Code Combining And Turbo-ARQ Techniques

FEC maintains a steady efficiency while ARQ assures high reliability for transmission.As turbo code has an error correcting performance close to Shannon theory limit and its iterative decoding scheme,turbo code hybrid ARQ(TC-HARQ) is an important strategy in high data rate communications.In HARQ system, Without combining previous packets,if the entire erroneous packet is discarded and all the hopeis placed on the retransmission,the throughput performance will decrease dramatically.In this thesis,we mainly study on the TC-HARQ.The combining technique based on the iterative decoding scheme is thoroughly studied; also,we combine the retransmission stratagem and the iterative decoding scheme to develop better TC-HARQ stratage.Two types of parallel decoding scheme are introduced firstly,and we simulate the systems adopting different schemes respectively.Simulation results shows that the performance of the parallel decoding scheme based on sub-block trillis terminated to zero is better than the traditional parallel decoding scheme.The former could improve the "sub-block affect".Next,we research on the code combining techniques,mainly focus on the iterative combining technique(IC).The performances of the key parameters of iterative combining are evaluated.Furthermore,like the HARQ combine FEC and ARQ to get better performance,we utilize the advantage of IC and Chase combining technique to develop two hybrid combining techniques,the thesis shows that the hybrid combining technique could improve performanve in terms of the convergence speed with negligible additional decoder complexity.Furthmore,the performance in terms of SNR Gain of Tpye-Ⅰand Typr-ⅡHARQ is compared,the result shows that Tpye-Ⅰhas the comparable performance with Tpye-Ⅱ.Besides,getting the idea from the iterative combining,we propose a new TC-HARQ stratage based on the iterative scheme that different transmission use different number of SISO decoder.Simulation shows that the new TC-HARQ has good BER performance and suit to be as the complementarity of RCPT.Followly; the thesis introduces the parallel decoding scheme to the TC-HARQ,joined with the segment-block retransmission scheme,we propose another new segment-block retransmission TC-HARQ based on parallel decoding stratagem.Simulaton also shows that a significant improvement in throughput efficiency compared with the type-ⅠHARQ is obtained.