http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2013 , Hindawi Publishing Corporation . All rights reserved. Thu, 16 May 2013 16:01:13 +0000 http://www.hindawi.com/journals/jcnc/2013/497157/ Multimedia sensor networks for real-time applications have strict constraints on delay, packet loss, and energy consumption requirements. For example, video streaming in a disaster-management scenario requires careful handling to ensure that the end-to-end delay is within the acceptable range and the video is received properly without any distortion. The failure to transmit a video stream effectively occurs for many reasons, including sensor function limitations, excessive power consumption, and a lack of routing reliability. We propose a novel mathematical model for quality of service (QoS) route determination that enables a sensor to determine the optimal path for minimising resource use while satisfying the required QoS constraints. The proposed mathematical model uses the Lagrangian relaxation mixed integer programming technique to define critical parameters and appropriate objective functions for controlling the adaptive QoS constrained route discovery process. Performance trade-offs between QoS requirements and energy efficiency were simulated using the LINGO mathematical programming language. The proposed approach significantly improves the network lifetime, while reducing energy consumption and decreasing average end-to-end delays within the sensor network via optimised resource sharing in intermediate nodes compared with existing routing algorithms. Mohammed Zaki Hasan and Tat-Chee Wan Copyright © 2013 Mohammed Zaki Hasan and Tat-Chee Wan. All rights reserved. Tue, 23 Apr 2013 16:59:03 +0000 http://www.hindawi.com/journals/jcnc/2013/752363/ The high bandwidth demand of Internet applications has recently driven the need of increasing the residential download speed. A practical solution to the problem is to aggregate the bandwidth of 802.11 access points (APs) backhauls in range. Since 802.11 devices are usually single radio, the communication to APs on different radio channels requires a time-division multiple access (TDMA) policy at the client station. With an in-depth experimental analysis and a customized 802.11 driver, in this paper, we show that the usage of multi-AP TDMA policy may cause degradation of the TCP throughput and an underutilization of the AP backhauls. We then introduce a simple analytical model that accurately predicts the TCP round-trip time (RTT) with a multi-AP TDMA policy and propose a resource allocation algorithm to reduce the observed TCP RTT with a very low computational cost. Our proposed scheme runs locally at the client station and improves the aggregate throughput up to 1.5 times compared to state-of-the-art allocations. We finally show that the throughput achieved by our algorithm is very close to the theoretical upper bound in key simulation scenarios. Domenico Giustiniano, Eduard Goma, Alberto Lopez Toledo, and George Athanasiou Copyright © 2013 Domenico Giustiniano et al. All rights reserved. Thu, 18 Apr 2013 14:12:31 +0000 http://www.hindawi.com/journals/jcnc/2013/597461/ Due to the dynamic nature of mobile ad hoc network (MANET), the quality of service (QoS) requires several improvements. The present papercomeswithin the framework of research to optimize QoS in MANET. In this paper, we propose a novel version of OLSR based on the clustering approach which is inspired from Lin and Chu heuristic and adapted to beimplemented inOLSR. We studied its stability and we compared its performances to those of standard OLSR. The metrics we used in evaluating network performances were average end-to-end delay, control routing overhead, and packet delivery ratio. Experimental results show that our alternative significantly reduces the traffic reserved to monitoring the network, which positively influences other performances such as throughput, delay, and loss. Ali Choukri, Ahmed Habbani, and Mohamed El Koutbi Copyright © 2013 Ali Choukri et al. All rights reserved. Mon, 15 Apr 2013 11:23:06 +0000 http://www.hindawi.com/journals/jcnc/2013/412491/ Scalable video coding allows an efficient provision of video services at different quality levels with different energy demands. According to the specific type of service and network scenario, end users and/or operators may decide to choose among different energy versus quality combinations. In order to deal with the resulting trade-off, in this paper we analyze the number of video layers that are worth to be received taking into account the energy constraints. A single-objective optimization is proposed based on dynamically selecting the number of layers, which is able to minimize the energy consumption with the constraint of a minimal quality threshold to be reached. However, this approach cannot reflect the fact that the same increment of energy consumption may result in different increments of visual quality. Thus, a multiobjective optimization is proposed and a utility function is defined in order to weight the energy consumption and the visual quality criteria. Finally, since the optimization solving mechanism is computationally expensive to be implemented in mobile devices, a heuristic algorithm is proposed. This way, significant energy consumption reduction will be achieved while keeping reasonable quality levels. Fidel Liberal, Ianire Taboada, and Jose-Oscar Fajardo Copyright © 2013 Fidel Liberal et al. All rights reserved. Wed, 03 Apr 2013 11:25:43 +0000 http://www.hindawi.com/journals/jcnc/2013/351435/ We propose methods for selecting the modelling parameters of H.263-quantized video traffic under two different encoding scenarios. For videos encoded with a constant quantization step (unconstrained), we conclude that a two-parameter power relation holds between the exhibited video bit rate and the quantizer value and that the autocorrelation decay rate remains constant for all cases. On the basis of these results, we propose a generic method for estimating the modelling parameters of unconstrained traffic by means of measuring the statistics of the single “raw” video trace. For rate-controlled video (constrained), we propose an approximate method based on the adjustment of the “shape” parameter of the counterpart—with respect to rate—unconstrained video trace. The convergence of the constructed models is assessed via q-q plots and queuing simulations. On the assumption that the popular MPEG-4 encoders like XVID, DIVX usually employ identical H.263 quantization and rate control schemes, it is expected that the results of this paper also hold for the MPEG-4 part 2 family. A. Drigas and S. Kouremenos Copyright © 2013 A. Drigas and S. Kouremenos. All rights reserved. Wed, 03 Apr 2013 08:35:29 +0000 http://www.hindawi.com/journals/jcnc/2013/176217/ The popularity of smartphones and mobile applications has experienced a considerable growth during the recent years, and this growth is expected to continue in the future. Since smartphones have only very limited energy resources, battery efficiency is one of the determining factors for a good user experience. Therefore, some smartphones tear down connections to the mobile network soon after a completed data transmission to reduce the power consumption of their transmission unit. However, frequent connection reestablishments caused by apps which send or receive small amounts of data often lead to a heavy signalling load within the mobile network. One of the major contributions of this paper is the investigation of the resulting tradeoff between energy consumption at the smartphone and the generated signalling traffic in the mobile network. We explain that this tradeoff can be controlled by the connection release timeout and study the impact of this parameter for a number of popular apps that cover a wide range of traffic characteristics in terms of bandwidth requirements and resulting signalling traffic. Finally, we study the impact of the timer settings on Quality of Experience (QoE) for web traffic. This is an important aspect since connection establishments not only lead to signalling traffic but also increase the load time of web pages. Christian Schwartz, Tobias Hoßfeld, Frank Lehrieder, and Phuoc Tran-Gia Copyright © 2013 Christian Schwartz et al. All rights reserved. Tue, 26 Mar 2013 11:55:36 +0000 http://www.hindawi.com/journals/jcnc/2013/134760/ The aim of this paper is to present an adaptive and cost-sensitive model to prevent security intrusions. In most automated intrusion response systems, response selection is performed locally based on current threat without using the knowledge of attacks history. Another challenge is that a group of responses are applied without any feedback mechanism to measure the response effect. We address these problems through retroactive-burst execution of responses and a Response Coordinator (RC) mechanism, the main contributions of this work. The retroactive-burst execution consists of several burst executions of responses with, at the end of each burst, a mechanism for measuring the effectiveness of the applied responses by the risk assessment component. The appropriate combination of responses must be considered for each burst execution to mitigate the progress of the attack without necessarily running the next round of responses, because of the impact on legitimate users. In the proposed model, there is a multilevel response mechanism. To indicate which level is appropriate to apply based on the retroactive-burst execution, we get help from a Response Coordinator mechanism. The applied responses can improve the health of Applications, Kernel, Local Services, Network Services, and Physical Status. Based on these indexes, the RC gives a general overview of an attacker’s goal in a distributed environment. Alireza Shameli-Sendi, Julien Desfossez, Michel Dagenais, and Masoume Jabbarifar Copyright © 2013 Alireza Shameli-Sendi et al. All rights reserved. Sat, 23 Mar 2013 15:00:32 +0000 http://www.hindawi.com/journals/jcnc/2013/165146/ With the move towards converged all-IP wireless network environments, managing end-user Quality of Experience (QoE) poses a challenging task, aimed at meeting high user expectations and requirements regarding reliable and cost-effective communication, access to any service, anytime and anywhere, and across multiple operator domains. In this paper, we give a survey of state-of-the-art research activities addressing the field of QoE management, focusing in particular on the domain of wireless networks and addressing three management aspects: QoE modeling, monitoring and measurement, and adaptation and optimization. Furthermore, we identify and discuss the key aspects and challenges that need to be considered when conducting research in this area. Sabina Baraković and Lea Skorin-Kapov Copyright © 2013 Sabina Baraković and Lea Skorin-Kapov. All rights reserved. Sun, 17 Mar 2013 08:08:58 +0000 http://www.hindawi.com/journals/jcnc/2013/528750/ Sergio Saponara, Agusti Solanas, Gildas Avoine, and Bruno Neri Copyright © 2013 Sergio Saponara et al. All rights reserved. Wed, 13 Mar 2013 18:07:10 +0000 http://www.hindawi.com/journals/jcnc/2013/781620/ Chronic heart failure (CHF) is among the major causes of hospitalization for elderly citizens. Its considerable impact on patient quality of life, the resources congestion, and the related costs can be efficiently mitigated using remote wireless biosensors networks placed at patient home, able to communicate in secure way over the public Internet with the cardiology departmental Hospital Information System (HIS). In this way, physicians can monitor the situation of several patients at distance and quickly realize and act alterations in vital parameters. In this scenario, the Health@Home (H@H) platform is conceived. The pool of Bluetooth sensors enables patients to daily collect vital signs at home in noninvasive fashion. A home gateway receives and processes all signals before sending them to a server node in charge of interfacing with the usual HIS. The novel concept of operating protocol (OP) represents a list of actions, remotely configurable, that the domestic network has to follow (required measurements, transmissions, comparisons with personalized thresholds, etc.). The first medical tests on 30 patients (1 month) allowed to verify the model, both from the patient and the medical perspective. The main evaluation metrics were usability, flexibility, and reliability of the communication from sensors to HIS. Massimiliano Donati, Tony Bacchillone, Luca Fanucci, Sergio Saponara, and Filippo Costalli Copyright © 2013 Massimiliano Donati et al. All rights reserved. Wed, 13 Mar 2013 10:44:20 +0000 http://www.hindawi.com/journals/jcnc/2013/791097/ Node mobility in mobile ad hoc networks (MANETs) causes frequent route breakages and intermittent link stability. In this paper, we introduce a robust routing scheme, known as ad hoc on-demand multipath distance vector with dynamic path update (AOMDV-DPU), for delay-sensitive data transmission over MANET. The proposed scheme improves the AOMDV scheme by incorporating the following features: (i) a routing metric based on the combination of minimum hops and received signal strength indicator (RSSI) for discovery of reliable routes; (ii) a local path update mechanism which strengthens the route, reduces the route breakage frequency, and increases the route longevity; (iii) a keep alive mechanism for secondary route maintenance which enables smooth switching between routes and reduces the route discovery frequency; (iv) a packet salvaging scheme to improve packet delivery in the event of a route breakage; and (v) low HELLO packet overhead. The simulations are carried out in ns-2 for varying node speeds, number of sources, and traffic load conditions. Our AOMDV-DPU scheme achieves significantly higher throughput, lower delay, routing overhead, and route discovery frequency and latency compared to AOMDV. For H.264 compressed video traffic, AOMDV-DPU scheme achieves 3 dB or higher PSNR gain over AOMDV at both low and high node speeds. Sunil Kumar, Siddharth Khimsara, Kashyap Kambhatla, Kalyani Girivanesh, John D. Matyjas, and Michael Medley Copyright © 2013 Sunil Kumar et al. All rights reserved. Mon, 04 Mar 2013 10:38:36 +0000 http://www.hindawi.com/journals/jcnc/2013/897029/ Runhua Chen, Lingjia Liu, Krishna Sayana, and Hongxiang Li Copyright © 2013 Runhua Chen et al. All rights reserved. Mon, 11 Feb 2013 09:47:28 +0000 http://www.hindawi.com/journals/jcnc/2013/710275/ The rise of wireless applications based on RFID has brought up major concerns on privacy. Indeed nowadays, when such an application is deployed, informed customers yearn for guarantees that their privacy will not be threatened. One formal way to perform this task is to assess the privacy level of the RFID application with a model. However, if the chosen model does not reflect the assumptions and requirements of the analyzed application, it may misevaluate its privacy level. Therefore, selecting the most appropriate model among all the existing ones is not an easy task. This paper investigates the eight most well-known RFID privacy models and thoroughly examines their advantages and drawbacks in three steps. Firstly, five RFID authentication protocols are analyzed with these models. This discloses a main worry: although these protocols intuitively ensure different privacy levels, no model is able to accurately distinguish them. Secondly, these models are grouped according to their features (e.g., tag corruption ability). This classification reveals the most appropriate candidate model(s) to be used for a privacy analysis when one of these features is especially required. Furthermore, it points out that none of the models are comprehensive. Hence, some combinations of features may not match any model. Finally, the privacy properties of the eight models are compared in order to provide an overall view of their relations. This part highlights that no model globally outclasses the other ones. Considering the required properties of an application, the thorough study provided in this paper aims to assist system designers to choose the best suited model. Iwen Coisel and Tania Martin Copyright © 2013 Iwen Coisel and Tania Martin. All rights reserved. Tue, 29 Jan 2013 11:38:29 +0000 http://www.hindawi.com/journals/jcnc/2013/136213/ The fast growing popularity of smartphones and tablets enables us to use various intelligent mobile applications. As many of those applications require position information, smart mobile devices provide positioning methods such as Global Positioning System (GPS), WiFi-based positioning system (WPS), or Cell-ID-based positioning service. However, those positioning methods have different characteristics of energy-efficiency, accuracy, and service availability. In this paper, we present an Energy-Efficient Collaborative and Opportunistic Positioning System (ECOPS) for heterogeneous mobile devices. ECOPS facilitates a collaborative environment where many mobile devices can opportunistically receive position information over energy-efficient and prevalent WiFi, broadcasted from a few other devices in the communication range. The position-broadcasting devices in ECOPS have sufficient battery power and up-to-date location information obtained from accurate but energy-inefficient GPS. A position receiver in ECOPS estimates its location using a combination of methods including received signal strength indicators and 2D trilateration. Our field experiments show that ECOPS significantly reduces the total energy consumption of devices while achieving an acceptable level of location accuracy. ECOPS can be especially useful for unique resource scarce, infrastructureless, and mission critical scenarios such as battlefields, border patrol, mountaineering expeditions, and disaster area assistance. Kaustubh Dhondge, Hyungbae Park, Baek-Young Choi, and Sejun Song Copyright © 2013 Kaustubh Dhondge et al. All rights reserved. Sun, 27 Jan 2013 08:16:22 +0000 http://www.hindawi.com/journals/jcnc/2013/794202/ This work is about reducing energy consumption in the receiver chain by limiting the use of the equalizer. It is to make the radio receiver aware of its environment and able to take decision to turn on or off the equalizer according to its necessity or not. When the equalizer is off, the computational complexity is reduced and the rate of reduction depends on the percentage of time during which this component is disabled. In order to achieve this scenario of adapting the use of the equalizer, we need to develop a decision-making technique that provides the receiver with the capacities of awareness and adaptability to the state of its environment. For this, we improve a technique based on a statistical modeling of the environment by defining two metrics as channel quality indicators to evaluate the effect of the intersymbol interferences and the channel fading. The statistical modeling technique allows to take into account the impact of the uncertainties of the estimated metrics on the decision making. Salma Bourbia, Daniel Le Guennec, Jacques Palicot, Khaled Grati, and Adel Ghazel Copyright © 2013 Salma Bourbia et al. All rights reserved. Mon, 21 Jan 2013 10:50:38 +0000 http://www.hindawi.com/journals/jcnc/2013/302502/ Ondrej Krejcar, Peter Brida, and Stavros Kotsopoulos Copyright © 2013 Ondrej Krejcar et al. All rights reserved. Sun, 20 Jan 2013 14:35:10 +0000 http://www.hindawi.com/journals/jcnc/2013/984956/ In NDMA (network diversity multiple access), protocol-controlled retransmissions are used to create a virtual MIMO (multiple-input multiple-output) system, where collisions can be resolved via source separation. By using this retransmission diversity approach for collision resolution, NDMA is the family of random access protocols with the highest potential throughput. However, several issues remain open today in the modeling and design of this type of protocol, particularly in terms of dynamic stable performance and backlog delay. This paper attempts to partially fill this gap by proposing a Markov model for the study of the dynamic-stable performance of a symmetrical and non-blind NDMA protocol assisted by a multiple-antenna receiver. The model is useful in the study of stability aspects in terms of the backlog-user distribution and average backlog delay. It also allows for the investigation of the different states of the system and the transition probabilities between them. Unlike previous works, the proposed approach considers the imperfect estimation of the collision multiplicity, which is a crucial process to the performance of NDMA. The results suggest that NDMA improves not only the throughput performance over previous solutions, but also the average number of backlogged users, the average backlog delay and, in general, the stability of random access protocols. It is also shown that when multiuser detection conditions degrade, ALOHA-type backlog retransmission becomes relevant to the stable operation of NDMA. Ramiro Samano-Robles and Atilio Gameiro Copyright © 2013 Ramiro Samano-Robles and Atilio Gameiro. All rights reserved. Wed, 16 Jan 2013 16:17:50 +0000 http://www.hindawi.com/journals/jcnc/2013/970597/ Acquiring the snapshot of a distributed system helps gathering system related global state. In wireless sensor networks (WSNs), global state shows if a node is terminated or deadlock occurs along with many other situations which prevents a WSN from fully functioning. In this paper, we present a fully distributed snapshot acquisition algorithm adapted to tree topology wireless sensor networks (WSNs). Since snapshot acquisition is through control messages sent over highly lossy wireless channels and congested nodes, we enhanced the snapshot algorithm with a sink based reliability suit to achieve robustness. We analyzed the performance of the algorithm in terms of snapshot success ratio and response time in simulation and experimental small test bed environment. The results reveal that the proposed tailor made reliability model increases snapshot acquisition performance by a factor of seven and response time by a factor of two in a 30-node network. We have also shown that the proposed algorithm outperforms its counterparts in the specified network setting. Gamze Uslu, Kemal Cagri Serdaroglu, and Sebnem Baydere Copyright © 2013 Gamze Uslu et al. All rights reserved. Mon, 14 Jan 2013 14:49:43 +0000 http://www.hindawi.com/journals/jcnc/2013/392056/ This paper presents wireless sensing systems to increase safety and robustness in industrial process control, particularly in industrial machines for marble slab working. The process is performed by abrasive or cutting heads activated independently by the machine controller when the slab, transported on a conveyer belt, is under them. Current slab detection systems are based on electromechanical or optical devices at the machine entrance stage, suffering from deterioration and from the harsh environment. Slab displacement or break inside the machine due to the working stress may result in safety issues and damages to the conveyer belt due to incorrect driving of the working tools. The experimented contactless sensing techniques are based on four RFID and two capacitive sensing technologies and on customized hardware/software. The proposed solutions aim at overcoming some limitations of current state-of-the-art detection systems, allowing for reliable slab detection, outside and/or inside the machine, while maintaining low complexity and at the same time robustness to industrial harsh conditions. The proposed sensing devices may implement a wireless or wired sensor network feeding detection data to the machine controller. Data integrity check and process control algorithms have to be implemented for the safety and reliability of the overall industrial process. Fabrizio Iacopetti, Sergio Saponara, Luca Fanucci, and Bruno Neri Copyright © 2013 Fabrizio Iacopetti et al. All rights reserved. Thu, 10 Jan 2013 15:36:14 +0000 http://www.hindawi.com/journals/jcnc/2013/148015/ This paper reviews the research work done on the response time analysis of messages in controller area network (CAN) from the time CAN specification was submitted for standardization (1990) and became a standard (1993) up to the present (2012). Such research includes the worst-case response time analysis which is deterministic and probabilistic response time analysis which is stochastic. A detailed view on both types of analyses is presented here. In addition to these analyses, there has been research on statistical analysis of controller area network message response times. Gerardine Immaculate Mary, Z. C. Alex, and Lawrence Jenkins Copyright © 2013 Gerardine Immaculate Mary et al. All rights reserved. Thu, 10 Jan 2013 13:00:50 +0000 http://www.hindawi.com/journals/jcnc/2013/614157/ This paper presents modelling results for H.26x video traffic generated by popular videoconference software applications. The analysis of videoconference data, that were measured during realistic point-point videoconference sessions, led us to the general conclusion that the traffic can be distinguished into two categories: unconstrained and constrained. In the unconstrained traffic, there is a direct relation between the encoder and the form of the frequency histogram of the frame-size sequence. Moreover, for this type of traffic, strong correlations between successive video frames can be found. On the other hand, where bandwidth constraints are imposed during the encoding process, the generated traffic appears to exhibit similar characteristics for all the examined encoders with the very low autocorrelation values being the most notable one. On the basis of these results, this study proposes methods to calculate the parameters of a widely adopted autoregressive model for both types of traffic. S. Domoxoudis, S. Kouremenos, V. Loumos, and A. Drigas Copyright © 2013 S. Domoxoudis et al. All rights reserved. Wed, 09 Jan 2013 14:49:58 +0000 http://www.hindawi.com/journals/jcnc/2013/505910/ We propose a novel architecture for providing quality of experience (QoE) awareness to mobile operator networks. In particular, we describe a possible architecture for QoE-driven resource control for long-term evolution (LTE) and LTE-advanced networks, including a selection of KPIs to be monitored in different network elements. We also provide a description and numerical results of the QoE evaluation process for different data services as well as potential use cases that would benefit from the rollout of the proposed framework. Gerardo Gómez, Javier Lorca, Raquel García, and Quiliano Pérez Copyright © 2013 Gerardo Gómez et al. All rights reserved. Mon, 31 Dec 2012 13:52:42 +0000 http://www.hindawi.com/journals/jcnc/2012/672196/ The mobile computing established communication environment where personal identification is a key factor which influence usability of mobile application. Open personal identity is a partial service which enables crowd resource identifications processing in online distributive unified form over secured communication channel. The service provides current fresh personal identificators which are essential in communication process. Miroslav Behan Copyright © 2012 Miroslav Behan. All rights reserved. Sat, 29 Dec 2012 12:09:58 +0000 http://www.hindawi.com/journals/jcnc/2012/534512/ This paper discusses aims, architecture, and security issues of Smart Grid, taking care of the lesson learned at University of Pisa in research projects on smart energy and grid. A key element of Smart Grid is the energy home area network (HAN), for which an implementation is proposed, dealing with its security aspects and showing some solutions for realizing a wireless network based on ZigBee. Possible hardware-software architectures and implementations using COTS (Commercial Off The Shelf) components are presented for key building blocks of the energy HAN such as smart power meters and plugs and a home smart information box providing energy management policy and supporting user's energy awareness. Sergio Saponara and Tony Bacchillone Copyright © 2012 Sergio Saponara and Tony Bacchillone. All rights reserved. Wed, 26 Dec 2012 14:19:53 +0000 http://www.hindawi.com/journals/jcnc/2012/414796/ The effect of self-interference due to the increase of spatial correlation in a MIMO channel has become one of the limiting factors towards the implementation of future network downlink transmissions. This paper aims to reduce the effect of self-interference in a downlink multiuser- (MU-) MIMO transmission by exploiting the available spatial and frequency diversity. The subcarrier allocation scheme can exploit the frequency diversity to determine the self-interference from the ESINR metric, while the spatial diversity can be exploited by introducing the partial feedback scheme, which offers knowledge of the channel condition to the base station and further reduces the effect before the allocation process takes place. The results have shown that the proposed downlink transmission scheme offers robust bit error rate (BER) performance, even when simulated in a fully correlated channel, without imposing higher feedback requirements on the base controller. Rosdiadee Nordin Copyright © 2012 Rosdiadee Nordin. All rights reserved. Wed, 26 Dec 2012 09:14:21 +0000 http://www.hindawi.com/journals/jcnc/2012/649584/ MoonBae Song, Goreti Marreiros, Hoon Ko, and Jae-Ho Choi Copyright © 2012 MoonBae Song et al. All rights reserved. Sun, 23 Dec 2012 11:34:28 +0000 http://www.hindawi.com/journals/jcnc/2012/703642/ This paper presents case studies of attacks aimed at tactical software defined radios based on a classification with the most common sources of vulnerabilities, classes of attacks, and types of intrusions that military radio sets may suffer. Besides that, we also describe how attack mitigation strategies can impact the development of SDR infrastructures. By using such approach, we identify several possible sources of vulnerabilities, attacks, intrusions, and mitigation strategies, illustrating them onto typical tactical radio network deployment scenarios, as an initial and necessary step for the definition of realistic and relevant security requirements for military software defined radio applications. David Fernandes Cruz Moura, Fabricio Alves Barbosa da Silva, and Juraci Ferreira Galdino Copyright © 2012 David Fernandes Cruz Moura et al. All rights reserved. Wed, 19 Dec 2012 10:38:02 +0000 http://www.hindawi.com/journals/jcnc/2012/259824/ This paper presents a novel pattern recognition approach to spectrum sensing in collaborative cognitive radio systems. In the proposed scheme, discriminative features from the received signal are extracted at each node and used by a classifier at a central node to make a global decision about the availability of spectrum holes for use by the cognitive radio network. Specifically, linear and polynomial classifiers are proposed with energy, cyclostationary, or coherent features. Simulation results in terms of detection and false alarm probabilities of all proposed schemes are presented. It is concluded that cyclostationary-based schemes are the most reliable in terms of detecting primary users in the spectrum, however, at the expense of a longer sensing time compared to coherent based schemes. Results show that the performance is improved by having more users collaborating in providing features to the classifier. It is also shown that, in this spectrum sensing application, a linear classifier has a comparable performance to a second-order polynomial classifier and hence provides a better choice due to its simplicity. Finally, the impact of the observation window on the detection performance is presented. Yasmin Hassan, Mohamed El-Tarhuni, and Khaled Assaleh Copyright © 2012 Yasmin Hassan et al. All rights reserved. Mon, 17 Dec 2012 14:09:09 +0000 http://www.hindawi.com/journals/jcnc/2012/845762/ It has been proposed that Semantic Web technologies would be key enablers in achieving context-aware computing in our everyday environments. In our vision of semantic technology empowered smart spaces, the whole interaction model is based on the sharing of semantic data via common blackboards. This approach allows smart space applications to take full advantage of semantic technologies. Because of its novelty, there is, however, a lack of solutions and methods for developing semantic smart space applications according to this vision. In this paper, we present solutions to the most relevant challenges we have faced when developing context-aware computing in smart spaces. In particular the paper describes (1) methods for utilizing semantic technologies with resource restricted-devices, (2) a solution for identifying real world objects in semantic technology empowered smart spaces, (3) a method for users to modify the behavior of context-aware smart space applications, and (4) an approach for content sharing between autonomous smart space agents. The proposed solutions include ontologies, system models, and guidelines for building smart spaces with the M3 semantic information sharing platform. To validate and demonstrate the approaches in practice, we have implemented various prototype smart space applications and tools. Jussi Kiljander, Arto Ylisaukko-oja, Janne Takalo-Mattila, Matti Eteläperä, and Juha-Pekka Soininen Copyright © 2012 Jussi Kiljander et al. All rights reserved. Thu, 13 Dec 2012 17:31:37 +0000 http://www.hindawi.com/journals/jcnc/2012/427246/ An important performance concern for wireless sensor networks (WSNs) is the total energy dissipated by all the nodes in the network over the course of network lifetime. In this paper, we propose a routing algorithm termed as PCA-guided routing algorithm (PCA-RA) by exploring the principal component analysis (PCA) approach. Our algorithm remarkably reduces energy consumption and prolongs network lifetime by realizing the objective of minimizing the sum of distances between the nodes and the cluster centers in a WSN network. It is demonstrated that the PCA-RA can be efficiently implemented in WSNs by forming a nearly optimal -means-like clustering structure. In addition, it can decrease the network load while maintaining the accuracy of the sensor measurements during data aggregating process. We validate the efficacy and efficiency of the proposed algorithm by simulations. Both theoretical analyses and simulation results demonstrate that this algorithm can perform significantly with less energy consumption and thus prolong the system lifetime for the networks. Gong Chen, Liansheng Tan, Yanlin Gong, and Wei Zhang Copyright © 2012 Gong Chen et al. All rights reserved.