Design Of Turbo Interleaver And Research On Relevant Techniques

Code controlled by error is based upon Shannon theory, while the present of turbo code is viewed as an important landmark in the development of error correction code. Turbo code, which utilizes the condition of random coding and decoding of Shannon coding theorem and makes iterative decoding approach maximum likelihood decoding, has obtained the performance near to Shannon theoretic limit. So turbo code is research hotspot in the field of channel coding.Turbo code achieves random coding by using interleavers, and it takes on good performance. Therefore interleaver acts a very important part in turbo code system. This paper designs a new interleaver which is suitable for short frame systems and entitled double-helical interleaver. It adopts helical method for write-in and read-out, and it improves the distance spectrum between code words. As a result, the performance of decoding is improved. The simulation results show that it has better performance than other typic regular interleavers.Iterative decoding is significant for turbo code to gain good capability, while stopping criteria takes a crucial part in iterative decoding. This paper proposes a new stopping criteria which is based on external output of encoder, according to the output characteristic of iterative decoding. This rule can choose iterative parameters by itself according to practical system. The simulation results indicate that the new rule can get less number of iteration and system performance increase under lower SNR, at the same time it cuts down computation time and reduces time delay of system.In order to know the effect of factors which affect turbo code, these factors are also analyzed and simulated. In this way, the emphases of design can be known from different aspects when turbo coding system is designed.