TDD系统中非理想互易条件下双流波束赋形的容量分析

Capacity Analysis of Dual Stream Beamforming in TDD Systems with Nonideal Channel Reciprocity

在时分双工(TDD)多天线系统中,由于上行信道估计误差和上下行传输时延,上下行链路信道的互易性并不理想。针对非理想互易条件下基于最小均方误差线性接收准则的双流波束赋形,通过推导其后验信干噪比,得到了容量上界的闭合表达式。数值和仿真结果表明:所得上界与准确值较为接近;且与理想互易情形相比,非理想互易性对系统的复用增益没有影响,而只会降低系统的阵列增益。

In a time division duplex （TDD） multiple antenna system, the channel reciprocity between uplink and downlink is not ideal due to the uplink channel estimation error and the transmission delay between the uplink and downlink. In this paper, we investigate dual stream beamforming in the scenario of nonideal reciprocity giv- en minimum mean squared error （MMSE） linear receiver, and derive the close-form expression of upper bound （UB） on the ergodie capacity by analyzing the corresponding post-SINR （Signal to Interference plus Noise Ratio）. The numerical and simulation results show that the derived capacity UB is close to the accurate value, and the nonideal reciprocity only decreases the array gain while dose not impact the multiplexing gain.