关键词: 多入多出系统, 信道容量, 空时分组编码, 最陡下降算法, 泰勒级数展开

Abstract: 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.

Key words: Multiple Input Multiple Output(MIMO) system, channel capacity, Space Time Block Coding(STBC), steepest descent algorithm, Taylor series expansion