低信噪比下随机交织器识别

针对Turbo码随机交织器参数识别问题,充分利用信道截获数据的软判决信息,提出了一种基于对数符合度的交织映射关系识别算法。该算法从计算总的编码方程成立概率出发,定义了能很好衡量概率大小的对数符合度概念,极大地简化了计算复杂度,使得计算量仅与截获码块数目和交织长度的平方有关,计算方式仅为大小比较与符号提取;再利用正确交织位置能够使总的编码方程成立的概率达到最大这一特性,依次实现各个位置的交织关系的识别。与现有算法相比,所提算法识别性能稍差,但计算复杂度更低。仿真结果表明,在信噪比为0 dB、交织长度为200时,仅需要截获码块数目为500,其正确识别率就能达到100%。

Blind recognition of random interleaver at low SNR

To recognize the Turbo code interleaver,a new algorithm based on logarithmic conformity is proposed,which can make full use of the soft decision information to identify the pseudo-random interleaver of the Turbo code. Firstly,logarithmic conformity is defined to measure the possibility of coding equations. As the result,the calculation complexity which is only related to the number of the code blocks and length of interleaver is simplified greatly and the methods of calculation are just the comparison and symbol extraction. Then,according to the fact that the correct position can make the possibility of overall coding equations maximum,the interleaver position can be recognized one by one. Compared with existed algorithms,the recognition of new algorithm is slightly worse,but its computational complexity is lower. The simulation results show that the correct ratio of recognition can reach 100% at 0 dB by the 500 code blocks,when the length of interleaver is 200.