隐蔽通信中变换域通信系统双门限基函数设计

Design of double-threshold basic function in transform domain communication system for covert communication

针对变换域通信系统中传统基函数二进制门限设计单一固定,且未考虑系统隐蔽性的缺点,提出了一种双门限基函数设计方法.通过理论分析推导,验证了基于高阶累积量进行系统隐蔽性评价的合理性.并通过高、低门限的合理设定,确立基函数幅度谱与干扰幅度谱的动态关系式.建立了以降低系统误码率为准则的优化模型,采用遍历法进行最终优化搜索.仿真结果表明:与传统的二进制门限设计相比,所设计双门限优化算法在隐蔽性上与传统二进制门限相当,且能够实现误码率性能的提升.此外,所设计的双门限结构与传统二进制门限能有效兼容.

As conventional basic function has single-fixed binary threshold and could not take the system′s concealment into account in transform domain communication system,thus,an optimal method to design double-threshold basic function was proposed.Through theoretical analysis and deduction,the rationality was testified to evaluate the system concealment based on high order cumulants.By setting high and low threshold properly,the dynamic expression between basic function amplitude and jam amplitude was derived.With the bit error rate（BER）reduction as a criterion,the optimal model was designed and the traversing method was adopted to obtain the optimal solution.Simulation results show that the double-threshold design can improve the BER performance in comparison with the conventional binary threshold design,while achieving the same concealment.The proposed double threshold can be well compatible with the conventional binary threshold.