说明：   该程序是使用Matlab仿真协同通信的DF（解码转发）基本性能，基本模型S-R-D三个节点，接收端使用MRC（最大比合并）。固定DF由于SR信道的错误，其性能受到限制，在大SNR情况下不能获得有效分集。而当SR距离足够近的时候，可能获得一定的分集增益
(The program is a cooperative communication using Matlab simulation DF (decode forwarding) basic performance, the basic model of the SRD three nodes, the receiver uses the MRC (maximum ratio combining). Fixed DF error of the SR channel, its performance is limited, can not obtain a valid diversity in the large SNR case. When the SR close enough, you may get a certain amount of diversity gain)