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Summary: Recently, many researches have been conducted to exploit the compressive sensing (CS) theory in wireless sensor networks (WSNs). One of the most important goals in CS is to prolong the lifetime of WSNs. But CS may suffer from some errors during the reconstruction phase. In addition, an adaptive version of CS named Bayesian compressive sensing has been studied to improve the reconstruction accuracy in WSNs. This paper investigates these adaptive methods and identifies their associated problems. Finally, a distributed and semi‐adaptive CS‐based data collection method is proposed. The proposed method tackles the aforementioned problems. Simulation results show that considering both lifetime and accuracy factors as a compound metric, the proposed method yields a 200% improvement compared with the Bayesian compressive sensing‐based method and outperforms other compared methods in the literature. [ABSTRACT FROM AUTHOR]

Summary: This paper investigates the secrecy outage probability (SOP) and intercept behavior for the amplify‐and‐forward network over Nakagami‐m fading channels. Relay selection schemes are evaluated. The optimal and suboptimal criterions require the instantaneous and statistical channel state information of the eavesdroppers' channels, respectively. The enhanced 2‐hop criterion needs the additional information of the target secrecy rate for relay selection. Theoretical analysis reveals that the diversity order of the SOP is dominated by the minimum fading figures of the source‐relay and relay‐destination channels, while that of the intercept probability depends on the fading figure of the relay‐destination channel. In the multirelay scenario, the optimal, suboptimal, and enhanced 2‐hop scheme achieve the same diversity orders of the SOP. For the intercept probability, the optimal and second‐hop relay selection schemes provide the same diversity order, while the diversity orders of the suboptimal and enhanced 2‐hop schemes are the same. Simulation results finally substantiate the accuracy of the theoretical analysis. [ABSTRACT FROM AUTHOR]

Summary: Network virtualization enables service providers to instantiate virtual networks on a common physical infrastructure. Virtual networks are then allocated to clients in order to deploy or test their services. Thus, clients do not know how their traffic is routed, which server is responding, and which path is crossed. Service providers who own the physical infrastructure aim to share the load among multiple servers for traffic routing. However, those who do not own the infrastructure and want to lease it essay to concentrate all the traffic on one server and exactly the closest server. In this paper, we model the problems of load sharing on multiple servers and traffic concentration on one server as two mathematical programs. The objective functions correspond to service providers' aims under a delay constraint based on the M/D/1/N queue's mean sojourn time's formula. Due to its hardness, we provide an approximation of the delay constraint at low and medium traffic intensities. The approximation is analytically proved by the Taylor series development at a chosen point. Finally, through simulation and analytical models, we compare the performance of programs' optimal solutions. We notice that load sharing decreases the packet loss and jitter values. However, traffic concentration reduces the latency. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a device‐to‐device (D2D)–pairing scheme based on Voronoi diagram, which establishes D2D links by the relation of transmission powers and link distances. Using the principle of stochastic geometry and channel inversion, the coverage probability is analyzed, we observe that the co‐channel interference caused by cellular networks is stable in theory, and the influence of link distance parameter is highlighted as well. According to the second‐order moment of link distance, the new metric space of D2D terminals set is constructed, in which Voronoi diagram is degenerated into Delaunay triangles set to represent the potential D2D links. In addition, on the basis of the mini‐max length criterion of Delaunay triangle, the D2D communication range–limiting algorithm is designed. Finally, the more intuitive results compared with conventional D2D communications are displayed by simulations. Owing to restraining the D2D communication range, lower co‐channel interference can be obtained. Specially, the D2D‐pairing scheme is approximate local optimal under the D2D communication range–limiting algorithm, and it can provide more fairness than greedy algorithm. [ABSTRACT FROM AUTHOR]

To balance and improve the resource utilization of the orthogonal frequency division multiple access (OFDMA) cellular networks, we switch parts of the edge users in overloaded cell to the adjacent light-loaded cells by using the inter-cell relay. The efficiency of traditional load balancing method based on the cell switching is low and in some cases, will occur the collision load problem. In this paper, we propose a new load balancing scheme based on inter-cell relay in downlink OFDMA cellular networks. Besides, we put forward a new spectrum division scheme to reduce interference and improve spectrum efficiency. According to the formulas derived from the model we established, we can obtain the signal interference ratio and further to calculate the amount of remaining subcarrier and the throughput of the system. Finally, through numerical calculation and simulation, the result shows that the load balancing and spectrum division schemes can remit the resource stress of the overloaded cell and improve the spectrum utilization in adjacent cells. [ABSTRACT FROM AUTHOR]

This paper deals with the problem of sensor node localization in the presence of uncertainty in anchor node location. Aqueous environments are prone to adverse effects of underwater currents. This adversity causes non-negligible mobility to the anchor nodes deployed under water. Localization in the presence of uncertainty in the anchor node location is quite challenging. Also, the authors consider the ray-bending property of underwater medium due to depth dependent sound speed, to furnish the accurate position estimate of the target node. Standard ray equations are used to model the path followed by acoustic rays in water. Maximum likelihood estimation is proposed to estimate the location of target node with uncertainty in anchor node positions and is compared with the scheme with exact knowledge of anchor node positions, and the results are reported. Monte Carlo simulation is used to assess the performance of the proposed method. Also, the Cramer-Rao lower bound with uncertainty in anchor nodes is derived and described. Simulation results of the proposed algorithm outperform the existing algorithm with known anchor location by up to 49.4%, and hence, accuracy is improved in the proposed method. [ABSTRACT FROM AUTHOR]

SUMMARY In this paper, we consider a vehicular ad hoc network used for distributing traffic information and investigate the minimum uniform transmit power, to be used by all vehicles, sufficient to guarantee network connectivity, in the presence of channel fading. As opposed to the conventional graph theoretic approach, in this paper, the network connectivity problem is analyzed from a physical layer perspective in which a given multi-hop path joining a pair of vehicles in the network is considered to be connected if and only if the average route BER corresponding to this path meets a target requirement. The analysis considers the communication range of each vehicle to be a random variable. The random communication range model is relevant for connectivity analysis because it can account for variability in the communication links and thus will be able to accurately estimate the network connectivity probability after network setup. We derive closed form analytical expression for the minimum transmit power sufficient to ensure network connectivity. We also derive analytical expression for the maximum number of hops, a packet can traverse satisfying the route BER constraint, for a given transmit power. The validity of our theoretical analysis is verified by extensive simulation studies. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper proposes a novel robust affine projection sign algorithm (R-APSA) through a modified criterion that consists of the Euclidean norm of the sum of the difference between the present weight vector and the previous weight vectors. Because the filter update equation of the proposed R-APSA is obtained from the modified criterion, it has robustness against the high power of measurement noises. Moreover, due to the characteristic inherent in the original APSA, the proposed R-APSA performs well even though impulsive noises occur. Simulation results verify that the proposed R-APSA attains smaller steady-state errors than the existing released algorithms. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The near-field electromagnetic ranging technology exploits the near-field behavior of radio signals to measure distance in indoor real-time location system. In this paper, we propose a new adaptive time-delay estimation algorithm based on maximum correntropy criterion (MCC) and received signal strength indication (RSSI), abbreviated as RSSIMCC. The proposed RSSIMCC algorithm estimates the time delay between the electric and magnetic components of low-frequency signals in the near field instead of detecting the phase difference. An inaccurate time-delay estimation value obtained according to the RSSI is used as the initial time delay of adaptive time-delay estimator, which is not far from the true time delay and can improve the convergence speed. Through the analysis of simulation and experiment results, we conclude that the proposed RSSIMCC algorithm can estimate the time delay with small steady-state error in near-field electromagnetic ranging application. Then the time delay estimated by RSSIMCC algorithm can be exploited based on the near-field behavior of radio signals for ranging in an indoor environment. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper proposes a distributed coordination framework with opportunistic scheduling among multiple users as opposed to the existing works on the multiple-cell cooperative beamforming problem that deals with a single active user in each cell. In this cross-layer design framework that deals with the beamforming in the physical layer and multiuser scheduling in the upper layer, radio resource management and inter-cell coordination issues are jointly considered to improve the cell-edge throughput performance by trading off their individual benefit in an optimal manner. Our simulation results demonstrated that its performance can reach up to 85% of its upper bound at the cell boundary. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY In this paper we study the resource allocation problem for the multiuser orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems with proportional rate constraints. The mutual interference introduced by primary user (PU) and cognitive radio user (also referred to secondary user, SU) makes the optimization problem of CR systems more complex. Moreover, the interference introduced to PUs must be kept under a given threshold. In this paper, the highest achievable rate of each OFDM subchannel is calculated by jointly considering the channel gain and interference level. First, a subchannel is assigned to the SU with the highest achievable rate. The remaining subchannels are always allocated to the SU that suffers the severest unjustness. Second, an efficient bit allocation algorithm is developed to maximize the sum capacity, which is again based on the highest achievable rate of each subchannel. Finally, an adjustment procedure is designed to maintain proportional fairness. Simulation results show that the proposed algorithm maximizes the sum capacity while keeping the proportional rate constraints satisfied. The algorithm exhibits a good tradeoff between sum capacity maximization and proportional fairness. Furthermore, the proposed algorithm has lower complexity compared with other algorithms, rendering it promising for practical applications. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, we explore the advantages of network coding and space-time coding in improving the performance of two-way-relayed communications where two terminals absent of direct links exchange information through a single relay in between. Network coding allows embracing the interference from other terminals thereby turning it into a capacity boost. The application of space-time codes yields higher capacity by exploiting the spatial diversity. The joint performance of both techniques is studied in this paper. Specifically, we consider the class of decode-and-forward (DF) relaying strategy, evaluated in terms of symbol error rate using BPSK and QPSK modulations by both theoretical analysis and simulation. Based on our results, DF outperforms the amplify-and-decode and partial-decode-and-forward protocols. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Transmitted reference pulse cluster (TRPC) signaling was recently proposed for low data rate ultra-wideband communications. Compared with the conventional transmitted reference (TR), TRPC has a more compact and uniform spacing for the reference and data pulses and therefore solves the implementation problem posed by the long delay line requirement in the conventional TR. In this paper, downlink multiple access issue is further investigated for TRPC systems. According to the TRPC signaling structure, both code division multiple access (CDMA) and time division multiple access (TDMA) methods are discussed. Theoretical analysis and simulation results show that TDMA outperforms CDMA in both bit error rate performance and throughput. Copyright © 2010 John Wiley & Sons, Ltd. In this paper, the downlink multiple access issue has been discussed for TRPC systems. According to the TRPC signaling structure, both CDMA and TDMA schemes were employed. We have shown that TDMA exhibits a robust performance in both LOS and NLOS environments. In NLOS channels, CDMA performs nearly the same as TDMA. However, in LOS channels, the performance of CDMA degrades significantly in the case of large numbers of users. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper considers the impact of dual polarization adoption on the performance for a fixed wireless access (FWA) network. The major limiting factor of the performance in these systems is co-channel interference (CCI) originating from intracell and intercell concurrent transmissions. The proposed framework combines an appropriate time domain radio resource allocation technique with a dual polarization pattern to mitigate CCI and enhance the obtained signal to interference plus noise ratio (SINR). Simulation results present the performance of the proposed framework against various terrain categories and sector antenna characteristics. Copyright © 2010 John Wiley & Sons, Ltd. This paper considers the impact of dual polarization adoption on the performance for a fixed wireless access (FWA) network. The proposed framework combines an appropriate time domain radio resource allocation technique with a dual polarization pattern to mitigate co-channel interference (CCI) and enhance the obtained signal to interference plus noise ratio (SINR). Simulation results present the performance of the proposed framework against various terrain categories and sector antenna characteristics. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Optical burst switching (OBS) provides a promising solution to utilize the huge terahertz bandwidth of optical wavelength division multiplexing (WDM) transmission technology. To exploit this bandwidth, several reservation schemes have been proposed that include just-in-time (JIT) signaling, just-enough-time (JET) signaling and burst segmentation (BS). It is necessary to investigate the performance of these schemes under the same constraints for a prescribed OBS application. Accordingly, in this paper, we analyzed and compared the performance of JIT, JET and BS techniques under various scenarios such as network size, delay variation and load variation in an OBS network using various performance metrics, such as the offset time and switch configuration time. Also, the performance of the network under various switching delays was also investigated. The modified BS reservation scheme has been found to yield significantly better performance and better throughput compared with the JIT and JET reservation schemes. Test results show that the effect of varying loads as well as delays significantly impacts the performance of the OBS network. The results presented in this paper are expected to lead further performance improvements in OBS networks using the BS reservation scheme. Copyright © 2010 John Wiley & Sons, Ltd. In this paper, it is shown that the performance of an OBS node can be significantly improved using the BS reservation scheme. Although at some specific number of wavelengths, the BS slightly underperforms, it significantly improves the overall performance when compared to the JIT, JET reservation schemes. Simulation results show that the overall performance of the network under BS is significantly better than the alternate schemes. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Cyclic code-shift keying (CCSK) is the baseband 32-ary symbol modulation scheme used by the Joint Tactical Information Distribution System (JTIDS), the communication terminal for Link-16. CCSK is not orthogonal and an analytic expression for the probability of symbol error for CCSK has thus far been elusive. In this paper, an analytic upper bound on the probability of symbol error of CCSK is derived for the 32-chip CCSK starting sequence chosen for JTIDS. The analytically obtained probability of symbol error is compared with two different Monte Carlo simulations for additive white Gaussian noise. The results of both simulations match the analytic results very well and show that the analytic method yields a tight upper bound. A new 32-chip CCSK starting sequence which has a smaller maximum off-peak cross-correlation value than the current JTIDS starting sequence is proposed and evaluated both analytically and by simulation. The results obtained for the new CCSK starting sequence compare favorably with the CCSK starting sequence chosen for JTIDS. Published in 2010 by John Wiley & Sons, Ltd. Cyclic code shift keying is used in important military communications systems designed for jamming resistance. This paper provides the most accurate analysis and simulation of CCSK performance to date in addition to a proposed improvement over the CCSK employed in the widely used Link-16 tactical communications system. Published in 2010 by John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The dynamics of peers, namely Churn, is an inherent property of peer-to-peer (P2P) systems and is critical to their design and evaluation. Although every excellent P2P protocol has some solution to this issue, studies on Churn are still seldom. This paper studies various factors related to Churn, and uses them to analyze and evaluate P2P protocols. Prior researches on Churn are all based on the P2P network factors in Churn environment, and their difference is whether to use these factors as predecessor references to build Churn analytical models or as successor references to test the models. According to this difference, this paper first divides various factors into two categories: impacting Churn and affected by Churn. There is a causal relationship between these two categories. Factors impacting Churn are cause, and the factors affected by Churn are effect. In this paper, we use this causality to simulate and analyze P2P Churn. Cause is used as the input data and effect is used as the output result. Second, based on the classification of Churn factors, we present a performance evaluation framework and two comparing models. Based on the framework and models, we simulate and analyze three P2P protocols and get some useful results such as the performance of these protocols under Churn, the advantage of Chord over others, and the most important factors impacting Churn. Finally, we present a method to improve recent P2P Churn models by adding some influence factors. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The paper presents analytical and simulation models to study the impact of interrupt overhead on operating system throughput of network elements such as PC-based routers, servers, and hosts when subjected to high-speed network traffic. Under such high network traffic, the system throughput will be negatively affected due to interrupt overhead caused by the incoming traffic. We first present an analytical model for the ideal system when interrupt overhead is ignored. We then present two models which describe the impact of high interrupt rate on system throughput. One model is for employing PIO in which network adapters are not equipped with DMA engines, and the other model is for employing DMA in which network adapters are equipped with DMA engines. The paper also describes detailed discrete-event simulation models for the ideal system and for systems with DMA and PIO. Simulations results as well as reported experimental measurements show that our analytical models are valid and give a good approximation. Our analysis and simulation work can be valuable in providing insight to understand and predict system behaviour, as well as improving and maintaining good host performance. The paper identifies analytically critical design operation points such as that of overload condition. The paper also proposes solutions and recommendations for improving performance. Copyright © 2005 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Based on green energy prediction and storage, a novel green base station (GBS) offloading model is proposed and can be employed with multiple objectives in this paper to save energy. By predicting the value of green energy collected by GBS and updating the residual energy of each GBS, we can obtain the maximum number of users that each GBS can offload theoretically. Then, the optimum number of users should be calculated in order to achieve different network performance. Eventually, under the restrictions of the maximum number of users and the optimum number of users, we can finish offloading for traditional base station in the network. Simulation results demonstrate that through the proposed GBS offloading model, we can fulfill compromise between maximizing green energy utilization and load balancing in the offloading process, and the effect of energy saving is remarkable. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents a new variable step-size diffusion affine projection algorithm (VSS-DAPA) to advance the filter performance of the diffusion affine projection algorithm (DAPA). The proposed VSS strategy is developed for the DAPA, which can solve the distributed estimation problem over diffusion networks well. To obtain the optimal step size reasonably, we seek the update recursion of mean-square deviation (MSD) that is suitable for the DAPA. The step size is optimally given through the minimization for the MSD of the DAPA at each iteration. The derived step size through the MSD minimization improves the filter performance with respect to the convergence and the estimation error in steady state. The results based on simulations demonstrate that the proposed VSS-DAPA performs better than the existing algorithms with a system-identification scenario in diffusion network. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Femtocell is regarded as a promising technology to enhance indoor coverage and improve network capacity. However, highly dense and self-organized femtocells in urban environment will result in serious inter-femtocell interference. To solve this problem, this paper proposes a distributed power self-optimization scheme for the downlink operation of dense femtocell networks. First, a novel convex pricing mechanism is presented to price the transmit power of femtocells and construct the utility function of femtocells. Then, a noncooperative game framework for power self-optimization of femtocells in dense femtocell networks is established on the basis of the exact potential game theory, which is demonstrated to converge to a pure and unique Nash equilibrium. Finally, combined with firefly algorithm, an effective power self-optimization algorithm with guaranteed convergence is proposed to achieve the Nash equilibrium of the proposed game. With practical LTE parameters and a 3GPP dual-strip femtocell model, simulation results show that the proposed game with convex pricing mechanism increases the femtocell network throughput by 7% and reduces the average transmit power of femtocells by 50% in dense femtocell networks, with respect to the compared schemes. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, an approach of detecting low-rate denial of service attack is proposed on the basis of principal component analysis algorithm. The proposed approach analyzes low-rate denial of service attack flows and handles complicated network flows by using principal component analysis algorithm to establish the network traffic matrix model, which is established on the basis of a large number of data acquisitions. Simulation results show that the proposed approach can predigest the high dimension vector, which is composed of networks flows, guarantee the detection precision, and reduce the computation consuming. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY Target tracking in wireless sensor networks is a well-known application. In real life scenario, target mobility can be predicted using well-known filters. In this paper, we explain an approach to model the pattern of movement of a target on the basis of target data available. This method utilizes filter techniques to predict the target and a curve-fitting algorithm to model the mobility of a target in both linear and non-linear motion patterns. Two alternate strategies to achieve mobility approximation have been proposed and compared. The efficacy of the algorithm is, further, adjudged by comparing its mobility prediction vis-a-vis the Kalman filter. Simulation results show that with sufficient data, the mobility pattern of the target can be fairly calculated even if the target moves unpredictably. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY In this paper, we investigate a communication relay placement problem to optimize the network throughput in a content-centric wireless mesh networks (WMN), in which the WMN is enhanced by including a small set of communication relays and a subset of wireless mesh routers serving as storage nodes. Specifically, we first define the communication relay placement problem in content-centric WMNs. We then model the problem as a mathematical programming and propose a linear programming approach for calculating the achievable network throughput when the positions of communication relays are fixed. Next, to optimally placing the communication relays, we formulate an integer linear programming problem and we develop an efficient near-optimal approximation algorithm based on linear programming relaxation. Finally, extensive simulation experiments have been conducted, and the results demonstrate the effectiveness of the proposed algorithms. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY Vehicular Ad Hoc Networks (VANETs), designed to ensure the safety and comfort of passengers via the exchange of information amongst nearby vehicles or between the vehicles and Roadside Units (RSUs), have attracted particular attention. However, the success of many VANET applications depends on their ability to estimate the vehicle position with a high degree of precision, and thus, many vehicle localization schemes have been proposed. Many of these schemes are based on vehicle-mounted Global Positioning System (GPS) receivers. However, the GPS signals are easily disturbed or obstructed. Although this problem can be resolved by vehicle-to-vehicle communication schemes, such schemes are effective only in VANETs with a high traffic density. Accordingly, this paper presents a VANET localization scheme in which each vehicle estimates its location on the basis of beacon messages broadcast periodically by pairs of RSUs deployed on either side of the road. In addition, three enhancements to the proposed scheme are presented for the RSU deployment, RSU beacon collisions, and RSU failures. Overall, the ns-2 simulation results show that the localization scheme achieves a lower localization error than existing solutions on the basis of vehicle-to-vehicle communications and is robust toward changes in the traffic density and the vehicle speed. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: Multicast communication constrained by end‐to‐end and interdestination delay variation is known as delay and delay variation–bounded multicast. These constraints are salient for real‐time multicast communications. In this paper, we propose a directional core selection algorithm for core selection and delay variation–bounded multicast tree generation. Another algorithm, based on k‐shortest paths, is proposed to further decrease the interdestination delay variation of the trees generated by directional core selection. We also propose the dynamic version of both algorithms that respond to dynamic join and leave requests to the ongoing multicast session by reorganizing the tree and avoiding session disruption. Simulations show that the proposed algorithms surpass existing algorithms in end‐to‐end delay, interdestination delay variation, execution time, and failure probability. [ABSTRACT FROM AUTHOR]

For the current generation of cellular communication systems, long-term evolution (LTE) has been the major protocol to support high-speed data transmission. It is critical to allocate downlink spectral resource in LTE, namely, resource blocks (RBs), but the issue is not well addressed in the standard. Therefore, the paper develops an efficient RB allocation algorithm with 4 mechanisms to improve both fairness and throughput in LTE. For fairness concern, our RB allocation algorithm uses a resource-reservation mechanism to prevent cell-edge user equipments from starvation, and a credit-driven mechanism to keep track of the amount of resource given to each user equipment. For throughput concern, it adopts both weight-assignment and RB-matching mechanisms to allocate each RB to a packet according to its flow type and length. Through simulations, we demonstrate that the proposed RB allocation algorithm can significantly increase both throughput and fairness while reducing packet dropping and delays of real-time flows, as compared with previous methods. [ABSTRACT FROM AUTHOR]

SUMMARY An improved algorithm is presented for a signal's direction of arrival estimation to reduce the computational complexity of the existing modified multiple signal classification (MMUSIC) algorithm. In this paper, FFT algorithm is introduced to narrow the searching range of the direction angle. Afterwards, a compromise approach-based SVD and orthogonal-triangular decomposition takes the place of traditional double SVDs. Then, during matrix calculation, the noise subspace is achieved for the signal's direction of arrival. Finally, the system simulation demonstrates the efficiency and reliability of this novel MMUSIC algorithm. Compared with the existing algorithm, MMUSIC effectively saves the computational complexity with the approximation estimation performance. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY The paper proposes a hierarchical and low-power IPv6-address configuration scheme for wireless sensor networks based on the cluster-tree architecture. In the scheme, a wireless sensor network is divided into multiple clusters and the generation algorithm of a cluster is proposed. A cluster-tree architecture for wireless sensor networks is presented and a layered IPv6 address format for a cluster head and a cluster member is created. The stateless address configuration strategy and the stateful address configuration strategy are effectively combined to develop the IPv6 address configuration scheme. In the scheme, the duplicate address detection of the IPv6 address assigned for a cluster member is performed in the cluster where the cluster member locates, and the IPv6 address configuration for the cluster members in the different clusters can be carried out at the same time. The paper also addresses the mobility of sensor nodes and their failure. From the theoretical and simulative perspectives, the paper analyzes the performance parameters, including duplicate address detection cost, address configuration cost and address configuration delay time, of the proposed scheme, Strong DAD and MANETConf. Analytical and simulative results show that the performance of the proposed scheme is better. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY Minimizing the schedule frame length in spatial time division multiple access networks is essential in enhancing the performance of multiplayer interactive applications in multiple-group multicasting environments. In this paper, the joint link scheduling and multiple-group communication problem in such networks is referred to as a real-time multiple-group communication tree scheduling (RMGCTS) problem in which the objective is to minimize the total schedule frame length. It is shown that the RMGCTS problem can be represented as an integer linear programming problem. Two particular RMGCTS problems are considered, namely, back-to-back RMGCTS for applications with a receiving-jitter constraint, and general RMGCTS for applications with a delay constraint. Two heuristic algorithms, designated as back-to-back scheduling and level-by-level scheduling, are proposed to provide efficient solutions of the back-to-back and general RMGCTS problems by maximizing the spatial reuse capability within each time slot, thereby minimizing the schedule frame length. The simulation results show that the proposed schemes yield an effective reduction in the length of the multicast schedule frame compared to that obtained from existing tree-based or pure-color scheduling algorithms. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY This paper is concerned with the bandwidth allocation problem for cooperative relay networks. The relay takes the roles of not only forwarding the data originated from the users but also of transmitting its own data to the access point. We focus on the interesting questions of when and how the users and the relay can both benefit from the cooperation by bandwidth allocation for relaying among the users. The bandwidth allocation problem is formulated in this paper as a Nash bargaining problem, and then the bandwidth allocation algorithm can be given on the basis of the sub-gradient method. Simulation results illustrate that users and the relay can both obtain more profits through cooperation. Copyright ©2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY The WAVE (IEEE 1609) standard and vehicular technology create a new opportunity for telematics service. Safety is one of the top issues of telematics service. In this paper, we propose a proactive safety method that can alert drivers before the accident occurs using WAVE. An algorithm named Early Collision Warning Algorithm (ECWA) was proposed in this paper. In ECWA, vehicles broadcast Relationship Information (RI) to neighboring vehicles periodically. Each vehicle calculates whether potential collisions may happen or not upon receiving RI messages. After calculation, ECWA sends warning messages to drivers if the collision will occur. ECWA allows drivers to set the warning level and warning distance by themselves. In our simulation, not only vehicles's collisions at an intersection were simulated but also the GPS error range was considered in our design. The results show that ECWA has good performance and can always alert drivers suitably if the GPS error range was small. Even though the GPS error range is large, ECWA also can enhance the hit rate of warning messages. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY A major challenge in packet-based optical networks is packet contention, which occurs when two or more packets are heading to the same output at the same time. To resolve contention in the optical domain, a fundamental approach is fiber delay-line (FDL) buffering, in which packets can be delayed for a fixed amount of time. In the literature, the performance of FDL buffering has been studied extensively. However, most existing works are based on an assumption that there is only one fiber per link in the network. In this paper, we address the architecture and performance of FDL buffers in packet-based asynchronous multifiber optical networks (PAMFONET), in which each link in the network may consist of multiple optical fibers. We propose a framework for FDL buffers in PAMFONET, in which we provide three essential architectures and corresponding packet scheduling policies. Extensive simulation results show that, with appropriate settings, the same number of FDLs can lead to better performance in multifiber networks than in single-fiber networks. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY This paper proposes a joint precoding and power allocation strategy to maximize the sum rate of multiuser multiple-input multiple-output (MIMO) relay networks. A two-hop relay link working on amplify-and-forward (AF) mode is considered. Precoding and power allocation are designed jointly at the base station (BS). It is assumed that there are no direct links between the BS and users. Under individual power constraints at the BS and relay station, precoders designed based on zero forcing, minimum mean-square error and maximum ratio transmission are derived, respectively. Optimal power allocation strategies for these precoders are given separately. To demonstrate the performance of the proposed strategies, we simulate the uncoded bit error rate performance of the underlined system. We also show the difference of the sum rate of the system with the optimal power allocation strategies and with average power transmission. The simulation results show the advantages of the proposed joint precoding and power allocation strategies as expected. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY Gang scheduling is an efficient resource management scheme for distributed systems which combines elements of time sharing and space sharing. It is a suitable technique particularly in the case when parallel tasks have to be running concurrently to make progress in communication. This paper studies the impact on scheduling performance when dynamically generated sequential gangs exist in the workload. In the case of sequential gangs, a subsequent gang can be dynamically generated after the execution of the initial gang based on affinity information which resides on the caches of the previously seized processors. The performance of different gang-scheduling algorithms is examined for various cases of workload compositions which range from cases with a low demand for dynamically generated gangs to cases with a high ratio of sequential gangs to solitary gangs. A simulation model is implemented to address associated performance issues. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY The IEEE 802.16e standard specifies the QoS support at the MAC level for wireless broadband access network. To meet the QoS requirements, an efficient scheduling algorithm at base station (BS), which is not defined in the standard, is necessary for slots allocation. In this paper, a Slot-based BS scheduling algorithm with Maximum Latency Guarantee and Capacity First (SMLG-CF) is proposed. With SMLG-CF, the connection request is satisfied with highest slot capacity first. Together with the use of dynamic sub-frame adjustment, the overall system transmission can be efficiently improved. Through the finer slots calculation and accurate transmission time scheduling, the maximum latency guarantee can be better achieved for urgent requests. In the simulation, we compare the proposed mechanism with the deficit fair priority queue scheduling algorithm and the Highest Urgency First scheduling algorithm. The simulation results reveal that SMLG-CF outperforms both algorithms from the aspect of maximum latency violation rate and average transmission rate. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY In multicarrier communication systems, a time-domain equalizer (TEQ) can be applied to shorten the channel impulse response and to eliminate inter-symbol interference (ISI). However, the presence of impulsive noise in the channel may paralyze the operation of TEQs and subsequently lead to poor error performance. In this paper, a multicarrier receiver that incorporates a constant false alarm rate algorithm and an iterative estimation technique (CFAR-IET) in conjunction with a TEQ is proposed to increase the robustness of the receiver against impulsive noise. Furthermore, an improved version of the CFAR-IET-TEQ scheme, which uses the buffering, sorting, removing and amplitude averaging (BSRA) processes, is presented. Performance comparisons of the proposed schemes with the existing Gaussian-optimized schemes are made. Simulation results show that the BSRA-IET-TEQ scheme is an effective approach to reduce symbol error rate (SER) in impulsive channels while performing satisfactorily in Gaussian channels. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY The ever-increasing share of the peer-to-peer (P2P) traffic flowing in the Internet has unleashed new challenges to the quality of service provisioning. Striving to accommodate the rise of P2P traffic or to curb its growth has led to many schemes being proposed: P2P caches, P2P filters, ALTO mechanisms and re-ECN. In this paper, we propose a scheme named 'UARA:textbfUser/ Application-aware RED-based AQM' which has a better perspective on the problem: UARA is proposed to be implemented at the edge routers providing real-time near-end-user traffic shaping and congestion avoidance. UARA closes the loopholes exploited by the P2P traffic by bringing under control the P2P users who open and use numerous simultaneous connections. In congestion times, UARA monitors the flows of each user and caps the bandwidth used by 'power users' which leads to the fair usage of network resources. While doing so, UARA also prioritizes the real-time traffic of each user, further enhancing the average user quality of experience (QoE). UARA hence centralizes three important functionalities at the edge routers: (1) congestion avoidance; (2) providing user fairness; (3) prioritizing real-time traffic. The simulation results indicate that average user QoE is significantly improved in congestion times with UARA at the edge routers. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper addresses the analytical evaluation of broadcast protocols in VANET. We focus on the most popular broadcast algorithm, which consists in the current emitter selecting the furthest receiver as the next forwarder. We propose a general framework based on point process to evaluate this protocol. The radio environment is modelled by a generic Frame Error Rate function. It enables us, through the same model, to assess the performances for different radio environments or radio technologies. We derive simple formulae for different quantities relative to the performance of the broadcast protocol: time to propagate the message, emitters' intensity, mean number of receptions for the same message, etc. Results based on the analytical model are compared with simulations using realistic vehicle traffic in order to determine the contexts for which the analytical model is relevant. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Multiuser orthogonal frequency division multiplexing (OFDM) is a promising technology to achieve high uplink/downlink (DL) capacities in the next generation broadband wireless networks such as WiMAX (Worldwide Interoperability for Microwave Access). In this paper, we investigate the DL adaptive power allocation (APA) in multiuser OFDM system from the perspective of cross-layer design. Specifically, we formulate APA as an optimization problem with the traffic profile of each user asit a priori knowledge. To solve the optimization problem, we develop a fairness-constrained optimal prioritized effective throughput (PET) strategy and the corresponding iterative algorithms, aiming at balancing the prioritized effective throughput and the linear or logarithmic user satisfaction-based fairness. Simulation results show that our proposed APA optimization approach can achieve satisfying performance. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The nodes in a wireless ad hoc network act as routers in a self-configuring network without infrastructure. An application running on the nodes in the ad hoc network may require that intermediate nodes act as routers, receiving and forwarding data packets to other nodes to overcome the limitations of noise, router congestion and limited transmission power. In existing routing protocols, the 'self-configuring' aspects of network construction have generally been limited to the construction of routes that minimize the number of intermediate nodes on a route while ignoring the effects that the resulting traffic has on the overall communication capacity of the network. This paper presents a context-aware routing metric that factors the effects of environmental noise and router congestion into a single time-based metric, and further presents a new cross-layer routing protocol, called Warp-5 (Wireless Adaptive Routing Protocol, Version 5), that uses the new metric to make better routing decisions in heterogeneous network systems. Simulation results for Warp-5 are presented and compared to the existing, well-known AODV ( Ad hoc On-Demand Distance Vector) routing protocol and the reinforcement-learning based routing protocol, Q-routing. The results show Warp-5 to be superior to shortest path routing protocols and Q-routing for preventing router congestion and packet loss due to noise. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Multicast communications concern the transfer of data among multiple users. Multicast communications can be provided at the network layer-an example is IP multicast-or at the application layer, also called overlay multicast. An important issue in multicast communications is to control how different users-senders, receivers, and delivery nodes-access the transmitted data as well as the network resources. Many researchers have proposed solutions addressing access control in IP multicast. However, little attention has been paid to overlay multicast. In this paper, we investigate the access control issues in overlay multicast and present OMAC: a new solution to address these issues. OMAC provides access control for senders, receivers, and delivery nodes in overlay multicast. The proposed architecture, which is based on symmetric key cryptosystem, centralizes the authentication process in one server whereas it distributes the authorization process among the delivery nodes. Moreover, delivery nodes are utilized as a buffer zone between end systems and the authentication server, making it less exposed to malicious end systems. To evaluate our work, we have used simulation to compare the performance of OMAC against previous solutions. Results of the simulation show that OMAC outperforms previous multicast access control schemes. Copyright © 2010 John Wiley & Sons, Ltd. This paper investigates the access control issues in overlay multicast and presents OMAC: a new architecture to address these issues. The proposed architecture, which is based on symmetric key cryptosystem, centralizes the authentication process in one server and distributes the authorization process among the multicast delivery nodes. The paper examines the security strength of OMAC and demonstrates that-based on simulation-its performance is better than a previous multicast access control solution. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents an analytical approach to model the bi-directional multi-channel IEEE 802.11 MAC protocols (Bi-MCMAC) for ad hoc networks. Extensive simulation work has been done for the performance evaluation of IEEE 802.11 MAC protocols. Since simulation has several limitations, this work is primarily based on the analytical approach. The objective of this paper is to show analytically the performance advantages of Bi-MCMAC protocol over the classical IEEE 802.11 MAC protocol. The distributed coordination function (DCF) mode of medium access control (MAC) is considered in the modeling. Two different channel scheduling strategies, namely, random channel selection and fastest channel first selection strategy are also presented in the presence of multiple channels with different transmission rates. M/G/1 queue is used to model the protocols, and stochastic reward nets (SRNs) are employed as a modeling technique as it readily captures the synchronization between events in the DCF mode of access. The average system throughput, mean delay, and server utilization of each MAC protocol are evaluated using the SRN formalism. We also validate our analytical model by comparison with simulation results. The results obtained through the analytical modeling approach illustrate the performance advantages of Bi-MCMAC protocols with the fastest channel first scheduling strategy over the classical IEEE 802.11 protocol for TCP traffic in wireless ad hoc networks. Copyright © 2010 John Wiley & Sons, Ltd. This paper presents an analytical approach to model the bi-directional multi-channel IEEE 802.11 MAC (Bi-MCMAC) protocols for ad hoc networks via stochastic reward nets. The objective is to show the performance advantages of Bi-MCMAC protocol over the classical IEEE 802.11 MAC protocol. Two different channel scheduling strategies are also presented in the presence of multiple channels with different transmission rates. The average system throughput, mean delay, and server utilization of each MAC protocol are evaluated using the SRN formalism. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Next-generation ad hoc networks need to be able to handle high mobility in order to support a wide range of emerging applications such as vehicular networks. Maintaining communication links of an established communication path that extends between source and destination nodes is a significant challenge in mobile ad hoc networks due to the movement of the mobile nodes. In particular, such communication links are often broken under a high mobility environment. Although a new communication route can be established when a break in the communication path occurs, repeatedly reestablishing new routes incurs delay and substantial overhead. To address this limitation, we introduce the Virtual Router abstraction in this paper. A virtual router is a dynamically created logical router that is associated with a particular geographical area. Its routing functionality is provided by the physical nodes (i.e. mobile devices) currently within the geographical region served by the virtual router. These physical nodes take turns in forwarding data packets for the virtual router. In this environment, data packets are transmitted from a source node to a destination node over a series of virtual routers. Since virtual routers do not move, this scheme is much less susceptible to node mobility. We give simulation results to demonstrate the effectiveness of this technique in handling high mobility. They show that the Virtual Router approach can achieve several times better performance than the traditional approach based on physical routers (i.e. relay nodes). Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper investigates the error performance of three relaying protocols with multiple decode-and-forward relays. In the first protocol, relays that can decode correctly will forward the signals from source. Nevertheless, selection cooperation (SC) and opportunistic relaying (OR) are adopted to select only a single relay to forward in the other two protocols, respectively. At sufficiently high signal-to-noise ratio, the upper bounds on bit error probability are derived for three protocols, where the developments apply for various channel fading models. Simulation results are provided to verify the tightness of the analytical bounds, and the performance comparisons among different relaying protocols are presented. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Bank communication networks support four classes of traffic: Alarm, BSC, SNA and IP traffic, with each class of traffic having different priority requirements. In this paper, a framework for the design of multiple access protocols which are capable of handling the above priority classes is introduced. Furthermore, a hybrid multiple access protocol that has been designed according to the proposed framework is presented and evaluated by means of extensive simulation results. The proposed protocol, is applicable to a broad range of prioritized LANs. Copyright © 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

QoS Routing is crucial for QoS provisioning in high-speed networks. In general, QoS routing can be classified into two paradigms: source routing and hop-by-hop routing. In source routing, the entire path to the destination node of a communication request is locally computed at the source node based on the global state that it maintains, which does not scale well to large networks. In hop-by-hop routing, a path-selecting process is shared among intermediate nodes between the source node and the destination node, which can largely improve the protocol scalability. In this paper, we present the design of hop-by-hop routing with backup route information such that each intermediate node can recursively update the best known feasible path, if possible, by collectively utilizing the routing information gathered thus far and the information that it locally stores. Such a route is kept as a backup route and its path cost is used as a reference to guide the subsequent routing process to search for a lower-cost constrained path and avoid performance degradation. In this way, the information gathered is maximally utilized for improved performance. We prove the correctness of our presented algorithm and deduce its worst message complexity to be O(∣V∣2), where ∣V∣ is the number of network nodes. Simulation results indicate that, however, the designed algorithm requires much fewer messages on average. Therefore it scales well with respect to the network size. Moreover, simulation results demonstrate that the cost performance of our algorithm is near-optimal. Copyright © 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, we describe a mechanism for adaptive transmission of multimedia data, which is based on real-time protocols. The proposed mechanism can be used for unicast or multicast transmission of multimedia data over heterogeneous networks, like the Internet, and has the capability to adapt the transmission of the multimedia data to network changes. In addition, the implemented mechanism uses an inter-receiver fairness function in order to treat the group of clients with fairness during the multicast transmission in a heterogeneous environment. The proposed mechanism uses a ‘friendly’ to the network users congestion control policy to control the transmission of the multimedia data. We implement a prototype application based on the proposed mechanism and we evaluate the proposed mechanism both in unicast and multicast transmission through a number of experiment and a number of simulations in order to examine its fairness to a group of clients and its behaviour against transport protocols (TCP) and UDP data streams. Copyright © 2003 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In our days, efficient management of the available network resources becomes a critical issue, both from a functional point of view (so that users can be provided with the bandwidth they need), and an economical point of view (so that carriers can satisfactorily and efficiently serve as many customers as possible and at the same time increase their revenue). In this paper we consider a bandwidth control scheme (i.e. managed bandwidth service) for an ATM network infrastructure which is applied to the Greek research and technology network (GRNET). We present some methods that we have tested (in a simulation setting) in order to increase the efficiency of the system and the utilization of the available bandwidth. More specifically, we consider a bandwidth-resizing algorithm for virtual paths, in order to keep the allocated bandwidth very close to the bandwidth actually used. This leads to an increased number of accepted requests and better network utilization. We, also, use the simulation results in order to get an estimation of the effective bandwidth for VBR paths that can be used in call admission. Finally, we consider a semi-offline scheme where requests are gathered and considered for acceptance in regular intervals. Simulation results show an increase in the utilization of resources. As a further improvement, we allow connections to be allocated a little before or after the time initially requested. This leads to further improvement in network utilization. All the improvement schemes were tested with the ATM-TN simulator and the results look promising. Copyright © 2003 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, we design and evaluate an Internet friendly transport-level protocol (IFTP) for solving the TCP-friendly problem. IFTP has two modes of operation. In the standard mode, the IFTP connection faithfully emulates the behaviour of TCP in order to roughly obtain a bandwidth equal to that of a TCP connection. In the extended mode, a simple modification is used to grant QoS-differentiated services to selected connections. Connections running in the extended mode can get enhanced bandwidth while still emulating the general behaviour of TCP. We develop an analytical model for the congestion control mechanism of IFTP. We also derive analytically the amount of bandwidth that IFTP may be able to claim from TCP in ideal and non-ideal environments. We evaluate IFTP through simulation and prove its TCP friendliness as well as provide performance results on some of the important metrics such as packet delay, delay jitter, packet loss and link utilization. Copyright © 2002 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]