说明：  一个四用户的扩频通信系统,扩频增益为N 16,采用Walsh码进行直接序列扩频,BPSK调制,无线信道为AWGN信道,在接收
(A four-user spread spectrum communication system with a spread spectrum gain of N 16 using Walsh code for direct sequence spread spectrum, BPSK modulation, and wireless channel for AWGN channel.)