申論題

6.(20%) Consider a simple communication system that contains a single antenna at the transmitter and M antennas at the receiver. The received signal at the mth antenna with a binary transmitted signal can thus be expressed as
 y_m =uh_m +w_m,
where u = ±a is the transmitted signal, h_m is the gain of antenna m, and w_m is the associated AWGN with zero mean and variance σ² . Herein, u, w₁，...， w_M are mutually independent. Collecting Y₁,.... Y_M into a vector, we have