Joint power allocation and multi-relay selection scheme based on system outage probability

An amplify-and-forward （AF） based multi-relay network is studied. In order to minimize the system outage probability with a required transmission rate, a joint power allocation （PA） and multi-relay selection scheme is proposed under both total and individual power constraints （TIPC）. In the proposed scheme, the idea of ordering is adopted to avoid exhaustive search without losing much system performance. Besides the channel quantity, the ordering algorithm proposed in this article also takes relays＇ maximal output ability into consideration, which is usually ignored in traditional relay ordering algorithms. In addition, simple power reallocation method is provided to avoid repetitive PA operation during the process of searching all possible relay subsets. By Adopting the idea of ordering and using the proposed power reallocation method lead to remarkable decrease of the computation complexity, making the scheme easier and more feasible to implement in practical communication scenarios. Simulations show that the proposed multi-relay selection scheme provides similar performance compared to the optimal scheme with optimal PA and exhaustive search （OPAES） but with much lower complexity.     

Energy-efficient relay selection and optimal relay location in cooperative cellular networks with asymmetric traffic

Energy-efficient communication is an important requirement for mobile relay networks due to the limited battery power of user terminals. This paper considers energy-efficient relaying schemes through selection of mobile relays in cooperative cellular systems with asymmetric traffic. The total energy consumption per information bit of the battery-powered terminals, i. e. , the mobile station(MS)and the relay, is derived in theory. In the joint uplink and downlink relay selection(JUDRS)scheme we proposed, the relay which minimizes the total energy consumption is selected. Additionally, the energy-efficient cooperation regions are investigated, and the optimal relay location is found for cooperative cellular systems with asymmetric traffic. The results reveal that the MS-relay and the relay-base station(BS)channels have different influence over relay selection decisions for optimal energy-efficiency. Information theoretic analysis of the diversity-multiplexing tradeoff(DMT)demonstrates that the proposed scheme achieves full spatial diversity in the quantity of cooperating terminals in this network. Finally, numerical results further confirm a significant energy efficiency gain of the proposed algorithm comparing to the previous best worse channel selection and best harmonic mean selection algorithms.     

基于过时信道状态信息的机会协作性能研究

机会中继是协作通信系统中提高频谱效率和节省功率消耗的常用方法.在通信过程中,信道估计时刻和实际中继传输信息时刻存在一定的延时,其产生的过时信道状态信息（Outdated CSI）会严重地影响协作通信系统的性能.分别从考虑直传链路和不考虑直传链路两方面,分析了过时信道状态信息对机会协作分集系统中断概率的影响.仿真结果表明,系统性能随着相关系数ρ的减小而变差,并且随着中继节点数目的增加而提高.     

Optimal power allocation with AF and SDF strategies in dual-hop cooperative MIMO networks

Dual-hop cooperative Multiple-Input Multiple-Output (MIMO) network with multi-relay cooperative communication is introduced. Power allocation problem with Amplify-and-Forward (AF) and Selective Decode-and-Forward (SDF) strategies in multi-node scenario are formulated and solved respectively. Optimal power allocation schemes that maximize system capacity with AF strategy are presented. In addition, optimal power allocation methods that minimize asymptotic Symbol Error Rate (SER) with SDF cooperative protocol in multi-node scenario are also proposed. Furthermore, performance comparisons are provided in terms of system capacity and approximate SER. Numerical and simulation results confirm our theoretical analysis. It is revealed that, maximum system capacity could be obtained when powers are allocated optimally with AF protocol, while minimization of system’s SER could also be achieved with optimum power allocation in SDF strategy. In multi-node scenario, those optimal power allocation algorithms are superior to conventional equal power allocation schemes.     

基于阴影衰落相关性的协作伙伴的选择

考虑蜂窝移动通信系统中大尺度衰落对协作分集技术的影响,提出根据大尺度衰落相关性来选择协作伙伴。以距离和终端所处的地理环境为依据,建立了蜂窝移动通信系统中阴影衰落的相关模型,求出各终端间的相关系数,选择相关系数最小的作为协作伙伴。从理论上对由此形成的协作通信系统进行了分析,可以提高信道容量,降低误码率。仿真结果进一步验证了该方法的可行性。     

分布式无线通信系统中的主从协同功控

分布式无线通信系统通过多个基站与移动台协作通信有效地提高了系统的容量和覆盖范围。然而传统的功率控制算法并不适用于移动台同时接收多个基站信号的情况。本文提出了一种基于适用多小区结构的主从协同功控算法。该算法把为移动台服务的基站分为主基站和从基站,各从基站以主基站分配的功率为参考值分配功率,可使整个覆盖区域内的所有移动台达到平衡的信干比,且可适用于任意拓扑结构的,使用全向天线或定向天线的分布式无线通信系统,并可以采用低复杂度和开销的分布式算法实现。仿真结果表明,在不同环境中,与现有的分布式系统中功控算法相比,新算法可以显著地提高整个系统的容量。     

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.     

Lifetime maximization of cooperative networks with mean channel gain information

ith the ETP.     

Asymptotically optimal cooperative wireless networks with reduced signaling complexity

This paper considers an orthogonal amplify-and-forward (OAF) protocol for cooperative relay communication over Rayleigh-fading channels in which the intermediate relays are permitted to linearly transform the received signal and where the source and relays transmit for equal time durations. The diversity-multiplexing gain (D-MG) tradeoff of the equivalent space-time channel associated to this protocol is determined and a cyclic-division-algebra-based D-MG optimal code constructed. The transmission or signaling alphabet of this code is the union of the QAM constellation and a rotated version of QAM. The size of this signaling alphabet is small in comparison with prior D-MG optimal constructions in the literature and is independent of the number of participating nodes in the network     

QoS-guaranteed multi-relay selection and power allocation optimization in cooperative systems

This paper investigates the relay selection and power allocation problem in multi-user based cooperative networks, where intermediate relay nodes help source forward information to destination using decode-and-forward (DF) relaying protocol. Specifically, we propose a novel multi-relay nodes selection strategy taking both instantaneous channel state information (I-CSI) and residual energy into consideration, by which 'emergence' diversity gain can be achieved and the imbalance of resource utilization can be overcome. Besides, using Largangian dual-primal decomposition and subgradient projection approach, an optimal power allocation algorithm at source and cooperative relay nodes is presented with the constraints of each user's individual quality of service (QoS) requirements and system total transmit power. Theoretical analysis and simulation results demonstrate that the proposed scheme can significantly improve energy efficiency, while guaranteeing a good balance between achievable data rate and average network lifetime with relatively low implementation complexity.     

Joint power and spectrum allocation in multi-hop cognitive radio networks

Various cognitive network technologies are developed rapidly. In the article, the power and spectrum allocation in multi-hop cognitive radio network （CRN） with linear topology is investigated. The overall goal is to minimize outage probability and promote spectrum utility, including total reward and fairness, while meeting the limits of total transmit power and interference threshold to primary user simultaneously. The problem is solved with convex optimization and artificial bee colony （ABC） algorithm jointly. Simulation shows that the proposed scheme not only minimizes outage probability, but also realizes a better use of spectrum.     

协作分集中基于延迟时间的伙伴选择

在协作分集中如何及时有效选取合作伙伴是重点研究问题之一,制定一个合理可靠的选择标准是解决此问题的关键。依据传输路径的时延特性,提出以中继延迟时间最小为标准来进行协作伙伴的选择。对此选择标准在分集增益、信噪比、传输误比特率性能上进行了仿真分析,表明以此标准选择协作伙伴能够获得较好的分集性能,降低误码率,并且能够避免目的节点处因同时接收中继节点信息而造成干扰阻塞,是一种可靠的伙伴选择协议。     

Grouping and partner selection in cooperative wireless networks

Various results to date have demonstrated the advantages of one or several relay nodes assisting transmissions in a wireless network. In many practical scenarios, not all nodes in the network are simultaneously involved in every transmission; therefore, protocols are needed to form groups or subsets of nodes for the purposes of cooperation. We consider this problem in the context of regenerative nodes and non-altruistic cooperation (all nodes have data of their own to transmit). For a network-wide diversity advantage, the protocol must provide each transmitting node with enough "partners" that can decode its message with high-enough probability. Assuming that the nodes cannot communicate their control decisions (distributed scenario), and that each node chooses to help n other nodes, we point out a simple, static selection strategy that guarantees diversity n+1 for all transmissions. We then consider centralized control strategies and study the additional gains that arise from a central control, under various amounts of information being available to the central controller     

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。     

一种用于无线传感器网的协作接收方案

无线传感器网中,能量效率是系统设计首要考虑的因素.基于提高无线传感器网能量效率的目的,本文提出了一种简单的协作接收方案并分析了其能量效率,理论分析及仿真结果表明,当通信距离大于某一门限值时采用该接收方案可以有效提高无线传感器网的能量效率.     

Multiplicative multi-attribute auction based optimal network selection for heterogeneous wireless networks

One of the remarkable features of the next generation network is the integration of heterogeneous wireless networks,which enables mobile users with multi-mode terminals access to the best available network seamlessly.However,most of previous work only takes account of either maximizing single user’s utility or the whole network’s payoff,rarely considers the negotiation between them.In this paper,we propose a novel network selection approach using improved multiplicative multi-attribute auction(MMA).At first,an improved MMA method is put forward to define the user’s utility.Additionally,user cost is defined by considering allocated bandwidth,network load intensity and cost factor parameter.And last the best suitable network is selected according to the user’s performance-cost-ration.Simulation results confirm that the proposed scheme outperforms the existing scheme in terms of network selection’s fairness,user’s performance-cost-ration,load balancing and the number of accommodated users.     

对协作系统自适应角色选择策略的思考

在传统协作系统基础上提出了一种新颖的自适应协作方式——机会角色选择协作.为进一步说明该策略,构建了一种最基本的两用户机会协作框架,其中两个用户相互竞争将各自信息发送给同一目的端.根据瞬时信道条件,两用户均可以机会地充当信息源角色,而另一用户将作为放大转发中继来为信源服务.同时,在此基础上提出并简要描述了一种最优的中心化角色选择策略(C-ROSE).该策略能够最大化目的端接收信噪比(SNR),进而提高系统传输性能.研究表明,通过这种动态、灵活、高效的节点角色分配方式,协作系统的传输可靠性可得到进一步增强,从而为构建稳固、高效、互惠的协作传输体系开辟了新道路.     

Cooperation with multiple relays in wireless sensor networks: optimal cooperator selection and power assignment

We consider the energy-minimal joint cooperator set selection and power assignment problem in a cooperation scenario with multiple relays, under transmit power constraints, while satisfying a target frame error rate (FER) at the destination receiver. We first derive the FER of a cooperative system and present a simplified calculation that also involves a simple, yet close approximation to the average bit error rate of a multiple input single output system. Our FER calculation facilitates a closed-form solution for the joint optimization problem, resulting in the Optimal Cooperator Selection and Power Assignment (O-CSPA) algorithm. Next, we devise the Distributed Cooperator Selection and Power Assignment (D-CSPA) algorithm in which the relays individually decide to become a cooperator and determine their power levels. We evaluate the performance of O-CSPA and D-CSPA algorithms under several network topologies, varying target FER levels and different power consumption models, by considering the energy dissipated in the transceiver circuits and amplifiers of all involved nodes. We show that both algorithms provide notable energy savings and conclude that the extent of the savings depends significantly on the power consumption model. D-CSPA’s performance is shown to be not only close to that of optimal solution, but also robust to errors in channel estimation.     

Enhanced cooperative MAC for wireless local area networks

A novel network protocol,enhanced cooperative medium access control(ECoop MAC),is present in this article.Its function is to guarantee the quality of service(QoS)in wireless local area networks.For the sake of supporting different application scenarios,two proposed schemes,namely E-scheme I for lower priority traffic and E-scheme II for higher priority traffic can be adopted independently or in combination.ECoop MAC takes into account request failure problems,and utilizes cooperative protocol information to boost the system performance as well as to effectively cut control packets overhead.Simulation results show that the proposed algorithm can not only improve network throughput,but also lead to reduced network delays for individual packets.     

含光伏发电系统的配电网无功补偿优化规划

本文针对目前含分布式电源的配电网无功补偿问题,采用改进禁忌搜索算法,通过IEEE33节点网络拓扑进行分析,使含分布式电源的配电网无功功率补偿达到全局最优,降低网络损耗.