卫星通信目标信号精确识别仿真研究

Simulation for Accurate Identification of Target Signals in Satellite Communication

不归零Turbo码广泛用作卫星通信信号,而完成其码率、码组起点、交织长度、交织起点初始参数识别是后续参数识别的前提,针对目前算法时效性差的缺点,提出了相应的改进算法。首先基于矩阵分析的思想,引入了矩阵秩量比的概念,通过构造分析矩阵,记录矩阵秩量比小于1时的矩阵列数,实现码率与码组起点的识别;其次,推导出不归零Turbo码矩阵秩量比下限,提出了基于判决门限的交织长度识别算法,可快速识别出不归零Turbo码交织长度大小;最后,通过遍历交织帧输出码元的起始位置,寻找最小矩阵秩量比所对应的输出位置,从而实现交织起点的识别。仿真结果表明:提出的算法能够在较低信噪比下实现各个参数正确的识别,针对码长的识别,与传统算法相比,新算法识别的时间大大缩减。

The Turbo codes which are not on the trellis termination are widely used as satellite signals, and the prerequisite for subsequent parameter is completing identification of the code rate, start point of code group, interlaced length and start point. According to the current algorithms＇ deficits, this paper puts forward the recognition algorithms based on the theory of matrix analysis and the special structure of the code. The columns of analytical matrixes which rank ratio is less than one can be memorized to realize the identification of code rate and start point of code group by constructing the analytical matrixes. Then, based on the concept of rank ratio, the lower bound of rank ratio was derived and then the recognition algorithm based on the decision threshold was proposed, which can efficiently identify the interleaving length of Turbo code which is not on the trellis termination. Finally, the position according to minimum of the rank ratio can be found by traversing a starting position of interleaving frame output symbols, so as to realize the identification of starting point of interleaver. Simulation results show that the proposed algorithms can realize the recognition of each parameter correctly at low SNR; compared with traditional algorithm, the new algorithm can reduce the recognition time greatly according to the recognition of interlaced length.