多输入多输出系统发射天线选择对系统信道容量的影响

针对多输入多输出(MIMO)系统信道矩阵秩亏引起信道容量下降的问题,基于信道容量上限提出了一种发射天线选择方法.该方法利用信道矩阵与发射空间相关矩阵秩相同的特点,重新构建了蕴含模型物理参数的信道模型.在对空间相关矩阵QR分解的基础上,采用随机矩阵理论推导了迫零接收机信噪比的概率密度函数,从而得到了MIMO系统信道容量的上限.该方法不需要已知信道的瞬时状态信息,只取决于衰落的空间相关,计算的复杂度较低,易于实现.仿真结果表明:在低散射环境中,适当地选择发射天线可以使系统的信道容量增加约1 b/s;当接收信噪比大于6.5 dB时,发射端采用均匀圆阵系统的性能要优于采用均匀线阵系统的性能.

Transmit Antenna Selection and Its Impact on the Capacity of Multiple Input Multiple Output Systems

The rank deficient channel may result in a substantial decrease of the channel capacity of a multiple input multiple output (MIMO) system.Focusing on this problem,a novel method was proposed to select the optimum set of transmit antennas based on the upper bound on the mean channel capacity.On the analysis of the properties of the fading correlation and the rank of the channel,the QR decomposition of fading correlation was calculated and the distribution of the receive signal-to-noise ratio(SNR) of a zero-forcing receiver was derived by using random matrix theory.Sequentially,the upper bound on the mean channel capacity of MIMO system was given.The proposed method based only on the fading correlation and not the instantaneous channel realization.And also its computational complexity is low and tends to be realized.The simulation results show that antenna selection of transmitter can increase the channel capacity of MIMO system by 1 b/s in a flat fading environment with a rank deficient channel.And at high SNR(>6.5dB),the uniform circular array yields higher channel capacity than uniform linear array.