RS_Turbo级联码的性能仿真分析

为了利用RS码在高信噪比时的性能优势和Turbo码在低信噪比时的性能优势，从而进一步提高系统的抗误码性能，将RS码和Turbo码串行级联，并搭建了级联OFDM的WiMax系统进行仿真验证。高阶调制的解调采用最大对数似然比软解调算法，分析了级联码在不同调制模式下基于高斯白噪声和衰落信道的误码性能。仿真结果表明，该系统相对于RS码与卷积码的级联系统有2-3dB的编码增益，而且降低了Turbo码的迭代次数，克服了误码平台现象，达到降低系统复杂度和延时要求。

Simulation Analysis on Performance of RS_Turbo Concatenated Code

RS codes perform better when the signal to noise ratio is high, while the Turbo codes have better performance in low signal to noise ratio channel. In order to make full use of this fact and improve the anti-error performance of the system, RS code and Turbo code were serially concatenated. And a cascaded OFDM WiMax system was set up to analyze the bit error rate （BER） performance in different modulation modes based on white Gaussian noise and fading channel. The algorithm for soft decision of high order modulation is max-log likelihood ratio （MAX-LLR）. It is proved that this system has a 2-3 dB coding gain compared with the RS code concatenating convolutional code. Also, the iterations of Turbo code are reduced, with the phenomenon of error floor avoided. Therefore, the complexity and delay of this system is reduced effectively.