Turbo码的Simulink建模及性能测试

针对Turbo码编译码器结构复杂、仿真困难的问题,提出了一种完全基于Simulink模块的Turbo码仿真模型。编码器中,分量码采用循环系统卷积码,使分量码的奇序列与原始信息相同。译码器采用流水线译码方式,由Simulink模型库中的后验概率译码(A Posteriori Probability Decoder)模块构成,使译码过程变得直观和便捷,简化了编译码器的复杂性。通过仿真,分析了迭代次数、交织长度及不同译码算法对Turbo码性能的影响。结果表明,单比特信噪比(Eb/No)为2 dB时,误比特率(BER:Bit Error Rate)可以接近10-7;迭代次数增加到7次以后接近饱和;交织长度越大,Turbo码性能越好。

Modeling in Simulink and Performance Test of Turbo Codes

A Simulink model of a Turbo encoder and decoder is presented to make Turbo code simulate conveniently against the complicated Turbo code structure.In the encoder,the odd outputs of convolutional encoders are the same as the original signal because of using recursive systematic convolutional encoders with feedback.The pipelining decoder is based on APP(A Posteriori Probability)decoder block in Simulink,so the process of coding becomes convenient and vividly.By simulating,the factors,such as number of iterations and length of interleave as well as different arithmetic,which influence on the performance of turbo codes are presented.As is shown in the results of simulation,the BER(Bit Error Rate) is near to 10-7 when Eb/No is 2 dB;the number of iterations comes to saturation at 7;the longer the length of interleave is,the better the performance of turbo codes.