The Research Of Hybrid Automatic Request Algorithm Based On Packet Loss Rate Prediction

In the wireless communication environment, wireless channel is unstable because of factors of noise interference, multipath effect, shadow effects, the energy of the signal will decreases with the increase of the propagation distance, make the transmission error rate is high, thus the data transmission quality is affected. Error control is a common means to improve the reliability of wireless transmission. Usually error control algorithm has three types of forward error correction(FEC), automatic repeat request(ARQ) and hybrid automatic repeat request(HARQ). FEC algorithm usually adopts the way of channel coding, redundant symbols are added to the information to be transmitted to correct the error. ARQ algorithm through the error detection code encoding the information to be transmitted, the receiving end determines whether the received information of the presence of errors, if an error exists again transfer the data packet. HARQ algorithm is a combination of FEC algorithm and ARQ algorithm, not only has the error correction ability also has the ability of retransmission.HARQ algorithm is an excellent error control mode, it is also a hot research topic in wireless communication field at home and abroad.This paper first analyzes the research status at home and abroad, and studies the basic principle of FEC, ARQ and HARQ algorithm and the realization process, points out the shortcomings existing in each algorithm in wireless communication. Analyzes the classification of HARQ algorithm and the realization principle of HARQ algorithm.Then, describes the framework of hidden Markov model(HMM), Analyzes the problems that can be solved by HMM in the practical application and study the bit level model and packet model in the wireless channel. Then, put forward a prediction model of packet loss rate based on HMM.This paper presents an adaptive HARQ algorithm which RS encoding decision made by the trend of packet loss rate. On the basis of packet loss rate prediction of HMM, RS code encoding scheme is dynamically adjusted by the change of packet loss rate, realize the HMM and the channel state adaptive matching.Finally, the simulation experiments of the improved HARQ algorithm and three kinds of traditional HARQ algorithm were performed and the results were analyzed, the feasibility of the HARQ algorithm based on prediction is verified.