从信息理论安全的角度研究正交中继-窃听信道中的安全通信. 考虑采用瞬时中继策略的中继信道，即中继的输出仅依赖当前接收信号，首先给出可达安全速率的表达式，在此基础上得到中继函数为分段线性函数时信道安全速率的数学表示. 给出了安全速率的数值计算方法，通过迭代网格搜索优化分段线性函数的各段参数，得到了安全速率的次优解. 通过仿真对比了分段线性中继策略、放大前传策略、译码前传策略下的可达安全速率，结果表明分段线性中继比放大前传中继策略的可达安全速率更大. 当源-中继信道增益较小时，分段线性中继的安全速率比译码前传策略更高，复杂度更低且时延更小.
In this paper, secret communication in an orthogonal relay-eavesdropper channel is studied in view of information-theoretical security. For an orthogonal relay-eavesdropper channel with instantaneous relay in which the present output depends only on the currently received signal, the achievable secrecy rate is
formulated. The achievable secrecy rate with piecewise linear(PL) relaying function is derived and computed numerically. A sub-optimal solution to this secrecy rate is obtained by optimizing the parameters of the piecewise linear function with an iterative grid search algorithm. The achievable secrecy rate with PL relaying is compared to that with amplify-and-forward (AF) relaying and decode-and-forward (DF) relaying by simulation. The results show that PL always outperforms AF, and outperforms DF when the source-relay link is poor. Meanwhile, compared with DF, PL relaying has lower complexity and lower time-delay.
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