【作者】 杨晓峰；

【导师】 陈红；

【作者基本信息】 西南交通大学 ， 通信与信息系统， 2011， 硕士

【摘要】 由于无线信道的衰落特性,无线通信的性能会受到严重影响。为了有效对抗无线信道衰落特性,研究者提出了多输入多输出(Multi-Input Multi-Output, MIMO)技术,但它的实现需要在终端安装多天线。在实际的应用中,由于终端受尺寸、功率等条件的限制而无法配置多天线,从而限制了MIMO的实用化。为了克服MIMO的这一缺点,协作通信的概念被提出并且引起了研究者的极大兴趣。它的主要思想是通过相邻节点间彼此相互转发信息,形成一个虚拟的MIMO系统,通过分布式的方式获得MIMO增益,从而提高系统性能。本文主要对协作通信中的中继选择和功率分配进行了研究。全文共分六章,主要工作体现在以下几点：首先,本文对协作通信的研究现状做了概要的阐述。结合本文的研究内容,对中继技术的研究进展、协作通信的中继选择和功率分配研究做了简单介绍。其次,介绍了协作通信的相关技术。其中包括常见的分集技术和合并方式,协作分集和协作转发协议,并对放大转发(Amplify-and-Forward, AF)和译码转发(Decoded-and-Forward, DF)协议的性能进行了简单的仿真并比较了它们的性能。接着,针对放大转发系统,结合最优中继选择分析了基于门限的中继选择,分析了M-PSK和M-QAM调制下系统的误符号率和带宽效率。仿真结果表明,门限较低时,系统的性能接近最优中继选择的性能。在不同的信噪比和中继节点数下,可以适当调整门限来获得较好的系统误符号率性能或带宽效率。最后,在系统总功率一定的条件下,分析了AF和DF系统的功率分配问题,并对不同的分配方案进行了仿真。针对AF系统,首先分析了最小化误符号率和最大化系统容量的功率分配方案,然后分析了综合考虑误符号率和系统容量的联合分配方案。对DF系统,分析了最大化系统容量和最小化误符号率的功率分配方案。结合功率分配问题,论文还分析了中继节点位置对系统性能的影响。更多还原

【Abstract】 The performance of wireless communication will be seriously affected due to the fading characteristic of the wireless channel. In order to effectively combat the fading characteristics of wireless channel, Multi-Input Multi-Output (MIMO) technology has been proposed by researchers. However, the realization of MIMO need to configurate multi-antenna on terminals. In particular, due to the restrictions such as size, power etc, the terminals can not configure multiple antennas, which have limited the application of MIMO technology. To overcome this drawback, the concept of cooperative communications has recently been proposed and gained large interest in the research community. The main idea of cooperative communications is to form a virtual MIMO system by utilizing neighbor nodes mutually transfer information on each other. With this approach, the benefits of MIMO systems can be attained in a distributed fashion, thereby improving the system performance.This thesis focus on relay node selection and power allocation in cooperative communications systems carried out researching. The thesis is divided into six chapters, the main contents are listed as follows:Firstly, the research status of cooperative communications has been illustrated generally. With the contents of this sthesis, the research progress of relay as well as the relay selection and power allocation in cooperative communications have been introduced in a brief way.Secondly, a brief introduction has given to the related technologies of cooperative communications, which including the common diversity and combing methods as well as cooperative diversity and relaying procotols. The performance of Amplify-and-Forward (AF) and Decoded-and-Forward (DF) have simply simulated and compared.Next, combed with best relay selection, a threshold relay selection method has been analyzed in AF system. The symbol error rate as well as bandwidth efficiency have been analyzed for this method under M-PSK and M-QAM modulation schemes. Simulation results illustrate that the performance of the threshold method approaches to the best selection method in a low threshold condition. What’s more, in different SNR region and relay nodes, better SER performance or bandwidth efficiency can be obtained by adjust the threshold to an appropriate value.Finally, the power allocation issue has been analyzed in AF and DF systems under the conditon that the total system power is constant. The performance of different power allocation schemes have simulated. For AF system, the allocation schemes based on minimize the symbol error rate and maximize the system capacity have been analyzed, and then a joint allocation scheme has been analyzed. For DF system, the power allocation schemes for the purpose of maximize the system capacity and minimize the symbol error rate have been analyzed. Combined with the power allocation issue, this thesis analyzed the location of the relay nodes impact on the system performance both for AF and DF system.更多还原