基于中断概率的协作通信中继选择与功率分配算法

研究了功率受限情况下多中继协作通信网络的中继选择和功率优化问题。在AF网络中,提出了一种低复杂度中继选择与功率分配算法,其目标是在总功率一定的条件下使系统的中断概率最小。本算法对源节点和所有潜在中继节点进行功率分配,结合当前信噪比选择最优的中继集合,通过最速下降法求出使系统中断概率最低的功率分配因子。该算法不需要知道大量瞬时信道信息、不需要系统在等功率条件下进行中继选择,只需求得中继节点排列矩阵便可根据当前信噪比自适应获得最优中继节点集合。仿真结果表明,在相同条件下,该算法明显优于不同中继节点集合下几种算法的中断性能,并且与传统的SAF及AAF算法相比,有效降低了中断概率,提升了系统性能和功率效率。     

中继蜂窝网中基于负载均衡的中继节点选择算法

提出了一种中继蜂窝网络的基于负载均衡的中继节点选择策略(Load Balancing Relay Selection,LB-Rs).根据每个用户的具体信道状况以及中继节点服务的用户数目,LB-RS以分布式的方式为每个用户选择最优的中继节点.仿真结果表明,与基于单一物理层参数的中继节点选择算法相比,所提出的中继选择算法综...     

一种交互式中继选择策略

提出了一种协作中继网络的交互式中继节点选择(IRS)策略。用户首先分布式构造基于信道状况及中继节点负载情况的中继选择函数,选择最优的中继节点;中继节点再根据资源分配情况、业务优先级以及加权信道调度算法进行反向用户选择。仿真结果表明,相比于已研究的算法,所提出的IRS算法结合了信道状况、MAC层资源与用户业务状况等因素,利用用户和中继之间的两步式交互中继选择来调节小区内的用户负载分布,获得了小区吞吐量与用户公平性之间的折衷。     

一种5G网络协同通信自适应中继选择方案

针对协作通信网的中继选择问题,提出了一种基于贝叶斯推理的自适应中继选择方案。该方案拓展地运用了放大转发协议的原理,准确地分析了中继节点后验概率,并以此选取最优的中继节点进行信息传输。实验仿真结果表明,该方案在信噪比恒定的情况下,显著地提高了网络性能。     

非正交多址接入系统中的联合中继选择和用户配对算法

针对多用户NOMA中继系统,文中提出了一种联合中继选择和用户配对算法。该算法首先利用最小距离准则选择最优次级用户与主用户配对,然后进行最优中继选择来改善系统中断性能。根据系统模型的分析,推导了系统中断概率的准确表达式,并分析了高信噪比条件下的渐近中断性能。系统分集阶数的研究说明了所提NOMA中继系统相比于传统单中继NOMA系统的优越性。最后,蒙特卡洛仿真结果验证了理论分析的正确性。     

能量高效利用的动态节点选择传感网路由算法

无线传感网中由于节点具有有限的能量,因此需最大化它们的网络生存期。在网络生存期问题中,所有节点都在发送广播信息,同时请求中继节点集。选择包含一个主节点的动态中继集是一种特殊情况,在一般性设置中它提供了最优生存期的下界。文中提供了一个基于动态主节点选择算法的初步分析,该分析比较了转播和直接路由。通过仿真结果表明,初始电池不均匀分布及几何设置时,最优主节点选择算法优于直接传输算法;均匀分布情况下,直接传输算法优于最优主节点选择算法。     

基于信道统计特性的中继选择算法

该文提出了一种在非再生协作网络中,基于信道统计特性的最优中继选择方法。首先在等功率条件下,根据信道统计特性,定义一个等效信道增益的参数,该参数反映了中继节点在协作过程中两个阶段的信道特性。然后提出一种基于该参数的降序排列的中继选择方法。该方法在不同的信噪比范围内,选择不同的节点集合,使得系统的吞吐率中断概率最小。分析表明该选择方法的分集增益阶数能达到N+1,N为中继节点数目。仿真结果表明这种中继选择算法的中断概率性能优于其他算法。该方法进一步与功率分配相结合,构成了一种低复杂度的次优的中继选择方法。仿真结果表明这种次优算法能够取得和穷举算法相似的性能。     

采用最优放大因子的全双工中继选择方案

在多中继协作通信系统中,提出一种基于放大转发协议的全双工中继选择算法并进行了相应的理论分析。由于全双工中继中自干扰的存在,为保证通信的质量,首先利用传统的最大化边界信干噪比算法选择一个中继,然后利用中继的最优功率放大因子来减小自干扰对系统的不利影响。基于最优放大因子的全双工中继选择方案在系统中断概率、中继节点功率消耗、目的节点接收信干噪比方面都优于采用最大化边界信干噪比的系统。最后,我们利用蒙特卡洛仿真结果证明了该选择算法的优势。      

多中继与多用户选择的中继系统安全性能分析

为了考察使用多中继选择与多用户选择的放大转发（AF）中继系统的物理层安全性能,推导了其在瑞利衰落信道上和联合发送天线选择/接收最大比合并天线分集下的非零安全容量概率和安全中断概率的精确表达式以及在高信噪比下的渐近安全中断概率解析表达式。AF中继系统的非零安全容量概率和安全中断概率的数值计算和仿真结果相吻合,验证了以上理论分析的正确性;分析结果表明,其安全分集增益为源节点发射天线数、最优中继节点接收天线数、中继节点数的三者乘积与最优中继节点发射天线数、最优用户接收天线数、用户数三者乘积之间的最小值,且与窃听信道无关。     

无线传感网中基于卡尔曼预测的自适应压缩感知

针对无线传感网中节点间相关性较弱但节点内相关性较强的情况,本文提出了基于卡尔曼预测的自适应压缩感知算法。在中继传输模型下,通过卡尔曼预测来决定观测节点是否发送数据,减少发送节点来构建空间稀疏性,同时在融合中心采用自适应选择中继数量的序贯重构算法,降低中继节点的传输能耗。仿真结果表明,和其他基于预测的压缩感知算法相比,本算法观测节点的计算复杂度和中继节点的传输能耗大大降低而不会带来误差的增加。      

Secrecy outage analysis in a hybrid cognitive relay network with energy harvesting

In this paper, we investigate the physical layer security of a hybrid cognitive relay network using an energy harvesting relay in presence of an eavesdropper. In the hybrid scheme, a secondary user (SU) as well as a cognitive relay works either in underlay or in overlay mode. In underlay, the transmit power of the SU as well as the relay is limited by the maximum acceptable interference at primary user (PU) receiver as required by an outage constraint of PU, a quality of service for PU. The secondary network consists of a decode and forward relay that harvests energy from radio frequency signal of secondary transmitter as well as PU transmitter to assist the SU in forwarding the information signal to the destination. A time switching relaying protocol is used at the relay. We evaluate the secrecy outage probability of secondary relay network assuming that channel state information of the interfering links from both the SU and relay transmitter to PU receiver is imperfect. Our results reveal the impact of imperfect channel state information, energy harvesting time, tolerable interference threshold, and PU outage constraint on the secrecy outage probability of SU.     

Research on the NOMA performance in cognitive cooperation network

The non-orthogonal multiple access (NOMA) technology was studied in a downlink cognitive relay cooperation network.A cognitive multiuser relay cooperation based NOMA scheme was proposed (CM-RC-NOMA),in which,the outage performance of PU and SU were given under different cognitive relay cooperation schemes and the corresponding outage expressions were also derived.At the same time,the AF based relay cooperation method and the DF based relay cooperation method were compared.The simulation results show that the lower outage of PU can be achieved by AF method compared with DF method,when the channel condition of BS to PU is no more than that of SU to PU.It is also revealed that the optimal outage performance of PU can be achieved by the proposed best cognitive relay cooperation scheme in contrast to the traditional best cognitive relay cooperation scheme.     

Optimal precoder design for non‐regenerative multiple‐input multiple‐output cognitive relay systems with perfect and imperfect channel state information

This paper studies optimal precoder design for non‐regenerative multiple‐input multiple‐output (MIMO) cognitive relay systems, where the secondary user (SU) and relay station (RS) share the same spectrum with the primary user (PU). We aim to maximize the system capacity subject to the transmit power constraints at the SU transmitter (SU‐Tx) and RS, and the interference power constraint at the PU. We jointly optimize precoders for the SU‐Tx and RS with perfect and imperfect channel state information (CSI) between the SU‐Tx/RS and PU, where our design approach is based on the alternate optimization method. With perfect CSI, we derive the optimal structures of the RS and SU‐Tx precoding matrices and develop the gradient projection algorithm to find numerical solution of the RS precoder. Under imperfect CSI, we derive equivalent conditions for the interference power constraints and convert the robust SU‐Tx precoder optimization into the form of semi‐definite programming. For the robust RS precoder optimization, we relax the interference power constraint related with the RS precoder to be convex by using an upper bound and apply the gradient projection algorithm to deal with it. Simulation results demonstrate the effectiveness of the proposed schemes. Copyright © 2013 John Wiley & Sons, Ltd.     

Combined spatial-temporal energy harvesting and relay selection for cognitive wireless powered networks

In order to improve the Energy Efficiency (EE) and spectrum utilization of Cognitive Wireless Powered Networks (CWPNs), a combined spatial-temporal Energy Harvesting (EH) and relay selection scheme is proposed. In the proposed scheme, for protecting the Primary User (PU), a two-layer guard zone is set outside the PU based on the outage probability threshold of the PU. Moreover, to increase the energy of the CWPNs, the EH zone in the two-layer guard zone allows the Secondary Users (SUs) to spatially harvest energy from the Radio Frequency (RF) signals of temporally active PUs. To improve the utilization of the PU spectrum, the guard zone outside the EH zone allows for the constrained power transmission of SUs. Moreover, the relay selection transmission is designed in the transmission zone of the SU to improve the EE of the CWPNs. In addition to the EE of the CWPNs, the outage probabilities of the SU and PU are derived. The results reveal that the setting of a two-layer guard zone can effectively reduce the outage probability of the PU and improve the EE of CWPNs. Furthermore, the relay selection transmission decreases the outage probabilities of the SUs.     

Two-way中继系统的中继选择算法分析

为了提升双向AF中继系统总速率和降低系统中断概率,提出了一种最小中断概率的中继算法MOP,介绍了现有的两种中继选择算法,利用通信系统的性能指标(信噪比、中断概率、信道容量)展开分析。仿真结果表明,所提出最小中断概率中继选择算法可明显降低系统中断概率,在提升系统总速率的性能与最大化容量中继算法接近,有效地改善了系统性能。     

D2D通信中基于社交门限的最优中继选择方案

在基于设备直传(D2D)通信的中继系统中,提出了一种基于社交感知的增强型中继选择策略.该策略首先在D2D中继网络中引入社交门限值,对潜在中继用户进行筛选和过滤,从而有效降低了探测成本;然后利用最优停止理论实现了最优中继节点的选择.仿真结果表明,与已有中继选择策略相比,所提出的策略能够以较少的中继探测次数获得较高的系统性能收益,从而实现能耗与收益之间的折中.     

Performance of cognitive relay network with energy harvesting relay under imperfect CSI

This paper evaluates the performance of an underlay cognitive relay network under imperfect channel state information (CSI) where a secondary user (SU) transmits using a secondary relay (SR) based on decode and forward scheme. The outage probability (OP) of SU is investigated in a scenario where the decode and forward relay harvests energy from radio frequency signal of SU. The relay uses a fraction of time for harvesting in time switching–based relaying (TSR) while a fraction of received power is used for harvesting in power splitting–based relaying (PSR) scheme. The SU and relay control their transmit power using a scaling factor, based on CSI of the interfering links (ie, links from SU transmitter and SR to the primary user [PU] receiver) to protect the quality of service of PU. The available CSI at the SU and SR are imperfect due to practical limitation. Analytical expressions of the OP are derived for TSR‐ and PSR‐based schemes. The impact of harvesting time, power splitting ratio, imperfect CSI, PU outage constraint and interference threshold on the OP of the SU network, and average transmit power of SR is indicated. Further, the impact of multiple SRs is also shown.     

Maximum harvested energy policy in full‐duplex relaying networks with SWIPT

It is considered that energy scavenging is a promising way for source node transfer energy to powered constraint relay in cooperative networks with advantage of cost‐effective maintenance and flexible deployment, which so‐called simultaneous wireless information and power transfer. In this paper, relay selection for optimal wireless energy is investigated. In terms of time switching–based relaying, this paper considers the performance comparison of 3 proposed relay selection schemes, namely, (1) optimal relay selection scheme , (2) maximum harvested energy relay selection scheme , and (3) minimum self‐interference relay selection . In particular, the system performance is studied intensively with regard to outage probability and throughput over Rayleigh fading channels. We also achieve the integral form for accurate expressions and closed form for approximate expressions. Finally, these analytical expressions are proved exactness according to Monte Carlo simulation.     

双向协作系统的中继选择和功率分配策略

针对瑞利衰落信道下双向多中继协作通信系统,为了降低中断概率,提出了一种基于最小化中断概率的中继选择策略和功率分配方案。首先联合考虑两条链路的中继节点处信噪比和信道增益实现双链路中继选择,然后推导出一种新的最优中继下双向放大转发协作中断概率的近似表达式上界,并利用凸优化求解得到使中断概率最小的最优功率分配解。仿真结果表明,与现有策略相比,提出的策略能够明显降低系统中断概率和误码率,显著提高系统性能。