基于变换域选择的干扰抑制技术

在无线通信系统中存在各式各样的干扰,尤其在军事通信中。不同类型干扰信号在时/频域具有不同的信号特征。现有的干扰抑制算法都是在特定域上进行干扰抑制。研究了一种基于变换域选择的干扰抑制算法,并提出了一种改进的度量选择算法,该算法可以有效地选择最佳变换域去抑制干扰。这种算法简单、且容易实现,复杂度也比较低。仿真结果表明这种算法对于抑制不同的干扰有较好的性能。

短波宽带波形干扰抑制技术

短波宽带波形是现代短波通信的最新研究成果,采用带宽扩展方式实现短波高速通信。短波信道存在的各种各样强干扰信号使得干扰抑制成为现代短波宽带通信急待解决关键问题之一。针对这种现象,提出了一种基于变换域选择的双门限干扰抑制方法,该算法可以有效地选择最佳变换域去抑制干扰。仿真结果表明这种干扰抑制方法能够抑制不同类型干扰信号,在干扰环境下短波宽带波形具有较好传输性能。

Permutation-substitution image encryption scheme based on a modified chaotic map in transform domain

A new chaotic image encryption scheme based on permutation and substitution in the Fourier domain is presented.Fractional Fourier Transform(FRFT)is used before the encryption scheme to get a large degree of randomization.The permutation is achieved by Baker map and the substitution by a key-related-to-plain-image algorithm based on the modified Logistic map.Modification of the Logistic map is developed to increase the space of the encryption key,and hence increase the security.The key of the encryption algorithm dependents on the plain image,and thus,the cipher image is sensitive to both the initial key and the plain image to resist known-plaintext and chosen plaintext attacks.The key space is large and hence the algorithm can effectively resist brute-force attacks.The proposed scheme is examined using different performance evaluation metrics and the results prove that the proposed scheme is highly secure,and it can effectively resist different attacks.