无线网络协作中继技术研究

发布时间：2018-03-07 10:07

  本文选题：协作中继　切入点：放大转发　出处：《西南交通大学》2014年硕士论文　论文类型：学位论文

【摘要】：相对有线信道,无线信道由于其传播空间的开放性与时变特性,存在衰落效应,信号到达接收端时往往已经发生了严重的衰减或畸变,这种变化主要是由于信号的衰落引起的。空间分集技术以及MIMO技术通过在不同的空间路径上传输多路信号,有效克服了衰落带来的影响,提高了信息传输的可靠性以及系统容量。但是空间分集需要在接收端或者发送端安装一定距离的多根天线,以保证传输的多路信号是不相关的。然而由于移动终端要满足便携性的要求,尺寸不能太大,这就使得空间分集的实用性收到限制。协作中继技术通过不同用户共享彼此的天线实现虚拟的空间分集效果,提高了信息传输的可靠性以及系统容量,在学术界被广泛研究。本文首先对几种常见的分集合并技术进行了讨论,对QPSK调制信号最大比合并、等比合并、选择合并下不同分集链路数对误码率性能的影响进行了仿真,并与无分集时的误码率特性做比较。接着,本文分析了三节点构成的协作中继系统中AF、DF、SDF以及IR四种不同的中继模式,对每种中继模式的误码率性能进行了仿真和分析。然后,针对单向中继系统频谱利用率低的问题,研究了基于DF的两阶段双向协作中继系统的两种主要机制,即基于比特级异或和去噪转发机制在等功率分配时的误符号率性能。并在此基础上以最小化系统的误符号率为目标,在总功率一定的前提下,针对等功率分配方案不能适应中继节点R两侧信道状态差异的缺陷,提出了一种最优的功率分配算法。仿真结果表明,该最优功率分配算法和等功率分配算法相比,可降低系统的符号错误概率,并提高系统的吞吐量性能。
[Abstract]:Compared with wired channel, wireless channel has fading effect because of its open and time-varying characteristics of propagation space. When the signal arrives at the receiving end, it often has serious attenuation or distortion. This change is mainly caused by signal fading. Spatial diversity technology and MIMO technology can effectively overcome the influence of fading by transmitting multi-channel signals on different spatial paths. It improves the reliability of information transmission and system capacity, but spatial diversity requires the installation of multiple antennas at a certain distance at the receiving or sending end. In order to ensure that the transmitted multichannel signal is irrelevant. However, because the mobile terminal needs to meet the requirements of portability, the size should not be too large. This limits the practicability of spatial diversity. Cooperative relay technology realizes virtual spatial diversity through different users sharing each other's antennas, which improves the reliability of information transmission and system capacity. In this paper, several common diversity merging techniques are discussed, and the effects of maximum ratio combination, equal ratio combination, and the number of diversity links on the BER performance of QPSK modulation signal are simulated. Then, four different relay modes, AFDF-SDF and IR, are analyzed, and the BER performance of each relay mode is simulated and analyzed. Aiming at the problem of low spectrum efficiency of one-way relay system, two main mechanisms of two-stage bidirectional cooperative relay system based on DF are studied. That is, the performance of symbol error rate in equal-power allocation is based on the performance of BER and de-noising and forwarding mechanism. On this basis, the target is to minimize the symbol error rate of the system, and under the premise of a certain total power, the symbol error rate of the system is minimized. An optimal power allocation algorithm is proposed to solve the problem that the equal power allocation scheme can not adapt to the channel state difference between the two sides of the relay node R. The simulation results show that the optimal power allocation algorithm is compared with the equal power allocation algorithm. It can reduce the symbol error probability of the system and improve the throughput performance of the system.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN92
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本文编号：1578990