 16-bit hybrid IP traceback schemes, for example, MORE, can mitigate the fragment problem, their storage requirement grows up with packet numbers. To solve the storage and fragment problems in one shot, we propose a single-packet IP traceback scheme that only uses packets’ ID field for marking. Our major contributions are as follows: (1) our fragmented packets with tracing marks can be reassembled; (2) our storage is not affected by packet numbers; (3) it is the first hybrid single-packet IP traceback scheme to achieve zero false positive and zero false negative rates. Ming Hour Yang Copyright © 2014 Ming Hour Yang. All rights reserved. Design and Implementation of Low Profile Antenna for Dual-Band Applications Using Rotated E-Shaped Conductor-Backed Plane Sun, 23 Feb 2014 09:04:40 +0000 http://www.hindawi.com/journals/tswj/2014/632403/ A novel configuration of a printed monopole antenna with a very compact size for satisfying WLAN operations at the 5.2/5.8 GHz and also for X-band operations at the 10 GHz has been proposed. The antenna includes a simple square-shaped patch as the radiator, the rotated U-shaped conductor back plane element with embedded strip on it, and the partial rectangular ground surface. By using the rotated U-shaped conductor-backed plane with proper values, good impedance matching and improvement in bandwidth can be achieved, at the lower and upper bands. The impedance bandwidth for  dB is about 1.15 GHz for 5 GHz band and 5.3 GHz for X-band. The measured peak gains are about 1.9 dBi at WLAN-band and 4.2 dBi at X-band. The experimental results represent that the realized antenna with good omnidirectional radiation characteristics, enough impedance bandwidth, and reasonable gains can be appropriate for various applications of the future developed technologies and handheld devices. Mahdi Jalali, Tohid Sedghi, and Shahin Shafei Copyright © 2014 Mahdi Jalali et al. All rights reserved. A New Cooperative MIMO Scheme Based on SM for Energy-Efficiency Improvement in Wireless Sensor Network Thu, 20 Feb 2014 12:54:30 +0000 http://www.hindawi.com/journals/tswj/2014/975054/ Improving the energy efficiency in wireless sensor networks (WSN) has attracted considerable attention nowadays. The multiple-input multiple-output (MIMO) technique has been proved as a good candidate for improving the energy efficiency, but it may not be feasible in WSN which is due to the size limitation of the sensor node. As a solution, the cooperative multiple-input multiple-output (CMIMO) technique overcomes this constraint and shows a dramatically good performance. In this paper, a new CMIMO scheme based on the spatial modulation (SM) technique named CMIMO-SM is proposed for energy-efficiency improvement. We first establish the system model of CMIMO-SM. Based on this model, the transmission approach is introduced graphically. In order to evaluate the performance of the proposed scheme, a detailed analysis in terms of energy consumption per bit of the proposed scheme compared with the conventional CMIMO is presented. Later, under the guide of this new scheme we extend our proposed CMIMO-SM to a multihop clustered WSN for further achieving energy efficiency by finding an optimal hop-length. Equidistant hop as the traditional scheme will be compared in this paper. Results from the simulations and numerical experiments indicate that by the use of the proposed scheme, significant savings in terms of total energy consumption can be achieved. Combining the proposed scheme with monitoring sensor node will provide a good performance in arbitrary deployed WSN such as forest fire detection system. Yuyang Peng and Jaeho Choi Copyright © 2014 Yuyang Peng and Jaeho Choi. All rights reserved. Video Traffic Characteristics of Modern Encoding Standards: H.264/AVC with SVC and MVC Extensions and H.265/HEVC Thu, 20 Feb 2014 12:08:16 +0000 http://www.hindawi.com/journals/tswj/2014/189481/ Video encoding for multimedia services over communication networks has significantly advanced in recent years with the development of the highly efficient and flexible H.264/AVC video coding standard and its SVC extension. The emerging H.265/HEVC video coding standard as well as 3D video coding further advance video coding for multimedia communications. This paper first gives an overview of these new video coding standards and then examines their implications for multimedia communications by studying the traffic characteristics of long videos encoded with the new coding standards. We review video coding advances from MPEG-2 and MPEG-4 Part 2 to H.264/AVC and its SVC and MVC extensions as well as H.265/HEVC. For single-layer (nonscalable) video, we compare H.265/HEVC and H.264/AVC in terms of video traffic and statistical multiplexing characteristics. Our study is the first to examine the H.265/HEVC traffic variability for long videos. We also illustrate the video traffic characteristics and statistical multiplexing of scalable video encoded with the SVC extension of H.264/AVC as well as 3D video encoded with the MVC extension of H.264/AVC. Patrick Seeling and Martin Reisslein Copyright © 2014 Patrick Seeling and Martin Reisslein. All rights reserved. Uplink Scheduling and Adjacent-Channel Coupling Loss Analysis for TD-LTE Deployment Thu, 20 Feb 2014 09:09:49 +0000 http://www.hindawi.com/journals/tswj/2014/685102/ TD-LTE, one of the two duplexing modes in LTE, operates in unpaired spectrum and has the advantages of TDD-based technologies. It is expected that TD-LTE will be more rapidly deployed in near future and most of WiMax operators will upgrade their networks to TD-LTE gradually. Before completely upgrading to TD-LTE, WiMax may coexist with TD-LTE in an adjacent frequency band. In addition, multiple TD-LTE operators may deploy their networks in adjacent bands. When more than one TDD network operates in adjacent frequency bands, severe interference may happen due to adjacent channel interference (ACI) and unsynchronized operations. In this paper, coexistence issues between TD-LTE and other systems are analyzed and coexistence requirements are provided. This paper has three research objectives. First, frame synchronization between TD-LTE and WiMax is discussed by investigating possible combinations of TD-LTE and WiMax configurations. Second, an uplink scheduling algorithm is proposed to utilize a leakage pattern of ACI in synchronized operations. Third, minimum requirements for coexistence in unsynchronized operations are analyzed by introducing a concept of adjacent-channel coupling loss. From the analysis and simulation results, we can see that coexistence of TD-LTE with other TDD systems is feasible if the two networks are synchronized. For the unsynchronized case, some special cell-site engineering techniques may be required to reduce the ACI. Woon-Young Yeo, Sung Ho Moon, and Jae-Hoon Kim Copyright © 2014 Woon-Young Yeo et al. All rights reserved. Synthesis of Volumetric Ring Antenna Array for Terrestrial Coverage Pattern Tue, 18 Feb 2014 11:37:14 +0000 http://www.hindawi.com/journals/tswj/2014/260949/ This paper presents a synthesis of a volumetric ring antenna array for a terrestrial coverage pattern. This synthesis regards the spacing among the rings on the planes -, the positions of the rings on the plane -, and uniform and concentric excitations. The optimization is carried out by implementing the particle swarm optimization. The synthesis is compared with previous designs by resulting with proper performance of this geometry to provide an accurate coverage to be applied in satellite applications with a maximum reduction of the antenna hardware as well as the side lobe level reduction. Alberto Reyna, Marco A. Panduro, and Carlos Del Rio Bocio Copyright © 2014 Alberto Reyna et al. All rights reserved. Analysis and Modeling of Realistic Compound Channels in Transparent Relay Transmissions Tue, 18 Feb 2014 06:05:01 +0000 http://www.hindawi.com/journals/tswj/2014/538578/ Analytical approaches for the characterisation of the compound channels in transparent multihop relay transmissions over independent fading channels are considered in this paper. Compound channels with homogeneous links are considered first. Using Mellin transform technique, exact expressions are derived for the moments of cascaded Weibull distributions. Subsequently, two performance metrics, namely, coefficient of variation and amount of fade, are derived using the computed moments. These metrics quantify the possible variations in the channel gain and signal to noise ratio from their respective average values and can be used to characterise the achievable receiver performance. This approach is suitable for analysing more realistic compound channel models for scattering density variations of the environment, experienced in multihop relay transmissions. The performance metrics for such heterogeneous compound channels having distinct distribution in each hop are computed and compared with those having identical constituent component distributions. The moments and the coefficient of variation computed are then used to develop computationally efficient estimators for the distribution parameters and the optimal hop count. The metrics and estimators proposed are complemented with numerical and simulation results to demonstrate the impact of the accuracy of the approaches. Cibile K. Kanjirathumkal, Sameer S. Mohammed, and Lillykutty Jacob Copyright © 2014 Cibile K. Kanjirathumkal et al. All rights reserved. Reputation Revision Method for Selecting Cloud Services Based on Prior Knowledge and a Market Mechanism Mon, 17 Feb 2014 06:20:39 +0000 http://www.hindawi.com/journals/tswj/2014/617087/ The trust levels of cloud services should be evaluated to ensure their reliability. The effectiveness of these evaluations has major effects on user satisfaction, which is increasingly important. However, it is difficult to provide objective evaluations in open and dynamic environments because of the possibilities of malicious evaluations, individual preferences, and intentional praise. In this study, we propose a novel unfair rating filtering method for a reputation revision system. This method uses prior knowledge as the basis of similarity when calculating the average rating, which facilitates the recognition and filtering of unfair ratings. In addition, the overall performance is increased by a market mechanism that allows users and service providers to adjust their choice of services and service configuration in a timely manner. The experimental results showed that this method filtered unfair ratings in an effective manner, which greatly improved the precision of the reputation revision system. Qingtao Wu, Xulong Zhang, Mingchuan Zhang, Ying Lou, Ruijuan Zheng, and Wangyang Wei Copyright © 2014 Qingtao Wu et al. All rights reserved. Printed Wide-Slot Antenna Design with Bandwidth and Gain Enhancement on Low-Cost Substrate Thu, 13 Feb 2014 16:21:59 +0000 http://www.hindawi.com/journals/tswj/2014/804068/ This paper presents a printed wide-slot antenna design and prototyping on available low-cost polymer resin composite material fed by a microstrip line with a rotated square slot for bandwidth enhancement and defected ground structure for gain enhancement. An I-shaped microstrip line is used to excite the square slot. The rotated square slot is embedded in the middle of the ground plane, and its diagonal points are implanted in the middle of the strip line and ground plane. To increase the gain, four L-shaped slots are etched in the ground plane. The measured results show that the proposed structure retains a wide impedance bandwidth of 88.07%, which is 20% better than the reference antenna. The average gain is also increased, which is about 4.17 dBi with a stable radiation pattern in the entire operating band. Moreover, radiation efficiency, input impedance, current distribution, axial ratio, and parametric studies of S11 for different design parameters are also investigated using the finite element method-based simulation software HFSS. M. Samsuzzaman, M. T. Islam, J. S. Mandeep, and N. Misran Copyright © 2014 M. Samsuzzaman et al. All rights reserved. An Energy-Aware Routing Protocol for Query-Based Applications in Wireless Sensor Networks Thu, 13 Feb 2014 14:04:30 +0000 http://www.hindawi.com/journals/tswj/2014/359897/ Wireless sensor network (WSN) typically has energy consumption restriction. Designing energy-aware routing protocol can significantly reduce energy consumption in WSNs. Energy-aware routing protocols can be classified into two categories, energy savers and energy balancers. Energy saving protocols are used to minimize the overall energy consumed by a WSN, while energy balancing protocols attempt to efficiently distribute the consumption of energy throughout the network. In general terms, energy saving protocols are not necessarily good at balancing energy consumption and energy balancing protocols are not always good at reducing energy consumption. In this paper, we propose an energy-aware routing protocol (ERP) for query-based applications in WSNs, which offers a good trade-off between traditional energy balancing and energy saving objectives and supports a soft real time packet delivery. This is achieved by means of fuzzy sets and learning automata techniques along with zonal broadcasting to decrease total energy consumption. Ehsan Ahvar, Shohreh Ahvar, Gyu Myoung Lee, and Noel Crespi Copyright © 2014 Ehsan Ahvar et al. All rights reserved. An Empirical Evaluation of Lightweight Random Walk Based Routing Protocol in Duty Cycle Aware Wireless Sensor Networks Thu, 13 Feb 2014 13:13:13 +0000 http://www.hindawi.com/journals/tswj/2014/946249/ Energy efficiency is an important design paradigm in Wireless Sensor Networks (WSNs) and its consumption in dynamic environment is even more critical. Duty cycling of sensor nodes is used to address the energy consumption problem. However, along with advantages, duty cycle aware networks introduce some complexities like synchronization and latency. Due to their inherent characteristics, many traditional routing protocols show low performance in densely deployed WSNs with duty cycle awareness, when sensor nodes are supposed to have high mobility. In this paper we first present a three messages exchange Lightweight Random Walk Routing (LRWR) protocol and then evaluate its performance in WSNs for routing low data rate packets. Through NS-2 based simulations, we examine the LRWR protocol by comparing it with DYMO, a widely used WSN protocol, in both static and dynamic environments with varying duty cycles, assuming the standard IEEE 802.15.4 in lower layers. Results for the three metrics, that is, reliability, end-to-end delay, and energy consumption, show that LRWR protocol outperforms DYMO in scalability, mobility, and robustness, showing this protocol as a suitable choice in low duty cycle and dense WSNs. Adnan Noor Mian, Mehwish Fatima, Raees Khan, and Ravi Prakash Copyright © 2014 Adnan Noor Mian et al. All rights reserved. Cloud Service Selection Using Multicriteria Decision Analysis Thu, 13 Feb 2014 11:10:15 +0000 http://www.hindawi.com/journals/tswj/2014/459375/ Cloud computing (CC) has recently been receiving tremendous attention from the IT industry and academic researchers. CC leverages its unique services to cloud customers in a pay-as-you-go, anytime, anywhere manner. Cloud services provide dynamically scalable services through the Internet on demand. Therefore, service provisioning plays a key role in CC. The cloud customer must be able to select appropriate services according to his or her needs. Several approaches have been proposed to solve the service selection problem, including multicriteria decision analysis (MCDA). MCDA enables the user to choose from among a number of available choices. In this paper, we analyze the application of MCDA to service selection in CC. We identify and synthesize several MCDA techniques and provide a comprehensive analysis of this technology for general readers. In addition, we present a taxonomy derived from a survey of the current literature. Finally, we highlight several state-of-the-art practical aspects of MCDA implementation in cloud computing service selection. The contributions of this study are four-fold: (a) focusing on the state-of-the-art MCDA techniques, (b) highlighting the comparative analysis and suitability of several MCDA methods, (c) presenting a taxonomy through extensive literature review, and (d) analyzing and summarizing the cloud computing service selections in different scenarios. Md Whaiduzzaman, Abdullah Gani, Nor Badrul Anuar, Muhammad Shiraz, Mohammad Nazmul Haque, and Israat Tanzeena Haque Copyright © 2014 Md Whaiduzzaman et al. All rights reserved. Performance Analysis of MIMO-STBC Systems with Higher Coding Rate Using Adaptive Semiblind Channel Estimation Scheme Wed, 12 Feb 2014 12:19:51 +0000 http://www.hindawi.com/journals/tswj/2014/304901/ Semiblind channel estimation method provides the best trade-off in terms of bandwidth overhead, computational complexity and latency. The result after using multiple input multiple output (MIMO) systems shows higher data rate and longer transmit range without any requirement for additional bandwidth or transmit power. This paper presents the detailed analysis of diversity coding techniques using MIMO antenna systems. Different space time block codes (STBCs) schemes have been explored and analyzed with the proposed higher code rate. STBCs with higher code rates have been simulated for different modulation schemes using MATLAB environment and the simulated results have been compared in the semiblind environment which shows the improvement even in highly correlated antenna arrays and is found very close to the condition when channel state information (CSI) is known to the channel. Ravi Kumar and Rajiv Saxena Copyright © 2014 Ravi Kumar and Rajiv Saxena. All rights reserved. Low-Bit Rate Feedback Strategies for Iterative IA-Precoded MIMO-OFDM-Based Systems Tue, 11 Feb 2014 14:05:10 +0000 http://www.hindawi.com/journals/tswj/2014/619454/ Interference alignment (IA) is a promising technique that allows high-capacity gains in interference channels, but which requires the knowledge of the channel state information (CSI) for all the system links. We design low-complexity and low-bit rate feedback strategies where a quantized version of some CSI parameters is fed back from the user terminal (UT) to the base station (BS), which shares it with the other BSs through a limited-capacity backhaul network. This information is then used by BSs to perform the overall IA design. With the proposed strategies, we only need to send part of the CSI information, and this can even be sent only once for a set of data blocks transmitted over time-varying channels. These strategies are applied to iterative MMSE-based IA techniques for the downlink of broadband wireless OFDM systems with limited feedback. A new robust iterative IA technique, where channel quantization errors are taken into account in IA design, is also proposed and evaluated. With our proposed strategies, we need a small number of quantization bits to transmit and share the CSI, when comparing with the techniques used in previous works, while allowing performance close to the one obtained with perfect channel knowledge. Sara Teodoro, Adão Silva, Rui Dinis, and Atílio Gameiro Copyright © 2014 Sara Teodoro et al. All rights reserved. Augmented Lagrange Based on Modified Covariance Matching Criterion Method for DOA Estimation in Compressed Sensing Tue, 11 Feb 2014 13:23:48 +0000 http://www.hindawi.com/journals/tswj/2014/241469/ A novel direction of arrival (DOA) estimation method in compressed sensing (CS) is presented, in which DOA estimation is considered as the joint sparse recovery from multiple measurement vectors (MMV). The proposed method is obtained by minimizing the modified-based covariance matching criterion, which is acquired by adding penalties according to the regularization method. This minimization problem is shown to be a semidefinite program (SDP) and transformed into a constrained quadratic programming problem for reducing computational complexity which can be solved by the augmented Lagrange method. The proposed method can significantly improve the performance especially in the scenarios with low signal to noise ratio (SNR), small number of snapshots, and closely spaced correlated sources. In addition, the Cramér-Rao bound (CRB) of the proposed method is developed and the performance guarantee is given according to a version of the restricted isometry property (RIP). The effectiveness and satisfactory performance of the proposed method are illustrated by simulation results. Weijian Si, Xinggen Qu, and Lutao Liu Copyright © 2014 Weijian Si et al. All rights reserved. Design of Pulse Waveform for Waveform Division Multiple Access UWB Wireless Communication System Tue, 11 Feb 2014 11:48:17 +0000 http://www.hindawi.com/journals/tswj/2014/171875/ A new multiple access scheme, Waveform Division Multiple Access (WDMA) based on the orthogonal wavelet function, is presented. After studying the correlation properties of different categories of single wavelet functions, the one with the best correlation property will be chosen as the foundation for combined waveform. In the communication system, each user is assigned to different combined orthogonal waveform. Demonstrated by simulation, combined waveform is more suitable than single wavelet function to be a communication medium in WDMA system. Due to the excellent orthogonality, the bit error rate (BER) of multiuser with combined waveforms is so close to that of single user in a synchronous system. That is to say, the multiple access interference (MAI) is almost eliminated. Furthermore, even in an asynchronous system without multiuser detection after matched filters, the result is still pretty ideal and satisfactory by using the third combination mode that will be mentioned in the study. Zhendong Yin, Zhirui Wang, Xiaohui Liu, and Zhilu Wu Copyright © 2014 Zhendong Yin et al. All rights reserved. Integration and Analysis of Neighbor Discovery and Link Quality Estimation in Wireless Sensor Networks Tue, 11 Feb 2014 07:48:01 +0000 http://www.hindawi.com/journals/tswj/2014/789642/ Network connectivity and link quality information are the fundamental requirements of wireless sensor network protocols to perform their desired functionality. Most of the existing discovery protocols have only focused on the neighbor discovery problem, while a few number of them provide an integrated neighbor search and link estimation. As these protocols require a careful parameter adjustment before network deployment, they cannot provide scalable and accurate network initialization in large-scale dense wireless sensor networks with random topology. Furthermore, performance of these protocols has not entirely been evaluated yet. In this paper, we perform a comprehensive simulation study on the efficiency of employing adaptive protocols compared to the existing nonadaptive protocols for initializing sensor networks with random topology. In this regard, we propose adaptive network initialization protocols which integrate the initial neighbor discovery with link quality estimation process to initialize large-scale dense wireless sensor networks without requiring any parameter adjustment before network deployment. To the best of our knowledge, this work is the first attempt to provide a detailed simulation study on the performance of integrated neighbor discovery and link quality estimation protocols for initializing sensor networks. This study can help system designers to determine the most appropriate approach for different applications. Marjan Radi, Behnam Dezfouli, Kamalrulnizam Abu Bakar, and Shukor Abd Razak Copyright © 2014 Marjan Radi et al. All rights reserved. A New Subcarrier Allocation Strategy for MIMO-OFDMA Multicellular Networks Based on Cooperative Interference Mitigation Mon, 10 Feb 2014 10:28:45 +0000 http://www.hindawi.com/journals/tswj/2014/652968/ The goal of the study presented in this paper is to investigate the performance of a new subcarrier allocation strategy for Orthogonal Frequency Division Multiple Access (OFDMA) multicellular networks which employ Multiple Input Multiple Output (MIMO) architecture. For this reason, a hybrid system-link level simulator has been developed executing independent Monte Carlo (MC) simulations in parallel. Up to two tiers of cells around the central cell are taken into consideration and increased loading per cell. The derived results indicate that this strategy can provide up to 12% capacity gain for 16-QAM modulation and two tiers of cells around the central cell in a symmetric MIMO configuration. This gain is derived when comparing the proposed strategy to the traditional approach of allocating subcarriers that maximize only the desired user’s signal. Panagiotis K. Gkonis, Maria A. Seimeni, Nikolaos P. Asimakis, Dimitra I. Kaklamani, and Iakovos S. Venieris Copyright © 2014 Panagiotis K. Gkonis et al. All rights reserved. On the Degrees of Freedom of Interference Alignment for Multicell MIMO Interfering Broadcast Channels Mon, 10 Feb 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/827357/ The interference alignment (IA) is a promising technique to efficiently mitigate interference and to enhance capacity of a wireless network. This paper proposes an interference alignment scheme for a cellular network with L cells and K users under a multiple-input multiple-output (MIMO) Gaussian interfering broadcast channel (IFBC) scenario. The proposed IA scheme aligns intercell interferences (ICI) into a small dimensional subspace through a cooperative receive beamforming and cancels both the ICI and interuser interferences (IUI) simultaneously through a transmit beamforming. We characterize the feasibility condition for the proposed IA to achieve a total number of degrees of freedom (DoF) of LK in terms of the numbers of transmit antennas and receive antennas. Then we derive the maximum number of DoF achieved by the proposed IA by finding an optimal dimension of ICI alignment subspace for a given antenna configuration. The numerical results show that the proposed IA scheme has a better DoF performance than the conventional schemes. Hyun-Ho Choi Copyright © 2014 Hyun-Ho Choi. All rights reserved. Network Efficient Power Control for Wireless Communication Systems Sun, 09 Feb 2014 13:31:37 +0000 http://www.hindawi.com/journals/tswj/2014/650653/ We introduce a two-loop power control that allows an efficient use of the overall power resources for commercial wireless networks based on cross-layer optimization. This approach maximizes the network’s utility in the outer-loop as a function of the averaged signal to interference-plus-noise ratio (SINR) by considering adaptively the changes in the network characteristics. For this purpose, the concavity property of the utility function was verified with respect to the SINR, and an iterative search was proposed with guaranteed convergence. In addition, the outer-loop is in charge of selecting the detector that minimizes the overall power consumption (transmission and detection). Next the inner-loop implements a feedback power control in order to achieve the optimal SINR in the transmissions despite channel variations and roundtrip delays. In our proposal, the utility maximization process and detector selection and feedback power control are decoupled problems, and as a result, these strategies are implemented at two different time scales in the two-loop framework. Simulation results show that substantial utility gains may be achieved by improving the power management in the wireless network. Daniel U. Campos-Delgado, Jose Martin Luna-Rivera, C. J. Martinez-Sánchez, Carlos A. Gutierrez, and J. L. Tecpanecatl-Xihuitl Copyright © 2014 Daniel U. Campos-Delgado et al. All rights reserved. Error Analysis for RADAR Neighbor Matching Localization in Linear Logarithmic Strength Varying Wi-Fi Environment Sun, 09 Feb 2014 11:21:26 +0000 http://www.hindawi.com/journals/tswj/2014/647370/ This paper studies the statistical errors for the fingerprint-based RADAR neighbor matching localization with the linearly calibrated reference points (RPs) in logarithmic received signal strength (RSS) varying Wi-Fi environment. To the best of our knowledge, little comprehensive analysis work has appeared on the error performance of neighbor matching localization with respect to the deployment of RPs. However, in order to achieve the efficient and reliable location-based services (LBSs) as well as the ubiquitous context-awareness in Wi-Fi environment, much attention has to be paid to the highly accurate and cost-efficient localization systems. To this end, the statistical errors by the widely used neighbor matching localization are significantly discussed in this paper to examine the inherent mathematical relations between the localization errors and the locations of RPs by using a basic linear logarithmic strength varying model. Furthermore, based on the mathematical demonstrations and some testing results, the closed-form solutions to the statistical errors by RADAR neighbor matching localization can be an effective tool to explore alternative deployment of fingerprint-based neighbor matching localization systems in the future. Mu Zhou, Zengshan Tian, Kunjie Xu, Xiang Yu, and Haibo Wu Copyright © 2014 Mu Zhou et al. All rights reserved. Fault Tolerant Mobile Sensor Node Traversal Schemes Based on Hexagonal Coverage Thu, 06 Feb 2014 11:10:27 +0000 http://www.hindawi.com/journals/tswj/2014/130793/ Mobile sensor nodes (MSNs) are equipped with locomotive can move around after having been deployed. They are equipped with limited energy. A large portion of energy is drained during the traversal. In order to extend the life time of a MSN, the traveling distance must be minimized. Region of interest (ROI) is covered with multiple MSNs using coverage based pattern movement. When a group of MSNs are deployed to cover a given ROI, all the deployed MSNs should travel an approximately equal distance. Otherwise, the MSN which travels longer distance depletes more energy compared to the MSN which travels a shorter distance. In this work we show that, ROI partition plays great role in hole free coverage and makes the MSNs have optimized movement cost with fault tolerant support. Ganala Santoshi and R. J. D’Souza Copyright © 2014 Ganala Santoshi and R. J. D’Souza. All rights reserved. Data Delivery Method Based on Neighbor Nodes’ Information in a Mobile Ad Hoc Network Tue, 04 Feb 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/793171/ This paper proposes a data delivery method based on neighbor nodes’ information to achieve reliable communication in a mobile ad hoc network (MANET). In a MANET, it is difficult to deliver data reliably due to instabilities in network topology and wireless network condition which result from node movement. To overcome such unstable communication, opportunistic routing and network coding schemes have lately attracted considerable attention. Although an existing method that employs such schemes, MAC-independent opportunistic routing and encoding (MORE), Chachulski et al. (2007), improves the efficiency of data delivery in an unstable wireless mesh network, it does not address node movement. To efficiently deliver data in a MANET, the method proposed in this paper thus first employs the same opportunistic routing and network coding used in MORE and also uses the location information and transmission probabilities of neighbor nodes to adapt to changeable network topology and wireless network condition. The simulation experiments showed that the proposed method can achieve efficient data delivery with low network load when the movement speed is relatively slow. Shigeru Kashihara, Takuma Hayashi, Yuzo Taenaka, Takeshi Okuda, and Suguru Yamaguchi Copyright © 2014 Shigeru Kashihara et al. All rights reserved. Fabrication of CPW-Fed Fractal Antenna for UWB Applications with Omni-Directional Patterns Mon, 03 Feb 2014 11:40:38 +0000 http://www.hindawi.com/journals/tswj/2014/391602/ Novel and compact CPW-fed antennas are proposed comprised of a fractal patch and modified ground-plane. The ground-plane is truncated at the center and includes dielectric notches at its side to enhance the antenna’s impedance bandwidth. The dimensions of the notches effectively control the upper and lower band edges of the antenna. The optimized antenna operates across 2.95–12.81 GHz for  dB. Omnidirectional radiation pattern is achieved over the full UWB frequency range. The miniaturized antenna has a total size of  mm3. The characteristics of the proposed antenna are suitable for UWB wireless communication requiring low profile antennas. Tohid Sedghi, Mahdi Jalali, and Tohid Aribi Copyright © 2014 Tohid Sedghi et al. All rights reserved. QoS-Oriented High Dynamic Resource Allocation in Vehicular Communication Networks Thu, 30 Jan 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/718698/ Vehicular ad hoc networks (VANETs) are emerging as new research area and attracting an increasing attention from both industry and research communities. In this context, a dynamic resource allocation policy that maximizes the use of available resources and meets the quality of service (QoS) requirement of constraining applications is proposed. It is a combination of a fair packet scheduling policy and a new adaptive QoS oriented call admission control (CAC) scheme based on the vehicle density variation. This scheme decides whether the connection request is to be admitted into the system, while providing fair access and guaranteeing the desired throughput. The proposed algorithm showed good performance in testing in real world environment. Tarek Bejaoui Copyright © 2014 Tarek Bejaoui. All rights reserved. Coverage Extension and Balancing the Transmitted Power of the Moving Relay Node at LTE-A Cellular Network Wed, 29 Jan 2014 06:50:27 +0000 http://www.hindawi.com/journals/tswj/2014/815720/ The poor capacity at cell boundaries is not enough to meet the growing demand and stringent design which required high capacity and throughput irrespective of user’s location in the cellular network. In this paper, we propose new schemes for an optimum fixed relay node (RN) placement in LTE-A cellular network to enhance throughput and coverage extension at cell edge region. The proposed approach mitigates interferences between all nodes and ensures optimum utilization with the optimization of transmitted power. Moreover, we proposed a new algorithm to balance the transmitted power of moving relay node (MR) over cell size and providing required SNR and throughput at the users inside vehicle along with reducing the transmitted power consumption by MR. The numerical analysis along with the simulation results indicates that an improvement in capacity for users is 40% increment at downlink transmission from cell capacity. Furthermore, the results revealed that there is saving nearly 75% from transmitted power in MR after using proposed balancing algorithm. ATDI simulator was used to verify the numerical results, which deals with real digital cartographic and standard formats for terrain. Jaafar A. Aldhaibani, Abid Yahya, and R. Badlishah Ahmad Copyright © 2014 Jaafar A. Aldhaibani et al. All rights reserved. Augmented Twin-Nonlinear Two-Box Behavioral Models for Multicarrier LTE Power Amplifiers Wed, 29 Jan 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/762534/ A novel class of behavioral models is proposed for LTE-driven Doherty power amplifiers with strong memory effects. The proposed models, labeled augmented twin-nonlinear two-box models, are built by cascading a highly nonlinear memoryless function with a mildly nonlinear memory polynomial with cross terms. Experimental validation on gallium nitride based Doherty power amplifiers illustrates the accuracy enhancement and complexity reduction achieved by the proposed models. When strong memory effects are observed, the augmented twin-nonlinear two-box models can improve the normalized mean square error by up to 3 dB for the same number of coefficients when compared to state-of-the-art twin-nonlinear two-box models. Furthermore, the augmented twin-nonlinear two-box models lead to the same performance as previously reported twin-nonlinear two-box models while requiring up to 80% less coefficients. Oualid Hammi Copyright © 2014 Oualid Hammi. All rights reserved. Video Conferences through the Internet: How to Survive in a Hostile Environment Tue, 28 Jan 2014 07:53:20 +0000 http://www.hindawi.com/journals/tswj/2014/860170/ This paper analyzes and compares two different video conference solutions, widely used in corporate and home environments, with a special focus on the mechanisms used for adapting the traffic to the network status. The results show how these mechanisms are able to provide a good quality in the hostile environment of the public Internet, a best effort network without delay or delivery guarantees. Both solutions are evaluated in a laboratory, where different network impairments (bandwidth limit, delay, and packet loss) are set, in both the uplink and the downlink, and the reaction of the applications is measured. The tests show how these solutions modify their packet size and interpacket time, in order to increase or reduce the sent data. One of the solutions also uses a scalable video codec, able to adapt the traffic to the network status and to the end devices. Carlos Fernández, Jose Saldana, Julián Fernández-Navajas, Luis Sequeira, and Luis Casadesus Copyright © 2014 Carlos Fernández et al. All rights reserved. Design of Simplified Maximum-Likelihood Receivers for Multiuser CPM Systems Mon, 27 Jan 2014 14:02:22 +0000 http://www.hindawi.com/journals/tswj/2014/174294/ A class of simplified maximum-likelihood receivers designed for continuous phase modulation based multiuser systems is proposed. The presented receiver is built upon a front end employing mismatched filters and a maximum-likelihood detector defined in a low-dimensional signal space. The performance of the proposed receivers is analyzed and compared to some existing receivers. Some schemes are designed to implement the proposed receivers and to reveal the roles of different system parameters. Analysis and numerical results show that the proposed receivers can approach the optimum multiuser receivers with significantly (even exponentially in some cases) reduced complexity and marginal performance degradation. Li Bing and Baoming Bai Copyright © 2014 Li Bing and Baoming Bai. All rights reserved. Fault Tolerant Coverage and Connectivity in Presence of Channel Randomness Tue, 21 Jan 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/818135/ Some applications of wireless sensor network require -coverage and -connectivity to ensure the system to be fault tolerance and to make it more reliable. Therefore, it makes coverage and connectivity an important issue in wireless sensor networks. In this paper, we proposed -coverage and -connectivity models for wireless sensor networks. In both models, nodes are distributed according to Poisson distribution in the sensor field. To make the proposed model more realistic we used log-normal shadowing path loss model to capture the radio irregularities and studied its impact on -coverage and -connectivity. The value of can be different for different types of applications. Further, we also analyzed the problem of node failure for -coverage model. In the simulation section, results clearly show that coverage and connectivity of wireless sensor network depend on the node density, shadowing parameters like the path loss exponent, and standard deviation. Anil Kumar Sagar and D. K. Lobiyal Copyright © 2014 Anil Kumar Sagar and D. K. Lobiyal. All rights reserved. Optimal Throughput for Cognitive Radio with Energy Harvesting in Fading Wireless Channel Mon, 20 Jan 2014 12:55:11 +0000 http://www.hindawi.com/journals/tswj/2014/370658/ Energy resource management is a crucial problem of a device with a finite capacity battery. In this paper, cognitive radio is considered to be a device with an energy harvester that can harvest energy from a non-RF energy resource while performing other actions of cognitive radio. Harvested energy will be stored in a finite capacity battery. At the start of the time slot of cognitive radio, the radio needs to determine if it should remain silent or carry out spectrum sensing based on the idle probability of the primary user and the remaining energy in order to maximize the throughput of the cognitive radio system. In addition, optimal sensing energy and adaptive transmission power control are also investigated in this paper to effectively utilize the limited energy of cognitive radio. Finding an optimal approach is formulated as a partially observable Markov decision process. The simulation results show that the proposed optimal decision scheme outperforms the myopic scheme in which current throughput is only considered when making a decision. Hiep Vu-Van and Insoo Koo Copyright © 2014 Hiep Vu-Van and Insoo Koo. All rights reserved. Novel Wideband MIMO Antennas That Can Cover the Whole LTE Spectrum in Handsets and Portable Computers Thu, 16 Jan 2014 12:08:33 +0000 http://www.hindawi.com/journals/tswj/2014/694805/ A dual resonant antenna configuration is developed for multistandard multifunction mobile handsets and portable computers. Only two wideband resonant antennas can cover most of the LTE spectrums in portable communication equipment. The bandwidth that can be covered by each antenna exceeds 70% without using any matching or tuning circuits, with efficiencies that reach 80%. Thus, a dual configuration of them is capable of covering up to 39 LTE (4G) bands besides the existing 2G and 3G bands. MIMO configurations have been also developed for the two wideband antennas with a maximum isolation and a minimum correlation coefficient between the primary and the diversity antennas. Mohamed Sanad and Noha Hassan Copyright © 2014 Mohamed Sanad and Noha Hassan. All rights reserved. Hybrid Network Defense Model Based on Fuzzy Evaluation Thu, 16 Jan 2014 12:02:23 +0000 http://www.hindawi.com/journals/tswj/2014/178937/ With sustained and rapid developments in the field of information technology, the issue of network security has become increasingly prominent. The theme of this study is network data security, with the test subject being a classified and sensitive network laboratory that belongs to the academic network. The analysis is based on the deficiencies and potential risks of the network’s existing defense technology, characteristics of cyber attacks, and network security technologies. Subsequently, a distributed network security architecture using the technology of an intrusion prevention system is designed and implemented. In this paper, first, the overall design approach is presented. This design is used as the basis to establish a network defense model, an improvement over the traditional single-technology model that addresses the latter’s inadequacies. Next, a distributed network security architecture is implemented, comprising a hybrid firewall, intrusion detection, virtual honeynet projects, and connectivity and interactivity between these three components. Finally, the proposed security system is tested. A statistical analysis of the test results verifies the feasibility and reliability of the proposed architecture. The findings of this study will potentially provide new ideas and stimuli for future designs of network security architecture. Ying-Chiang Cho and Jen-Yi Pan Copyright © 2014 Ying-Chiang Cho and Jen-Yi Pan. All rights reserved. Low-Complexity User Selection for Rate Maximization in MIMO Broadcast Channels with Downlink Beamforming Thu, 16 Jan 2014 11:58:05 +0000 http://www.hindawi.com/journals/tswj/2014/865905/ We present in this work a low-complexity algorithm to solve the sum rate maximization problem in multiuser MIMO broadcast channels with downlink beamforming. Our approach decouples the user selection problem from the resource allocation problem and its main goal is to create a set of quasiorthogonal users. The proposed algorithm exploits physical metrics of the wireless channels that can be easily computed in such a way that a null space projection power can be approximated efficiently. Based on the derived metrics we present a mathematical model that describes the dynamics of the user selection process which renders the user selection problem into an integer linear program. Numerical results show that our approach is highly efficient to form groups of quasiorthogonal users when compared to previously proposed algorithms in the literature. Our user selection algorithm achieves a large portion of the optimum user selection sum rate (90%) for a moderate number of active users. Eduardo Castañeda, Adão Silva, Ramiro Samano-Robles, and Atílio Gameiro Copyright © 2014 Eduardo Castañeda et al. All rights reserved. Evaluation of Clipping Based Iterative PAPR Reduction Techniques for FBMC Systems Thu, 16 Jan 2014 10:05:06 +0000 http://www.hindawi.com/journals/tswj/2014/841680/ This paper investigates filter bankmulticarrier (FBMC), a multicarrier modulation technique exhibiting an extremely low adjacent channel leakage ratio (ACLR) compared to conventional orthogonal frequency division multiplexing (OFDM) technique. The low ACLR of the transmitted FBMC signal makes it especially favorable in cognitive radio applications, where strict requirements are posed on out-of-band radiation. Large dynamic range resulting in high peak-to-average power ratio (PAPR) is characteristic of all sorts of multicarrier signals. The advantageous spectral properties of the high-PAPR FBMC signal are significantly degraded if nonlinearities are present in the transceiver chain. Spectral regrowth may appear, causing harmful interference in the neighboring frequency bands. This paper presents novel clipping based PAPR reduction techniques, evaluated and compared by simulations and measurements, with an emphasis on spectral aspects. The paper gives an overall comparison of PAPR reduction techniques, focusing on the reduction of the dynamic range of FBMC signals without increasing out-of-band radiation. An overview is presented on transmitter oriented techniques employing baseband clipping, which can maintain the system performance with a desired bit error rate (BER). Zsolt Kollár, Lajos Varga, Bálint Horváth, Péter Bakki, and János Bitó Copyright © 2014 Zsolt Kollár et al. All rights reserved. Social Network Supported Process Recommender System Wed, 15 Jan 2014 15:20:49 +0000 http://www.hindawi.com/journals/tswj/2014/349065/ Process recommendation technologies have gained more and more attention in the field of intelligent business process modeling to assist the process modeling. However, most of the existing technologies only use the process structure analysis and do not take the social features of processes into account, while the process modeling is complex and comprehensive in most situations. This paper studies the feasibility of social network research technologies on process recommendation and builds a social network system of processes based on the features similarities. Then, three process matching degree measurements are presented and the system implementation is discussed subsequently. Finally, experimental evaluations and future works are introduced. Yanming Ye, Jianwei Yin, and Yueshen Xu Copyright © 2014 Yanming Ye et al. All rights reserved. Structured P2P Overlay of Mobile Brokers for Realizing Publish/Subscribe Communication in VANET Sun, 12 Jan 2014 11:39:48 +0000 http://www.hindawi.com/journals/tswj/2014/136365/ Publish/subscribe communication paradigm provides asynchrony and decoupling, making it an elegant alternative for designing applications in distributed and dynamic environment such as vehicular ad hoc networks (VANETs). In this paradigm, the broker is the most important component that decouples other two components, namely, publisher and subscriber. Previous research efforts have either utilized the deployment of distributed brokers on stationary road side info-stations or have assigned the role of broker to any moving vehicle on ad hoc basis. In one approach, lots of preinstalled infrastructures are needed whereas, in another, the quality of service is not guaranteed due to unpredictable moving and stopping patterns of vehicles. In this paper, we present the architecture of distributed mobile brokers which are dynamically reconfigurable in the form of structured P2P overlay and act as rendezvous points for matching publications and subscriptions. We have taken city buses in urban settings to act as mobile brokers whereas other vehicles are considered to be in role of publishers and subscribers. These mobile brokers also assist in locating a vehicle for successful and timely transfer of notifications. We have performed an extensive simulation study to compare our approach with previously proposed approaches. Simulation results establish the applicability of our approach. Tulika Pandey, Deepak Garg, and Manoj Madhava Gore Copyright © 2014 Tulika Pandey et al. All rights reserved. A Downlink and Uplink Alignment Scheme for Power Saving in IEEE 802.16 Protocol Sun, 12 Jan 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/217973/ This study shows the problem of power saving mechanism (PSM) that sleep intervals of uplink (UL) connections do not synchronize with sleep intervals of downlink (DL) connections. That is, the energy of a mobile station (MS) is not really saved if the DL connections are in the sleep mode while the UL connections are in normal mode, and vice versa. To avoid the asynchronism of power saving (PS) between UL and DL connections, we invent a mechanism of DL connections regulating UL connections, called DL and UL Alignment (DUAL) scheme, to improve the energy efficiency for PS. Considering that the buffer size of MS is limited, DUAL uses the mean packet arrival rate of UL and a relatively safe threshold of buffer size as the parameters to estimate the maximum allowable waiting time to align the UL with the DL connections. To analyze the performance of DUAL, a system model of PS is proposed to evaluate the performance of DUAL under different conditions. The correctness of performance analysis of DUAL is validated by using simulation with realistic parameters. Numerical experiments show that DUAL improves the energy conservation significantly when UL traffic is greater than DL traffic. Jenhui Chen, Woei-Hwa Tarn, and Jiann-Der Lee Copyright © 2014 Jenhui Chen et al. All rights reserved. Proactive Schema Based Link Lifetime Estimation and Connectivity Ratio Thu, 09 Jan 2014 14:02:40 +0000 http://www.hindawi.com/journals/tswj/2014/172014/ The radio link between a pair of wireless nodes is affected by a set of random factors such as transmission range, node mobility, and environment conditions. The properties of such radio links are continually experienced when nodes status balances between being reachable and being unreachable; thereby on completion of each experience the statistical distribution of link lifetime is updated. This aspect is emphasized in mobile ad hoc network especially when it is deployed in some fields that require intelligent processing of data information such as aerospace domain. Bouamoud Bachir, Ouacha Ali, Habbani Ahmed, and Elkoutbi Mohamed Copyright © 2014 Bouamoud Bachir et al. All rights reserved. Multiple Power-Saving MSSs Scheduling Methods for IEEE802.16e Broadband Wireless Networks Thu, 09 Jan 2014 08:52:22 +0000 http://www.hindawi.com/journals/tswj/2014/957158/ This work proposes two enhanced multiple mobile subscriber stations (MSSs) power-saving scheduling methods for IEEE802.16e broadband wireless networks. The proposed methods are designed for the Unsolicited Grant Service (UGS) of IEEE802.16e. To reduce the active periods of all power-saving MSSs, the base station (BS) allocates each MSS fewest possible transmission frames to retrieve its data from the BS. The BS interlaces the active periods of each MSS to increase the amount of scheduled MSSs and splits the overflowing transmission frames to maximize the bandwidth utilization. Simulation results reveal that interlacing the active periods of MSSs can increase the number of scheduled MSSs to more than four times of that in the Direct scheduling method. The bandwidth utilization can thus be improved by 60%–70%. Splitting the overflowing transmission frames can improve bandwidth utilization by more than 10% over that achieved using the method of interlacing active periods, with a sacrifice of only 1% of the sleep periods in the interlacing active period method. Shih-Chang Huang Copyright © 2014 Shih-Chang Huang. All rights reserved. Compressed Wideband Spectrum Sensing Based on Discrete Cosine Transform Wed, 08 Jan 2014 15:39:04 +0000 http://www.hindawi.com/journals/tswj/2014/464895/ Discrete cosine transform (DCT) is a special type of transform which is widely used for compression of speech and image. However, its use for spectrum sensing has not yet received widespread attention. This paper aims to alleviate the sampling requirements of wideband spectrum sensing by utilizing the compressive sampling (CS) principle and exploiting the unique sparsity structure in the DCT domain. Compared with discrete Fourier transform (DFT), wideband communication signal has much sparser representation and easier implementation in DCT domain. Simulation result shows that the proposed DCT-CSS scheme outperforms the conventional DFT-CSS scheme in terms of MSE of reconstruction signal, detection probability, and computational complexity. Yulin Wang and Gengxin Zhang Copyright © 2014 Yulin Wang and Gengxin Zhang. All rights reserved. Classification Based on Pruning and Double Covered Rule Sets for the Internet of Things Applications Sun, 05 Jan 2014 14:31:57 +0000 http://www.hindawi.com/journals/tswj/2014/984375/ The Internet of things (IOT) is a hot issue in recent years. It accumulates large amounts of data by IOT users, which is a great challenge to mining useful knowledge from IOT. Classification is an effective strategy which can predict the need of users in IOT. However, many traditional rule-based classifiers cannot guarantee that all instances can be covered by at least two classification rules. Thus, these algorithms cannot achieve high accuracy in some datasets. In this paper, we propose a new rule-based classification, CDCR-P (Classification based on the Pruning and Double Covered Rule sets). CDCR-P can induce two different rule sets and . Every instance in training set can be covered by at least one rule not only in rule set , but also in rule set . In order to improve the quality of rule set , we take measure to prune the length of rules in rule set . Our experimental results indicate that, CDCR-P not only is feasible, but also it can achieve high accuracy. Shasha Li, Zhongmei Zhou, and Weiping Wang Copyright © 2014 Shasha Li et al. All rights reserved. Enhanced Handoff Scheme for Downlink-Uplink Asymmetric Channels in Cellular Systems Tue, 31 Dec 2013 17:43:36 +0000 http://www.hindawi.com/journals/tswj/2013/241483/ In the latest cellular networks, data services like SNS and UCC can create asymmetric packet generation rates over the downlink and uplink channels. This asymmetry can lead to a downlink-uplink asymmetric channel condition being experienced by cell edge users. This paper proposes a handoff scheme to cope effectively with downlink-uplink asymmetric channels. The proposed handoff scheme exploits the uplink channel quality as well as the downlink channel quality to determine the appropriate timing and direction of handoff. We first introduce downlink and uplink channel models that consider the intercell interference, to verify the downlink-uplink channel asymmetry. Based on these results, we propose an enhanced handoff scheme that exploits both the uplink and downlink channel qualities to reduce the handoff-call dropping probability and the service interruption time. The simulation results show that the proposed handoff scheme reduces the handoff-call dropping probability about 30% and increases the satisfaction of the service interruption time requirement about 7% under high-offered load, compared to conventional mobile-assisted handoff. Especially, the proposed handoff scheme is more efficient when the uplink QoS requirement is much stricter than the downlink QoS requirement or uplink channel quality is worse than downlink channel quality. Sunghyun Cho, Ji-Su Kim, and Jae-Hyun Kim Copyright © 2013 Sunghyun Cho et al. All rights reserved. Beamforming of Joint Polarization-Space Matched Filtering for Conformal Array Tue, 31 Dec 2013 08:08:15 +0000 http://www.hindawi.com/journals/tswj/2013/589675/ Due to the polarization mismatch of the antenna, the received signal suffers from energy loss. The conventional beamforming algorithms could not be applied to the conformal array because of the varying curvature. In order to overcome the energy loss of the received signal, a novel joint polarization-space matched filtering algorithm for cylindrical conformal array is proposed. First, the snapshot data model of the conformal polarization sensitive array is analyzed. Second, the analytical expression of polarization sensitive array beamforming is derived. Linearly constrained minimum variance (LCMV) beamforming technique is facilitated for the cylindrical conformal array. Third, the idea of joint polarization-space matched filtering is presented, and the principle of joint polarization-space matched filtering is discussed in detail. Theoretical analysis and computer simulation results verify that the conformal polarization sensitive array is more robust than the ordinary conformal array. The proposed algorithm can improve the performance when signal and interference are too close. It can enhance the signal-to-noise ratio (SNR) by adjusting the polarization of the elements of the conformal array, which matches the polarization of the incident signal. Lutao Liu, Yilin Jiang, Liangtian Wan, and Zuoxi Tian Copyright © 2013 Lutao Liu et al. All rights reserved. Optimal Transport on Weighted Networks for Different Node Delivery Capability Schemes Mon, 30 Dec 2013 18:13:28 +0000 http://www.hindawi.com/journals/tswj/2013/378083/ Many real networks can be best described by weighted networks with a diversity of interactions between nodes measured by the weights of the edges. It is of great importance to improve the overall capacity of these real-world networks. In this paper, the traffic capacity of weighted network is investigated based on three different node delivery capability schemes: the delivery capacity of each node is constant in the first scheme while in the second and third schemes it is proportional to its node degree and node strength. It is shown by simulations that the network transfer capacity depends strongly on the tunable parameter. And different tunable parameter is suitable for different node delivery capability. Fei Shao Copyright © 2013 Fei Shao. All rights reserved. Coexistence of 3G Repeaters with LTE Base Stations Sun, 29 Dec 2013 11:55:41 +0000 http://www.hindawi.com/journals/tswj/2013/185372/ Repeaters have been an attractive solution for mobile operators to upgrade their wireless networks at low cost and to extend network coverage effectively. Since the first LTE commercial deployment in 2009, many mobile operators have launched LTE networks by upgrading their 3G and legacy networks. Because all 3G frequency bands are shared with the frequency bands for LTE deployment and 3G mobile operators have an enormous number of repeaters, reusing 3G repeaters in LTE networks is definitely a practical and cost-efficient solution. However, 3G repeaters usually do not support spatial multiplexing with multiple antennas, and thus it is difficult to reuse them directly in LTE networks. In order to support spatial multiplexing of LTE, the role of 3G repeaters should be replaced with small LTE base stations or MIMO-capable repeaters. In this paper, a repeater network is proposed to reuse 3G repeaters in LTE deployment while still supporting multilayer transmission of LTE. Interestingly, the proposed network has a higher cluster throughput than an LTE network with MIMO-capable repeaters. Woon-Young Yeo, Sang-Min Lee, Gyung-Ho Hwang, and Jae-Hoon Kim Copyright © 2013 Woon-Young Yeo et al. All rights reserved. A Novel Coordinated Edge Caching with Request Filtration in Radio Access Network Sun, 29 Dec 2013 10:32:14 +0000 http://www.hindawi.com/journals/tswj/2013/654536/ Content caching at the base station of the Radio Access Network (RAN) is a way to reduce backhaul transmission and improve the quality of experience. So it is crucial to manage such massive microcaches to store the contents in a coordinated manner, in order to increase the overall mobile network capacity to support more number of requests. We achieve this goal in this paper with a novel caching scheme, which reduces the repeating traffic by request filtration and asynchronous multicast in a RAN. Request filtration can make the best use of the limited bandwidth and in turn ensure the good performance of the coordinated caching. Moreover, the storage at the mobile devices is also considered to be used to further reduce the backhaul traffic and improve the users’ experience. In addition, we drive the optimal cache division in this paper with the aim of reducing the average latency user perceived. The simulation results show that the proposed scheme outperforms existing algorithms. Yang Li, Yuemei Xu, Tao Lin, Xiaohui Wang, and Song Ci Copyright © 2013 Yang Li et al. All rights reserved. A Source-Initiated On-Demand Routing Algorithm Based on the Thorup-Zwick Theory for Mobile Wireless Sensor Networks Wed, 25 Dec 2013 10:30:53 +0000 http://www.hindawi.com/journals/tswj/2013/283852/ The unreliability and dynamics of mobile wireless sensor networks make it hard to perform end-to-end communications. This paper presents a novel source-initiated on-demand routing mechanism for efficient data transmission in mobile wireless sensor networks. It explores the Thorup-Zwick theory to achieve source-initiated on-demand routing with time efficiency. It is able to find out shortest routing path between source and target in a network and transfer data in linear time. The algorithm is easy to be implemented and performed in resource-constrained mobile wireless sensor networks. We also evaluate the approach by analyzing its cost in detail. It can be seen that the approach is efficient to support data transmission in mobile wireless sensor networks. Yuxin Mao and Ping Zhu Copyright © 2013 Yuxin Mao and Ping Zhu. All rights reserved. Derivation of Probability Density Function of Signal-to-Interference-Plus-Noise Ratio for the MS-to-MS Interference Analysis Tue, 24 Dec 2013 18:04:00 +0000 http://www.hindawi.com/journals/tswj/2013/143970/ This paper provides an analytical derivation of the probability density function of signal-to-interference-plus-noise ratio in the scenario where mobile stations interfere with each other. This analysis considers cochannel interference and adjacent channel interference. This could also remove the need for Monte Carlo simulations when evaluating the interference effect between mobile stations. Numerical verification shows that the analytical result agrees well with a Monte Carlo simulation. Also, we applied analytical methods for evaluating the interference effect between mobile stations using adjacent frequency bands. The analytical derivation of the probability density function can be used to provide the technical criteria for sharing a frequency band. Ho-Kyung Son and Che-Young Kim Copyright © 2013 Ho-Kyung Son and Che-Young Kim. All rights reserved. Reconfiguration and Search of Social Networks Wed, 18 Dec 2013 12:08:30 +0000 http://www.hindawi.com/journals/tswj/2013/391782/ Social networks tend to exhibit some topological characteristics different from regular networks and random networks, such as shorter average path length and higher clustering coefficient, and the node degree of the majority of social networks obeys exponential distribution. Based on the topological characteristics of the real social networks, a new network model which suits to portray the structure of social networks was proposed, and the characteristic parameters of the model were calculated. To find out the relationship between two people in the social network, and using the local information of the social network and the parallel mechanism, a hybrid search strategy based on -walker random and a high degree was proposed. Simulation results show that the strategy can significantly reduce the average number of search steps, so as to effectively improve the search speed and efficiency. Lianming Zhang, Aoyuan Peng, and Jianping Yu Copyright © 2013 Lianming Zhang et al. All rights reserved. Multiple-Feature Extracting Modules Based Leak Mining System Design Tue, 17 Dec 2013 11:34:45 +0000 http://www.hindawi.com/journals/tswj/2013/704865/ Over the years, human dependence on the Internet has increased dramatically. A large amount of information is placed on the Internet and retrieved from it daily, which makes web security in terms of online information a major concern. In recent years, the most problematic issues in web security have been e-mail address leakage and SQL injection attacks. There are many possible causes of information leakage, such as inadequate precautions during the programming process, which lead to the leakage of e-mail addresses entered online or insufficient protection of database information, a loophole that enables malicious users to steal online content. In this paper, we implement a crawler mining system that is equipped with SQL injection vulnerability detection, by means of an algorithm developed for the web crawler. In addition, we analyze portal sites of the governments of various countries or regions in order to investigate the information leaking status of each site. Subsequently, we analyze the database structure and content of each site, using the data collected. Thus, we make use of practical verification in order to focus on information security and privacy through black-box testing. Ying-Chiang Cho and Jen-Yi Pan Copyright © 2013 Ying-Chiang Cho and Jen-Yi Pan. All rights reserved. Joint Estimation of 2D-DOA and Frequency Based on Space-Time Matrix and Conformal Array Sun, 15 Dec 2013 14:00:07 +0000 http://www.hindawi.com/journals/tswj/2013/463828/ Each element in the conformal array has a different pattern, which leads to the performance deterioration of the conventional high resolution direction-of-arrival (DOA) algorithms. In this paper, a joint frequency and two-dimension DOA (2D-DOA) estimation algorithm for conformal array are proposed. The delay correlation function is used to suppress noise. Both spatial and time sampling are utilized to construct the spatial-time matrix. The frequency and 2D-DOA estimation are accomplished based on parallel factor (PARAFAC) analysis without spectral peak searching and parameter pairing. The proposed algorithm needs only four guiding elements with precise positions to estimate frequency and 2D-DOA. Other instrumental elements can be arranged flexibly on the surface of the carrier. Simulation results demonstrate the effectiveness of the proposed algorithm. Liang-Tian Wan, Lu-Tao Liu, Wei-Jian Si, and Zuo-Xi Tian Copyright © 2013 Liang-Tian Wan et al. All rights reserved. An MBS-Assisted Femtocell Transmit Power Control Scheme with Mobile User QoS Guarantee in 2-Tier Heterogeneous Femtocell Networks Wed, 11 Dec 2013 08:46:59 +0000 http://www.hindawi.com/journals/tswj/2013/403978/ This study investigates how to adjust the transmit power of femto base station (FBS) to mitigate interference problems between the FBSs and mobile users (MUs) in the 2-tier heterogeneous femtocell networks. A common baseline of deploying the FBS to increase the indoor access bandwidth requires that the FBS operation will not affect outdoor MUs operation with their quality-of-service (QoS) requirements. To tackle this technical problem, an FBS transmit power adjustment (FTPA) algorithm is proposed to adjust the FBS transmit power (FTP) to avoid unwanted cochannel interference (CCI) with the neighboring MUs in downlink transmission. FTPA reduces the FTP to serve its femto users (FUs) according to the QoS requirements of the nearest neighboring MUs to the FBS so that the MU QoS requirement is guaranteed. Simulation results demonstrate that FTPA can achieve a low MU outage probability as well as serve FUs without violating the MU QoS requirements. Simulation results also reveal that FTPA has better performance on voice and video services which are the major trend of future multimedia communication in the NGN. Jenhui Chen, Chih-Cheng Yang, and Shiann-Tsong Sheu Copyright © 2013 Jenhui Chen et al. All rights reserved. Multiantenna Relay Beamforming Design for QoS Discrimination in Two-Way Relay Networks Tue, 10 Dec 2013 13:20:48 +0000 http://www.hindawi.com/journals/tswj/2013/306423/ This paper investigates the relay beamforming design for quality of service (QoS) discrimination in two-way relay networks. The purpose is to keep legitimate two-way relay users exchange their information via a helping multiantenna relay with QoS guarantee while avoiding the exchanged information overhearing by unauthorized receiver. To this end, we propose a physical layer method, where the relay beamforming is jointly designed with artificial noise (AN) which is used to interfere in the unauthorized user’s reception. We formulate the joint beamforming and AN (BFA) design into an optimization problem such that the received signal-to-interference-ratio (SINR) at the two legitimate users is over a predefined QoS threshold while limiting the received SINR at the unauthorized user which is under a certain secure threshold. The objective of the optimization problem is to seek the optimal AN and beamforming vectors to minimize the total power consumed by the relay node. Since the optimization problem is nonconvex, we solve it by using semidefinite program (SDP) relaxation. For comparison, we also study the optimal relay beamforming without using AN (BFO) under the same QoS discrimination constraints. Simulation results show that both the proposed BFA and BFO can achieve the QoS discrimination of the two-way transmission. However, the proposed BFA yields significant power savings and lower infeasible rates compared with the BFO method. Ke Xiong, Yu Zhang, Dandan Li, Chih-Yung Chang, and Zhangdui Zhong Copyright © 2013 Ke Xiong et al. All rights reserved. Peering Strategic Game Models for Interdependent ISPs in Content Centric Internet Thu, 05 Dec 2013 10:51:28 +0000 http://www.hindawi.com/journals/tswj/2013/380265/ Emergent content-oriented networks prompt Internet service providers (ISPs) to evolve and take major responsibility for content delivery. Numerous content items and varying content popularities motivate interdependence between peering ISPs to elaborate their content caching and sharing strategies. In this paper, we propose the concept of peering for content exchange between interdependent ISPs in content centric Internet to minimize content delivery cost by a proper peering strategy. We model four peering strategic games to formulate four types of peering relationships between ISPs who are characterized by varying degrees of cooperative willingness from egoism to altruism and interconnected as profit-individuals or profit-coalition. Simulation results show the price of anarchy (PoA) and communication cost in the four games to validate that ISPs should decide their peering strategies by balancing intradomain content demand and interdomain peering relations for an optimal cost of content delivery. Jia Zhao, Jianfeng Guan, Changqiao Xu, Wei Su, and Hongke Zhang Copyright © 2013 Jia Zhao et al. All rights reserved. Dual-Band Operation of a Microstrip Patch Antenna on a Duroid 5870 Substrate for Ku- and K-Bands Thu, 05 Dec 2013 10:21:40 +0000 http://www.hindawi.com/journals/tswj/2013/378420/ The dual-band operation of a microstrip patch antenna on a Duroid 5870 substrate for Ku- and K-bands is presented. The fabrication of the proposed antenna is performed with slots and a Duroid 5870 dielectric substrate and is excited by a 50 Ω microstrip transmission line. A high-frequency structural simulator (HFSS) is used which is based on the finite element method (FEM) in this research. The measured impedance bandwidth (2 : 1 VSWR) achieved is 1.07 GHz (15.93 GHz–14.86 GHz) on the lower band and 0.94 GHz (20.67–19.73 GHz) on the upper band. A stable omnidirectional radiation pattern is observed in the operating frequency band. The proposed prototype antenna behavior is discussed in terms of the comparisons of the measured and simulated results. M. M. Islam, M. T. Islam, and M. R. I. Faruque Copyright © 2013 M. M. Islam et al. All rights reserved. The Robustness Analysis of Wireless Sensor Networks under Uncertain Interference Sat, 30 Nov 2013 10:55:57 +0000 http://www.hindawi.com/journals/tswj/2013/185970/ Based on the complex network theory, robustness analysis of condition monitoring wireless sensor network under uncertain interference is present. In the evolution of the topology of sensor networks, the density weighted algebraic connectivity is taken into account, and the phenomenon of removing and repairing the link and node in the network is discussed. Numerical simulation is conducted to explore algebraic connectivity characteristics and network robustness performance. It is found that nodes density has the effect on algebraic connectivity distribution in the random graph model; high density nodes carry more connections, use more throughputs, and may be more unreliable. Moreover, the results show that, when network should be more error tolerant or robust by repairing nodes or adding new nodes, the network should be better clustered in median and high scale wireless sensor networks and be meshing topology in small scale networks. Changjian Deng Copyright © 2013 Changjian Deng. All rights reserved. On the Relationship between Multicast/Broadcast Throughput and Resource Utilizations in Wireless Mesh Networks Tue, 19 Nov 2013 10:06:18 +0000 http://www.hindawi.com/journals/tswj/2013/794549/ This paper deals with the problem of multicast/broadcast throughput in multi-channel multi-radio wireless mesh networks that suffer from the resource constraints. We provide a formulation to capture the utilization of the network resources and derive analytical relationships for the network’s throughput in terms of the node utilization, the channel utilization, and the number of transmissions. Our model relies on the on-demand quality of service multicast/broadcast sessions, where each admitted session creates a unique tree with a specific bandwidth. As an advantage, the derived relationships are independent of the type of tree built for each session and can be used for different protocols. The proposed formulation considers the channel assignment strategy and reflects both the wireless broadcast advantage and the interference constraint. We also offer a comprehensive discussion to evaluate the effects of load-balancing and number of transmissions on the network’s throughput. Numerical results confirm the accuracy of the presented analysis. Avid Avokh, Ghasem Mirjalily, Jamshid Abouei, and Shahrokh Valaee Copyright © 2013 Avid Avokh et al. All rights reserved. On the Accurate Identification of Network Paths Having a Common Bottleneck Tue, 12 Nov 2013 16:08:10 +0000 http://www.hindawi.com/journals/tswj/2013/890578/ We present a new mechanism for detecting shared bottlenecks between end-to-end paths in a network. Our mechanism, which only needs one-way delays from endpoints as an input, is based on the well-known linear algebraic approach: singular value decomposition (SVD). Clusters of flows which share a bottleneck are extracted from SVD results by applying an outlier detection method. Simulations with varying topologies and different network conditions show the high accuracy of our technique. Muhammad Murtaza Yousaf and Michael Welzl Copyright © 2013 Muhammad Murtaza Yousaf and Michael Welzl. All rights reserved. A Relation Routing Scheme for Distributed Semantic Media Query Mon, 11 Nov 2013 11:18:24 +0000 http://www.hindawi.com/journals/tswj/2013/915963/ Performing complex semantic queries over large-scale distributed media contents is a challenging task for rich media applications. The dynamics and openness of data sources make it uneasy to realize a query scheme that simultaneously achieves precision, scalability, and reliability. In this paper, a novel relation routing scheme (RRS) is proposed by renovating the routing model of Content Centric Network (CCN) for directly querying large-scale semantic media content. By using proper query model and routing mechanism, semantic queries with complex relation constrains from users can be guided towards potential media sources through semantic guider nodes. The scattered and fragmented query results can be integrated on their way back for semantic needs or to avoid duplication. Several new techniques, such as semantic-based naming, incomplete response avoidance, timeout checking, and semantic integration, are developed in this paper to improve the accuracy, efficiency, and practicality of the proposed approach. Both analytical and experimental results show that the proposed scheme is a promising and effective solution for complex semantic queries and integration over large-scale networks. Zhuhua Liao, Guoqiang Zhang, Aiping Yi, Guoqing Zhang, and Wei Liang Copyright © 2013 Zhuhua Liao et al. All rights reserved. Design and Analysis of a Dynamic Mobility Management Scheme for Wireless Mesh Network Thu, 07 Nov 2013 14:42:05 +0000 http://www.hindawi.com/journals/tswj/2013/656259/ Seamless mobility management of the mesh clients (MCs) in wireless mesh network (WMN) has drawn a lot of attention from the research community. A number of mobility management schemes such as mesh network with mobility management (MEMO), mesh mobility management (), and wireless mesh mobility management (WMM) have been proposed. The common problem with these schemes is that they impose uniform criteria on all the MCs for sending route update message irrespective of their distinct characteristics. This paper proposes a session-to-mobility ratio (SMR) based dynamic mobility management scheme for handling both internet and intranet traffic. To reduce the total communication cost, this scheme considers each MC’s session and mobility characteristics by dynamically determining optimal threshold SMR value for each MC. A numerical analysis of the proposed scheme has been carried out. Comparison with other schemes shows that the proposed scheme outperforms MEMO, , and WMM with respect to total cost. Abhishek Majumder and Sudipta Roy Copyright © 2013 Abhishek Majumder and Sudipta Roy. All rights reserved. Amplify-and-Forward Cooperative Diversity for Green UWB-Based WBSNs Wed, 06 Nov 2013 09:41:18 +0000 http://www.hindawi.com/journals/tswj/2013/785840/ This paper proposes a novel green cooperative diversity technique based on suboptimal template-based ultra-wideband (UWB) wireless body sensor networks (WBSNs) using amplify-and-forward (AF) relays. In addition, it analyzes the bit-error-rate (BER) performance of the proposed nodes. The analysis is based on the moment-generating function (MGF) of the total signal-to-noise ratio (SNR) at the destination. It also provides an approximate value for the total SNR. The analysis studies the performance of equally correlated binary pulse position modulation (EC-BPPM) assuming the sinusoidal and square suboptimal template pulses. Numerical results are provided for the performance evaluation of optimal and suboptimal template-based nodes with and without relay cooperation. Results show that one relay node provides ~23 dB performance enhancement at BER, which mitigates the effect of the nondesirable non-line-of-sight (NLOS) links in WBSNs. Heba Shaban and Mohamad Abou El-Nasr Copyright © 2013 Heba Shaban and Mohamad Abou El-Nasr. All rights reserved. Deterministic Sensing Matrices in Compressive Sensing: A Survey Tue, 05 Nov 2013 14:57:39 +0000 http://www.hindawi.com/journals/tswj/2013/192795/ Compressive sensing is a sampling method which provides a new approach to efficient signal compression and recovery by exploiting the fact that a sparse signal can be suitably reconstructed from very few measurements. One of the most concerns in compressive sensing is the construction of the sensing matrices. While random sensing matrices have been widely studied, only a few deterministic sensing matrices have been considered. These matrices are highly desirable on structure which allows fast implementation with reduced storage requirements. In this paper, a survey of deterministic sensing matrices for compressive sensing is presented. We introduce a basic problem in compressive sensing and some disadvantage of the random sensing matrices. Some recent results on construction of the deterministic sensing matrices are discussed. Thu L. N. Nguyen and Yoan Shin Copyright © 2013 Thu L. N. Nguyen and Yoan Shin. All rights reserved. Compact Ultra Wide Band Microstrip Bandpass Filter Based on Multiple-Mode Resonator and Modified Complementary Split Ring Resonator Mon, 04 Nov 2013 11:38:43 +0000 http://www.hindawi.com/journals/tswj/2013/402539/ A new class of broadband microstrip filters for Ultra Wide Band (UWB) applications is proposed. In the design, different stages of parallel-coupled microstrip line and other stages with a Modified Complementary Split Ring Resonator (MCSRR)—a concept proposed here for the first time—are adjusted to obtain the desired response with broadband, sharp rejection, low insertion loss, and low return loss. Full wave simulation results as well as measurement results from fabricated prototypes are presented, showing good agreement. The proposed technique offers a new alternative to implement low-cost high-performance filter devices, applicable to a wide range of communication systems. J. Antonio Marcotegui, Jesús Miguel Illescas, Aritz Estevez, and Francisco Falcone Copyright © 2013 J. Antonio Marcotegui et al. All rights reserved. Smart Caching Based on Mobile Agent of Power WebGIS Platform Mon, 28 Oct 2013 14:58:08 +0000 http://www.hindawi.com/journals/tswj/2013/757182/ Power information construction is developing towards intensive, platform, distributed direction with the expansion of power grid and improvement of information technology. In order to meet the trend, power WebGIS was designed and developed. In this paper, we first discuss the architecture and functionality of power WebGIS, and then we study caching technology in detail, which contains dynamic display cache model, caching structure based on mobile agent, and cache data model. We have designed experiments of different data capacity to contrast performance between WebGIS with the proposed caching model and traditional WebGIS. The experimental results showed that, with the same hardware environment, the response time of WebGIS with and without caching model increased as data capacity growing, while the larger the data was, the higher the performance of WebGIS with proposed caching model improved. Xiaohui Wang, Kehe Wu, and Fei Chen Copyright © 2013 Xiaohui Wang et al. All rights reserved. Service Differentiated and Adaptive CSMA/CA over IEEE 802.15.4 for Cyber-Physical Systems Wed, 23 Oct 2013 18:47:12 +0000 http://www.hindawi.com/journals/tswj/2013/947808/ Cyber-Physical Systems (CPS) that collect, exchange, manage information, and coordinate actions are an integral part of the Smart Grid. In addition, Quality of Service (QoS) provisioning in CPS, especially in the wireless sensor/actuator networks, plays an essential role in Smart Grid applications. IEEE 802.15.4, which is one of the most widely used communication protocols in this area, still needs to be improved to meet multiple QoS requirements. This is because IEEE 802.15.4 slotted Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) employs static parameter configuration without supporting differentiated services and network self-adaptivity. To address this issue, this paper proposes a priority-based Service Differentiated and Adaptive CSMA/CA (SDA-CSMA/CA) algorithm to provide differentiated QoS for various Smart Grid applications as well as dynamically initialize backoff exponent according to traffic conditions. Simulation results demonstrate that the proposed SDA-CSMA/CA scheme significantly outperforms the IEEE 802.15.4 slotted CSMA/CA in terms of effective data rate, packet loss rate, and average delay. Feng Xia, Jie Li, Ruonan Hao, Xiangjie Kong, and Ruixia Gao Copyright © 2013 Feng Xia et al. All rights reserved. Extending Stochastic Network Calculus to Loss Analysis Sun, 20 Oct 2013 13:09:04 +0000 http://www.hindawi.com/journals/tswj/2013/918565/ Loss is an important parameter of Quality of Service (QoS). Though stochastic network calculus is a very useful tool for performance evaluation of computer networks, existing studies on stochastic service guarantees mainly focused on the delay and backlog. Some efforts have been made to analyse loss by deterministic network calculus, but there are few results to extend stochastic network calculus for loss analysis. In this paper, we introduce a new parameter named loss factor into stochastic network calculus and then derive the loss bound through the existing arrival curve and service curve via this parameter. We then prove that our result is suitable for the networks with multiple input flows. Simulations show the impact of buffer size, arrival traffic, and service on the loss factor. Chao Luo, Li Yu, and Jun Zheng Copyright © 2013 Chao Luo et al. All rights reserved. Power and Time Slot Allocation in Cognitive Relay Networks Using Particle Swarm Optimization Tue, 08 Oct 2013 11:46:37 +0000 http://www.hindawi.com/journals/tswj/2013/424162/ The two main problems in cognitive radio networks are power and time slot allocation problems which require a precise analysis and guarantee the quality of service in both the primary and secondary users. In this paper, these two problems are considered and a method is proposed to solve the resulting optimization problem. Our proposed method provides an improved performance in solving the constrained nonlinear multiobject optimization for the power control and beamforming in order to reach the maximum capacity and proper adaption of time slots, and as a result a new scheme for joint power and time slot allocation in cognitive relay networks is proposed. We adopt space diversity access as the secondary users access scheme and divide the time between multiple secondary users according to their contribution to primary user’s transmission. Helping primary users provides more opportunities for secondary users to access the channel since the primary users can release the channel sooner. In contrast, primary network leases portion of channel access time to the secondary users for their transmission using particle swarm optimization (PSO). Numerical studies show good performance of the proposed scheme with a dynamic cost function in a nonstationary environment. Pouya Derakhshan-Barjoei, Gholamreza Dadashzadeh, Farbod Razzazi, and S. Mohammad Razavizadeh Copyright © 2013 Pouya Derakhshan-Barjoei et al. All rights reserved. A CPW-Fed Circular Wide-Slot UWB Antenna with Wide Tunable and Flexible Reconfigurable Dual Notch Bands Thu, 03 Oct 2013 15:37:47 +0000 http://www.hindawi.com/journals/tswj/2013/402914/ A coplanar waveguide (CPW)-fed circular slot antenna with wide tunable dual band-notched function and frequency reconfigurable characteristic is designed, and its performance is verified experimentally for ultra-wideband (UWB) communication applications. The dual band-notched function is achieved by using a T-shaped stepped impedance resonator (T-SIR) inserted inside the circular ring radiation patch and by etching a parallel stub loaded resonator (PSLR) in the CPW transmission line, while the wide tunable bands can be implemented by adjusting the dimensions of the T-SIR and the PSLR. The notch band reconfigurable characteristic is realized by integrating three switches into the T-SIR and the PSLR. The numerical and experimental results show that the proposed antenna has a wide bandwidth ranging from 2.7 GHz to 12 GHz with voltage standing wave ratio (VSWR) less than 2, except for the two notch bands operating at 3.8–5.9 GHz and 7.7–9.2 GHz, respectively. In addition, the proposed antenna has been optimized to a compact size and can provide omnidirectional radiation patterns, which are suitable for UWB communication applications. Yingsong Li, Wenxing Li, and Qiubo Ye Copyright © 2013 Yingsong Li et al. All rights reserved. A Hybrid OFDM-TDM Architecture with Decentralized Dynamic Bandwidth Allocation for PONs Mon, 30 Sep 2013 13:32:42 +0000 http://www.hindawi.com/journals/tswj/2013/561984/ One of the major challenges of passive optical networks is to achieve a fair arbitration mechanism that will prevent possible collisions from occurring at the upstream channel when multiple users attempt to access the common fiber at the same time. Therefore, in this study we mainly focus on fair bandwidth allocation among users, and present a hybrid Orthogonal Frequency Division Multiplexed/Time Division Multiplexed architecture with a dynamic bandwidth allocation scheme that provides satisfying service qualities to the users depending on their varying bandwidth requirements. Unnecessary delays in centralized schemes occurring during bandwidth assignment stage are eliminated by utilizing a decentralized approach. Instead of sending bandwidth demands to the optical line terminal (OLT) which is the only competent authority, each optical network unit (ONU) runs the same bandwidth demand determination algorithm. ONUs inform each other via signaling channel about the status of their queues. This information is fed to the bandwidth determination algorithm which is run by each ONU in a distributed manner. Furthermore, Light Load Penalty, which is a phenomenon in optical communications, is mitigated by limiting the amount of bandwidth that an ONU can demand. Taner Cevik Copyright © 2013 Taner Cevik. All rights reserved. Energy-Efficient Data Gathering Scheme Based on Broadcast Transmissions in Wireless Sensor Networks Sat, 24 Aug 2013 11:30:03 +0000 http://www.hindawi.com/journals/tswj/2013/402930/ Improving energy efficiency is the most important challenge in wireless sensor networks. Because sensing information is correlated in many sensor network applications, some previous works have proposed ideas that reduce the energy consumption of the network by exploiting the spatial correlation between sensed information. In this paper, we propose a distributed data compression framework that exploits the broadcasting characteristic of the wireless medium to improve energy efficiency. We analyze the performance of the proposed framework numerically and compare it with the performance of previous works using simulation. The proposed scheme performs better when the sensing information is correlated. Soobin Lee and Howon Lee Copyright © 2013 Soobin Lee and Howon Lee. All rights reserved. Presence Service in IMS Tue, 23 Jul 2013 09:28:48 +0000 http://www.hindawi.com/journals/tswj/2013/606790/ This paper describes the presence service, which is located in the IP multimedia subsystem. This service allows making many applications for different groups of people. The paper describes differences between a network without the service and with the service. The biggest change is an increased number of transmitted messages. The presence uses some part of the IP multimedia subsystem control layer, which is shown in communication between the user and the server. The paper deals with the number of generated messages depending on the behaviour of the users. This is described by a mathematical model using discrete Markov chains. David Petras, Ivan Baronak, and Erik Chromy Copyright © 2013 David Petras et al. All rights reserved. Cascadable Current-Mode First-Order All-Pass Filter Based on Minimal Components Thu, 13 Jun 2013 14:27:43 +0000 http://www.hindawi.com/journals/tswj/2013/859784/ A novel current-mode first-order all-pass filter with low input and high output impedance feature is presented. The circuit realization employs a single dual-X-second-generation current conveyor, one grounded capacitor, and one grounded resistor, which is a minimum component realization. The theoretical results are verified using PSPICE simulation program with TSMC 0.35 μm CMOS process parameters. Jitendra Mohan and Sudhanshu Maheshwari Copyright © 2013 Jitendra Mohan and Sudhanshu Maheshwari. All rights reserved. The System Power Control Unit Based on the On-Chip Wireless Communication System Thu, 30 May 2013 14:09:46 +0000 http://www.hindawi.com/journals/tswj/2013/939254/ Currently, the on-chip wireless communication system (OWCS) includes 2nd-generation (2G), 3rd-generation (3G), and long-term evolution (LTE) communication subsystems. To improve the power consumption of OWCS, a typical architecture design of system power control unit (SPCU) is given in this paper, which can not only make a 2G, a 3G, and an LTE subsystems enter sleep mode, but it can also wake them up from sleep mode via the interrupt. During the sleep mode period, either the real-time sleep timer or the global system for mobile (GSM) communication sleep timer can be used individually to arouse the corresponding subsystem. Compared to previous sole voltage supplies on the OWCS, a 2G, a 3G, or an LTE subsystem can be independently configured with three different voltages and frequencies in normal work mode. In the meantime, the voltage supply monitor, which is an important part in the SPCU, can significantly guard the voltage of OWCS in real time. Finally, the SPCU may implement dynamic voltage and frequency scaling (DVFS) for a 2G, a 3G, or an LTE subsystem, which is automatically accomplished by the hardware. Tiefeng Li, Caiwen Ma, and WenHua Li Copyright © 2013 Tiefeng Li et al. All rights reserved. Deadline-Aware Energy-Efficient Query Scheduling in Wireless Sensor Networks with Mobile Sink Wed, 29 May 2013 11:19:17 +0000 http://www.hindawi.com/journals/tswj/2013/834653/ Mobile sinks are proposed to save sensor energy spent for multihop communication in transferring data to a base station (sink) in Wireless Sensor Networks. Due to relative low speed of mobile sinks, these approaches are mostly suitable for delay-tolerant applications. In this paper, we study the design of a query scheduling algorithm for query-based data gathering applications using mobile sinks. However, these kinds of applications are sensitive to delays due to specified query deadlines. Thus, the proposed scheduling algorithm aims to minimize the number of missed deadlines while keeping the level of energy consumption at the minimum. Murat Karakaya Copyright © 2013 Murat Karakaya. All rights reserved. An Efficient and Secure Certificateless Authentication Protocol for Healthcare System on Wireless Medical Sensor Networks Sun, 21 Apr 2013 11:50:52 +0000 http://www.hindawi.com/journals/tswj/2013/761240/ Sensor networks have opened up new opportunities in healthcare systems, which can transmit patient’s condition to health professional’s hand-held devices in time. The patient’s physiological signals are very sensitive and the networks are extremely vulnerable to many attacks. It must be ensured that patient’s privacy is not exposed to unauthorized entities. Therefore, the control of access to healthcare systems has become a crucial challenge. An efficient and secure authentication protocol will thus be needed in wireless medical sensor networks. In this paper, we propose a certificateless authentication scheme without bilinear pairing while providing patient anonymity. Compared with other related protocols, the proposed scheme needs less computation and communication cost and preserves stronger security. Our performance evaluations show that this protocol is more practical for healthcare system in wireless medical sensor networks. Rui Guo, Qiaoyan Wen, Zhengping Jin, and Hua Zhang Copyright © 2013 Rui Guo et al. All rights reserved. Many-to-Many Multicast Routing Schemes under a Fixed Topology Mon, 25 Mar 2013 13:21:21 +0000 http://www.hindawi.com/journals/tswj/2013/718152/ Many-to-many multicast routing can be extensively applied in computer or communication networks supporting various continuous multimedia applications. The paper focuses on the case where all users share a common communication channel while each user is both a sender and a receiver of messages in multicasting as well as an end user. In this case, the multicast tree appears as a terminal Steiner tree (TeST). The problem of finding a TeST with a quality-of-service (QoS) optimization is frequently NP-hard. However, we discover that it is a good idea to find a many-to-many multicast tree with QoS optimization under a fixed topology. In this paper, we are concerned with three kinds of QoS optimization objectives of multicast tree, that is, the minimum cost, minimum diameter, and maximum reliability. All of three optimization problems are distributed into two types, the centralized and decentralized version. This paper uses the dynamic programming method to devise an exact algorithm, respectively, for the centralized and decentralized versions of each optimization problem. Wei Ding, Hongfa Wang, and Xuerui Wei Copyright © 2013 Wei Ding et al. All rights reserved. Nonlinear Demodulation and Channel Coding in EBPSK Scheme Tue, 20 Nov 2012 08:27:12 +0000 http://www.hindawi.com/journals/tswj/2012/180469/ The extended binary phase shift keying (EBPSK) is an efficient modulation technique, and a special impacting filter (SIF) is used in its demodulator to improve the bit error rate (BER) performance. However, the conventional threshold decision cannot achieve the optimum performance, and the SIF brings more difficulty in obtaining the posterior probability for LDPC decoding. In this paper, we concentrate not only on reducing the BER of demodulation, but also on providing accurate posterior probability estimates (PPEs). A new approach for the nonlinear demodulation based on the support vector machine (SVM) classifier is introduced. The SVM method which selects only a few sampling points from the filter output was used for getting PPEs. The simulation results show that the accurate posterior probability can be obtained with this method and the BER performance can be improved significantly by applying LDPC codes. Moreover, we analyzed the effect of getting the posterior probability with different methods and different sampling rates. We show that there are more advantages of the SVM method under bad condition and it is less sensitive to the sampling rate than other methods. Thus, SVM is an effective method for EBPSK demodulation and getting posterior probability for LDPC decoding. Xianqing Chen and Lenan Wu Copyright © 2012 Xianqing Chen and Lenan Wu. All rights reserved.