相关衰落信道下闭环发射分集方案的性能分析

Performance Analysis of Close Loop Transmit Diversity Scheme under Correlated Rayleigh Fading Channel

未来移动通信系统采用的关键技术之一是发射分集技术,如WCDMA标准中采用了一种称作闭环发射分集的方案,用于下行信道传输。闭环发射分集方案使用了前向信道的相位与幅度的部分信息来选择天线的加权系数,在信道时变速率较小时,闭环发射分集的性能优于开环发射分集方案。在一般情况下,假设两个发射天线之间距离足够大,各个发射天线到接收天线的信道是不相关的,在基站这种假设是合理的。但如果在上行信道传输中(移动台到基站)应用闭环发射分集技术时,天线之间不相关的假设很难满足。本文基于对移动台配置多天线并应用闭环发射分集技术的考虑,研究在相关瑞利衰落信道下闭环发射分集技术的性能。蒙特卡罗仿真给出了不同相关系数下的性能曲线,并得出一个具有指导意义的结论。

Transmit diversity is one of the key contributing technologies to defining the ITU endorsed 3G systems WCDMA and CDMA 2000 It can be divided into two categories,close loop transmit diversity and open loop transmit diversity When using transmit diversity technologies, the antennas are assumed to be spaced far enough apart,that the signals emanating from them can be assumed to undergo independent fading Base stations can satisfy the assumption easily,but in a mobile terminal with multiple antennas it is often difficult to provide enough space for independent antennas In this paper, we discuss the situation using close loop transmit diversity where channels are correlated fading Monte Carlo simulations are used to compare performance of close loop transmit diversity when correlation coefficient of channels vary from zero to one Through analyzing the simulation result we drew an inscructive conclusion