Turbo码结合已知比特的不等保护方案设计

交织器的引入使Turbo码对不同信息位具有明显的不等保护特性，从而对其性能产生影响。为了提高Turbo码译码性能，在给定的S距离伪随机交织器下，首先通过对多组随机输入信息序列的位误比特率仿真分析，找到对Turb0码性能影响较大的关键比特位置，然后在对Turbo码不等保护特性和已知比特Turbo码进行理论分析和研究的基础上，提出了关键比特不等保护和结合已知比特的Turbo码不等保护两种方案。最后，对提出的方案进行了仿真验证，结果表明在交织长度分别为200和400两种条件下，两种保护方案在高信噪比时与未保护相比均有0．2dB以上增益．且结合已知比特的Turbo码不等保护方案比关键比特保护方案性能更优。

Unequal Protection of Turbo Code based on Known Bits

The introduction of interleaver makes the Turbo code have the obvious unequal protection of different information bits, thus limiting the performance of turbo code. In order to improve the performance of Turbo code, and under certain condition of given S-random interleaver,the key bits which may seriously impact the performance of Turbo code could he searched out through simulation and analysis on the bit error rate of input information sequences. Based on analysis and research of the unequal protection and KB （knownbits） turbo code,the two protection schemes,including the key-bit protection and the known-bit protection, are proposed. Finally, the simulation indicates that with the different interleaving lengths of 200 and 400, the proposed schemes both could have more than 0.2dB SNR gain under the condition of high SNR, while the known-bit protection scheme could acquire even better performance than the key-bit protection scheme.