Cooperative quadrature physical layer network coding in wireless relay networks

This paper proposes a cooperative quadrature physical layer network coding (CQPNC) scheme for a dual‐hop cooperative relay network, which consists of two source nodes, one relay node and one destination node. All nodes in the network have one antenna, and the two source nodes transmit their signals modulated with quadrature carriers. In this paper, a cooperative quadrature physical layer network coded decode‐and‐forward (DF) relay protocol (CQPNC‐DF) is proposed to transmit the composite information from the two source nodes via the relay node to the destination node simultaneously to reduce the number of time slots required for a transmission. The proposed CQPNC‐DF relay protocol is compared with time‐division multiple‐access amplify‐and‐forward (TDMA‐AF), TDMA‐DF, cooperative network coded DF (CNC‐DF) and cooperative analog network coded AF (CANC‐AF) relay protocols to demonstrate its effectiveness in terms of bit error rate (BER) and system throughput under different propagation conditions. The simulation results reveal that the proposed CQPNC‐DF relay protocol can significantly improve the network performance. Compared with two TDMA schemes and CNC‐DF, the proposal can provide up to 100% and 50% throughput gains, respectively. Moreover, no matter what the scene, the proposed scheme always has the lowest BER in the low SNR region. Copyright © 2013 John Wiley & Sons, Ltd.     

多用户SIMO-OFDM系统中的协作分集性能分析

协作分集使得在多用户环境下,具有单天线的多个终端可以共享彼此的天线,以形成一个虚拟的天线阵列结构,实现空域分集。首先介绍了多用户SIMO—OFDM系统中的两种协作方式,放大前传和译码前传。然后针对源结点和目的结点之间是否存在路径损耗,提出了一种基于信道状态信息的选择中继协作方式,并对系统性能进行了理论和仿真分析。仿真结果表明,这种基于信道状态信息的选择中继协作方式可以获得较好的系统性能。     

A New Solution for Simple Cooperative Relaying

In this paper we present a new simple cooperative relaying scheme. The proposed scheme is compared with simple cooperative schemes with virtual orthogonal space time block coding (OSTBC) and quasi orthogonal space time block coding (QOSTBC). Every of these three schemes includes one base station with two antennas, two relay stations each with a single antenna and one mobile station with a single antenna. The aim of the proposed scheme is to preserve, as much as it is possible bit error rate (BER) performance of the cooperative scheme with virtual OSTBC, but with increased code rate. It is shown that the presented scheme obviously outperforms simple cooperative scheme with virtual QOSTBC, while in comparison with simple cooperative scheme with virtual OSTBC has very similar BER performance and increased code rate.     

Adaptive Path Selection Scheme with Combining for Multiple Relaying Cooperative Communications Networks

In future communications, cooperative communications with relay networks will be one of the most effective schemes to enlarge the coverage area and to boost the data rate. In the recent research results, the path selection, power allocation, and relay protocols on relay networks are the most important factors to improve the system performance. However, the channel quality of the direct transmission path and the relaying path has an influential effect on the performance of relay networks. Therefore, in this paper, we propose a best relaying path selection (BRPS) scheme to obtain the path diversity to improve the system capacity and data rate for cooperative networks (CNs). Simulation results show that the more the relay nodes are selected, the lower the bit error rate (BER) is. The proposed BRPS scheme obtains a high concession between both BER and system capacity for CNs.     

联合网络编码和中继选择的协作传输方案及其性能分析

研究了Nakagami信道中联合网络编码和双向协作中继选择的中断与平均误码率的性能,基于3个时隙的网络编码方案提出了一种最小化较差用户误码率的协作中继选择策略。在Nakagami信道下,从双向通信的角度,通过理论分析得出其中断概率和平均误码率的解析式和渐近式,同时推导了无协作中继选择时网络编码的中断概率和平均误码率解析式。通过理论分析发现,当Nakagami信道衰落参数降低时,联合网络编码的协作中继选择方案相对于无协作中继选择时的性能增益将逐渐升高。数值仿真实验结果表明,所提策略的平均误码率性能要显著高于无协作中继选择时的网络编码性能。     

Antenna/relay selection for coded cooperative networks with AF relaying

In this paper, we consider antenna/relay selection for coded cooperative networks in an effort to improve their end-to-end performance by improving the detection reliability at the relay nodes. Considering amplify-and-forward (AF) relaying, we analyze a previously proposed distributed coded cooperation scheme in conjunction with antenna/relay selection. Specifically, we derive upper bounded expressions for the bit error rate assuming M-ary phase shift keying (M-PSK) transmission. Our analytical results show that the maximum diversity order of the system is maintained for the entire range of symbol error rate of interest, unlike the case without antenna/relay selection. Several numerical and simulation results are presented to demonstrate the efficacy of the proposed scheme.     

基于正交处理的网络编码方法及其性能分析

为有效传输多用户多中继网络信息,在线性网络编码的基础上给出一种基于正交处理的网络编码方法（NCOP, network coding based on orthogonal process）,该编码方式结合正交低频子载波处理思想,将传输数据正交化,利用处理后数据正交性实时传输并解码需要用户数据,进一步降低系统中断概率,提高分集增益。理论分析了该编码方法的系统中断概率和平均误码率,分析和仿真结果表明在多用户协作网络的应用中,NCOP中断性能及误码性能均优于线性网络编码。     

一种利用机器学习优化MIMO窃听信道天线选择的方法

为保障多输入多输出窃听信道系统中信息传输的保密性,提出了一种基于机器学习的天线选择方案。首先利用机器学习解决分类问题准确率高、处理大数据高效这一优势,设计了基于奇异值分解的特征值提取、基于信干噪比的标签赋值方案,建立了k最近邻分类器和逻辑回归分类器选择最优天线最大化保密性能(可达保密速率和保密中断概率)。与传统天线选择方案相比,所提方案获得了几乎一致的保密性能,并且大幅降低了系统的选择复杂度和误比特率。     

一种改进的大规模MIMO发射天线选择算法

为了降低天线选择算法在大规模多输入多输出（Multiple-Input Multiple-Output,MIMO）系统下的误码率和复杂度,以用户端接收的总功率为优化目标,提出一种最大化所有用户接收总功率的天线选择算法。该算法将优化目标函数转化为凸函数,并利用凸优化方法求得其有效解。仿真结果表明,所提天线选择算法与传统的最大和容量算法相比,具有较好的系统误码率性能,且运算复杂度低,但系统容量有所降低。     

New Solutions for Cooperative Relaying Implementation of OSTBC with 3/4 Code Rate

In this paper we propose two new cooperative relaying schemes which enable distributed implementation of the orthogonal space time block coding (OSTBC) with 3/4 code rate. These proposed schemes are compared with cooperative relaying scheme with virtual OSTBC and 1/2 code rate. The considered schemes are used for creating virtual 4 × 1 multiple input–single output (MISO) channel, and include one base station with two antennas, two relay stations each with a single antenna and one mobile station with a single antenna. Obtained results show that in the case of the same bit rate the proposed schemes provide better bit error rate (BER) performances than virtual OSTBC with 1/2 code rate. On the other side, for the same symbol constellations the proposed schemes have almost identical BER performances as virtual OSTBC with 1/2 code rate, but with a benefit of 1.5 times increased code rate.     

Turbo-BLAST系统中天线选择和功率分配算法

提出一种适用于Turbo-BLAST系统的自适应天线选择和功率分配算法,所提算法以误比特率为优化目标,并且考虑了信道估计误差的影响.在总功率约束条件下,采用所提算法进行天线选择和自适应功率分配,并利用软干扰抵消算法对接收信号进行迭代检测,以进一步改善系统性能.仿真结果表明:采用所提算法可以显著改善系统的误比特率性能.     

基于信道编码及空时编码级联的两用户协同分集

传统协同分集通过使网络中各单天线用户共享彼此天线,形成虚拟多天线阵列来实现空间分集,使得体积和功耗受限的网络终端也能获得分集增益,然而这并没有将信道编码和空时编码结合起来以使系统得到编码增益。为了能够获得编码增益来进一步改善系统性能,本文提出了一种基于信道编码和分布式空时分组码级联方式下的两用户协同分集方案,并且在准静态的瑞利衰落信道下对系统误码性能进行了理论推导和系统仿真,给出了误比特率的上限解析表达式。在协同用户间信道存在噪声的情况下,我们分别对CRC-DSTBC和CC-DSTBC级联下的发射方案进行了性能分析和系统仿真。仿真结果表明:即使协同用户间的信道存在噪声,本文所提出的协同分集方案与传统协同分集相比,不但获得了分集增益,同时也得到了编码增益,系统误比特率大大降低,从而显著提高了系统性能,并且这也和理论分析相吻合。     

Channel and queue aware joint relay selection and resource allocation for MISO-OFDMA based user-relay assisted cellular networks

User-relay assisted orthogonal frequency division multiple access (OFDMA) networks are cost-effective solutions to meet the growing capacity and coverage demands of the next generation cellular networks. These networks can be used with multiple antennas technology in order to obtain a diversity gain to combat signal fading and to obtain more capacity gain without increasing the bandwidth or transmit power. Efficient relay selection and resource allocation are crucial in such a multi-user, multi-relay and multi-antenna environment to fully exploit the benefits of the combination of user-relaying and multiple antennas technology. Thus, we propose a channel and queue aware joint relay selection and resource allocation algorithm for multiple-input single-output (MISO)-OFDMA based user-relay assisted downlink cellular networks. Since, the proposed algorithm is not only channel but also queue-aware, the system resources are allocated efficiently among the users. The proposed algorithm for the MISO-OFDMA based user-relay assisted scheme is compared to existing MISO-OFDMA based non-relaying and fixed relay assisted schemes and it is also compared with the existing single-input single-output (SISO)-OFDMA based user-relay assisted scheme. Simulation results revealed that the proposed scheme outperforms the existing schemes in terms of cell-edge users’ total data rate, average backlog and average delay.     

基于DSTBC-MC-CDMA的无线网络协同发射分集系统

协同分集(cooperative diversity)技术通过使网络中各单天线用户共享彼此天线,形成虚拟的多天线阵列来实现发射或接收分集,可以有效地提高系统性能。该文提出无线网络中频率选择性衰落信道环境下的一种基于分布式空时分组码(Distributed Space Time Block Code, DSTBC)和MC-CDMA的协同发射分集方案,并给出了系统实现。建立了误码模型,探讨了协同用户间的信道状态信息(CSI)对系统误码性能的影响,分析了误码性能的上限,并给出了仿真结果。结果表明,DSTBC-MC-CDMA系统相对于未协同的MC-CDMA系统,获得了明显的性能增益。     

A fuzzy decision scheme for relay selection in cooperative wireless sensor network

In energy‐constrained military wireless sensor networks, minimizing the bit error rate (BER) with little compromise on network lifetime is one of the most challenging issues. This paper presents a new relay selection based on fuzzy logic (RSFL) scheme which provides balance between these parameters. The proposed scheme considers node's residual energy and path loss of the relay‐destination link as the input parameters for the selection of the relay node. The relay node selection by fuzzy logic is based on prioritizing higher residual energy and minimum path loss. To evaluate the performance on wireless sensor network, we compare the proposed scheme with the three existing relay selection strategies, ie, random, maximum residual energy based relay selection (MaxRes), and minimum energy consumption based relay selection (MinEnCon). The simulation results of the proposed scheme in terms of network lifetime, BER, Network Survivability Index (NSI), and average energy of network nodes have been presented and compared with different relay selection schemes. The simulation results show that the proposed RSFL scheme has the lowest BER, moderate network lifetime, average energy, and NSI.     

Distributed polar-coded OFDM based on Plotkin’s construction for half duplex wireless communication

A Plotkin-based polar-coded orthogonal frequency division multiplexing (P-PC-OFDM) scheme is proposed and its bit error rate (BER) performance over additive white gaussian noise (AWGN), frequency selective Rayleigh, Rician and Nakagami-m fading channels has been evaluated. The considered Plotkin’s construction possesses a parallel split in its structure, which motivated us to extend the proposed P-PC-OFDM scheme in a coded cooperative scenario. As the relay’s effective collaboration has always been pivotal in the design of cooperative communication therefore, an efficient selection criterion for choosing the information bits has been inculcated at the relay node. To assess the BER performance of the proposed cooperative scheme, we have also upgraded conventional polar-coded cooperative scheme in the context of OFDM as an appropriate bench marker. The Monte Carlo simulated results revealed that the proposed Plotkin-based polar-coded cooperative OFDM scheme convincingly outperforms the conventional polar-coded cooperative OFDM scheme by 0.5 ~ 0.6 dBs over AWGN channel. This prominent gain in BER performance is made possible due to the bit-selection criteria and the joint successive cancellation decoding adopted at the relay and the destination nodes, respectively. Furthermore, the proposed coded cooperative schemes outperform their corresponding non-cooperative schemes by a gain of 1 dB under an identical condition.     

Power allocation for AF relaying aided spatial modulation in the presence of imperfect channel state information

By combining Spatial modulation (SM) with cooperative communication, the diversity gain brought by cooperative relaying and high rate of SM can be obtained. In this paper, considering amplify-and-forward (AF) protocol, the performance of cooperative SM system with imperfect channel state information (CSI) over Rayleigh channel is analyzed. According to the performance analysis, the moment generating functions (MGFs) of effective signal-to-noise ratios (SNRs) are derived. With the MGFs, closed-form expressions of the error probability of antenna index detection and the error probability of symbol detection for imperfect CSI are achieved. Thereby, the approximate overall average bit error ratio (BER) is obtained, and these theoretical expressions include those under perfect CSI as special cases. Besides, the asymptotically approximate BER for large SNR is also derived. Based on this, a suboptimal power allocation (PA) scheme is developed, and the corresponding PA coefficients are attained by minimizing the asymptotical BER. As a result, closed-form PA can be attained for the system with multiple receive antennas. Computer simulations show that the theoretical BERs are close to the corresponding simulated results, which illustrates the effectiveness of the derived theoretical expressions. Compared with the conventional equal PA scheme, the proposed PA scheme enhances the BER performance efficiently.     

一种基于非正交信道的分布式中继选择及功率分配方法

针对非正交两跳多中继协作通信系统中的分布式中继选择问题,提出了一种基于非正交信道的中继选择准则,简化了系统的设计。分析了其误码率性能,给出了其解析表达式和以总功率为约束条件下的最优功率分配方案。仿真结果表明,最佳中继选择准则明显优于传统的中继选择准则,且在最优功率分配方案下,可以获得明显的分集增益,系统的误码率显著下降。     

正交多用户CD-DCSK方案的设计及性能分析

为了进一步提升现有多用户混沌键控系统的信息传输速率和误码率(BER) 性能,该文提出一种正交多用户CD-DCSK(OMU-CD-DCSK)系统。该系统在差分混沌移位键控(DCSK)的基础上结合了相关延迟移位键控(CDSK),每个时隙中利用正交的Walsh码序列可以传输N bit的多用户信息,然后通过正交调制技术进一步提升传输速率。在接收端,采用滑动平均滤波器降低噪声方差,改善误码性能,之后进行相关解调即可恢复多用户信息比特。推导了多径瑞利衰落信道下系统的理论BER,并通过蒙特卡罗仿真实验进行了验证。此外,还定义了系统的综合效用,用于评估混沌系统的综合性能。与其他混沌键控系统相比,OMU-CD-DCSK的综合性能有明显优势,因此具有较好的实用价值。     

Turbo-BLAST系统中基于容量的天线选择和功率分配算法

在不完全信道状态信息条件下,提出了一种适用于Turbo BLAST系统的天线选择和功率分配算法。所提算法以信道容量最大化为准则,从所有天线中选取一组天线子集用于发射,并对选择的天线子集进行注水功率分配,以充分利用Turbo BLAST系统的空间复用增益并提高信道容量。在接收端,采用Turbo原理对接收信号进行迭代检测以改善系统的误比特率性能。仿真结果表明采用所提算法不仅可以显著提高系统的信道容量, 而且误比特率性能也得到明显的改善。