Research On Turbo-code Decoding Algorithm And Interleaver

Channel coding can control the process of transmission error, so that it makes thereliable data to reproduce. Channel coding becomes an inseparable part of moderncommunication systems. Turbo code as a leader in channel coding is a invention ofmilepost in coding theory. There are two basic idea of Turbo coding technology: one isthe design scheme with random code, the other is the design of using soft output anditerative decoding. Because the Turbo code realizes the code design of Shannon expectedwith random characteristic, so the Turbo code achieves excellent performance whichclose to Shannon limit.Firstly, this paper describes the coding structure of Turbo code, a detaileddescription of the Turbo code encoding process with parallel concatenation is made, andeach of the encoder component is briefly analyzed; decoding structure of Turbo code aregiven, and analyzes the process of the basic iterative decoding; we study terminationcondition of the iterative decoding of Turbo code, and get the termination expression andreasonable; then summarize the basic conclusion of the Turbo code.Secondly, the MAP decoding algorithm of Turbo codes are studied, and proposes animproved Log-MAP algorithm. The algorithm based on linear fitting method, the formertwo sections of approximation correlation function is replaced by quadratic polynomial.It makes the fitting function curve approach the correlation function. The simulationresults show that, the improved Log-MAP algorithm is better than Log-MAP algorithm incomputation complexity and the delay of decoding, and error correction performancecomparable to that of Log-MAP algorithm. It simplified the decoding algorithm, andreduce the difficulty of hardware implementation at the same time, so that promote theapplication of Turbo codes more widely in communication system.Finally, analysis the basic principle of interleaving and its design idea, systemdesign step helical interleaver in short frame communication. The interleaver is largelyincreased the distance between adjacent bits of information, make the possibility ofcontinuous burst error after interleaver still continuous greatly reduced. It has very good effect on burst error, and the error correcting performance of Turbo codes is significantlyimproved. The design will be good at application prospects in the communication systemwhich have high requirements with decoding time and hardware complexity.