异构无线通信系统的融合机制和协同功率分配算法研究

该文提出了一种基于协同通信和无线中继技术的融合机制,以实现异构无线接入网的互联互通和融合。为了最大化所提异构协同网络方案的协同容量,从理论上给出了协同功率分配优化理论模型,并介绍了一种不同于传统注水理论的基于效用函数的协同功率分配算法,该算法在合理设置发射功率保证第1跳和第2跳链路的传输速率匹配的前提下能够优化系统性能。仿真结果表明所提协同功率分配算法有显著的性能增益。     

基于多跳协同传输的物联网系统性能研究

针对物联网系统中多跳协同传输的场景,为满足低功耗和高可靠等系统传输要求,提出了目的节点利用收发端直达链路和多跳中继协同链路的最大比合并实现信号的分集接收的传输方案.其中源节点到目的节点的直达径传输和多跳协同传输信道均服从Nakagami-m分布,该分布可涵盖瑞利分布和莱斯分布等信道特性,增加了理论分析的难度.本文在获得接收端信噪比的概率密度函数闭合表达式的基础上,利用概率密度函数分析法和积分特性等方法,在无任何函数近似的条件下,推导出了基于多跳协同传输的物联网系统中断概率和误码率的闭合表达式.通过数值仿真验证了所提方案的有效性和理论分析的正确性.     

瑞利-对数正态联合衰落下多跳宏分集的性能分析

基于多跳传输的特点,提出了一种多跳宏分集。以3个基站构成的六边形宏分集为模型,分别在纯阴影和联合衰落信道下研究了上行链路最大比合并(MRC)的DPSK误码率。分析表明,新系统的性能要优于传统单跳宏分集系统,多跳中继能增强系统性能随移动终端位置变化的鲁棒性,对改善无线链路的可靠通信较有好处。     

异构网络脏纸编码方案

异构网络技术是一把"双刃剑"。一方面,引入低功率节点能够增加网络部署的灵活性;另一方面,部署低功率节点同样会引入大量潜在干扰源。合理的低功率节点部署方案和高效的无线资源管理是降低干扰,提高异构网络性能的关键。鉴于脏纸编码方案具有能够充分利用发射端信道信息消除干扰的特性,首先考虑异构网络宏微蜂窝干扰受限的场景,指出脏纸编码方案在异构网络Z信道干扰中的应用。其次指出传统的脏纸编码方案在互干扰双链路网络中,只能消除一条链路的干扰,无法使两条链路同时实现无干扰信道容量。因此,一种基于协作分集的脏纸编码方案被提出,使相互干扰的两条收发链路均能达到无干扰时的信道容量。最后,通过仿真对比验证脏纸编码方案在Z干扰信道和二元对称信道中的性能优势。     

AF协同通信系统最优多跳中继位置

协作中继能够提供分集增益以提高链路成功发送分组的概率,除传输功率外,中继位置也是影响端到端性能的一个重要参数。为了降低多个协作节点对系统容量的影响,多跳中继是当前协作中继发展的一种新趋势。通过中断概率,得出了吞吐量的理论近似表达式,并进一步研究多跳中继位置对吞吐量的影响。仿真结果表明,多跳中继处于源节点和目的节点的中点...     

低轨卫星移动通信系统中译码前传协作策略的性能研究

卫星移动通信信道是典型的衰落信道,其信道特性在不同的环境中通常被表述为三种衰落形式,即Rayleigh 衰落、Rician衰落和遮蔽Rician衰落.为了保证可靠的通信,系统需要采用具有较强抗衰落能力的技术来进行信号的传输.近年来,协作分集技术因其能显著地提高无线通信系统的性能而吸引了大量的研究关注.莱曼等人的研究中提出了多种协同策略,包括放大前传,译码前传和编码协同等.本文中提出将协作分集技术应用在低轨卫星移动通信系统用户下行链路(卫星和终端用户之间的通信链路)中以减小信道衰落的影响.建立系统模型,分析得出该系统采用译码前传协作策略的通用误码率公式,由此推导出用户下行链路在Rayleigh衰落信道、Rician衰落信道、遮蔽Rician衰落信道条件下的系统误码率公式.仿真结果表明,理论分析和仿真结果完全吻合,本系统相对于传统无协作系统有较大的性能优势.     

WiMax与3G LTE网络互联与融合技术研究

本文先分析WiMax与3GPP长期演进项目(LTE)两种无线接入技术融合的可能性.基于通用链路层(GLL)和协同无线资源管理(CRRM)机制的引入.提出了两种不同的协作程度的百联融合技术的网络架构.引入GLL的目的是为不同的无线接入机制提供统-的链路层数据处理.同时带来两个新的研究子课题:异构发送分集与异构多跳技术.CRRM完成网络间无线资源的协调管理,以达到最优化无线资源利用率和最大化系统容量的目的.几种关键的协同无线资源管理机制包括:接人选择、负载均衡、动态频谱控制技术在文中进行了详细分析及讨论.     

基于网络编码的系统中断性能分析

在无线通信中,信道的衰落会降低信号传输的可靠性,影响通信质量。协同分集技术作为一种对抗衰落的有效手段,能提高无线通信性能,已经得到了广泛的研究和应用。为了更有效地利用信道资源,本文提出了基于机会式网络编码的协同机制。在两个节点A和B与一个中继节点R相互协同向基站D发送数据的仿真场景下,研究非协同通信机制、传统协同通信机制和机会式网络编码的协同通信机制下的系统中断概率。理论分析和系统仿真表明,当节点A与B之间的链路以及节点A,B到中继R的链路存在衰落的情况下,机会式网络编码的协同策略具有较好的性能。      

基于跨层设计的AODV路由算法研究

为了提高移动Ad Hoc网络中AODV路由算法的性能,提出了一种基于两跳邻居信息的高效AODV路由算法-TNAODV,文中采用两跳邻居信息机制,减少了建立路由所耗的时间;同时通过在网络层、MAC层与物理层三层之间的跨层协同,实现了及时的感知链路的连接状态,减少了因链路断裂而增加的路由开销。性能分析和仿真结果均表明,该路由算法在端到端时延、成功率等性能优于经典的AODV路由算法。     

无线蜂窝网络中一种新的多跳宏分集

基于多跳中继的概念，提出了一种新的多跳宏分集。在瑞利阴影联合衰落信道下以三个基站构成的六边形宏分集为模型，研究和分析了上行链路选择合并(SC)和最大比合并（MRC)时的中断率。分析表明，新系统的性能要优于传统单跳宏分集系统，多跳中继能增强系统性能随移动终端位置变化的顽健性。     

Performance analysis of multi-user diversity in heterogeneous cooperative communication systems

The heterogeneous cooperative relaying technique can be utilized to complete the hierarchical convergence for the multi-radio access networks, where the single heterogeneous cooperative relay is selected and the maximal-ratio combining (MRC) scheme is utilized to achieve the cooperative diversity gain. In order to evaluate performances of the hierarchical convergence mechanism, this paper theoretically investigates the key factors of the multi-user diversity (MUD) gain, the heterogeneous cooperative diversity gain and the large scale fading of the first and second links. The tight closed-form expressions in terms of the outage probability and the average symbol error rate are derived for evaluating how and with what factors impact on the system performance. The analytical and simulation results show that the number of heterogeneous cooperative relay nodes (HCRNs)M and the number of destination stations (DSs)K have great impacts on performances, and the order of outage probability is (M + 1)K. The large scale fading ratio of the first hop to the second hop also has a big impact on performances. Thus in the real network, we can utilize advanced radio resource management schemes to achieve a high multi-user diversity, instead of configuring too many HCRNs for the heterogeneous cooperative diversity gain. Furthermore, we can guarantee the transmission quality between the BS and HCRNs via the network planning to optimize the overall network performance.     

A utility-based capacity optimization framework for achieving cooperative diversity in the hierarchical converged heterogeneous wireless networks

A hierarchical convergence mechanism for the heterogeneous wireless communication system via the heterogeneous cooperative relay node is presented in this paper, in which the techniques of cooperative communication and wireless relay are utilized to improve performances of the individual user and the overall converged networks. In order to evaluate the benefits of the proposal, a utility-based capacity optimization framework for achieving the heterogeneous cooperative diversity gain is proposed. The heterogeneous cooperative capacity, relay selection and power allocation theoretical models are derived individually. The joint optimization model for relay selection and power allocation is presented as well. Owing to the computation complexity, the sub-optimal cooperative relay selection algorithm, the sub-optimal power allocation algorithm and the sub-optimal joint algorithm are determined to approach the maximum overall networks' spectrum efficiency. These proposed algorithms are designed in conformance to guarantee the equivalent transmission rates of the different wireless access networks. The simulation results demonstrate that the utility-based capacity model is available for the heterogeneous cooperative wireless communication system, and the proposed algorithms can improve performances by achieving the cooperative gain and taking full advantage of the cross-layer design. Copyright © 2008 John Wiley & Sons, Ltd.     

协作通信系统的中继选择算法研究

协作通信作为一种新颖的无线通信技术,它的主要思想是通过中继节点参与协作传输,在目的端获得两个或者多个在空间上独立的信号样本,实现空间分集,获得分集增益.因此如何合理选择中继节点成为协作通信的关键问题之一.本文在协作通信模型及原理的基础上,对基于信道状态信息的中继选择算法进行了介绍,并对具体的选择算法的性能进行了仿真.     

Comparative performance analysis of cooperative and multi dual‐hop relay networks using MGF approach

In this paper, we analyzed and compared the performance of cooperative diversity systems such as cooperative and multi dual‐hop networks with non‐regenerative relay nodes. The contributions of this study are twofolds. Firstly, analytical expressions of outage probability P_out and average symbol error rate ASER are derived using moment generating function (MGF) analysis of the received SNR with the assumption that the channel experiences Weibull fading and the best relay selection is used. Then, using the analytical results, comparative performance evaluation of cooperative and multi dual‐hop relay networks is done for varying number of relay nodes and different receive diversity schemes such as maximal ratio combining (MRC) and selection combining (SC). The results show that the cooperative relay network has better performance than a multi dual‐hop relay network in terms of P_out and ASER. The results also show that the multi dual‐hop network can achieve the same performance as the cooperative network with the requirement that it needs the deployment of three times more relay nodes.     

Secrecy performance analysis of AF relaying with relay selection scheme over Nakagami‐m fading channels

This paper investigates the secrecy outage probability (SOP) and intercept behavior for the amplify‐and‐forward network over Nakagami‐m fading channels. Relay selection schemes are evaluated. The optimal and suboptimal criterions require the instantaneous and statistical channel state information of the eavesdroppers' channels, respectively. The enhanced 2‐hop criterion needs the additional information of the target secrecy rate for relay selection. Theoretical analysis reveals that the diversity order of the SOP is dominated by the minimum fading figures of the source‐relay and relay‐destination channels, while that of the intercept probability depends on the fading figure of the relay‐destination channel. In the multirelay scenario, the optimal, suboptimal, and enhanced 2‐hop scheme achieve the same diversity orders of the SOP. For the intercept probability, the optimal and second‐hop relay selection schemes provide the same diversity order, while the diversity orders of the suboptimal and enhanced 2‐hop schemes are the same. Simulation results finally substantiate the accuracy of the theoretical analysis.     

Secure AF relaying with efficient partial relay selection scheme

This paper evaluates the secrecy performance for the amplify‐and‐forward (AF) protocol with partial relay selection (PRS) schemes in the scenario of multiple independent but not necessarily identically distributed eavesdroppers. The secrecy performances of the first‐hop and second‐hop PRS schemes are revisited. Given the secrecy data rate, an efficient PRS scheme is presented, which selects the relay based on the instantaneous channel state information (CSI) of either the first or second hop according to the statistical CSI of two hops. The proposed PRS scheme provides the trade‐off between the two‐hop and one‐hop PRS criteria. Results show that the secrecy outage probability (SOP) performance of the proposed scheme is close to that of the conventional opportunistic relaying in the medium main‐to‐eavesdropper ratio (MER) regions. As for the intercept probability, the second‐hop scheme achieves the highest diversity order among PRS schemes and its performance depends on the overall eavesdroppers' behavior not on individual effects of the specific relay. The proposed criterion also outperforms the first‐hop PRS scheme. Simulation results finally substantiate the accuracy of the theoretical analysis.     

具有天线选择与中继选择的空间调制技术

针对空间调制(SM)技术存在的缺欠,提出了具有天线选择和中继选择的空间调制系统方案。首先在多输入多输出(MIMO)信道模型下,通过对发送端天线选择,将拥有最佳信道状态的天线选出进行SM,打破SM技术对发送端天线数的限制,并提升采用高阶调制的SM分集性能。然后进一步将此思想引入协作通信网络,结合传感器网络的分级观念,提出采用中继选择和空间调制的中继传输协议,并通过仿真观察系统分集性能的改善。仿真结果表明,上述中继传输协议不仅能提升系统性能,而且使系统配置更加灵活。     

A cross-layer protocol for exploiting cooperative diversity in multi-hop wireless ad hoc networks

Cooperative communication has emerged to reap the benefits of spatial diversity. To fully exploit cooperative diversity, we propose a medium access control and routing enabled cross-layer cooperative transmission (MACR-CCT) protocol for improving the performance in multi-hop wireless ad hoc networks (MWAN). Different from previous cooperative protocols that determine a receiver in one hop according to a non-cooperative routing protocol first and then select a cooperative relay, MACR-CCT selects the cooperative relay together with the receiver in one hop to exploit fully cooperative diversity, so that the receiver is selected for higher cooperative gain and closer distance to destination, and the relay is selected to achieve the better throughput performance while considering transmission error. Furthermore, considering that there are multiple source–destination pairs in MWAN, MACR-CCT takes interference mitigation into account to further improve network throughput when selecting the cooperative relay. Besides, we propose a theoretical model to analyze the throughput performance. Finally, we take advantage of simulation results to validate the effectiveness of our analytical model and show that our proposed MACR-CCT protocol can significantly outperform existing packet transmission mechanisms in terms of throughput and delay under the multi-hop multi-flow network scenario.     

Opportunistic Decode‐and‐Forward Cooperation in Mixed Rayleigh and Rician Fading Channels

We consider a two‐hop multiple‐relay network implemented with opportunistic decode‐and‐forward cooperative strategy, where the first hop and second hop links experience different fading (Rayleigh and Rician). We derive the exact expressions of end‐to‐end outage probability and analyze the approximate results in high signal‐to‐noise ratio region. The analysis shows that the same diversity order can be achieved even in different mixed fading environments. Simulation results are provided to verify our analysis.