大规模MIMO下最优预编码选择策略研究

大规模多入多出(Massive MIMO)系统中,随着天线数的增加,线性预编码算法的性能逐渐趋于最优,选择合适的线性预编码对系统性能具有重要的意义.针对发射端信道状态信息(Channel State Information at Transmitter,CSIT)不完美的Massive MIMO系统,推导出了迫零(Zero-Forcing,ZF)和最大比传输(Maximum Ratio Transmission,MRT)这两种常见预编码方案在向量归一化方式下的下行可达和速率下界,并给出了证明.随后对两种下界进行了分析,提出了一个关于系统用户数的阈值,当系统用户数和阈值的大小关系不同时,两种预编码性能的优劣关系也不相同.根据分析结果,文章进一步提出了一种以系统中用户数为参量的预编码选择策略,可以保证不论用户数如何变化,系统都能选择出更优的那一个预编码算法来对信号进行预处理.分析的有效性和方案的可靠性通过仿真得到了验证.

The research of optimal precoding selection strategy in large scale MIMO

In massive MIMO (Multi-Input Multi-Output) system, the performance of linear precoding tend to be optimal while the number of the antennas increased. Hence, choosing a appropriate linear precoding has significant meaning to the performance of system. For this paper, analyze the downlink achievable sum rate of zero-forcing (ZF) precoding and Maximum Ratio Transmission (MRT) precoding use Vetor Normalization in massive MIMO system with imperfect CSIT then give proof.Compare the performances of these two precodings and proposed a threshold on the number of users in the system, When the number of users different from the system threshold, the merits of two pre-coding performance also different. According the results , this paper provide a procedure of precoding schemes selection which is depend on the number of system users. This procedure choose the better precoding algorithm no matter the amount of users change. The computer simulation proves the method is correct. Key words: massive MIMO;pre-coding;ZF;MRT; vector normalization