Nakagami衰落信道下多跳合作分集系统的中断率

该文在Nakagami衰落信道下研究了多跳无线网络中合作分集系统的中断性能。根据单节点和多节点中继的情况导出了合作系统再生中继时中断率的数学闭式解,并在高平均信噪比下给出了系统的分集度。理论分析和仿真研究的结果表明多跳合作系统在一定条件下可实现全路由分集,其分集度为所有路由的分集度之和,不是所有合作节点的和,但每支路由的分集度取决于该路由两跳中较小的值。     

Multihop Diversity in Wireless Relaying Channels

Multihop Diversity in Wireless Relaying Channels This paper presents theoretical characterizations and analysis for the physical layer of multihop wireless communications channels. Four channel models are considered and developed: the decoded relaying multihop channel; the amplified relaying multihop channel; the decoded relaying multihop diversity channel; and the amplified relaying multihop diversity channel. Two classifications are discussed: decoded relaying versus amplified relaying; and multihop channels versus multihop diversity channels. The channel models are compared, through analysis and simulations, with the “singlehop” (direct transmission) reference channel on the basis of signal-to-noise ratio, probability of outage, probability of error, and optimal power allocation. Each of the four channel models is shown to outperform the singlehop reference channel under the condition that the set of intermediate relaying terminals is selected intelligently. Multihop diversity channels are shown to outperform multihop channels. Amplified relaying is shown to outperform decoded relaying despite noise propagation. This is attributed to the fact that amplified relaying does not suffer from the error propagation which limits the performance of decoded relaying channels to that of their weakest link.     

Asymptotic Error Rate Analysis of Dual-Branch Diversity over Correlated Rician Channels

Asymptotic error rate expressions are derived for equal gain combining and selection combining on dual-branch correlated Rician channels. The asymptotic error rate performances of three popular diversity combining techniques are compared and some insights are obtained. The impacts of various channel parameters on the asymptotic performances of these diversity combining techniques are studied comprehensively. Some previous observations on diversity performances on correlated Rician channels are unified and further extended.     

Performance of Multilayered Video Encoding and Delivery over Lossy Channels Using a Joint Source-Channel Coding Approach

In this paper, the performance of selected error-control schemes based on forward error-control (FEC) coding for H.263+ video transmission over an additive white Gaussian noise (AWGN) channel is studied. Joint source and channel coding (JSCC) techniques that employ single-layer and 2-layer H.263+ coding in conjunction with unequal error protection (UEP) to combat channel errors are quantitatively compared. Results indicate that with appropriate joint source and channel coding, tailored to the respective layers, FEC-based error control in combination with 2-layer video coding techniques can lead to more acceptable quality for wireless video delivery in the presence of channel impairments. Yong Pei is currently a tenure-track assistant professor in the Computer Science and Engineering Department, Wright State University, Dayton, OH. Previously he was a visiting assistant professor in the Electrical and Computer Engineering Department, University of Miami, Coral Gables, FL. He received his B.S. degree in electrical power engineering from Tsinghua University, Beijing, in 1996, and M.S. and Ph.D. degrees in electrical engineering from Rensselaer Polytechnic Institute, Troy, NY, in 1999 and 2002, respectively. His research interests include information theory, wireless communication systems and networks, and image/video compression and communications. He is a member of IEEE and ACM. James W. Modestino (S′67- M′73- SM′81- F′87) was born in Boston, MA, on April 27, 1940. He received the B.S. degree from Northeastern University, Boston, MA, in 1962, and the M.S. degree from the University of Pennsylvania, Philadelphia, PA, in 1964, both in electrical engineering. He also received the M.A. and Ph.D. degrees from Princeton University, Princeton, NJ, in 1968 and 1969, respectively. He has held a number of industrial positions, including positions with RCA Communications Systems Division, Camden, NJ; General Electronic Laboratories, Cambridge, MA; AVCO Systems Division, Wilmington, MA; GTE Laboratories, Waltham, MA; and MIT Lincoln Laboratories, Lexington, MA. From 1970 to 1972, he was an Assistant Professor in the Department of Electrical Engineering, Northeastern University. In 1972, he joined Rensselaer Polytechnic Institute, Troy, NY, where until leaving in 2002 he was an Institute Professor in the Electrical, Computer and Systems Engineering Department and Director of the Center for Image Processing Research. He has been responsible for teaching and research in the communication, information and signal processing systems area. His specific research interests include communication in fading dispersive channels; detection, estimation and filtering in impulsive or burst noise environments; digital signal, image and video processing; and multimedia communication systems and networks. In 2002 he joined the Department of Electrical and Computer Engineering at the University of Miami, Coral Gables, FL, as the Victor E. Clarke Endowed Scholar, Professor and Chair. He has held visiting positions with the University of California at San Diego, LaJolla, CA (1981–1982); GE Research and Development Center, Schenectady, NY (1988–1989); and Massachusetts Institute of Technology, Cambridge, MA (1995–1996). Dr. Modestino is a past member of the Board of Governors of the IEEE Information Theory Group. He is a past Associate Editor and Book Review Editor for the IEEE TRANSACTIONS ON INFORMATION THEORY. In 1984, he was co-recipient of the Stephen O. Rice Prize Paper Award from the IEEE Communications Society and in 2000 he was co-recipient of the best paper award at the International Packet Video Conference.     

Performance Analysis of Full-Duplex Vehicle-to-Vehicle Relay System over Double-Rayleigh Fading Channels

Mobile Networks and Applications - In this paper, we study the performance of a full-duplex (FD) relay system in vehicle-to-vehicle (V2V) communication. In this relay communication system, the...     

能量收集认知多跳中继网络中断性能分析及优化

针对能量收集认知无线网络中的多跳中继传输问题,该文构建了一种新的具有主网络干扰的功率信标(PB)辅助能量收集认知多跳中继网络模型,并提出单向传输方案.在干扰链路统计信道状态信息场景下,推导了次网络精确和渐近总中断概率闭合式.针对精确总中断概率表达式的复杂性和非凸性,采用自适应混沌粒子群优化(ACPSO)算法对次网络总中断性能进行优化.仿真结果表明,PB功率、干扰约束、次网络跳数、能量收集比率、主接收端数目和信道容量阈值等参数对中断性能影响显著,所提算法能快速和有效地对网络中断性能进行优化.     

Error Performance of DQPSK with EGC Diversity Reception over Fading Channels

This paper derives the average bit error probability (BEP) of differential quaternary phase shift keying (DQPSK) with postdetection equal gain combining (EGC) diversity reception over independent and arbitrarily correlated fading channels. First, using the associated Legendre functions, the average BEP of DQPSK is analyzed over independent Rayleigh, Nakagami-m, and Rician fading channels. Finite-series closed-form expressions for the average BEP of DQPSK over L-branch independent Rayleigh and Nakagami-m fading channels (for integer Lm) are presented. Besides, a finite-series closed-form expression is given for the average BEP of differential binary phase shift keying (DBPSK) with EGC over independent Rician fading channels. Second, an alternative approach is propounded to study the performance of DQPSK over arbitrarily correlated Nakagami-m and Rician fading channels. Relatively simple BEP expressions in terms of a finite sum of a finite-range integral are proposed. Moreover, the penalty in signal to noise ratio (SNR) due to arbitrarily correlated channel fading is also investigated. Finally, the accuracy of the results is verified by computer simulation.     

Outage Performance of Dual-Hop AF Relay Channels with Co-Channel Interferences over Rayleigh Fading

This paper studies the outage performance of a dual-hop amplify-and-forward (AF) relay fading channel in an interference-limited environment. The relay and destination nodes are corrupted by multiple co-channel Rayleigh interferences. New exact closed-form expressions for the outage probability for channel-state-information (CSI)—assisted relay, in which gain is dependent on previous hop CSI and interference, are derived. Monte Carlo simulations are performed to verify the obtained theoretical results. For the cases where the number of interferers at the relay and the destination node is equal, we derive novel expressions for outage probability upper and lower bounds.     

能量收集认知多跳中继网络中断性能分析及优化

针对能量收集认知无线网络中的多跳中继传输问题,该文构建了一种新的具有主网络干扰的功率信标(PB)辅助能量收集认知多跳中继网络模型,并提出单向传输方案。在干扰链路统计信道状态信息场景下,推导了次网络精确和渐近总中断概率闭合式。针对精确总中断概率表达式的复杂性和非凸性,采用自适应混沌粒子群优化(ACPSO)算法对次网络总中断性能进行优化。仿真结果表明,PB功率、干扰约束、次网络跳数、能量收集比率、主接收端数目和信道容量阈值等参数对中断性能影响显著,所提算法能快速和有效地对网络中断性能进行优化。     

Rice衰落信道下选择中继的性能分析与功率分配算法

本文针对无线传感器网络,研究了Rice衰落信道下基于选择中继的两跳译码转发系统的协同中继传输性能与功率分配算法.文中利用概率密度函数推导了选择中继协同传输的中断概率、误符号率的闭式表达式,并给出了高信噪比时的渐近性表达式;然后根据渐近性能进行源与中继节点间的功率优化,进一步提升系统传输性能;最后用蒙特卡洛仿真验证了结果的有效性.仿真结果显示,理论值与仿真结果基本一致,优化功率分配后的传输性能接近于搜索法得到的传输性能,但计算复杂度明显降低.     

Distortion-Driven Video Streaming over Multihop Wireless Networks with Path Diversity

Multihop networks provide a flexible infrastructure that is based on a mixture of existing access points and stations interconnected via wireless links. These networks present some unique challenges for video streaming applications due to the inherent infrastructure unreliability. In this paper, we address the problem of robust video streaming in multihop networks by relying on delay- constrained and distortion-aware scheduling, path diversity, and retransmission of important video packets over multiple links to maximize the received video quality at the destination node. To provide an analytical study of this streaming problem, we focus on an elementary multihop network topology that enables path diversity, which we term "elementary cell." Our analysis is considering several cross-layer parameters at the physical and medium access control (MAC) layers, as well as application-layer parameters such as the expected distortion reduction of each video packet and the packet scheduling via an overlay network infrastructure. In addition, we study the optimal deployment of path diversity in order to cope with link failures. The analysis is validated in each case by simulation results with the elementary cell topology, as well as with a larger multihop network topology. Based on the derived results, we are able to establish the benefits of using path diversity in video streaming over multihop networks, as well as to identify the cases where path diversity does not lead to performance improvements.     

Performance Improvements Provided by Route Diversity in Multihop Wireless Networks

In multihop wireless networks, the variability of channels results in some paths providing better performance than other paths. Although it is well known that some paths are better than others, a significant number of routing protocols do not focus on utilizing optimal paths. However, cooperative diversity, which is an area of recent interest, provides techniques for efficiently exploiting path and channel diversity. This paper examines the potential performance improvements offered by path diversity. Three settings are examined, namely, where the path loss and channel correlation are neglected, where path loss is considered, but channel correlation is neglected, and where path loss and channel correlation are both accounted for. It is shown that, by exploiting path diversity, dramatic improvements in the considered route metric may be achieved. Furthermore, in some settings, if the link statistics are held constant, then when path diversity is exploited, the route metric improves with path length. This implies that, if links statistics are fixed and if sufficient path diversity exists, then paths with more hops tend to support higher bit rates than paths with fewer hops. It is shown that such behavior occurs when a particular map has a nonzero fixed point.     

Performance Characterization of Spatial Diversity Based Optical Wireless Communication over Atmospheric Turbulence Channels

Optical wireless communication is regarded as the next-generation high-speed technology. It has demonstrated its capability to deliver data faster than any other state-of-the-art wireless communication technique. This technology has drawn attention as a means of implementing reliable high capacity outdoor systems that cannot be implemented by conventional fiber optics. It has emerged recently as an efficient solution to match the larger bandwidth and high data rates requirement of the upcoming wireless communication systems. However, although FSO (free space optics) system has many appealing features, it has rather disappointing performance for long links due to the degrading effects of atmospheric turbulence-induced fading. In the presence of such type of performance impairments, the received signal exhibits random intensity fluctuations, which increase the BER (bit error-rate), where the severe weather conditions can have a detrimental impact on the performance, which may result in an inadequate availability. The MIMO wireless optical procedure, in which the spatial dimensions are used to improve the reliability and spectral efficiency of point-to-point links, provides a promising approach to mitigate turbulence effects due to its powerful performance enhancing capabilities.In this paper, we investigate a terrestrial atmospheric FSO communication system operating under the influence of strong atmospheric turbulences. Additionally, the MIMO technique with equal gain combining (EGC) is used in this work to enhance the data rate of the proposed system. Atmospheric turbulence impacts are modeled as a lognormal channel with due regard for geometric losses. With the use of NRZ line coding, an FSO highly sensitive receiver using either avalanche photodetector (APD) or PIN is designed and simulated for best system performance. The preference is achieved by using Bessel and Gaussian filters. It has been found that APD receiver using Gaussian filter is suitable for long-range links with APD gain value of 3. Also, the selection of APD gain is critical to the system performance. In addition, the optimal value of APD gain required for best system performance decreases as the size of the MIMO technique increases. The achievable performance improvements including received power levels, BER and Q-factor are also discussed. The results show that the system with optical amplifier at the transmitter gives an optimum performance. In addition the system performance is enhanced in most weather conditions by using an amplified 2×2 MIMO-FSO system with booster amplifier.     

Multi-antenna Decode and Forward Relay Selection over Nakagami-m Fading Channels

This paper analyzes the performance of opportunistic relay under aggregate power constraint in Decode-and-Forward (DF) relay networks over independent, non-identical, Nakagami-m fading channels, assuming multiple antennas are available at the relay node. According to whether instantaneous Signal-to-Noise Ratio (SNR) or average SNR can be exploited for relay selection, two opportunistic relay schemes, opportunistic multi-antenna relay selection (OMRS) and average best relay selection (ABRS) are proposed. The closed form expressions of outage probability and error performance for binary phase shift keying (BPSK) modulation of OMRS and ABRS are determined using the moment generating function (MGF) of the total signal-to-noise ratio (SNR) at the destination. Simulations are provided to verify the correctness of theoretical analysis. It is observed that OMRS is outage-optimal among multi-antenna relay selection schemes and approaches the Beamforming (BF) scheme known as theoretical outage-optimal very closely. Compared with previous single-antenna Opportunistic Relaying (OR) scheme, OMRS brings remarkable performance improvement obtained from maximum ratio combining (MRC) and beamforming, which proves that multiple antennas at the relays could provide more array gain and diversity order. It also shows that the performance of ABRS in asymmetric channels is close to OMRS in the low and median SNR range.     

Asymptotic Performance of Linear Receivers in MIMO Fading Channels

Linear receivers are an attractive low-complexity alternative to optimal processing for multiple-antenna multiple-input multiple-output (MIMO) communications. In this paper, we characterize the information-theoretic performance of MIMO linear receivers in two different asymptotic regimes. For fixed number of antennas, we investigate the limit of error probability in the high-signal-to noise-ratio (SNR) regime in terms of the diversity-multiplexing tradeoff (DMT). Following this, we characterize the error probability for fixed SNR in the regime of large (but finite) number of antennas.As far as the DMT is concerned, we report a negative result: we show that both linear zero-forcing (ZF) and linear minimum mean- square error (MMSE) receivers achieve the same DMT, which is largely suboptimal even in the case where outer coding and deAcircnot coding is performed across the antennas. We also provide an apAcircnot proximate quantitative analysis of the markedly different behavior of the MMSE and ZF receivers at finite rate and nonasymptotic SNR, and show that while the ZF receiver achieves poor diversity at any finite rate, the MMSE receiver error curve slope flattens out progressively, as the coding rate increases. When SNR is fixed and the number of antennas becomes large, we show that the mutual information at the output of an MMSE or ZF linear receiver has fluctuations that converge in distribution to a Gaussian random variable, whose mean and variance can be characterized in closed form. This analysis extends to the linear reAcircnot ceiver case a well-known result previously obtained for the optimal receiver. Simulations reveal that the asymptotic analysis captures accurately the outage behavior of systems even with a moderate number of antennas.     

Performance of Transmit Antenna Selection and Maximal-Ratio Combining in Dual Hop Amplify-and-Forward Relay Network over Nakagami-m Fading Channels

In this paper, we study end-to-end performance of transmit antenna selection (TAS) and maximal ratio combining (MRC) in dual hop amplify-and-forward relay network in flat and asymmetric Nakagami-m fading channels. In the network, source and destination communicate by the help of single relay and source-destination link is not available. Source and destination are equipped with multiple antennas, and relay is equipped with single antenna. TAS and MRC are used for transmission at the source and reception at the destination, respectively. The relay simply amplifies and forwards the signal sent by the source to the destination by using channel state information (CSI) based gain or fixed gain. By considering relay location, for CSI based and fixed relay gains, we derive closed-form cumulative distribution function, moments and moment generating function of end-to-end signal-to-noise ratio, and closed-form symbol error probability expression. Moreover, asymptotical outage probability and symbol error probability expressions are also derived for both CSI based and fixed gains to obtain diversity order of the network. Analytical results are validated by the Monte Carlo simulations. Results show that diversity order is minimum of products of fading parameter and number of antennas at the end in each hop. In addition, for optimum performance the relay must be closer to the source when the diversity order of the first hop is smaller than or equal to that of the second hop.     

双向中继信道中物理层网络编码的性能分析

针对双向中继信道,文章研究采用放大转发协议的物理层网络编码的性能.在考虑直传链路下,给出了3时隙网络编码的可达速率.在高信噪比条件下,推导了 3时隙物理层网络编码方案和2时隙物理层网络编码方案的中断概率近似表达式.通过仿真,验证了理论分析结果.同时,对3时隙物理层网络编码方案中继节点的功率分配因子进行了优化,在中继节点处于不同位置下分节点等功率和不同功率对不同方案进行了最大和速率的仿真,结果表明3时隙物理层网络编码可以利用网络的非对称性提高性能.     

Performance of Physical-Layer Network Coding in Asymmetric Two-Way Relay Channels

In this paper, we study the performance of physical-layer network coding in asy- mmetric two-way relay channels using four different cases having different poor channels： phase asymmetry, downlink asymmetry, uplink asymmetry and node asymmetry. The decision and mapping rule for symmetric and asymmetric cases are studied. The performance in terms of bit error rate for each case will be studied and analysed by computer simulation. Analytical and simulation results show that uplink asymmetry is the worst case; intra-phase asymmetry and unreliable uplink channels will more severely affect the performance degradation, which is caused by channel asymmetry.     

Performance Analysis of Relay Selection with Enhanced Dynamic Decode-and-Forward and Network Coding in Two-Way Relay Channels

Wireless Personal Communications - Relay selection (RS), enhanced dynamic decode-and-forward (EDDF), and network coding (NC) have been proven to effectively improve the performance of cooperative...     

A Simple Technique to Enhance Diversity Order in Wireless Fading Relay Channels

Relaying has proven to be an effective method of providing additional spatial diversity on wireless fading channels. This paper proposes a system of XORing at the relay with iterative maximum a posteriori (MAP) decoding at the destination. An XOR-relay offers an increased number of diversity paths, enabling the destination to construct a cycle- free decoding structure, and resulting in an enhanced diversity order. Simulation results clearly show that the proposed scheme approaches 3rd-order diversity in the topology of second diversity paths, with no need for additional resources.