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。     

两级中继选择的协作CR-NOMA网络性能分析

本文研究了中继选择方案对协作下认知非正交多址（CR-NOMA）网络中断性能的影响,提出了一种两级中继选择方案。第一时隙在保证主用户服务质量的基础上,次级网络源节点向认知中继集群广播叠加信号。第二时隙认知中继提供解码转发服务,协助源节点传输信息。基于上述假设,推导了次级用户中断概率的闭合表达式并给出了分析结果。证明相比于部分中继选择策略,两级中继选择策略可以达到更好的中断性能和更大的分集增益。同时本文的分析结果验证了备选中继节点数目和功率分配因子对系统中断性能的影响,蒙特卡罗仿真验证了理论结果。      

多用户多中继系统下协作NOMA的中断性能

在基于非正交多址接入技术(NOMA)的多用户多中继协作中继网络中,为优先满足混叠信号中的时延敏感信息的服务质量(QoS)需求,对功率因子进行了简单分析,进而找到了关于信道增益的解码限制条件。在给定中继的情况下,根据解码限制条件建立用户集合,进而找到可以使高QoS信号速率最大化的用户中继对作为最佳“用户-中继”来传递信号。并且对该“用户-中继”选择方案下的系统中断概率的表达式进行推导并求出了其渐进式。仿真结果验证了推导结果的正确性,系统的中断概率随着节点数目的增多而降低,而当信噪比趋于无穷时,系统的分集增益取决于用户数目和中继数目。且与已有文献进行对比,本文提出的用户中继匹配方案的中断性能相对较好。     

基于解码重传的最佳协作中继选择策略

近年来提出的协作分集技术通过使网络中各单天线用户共享彼此天线以形成虚拟多天线阵列,从而可以显著提高网络容量,也使得其备受科研工作者的关注。提出了基于解码重传（DaF）下的被动式最佳协作中继选择准则,该准则是通过推导协作中继传输系统的误符号率而得出的。在总功率限制下,可以证明基于解码重传下的机会中继在中断性能上考虑是最佳的,更确切地说,它的中断性能和利用全部候选中继传输的最佳解码重传策略是一样的。     

协作认知无线电网络频谱检测性能分析

阴影热点区域环境复杂,信号传输损耗更大,协作中继转播功能能够提高通信性能.文章对阴影衰落信道上多中继认知无线电系统的联合频谱检测概率进行了分析,计算基于解码转发机制的中继器的成功解码概率;分析中继器对于一级和二级用户的中断概率的影响.误警率为0.1和0.05条件下的检测概率、一级系统和二级系统的中断概率等性能的仿真结果表明:中继器协作检测可以提高检测性能;协作中继转播可以在保证授权用户所需中断概率条件下降低认知用户的中断概率;结合联合频谱检测和协作中继转播,能提高系统通信性能,提高频谱使用效率.     

两阶段中继选择策略下SWIPT-CR-NOMA网络的中断性能分析

针对采用无线携能传输(SWIPT)的多中继协作底层认知NOMA网络,提出一种基于NOMA和串行干扰消除协议的两阶段中继选择策略(TSRS),次级网络源节点和所选中继采用相同的功率分配生成多用户叠加信号,中继只利用采集能量提供解码转发服务。推导了用户中断概率的闭合表达式,进行了蒙特卡洛仿真验证,分析了功率分配因子、能量分裂参数、干扰温度限和中继数量等系统参数对中断性能的影响。仿真结果表明,所提方案可显著提升协作系统中断性能。      

D2D辅助的协作中继NOMA系统中TSRS策略及其中断性能分析

该文研究了D2D辅助的协作中继NOMA（DC-NOMA）网络,在中继用户（RU）转发信息的第二时隙,利用RU到蜂窝中心用户（CCU）的D2D通信链路传输新的信号。为了提高传输可靠性,设计了新的信号检测策略,通过完全利用边缘信息消除了用户间的干扰。基于新的信号检测策略,提出了一种两阶段中继选择策略（TSRS）。在满足蜂窝边缘用户（CEU）可靠接收的中继集合中,选择使CCU成功解码概率最大的中继。为了评估所提出的DC-NOMA方案,推导了每个用户的确切中断概率且通过仿真得到验证。仿真结果表明,在高信噪比区域,该文所提出的基于新的信号检测策略的DC-NOMA在TSRS方案下的中断性能优于部分中继选择方案（PRSS）和传统的DC-NOMA。特别地,增大中继数量可有效提高DC-NOMA系统的中断性能。      

硬件损伤下能量采集双向中继网络系统中断性能分析

在硬件损伤条件下分析了能量采集双向中继网络的系统中断性能,该网络的终端节点对直达链路信号和中继链路信号分别进行选择合并（Selection Combining, SC）和最大比合并（Maximum Ratio Combining,MRC）。首先,推导了该网络在SC方案下的系统中断概率,并在此基础上得到了由硬件损伤而引起的两种效应,即中继协作效应和系统协作效应。然后,推导了该网络在MRC方案下的系统中断概率。最后,通过仿真分析了硬件损伤及系统参数对系统中断性能的影响,并比较了该网络在SC方案和MRC方案下的系统中断性能。仿真结果表明:在硬件损伤条件下,MRC方案仅引起系统协作效应;相比于MRC方案,SC方案对硬件损伤更加敏感;当数据传输速率低于系统协作门限时,采用MRC能够实现更好的系统中断性能。      

非理想SIC下SWIPT-CR-NOMA网络中断性能分析

针对采用无线携能通信的多中继底层协作认知非正交多址接入网络,提出一种两阶段中继选择策略。认知中继执行功率划分的无线携能通信协议为次级用户提供解码转发服务,其能量开销源于所采集到的能量。考虑了实际的非正交多址接入网络中,中继节点与次级用户均无法完全消除多址干扰,即无法实现理想连续干扰消除。在干扰阈值约束下,推导了非理想连续干扰消除下两次级用户端中断概率的精确表达式,并通过蒙特卡洛仿真验证其正确性。此外,定量分析了各系统相关参数（最大发射功率、干扰阈值、功率分配系数等）的选取对次级用户中断性能的具体影响。结果表明,在相同的系统参数设置下,所提方案次级用户中断性能远优于现有部分中继选择方案。      

机会式网络编码在分布式协作网络中的应用

协作通信技术是一种新型的空间分集技术,用户节点彼此共享天线,获取分集增益,有效提高系统性能。网络编码能够减小系统中断概率,解决网络拥塞问题,从而提高传输有效性。文章主要研究了机会式网络编码在分布式天线协作通信系统中的应用,分析了其中断概率。结果表明网络编码可以节省时间成本,提高系统吞吐量。其中,当用户和中继之间不存在误码时,网络编码能够减小系统的中断概率;当用户和中继之间存在误码时,机会式网络编码的中断概率最低。     

Adaptive Transmission Scheme for Mixed Multicast and Unicast Traffic in Cellular Systems

Wireless communication systems have been developed to support users' various requirements. Multicast and unicast transmission schemes are proposed for various types of services. The multicast transmission is known as an efficient method for group-data transmission. The data rate for multicast transmission depends on the instantaneous worst channel user. On the other hand, unicast transmission exploits wireless channel variation and achieves a multiuser diversity gain. In this paper, we evaluate and compare the system performance of multicast and unicast transmission schemes in terms of system capacity, worst average channel user's capacity, and outage probability for varying cell environments. We also propose a novel hybrid scheduling scheme for mixed multicast and unicast traffic services and compare the proposed scheme with the conventional scheme.      

Performance analysis of two-way relay cooperation underlay cognitive radio networks based on WIPT

The two-way relay cooperation for underlay cognitive radio networks based on WIPT was presented,where secondary system adopted the two-way relay cooperative transmission.First,the relay adopted a power splitting protocol to harvest energy and to decode information transmitted by secondary users,then the relay forwarded information to two secondary users by using the harvested energy.Subsequently the exact expression of the outage probability,the ergodic capacity and energy efficiency of the secondary user system were derived.Finally,numerical simulation discusses the impact on the system performance with regard to secondary transmission power.The results reveal that the two-way relay cooperation effectively reduces the outage probability of data transmission.The capacity and energy efficiency of the system reaches optimal level when the power allocation coefficient is 0.5.     

基于NOMA的D2D辅助中继系统性能分析与优化

本文针对两阶段NOMA(Non-Orthogonal Multiple Access)-D2D((Device-to-Device)辅助中继场景提出了一种功率优化算法，推导分析了各用户的中断概率。构建了以最大化系统各态历经容量为目标的优化问题，由于一、二两阶段通信用户的差异性，重点优化了对提升系统容量起决定作用的第一阶段功率分配因子，分析证明了原优化问题存在极值点，并利用凸函数性质获得了优化的功率分配因子，并且进一步推导分析了各个用户的中断概率。仿真结果表明，理论推导的中断概率值与仿真结果完全一致，证明了推导的正确性，本文提出的功率优化算法能显著提高系统容量，且降低了中断概率。例如当SNR为35dB时，本文算法可以提高约17.6%的系统容量，而作为辅助中继用户的中断概率大约降低了81.3%。      

NOMA-D2D协作无线系统的物理层安全

针对未来海量用户设备接入的物理层安全（physical layer security，PLS）应用需求，提出了一种组合非正交多址接入（non-orthogonal multiple access，NOMA）、终端直通（device-to-device，D2D）与中继协作的NOMA-D2D协作无线系统PLS模型。该模型由采用发射天线选择（transmit antenna selection，TAS）的基站、分别作为基站和D2D发射端的NOMA远端蜂窝用户、D2D接收端以及被动窃听者组成，其中的D2D发射端承担基站的 NOMA 近端用户和解码转发中继两种角色。利用高斯—切比雪夫正交定理推导两种 TAS 方案下NOMA-D2D协作无线系统的安全中断概率、非零安全容量概率以及渐近安全中断概率的近似表达式。数值计算和仿真实验验证了NOMA-D2D协作无线系统PLS性能分析的准确性；在基站总功率恒定时增大分配给远端蜂窝用户的功率能有效提升NOMA-D2D协作无线系统的PLS性能。     

Exploiting cooperative diversity with non-orthogonal multiple access over slow fading channel

Non-orthogonal multiple access (NOMA) has attracted a significant attention to the research community as a potential candidate for 5G or future radio access. This article presents a NOMA-based cooperative network where a transmitter considered as a base station communicates simultaneously with two users treating as a far user and a near user via the help of a half-duplex decode-and-forward relay. We investigate the outage probability and the outage capacity of the proposed network over independent Rayleigh slow fading channels. Closed-form expressions of the outage probabilities are derived for both users. Approximate outage capacity of the users are also investigated at high signal to noise ratio regime. It has been shown that the proposed cooperative NOMA can achieve superior performance compared to the non-cooperative NOMA in terms of outage probability. The tightness between the simulation and theoretical results confirms the efficiency of the proposed protocol.     

认知中继网络中认知用户基于频谱感知机会中继的中断性能分析

认知无线电中继网络中,认知用户需要成功感知到其所在簇内的主用户频谱空穴后才能成为认知中继节点,且各认知中继节点发射功率受到各自主用户干扰温度限制(ITC)。该文对认知中继节点采用分布式空时编码和解码转发协议时认知用户的中断性能进行了分析;给出了认知用户在干扰温度限制下中断概率的上下界,得出中断概率的上下界在不同干扰温度限下与认知用户归一化数据速率、中继数量和其对主用户检测概率的关系。给出了源节点和频谱感知中继节点在相同干扰温度限下的数值仿真,并对仿真结果进行了分析。     

A Cooperative Transmission Scheme for the Secure Wireless Multicasting

In this paper, a wireless multicast scenario with secrecy constraints is considered, where the source wishes to send a common message to two intended destinations in the presence of a passive eavesdropper. One destination is equipped with multiple antennas, and all of the other three nodes are equipped with a single antenna. Different to the conventional direct transmission, we propose a cooperative transmission scheme based on the cooperation between the two destinations. The basic idea is to divide the multicast scenario into two cooperative unicast transmissions at two phases and the two destinations help each other to jam the eavesdropper in turns. Such a cooperative transmission does not require the knowledge of the eavesdropper’s channel state information. Both analytic and numerical results demonstrate that the proposed cooperative scheme can achieve zero-approaching outage probability.     

分布式环境中协作分集的移动中继动态选择和切换策略研究

在协作无线通信系统中,中继节点的移动会大大降低系统的性能,目前该方面的结果很少。本文探讨分布式环境中协作分集的移动中继选择算法,在放大转发（AF）协作通信模式下,给出了基于信道统计状态信息的功率分配和中继的动态选择策略。针对单中继情况提出了中继切换方案,针对多中继情况提出了动态剔除、补充中继的方案,并导出了分集增益及系统容量的计算公式。通过模拟仿真分析,该方案能有效的降低中断概率,提高系统分集增益,扩大系统容量,实现良好的整体性能。      

Security versus reliability analysis for multi-eavesdropper cooperation wireless networks with best relay

Physical-layer security could be used to effectively combat eavesdroppers and the transmission reliability of the main link could be improved.A wireless relay network with multiple both decode and forward eavesdroppers and relays were considered,in the presence of the link from source to destination.A best relay selection scheme based on multieavesdropper’s cooperation was proposed,and the outage probability and the intercept probability was deduced under both schemes without relay and with best relay.Then,the security and reliability influenced by different relay selection schemes were analyzed.The simulation results show that the achievable channel capacity at the destination node and the system outage probability are directly affected by different relay selection scheme.Lower system outage probability can be achieved by the proposed scheme,and the system outage probability and intercept probability are both decreased with the increase of the number of relays.The intercept probability increases with the increase of the number of eavesdroppers,which,however,can be reduced by increasing the number of relays to ensure the main link’s reliable transmission.     

A Hybrid Adaptive Relay Technique for Cooperative Communication System

Cooperative communication will increase the channel capacity, when the communicating terminals exceed more than two. Therefore, a relay is termed, as three-terminal unit is a fundamental for user cooperation. The cooperation provides throughput enhancement, reliability, and coverage improvement for wireless communication. Relay technique plays a vital role in cooperative communication in terms of increasing coverage range as well as spectral efficiency. In existing techniques Amplify Forward increase the noise and Decode Forward increase the computational cost of the receiver. In order to overcome the above limitation, a hybrid adaptive relay technique is proposed for cooperative communication system, which will initially check the channel quality of the end user received SNR. When the receiver does not able to decode the message, then the user will choose relay signal. We derived a closed form expression to find the outage probability and channel capacity for the Rayleigh fading channel. Finally, simulation results show the performance of proposed adaptive relay technique in comparison with traditional relay technique by considering both perfect and imperfect CSI.