中继协作通信场景下的联合优化设计毕业论文

论文总字数：43206字

摘 要

在MIMO无线通信技术中，假设有一对多天线的信源和信宿，那么在特定的条件下两者之间安置中继（Relay）是有助于信号的收发与传输的。使用中继进行协作通信，不仅可以对进信号放大并转发，起到中转保持的作用，而且将有助于优化源端和目的地端之间的容量。本设计以三端口MIMO正交信道模型为基础，研究对比两个调频链路，一条是没有直接连接的中继链路，另一条是有中继的直接连接链路。先简单计算没有中继的直接连接链路下的信道容量，用于与加入中继后的系统信道容量进行对比。考虑没有直接连接的情况，先建立不同链路的信道矩阵，定义符合优化正则坐标的中继加权矩阵，然后找到沿优化正则坐标的优化功率分配，再把信道矩阵奇异值分解、获得中继矩阵特征值，最后通过变化不同的变量得到遍历容量的曲线。此时选用了其他三种常见的中继方案进行比对，分别是次优中继方案、放大并转发中继方案和伪匹配并转发中继方案，而优化中继矩阵下的系统容量要远远高于其他中继方案下的系统容量。当有直接连接的时候，则把两条正交信道以矢量的形式叠加，分析讨论优化系统的上下边界问题，上界由该模式下宽松功率条件给定，下界由放大并转发中继矩阵给定。

关键词：中继协作通信；MIMO；信道容量；优化正则坐标；功率分配。

Joint optimization of communication systems assisted by cooperative relays

Abstract

In the MIMO wireless communication technique, given a multi-antenna source and a multi-antenna destination, a relay between the source and the destination is desirable to help transmit signals under certain circumstances. Relays for the auxiliary communication are designed not only to amplify and forward the signals but also to optimize the capacity between the source and the destination. In this project, based on the three-terminal orthogonal MIMO channel model, one route is a relay without a direct link while the other is a direct link without a relay. Firstly we calculate the capacity between the source and the destination without a relay, in order to compare with those equipped with a relay. Consider the relay linking between the source and the destination, channel matrices of different routes are first established, the optimal canonical coordinates of the relay weighting matrix are defined, and the optimal power allocations along these coordinates are then found. Meanwhile, channel matrices should be decomposed into singular values and eigenvalues of relay weighting matrix should be found, in order to graphically display the ergodic capacity varying with different variables. Here we have three other common relay schemes used to compare which are SOR, NAF and PMF while the system capacity with the optimal relay matrix is shown to be significantly higher than the others. When a direct link is present, two orthogonal channels are first added in vectors, then upper and lower bounds of the optimal system capacity are discussed. The upper bound is decided by the loose power constraint under this mode while the lower bound is decided by the NAF relay matrix.

Keywords: communication assisted by relay; MIMO; channel capacity; optimal canonical coordinates; power allocation.

目 录

第1章 引言 1

第2章 中继协作通信的基本理论知识 3

2.1 中继协作通信 3

2.2 多天线MIMO系统 4

2.3 多天线MIMO系统的特征 4

2.3.1 信道容量 4

2.3.2 空间复用 5

2.3.3 发送分集 5

2.3.4 空间复用和分集的平衡 5

2.4 MIMO信道容量 6

2.4.1 信息论知识推导MIMO信道容量公式 6

2.4.2 奇异值分解理论推导MIMO信道容量公式 7

第3章 系统设计主体内容 9

3.1 系统模型及问题公式化 9

3.1.1 无中继的直接连接 9

3.1.2 无直接连接的中继 10

3.1.3 有直接连接的中继 11

3.2 优化中继矩阵 12

3.3 加权矩阵符合正则坐标 13

3.4 优化功率分配 14

3.5 用于对比的其他中继方案 16

3.5.1 次优化中继(SOR) 16

3.5.2 基本放大并转发(NAF) 16

3.5.3 伪匹配并转发(PMF) 16

3.6 仿真流程描述 17

第4章 结果分析与讨论 18

4.1 无中继的直接连接链路 18

4.2 无直接连接的中继链路 19

4.3 有中继的直接连接链路 23

第5章 结论 26

参考文献 27

附 录 28

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