Research On A New Type Of Concatenated Codes

In 1993, Claude Berrou, Alain Glavieux and Punya Thitimajshima published the paper which first described Turbo codes. Turbo codes have been becoming a popular area of communications research.Simulations show that Turbo codes could achieve low BER as SNR very close to Shannon Limit. When SNR below 3.0dB, traditional Turbo codes has powerful error-correcting capability; But when SNR larger than 3.0dB, its BER performance become flat. This shows that the increment speed of error-correcting capacity slowing down as signal to noise ratios increasing. When using these codes to get low BER, for example 10~-8, they also need a high SNR. As we all know, high SNR may brings a series of problems, for example wasting energy and leakage of information.In order to solve this problem we can construct long codes with two or more short codes base on concatenated encoding theory. This paper presents a new type of concatenated codes which consist of Turbo code and BCH code. That is to say Turbo codes extended with outer BCH codes. In these concatenated codes, BCH codes that can correct a few random bit errors are used to rectify the residual bit errors after Turbo decoding.Then the encoder and decoder of the concatenated codes are programmed. The programs are loaded to TMS320VC5410 respectively. So it can realize the real time processing of the concatenated codes by hardware.Simulations show that: concatenated codes become more and more powerful than traditional Turbo codes as SNR increasing. They can realize a low BER at relatively low SNR.