Journal of Computer Networks and Communications The latest articles from Hindawi © 2017 , Hindawi Limited . All rights reserved. Energy Efficient Secure Trust Based Clustering Algorithm for Mobile Wireless Sensor Network Mon, 28 Aug 2017 09:09:09 +0000 The main benefit of selecting a suitable node as cluster head (CH) in clustering for wireless mobile sensor networks (MWSNs) is to prolong the network lifetime. But the safe selection of CH is a challenging task by taking security into account. Mostly CH selection algorithms in MWSN do not consider security when selecting CH. We have proposed secure CH selection algorithm by calculating weight of each node to deal with secure selection using minimum energy consumption. The weight of node is a combination of different metrics including trust metric (behaviors of sensor node) which promotes a secure decision of a CH selection; in terms of this, the node will never be a malicious one. The trust metric is definitive and permits the proposed clustering algorithm to keep away from any malignant node in the area to select a CH, even if the rest of the parameters are in its favor. Other metrics of node include waiting time, connectivity degree, and distance among nodes. The selection of CHs is completed utilizing weights of member nodes. The preparatory outcomes acquired through simulation exhibit the adequacy of our proposed scheme as far as average rate of avoiding malicious node as a CH, energy efficiency, and some other performance parameters are concerned. Eid Rehman, Muhammad Sher, Syed Hussnain Abbas Naqvi, Khan Badar Khan, and Kamran Ullah Copyright © 2017 Eid Rehman et al. All rights reserved. Symmetric Blind Decryption with Perfect Secrecy Wed, 16 Aug 2017 07:09:31 +0000 A blind decryption scheme enables a user to query decryptions from a decryption server without revealing information about the plain-text message. Such schemes are useful, for example, for the implementation of privacy-preserving encrypted file storages and payment systems. In terms of functionality, blind decryption is close to oblivious transfer. For noiseless channels, information-theoretically secure oblivious transfer is impossible. However, in this paper, we show that this is not the case for blind decryption. We formulate a definition of perfect secrecy of symmetric blind decryption for the following setting: at most one of the scheme participants is a passive adversary (honest-but-curious). We also devise a symmetric blind decryption scheme based on modular arithmetic on a ring , where is a prime, and show that it satisfies our notion of perfect secrecy. Juha Partala Copyright © 2017 Juha Partala. All rights reserved. A Novel Audio Cryptosystem Using Chaotic Maps and DNA Encoding Sun, 06 Aug 2017 08:09:32 +0000 Chaotic maps have good potential in security applications due to their inherent characteristics relevant to cryptography. This paper introduces a new audio cryptosystem based on chaotic maps, hybrid chaotic shift transform (HCST), and deoxyribonucleic acid (DNA) encoding rules. The scheme uses chaotic maps such as two-dimensional modified Henon map (2D-MHM) and standard map. The 2D-MHM which has sophisticated chaotic behavior for an extensive range of control parameters is used to perform HCST. DNA encoding technology is used as an auxiliary tool which enhances the security of the cryptosystem. The performance of the algorithm is evaluated for various speech signals using different encryption/decryption quality metrics. The simulation and comparison results show that the algorithm can achieve good encryption results and is able to resist several cryptographic attacks. The various types of analysis revealed that the algorithm is suitable for narrow band radio communication and real-time speech encryption applications. S. J. Sheela, K. V. Suresh, and Deepaknath Tandur Copyright © 2017 S. J. Sheela et al. All rights reserved. Reducing the Amount of Data for Creating Routes in a Dynamic DTN via Wi-Fi on the Basis of Static Data Wed, 26 Jul 2017 06:30:34 +0000 This article presents the results of research on the acceleration of data processing in the construction routing in dynamic DTN, realized through the devices established in moving objects and connected by means of Wi-Fi. The routes are constructed based on the prehistory of the movement of objects, which is stored in the database in the csv format. This database has a large volume and contains unnecessary and incorrect information. The article shows the possibility of speeding up the process of constructing routes using data precleaning. Reducing data volume is proposed by constructing an enlarged grid on the object movement map. This article also demonstrates the use of fuzzy logic and graph theory for constructing routes. Yulia Shichkina and Alexander Koblov Copyright © 2017 Yulia Shichkina and Alexander Koblov. All rights reserved. Assessing Contact Graph Routing Performance and Reliability in Distributed Satellite Constellations Tue, 04 Jul 2017 00:00:00 +0000 Existing Internet protocols assume persistent end-to-end connectivity, which cannot be guaranteed in disruptive and high-latency space environments. To operate over these challenging networks, a store-carry-and-forward communication architecture called Delay/Disruption Tolerant Networking (DTN) has been proposed. This work provides the first examination of the performance and robustness of Contact Graph Routing (CGR) algorithm, the state-of-the-art routing scheme for space-based DTNs. To this end, after a thorough description of CGR, two appealing satellite constellations are proposed and evaluated by means of simulations. Indeed, the DtnSim simulator is introduced as another relevant contribution of this work. Results enabled the authors to identify existing CGR weaknesses and enhancement opportunities. J. A. Fraire, P. Madoery, S. Burleigh, M. Feldmann, J. Finochietto, A. Charif, N. Zergainoh, and R. Velazco Copyright © 2017 J. A. Fraire et al. All rights reserved. SDN-Enabled Communication Network Framework for Energy Internet Tue, 20 Jun 2017 06:51:56 +0000 To support distributed energy generators and improve energy utilization, energy Internet has attracted global research focus. In China, energy Internet has been proposed as an important issue of government and institutes. However, managing a large amount of distributed generators requires smart, low-latency, reliable, and safe networking infrastructure, which cannot be supported by traditional networks in power grids. In order to design and construct smart and flexible energy Internet, we proposed a software defined network framework with both microgrid cluster level and global grid level designed by a hierarchical manner, which will bring flexibility, efficiency, and reliability for power grid networks. Finally, we evaluate and verify the performance of this framework in terms of latency, reliability, and security by both theoretical analysis and real-world experiments. Zhaoming Lu, Chunlei Sun, Jinqian Cheng, Yang Li, Yong Li, and Xiangming Wen Copyright © 2017 Zhaoming Lu et al. All rights reserved. Selective Route Based on SNR with Cross-Layer Scheme in Wireless Ad Hoc Network Thu, 25 May 2017 06:15:43 +0000 In this study, we developed network and throughput formulation models and proposed new method of the routing protocol algorithm with a cross-layer scheme based on signal-to-noise ratio (SNR). This method is an enhancement of routing protocol ad hoc on-demand distance vector (AODV). This proposed scheme uses selective route based on the SNR threshold in the reverse route mechanism. We developed AODV SNR-selective route (AODV SNR-SR) for a mechanism better than AODV SNR, that is, the routing protocol that used average or sum of path SNR, and also better than AODV which is hop-count-based. We also used selective reverse route based on SNR mechanism, replacing the earlier method to avoid routing overhead. The simulation results show that AODV SNR-SR outperforms AODV SNR and AODV in terms of throughput, end-to-end delay, and routing overhead. This proposed method is expected to support Device-to-Device (D2D) communications that are concerned with the quality of the channel awareness in the development of the future Fifth Generation (5G). Istikmal, Adit Kurniawan, and Hendrawan Copyright © 2017 Istikmal et al. All rights reserved. Novel Opportunistic Network Routing Based on Social Rank for Device-to-Device Communication Thu, 18 May 2017 07:28:43 +0000 In recent years, there has been dramatic proliferation of research concerned with fifth-generation (5G) mobile communication networks, among which device-to-device (D2D) communication is one of the key technologies. Due to the intermittent connection of nodes, the D2D network topology may be disconnected frequently, which will lead to failure in transmission of large data files. In opportunistic networks, in case of encountering nodes which never meet before a flood message blindly to cause tremendous network overhead, a novel opportunistic network routing protocol based on social rank and intermeeting time (SRIT) is proposed in this paper. An improved utility approach applied in utility replication based on encounter durations and intermeeting time is put forward to enhance the routing efficiency. Meanwhile, in order to select better candidate nodes in the network, a social graph among people is established when they socially relate to each other in social rank replication. The results under the scenario show an advantage of the proposed opportunistic network routing based on social rank and intermeeting time (SRIT) over the compared algorithms in terms of delivery ratio, average delivery latency, and overhead ratio. Tong Wang, Yongzhe Zhou, Yunfeng Wang, and Mengbo Tang Copyright © 2017 Tong Wang et al. All rights reserved. Grassmannian Constellation Based on Antipodal Points and Orthogonal Design and Its Simplified Detecting Algorithm Mon, 03 Apr 2017 00:00:00 +0000 This study presents a framework of the unitary space time modulation (USTM) constellation based on antipodal points over Grassmannian manifold. The antipodal constellation enables an intrinsic simplified ML detecting algorithm. The algebraic orthogonal USTM constellation is also an antipodal constellation which, apart from being adaptive to the antipodal simplified ML detector, also has another simplified ML detector based on its self-indexing features, and the latter is simpler because of getting rid of the matrix operation. A searching orthogonal USTM constellation based on the grid search algorithm is obtained under the presented framework and its minimum Frobenius chordal distance and simulation performance are be superior to those of the algebraic orthogonal USTM constellation. Li Peng, Dacong Hu, Lin Zhang, and Zhen Qin Copyright © 2017 Li Peng et al. All rights reserved. GWO-LPWSN: Grey Wolf Optimization Algorithm for Node Localization Problem in Wireless Sensor Networks Tue, 21 Mar 2017 00:00:00 +0000 Seyedali Mirjalili et al. (2014) introduced a completely unique metaheuristic technique particularly grey wolf optimization (GWO). This algorithm mimics the social behavior of grey wolves whereas it follows the leadership hierarchy and attacking strategy. The rising issue in wireless sensor network (WSN) is localization problem. The objective of this problem is to search out the geographical position of unknown nodes with the help of anchor nodes in WSN. In this work, GWO algorithm is incorporated to spot the correct position of unknown nodes, so as to handle the node localization problem. The proposed work is implemented using MATLAB 8.2 whereas nodes are deployed in a random location within the desired network area. The parameters like computation time, percentage of localized node, and minimum localization error measures are utilized to analyse the potency of GWO rule with other variants of metaheuristics algorithms such as particle swarm optimization (PSO) and modified bat algorithm (MBA). The observed results convey that the GWO provides promising results compared to the PSO and MBA in terms of the quick convergence rate and success rate. R. Rajakumar, J. Amudhavel, P. Dhavachelvan, and T. Vengattaraman Copyright © 2017 R. Rajakumar et al. All rights reserved. Call Admission Scheme for Multidimensional Traffic Assuming Finite Handoff User Sun, 05 Mar 2017 09:57:44 +0000 Usually, the number of users within a cell in a mobile cellular network is considered infinite; hence, model is appropriate for new originated traffic, but the number of ongoing calls around a cell is always finite. Hence, the traffic model of handoff call will be . In this paper, a -dimensional traffic model of a mobile cellular network is proposed using the combination of limited and unlimited users case. A new call admission scheme (CAS) is proposed based on both thinning scheme and fading condition. The fading condition of the wireless channel access to a handoff call is prioritized compared to newly originated calls. Md. Baitul Al Sadi and Afsana Nadia Copyright © 2017 Md. Baitul Al Sadi and Afsana Nadia. All rights reserved. Energy Efficient Clustering Based Network Protocol Stack for 3D Airborne Monitoring System Thu, 16 Feb 2017 09:17:47 +0000 Wireless Sensor Network consists of large number of nodes densely deployed in ad hoc manner. Usually, most of the application areas of WSNs require two-dimensional (2D) topology. Various emerging application areas such as airborne networks and underwater wireless sensor networks are usually deployed using three-dimensional (3D) network topology. In this paper, a static 3D cluster-based network topology has been proposed for airborne networks. A network protocol stack consisting of various protocols such as TDMA MAC and dynamic routing along with services such as time synchronization, Cluster Head rotation, and power level management has been proposed for this airborne network. The proposed protocol stack has been implemented on the hardware platform consisting of number of TelosB nodes. This 3D airborne network architecture can be used to measure Air Quality Index (AQI) in an area. Various parameters of network such as energy consumption, Cluster Head rotation, time synchronization, and Packet Delivery Ratio (PDR) have been analyzed. Detailed description of the implementation of the protocol stack along with results of implementation has been provided in this paper. Abhishek Joshi, Sarang Dhongdi, Rishabh Sethunathan, Pritish Nahar, and K. R. Anupama Copyright © 2017 Abhishek Joshi et al. All rights reserved. Enabling LTE and WiFi Coexisting in 5 GHz for Efficient Spectrum Utilization Thu, 09 Feb 2017 00:00:00 +0000 Due to the increasing mobile traffic demands in cellular network, researchers have proposed the coexistence of LTE and WiFi technologies in 5 GHz unlicensed bands. Therefore, how to efficiently utilize the spectrum in 5 GHz becomes extremely important. To avoid the channel access conflicts, current LTE Unlicensed (LTE-U) technology introduces the duty cycle of LTE, while License-Assisted Access (LAA) technology introduces Listen-Before-Talk (LBT) mechanism. While these two technologies improve the spectrum utilization by using time division access schema, we believe that more efficient spectrum utilization can be achieved by enabling simultaneous transmissions from LTE and WiFi. In this paper, we propose a novel method (i.e., Low Amplitude Stream Injection (LASI) method) to enable the simultaneous transmissions of WiFi and LTE frames in the same channel and recover the data from the conflicts. To further utilize the LASI method, we introduce the Conflict-Tolerant Channel Allocation (CTCA) algorithm to optimize the channel allocation and achieve more efficient spectrum utilization in 5 GHz. Extensive simulation results show that our approach achieves lower latency and higher throughput. Compared with the state-of-the-art LTE-U and LAA technologies, our approach can improve the spectrum efficiency 2.9 times. Hongyu Sun, Zhiyi Fang, Qun Liu, Zheng Lu, and Ting Zhu Copyright © 2017 Hongyu Sun et al. All rights reserved. Analytical Computation of Information Rate for MIMO Channels Wed, 08 Feb 2017 00:00:00 +0000 Information rate for discrete signaling constellations is significant. However, the computational complexity makes information rate rather difficult to analyze for arbitrary fading multiple-input multiple-output (MIMO) channels. An analytical method is proposed to compute information rate, which is characterized by considerable accuracy, reasonable complexity, and concise representation. These features will improve accuracy for performance analysis with criterion of information rate. Jinbao Zhang, Zhenhui Tan, and Song Chen Copyright © 2017 Jinbao Zhang et al. All rights reserved. Cloud-Based DDoS HTTP Attack Detection Using Covariance Matrix Approach Tue, 24 Jan 2017 00:00:00 +0000 In this era of technology, cloud computing technology has become essential part of the IT services used the daily life. In this regard, website hosting services are gradually moving to the cloud. This adds new valued feature to the cloud-based websites and at the same time introduces new threats for such services. DDoS attack is one such serious threat. Covariance matrix approach is used in this article to detect such attacks. The results were encouraging, according to confusion matrix and ROC descriptors. Abdulaziz Aborujilah and Shahrulniza Musa Copyright © 2017 Abdulaziz Aborujilah and Shahrulniza Musa. All rights reserved. IoT in Action: Design and Implementation of a Building Evacuation Service Sun, 22 Jan 2017 00:00:00 +0000 With the development of sensor technologies, various application areas have emerged. The usage of these technologies and exploitation of recent improvements have clear benefits on building applications. Such use-cases can improve smart functions of buildings and can increase the end-user comfort. As a similar notion, building automation systems (BAS) are smart systems that target to provide automated management of various control services and to improve resource usage efficiency. However, buildings generally contain hardware and control services from a diverse set of characteristics. The automated and central management of such functions can be challenging. In order to overcome such issues, an Emergency Evacuation Service is proposed for BAS, where requirements of such central management model are analyzed and model content and subservice definitions are prepared. A crucial scenario, which could be a necessity for future BAS, is defined and an approach for evacuation of people in the buildings at emergency situations is proposed. For real-life scenarios, the Evacuation Service is implemented by using a low-cost design, which is appropriate for Internet of Things (IoT) based BAS applications. As demonstrated, the proposed service model can provide effective performance in real-life deployments. Selahattin Gokceli, Nikolay Zhmurov, Gunes Karabulut Kurt, and Berna Ors Copyright © 2017 Selahattin Gokceli et al. All rights reserved. Robust Preamble-Based Timing Synchronization for OFDM Systems Mon, 02 Jan 2017 12:53:57 +0000 This study presents a novel preamble-based timing offset estimation method for orthogonal frequency division multiplexing (OFDM) systems. The proposed method is robust, immune to the carrier frequency offset (CFO), and independent of the structure of the preamble. The performance of the new method is demonstrated in terms of mean square error (MSE) obtained by simulation in multipath fading channels. The results indicate that the new method significantly improves timing performance in comparison with existing methods. Yun Liu, Fei Ji, Hua Yu, Dehuan Wan, Fangjiong Chen, and Ling Yang Copyright © 2017 Yun Liu et al. All rights reserved. An Architecture for Anonymous Mobile Coupons in a Large Network Sun, 18 Dec 2016 13:34:05 +0000 A mobile coupon (m-coupon) can be presented with a smartphone for obtaining a financial discount when purchasing a product or a service. M-coupons are a powerful marketing tool that has enjoyed a huge growth and diffusion, involving tens of millions of people each year. We propose an architecture which may enable significant improvements over current m-coupon technology, in terms of acceptance of potential customers and of marketing actions that become feasible: the customer does not need to install any dedicated app; an m-coupon is not bound to any specific device or customer; an m-coupon may be redeemed at any store in a set of potentially many thousands of stores, without any prior arrangement between customer and store. We are not aware of any proposal with these properties. Alberto Bartoli and Eric Medvet Copyright © 2016 Alberto Bartoli and Eric Medvet. All rights reserved. Dynamic Clustering Algorithm for Tracking Targets with High and Variable Celerity (ATHVC) Sun, 18 Dec 2016 06:12:21 +0000 Target tracking with the wireless sensors networks is to detect and locate a target on its entire path through a region of interest. This application arouses interest in the world of research for its many fields of use. Wireless sensor networks, thanks to their versatility, can be used in many hostile and inaccessible to humans environments. However, with a limited energy, they cannot remain permanently active, which can significantly reduce their lifetime. The formation of a cluster network seems an effective mechanism to increase network lifetime. We propose to build optimal dynamic clusters on the target trajectory. For increasing energy efficiency, our algorithm integrates for the first time, to our knowledge, strategies to avoid overlapping clusters and a model to wake up the sensors, adapting to the context of targets with large and variable speed. Mohamed Toumi, Abderrahim Maizate, Mohammed Ouzzif, and Med Said Salah Copyright © 2016 Mohamed Toumi et al. All rights reserved. Performance Analysis of the Effect of Nonlinear Low Noise Amplifier for Wideband Spectrum Sensing in the Poisson Field of Interferers Thu, 24 Nov 2016 12:21:34 +0000 A cognitive radio (CR) device likely consists of a low-cost low noise amplifier (LNA) due to the mass-production reason. Nevertheless, the operation of a low-cost LNA becomes highly nonlinear causing intermodulation (IM) interference. The most important task of CR devices is to sense the wideband spectrum to increase opportunistic throughput. In noncooperative secondary networks, the IM interference usually can be ignored for the narrowband spectrum sensing, while the IM interference needs to be taken into account along with interference from other CR devices in the wideband case. Our contribution is to study the effects of a nonlinear LNA for the second case in environments modeled by Poisson field of interferers reflecting more realistic scenario. As shown in the simulation results, the performance of the receiver is degraded in all the cases due to the nonlinearity of LNA. The adaptive threshold setting based on the multivariate Gaussian mixture model is proposed to improve the receiver performance. Bipun Man Pati and Attaphongse Taparugssanagorn Copyright © 2016 Bipun Man Pati and Attaphongse Taparugssanagorn. All rights reserved. Performance Analysis of Reuse Distance in Cooperative Broadcasting Tue, 15 Nov 2016 12:35:10 +0000 Cooperative broadcasting is a promising technique for robust broadcast with low overhead and delay in mobile ad hoc networks. The technique is attractive for mission-oriented mobile communication, where a majority of the traffic is of broadcast nature. In cooperative broadcasting, all nodes simultaneously retransmit packets. The receiver utilizes cooperative diversity in the simultaneously received signals. The retransmissions continue until all nodes are reached. After the packet has traveled a specific number of hops out from the source, denoted as reuse distance, the source node transmits a new broadcast packet in the time slot used for the previous broadcast packet. If the reuse distance is too small, interference causes packet loss in intermediate nodes. In the literature, a reuse distance of three is common. With an analysis based on a realistic interference model and real terrain data, we show that a reuse distance of at least four is necessary to avoid packet loss in sparsely connected networks, especially for high spectral efficiencies. For frequency hopping, widely used in military systems, we propose a novel method. This method almost eliminates interference for a reuse distance of three, increasing the throughput by 33% compared to systems with a reuse distance of four. Jimmi Grönkvist, Anders Hansson, and Arwid Komulainen Copyright © 2016 Jimmi Grönkvist et al. All rights reserved. Wormhole Detection Based on Ordinal MDS Using RTT in Wireless Sensor Network Mon, 07 Nov 2016 08:08:37 +0000 In wireless communication, wormhole attack is a crucial threat that deteriorates the normal functionality of the network. Invasion of wormholes destroys the network topology completely. However, most of the existing solutions require special hardware or synchronized clock or long processing time to defend against long path wormhole attacks. In this work, we propose a wormhole detection method using range-based topology comparison that exploits the local neighbourhood subgraph. The Round Trip Time (RTT) for each node pair is gathered to generate neighbour information. Then, the network is reconstructed by ordinal Multidimensional Scaling (MDS) followed by a suspicion phase that enlists the suspected wormholes based on the spatial reconstruction. Iterative computation of MDS helps to visualize the topology changes and can localize the potential wormholes. Finally, a verification phase is used to remove falsely accused nodes and identify real adversaries. The novelty of our algorithm is that it can detect both short path and long path wormhole links. Extensive simulations are executed to demonstrate the efficacy of our approach compared to existing ones. Saswati Mukherjee, Matangini Chattopadhyay, Samiran Chattopadhyay, and Pragma Kar Copyright © 2016 Saswati Mukherjee et al. All rights reserved. Creating Values out of Internet of Things: An Industrial Perspective Wed, 19 Oct 2016 06:48:39 +0000 Internet of Things based cloud is envisaged to extract values other than the specified purpose for which it is to be utilized. It is hereby apprehended that different genre of values, rather business values, could efficiently be assimilated from the Internet of Things cloud platforms. It is also investigated to identify numerous domains of applications that are currently being associated with the similar cloud platforms. A case study on various types of value generation methods has been performed. A novel Internet of Things cloud stack is proposed to disseminate and aggregate the business values. Few research challenges are observed that shall need appropriate indulgence to generate more business values out of Internet of Things based cloud. This paper also seeks few research and industry related problems that need to be resolved. It further recommends several key parameters to the enterprise and government policymakers that should immediately be dealt with for long-term success. Partha Pratim Ray Copyright © 2016 Partha Pratim Ray. All rights reserved. Measurement of Mobile Switching Centres Throughput in GSM Network Integrating Sliding Window Algorithm with a Single Server Finite Queuing Model Thu, 13 Oct 2016 07:47:42 +0000 The sliding window algorithm proposed for determining an optimal sliding window does not consider the waiting times of call setup requests of a mobile station in queue at a Mobile Switching Centre (MSC) in the Global System for Mobile (GSM) Communication Network. This study proposes a model integrating the sliding window algorithm with a single server finite queuing model, referred to as integrated model for measurement of realistic throughput of a MSC considering the waiting times of call setup requests. It assumes that a MSC can process one call setup request at a time. It is useful in determining an optimal sliding window size that maximizes the realistic throughput of a MSC. Though the model assumes that a MSC can process one call setup request at a time, its scope can be extended for measuring the realistic throughput of a MSC that can process multiple call setup requests at a time. Dinaker Babu Bollini, Mannava Muniratnam Naidu, and Mallikharjuna Rao Nuka Copyright © 2016 Dinaker Babu Bollini et al. All rights reserved. A Quantitative Risk Evaluation Model for Network Security Based on Body Temperature Wed, 12 Oct 2016 13:52:17 +0000 These days, in allusion to the traditional network security risk evaluation model, which have certain limitations for real-time, accuracy, characterization. This paper proposed a quantitative risk evaluation model for network security based on body temperature (QREM-BT), which refers to the mechanism of biological immune system and the imbalance of immune system which can result in body temperature changes, firstly, through the -contiguous bits nonconstant matching rate algorithm to improve the detection quality of detector and reduce missing rate or false detection rate. Then the dynamic evolution process of the detector was described in detail. And the mechanism of increased antibody concentration, which is made up of activating mature detector and cloning memory detector, is mainly used to assess network risk caused by various species of attacks. Based on these reasons, this paper not only established the equation of antibody concentration increase factor but also put forward the antibody concentration quantitative calculation model. Finally, because the mechanism of antibody concentration change is reasonable and effective, which can effectively reflect the network risk, thus body temperature evaluation model was established in this paper. The simulation results showed that, according to body temperature value, the proposed model has more effective, real time to assess network security risk. Y. P. Jiang, C. C. Cao, X. Mei, and H. Guo Copyright © 2016 Y. P. Jiang et al. All rights reserved. A Persistent Structured Hierarchical Overlay Network to Counter Intentional Churn Attack Wed, 12 Oct 2016 11:21:57 +0000 The increased use of structured overlay network for a variety of applications has attracted a lot of attention from both research community and attackers. However, the structural constraints, open nature (anybody can join and anybody may leave), and unreliability of its participant nodes significantly affect the performance of these applications and make it vulnerable to a variety of attacks such as eclipse, Sybil, and churn. One attack to compromise the service availability in overlay network is intentional churn (join/leave) attack, where a large number of malicious users will join and leave the overlay network so frequently that the entire structure collapses and becomes unavailable. The focus of this paper is to provide a new robust, efficient, and scalable hierarchical overlay architecture that will counter these attacks by providing a structure that can accommodate the fleeting behaviour of nodes without causing much structural inconsistencies. The performance evaluation showed that the proposed architecture has more failure resilience and self-organization as compared to chord based architecture. Experimental results have demonstrated that the effect of failures on an overlay is proportional to the size of failure. Ramanpreet Kaur, Amrit Lal Sangal, and Krishan Kumar Copyright © 2016 Ramanpreet Kaur et al. All rights reserved. Human Depth Sensors-Based Activity Recognition Using Spatiotemporal Features and Hidden Markov Model for Smart Environments Tue, 04 Oct 2016 14:24:14 +0000 Nowadays, advancements in depth imaging technologies have made human activity recognition (HAR) reliable without attaching optical markers or any other motion sensors to human body parts. This study presents a depth imaging-based HAR system to monitor and recognize human activities. In this work, we proposed spatiotemporal features approach to detect, track, and recognize human silhouettes using a sequence of RGB-D images. Under our proposed HAR framework, the required procedure includes detection of human depth silhouettes from the raw depth image sequence, removing background noise, and tracking of human silhouettes using frame differentiation constraints of human motion information. These depth silhouettes extract the spatiotemporal features based on depth sequential history, motion identification, optical flow, and joints information. Then, these features are processed by principal component analysis for dimension reduction and better feature representation. Finally, these optimal features are trained and they recognized activity using hidden Markov model. During experimental results, we demonstrate our proposed approach on three challenging depth videos datasets including IM-DailyDepthActivity, MSRAction3D, and MSRDailyActivity3D. All experimental results show the superiority of the proposed approach over the state-of-the-art methods. Ahmad Jalal, Shaharyar Kamal, and Daijin Kim Copyright © 2016 Ahmad Jalal et al. All rights reserved. Corrigendum to “Hole Detection for Quantifying Connectivity in Wireless Sensor Networks: A Survey” Wed, 14 Sep 2016 09:08:41 +0000 Pearl Antil and Amita Malik Copyright © 2016 Pearl Antil and Amita Malik. All rights reserved. Exact SER Analysis of DFrFT-Based QPSK OFDM System over Frequency Selective Rayleigh Fading Channel with CFO Tue, 06 Sep 2016 09:11:38 +0000 We present the exact symbol error rate (SER) expression for quadrature phase shift keying (QPSK) modulation in frequency selective Rayleigh fading channel for discrete fractional Fourier transform- (DFrFT-) based orthogonal frequency division multiplexing (OFDM) system in the presence of carrier frequency offset (CFO). The theoretical result is confirmed by means of Monte Carlo simulations. It is shown that the performance of the proposed system, at different values of the DFrFT angle parameter “,” is better than that of OFDM based on discrete Fourier transform. Atul Kumar, Maurizio Magarini, Hem Dutt Joshi, and Rajiv Saxena Copyright © 2016 Atul Kumar et al. All rights reserved. Developing an On-Demand Cloud-Based Sensing-as-a-Service System for Internet of Things Tue, 30 Aug 2016 09:30:54 +0000 The increasing number of Internet of Things (IoT) devices with various sensors has resulted in a focus on Cloud-based sensing-as-a-service (CSaaS) as a new value-added service, for example, providing temperature-sensing data via a cloud computing system. However, the industry encounters various challenges in the dynamic provisioning of on-demand CSaaS on diverse sensor networks. We require a system that will provide users with standardized access to various sensor networks and a level of abstraction that hides the underlying complexity. In this study, we aim to develop a cloud-based solution to address the challenges mentioned earlier. Our solution, SenseCloud, includes a sensor virtualization mechanism that interfaces with diverse sensor networks, a multitenancy mechanism that grants multiple users access to virtualized sensor networks while sharing the same underlying infrastructure, and a dynamic provisioning mechanism to allow the users to leverage the vast pool of resources on demand and on a pay-per-use basis. We implement a prototype of SenseCloud by using real sensors and verify the feasibility of our system and its performance. SenseCloud bridges the gap between sensor providers and sensor data consumers who wish to utilize sensor data. Mihui Kim, Mihir Asthana, Siddhartha Bhargava, Kartik Krishnan Iyyer, Rohan Tangadpalliwar, and Jerry Gao Copyright © 2016 Mihui Kim et al. All rights reserved.