空时分组编码在多入多出系统中的容量分析

Capacity Analysis of Space Time Block Coding in Multiple Input Multiple Output System

研究瑞利衰落信道下正交空时分组编码的信道容量,针对收端已知信道状态信息(CSI)以及收发两端均知CSI的2种情况,给出相应的容量分析及计算公式的推导。在收端已知CSI情况下,采用泰勒级数展开方法,给出一种信道容量的近似表达式,该式可有效简化原有精确公式的计算,获得与真实值非常相似的结果。在收发两端均知CSI情况下,提出一种基于最陡下降算法的简单计算方法,用于求解最优中断门限值,该方法可避免原有求解方法的大量搜索和计算。仿真结果表明,所给出的信道容量精确表达式以及近似表达式均与相应的计算机仿真结果一致,从而验证了所推公式的有效性。

The channel capacity of orthogonal Space Time Block Coding（STBC） is investigated over Rayleigh fading channels.The capacity analysis and calculation are provided based on two different Channel State Information（CSI） cases,one is perfect CSI known at the receiver only,the other is perfect CSI available at the transmitter and the receiver.When the receiver knows the CSI only,an approximate expression of the channel capacity is derived by using Taylor series expansion.This expression can simplify the calculation of the existing exact expression effectively,and obtain similar results with the true value.When the transmitter and the receiver both know the CSI,a simple calculation method based on the steepest descent algorithm is proposed to obtain the optimal cutoff threshold.This method can avoid large number of search and calculation from the existing method.Simulation results show that the derived exact and approximate expressions of the channel capacity are good agreement with the corresponding simulated values,and thus the validity of the theoretical formulae is confirmed.