中文摘要：

针对发送端有多个用户（M）并且存在窃听者的无线通信系统的安全问题,在最优用户选择的基础上,提出选择第m佳的用户来发送信息,根据提出的模型思想进一步推出该方案下的安全中断概率表达式,最后通过仿真实验来分析安全中断概率与信道信噪比、安全传输速率以及发送端用户数目之间的关系。仿真结果表明：（1）当固定其他条件不变,主信道信噪比增加、窃听信道信噪比减少、安全传输速率变小和发送端用户增加都能使安全中断概率减小,使系统的安全性能提高;（2）仿真结果与理论分析一致,随着m的减小,安全中断概率减小,系统的安全性能变好,当选择最佳的用户时,系统的安全中断概率最小,安全性能最好;（3）提出的选择方案相对随机选择发送端的用户有显著的优点,降低了通信系统的安全中断概率,有效提高了系统的通信安全。

英文摘要：

In view of security issues of wireless communication system caused by multiple users （M） at sending end and eaves-droppers,on the basis of the optimal user to be selected,this paper proposes the scheme of select the tne best-user for information trans-mitting. Based the proposed model idea,the expressions of secrecy outage probability is derived in this scheme. Through the simulationexperiment, the relation between secrecy outage probability and channel signal-noise-ratio, secure transmission rate as well as number ofusers at sending end. The simulation results show that （1） when the other conditions are constant,the increased signal-to-noise ratio ofthe main channel,decreased signal-to-noise ratio of the eavesdropping channel and security transmission rate as well as increased sourcenodes all can reduce the secrecy outage probability and improve the security performance of the system. （2） The simulation results areconsistent with the theoretical analysis. With the decrease of re,the secrecy outage probability decreases, and the security performance ofthe system gets better. When the best user is selected, the secrecy outage probability of system is the smallest and the security perform-ance is the best. （3） The scheme has the advantages compared with random selection of the user at the source nodes,which reduces thesecrecy outage probability of communication system and effectively improves the communication security of system.