双向中继协作无线通信系统的波束成形技术研究

摘要中继可以提高频谱利用率和无线传输可靠性，减少基站覆盖盲区、干扰和功率消耗。双向中继同单向中继相比，可在 2 个而不是 3-4 个时隙内完成用户间信息交换，因而具有更高的频谱效率，双向中继技术是目前无线通信领域的一个研究热点。本文研究了无线协作通信系统中的双向中继波束成形技术。论文主要有如下几方面的工作： (1).研究对比了基于 AF 双向中继的三种波束成形技术，分别是最大和速率（Maximizing sum- rate，MSR）方案，最小均方根误差（Minimum mean square error ，MMSE）方案，迫零（Zero- forcing，ZF）方案。仿真结果表明在和速率与误码率的性能上，MSR 方案优于 MMSE 方案，MMSE 方案优于 ZF 方案。但在计算复杂度上，7484
MSR方案最复杂，ZF 方案最简单； (2).研究了信道估计误差对双向中继的影响。引入信道估计误差模型，仿真了修正后的MSR方案，发现随着信道估计误差的增大，系统性能会变差； (3).仿真了一种基于功率分配的波束成形算法，讨论了两种情况，一是在限定的接收信噪比下求解最小总功率，二是在总功率限制下，求解最大的接收信噪比。

关键词双向中继多输入多输出波束成形迫零最小均方误差和速率信道误差
功率分配
Title Beamforming   Study    for   Two-way Relaying   Cooperative
             Wireless    Communication    Systems
Abstract
Relaying can improve spectral efficiency and reliability and reduce blind areas of
coverage, interference and power consumption of base-station. In two-way relaying
systems, unlike one-way relaying, users can exchange information during 2 slots rather
than 3-4 time slots and thus shows a higher spectral efficiency. Therefore, two-way
relaying techniques currently become a hot research topic in the field of wireless
communications.
This paper studies the two-way relay beamforming techniques in wireless
cooperative communication system. The main works of this paper are as follows:
    1. Three relay beamforming methods based on AF two-way relaying are
investigated and compared as follows: maximizing sum-rate (MSR), minimum mean
square error (MMSE), zero- forcing (ZF). Simulation results show that the MSR
performs better than the MMSE in terms of sum-rate and bit error rate and the MMSE
is better than the ZF. However, for complexity, three beamformers have the decreasing
order:    MSR> MMSE>ZF.
    2. The impact of channel estimation error is studied in two-way relaying system.
A channel estimation error model is introduced. Simulation shows that the sum-rate
performance of system will become worse with the increase of channel estimation
error.
3. A beamforming algorithm based on power allocation (PA) is investigated for
two-way relay networks. The problem of minimizing the transmit power under the SNR
constraint and the problem of maximizing SNR under the power constraint are
discussed.
Keywords    Two-way relay    multi - input multi -output (MIMO)    beamforming
zero-forcing (ZF)    minimum mean square error(MMSE)    sum-rate
channel error   power distribution 双向中继协作无线通信系统的波束成形技术研究:http://www.751com.cn/tongxin/lunwen_5468.html