Harq Combination Of Decoding Algorithm And Its Application In Sess System

In order to improve the transmission reliability of data and image in 3G, thechannel coding technology-HARQ combined by ARQ and FEC is often adaptedwidely. HARQ is the core to realize the HSDPA proposed by 3GPP.This paper provides 3 mechanisms of HARQ and 3 ARQ retransmissionprotocols. The characteristic of 3rd HARQ in one channel stop and wait protocol isanalysed on emphases. This paper focuses on the discussion of the combiningdecoding algorithm. A modified combining decoding algorithm over chase algorithmis proposed. Computer simulations show that the HARQ with modified combiningdecoding algorithm is obviously superior with the HARQ with traditional chasealgorithm in term of the number of decoding and the throughput of system. In a rangeof SNR, modified combining decoding algorithm can obtain 1dB gain.The basic characteristic of self-encoded spread spectrum (SESS) system isanalysed in this paper. Aiming at its special characteristic, we analyse theanti-interference performance and proposed 3 models with error correct coding.Computer simulations show that the BER can be decreased in the system with Turbocoding. And we found that BER of SESS is near to the performance of error correctcoding while SNR is above a particular value. Because of the self-interference inSESS, there is a threshold in the SESS_Turbo system. Compared with other 2 models,modified external model has the lower threshold value. Introduce HARQ mechanisminto SESS system, which decrease BER and the threshold. 5dB gain can be obtainedwith 2 retransmissions.