The Improved Algorithm Of Turbo Codes Based On A Reliable Measure Of Value

The purpose of communication is be able to transmit the information safely and efficiently,In the present communication system, Turbo Code as a new communication coding scheme whitch rises nowdays,Experiments show When using a random interleaver,SNR is not less than0.7dB,after18times iteration,Turbo code achieved performance which closes to the Shannon limit.However, there are still many aspects which is waitting to be developed about Turbo codes,For example, the theory explains the principles of decoding Turbo codes are not sufficient, in the high SNR environment,Too many iterations reducing the Turbo decoding rate in Turbo codes, in the low SNR environment, the accuracy of Turbo code needs to be improved.Tthe Research For Turbo codes includes the following aspects in this paper.(1)A general description of the entire development process of Turbo Codes, also explains the advantages and disadvantages about the performance of Turbo codes,Also analyzed reasons that why Turbo codes can achieve excellent performance In some systems, then analyze The key technologies (Such as encoding, decoding, etc.) about Turbo codes Systematically.(2)This paper presents an improved stopping iterative algorithm named PE-CRC stopping iterative algorithm,The algorithm analyzes the traditional CRC check code section,Calculate a reliable value for every intermediate result, and achieve the purpose of early termination of the iteration by comparing this value with the value of a valve.Meanwhile, when the results of the iteration does not converge,Improve the accuracy of the decoding of Turbo codesBy exporting the middle of the decoding results with the most reliable final results as the end result. (3)Based on the PE-CRC iterative stopped algorithm, the paper furtherly proposes a new retransmission algorithm of Turbo codes—PE-CRC retransmission algorithm.The retransmission algorithm determines whether the data frame should be retransmitted by comparing the value of the final decoded reliable results,Meanwhile, set the maximum times of retransmission, when a frame of data reaches the maximum number of retransmissions, compare the results of multiple retransmissions, will obtain a new final output of the decoding witch greater accuracy, Greatly reduces the bit error rate of Turbo codes in decoding result.(4)In order to verify PE-CRC iterative algorithm and PE-CRC stop retransmission performance of the algorithm in Matlab simulation environment, one iteration stops for PE-CRC CRC algorithm and the traditional iterative stopping criterion compares the performance of experiments show at high SNR, PE-CRC iteration stops CRC algorithm compared to conventional iterative stopping criteria, fewer iterations, and in the low SNR, the accuracy of PE-CRC decoding algorithm with respect to CRC Standards increased slightly. On the other hand, through the PE-CRC retransmission algorithm simulation results show that in the same time with PE-CRC algorithm iterations stop condition, PE-CRC retransmission algorithm simulation results, the bit error rate is significantly lower than the unopened retransmission algorithm simulation results, thus proving PE-CRC algorithm can really stop the iterative improvement of Turbo decoding accuracy in low SNR.