差分跳频系统编码器与频率转移函数的匹配设计  

Matching design of encoder and frequency transition function in different frequency hopping system

作　　者：刘智泉[1] 潘克刚[1] 王庭昌[2] 

机构地区：[1]解放军理工大学通信工程学院,南京210007 [2]总参63研究所,南京210007

出　　处：《南京大学学报（自然科学版）》2009年第4期508-516,共9页Journal of Nanjing University（Natural Science）

摘　　要：将编码的差分跳频系统等效为串行级联码,充分利用频率转移函数所产生的网格关联信息,采用软输入软输出算法,进行类Turbo串行迭代译码,能有效改善系统的误比特性能.因此,如何实现差分跳频系统串行级联结构的外编码器和频率转移函数(G函数)的匹配设计是值得深入研究的问题.基于互信息的外信息转移图(EXIT)能有效预测迭代译码的收敛特性,并根据EXIT选择适当的内、外码进行级联.采用基于互信息的EXIT图分析差分跳频串行级联结构中外编码器和G函数的外信息转移过程,提出了一种采用EXIT图选择G函数及外编码器的方法.通过对该方法的理论分析和性能仿真,结果表明,在一定的输入先验信息量条件下,信噪比越高,G函数输出互信息量越大;在给定信噪比条件下,不同G函数对应的输出互信息量随输入先验信息量增长速度不同,能有效实现对性能较好的G函数的选择;对于给定G函数,在不同外编码方式下,通过EXIT图能得到迭代译码收敛的门限值;能反应出不同编码方式下的收敛特性的好坏,从而实现外编码器和G函数的匹配设计.Differential frequency hopping（DFH） is a new kind of frequency hopping communication technology.The data stream is sent by using the change of two successive frequencies in a determined way.DFH has overcome traditional problems that limit the utilities of the high frequency（HF） systems.These problems are： limited bandwidth with resultant low data rates,mutual signal interference,and the multi-path fading.We should analyze the system performance and study DFH demodulation algorithm deeply which is important to the research on the system of anti-jamming of communication.The conventional DFH demodulation algorithms are based on mapped pertinence of frequency transition function（FTF） which the data will be decoded according to the detection frequency information and that incorrect or missed hops can be modified.Viterbi algorithm is applied to maximum likelihood estimation frequency sequence decoding.But it has not taken full advantage of the pertinence determined by FTF in these algorithms which has a bad performance of bit error rate（BER） and can not provide the soft-output information.So that the system gain of coding is limited.Coded DFH system will be equivalent to serial concatenated convolutional code（SCCC）.Making full use of the Grid related information generated by frequency transfer function and using soft-input soft-output algorithm,it is similar to turbo serial iterative decoding and it can effectively improve the BER performance.Therefore,how to realize matching design of outer encoder and frequency transition function in DFH system with serial concatenated structure deserves a closer study.Since the discovery of parallel concatenated（turbo） codes,iterative decoding has become a vital field of research in digital communications.The extrinsic information transfer chart（EXIT（extrinsic information transfer） chart） can be used to illuminate the convergence properties of bit-interleaved coded modulation,equalization,and serially concatenated binary codes.The EXIT chart leads

关 键 词：差分跳频 频率转移函数 外信息转移图 迭代译码 串行级联码 

分 类 号：TN914[电子电信—通信与信息系统]