Research On Encoding And Decoding For Turbo Codes In Mobile Communication

Mobile communication system use error-control coding to improve reliability of news transmission. Since the Shannon's Information Theory has proposed, many channel coding is invented, such as Hamming codes,Conolutional codes, RS codes etc. C.Berrou et al invented Turbo codes in 1993 has captured great importance due to exhibiting near Shannon-limit performance, it has far-reaching influence on channel coding. In recent years, Turbo codes not only as a 3G (The Third Generation Mobile Communication) channel encoding scheme, it still used in the LTE (Long Term Evolution) technology for correctting and anti-jamming.Due to the complexity of Turbo iteration decoding, the delay is seriously, so it has some limitation in the use of Mobile communication. The research of Turbo code has been committed to improve performance and reduce the delay, and it is also the main research direction of this paper. This thesis introduced the Turbo coder scheme, arithmetic in detail and the design parameters (constitutive codes, interative times, encode rate et al) which have influence on its performance at frist, then introduced the 3GPP (The 3th Genaration Partnership Project)interleaver and analyzed the distance spectrum of Turbo codes, and an improved 3GPP interleaver applied under low signal-to-noise ratio condition, then introduced the parallel decoding Turbo codes in LTE, study the decoding structure, memory collision free interleaver and decoding algorithm, improve the key technology—memory collision free interleaver. At last Turbo encoder is achieved by use of VHDL language.The main innovation of this thesis is below:①This thesis improved 3GPP interleaver. On the condition of design steps of the basic interleaver does not change, the improve method simplify its structure, so the transmission BER of the short-frame at low SNR conditions was improved.②The parallel decoding Turbo codes in LTE is analyzed, improved the key technology--memory collision free interleaver. Used S-random regulation into common row column random interleaver again, and make the distance of adjacent data increase after interleaving in every processor . The simulation figures show, this improved design scheme to make better the code weight of parallel decoding Turbo codes, and the bit error rate performance is better.