提出了采用定向天线和最佳中继选择AF 协作策略的多中继协作通信系统，从理论上推导出相应的系统中断概率公式． 结合理论分析结果对中断概率和信噪比、信道衰落
系数、天线功率增益、中继节点数以及节点功率分配系数之间的关系进行了仿真分析． 结果表明: 采用定向天线和最佳中继选择AF 协作策略的通信系统，不但满足军事通信的射频隐身特性要求，而且在小信噪比、深衰落信道及参与协作中继节点有限的条件下，比采用相同策略的全向天线协作通信系统具有更小的中断概率，提高了通信可靠性．

A multi-relay cooperative communication system adopting directive antennas and optimal relay-selection AF cooperative strategy is proposed,and a corresponding formula of system outage probability is derived theoretically.On the basis of the theoretical analysis result,the relationships between the outage probability and the parameters ( namely,the signal-to-noise ratio,the channel fading coefficient,the antenna power gain,the number of relay nodes and the power allocation coefficient) are analyzed by simulations.The results show that the proposed communication system can meet the requirements of military communication for RF stealth,and under the conditions of low signal-to-noise ratio,deep fading channel and limited relay nodes,it has a smaller outage probability in comparison with the cooperative communication system with omnidirectional antennas and the same strategy,which means that the communication reliability is improved.