ALBERT

Description: In an amplify-and-forward cooperative network, a closed-form expression of the a priori distribution of the complex-valued gain of the global relay channel is intractable, so that a priori information is often not exploited for estimating this gain. Here, we present two iterative channel gain and noise variance estimation algorithms that make use of a priori channel information and exploit the presence of not only pilot symbols but also unknown data symbols. These algorithms are approximations of maximum a posteriori estimation and linear minimum mean-square error estimation, respectively. A substantially reduced frame error rate is achieved as compared to the case where only pilot symbols are used in the estimation.

Description: An important challenge in the domain of vehicular ad hoc networks (VANET) is the scalability of data dissemination. Under dense traffic conditions, the large number of communicating vehicles can easily result in a congested wireless channel. In that situation, delays and packet losses increase to a level where the VANET cannot be applied for road safety applications anymore. This paper introduces scalable data dissemination in vehicular ad hoc networks (SDDV), a holistic solution to this problem. It is composed of several techniques spread across the different layers of the protocol stack. Simulation results are presented that illustrate the severity of the scalability problem when applying common state-of-the-art techniques and parameters. Starting from such a baseline solution, optimization techniques are gradually added to SDDV until the scalability problem is entirely solved. Besides the performance evaluation based on simulations, the paper ends with an evaluation of the final SDDV configuration on real hardware. Experiments including 110 nodes are performed on the iMinds w-iLab.t wireless lab. The results of these experiments confirm the results obtained in the corresponding simulations.

Description: Adaptive spatial multiplexing (SM) Multiple Input Multiple Output (MIMO) techniques enhance the spectral efficiency of wideband wireless communications in favorable radio channel conditions. In this study, we show the benefits of combining a traditional fixed-beam scheme and multiuser opportunistic radio resource allocation in space-time-frequency domains. This combining is feasible in wideband Orthogonal Frequency Domain Multiple Access (OFDMA) systems such as the Universal Mobile Telecommunications System (UMTS) Long Term Evolution (LTE). This study brings novel knowledge which indicates that an orthogonal fixed beam approach benefits from opportunistic radio resource allocation clearly more than a conventional antenna domain approach in frequency-selective radio channels. It was found out that the fixed beam radio link performance is enhanced in wideband adaptive radio links due to the fact that orthogonal beams reduce correlation between the MIMO channels in the allocated sub-bands. Moreover, beamforming gains bring higher Eigenvalues of the MIMO channel matrix in the opportunistically selected sub-bands. It is shown that the fixed beam deployment changes the distribution of the MIMO channel correlation values and Eigenvalues in a manner which enhances opportunistic multiuser gains in wideband time-frequency-selective MIMO radio channels. Simulation results with 2 x 2 spatial multiplexing in an OFDMA uplink indicate that the proposed beam domain scheme gives up to 80% data throughput gain over the corresponding antenna domain scheme in a pedestrian microcell environment.

Description: Dynamic adaptive streaming over HTTP (DASH) has become a promising solution for video delivery services over the Internet in the last few years. Currently, several video content providers use the DASH solution to improve the users' quality of experience (QoE) by automatically switching video quality levels (VQLs) according to the network status. However, the frequency of switching events between different VQLs during a video streaming session may disturb the user's visual attention and therefore affect the user's QoE. As one of the first attempts to characterize the impact of VQL switching on the user's QoE, we carried out a series of subjective tests, which show that there is a correlation between the user QoE and the frequency, type, and temporal location of the switching events. We propose a novel parameter named switching degradation factor (SDF) to capture such correlation. A DASH algorithm with SDF parameter is compared with the same algorithm without SDF. The results demonstrate that the SDF parameter significantly improves the user's QoE, especially when network conditions vary frequently.

Description: With the development of mobile internet, protecting location privacy has already been an importantissue. Based on previous studies and the drawback of traditional algorithms, the paper proposes anovel algorithm for protecting location privacy. The algorithm is based on the voronoi map of aroad network, considers the problem of side-weight inference, and utilizes the information entropy asmetrics. Meanwhile, the algorithm can defense the attack of side-weight inference and replay. Lastly,we verified the algorithm based on the real data of the road network. Results of experiences show thatthe improved algorithm has the better performance on some key performance metrics.

Description: In this paper, we propose a model for mobile application profiles, wireless interfaces, and cloud resources. First, an algorithm to allocate wireless interfaces and cloud resources has been introduced. The proposed model is based on the wireless network cloud (WNC) concept. Then, considering power consumption, application quality of service (QoS) profiles, and corresponding cost functions, a multi-objective optimization approach using an event-based finite state model and dynamic constraint programming method has been used to determine the appropriate transmission power, process power, cloud offloading and optimum QoS profiles. Numerical results show that the proposed algorithm saves the mobile battery life and guarantees both QoS and cost simultaneously. Moreover, it determines the best available cloud server resources and wireless interfaces for applications at the same time.

Description: In this paper, we present a new queueing model providing the accurate average system time forpackets transmitted over a cognitive radio (CR) link for multiple traffic classes with the preemptiveand non-preemptive priority service disciplines. The analysis considers general packet service time,general distributions for the channel availability periods and service interruption periods, and aservice-resume transmission. We further introduce and analyze two novel priority service disciplinesfor opportunistic spectrum access (OSA) networks which take advantage of interruptions to preemptlow priority traffic at a low cost. Analytical results, in addition to simulation results to validate theiraccuracy, are also provided and used to illustrate the impact of different OSA network parameters onthe average system time. We particularly show that, for the same average CR transmission linkavailability, the packet system time significantly increases in a semi-static network with longoperating and interruption periods compared to an OSA network with fast alternating operating andinterruption periods. We also present results indicating that, due to the presence of interruptions,priority queueing service disciplines provide a greater differentiated service in OSA networks than intraditional networks. The analytical tools presented in this paper are general and can be used toanalyze the traffic metrics of most OSA networks carrying multiple classes of traffic with priorityqueueing service differentiation.

Description: Multiuser cooperative communication significantly improves the performance of wireless communication networks. One key challenge of multiuser cooperative communication is how to design a cooperative mechanism to incentivize potential relay nodes to help a source node in its data transmission. In this paper, to address this problem, a contract-based principal-agent framework is proposed in the context of a cognitive-radio-based wireless relaying networks in which the sources' wireless characteristics constitute hidden information which is not known by the relay. The problem is modeled as a monopolist's problem, in which a mobile relay node acts as the principal who designs incentive-compatible (IC) and individually rational (IR) contract items, consisting of a set of rate-price pairs. Subsequently, contract items can be broadcast by the relay to nearby mobile users that want to send data. Once these sources optimally select an item and notify the relay that they are willing to accept it, the relay then chooses one source based on the highest revenue for which to provide service. The cooperative gain, relay's revenue, and expected data rate are characterized for the optimal contract under complete information and incomplete information. Theoretical analysis and numerical results show that this pricing mechanism can lead to a win-win situation in which source nodes get good communication service and relay nodes maximize their own profit that can, in turn, be used to purchase the relay service of other nodes when needed in the future. Moreover, the proposed mechanism is shown to also exhibit other important features such as low complexity and low signaling overhead.

Description: The paper presents a method for constructing space-time block codes for multiple-input multipleoutputchannels by concatenating orthogonal designs with the so-called diversity transform. Relyingon unitary transforms, the diversity transform increases the channel alphabet without sacrificing informationrate, bandwidth, or Euclidean distance. The distribution of the resulting channel alphabetis shown to quickly become Gaussian-like. Specific code matrices are constructed and optimizedbased on the cutoff rate. Both optimum and, reduced-complexity, suboptimum detection algorithmsare presented. Simulation results are provided for demonstrating the gains attainable when using theproposed codes.

Description: Digital image splicing blind detection is becoming a new and important subject in information security area. Among various approaches in extracting splicing clues, Markov state transition probability feature based on transform domain (discrete cosine transform or discrete wavelet transform) seems to be most promising in the state of the arts. However, the up-to-date extraction method of Markov features has some disadvantages in not exploiting the information of transformed coefficients thoroughly. In this paper, an enhanced approach of Markov state selection is proposed, which matches coefficients to Markov states base on well-performed function model. Experiments and analysis show that the improved Markov model can employ more useful underlying information in transformed coefficients and can achieve a higher recognition rate as results.

Description: Multi-channel wireless ad hoc networks enhance network capacity with the use of available channelsin parallel but should strike a balance between maintaining network connectivity and maximizingutilization of different channels. Also, a promising wireless multi-channel ad hoc network shouldbe cognitive to interference from various wireless devices operating on industrial, scientific, andmedical bands effectively by scavenging less loaded channels dynamically using periodic spectrumsensing and distributed channel selection algorithm. In this paper, we study cross-layer fair ratecontrol problems for hybrid channel assignment-based multi-channel ad hoc networks in the cognitivecontext. We first identify two inherent constraints which are specific to multi-channel multi-radiowireless ad hoc networks and primary user interference. We then formulate a fair rate control problemby exploiting the network utility maximization framework and propose a price-based distributedsolution. We investigate in detail the convergence property of the distributed solution via simulation ona grid topology. We also show its convergence in adaptation to the change in primary user interferencein the cognitive context. We present a performance comparison study with a generic class of existingworks in the literature.

Description: Wireless sensor networks (WSNs) are being used for many applications ranging from mobile target surveillance to intelligent home networking. Due to the sensitive nature of the data transmitted by these applications, appropriate protection mechanisms are needed to prevent attackers from exploiting the weaknesses of the radio links. In this paper, we propose a novel group key management scheme called DynTunKey (dynamic tunneling and group key management protocol). This paper investigates the use of secure tunnels as a solution to improve the protection of WSNs. We propose a tunneling scheme that conforms to the security requirements of WSNs while having lesscomputational and network overhead. We also propose a solution for a dynamic integration in the secured communication of a newly deployed sensor. A set of experiments has been conducted to assess the performance of the proposed scheme with regard to recent key management protocol and to traditional tunnels built using the IPSec protocol. We found that our protocol considerably reduces the number of transmitted messages as well as the computational load, which makes it suitable for WSNs. We tested the proposed protocol considering two models of mobility of the targets which are respectively the Random Walk model and the Gauss Markov model.

Description: An improved adaptive filtering (IMPNLMS+) algorithm has been proposed for non-sparse impulse responses by incorporating an adaptive parameter mu of the mu-law compression into the improved mu-law PNLMS algorithm (IMPNLMS) algorithm. It not only achieves optimal step-size control factors but also overcomes that the convergence of classical mu-law PNLMS (MPNLMS) is even slower than conventional NLMS algorithm for dispersive channels. In this paper, we propose IMPNLMS++ algorithm, where normalized algorithm is analyzed to reduce computational complexity of proposed improved mu-law PNLMS (IMPNLMS+) algorithm. The validity has been proved by the simulation results.

Description: Network traffic modeling significantly affects various considerations in networking, including network resource allocation, quality of service provisioning, network traffic management, congestion control, and bandwidth efficiency. These are very important issues in network protocol design, too. In this paper, a comprehensive comparison of modeling approaches of adaptive neuro fuzzy inference system (ANFIS) and autoregressive integrated moving average (ARIMA) for modeling of wireless network traffic in terms of typical statistical indicator and computational complexity has been attempted. ARIMA has been widely used in this area for past many years. On the other hand, ANFIS is comparatively new, and no network traffic modeling using ANFIS was attempted until recently to the best of our knowledge. At the same time, a detailed comparative performance evaluation of ANFIS with other modeling approaches in traffic modeling could not be found in existing literature. Reportedly, ANFIS provides a good precision in prediction in terms of statistical indicators and also gives effective description of network conditions at different times. However, the computational complexity of ANFIS for traffic modeling is a major concern and deserves a closer inspection. In our case of wireless network traffic, as a final result, we find that ANFIS model performs better than the best ARIMA model in three different scenarios.

Description: In this paper, we consider the problem of building a secure network against node conspiracy attack that based on network segmentation. As we know, network coding has demonstrated its great application prospects in wireless sensor network (WSN) transmission. At the same time, it is facing a variety of security threats, especially conspiracy attack. In existing research, secure coding design strategies are much more than secure topological structure. In this background, a weakly secure scheme is proposed from the perspective of topology and network segmentation. Based on the network segmentation and topology design, the network coding transmission is weakly secure. We conduct a simulation to show that the proposed scheme can efficiently prevent conspiracy attack.

Description: A terahertz (THz) radar provides the possibility of higher precision imaging due to the wider bandwidth. A summary of a THz imaging radar system is presented with emphasis on THz radar component design, system design, and detective imaging. In this article, we introduce a linear frequency-modulated continuous wave (LFMCW) radar system with a 4.8-GHz bandwidth and theoretical resolution of 3.125 cm. The heterodyne RF receiver structure is applied to the system to reduce the sampling rate. A non-linear correction method is applied to compensate the range backscatter signal. With the presented LFMCW radar system, high-resolution images (3.5 cm × 3.5 cm) are achieved using the ISAR imaging technique. The experiments performed on the real LFMCW radar data have shown the capability of high-resolution imaging.

Description: In the paper, we research on the performance of time-triggered Ethernet based on network calculus. Three kinds of data with different priority are imported to research on time-triggered Ethernet. Firstly, we adopt network calculus to obtain the theory-bound value of the network performance parameters. Then, we design and implement the time-triggered Ethernet clock synchronization, redundancy fault-tolerant, multi-data communication, service-performance model, node model, and network model successfully in two different topologies. Lastly, we compare the simulation value with the network calculus value and obtain the comparison result. The result shows that the performance parameters of time-triggered Ethernet well meet the theory value, and time-triggered Ethernet specification is feasible.

Description: The rapid growth of mobile communication and the proliferation of smart phones have drawn significant attention to location-based services (LBS). The Wi-Fi positioning system (WPS) is a newly attractive method as a widely applicable positioning technique in LBS. In WPS, the received signal strength indication (RSSI) data of all Wi-Fi access points (APs) are measured, and stored in a huge database, as a form of radio fingerprint map. Because of the millions of APs in urban areas, radio fingerprint data are seriously contaminated. Therefore, we present a coherent filtering method for radio fingerprint data. All fingerprints used in the developed test bed are harvested from actual radio fingerprint measurements taken throughout Seoul, Korea. This demonstrates the practical usefulness of the proposed methodology.

Description: Identification of traffic flow is very important since it can help provide dynamic navigation and optimize the performance of vehicular ad hoc networks (VANETs). The existing ways for estimating the traffic state mostly show the drawbacks of large computation and hard implementations. In this paper, we propose a self-organizing way to collect traffic information through VANET communications without any aid of infrastructures. Then, a method based on fuzzy logic is presented to predict the phase of traffic flow timely. This method shows the advantages of easier implementations and less computation, and it can adapt dynamically to take more traffic factors into consideration if needed. With the knowledge of current traffic status, a new routing algorithm for vehicular communication on highways is proposed, which can be adaptive to different phases of traffic flow and guarantee reliable transmission in different environments. The simulation results show that our self-organizing proposal gains satisfactory accuracy according to the real-time identification of traffic flow, and the network performance of the adaptive routing algorithm is improved compared with traditional routing algorithms in terms of packet delivery ratio and throughput; at the same time, the end-to-end delay is still within an acceptable level.

Description: We propose a robust beamforming design for underlay cognitive radio networks where multiple secondarytransmitters communicate with corresponding secondary receivers and coexist with a primarynetwork. We consider a scenario where all transmitters have multiple antennas and all primary andsecondary receivers are equipped with a single antenna. The main focus is to design the optimaltransmit beamforming vectors for secondary transmitters that maximize the minimum of the receivedsignal-to-interference-plus-noise ratios of the cognitive users. The interference powers to the primaryreceivers are kept below a threshold to guarantee that the performance of the primary network doesnot degrade due to the secondary network. Imperfect channel state information (CSI) in all relevantchannels are considered, and a bounded ellipsoidal uncertainty model is used to model the CSI errors.We recast the problem in the form of semidefinite program and an iterative algorithm based on thebisection method is proposed to achieve the optimal solution. Further, we propose upper and lowerbounds for the optimal value of the considered problem, which provides better initialization for thealgorithm. Numerical simulations are conducted to show the effectiveness of the proposed methodagainst the non-robust design.

Description: One of the critical middleware services for sensor networks is the time synchronization, which provides supports to different applications. Synchronization protocols used for Internet and LANs are not appropriate in the sensor networks for the high-density and limited energy resource. This paper describes two-hop time synchronization (text-to-speech (TTS)) that aims at reducing the synchronization overhead and providing more accurate network-wide synchronization. The synchronization message exchanges are minimized by making full use of sensors' broadcast domain and enlarging the common node synchronization range in multi-hop scenarios. By halving synchronization hops, the TTS achieves high multi-hop synchronization precision. The proposed protocol contains single-hop synchronization model, multi-hop synchronization algorithm, and a power control scheme. We prove that the extension of single-hop TTS to network-wide synchronization is NP-complete. The complexity and convergence time of multi-hop TTS are analyzed in detail. We simulate TTS on MATLAB and show that it requires minimal overhead and convergence time compared with other protocols. We also implement TTS on common sensors and its multi-hop synchronization error is less than that of receiver-receiver synchronization (R-RS).

Description: In this paper, we present a data gathering technique for sensor networks that exploits correlation betweensensor data at different locations in the network. Contrary to distributed source coding, ourmethod does not rely on knowledge of the source correlation model in each node although this knowledgeis required at the decoder node. Similar to network coding, our proposed method (which we callQuantized Network Coding) propagates mixtures of packets through the network. The main conceptualdifference between our technique and other existing methods is that Quantized Network Codingoperates on the field of real numbers and not on a finite field. By exploiting principles borrowed fromcompressed sensing, we show that the proposed technique can achieve a good approximation of thenetwork data at the sink node with only a few packets received and that this approximation gets progressivelybetter as the number of received packets increases. We explain in the paper the theoreticalfoundation for the algorithm based on an analysis of the restricted isometry property of the correspondingmeasurement matrices. Extensive simulations comparing the proposed Quantized NetworkCoding to classic network coding and packet forwarding scenarios demonstrate its delay/distortionadvantage.

Description: This paper considers a multi-cell relay-aided orthogonal frequency division multiple access (OFDMA)downlink system, in which all stations are coordinated by a central controller for resource allocation(RA). The decode-and-forward (DF) protocol with opportunistic relaying (OR) and high spectrumefficiency (HSE) is applied. The problem of maximizing the weighted sum of per cell min-rate(WSMR) with per-cell total power constraints is formulated, and its per-cell maximum fairnessproperty is proven. An iterative RA algorithm is proposed to optimize mode selection (decisionwhether the relay should help or not), subcarrier assignment (MSSA) and power allocation (PA)alternatively. Each iteration is composed of the MSSA stage and the PA stage. During the MSSAstage, the original problem is decoupled into mixed integer linear programs (MILPs) with the tentativePA results, which can be solved by typical MILP solvers. To solve the MILPs more efficiently inpolynomial time, a randomized rounding-based MSSA (RR-MSSA) algorithm and a direct roundingbasedMSSA (DR-MSSA) algorithm are further proposed. During the PA stage, an algorithm basedon single condensation and geometric programming (SCGP) PA is designed to optimize PA with thetentative MSSA results. The convergence and the per-cell user fairness of the proposed RA algorithmare proven. Finally, the performance of the RA algorithm and the benefits of using OR and the HSEprotocol are illustrated through numerical experiments.

Description: Cloud computing is a style of computing in which dynamically scalable and other virtualized resources are provided as a service over the Internet. The energy consumption and makespan associated with the resources allocated should be taken into account. This paper proposes an improved clonal selection algorithm based on time cost and energy consumption models in cloud computing environment. We have analyzed the performance of our approach using the CloudSim toolkit. The experimental results show that our approach has immense potential as it offers significant improvement in the aspects of response time and makespan, demonstrates high potential for the improvement in energy efficiency of the data center, and can effectively meet the service level agreement requested by the users.

Description: This work addresses opportunistic distributed multiuser scheduling in the presence of a fixed packet deadline delay constraint. A threshold-based scheduling scheme is proposed which uses the instantaneous channel gain and buffering time of the individual packets to schedule a group of users simultaneously in order to minimize the average system energy consumption while fulfilling the deadline delay constraint for every packet. The multiuser environment is modeled as a continuum of interference such that the optimization can be performed for each buffered packet separately by using a Markov chain where the states represent the waiting time of each buffered packet. We analyze the proposed scheme in the large user limit and demonstrate the delay-energy trade-off exhibited by the scheme. We show that the multiuser scheduling can be broken into a packet-based scheduling problem in the large user limit and the packet scheduling decisions are independent of the deadline delay distribution of the packets.

Description: ZigBee hierarchical tree routing protocol (HRP; ZigBee Alliance, San Ramon, CA, USA) provides a simple but reliable topology. However, the transmission routes are not always efficient, and the links are fixed after they were determined during the network initialization. In this paper, we propose an adaptive routing optimization and energy-balancing algorithm in ZigBee hierarchical networks. In our routing algorithm, the parent node could adaptively maintain its child's links for lower network load, and all the information needed can be obtained from a neighbour table to avoid introducing extra communication overhead. Such algorithm makes ZigBee's hierarchical topology to adaptively maintain and optimize the routing paths during its lifetime, and an address reassignment mechanism is also introduced to ensure that our algorithm follows ZigBee specification. In addition, an energy-balancing algorithm is also proposed to reduce the power cost of low-battery device. Simulation results show that our routing scheme has better performance with lower average transmission hops and network load, and our energy-balancing algorithm could reduce the power consumption of low-battery device.

Description: In hardware, packet loss may happen due to overflow at a finite-depth transmit buffer in addition to the packet corruption in the channel. To reduce such losses and further improve spectral efficiency via rate selection, we exploit either statistical or instantaneous knowledge of transmit buffer occupancy and source packet distribution in IEEE 802.11-based systems, which have highly variable frame durations. We consider a traditional method of rate adaptation based on channel quality information and evaluate the throughput gain in hardware when the buffer occupancy and source packet distribution information are known. Our optimization objective is to maximize the throughput with constant transmit power since most wireless standards (e.g., 802.11, Bluetooth, ZigBee) operate in this manner. We study both cases with and without probe packets during the transmission. By evaluating the effect of diverse buffer sizes with different packet arrival distributions, both our theoretical analysis and our experimental results show that the throughput can be improved as much as 35% when the source packet distribution and buffer status information are exploited.

Description: Vehicular ad hoc networks (VANETs) are going to be an important communication infrastructure in our moving life. The design of routing protocols in VANETs is a significant and necessary issue for supporting VANET-based applications. However, due to high mobility, frequent link disconnection, and uneven distribution of vehicles, it becomes quite challenging to establish a robust route for delivering packets. This paper presents a connectivity-aware intersection-based routing (CAIR) protocol to address these problems by selecting an optimal route with higher probability of connectivity and lower experienced delay; then, geographical forwarding based on position prediction is used to transfer packets between any two intersections along the route. Simulation results show that the proposed protocol outperforms existing routing protocols in terms of data delivery ratio and average transmission delay in typical urban scenarios.

Description: In this paper, we investigate the utility-based resource allocation problem at a base station in high-speed railway (HSR) wireless networks, jointly taking into account the power allocation along the time and the packet allocation among services. The problem to maximize the total utility under the average power constraint is formulated as a mixed-integer non-linear programming (MINLP) problem. Through the integer constraint relaxation, the MINLP problem can be simplified into a convex optimization problem. The detailed analysis reveals that the relaxed problem can be equivalently decomposed into power allocation problem along the time and packet allocation problem among services, which can reduce the problem size. When the optimality of the relaxed problem is achieved, the power allocation along the time and the packet allocation along the time for each service are both proportionally fair. Since the integer relaxation causes a non-integer solution not implementable in practice, a greedy algorithm is proposed to obtain a near-optimal integer solution of the MINLP problem. Finally, the performance of the proposed algorithm is analyzed by simulations under realistic conditions for HSR wireless networks.

Description: We propose a novel workload-dependent queuing model for a wireless router link which employs active queue management (AQM) and is offered with a number of persistent Transmission Control Protocol (TCP) flows. As opposed to existing work that focus only on the average queue occupancy as the performance metric of interest, the proposed analytical method obtains the more information-bearing steady-state queue occupancy distribution of the wireless AQM link. Simulations are performed to demonstrate the accuracy of the proposed model in both wireline and wireless scenarios. With the intention of maximizing TCP throughput, this analytical method is used to obtain guidelines for setting the target wireless packet error rate (PER) for a PER-based traffic-agnostic link adaptation scheme.

Description: This paper focuses on a robust distributed power allocation scheme for downlink two-tier heterogeneous networks (HetNets). The objective is to maximize the network aggregate utility of femtocell users (FUEs) which factors the fairness between users under the constraint of not causing serious interference to existing macrocell users (MUEs). Being impractical for different nodes to cooperate in HetNets to obtain precise estimated values of the channel gains between them, it is a challenge to guarantee the performance of the power allocation algorithm by using existing methods. This work makes a step forward in the direction of conquering this challenge by taking into account channel uncertainty, and the robust counterpart of nominal problem, without channel uncertainty, is framed by using worst-case robust optimization theory. To make the robust counterpart computationally tractable, we exploit its convexity and derive that the channel uncertainties between a FUE and nearby femtocell base stations (FBSs) fall into water-filling form being related to the received power from interference sources. Based on the inherent relationship between channel uncertainty and received power, we design a distributed algorithm which merely needs to solve a deterministic problem. The algorithm is devised based on alternating direction method of multipliers (ADMM) with a fast convergence speed. The simulation results demonstrate the robustness of our proposed approach, and the corresponding cost of robustness is investigated.

Description: Congestion is a challenging problem for sensor networks because it causes the waste ofcommunication and reduces energy efficiency. Compared to traditional wireless sensor networks, theprobability of congestion occurrence in wireless multimedia sensor networks is higher due to thehigh volume of data arising from multimedia streaming. In this article, problems for multimediatransmission over wireless multimedia sensor networks are examined and sensor fuzzy-based imagetransmission (SUIT); a new progressive image transport protocol is proposed as a solution. SUITprovides fuzzy logic-based congestion estimation and an efficient congestion mitigation techniquewhich decreases the image quality on-the-fly to an acceptable level. In case of congestion, SUITdrops some packets of the frames in a smart way and thus transmits frames to the sink with lower, butacceptable quality. In this way, SUIT improves the continuity of the video streaming. We evaluatethe performance of SUIT by comparing it with two different competitors. The first one is an exampletransport protocol, namely Fuzzy Logic-Based Congestion Estimation. The second one is a bufferoccupancy-based congestion control mechanism which is commonly used in previous studies.According to the simulation results, SUIT provides better energy consumption, frame delivery, frameloss and frame latency performance than its competitors.

Description: In a fire rescue operation, a fast, reliable, and robust communication system is needed to quickly take control of the emergent situation. One of the most important issues in firefighter communication networks (FCNs) is the design of a specialized routing protocol that caters to the specific needs of the fire rescue application. This paper proposes a reliable, energy-balancing, multi-group (REM) routing protocol for an FCN. Since firefighters work in groups, a cluster-based hierarchical approach was adopted. REM is intended to achieve reliability and energy balancing in data communication by incorporating metric-based cluster head (CH) selection, CH rotation among cluster members, and a routing algorithm. Within a cluster, the node with highest metric value based on residual energy and number of connections is chosen as the CH. The CH's responsibilities are rotated periodically among the cluster members. REM chooses nodes with a higher metric based on residual energy, number of connections, and number of hops to the base station (BS) as the next hop for forwarding data to the BS. This helps to achieve reliability, less delay, and energy balancing when compared with other routing schemes, as evident from the simulation results.

Description: The 3D Multiple-input multiple-output (MIMO) code is a robust and efficient space-time block code(STBC) for the distributed MIMO broadcasting but suffers from high maximum-likelihood (ML) decodingcomplexity. In this paper, we first analyze some properties of the 3D MIMO code to show thatthe 3D MIMO code is fast decodable. It is proven that the ML decoding performance can be achievedwith a complexity of O(M{4.5}) instead of O(M^8) in quasi-static channel with M-ary square QAMmodulations. Consequently, we propose a simplified ML decoder exploiting the unique properties ofthe 3D MIMO code. Simulation results show that the proposed simplified ML decoder can achievemuch lower processing time latency compared to the classical sphere decoder with Schnorr-Euchnerenumeration.

Description: In this paper, we aim to address the cross-layer interference in the heterogenous cellular network (HetNet). In order to exploit the overlapping characteristics of the HetNet coverage and achieve a good trade-off between the interference coordination gain and the cost, an area-classified interference coordination strategy is first proposed. The basic idea is that coverage of the HetNet is classified into four different areas such that area-specific interference coordination can be used to increase the cross-layer cooperation efficiency. A new steepest slope method based on relative cooperation gain is proposed to realize efficient area classification. Then, a coordinated beamforming scheme based on area-specific limited feedback is proposed to examine the effectiveness of this new strategy. It is shown that the proposed scheme could increase the success rate of user pairing and thus improve the throughput performance, with reduced feedback overhead in contrast to existing schemes. Its effectiveness is finally verified via numerical simulations.

Description: This paper considers multi-cell decode-and-forward (DF) relay-aided orthogonal frequency divisionmulti-access (OFDMA) downlink systems, in which all sources and relays are coordinated by acentral controller for resource allocation (RA). The improved subcarrier pair-based opportunistic DFrelaying protocol proposed and studied in the IEEE International Conference on Communications,Beijing, 3795-3800, 2008 and IEEE Trans. Signal Process. 61:2512-2524, 2013 is applied. Thisprotocol has a high spectrum efficiency (HSE) in the sense that all unpaired subcarriers are utilizedfor data transmission during the second time slot (TS). In particular, the sum (over all cells and alldestinations) rate maximized problem with a total power constraint in each cell is formulated. Tosolve this problem, an iterative RA algorithm is proposed to optimize mode selection (decisionwhether the relay should help or not), subcarrier assignment and pairing (MSSAP) and powerallocation (PA) in an alternate way. As for the MSSAP stage of each iteration, the formulatedproblem is decoupled into subproblems with the tentative PA results. Each subproblem can be easilysolved by using the optimal results of a linear assignment problem (LAP), which is then solved bythe Hungarian Algorithm in polynomial time. As for the PA stage of each iteration, an algorithmbased on single-condensation and geometric programming (SCGP) is proposed to optimize PA inpolynomial time with the tentative MSSAP results. The proposed algorithm is coordinate ascent(CA)-based and therefore can reach a local optimum in polynomial time. Finally, the convergenceand effectiveness of the proposed algorithm, the impact of relay position and total power on thesystem performance, and the benefits of using subcarrier pairing (SP) and the HSE protocol areillustrated through numerical experiments.

Description: Spectrum sensing has been identified as the key step of the cognition cycle and the most important function for the establishment of cognitive radio. In this paper, a blind cyclostationary feature detector, which is based on the symmetry property of cyclic autocorrelation function (SP-CAF), is implemented and tested using universal software radio peripheral platform and GNU Radio open-source software development toolkit. Performance of the SP-CAF is compared to the classical energy detector via various tests conducted in real scenarios where both detection algorithms are employed to blindly sense the spectrum for opportunistic access. This study shows that the blind cyclostationary feature detector outperforms the classical energy detector while guaranteeing acceptable complexity and low sensing time. Moreover, different experimental results indicate that the blind sensing detector can achieve high detection probability at a low false alarm probability under real channel conditions and low signal-to-noise ratio.

Description: The deployment of antenna subset selection on a per-subcarrier basis in MIMO-OFDM systems could improve the system performance and/or increase data rates. This paper investigates this technique for the MIMO-OFDM systems suffering nonlinear distortions due to high-power amplifiers. At first, some problems pertaining to the implementation of the conventional per-subcarrier antenna selection approach, including power imbalance across transmit antennas and noncausality of antenna selection criteria, are identified. Next, an optimal selection scheme is devised by means of linear optimization to overcome those drawbacks. This scheme optimally allocates data subcarriers under a constraint that all antennas have the same number of data symbols. The formulated optimization problem to realize the constrained scheme could be applied to the systems with an arbitrary number of multiplexed data streams and with different antenna selection criteria. Finally, a reduced complexity strategy that requires smaller feedback information and lower computational effort for solving the optimization problem is developed. The efficacy of the constrained antenna selection approach over the conventional selection approach is analyzed directly in nonlinear fading channels. Simulation results demonstrate that a significant improvement in terms of error performance could be achieved in the proposed system with a constrained selection compared to its counterpart.

Description: Bit-interleaved coded modulation with iterative decoding (BICM-ID) is investigated for bandwidth efficient transmissions, where the error performance can be improved by employing a suitable symbol mapping. In this paper, we introduce a low-complexity irregular mapping optimization for BICM- ID with irregular doping and 8-ary phase-shift keying (8PSK) modulation over both additive white Gaussian noise (AWGN) and Rayleigh fading channels, for the purpose of achieving near-capacity performances. The Euclidean distance spectrum and the extrinsic information transfer (EXIT) chart analysis are aided for the proposed optimization to provide design guidelines of mappings. The bit error rate (BER) results demonstrate that the BICM-ID system with the proposed optimal irregular mapping and doping outperforms the other typical symbol mappings, and yields a gain of about 0.1 and 0.5 dB for AWGN and Rayleigh fading channels, respectively. Moreover, it is only about 0.5 and 0.73 dB away from the discrete-input continuous-output memoryless channel (DCMC) capacity limits of AWGN and Rayleigh fading channels, respectively, at the BER of 10-4 and for the spectral efficiency of 2 bits/channel use.

Description: A word error rate (WER) reducing approach for a hybrid iterative error and erasure decoding algorithm for low-density parity-check codes is described. A lower WER is achieved when the maximum number of iterations of the min-sum belief propagation decoder stage is set to certain specific values which are code dependent. By proper choice of decoder parameters, this approach reduces WER by about 2 orders of magnitude for an equivalent decoding complexity. Computer simulation results are given for the efficient use of this hybrid decoding technique in the presence of additive white Gaussian noise.

Description: This paper studies the auction-driven dynamic spectrum access in cognitive radio networks with heterogeneous secondary users, who have different risk attitudes. First, a game theoretic framework is established for auction-driven dynamic spectrum access in cognitive radio networks. The utility functions and bidding strategies of heterogeneous secondary users are defined, and the parameterized auction mechanisms of primary user are also introduced. Then, we formulate the auction-driven dynamic spectrum access problem as a finite discrete game with a mixed- or pure-strategy Nash equilibrium solution. We study the existence and uniqueness properties of the pure-strategy Nash equilibrium in the defined game. Next, we propose a distributed learning automata algorithm (DLA) to attain the Nash equilibrium of the defined game with limited feedback. The adaptive mechanism design is realized in the updating procedure of our DLA algorithm. We further prove that our DLA algorithm converges to a Nash equilibrium of the defined game. Finally, simulation results show that our DLA algorithm is efficient and outperforms the dynamic spectrum access schemes with fixed auction mechanism.

Description: Communication channels not only suffer from ambient noise but also from deterministicinterference. In this paper, we consider signal-to-noise ratio (SNR) estimation in the presence ofconstant deterministic interference. A maximum likelihood (ML) non-data-aided algorithm isproposed for SNR estimation. We first consider a real-valued model and then extend this to acomplex-valued model. The proposed algorithm applies an iterative approach initialized withapproximate closed form estimates so as to guarantee stability and convergence. Furthermore, theCramer-Rao bound (CRB) is also derived as the theoretical limit of the jitter variance. Computersimulations based on pulse-amplitude modulation (PAM) and quadrature amplitude modulationQAM sources show that the performance of the proposed algorithm is close to the CRB.

Description: Monitoring the illegal movement across the national border effectively is a challenging problem. The emerging technology of wireless sensor network (WSN) is expected to provide a new way to realize energy-efficient border intrusion detection. We propose a scheme to measure and guarantee the coverage quality of WSN. We also design a new coverage model for detecting one-direction path. The simulation results shows that the new coverage model could not only detect the intrusion in the border area well, but also extend the network lifetime in an efficient way.

Description: In this paper, the multinode amplify-and-forward cooperative communications for a network of Nnodes is studied via the novel concept of many-to-many space-time network coding (M2M-STNC).Communication under the M2M-STNC scheme is performed over two phases: (1) the broadcastingphase and (2) the cooperation phase. In the former phase, each node broadcasts its data symbol to allthe other nodes in the network in its allocated time slot, while in the latter phase, simultaneoustransmissions from N ¿ 1 nodes to a destination node take place in their time slot. In addition, theM2M-STNC scheme with optimal node selection (i.e., M2M-STNC-ONS) is proposed. In thisscheme, the optimal relay node is selected based on the maximum harmonic mean value of thesource, intermediate, and destination nodes¿ scaled instantaneous channel gains. Theoreticalsymbol-error-rate analysis for M-ary phase shift keying (M-PSK) modulation is derived for both theM2M-STNC and M2M-STNC-ONS schemes. Also, the effect of timing synchronization errors andimperfect channel state information on the SER performance and achievable rates is analyticallystudied. It is shown that the proposed M2M-STNC-ONS scheme outperforms the M2M-STNCscheme and is less sensitive to timing offsets and channel estimation errors. It is envisioned that theM2M-STNC-ONS scheme will serve as a potential many-to-many cooperative communicationscheme with applications spanning sensor and mobile ad hoc networks.

Description: In this paper, we explore a novel approach to end-to-end round-trip time (RTT) estimation using a machine-learning technique known as the experts framework. In our proposal, each of several 'experts' guesses a fixed value. The weighted average of these guesses estimates the RTT, with the weights updated after every RTT measurement based on the difference between the estimated and actual RTT. Through extensive simulations, we show that the proposed machine-learning algorithm adapts very quickly to changes in the RTT. Our results show a considerable reduction in the number of retransmitted packets and an increase in goodput, especially in more heavily congested scenarios. We corroborate our results through 'live' experiments using an implementation of the proposed algorithm in the Linux kernel. These experiments confirm the higher RTT estimation accuracy of the machine learning approach which yields over 40% improvement when compared against both standard transmission control protocol (TCP) as well as the well known Eifel RTT estimator. To the best of our knowledge, our work is the first attempt to use on-line learning algorithms to predict network performance and, given the promising results reported here, creates the opportunity of applying on-line learning to estimate other important network variables.

Description: With growing interest in using cognitive radio (CR) technology in wireless communication systems for vehicles, it is envisioned that future vehicles will be CR-enabled. This paper discusses CR technologies for vehicular networks aimed at improving vehicular communication efficiency. CR for vehicular networks has the potential of becoming a killer CR application in the future due to a huge consumer market for vehicular communications. This paper surveys novel approaches and discusses research challenges related to the use of cognitive radio technology in vehicular ad hoc networks. We review how CR technologies such as dynamic spectrum access, adaptive software-defined radios, and cooperative communications will enhance vehicular communications and, hence, present the potential of transforming vehicle communication in terms of efficiency and safety. Our work is different from existing works in that we provide recent advances and open research directions on applying cognitive radio in vehicular ad hoc networks (CR-VANETs) focusing on architecture, machine learning, cooperation, reprogrammability, and spectrum management as well as QoE optimization for infotainment applications. A taxonomy of recent advances in cognitive radio for vehicular networks is also provided. In addition, several challenges and requirements have been identified. The research on applying CR in vehicular networks is still in its early stage, and there are not many experimental platforms due to their complex setup and requirements. Some related testbeds and research projects are provided at the end.

Description: Data gathering is among the issues constantly acquiring attention in the area of wireless sensornetworks (WSNs). There is a consistent increase in the research directed on the gains of applyingmobile elements (MEs) to collect data from sensors, especially those oriented to power issues. Thereare two prevailing strategies used to collect data in sensor networks. The first approach requires datapackets to be serviced via multi-hop relay to reach the respective base station (BS). Thus, sensors willsend their packets through other intermediate sensors. However, this strategy has proven to consumehigh and a substantial amount of energy due to the dependency on other nodes for transmission. Thesecond approach encompasses a ME which serves as the core element for the searching of data. ThisME will visit the transmission range of each sensor to upload its data before eventually returning tothe BS to complete the data transmission. This approach has proven to reduce the energy consumptionsubstantially as compared to the multi-hop strategy. However, it has a trade-off which is the increaseof delay incurred and is constrained by the speed of ME. Furthermore, some sensors may lose theirdata due to overflow while waiting for the ME. In this paper, it is proposed that by strategicallydivisioning the area of data collection, the optimization of the ME can be elevated. These derived areadivisions are focused on the determination of a common configuration range and the correlation witha redundant area within an identified area. Thus, within each of these divided areas, the multi-hopcollection is deployed as a sub-set to the main collection. TheME will select a centroid point betweentwo sub-polling points, subsequently selecting common turning points as the core of the basis of thetour path. Extensive discrete-event simulations have been developed to assess the performance of theproposed algorithm. The acquired results depicted through the performance metrics of tour lengthand latency have determined the superior performance of the proposed algorithm in comparison tothe existing strategy. In addition, the proposed algorithm maintains the energy consumption within anacceptable level.

Description: WSN (wireless sensor network) is formed by a large number of cheap sensors, which are communicated by an ad hoc wireless network to collect information of sensed objects of a certain area. The acquired information is useful only when the locations of sensors and objects are known. Therefore, localization is one of the most important technologies of WSN. In paper W-VBLS scheme is proposed to extend VBLS. In this scheme, Firstly, a node estimates the distances according to the strength of its received RSSI from neighbor beacons, divides three beacons into a group, whose distances are similar. Secondly, by a triangle, formed by the node and two beacons of a group, a weighted bisector can be calculated out. Thirdly, an estimated position of the node with biggest RSSI value as weights can be calculated out by three bisectors of same group. Finally, the position of the node is calculated out by the average weighted of all estimated positions. The simulation shows that, compared with centroid and VBLS, W-VBLS has higher positioning accuracy and lower computation complexity.

Description: Intermodulation distortion (IMD) caused by nonlinear power amplifier (PA) is a major weakness in orthogonal frequency-division multiplexing (OFDM) transmitter systems, and most behavioral studies of IMD are based on specific example PAs. In recent papers, PA percentage linearization (PL), a general measurement for PA envelope variation, is investigated for its influence on system performance. Meanwhile, PL still somehow depends on specific example PA, and it mostly considers the PA saturation point (SP) variation. In this paper, a comparison analysis is presented to investigate the system performance when both SP and nonlinearity onset point (NOP) variations are considered. The simulations show that how the PA envelope variation can be represented by the signal impairment over IBO and OBO domains, respectively. It is interesting to find that although SP attracts much concern in current studies, NOP actually has a clear influence on modulation fidelity of nonlinear OFDM transmitter systems. Moreover, it is observed that when input power gets close to saturation range, the PAs having relatively higher nonlinearity show relatively lower distortion level over the input power domain. These interesting simulation observations above are analytically explained based on a mixed time domain and statistical analysis of IMD mechanism. An example IEEE 802.11a OFDM signal is driving through five example solid state PAs, and the system performance is measured by error vector magnitude (EVM) and adjacent channel power ratio (ACPR).

Description: IEEE802.11 s draft proposes a new medium access control function-mesh deterministic access (MDA), which is mainly used for single-channel wireless mesh local area network (LAN). In single-channel environment, collisions between control packets and data packets may occur very often. To completely avoid the collision between control packets and data packets, the mesh delivery traffic indication message (DTIM) interval is first divided into contention period and data transmission period. To reduce the hardware requirements in design, we require a mesh point (MP) only equips a single transceiver to support multichannel environment. To provide higher performance and network capacity than the original MDA for wireless mesh LAN, we proposed a multichannel MDA (MMDA) algorithm. However, the MMDA algorithm may suffer from the resource waste problem when wireless mesh LAN is at heavy-loading situation, so this paper proposes a dynamic adjustable contention period (DACP) mechanism to solve this problem. In addition, we use an adaptive backoff process (ABP) to improve the fairness of the MMDA algorithm. The theoretical analysis gives the upper limit of the throughput for the DACP mechanism. The simulation experiments clearly show the results in multichannel wireless mesh LAN environment that the proposed scheme performs better than the MMDA algorithm and the enhanced distributed channel access (EDCA) in throughput, average waiting time, and packet drop ratio.

Description: When estimating channel parameters in linearly modulated communication systems, the iterative expectation-maximization (EM) algorithm can be used to exploit the signal energy associated with the unknown data symbols. It turns out that the channel estimation requires at each EM iteration the a posteriori probabilities (APPs) of these data symbols, resulting in a high computational complexity when channel coding is present. In this paper, we present a new approximation of the APPs of trelliscoded symbols, which is less complex and requires less memory than alternatives from literature. By means of computer simulations, we show that the Viterbi decoder that uses the EM channel estimate resulting from this APP approximation experiences a negligible degradation in frame error rate (FER) performance, as compared to using the exact APPs in the channel estimation process.

Description: Wireless sensor networks can provide valuable information for a lot of measurement, tracking, surveillance, automation, and general-purpose monitoring applications. Information as humidity, temperature, pressure, infrared images, and noises will be sensed and packetized for distribution over the network, but corruption during transmission may compromise the accuracy of the retrieved information and even put people in danger. In fact, the sensed data may have different relevancies for the applications, altering the impact of packet corruptions. We propose a relevance-based partially reliable transmission approach to provide data delivery with different reliability guaranties, exploiting the relevancies of transmitted data when choosing the proper error recovery service. In this context, some error scenarios are investigated, considering different configurations of error bursts. We expect that the proposed partially reliable transmission mechanism can save energy over the network while assuring acceptable quality for sensing monitoring.

Description: Ultra wideband (UWB) radio for communication has several challenges. From the physical layer perspective, a signaling technique should be optimally designed to work in synergy with the underneath hardware to achieve maximum performance. In this paper, we propose a variant of pulse position modulation (PPM) for physical layer signaling, which can achieve raw bitrate in excess of 150 Mbps on a low complexity in-house developed impulse radio UWB platform. The signaling system is optimized to maximize bitrate under practical constraints of low complexity hardware and regulatory bodies. We propose a detector and derive its theoretical performance bounds and compare the performance in simulation in terms of symbol error rates (SER). Modifications to the signaling, which can increase the range by 4 times with a slight increase in hardware complexity, is proposed. Detectors for this modification and a comparative study of the performance of the proposed UWB physical layer signaling schemes in terms of symbol error rates are discussed.

Description: This paper describes the limiting behavior of linear and decision feedback equalizers (DFEs) in single/multiple antenna systems employing real/complex-valued modulation alphabets. The wideband frequency selective channel is modeled using a Rayleigh fading channel model with infinite number of time domain channel taps. Using this model, we show that the considered equalizers offer a fixed post detection signal-to-noise-ratio (post-SNR) at the equalizer output that is close to the matched filter bound (MFB). General expressions for the post-SNR are obtained for zero-forcing (ZF) based conventional receivers as well as for the case of receivers employing widely linear (WL) processing. Simulation is used to study the bit error rate (BER) performance of both MMSE and ZF based receivers. Results show that the considered receivers advantageously exploit the rich frequency selective channel to mitigate both fading and inter-symbol-interference (ISI) while offering a performance comparable to the MFB.

Description: Over the last two decades, free-space optical communication (FSOC) has become more and more interesting as an adjacent and/or alternative to radio frequency (RF) and optical fiber communications. The optical wave propagation in the FSOC channel is severely affected by atmospheric parameters, and it leads to the degradation of the data transmission quality and reliability. Among the various atmospheric effects, the beam wandering is the main cause of major power loss and cannot be solved without the incorporation of the beam centroid stabilization system. Therefore, designing a suitable opto-electronic assembly with a beam wandering mitigation system becomes significant to improve the performance of the FSOC system. A FSOC experimental setup is developed for the link range of 0.5 km in the college campus. A neural controller is designed for beam wandering mitigation. The neural controller processed the beam pointing (beam location) information obtained from an opto-electronic position detector (OPD) and then generated the necessary control outputs to the fast steering mirror (FSM) to steer the beam in the counter-direction to mitigate the beam wander at the receiver station. New design approach and architecture development for the implementation of the designed neural controller in the field-programmable gate array (FPGA) to mitigate the beam wandering are presented. The investigations on the performance of the neural controller in aiming a laser beam to be at a particular point on the detector plane are tested under dynamic disturbances generated at the transmitter in addition to the atmospheric effects through which the maximum correction capability of the developed neural controller is examined. Evidence of the suitability and the effectiveness of the proposed neural controller is evaluated in terms of beam centroid displacement, power spectral density (PSD), radial displacement on a 2D plane, effective scintillation index (ESI), Q-factor, and bit error rate (BER). The beam wandering range of -0.13 to +0.16 mm, maximum of 55 dB disturbance band attenuation with a frequency range of 0 Hz through 2 kHz, ESI of 0 to 0.15, Q-factor of 6, and BER of 6.45 x 10-9 are achieved due to the incorporation of the developed neural controller in different real-world environmental conditions.

Description: Network security and its energy efficiency are facing tougher challenges for mobile ad hoc networks (MANETs) due to emerging purposive strategic internal attacks conducted by smart malicious nodes and unavoidable external attacks. Most of the current works investigated the group key management for scalability and efficiency performance in MANETs to defend the external attacks, while some works envisioned the intrusion detection system or trust management to defend the internal attacks. However, fewer related protocols or algorithms could combine them well to enhance dual security performance as well as energy efficiency in MANETs. To this end, we have proposed a novel group key management protocol with high energy efficiency for the strategic mobile scenario of MANETs, which is provided with three functions to address the issues of improving security and energy efficiency performance: (1) designing a self-organized group establishing algorithm for strategy mobile application scenarios to ensure stable groups in spite of users' mobility with reducing the cost of rekeying operation, (2) proposing a lightweight contributory key agreement and authentication mechanism based on the group Diffie-Hellman protocol for enhancing global security, and (3) researching a strategic mobile management mechanism based on the Prufer codec method handling the effect of mobility impacts to enhance the multicast energy efficiency and provide secret communication among roaming users in MANETs. Both theoretical analyses and simulation results have demonstrated that our protocol is more energy-efficient for strategy mobile application scenario of MANETs with a large number of users.

Description: It is easy for adversaries to mount node replication attacks due to the unattended nature of wireless sensor networks. In several replica node detection schemes, witness nodes fail to work before replicas are detected due to the lack of effective random verification. This paper presents a novel distributed detection protocol to counteract node replication attacks. Our scheme distributes node location information to multiple randomly selected cells and then linear-multicasts the information for verification from the localized cells. Simulation results show that the proposed protocol improves detection efficiency compared with various existing protocols and prolongs the lifetime of the overall network.

Description: Handover is one of the key operations in the mobility management of long-term evolution (LTE)-based systems. Hard handover decided by handover margin and time to trigger (TTT) has been adopted in third Generation Partnership Project (3GPP) LTE with the purpose of reducing the complexity of network architecture. Various handover algorithms, however, have been proposed for 3GPP LTE to maximize the system goodput and minimize packet delay. In this paper, a new handover approach enhancing the existing handover schemes is proposed. It is mainly based on the two notions of handover management: lazy handover for avoiding ping-pong effect and early handover for handling real-time services. Lazy handover is supported by disallowing handover before the TTT window expires, while early handover is supported even before the window expires if the rate change in signal power is very large. The performance of the proposed scheme is evaluated and compared with two well-known handover algorithms based on goodput per cell, average packet delay, number of handovers per second, and signal-to-interference-plus-noise ratio. The simulation with LTE-Sim reveals that the proposed scheme significantly enhances the goodput while reducing packet delay and unnecessary handover.

Description: This paper addresses energy-efficient design for uplink multiuser SIMO systems with imperfect channel state information (CSI) at the base station (BS). Since the CSI at the BS is always imperfect due to the channel estimation error and delay, the imperfectness of the CSI needs to be considered in practical system design. It causes interuser interference at the zero-forcing (ZF) receiver and makes it difficult to obtain the globally optimal power allocation that maximizes the energy efficiency (EE). Hence, we propose a non-cooperative energy-efficient uplink power control game, where each user selfishly updates its own uplink power. The proposed uplink power control game is shown to admit a unique Nash equilibrium. Furthermore, to improve the efficiency of the Nash equilibrium, we study a new game that utilizes a pricing mechanism. For the new game, the existence of a Nash equilibrium and the convergence of the best response dynamics are studied based on super-modularity theory. Simulation results show that the proposed schemes can significantly improve the EEs of the mobile users in uplink multiuser SIMO systems.

Description: Multi-hop broadcast transmission is used in vehicular ad hoc networks (VANETs) to alert allvehicles within a geographical area of an emergency situation. However, the successfuldissemination of multi-hop warning messages beyond the transmission range of a vehicle faces threemajor issues: (i) the broadcast storm, (ii) the severe interference with the existing periodic single-hopsafety messages, and (iii) the hidden nodes. In this paper, we propose an efficient time-slottedmulti-hop broadcast protocol that significantly reduces the number of required transmissions, whileensuring a timely and successful delivery of the warning messages. To alleviate the broadcast stormproblem, we select only a subset of vehicles on the road to serve as the potential relay nodes. Each ofthese `segment leaders¿ is responsible for forwarding the warning messages arrived in its own roadsegment. To avoid interfering with the safety messages transmitted periodically, we propose toallocate separate time slots for the warning messages. We also devise a signaling mechanism thatensures the reliable delivery of these multi-hop messages. Simulation results confirm that thedeveloped protocol substantially outperforms existing schemes in terms of the number of requiredmulti-hop transmissions and the dissemination delay. At the same time, the proposed solutionmaintains a high reception rate and low end-to-end delay for the single-hop safety messages.

Description: One of the main properties of a three-dimensional (3D) video is the large amount of data, which impose challenges for network transport of videos, in applications such as digital video broadcast (DVB), streaming over IP networks, or for transmission over mobile broadband. Addressing these challenges requires a thorough understanding of the characteristics and traffic properties of 3D video formats. We analyzed 3D video formats using publicly available long video frame-size traces of videos in full high definition (HD) resolution with two views. Examined 3D video representation formats are the multiview (MV) video format, the frame sequential (FS) format, and the side-by-side (SBS) format. We performed a multifractal analysis through extensive simulation and showed multifractal properties of 3D video representation formats. It was shown that the MV video had the highest multifractal nature, while the FS video had the lowest. Also, a part of the multifractal spectrum connected to the highest changes in the signal (high bitrate variability) is analyzed in detail. Changes in multifractal properties for different streaming approaches of 3D videos with aggregated frames are examined, as well as the influence of frame types and values of quantization parameters. Multifractal analysis was performed by the method of moments and by the histogram method.

Description: In recent times, there is increasing consensus that the traditional Internet architecture needs to be evolved for it to sustain unstinted growth and innovation. A major reason for the perceived architectural ossification is the lack of the ability to program the network as a system. This situation has resulted partly from historical decisions in the original Internet design which emphasized decentralized network operations through colocated data and control planes on each network device. The situation for wireless networks is no different resulting in a lot of complexity and a plethora of largely incompatible wireless technologies. With traditional architectures providing limited support for programmability, there is a broad realization in the wireless community that future programmable wireless networks would require significant architectural innovations. In this paper, we will present an unified overview of the programmability solutions that have been proposed at the device and the network level. In particular, we will discuss software-defined radio (SDR), cognitive radio (CR), programmable MAC processor, and programmable routers as device-level programmability solutions, and software-defined networking (SDN), cognitive wireless networking (CWN), virtualizable wireless networking (VWN) and cloud-based wireless networking (CbWN) as network-level programmability solutions. We provide both a self-contained exposition of these topics as well as a broad survey of the application of these trends in modern wireless networks.

Description: Static topology analysis is not sufficient for the dynamic vehicular ad hoc network. Understanding the evolving topology of vehicular ad hoc networkings (VANETs) caused by vehicle mobility is very important for routing protocol design and algorithm optimization. This paper explores the spatial and temporal features of vehicular network topologies based on two real taxi-trace datasets. The analysis results reveal that the whole topology of VANETs consists of a large number of small-sized connected components. Two quantitative metrics are proposed to measure the stability and location dependency of the connected components. When the communication range is greater than a threshold, a large proportion of vehicles will connect to the biggest connected component, which is relatively stable and covers the most part of the downtown region of the city. Based on the analytical results, we propose several design philosophies and new research issues for VANETs.

Description: In a cognitive radio network (CRN), when the secondary users (SUs) are battery-powered devices, the concept of energy-efficient design is very important. The sensing time and the number of cooperative SUs in the cooperative spectrum sensing could greatly affect energy consumption and throughput of the system. In this paper, we propose an energy utility function by formulating the achievable data rate of a cooperative CRN in terms of the energy consumption by the CRN. The maximization of the energy utility function is obtained by jointly designing the sensing time, sensing threshold, and number of cooperative SUs with the constraint of sufficient protection for primary user (PU). Numerical results show that the CRN can achieve almost the maximum achievable data rate with significant energy saving through the joint optimization.

Description: A water-filling (WF) method is one of the techniques to improve a performance of multiple-inputmultiple-output (MIMO) systems. However, the application of theWFmethod to multiple-hop MIMOrelay systems (MMRSs) has not been discussed, especially in amplify-and-forward (AF) schemes. Inthis paper, the WF method for MMRSs with AF scheme is proposed and evaluated in both perfectand imperfect channel state information (CSI). The effect of imperfect CSI on optimization of transmitpower at all transmitters and on co-channel interference is taken into account. Compared to theaverage transmit power, the end-to-end channel capacity of the WF method is higher in the perfectCSI; however, it is subject to the effect of imperfect CSI. Additionally, half-duplex and full-duplextransmission methods are also discussed in this paper. The end-to-end channel capacity of full duplexis higher and more robust than that of the half duplex due to a double of allocation time and a half ofdelay time.

Description: In vehicular ad hoc networks (VANETs), the communication links are inherently unstable due tovehicles' mobility and various impairment of radio signal. Existing geographic routing protocolsoften choose the next hop according to the greedy forwarding, regardless of the link's quality andtransmission reliability. The successful packet delivery rate is decreased in non-ideal communicationlinks. Consequently, the reliability of data transmission is worse and the network throughput isdeclined. In this paper, we propose a routing protocol called link state aware geographic routingprotocol (LSGR) for VANETs. In LSGR, a routing metric called expected one-transmission advance(EOA) is contrived to improve the greedy forwarding algorithm by explicitly incorporating the linkstate and packet's advance. Routing with the EOA metric, one can improve the transmission efficiencyby diminishing transmission failures. Simulation results show that LSGR can achieve a higherthroughput and packet delivery rate than the geographic routing protocols that adopt the traditionalgreedy forwarding.

Description: The widespread deployment of base stations constitutes a promising solution to cope with theever-increasing wireless data rate demands. However, it also increases the interference levels,especially at the cell-edge. Most interference management techniques assume coordination betweenbase stations, which involves undesired overhead and delays. To solve this problem, we propose aneighbor-friendly autonomous algorithm for power control in wireless heterogeneous networks thatprotects victim users from neighboring cells through a penalty factor in the power allocation level.We refer to this algorithm as neighbor-friendly iterative waterfilling (NF-IWF). In addition, wepropose a low-complexity closed-form version that fixes the penalty factor by assuming a linearapproximation of the victim user data rate. In high interference conditions, it can achieve a victimuser data rate increase by a factor of 3.5 compared to IWF, 15 compared to soft frequency reuse(SFR), and 60 compared to equal power allocation (EPA) with a marginal decrease of the primaryuser data rate.

Description: The last decades have been really hungry in new ways to reduce energy consumption. That is especially true when talking about wireless sensor networks in general and home multimedia networks in particular, since electrical energy consumption is the bottleneck of the network. One of the most energy-consuming functional block of an equipment is the radio front end, and methods to switch it off during the time intervals where it is not active must be implemented. This paper proposes a wakeup radio circuit which is capable of both addressing and waking up not only a more efficient but also more energy-consuming radio front end. By using a frequency footprint to differentiate each sensor, awaking all the sensors except for the one of interest is avoided. The particularity of the proposed wake-up receiver is that the decision is taken in the radio-frequency part and no baseband treatment is needed.

Description: Relaying is one of the major innovative concepts proposed in the recent years for cellular radio communication systems. It is a perfect solution for dealing with the issue of high variability of performance in cellular networks. By coordinated deployment at cell-edge or in shadowed areas, relay nodes can extend network coverage and increase the low end-user performance. Considering the advantages, relaying is recently being included in the standards of the fourth generation systems such as the LTE-Advanced and the WiMAX. However, one major problem of relaying is still to be resolved. Specifically, there are no concrete concepts for quality-of-service provisioning for relayed transmissions. This paper investigates the case of packet delivery times over multi-hop links in relay-enhanced networks. The discussion is specifically based on relaying implementation in the LTE-Advanced system. The quality-of-service satisfaction and its fairness for the base station and relay-node-connected users are analyzed in the framework of the utility theory. For the purpose of this analysis, utility functions are proposed for real-time traffic with minimum data rate and/or maximum packet delivery time requirements. Furthermore, several optimization concepts are proposed for managing multi-hop transmissions in a quality-of-service aware manner. The included analysis based on the LTE-Advanced system level simulations shows that the proposed optimizations have the potential to improve the overall quality-of-service satisfaction in a relay-enhanced system.

Description: The inherent mesh infrastructure of IEEE 802.11-based wireless mesh networks provides added support to construct multiple robust paths. However, based on geometric locations of wireless nodes, neighborhood interference and channel contention impose challenges on multipath routing schemes. A large body of research has been carried out to maximize aggregate end-to-end throughput using multipath routing; however, interference has not been accurately modeled in majority of the work. Based on the relative location of transmitters and receivers, information asymmetric non-coordinated interference introduces bottleneck links and significantly reduces the aggregate throughput. The impact of this interference is even observed on links several hops away. In this paper, multipath routing is integrated with topology control to manage such multilevel asymmetric interference. An optimization model has been presented with an objective to achieve optimized end-to-end throughput using multiple available paths, considering coordinated and asymmetric non-coordinated interference. The goal of this research is to develop a multipath routing strategy which can achieve better end-to-end throughput by purging badly affected asymmetric non-coordinated interfering links during path construction procedure. The proposed model and routing strategy have been tested through extensive simulations. The results clearly exhibit the efficacy of the proposed approach, which achieves better aggregate end-to-end throughput compared to existing multipath routing schemes.

Description: Wireless sensor networks face many threats which drain the energy. The performance of sensor network routing is much affected in the presence of selfish nodes with messages being delivered with a longer delay. Social network routing is a method in which the messages are selectively forwarded through the nodes where the encounters between these nodes are more likely to occur. Network reputations clearly speak about the quality of nodes involved in data forwarding. The idea is to utilise social network reputations of source or destinations for effective data forwarding in farmland sensor networks.

Description: Ad hoc networks are wireless mobile networks that can operate without infrastructure and without centralized network management. Traditional techniques of routing are not well adapted. Indeed, their lack of reactivity with respect to the variability of network changes makes them difficult to use. Moreover, conserving energy is a critical concern in the design of routing protocols for ad hoc networks because most mobile nodes operate with limited battery capacity, and the energy depletion of a node affects not only the node itself but also the overall network lifetime. In all proposed single-path routing schemes, a new path-discovery process is required once a path failure is detected, and this process causes delay and wastage of node resources. A multipath routing scheme is an alternative to maximize the network lifetime. In this paper, we propose an energy-efficient multipath routing protocol, called ad hoc on-demand multipath routing with lifetime maximization (AOMR-LM), which preserves the residual energy of nodes and balances the consumed energy to increase the network lifetime. To achieve this goal, we used the residual energy of nodes for calculating the node energy level. The multipath selection mechanism uses this energy level to classify the paths. Two parameters are analyzed: the energy threshold beta and the coefficient alpha. These parameters are required to classify the nodes and to ensure the preservation of node energy. Our protocol improves the performance of mobile ad hoc networks by prolonging the lifetime of the network. This novel protocol has been compared with other protocols: ad hoc on-demand multipath distance vector (AOMDV) and ZD-AOMDV. The protocol performance has been evaluated in terms of network lifetime, energy consumption, and end-to-end delay.

Description: Compared to asynchronous contention-based random access, e.g., carrier sensing multiple access, synchronous and distributed link scheduling for orthogonal frequency-division multiplexing (OFDM) systems is a viable solution to improve system throughput for device-to-device (D2D) ad hoc network. In particular, spatial spectral efficiency can be improved by scheduling as many concurrent D2D links necessary to satisfy individual signal-to-interference ratio (SIR) requirements. In this paper, we propose an adaptive yielding mechanism that can further improve the spatial spectral efficiency by allowing for more concurrent D2D links whenever more interference can be accepted, e.g., when the instantaneous bandwidth efficiency requirement is less than the current link capacity. Even if the system throughput varies with the link density, it is shown that the average system throughput can be significantly improved by the proposed yielding mechanism.

Description: Reliability analysis is a key problem in wireless sensor networks (WSNs). The primary contribution of this paper is an in-depth study of the reliability of a chain topology wireless sensor network with multiple-sending scheme. We study the wireless link reliability for the fading channels. The node energy availability for the source and relay nodes is investigated in terms of the limited node energy. The instantaneous network reliability and the mean time to failure are derived. Finally, the initial node energy allocation scheme is proposed to balance the lifetime of each sensor node, thus reducing the total energy consumption. The simulation results substantiate the correctness of the theoretical results.

Description: Over the last years, the content delivery network (CDN) market has been witnessing globally an increase in the development of cloud-based CDNs, as they constitute a viable and cost-effective alternative to traditional commercial CDNs. Towards that direction, Social-Aware Virtual Network Embedding (SAViNE) for wireless content delivery within the OpenLab project aims at establishing, assessing, and prototyping a novel framework for deploying a CDN over the wireless cloud. Specifically, the goal of SAViNE is to provide experimental validation of the efficiency of social network analysis (SNA) - inspired surrogate server placement strategies, devised for fostering content delivery. The proposed framework has been integrated with the OpenLab experimental facilities, providing a run-time environment for CDN deployment, operation, and performance evaluation over the wireless environment. The framework's feasibility and scalability is experimentally validated. The study is complemented with repeatability evaluation of experimental measurements, related to the resulting CDN's operational efficiency.

Description: In order to meet the high throughput demand set by international mobile telecommunication union, carrier aggregation is exploited for expanding the bandwidth of up to 100 MHz in Long Term Evolution-Advanced (LTE-A). For achieving the aforementioned bandwidth, a maximum of five component carriers (CCs) can be aggregated as per Release 10 LTE-A. Improper CC selection and scheduling will result in hazardous throughput, fairness, and interference problems. Therefore, a proper CC selection and scheduling algorithm is most important for the overall performance of the network. On the other hand, due to an increased information exchange, centralized network planning is not a suitable choice here. In this study, we are employing a self-organized particle swarm optimization (PSO)-based joint component carrier selection and scheduling (JCCS) algorithm for the downlink. More precisely, the concern of the proposed algorithm is the autonomous distribution of resource blocks (RBs) from the pool of CCs by the base station, with the concern of minimizing the impact of inter-cell interference. Our proposed PSO-based JCCS algorithm results in the maximization of the min-max throughput by managing the inter-cell interference in an appropriate manner. Moreover, the proposed algorithm is compared with the traditional CC selection and scheduling algorithms, i.e., random, round robin, and proportional fair. The comparison is carried out in terms of throughput and fairness, and the calculated percentage gain in the end elaborates the performance improvement by exploiting PSO-based JCCS.

Description: Orthogonal frequency division multiplexing (OFDM) has been adopted in many modern communication systems due to its robustness against frequency-selective fading channels as well as its near-rectangular spectrum that can achieve high spectral efficiency. However, its major drawback is the resulting signal with high peak-to-average power ratio (PAPR), which causes severe nonlinear distortion at the power amplifier (PA) unless input backoff is chosen sufficiently large. The effect of the nonlinear distortion is two-fold: out-of-band radiation and signal quality degradation. The former causes adjacent channel interference and thus degrades the bandwidth efficiency. The latter affects the system level performance and is often measured by the error vector magnitude (EVM). It is thus important for the system designer to analyze the nonlinear distortion caused by a given PA in terms of power spectral density (PSD) and EVM, but accurate calculation of these characteristics may be generally involved. In this work, by establishing the link between the cross-correlation coefficient of the input and output signals from PA and the resulting PSD, we characterize the in-band and out-of-band distortion of nonlinearly amplified OFDM signals based exclusively on the cross-correlation coefficient. The accuracy of the proposed approach is confirmed by both simulation and measurement using a real PA.

Description: A cognitive radio ad hoc network (CRAHN) can be considered as a special delay tolerant network(DTN) that is composed of mobile secondary users (SUs) with social characteristics. Givenintermittent connectivity and spectrum availability, it is a challenging issue regarding how to transmitmessages between SUs in a reliable and effective way in CRAHNs. To tackle this challenge, wepropose a social-aware opportunistic routing and relay selection scheme, called SoRoute, which firstpredicts the link reliability based on a new social-relationship-aware mobility model and then fusesthe relationships of SUs to make a routing and relay decision. In our design, different predictionschemes are employed for the nodes with different relationships. A message is forwarded to the relaynode with the largest encounter probability with the destination. The evaluation results demonstratethat our social-based opportunistic routing scheme significantly improves the performance comparedto the existing routing schemes such as Direct Delivery, First Contact, MaxProp, and Prophet.

Description: We consider the problem of route selection and optimization for a mobile sensor network, which involves two nodes transferring information over a large area using a number of intermediate routers in the presence of noise, path loss, multipath fading, and interference. The communication- and position-aware reconfigurable (COMPARE) route optimization framework is proposed to improve the end-to-end throughput of the routes in the realistic communication environment. Initially, a communication-aware route selection strategy selects the optimal route by integrating the routing decisions with the link quality. The quality of the wireless link is characterized by the reception probability, i.e., the probability of successfully receiving packets over a realistic communication link. The selected route is reconfigured by exploiting the multipath fading, position information, and the mobility of the nodes during the phase of position-aware optimization. The optimal position for a router is heuristically found using a priori information about fading channels and the positions of transmitting and interfering nodes. The router is guided to the optimal position using the feedback mobility control, and only the route selected by the COMPARE framework is used for data transmission between the source and destination node. We illustrate through simulations that the proposed framework provides routes with considerably better performance than conventional route selection metrics, in terms of the end-to-end throughput.

Description: To improve the localization accuracy in multipath environments, this paper presents an effective localization approach with the utilization of reference tags. In this approach, an improved k-nearest neighbor (k-NN) algorithm is proposed based on radio-frequency (RF) phases. The traditional k-NN algorithm only focuses on the weighting factors of the coordinates of the selected reference tags, while the improved k-NN algorithm aims at the estimation of direct distance from a reader antenna to a target tag. Then, the location is estimated by linear least square with a new reference selection scheme. Simulation results show that our approach is superior to the traditional localization approaches under multipath environments. In addition, we conclude that phase has the superiority over strength in the selection of reference tags for range estimation, and range estimation is more accurate than coordinate estimation with k-NN algorithm for localization.

Description: In this paper, a novel two-tier mechanism for the access control and resource allocation of a two-hop high data rate IEEE 802.15.5 network is proposed. One of the main contributions in this proposal is the use of a dynamic superframe size in the IEEE 802.15.5. Additionally, the ideas of using a superframe utilization threshold and a channel time allocation period (CTAP) utilization threshold are incorporated, with the aim of allowing more devices to access the shared superframe. Using these thresholds, two new hop-1 resource allocation algorithms are described; CTAP utilization threshold-based resource allocation algorithm (CTRA) and superframe utilization threshold-based resource allocation algorithm (STRA). These algorithms control the access of the hop-1 Mesh PicoNet Coordinators (MPNCs) and Mesh DEVices (MDEVs) to the channel time resources in the superframe. Furthermore, an algorithm for the distribution of the hop-1 MPNCs' resources among the real-time (RT) and non-real-time (NRT) MDEVs at hop-2 is introduced. In this mechanism, a new flag metric is applied to provide higher priorities to MPNCs over MDEVs in the hop-1 algorithms and to the RT MDEVs over the NRT MDEVs in the hop-2 algorithm. Simulation results show the superiority of the proposed mechanism over others by providing a higher satisfaction factor and higher fairness among the competing devices at both hop-1 and hop-2 of the IEEE 802.15.5.

Description: This paper describes the implementation and the technical specifications of a geo-location database assisted by a spectrum-monitoring outdoor network. The geolocation database is populated according to ECC report 186 methodology. The API between the sensor network and the geo-location database implements an effective and secure connection to successfully gather sensing data and sent it to the geo-location database for post-processing. On the other hand, the testbed allows authorised TV white space devices to gain access to the services of the geo-location database, according to a draft implementation of IETF PAWS.Two experimental methodologies are available with the testbed: one focused on coexistence studies with commercial wireless microphones, when the testbed is used for sensing only, and another for demonstration purposes, when the testbed is also used to emulate wireless microphone signals.Overall, this hybrid approach is a promising solution for the effective use of TV white spaces and for the coexistence with digital TV broadcast signals, or dynamic incumbent systems, such as unregistered wireless microphones.

Description: To satisfy the ever-increasing data rate and service coverage demands, wireless communication networks evolve into heterogeneous networks (HetNets), where low-cost small base stations are embedded in conventional macrocells. Intercell interference emerges as the key capacity-limiting factor in such dense networks, restricting the reusability of spectral resources. Therefore, advanced interference mitigation techniques relying on multi-cell cooperation have attracted significant attention from the wireless industry and academia. This paper discusses interference management schemes for multi-tiered spectrum access in next-generation HetNets. A novel scheme based on full system cognition and base station cooperation is proposed as an enabler for high-capacity HetNets. In addition, practical implementation and operational challenges are investigated.

Description: There is an extensive research interest in cognitive radio mobile ad hoc networks (CR-MANETs) to improve the spectrum efficiency by developing innovative design techniques through various layers of the protocol stacks. This paper presents the optimisation of CR-MANETs by exploiting the efficient usage of the available wireless spectrum through a framework for spectrum-aware handoff. In this paper, the concept of integrated handoff management in CR-MANETs is considered. An analytical model for a spectrum handoff scheme is introduced based on spectrum mobility in which secondary users (SUs) will move to another unused spectrum band, giving priority to a Primary User (PU), while satisfying its communication quality of service (QoS). The main contribution is using the Markov chain to model the evolution of the network (node position, node speed, channel quality, etc.) and to propose the combined spectrum handoff and routing. The performance of the network is analyzed based on the Markov chain. The comparison results from both analytical modelling and simulation clearly show an improvement in the performance of the SU network in terms of the route maintenance probability and the SU throughput. It is also proved that not only the PU activity affects the performance of the handoff management scheme but also the channel transmission range and the node mobility have a significant effect on the performance of the management scheme.

Description: This paper proposes a method of detecting the number of persons in an area, along with their locations and breath patterns, using ultra-wideband (UWB) radars. A time-of-arrival type of location estimation was performed in this study not only using techniques introduced in the existing study results of detecting biomedical signals using a UWB radar but also by applying an initial screening method for redundancy reduction and a maximum likelihood observation-target association technique. This paper also introduces radar measurements conducted under a variety of scenarios and presents the results of applying the proposed algorithm to the measured data. The test results showed that the number of targets was accurately estimated with an average positioning accuracy of 12.7 cm.

Description: Vehicles in the future are anticipated to have the ability to communicate and exchange useful informationin order to avoid collisions. However, for this cooperation to be possible, all vehicles will haveto be equipped with compatible wireless modules, based on, e.g. IEEE 802.11p (used in ITS-G5 orWAVE), which implements intelligent transport systems operating in the 5GHz frequency band. Duringthe implementation phase of the system, there will be many older vehicles without such equipmentthat can cause hazard as information about them will not be available to vehicles equipped with IEEE802.11p modules. In this paper, we present a system to be used as a roadside unit (RSU), developedexplicitly for infrastructure-to-vehicle (I2V) communication that can solve the aforementioned trafficsafety problems. The system consists of a universal medium-range radar (UMRR) and an IEEE802.11p modem integrated together to detect vehicles, with or without communication capabilities,and forward their position and speed vectors to vehicles, with IEEE 802.11p modules installed, forcollision avoidance. Tests have been performed by using our system in parallel with vehicles in whichIEEE 802.11p modules are installed and comparing the content in the Cooperative Awareness Messagesobtained from both systems. Accuracy tests have been performed in order to verify the system,and Kalman filtering is applied on the radar data to improve the accuracy of the system further.

Description: Coding-aware routing is an effective approach to create more coding opportunities in inter-flow network coding. To the best of our knowledge, most of the coding-aware routing schemes focus on maximizing the coding opportunities. However, for opportunistic transmission, the throughput is not always increased with the increase of coding opportunities. In this paper, we explore why this case will happen and how to measure the benefits of network coding in the opportunistic routing. According to the above conclusions, we propose a novel high-throughput coding-aware opportunistic routing (HCOR) to achieve the maximal throughput gain in wireless mesh networks. HCOR is based on anypath routing and takes advantage of the network coding gain to find out the route with minimal anypath cost reasonably. Meanwhile, it is also a 'multihop' network coding and changes the route with dynamical data loads adaptively. Simulation results demonstrate that HCOR has better performance than coding opportunity-aware routing and also obtains a significant throughput gain in wireless mesh networks.

Description: Delay-tolerant networks (DTNs) are wireless partitioned networks. Because of intermittency, mobile ad hoc network (MANET) routing protocols are not efficient in DTNs. Wildlife tracking, vehicular networks, interplanetary networks, etc. are different applications of DTN. Regarding DTN applications, different parameters should be considered while designing DTN routing protocols. Message delivery ratio, message delivery delay, overhead, message drop, etc. are some important factors that are usually considered in routing algorithms. This paper proposes a method which tries to reduce overhead and message drop while increasing message delivery ratio. Choosing the appropriate number of message copies to distribute in the network is important. Few numbers of copies can lead to message drop. So, the message cannot be delivered to the destination. On the other hand, increasing the number of copies causes overhead increase in the network. The proposed algorithm uses particle swarm optimization (PSO) in intelligent choosing of number of message copies. Regarding message delivery ratio and network overhead, PSO greatly helps in finding the suitable number of copies. In order to evaluate our method, which is called PSODTN, we compared it with epidemic routing (ER) and probabilistic routing protocol using history of encounters and transitivity (PROPHET). PSODTN helps to reduce overhead, on average, 95.6% compared to ER and PROPHET. While reducing overhead, PSODTN message delivery ratio is on average 98%.

Description: A mobile ad hoc network (MANET) is a self-organized system comprised by multiple mobile wireless nodes. The node misbehavior due to selfish reasons can significantly diminish the performance of MANET. A selfish node attempts to use the resources only for its own purpose and it hesitates to share the resources with their neighbors. So, it is very important to detect the selfish nodes to improve the performance of MANET. Initially, an architectural model of a MANET is constructed and the communication between the mobile is originated. The packet drop can happen in MANET due to the selfish node or network congestion. In this paper, a Record- and Trust-Based Detection (RTBD) technique is proposed to detect the selfish nodes efficiently in MANET. The main reason for using trust in this analysis is to accelerate the detection of misbehaving nodes. This study has been carried out in order to analyze the detection of selfish nodes on essential network functions such as routing and packet dropping. The results show that the proposed selfish node detection method is very efficient, since the detection time of selfish nodes is diminished and the overall overhead is very low. The simulation study demonstrates that the proposed RTBD method enhances the selfish node detection ratio, packet delivery ratio (PDR), and average packet drop ratio.

Description: Wireless channels are prone to many impairments, such as noise and fading. Weak channels between the nodes in the wireless sensor network (WSN) can cause reception of erroneous packets. Retransmission mechanisms are mainly used to tackle the problem of erroneous reception in WSN communication protocols. Weak channels can cause high number of retransmissions in order to deliver a packet correctly, which will consume high energy of both the transmitting and the receiving nodes. Error correcting codes (ECCs) can be used to reduce number of retransmissions, but most ECCs have complex decoding algorithms, which leads to high processing energy consumption at the receiving nodes in the WSN. In this paper, we present a low power consumption decode-and-forward approach for the multi-hop WSNs; a serial concatenation convolutional codes (SCCC) encoder is implemented at the source node while the complex iterative decoding algorithm is shifted to the sink (base station). The intermediate nodes run a Viterbi decoding algorithm to decode only the inner code of the SCCC encoder. We investigate the effect of changing constraint length of both the inner and the outer codes and the effect of changing encoding block size. We show that most packets can be decoded at the base station at low signal-to-noise ratio (SNR) channels with the penalty of small energy loss in decoding the packet at the nodes in the network.

Description: An achievable rate region for a primary multiple access network coexisting with a secondary link of one transmitter and a corresponding receiver is analyzed. The rate region depicts the sum primary rate versus the secondary rate and is established assuming that the secondary link performs rate splitting. The achievable rate region is the union of two types of rate regions. The first type is a rate region established assuming that the secondary receiver cannot decode any primary signal, whereas the second is established assuming that the secondary receiver can decode the signal of one primary link. The achievable rate region is determined first assuming discrete memoryless channel (DMC), then the results are applied to a Gaussian channel. In the Gaussian channel, the performance of rate splitting is characterized for the two types of rate regions. Moreover, a necessary and sufficient condition to determine which primary signal the secondary receiver can decode without degrading the range of primary achievable sum rates is provided. When this condition is satisfied by a certain primary user, the secondary receiver can decode its signal and achieve larger rates without reducing the sum of the primary achievable rates as compared to the case in which it does not decode any primary signal. It is also shown that the probability of having at least one primary user satisfying this condition grows with the primary signal-to-noise ratio.

Description: Subcarrier mapping (SCM) is considered to be crucial for capacity-maximization in an orthogonal frequency division multiplexing (OFDM) relaying network. Although SCM in an OFDM system has been investigated extensively, nevertheless, the outage probability and outage capacity analysis of the system is not yet available in the literature. This paper presents the outage analysis of a dualhop OFDM relay system with ordered subcarrier paring schemes, i.e., worst-to-best (WTB) SCM and best-to-best (BTB) SCM. Accurate close-form expressions are derived for end-to-end outage while considering a dual-hop fixed gain amplify-and-forward (AF) relaying system with Rayleigh fading channel model. The first and second moments of end-to-end signal-to-noise ratio (SNR) and capacity are derived for WTB SCM and BTB SCM schemes while approximating the probability distribution function (PDF) of total capacity of each subcarrier pair by Gaussian distribution. The outage performances of these schemes are compared with balanced links, i.e., when the SNR is same for both hops, as well as unbalanced links, i.e., when the SNR of the second hop is one half of the SNR of the first hop. The numerical results validate the analysis in Rayleigh fading channel.

Description: In this paper, we propose and investigate a hybrid positioning data fusion technique for heterogeneous networks in critical transmission scenarios. The focus is on two scenarios: the small indoor scenario combining Wi-Fi and cellular systems and the small-to-mid-scale scenario composed of one located Mobile Terminal (MT) and one anchor node (AN). More specifically, we investigate the effect of the availability of three metrics i.e. the time of arrival (ToA), the angle of arrival (AoA), and the received signal strength-based fingerprint (RSS) on the positioning accuracy when the number of ANs is less than three. To combine these measurements, we use a 2-level unscented Kalman Filter (UKF) in conjunction with some advanced clustering techniques based on genetic algorithms. Simulation results show that the proposed hybrid data fusion technique outperforms the techniques presented in the literature independently of the transmission conditions.

Description: Vehicle sensing system is an important research topic in the research field of Internet-of-Vehicles (IoV). Reliability and real-time performance of vehicle sensing systems are greatly influenced when deadlock happens. When a deadlock is detected, identifying the optimal deadlock solving strategy can ensure that the system goes back to normal state quickly. In order to address this issue, this paper proposes an efficient deadlock solving method. Firstly, the deadlock problem in a vehicle sensing system is analyzed based on four deadlock occurring conditions (i.e., mutual exclusion, hold and wait, no preemption, and circular wait). Secondly, an optimization model is built to combine the quantity and cost of tasks in vehicle sensing systems. After that, a co-evolutionary genetic algorithm (CGA) is developed to search the optimal deadlock solving strategy. Finally, experiments by simulation are conducted and the experimental results show the efficiency of the proposed deadlock solving method for vehicle sensing systems.

Description: With the widespread deployment of wireless mesh networks (WMNs) in industrial environments, real-time (RT) communication may benefit from the multi-hop relaying infrastructure provided by WMNs. However, RT communication must be able to coexist with non-RT traffic sources that will interfere with RT communication. Within this context, this paper assesses the impact of interferences caused by non-RT traffic sources upon RT traffic in IEEE 802.11s mesh networks. Through an extensive set of simulations, we assess the impact of external traffic sources upon a set of RT message streams in different communication scenarios. According to the simulation results, we infer that RT traffic in 802.11s networks may be highly affected by external interferences, and therefore, such interferences must be taken into account when setting-up 802.11s networks. By varying the network load imposed by external interferences, we provide some useful hints about utilization thresholds above which the network can no longer reliably support RT traffic. We also present insights about the setting-up of some network parameters in order to optimize the RT communication performance.

Description: With the rapidly increasing demand for high-speed data transmission and a growing number of terminals, massive multiple-input multiple-output (MIMO) has been shown promising to meet the challenges owing to its high spectrum efficiency. Although massive MIMO can efficiently improve the system performance, usage of orthogonal pilots and growing terminals causes large resource consumption especially when the coherence interval is short. This paper proposes a semi-orthogonal pilot design with simultaneous data and pilot transmission. In the proposed technique, we exploit the asymptotic channel orthogonality in massive MIMO systems, with which a successive interference cancellation (SIC)-based channel estimation is applied to mitigate the mutual interference between data and pilot. We derived the theoretical expressions of the achievable rates in massive MIMO systems with our proposed pilot design. Further discussion on performance verifies the superiority of our proposed pilot design for high or low signal-to-noise-ratios (SNRs) with any coherence interval length. And simulation results show that the proposed pilot design can achieve a significant performance improvement with reduced pilot resource consumption compared with the conventional orthogonal pilots.

Description: Performance analysis of carrier sense multiple access with collision avoidance (CSMA/CA) scheme based on IEEE 802.15.6 standard has been discussed in many literatures. In previous works on IEEE 802.15.6 and another standards, the performance was analyzed by using access probability in one slot duration and the Markov chain model was proposed to calculate the access probability in both saturation and non-saturation models. However, for both saturation and non-saturation models, the access probability or the packet arrival rate was assumed to be fixed and the effect of remained packets that was transmitted unsuccessfully due to busy channel or collision was not considered. In this paper, in order to evaluate the system performance more accurately, the effect of the remained packet is taken into account and a statistical method is proposed to calculate the successful probability of wireless body area networks (WBANs). Moreover, a time-saturation model is defined as a system model in which the system performance is changed following the operating time, and then, the change between three models, i.e., saturation, non-saturation, and time-saturation models, is analyzed. The calculation result indicates that the proposal method can achieve the same performance as the Markov chain method in both saturation and non-saturation models. However, in the time-saturation model, the proposal statistical method is more accurate.

Description: The increasing complexity of wireless standards has shown that protocols cannot be designed once for all possible deployments, especially when unpredictable and mutating interference situations are present due to the coexistence of heterogeneous technologies. As such, flexibility and (re)programmability of wireless devices is crucial in the emerging scenarios of technology proliferation and unpredictable interference conditions. In this paper, we focus on the possibility to improve coexistence performance of WiFi and ZigBee networks by exploiting novel programmable architectures of wireless devices able to support run-time modifications of medium access operations. Differently from software-defined radio (SDR) platforms, in which every function is programmed from scratch, our programmable architectures are based on a clear decoupling between elementary commands (hard-coded into the devices) and programmable protocol logic (injected into the devices) according to which the commands execution is scheduled. Our contribution is two-fold: first, we designed and implemented a cross-technology time division multiple access (TDMA) scheme devised to provide a global synchronization signal and allocate alternating channel intervals to WiFi and ZigBee programmable nodes; second, we used the OMF control framework to define an interference detection and adaptation strategy that in principle could work in independent and autonomous networks. Experimental results prove the benefits of the envisioned solution.

Description: Electric vehicles (EVs) are becoming a more attractive transportation option, as they offer great cost savings, decrease foreign oil dependency, and reduce carbon emissions. However, varying temporal and spatial demand patterns of EVs threatens power grid operations and its physical components. Thus, the ability of the power grid to handle the potential extra load has become a major factor in the mainstream success. In order for this integration to occur seamlessly, the power grid and the consumers need to be coordinated in harmony. In this paper, we address the critical challenges introduced by the penetration of EVs, systematically categorize the proposed frameworks for demand management, and the role of information and communication technologies in the solution process. We provide a comprehensive survey on the communication requirements, the standards and the candidate technologies towards the Internet of electric vehicles (IoEV). This survey summarizes the current state of research efforts in electric vehicle demand management and aims to shed light on the continued studies.

Description: This paper proposes an opportunistic routing protocol for wireless sensor networks that works on top of an asynchronous duty-cycling medium access control (MAC) protocol. The proposed protocol is designed for applications that are not real-time but still have some requirements on packet delay. The main idea is that if a packet has time to spare, it can wait on a node hoping that it can be aggregated with other packets, resulting in reduced number of transmissions. The forwarders and the packet hold time depend on the energy status of nodes in the network. The simulation results show that the proposed protocol achieves longer network lifetime compared to the other state-of-the-art protocols, while satisfying application delay requirements.