说明：  cdma系统matlab仿真，在两个用户的背景下采用了直接扩频码实现扩频解扩，bpsk调制解调，程序已经运行过，没有问题！
(cdma system matlab simulation, in the context of two users using a direct spread spectrum spreading codes realize despreading, bpsk modem, the program has been run before, no problem!)