中文摘要：

研究了发送端未知、接收端已知信道信息条件下，离散调制信号输入时MIMO衰落信道容量。提出了一种有效的信道容量估计方法，仿真结果表明，该估计方法降低计算的复杂度同时获得了很好的近似结果。通过该估计方法比较了接收天线不同时，PSK输入与高斯输入时的信道容量。低信噪比时，PSK输入可获得与高斯输入相同的传输速率，而且在天线数一定的情况下，应尽量增加接收端天线数来增加系统传输速率。

英文摘要：

The capacity of the Multiple Input Multiple Output （MIMO） system with constellations is studied by assuming perfect channel state information （CSI） at the receiver. An expression for the discrete capacity of the Rayleigh, flat-fading, MIMO channel is derived, and an evaluation method of the discrete capacity is presented. Nu- merical results show that the proposed method can accurately estimate the discrete capacity with less computation, which make the evaluation of constrained capacities become possible for large MIMO channels. The method is also used to compare the QPSK and Gaussian input capacities with different antenna selections. Numerical results show that Gaussian input and PSK input can achieve about the same data rate at low signal-to-noise ratio （SNR）.