直达链路下的全双工能量采集中继系统的吞吐量分析

针对三节点传输系统,研究了基于时间切换能量采集的全双工放大转发协作中继方案。考虑源和目的地之间存在直达链路,全双工中继节点采用天线选择技术以最小化中继自干扰,目的节点采用最大比合并技术以最大化目的地接收信噪比。在延迟受限传输模式下,推出了自干扰信道增益为常数时系统吞吐量近似闭合表达式。运用最佳目的地选择策略和自适应中继选择策略讨论了系统吞吐量性能。如图4所示,在源发送功率为30 dB时,就系统吞吐量而言,本文算法比其他两种算法分别提高了0.22 bits/s/Hz和0.68 bits/s/Hz。数值分析和蒙特卡洛仿真表明,增加中继个数,增加目的地个数或者增大能量采集效率均能够提升系统吞吐量性能。      

协作干扰下的非可信中继与全双工目的节点系统的遍历安全容量分析

研究了一种非可信放大转发中继与全双工目的节点相结合的传输模型。为提升系统安全性能,提出了全双工目的节点干扰(full duplex-destination based jamming,FD-DBJ)策略。同时结合半双工目的节点干扰策略以及放大转发中继策略对比分析系统安全性能。在瑞利衰落信道下,通过合理的近似分析推导出三种策略遍历安全容量的近似闭合表达式。分析与仿真结果显示,在高信噪比下,理论分析曲线与蒙特卡洛仿真结果基本吻合,并对三种策略的性能进行对比,凸显出FD-DBJ策略的性能优越性。并分析了FD-DBJ传输策略的最优功率分配因子。      

基于能量采集的全双工中继系统时隙优化

针对能量采集基础上的全双工中继系统时隙优化问题,以双跳能量采集全双工中继系统为模型,基于中继工作于时间分割模式,分析了在放大中继转发协议与译码中继转发协议下如何实现系统吞吐量最大化,对能量采集时隙进行了优化研究,推导了瑞利衰落信道下最佳能量采集时间的具体表达式,在仿真中对比了全双工中继系统与半双工中继系统的吞吐量。通过性能分析与仿真实现可知,全双工中继技术可以提高频谱利用效率、系统吞吐量,满足日益增长的高速率要求。     

基于协作干扰的全双工中继系统混合安全传输协议

针对全双工中继系统的安全问题,提出一种基于协作干扰的物理层安全混合传输协议.系统根据自身信道状态信息,自适应地选择基于中继节点与信源节点轮流发送干扰(RSCJ)协议或基于中继节点与目的节点轮流发送干扰(RDCJ)协议中安全容量相对较高的协议进行信息的传输.在全双工节点自干扰因素被抑制的条件下,给出了系统的传输协议选择策略,并理论推导了采用RSCJ或RDCJ传输协议下系统的安全中断概率表达式.仿真结果表明,利用所提的混合安全传输协议可以显著提高全双工中继系统的安全中断性能,与传统未利用协作干扰的传输机制相比,具有明显的安全性能优势.     

功率约束下的星地协作网络中断概率分析

针对星地协作网络,考虑中继节点转发卫星节点信号时会受发射功率和干扰功率约束,提出了一种基于中继节点与目的节点间链路最大信噪比准则来选择中继节点的放大转发部分中继选择策略。在卫星链路遭受阴影莱斯衰落和地面链路遭受瑞利衰落情况下,推导出系统中断概率下界的闭合表达式。仿真结果表明了理论分析的正确性,并展示了不同阴影莱斯信道参数、不同中继数目、不同功率约束对中断概率的影响。     

同信道干扰下的中继网络性能分析

分析了两跳中继网络在同信道干扰下的中断概率。在中继网络中,源节点广播信号至所有的中继节点,此时同信道干扰在中继节点或者目的节点处被引入。中继节点采用解码转发策略转发源节点的信号,而目的节点采用最大比合并技术接收来自中继节点的信号。最终推导了各种干扰情形下系统中断概率的闭合表达式。仿真结果表明,解析曲线和蒙特卡洛仿真曲线非常吻合,而同信道干扰在某些场合会对系统性能造成较大影响。分析结果对中继网络的系统设计和参数设置都有一定的参考意义。     

多跳协同中继网络下物理层安全传输方案

针对多跳中继传输系统的信息安全传输问题,提出了一种基于全双工模式下多节点协作干扰(FD-MCJ)的物理层安全传输方案。该方案利用通信网络中的中继节点发送干扰信号恶化窃听节点的接收性能,同时中继节点根据信道状态信息(Channel State Information, CSI)自适应的选择两种情况下的安全传输方案。本文首先利用泊松点过程对窃听节点位置进行安全建模;然后,根据CSI可用程度,给出不同的安全传输具体方案,在考虑系统的跳数、天线间自干扰以及发射功率和干扰功率等因素下,推导FD-MCJ方案下系统保密中断概率的闭式解;最后,数值分析和蒙特卡洛仿真表明,理论推导的正确性以及多跳中继系统中采用全双工多节点协作干扰方案能够有效提升系统安全性能。      

过时信道状态信息下的机会式中继选择系统的安全性能分析

在 Nakagami m衰落信道下,目的端和窃听者采用最大比合并策略,本文研究了在机会式自适应解码转发中继选择安全协作系统中的安全性能。由于实际信道中的反馈延迟,最优的合法中继选择基于合法信道反馈的过时信道状态信息。为了评价机会式中继选择在改善安全性能上的表现,分别推导了准确的正安全容量概率和准确的安全中断概率闭合表达式。此外,针对两种不同情况, 推导了形式简单的渐近表达式,并明确给出安全分集阶数和安全阵列增益。理论分析和数值仿真表明,增加中继个数和目的节点的天线数能够改善安全中断概率的性能表现,且在信道状态信息过时的条件下,系统的安全分集阶数与中继数无关。      

能量收集全双工中继网络中的中继策略研究

本文针对双跳全双工多中继系统,研究了在中继节点能量受限情况下的中继选择方案。在该文中,中继工作方式为放大转发（Amplify-and-Forward, AF）,且中继通过收集源节点提供的能量来对源节点信息进行转发。整个通信过程分为两阶段,能量收集阶段与信息传输阶段,即采用的是时域分割方案。为了获得较好的性能与复杂度折中,本文分别研究了三种不同的中继选择策略,即最佳中继选择方案和两种次优中继选择方案。针对所提的三种方案,推导分析了其系统中断概率的理论值和下边界,以及系统的有效吞吐量。最后,利用蒙特卡洛仿真验证了理论分析的正确性,且仿真结果表明最佳中继选择方案的性能优于两种次优的中继选择方案,但其实现的复杂度高。      

全双工认知NOMA网络下中继选择策略性能分析

本文把非正交多址接入(NOMA)技术与认知网络相结合,提出了一种基于多中继选择的认知NOMA网络模型。考虑了在瑞利衰落信道下,主网络借助次级网络中的全双工中继实现可靠通信,作为回报,次级网络允许接入授权频谱来传输次级信号。中继同时接收主次信号后,采用串行干扰消除技术(SIC)依次解码主次信号,并根据NOMA协议转发信号到主次用户端。推导了在两种中继选择策略下认知NOMA网络中断概率,并通过了蒙特卡罗仿真验证。仿真结果表明,两阶段中继选择策略和全双工技术能有效提高系统中断性能。      

Hierarchical modulation-based cooperation utilizing relay-assistant full-duplex diversity

In this paper, we present a hierarchical modulation-based cooperation (HMC) scheme to overcome capacity degradation due to half-duplex transmissions in conventional cooperative relay systems. In the HMC scheme, two relay terminals are used for both transmit and receive operations, i.e., full-duplex transmission. This scheme reduces the required number of time slots for cooperation. Utilizing this cooperative mechanism, the HMC scheme achieves cooperative diversity at the destination node by combining the signals delivered from the source and relay nodes. In addition, we derive a closed form of the end-to-end bit error rate for the HMC scheme, which is utilized to determine an optimal power ratio for hierarchical signals at the source node. In concurrence with the HMC scheme, we develop the best relay selection scheme for a practical wireless communication networks.     

非理想SIC下全双工NOMA系统的安全性能分析

针对存在多个非共谋窃听者,研究了一种基于全双工中继和两阶段中继选择（TSRS）的非正交多址接入（NOMA）物理层安全通信方案。每个通信过程包含一个传输时隙,系统在每个时隙开始由TSRS策略选择最优中继,所选中继在从源节点接收NOMA叠加信号的同时,向两个目的节点转发上一时隙的再编码叠加信号,两个目的节点采用串行干扰消除（SIC）技术从中继叠加信号中解码获取各自的期望信号。推导了非理想SIC下系统安全中断概率的近似表达式,进行了蒙特卡洛（Monte-Carlo）仿真验证,同时分析了各仿真参数（SIC残余干扰系数、目标安全速率、中继规模等）与系统安全中断概率的关系。理论分析与模拟仿真的结果表明,全双工技术与TSRS的结合方案能有效提升系统的安全中断性能。将该方案应用于实际通信系统设计时,选择合适传输信噪比（SNR）、提高串行干扰消除能力或适当增加中继数量均可实现更好的保密性能。      

Impact of residual transmit RF impairments on energy harvesting relay selection systems

In this paper, we study the impact of residual transmit radio-frequency impairments (RTRIs) on a dual-hop energy-harvesting system in which a source and a destination both having multiple antennas communicate to each other with the help of single-antenna amplify-and-forward (AF) relays. The source and destination employ maximum ratio transmission (MRT) and maximal ratio combining (MRC), respectively, to exploit the benefits of using multiple antennas. To simplify the system complexity, we propose two partial relay selection (PRS) schemes (RSSs) that maximise the combined channel gains of the first hop (PRS-1 scheme) and the second hop (PRS-2 scheme), respectively. Both time-switching relaying (TSR) and power-splitting relaying (PSR) protocols are examined. In order to evaluate the system performance, the analytical expressions for outage probability and ergodic capacity are derived, and then the throughput expressions for delay-limited and delay-tolerant transmission modes are formulated. The analytical results are validated by Monte Carlo simulations. Our results show that: (1) The impact of RTRI can be significantly reduced by increasing the number of antennas and relays. (2) The PRS-1 scheme outperforms the PRS-2 scheme. (3) In the delay-limited mode, the TSR protocol performs better than the PSR protocol at high impairment levels, whereas in the delay-tolerant mode, the throughput of the PSR protocol is superior to that of the TSR protocol.     

基于部分中继选择的能量收集双跳网络信息年龄优化

针对传统中继协作网络传感器节点能量受限导致信息传输延迟较高的问题,将短包通信（SPC）和能量收集技术相结合,构建了一种双跳中继无线传感器网络模型。网络中源节点和中继均需从专用能量基站收集射频信号能量以保证信息的持续传输,中继采用半双工解码转发协议将源节点发送的状态更新信息以短包形式传递到目的节点,利用中继选择策略与最大比合并技术提出了基于时效性的最早部分中继选择方案。考虑该网络信息的新鲜度,首先,分析了SPC传输性能,推导了中继和目的节点处的平均包错误率。其次,利用顺序统计量描述了源节点到中继端数据包的重传次数,基于更新过程理论推导了网络的平均信息年龄（AoI）表达式,并采用梯度下降方法优化了影响网络平均AoI的部分参数。最后,仿真分析结果表明,优化中继数量和数据包长度可以有效提高网络信息新鲜度,同时,通过对比优化部分参数得到的最优值与贪婪方法得到的最小化平均AoI理论值,可以验证部分中继协作方案在双跳状态更新网络中的可行性。      

Simultaneous energy harvesting and information processing in wireless multiple relays with multiple antennas

Wireless networks suffer from battery discharging specially in cooperative communications when multiple relays have an important role but they are energy constrained. To overcome this problem, energy harvesting from radio frequency signals is applied to charge the node battery. These intermediate nodes have the ability to harvest energy from the source signal and use the energy harvested to transmit information to the destination. In fact, the node tries to harvest energy and then transmit the data to destination. Division of energy harvesting and data transmission can be done in two algorithms: time-switching-based relaying protocol and power-splitting-based relaying protocol. These two algorithms also can be applied in delay-limited and delay-tolerant transmission systems. The previous works have assumed a single relay for energy harvesting, but in this article, the proposed method is concentrated on improving the outage probability and throughput by using multiple antennas in each relay node instead of using single antenna. According to our simulation results, when using multi-antenna relays, ability of energy harvesting is increased and thus system performance will be improved to great extent. Maximum ratio combining scheme has been used when the destination chooses the best signal of relays and antennas satisfying the required signal-to-noise ratio.     

Comparative Performance Analysis of Multi-Antenna Regenerative Cooperative Relay in Nakagami-m Fading Channel

Performance of cooperative relay schemes employing infrastructure based fixed relays having multiple antennas, has been investigated. Closed form expressions of outage probability, bit error rate and throughput for such system have been derived for Nakagami-m fading channels, with integer values of m. Here, relay and destination may perform either maximum ratio combining or selection combining of the signals. Comparative performance analysis of all four possible combinations has been analyzed for various relay locations, different number of antennas on the relay, various transmission rate and different fading conditions.     

Exact analysis of the multihop multibranch hybrid AF/DF relaying networks

In this paper, the exact analysis of a multihop multibranch (MHMB) relaying network is investigated wherein each relay can operate in amplify‐and‐forward (AF) or decode‐and‐forward (DF) modes depending upon the decoding result of its received signal. If a relay decodes the received signal correctly, it works in DF mode; otherwise, the relay operates in AF mode. Therefore, we name such relaying network as hybrid amplify‐and‐forward and decode‐and‐forward (hybrid AF/DF) relaying network. We first investigate the signal transmission from source to destination node via n number of relays in a hybrid AF/DF MHMB mode. Then, we obtained the statistical features and analyze the end‐to‐end signal‐to‐noise ratio (SNR). Finally, a comprehensive performance analysis is conducted by using maximal ratio combining (MRC) scheme at the destination node. For comparison, we also obtained the results using selection combining (SC) scheme at the destination node. To the best of our knowledge, very few works in the literature have considered a general system model of MHMB relaying network wherein each relay can operate in AF or DF modes, that is, a hybrid AF/DF relaying network. Accordingly, the analysis of our system model is not only novel and exact, but also is comprehensive and can be employed in the future works.     

全双工窃听者主动干扰的协作NOMA网络性能分析

研究了瑞利衰落信道下协作非正交多址系统的安全性能。通信过程由一个时隙构成,源节点向中继广播叠加信号,全双工中继使用串行干扰消除技术解码信号协助用户通信。假设存在潜在全双工主动窃听者,窃听者能够从中继处截获信息并同时向用户发送人工噪声进行干扰。基于上述假设,在高信噪比条件下,推导了安全中断概率的近似表达式,分析了各节点传输信噪比与功率分配因子对系统中断概率的影响,分析结果与蒙特卡洛仿真结果吻合。