Hybrid Automatic Retransmission Research In Mobile Communication Technology

The rapid development of network technology, communication technology and microelectronic technology has offered a very wide space for media applications of mobile communications. at the same time, mobile communication has not content with the basic functions of single voice call, text-based transmission and data download, meanwhile streaming media, with the advantages of its continuous, real-time nature and timing is being widely applied to various fields of society even to the people's daily life. Due to noise, multipath fading and interference and other causes of high error and high packet loss, the error control to ensure data transmission quality are especially important. Hybrid ARQ is an excellent error control technology, and design a real-time correction capability and a good hybrid automatic retransmission mechanism is the theme of this paper.This paper firstly introduces the origin of hybrid automatic retransmission. Automatic retransmission request (ARQ) and forward error correction ((FEC) is the main technology to address transmission issues. Several traditional implementation of automatic retransmission request commonly used in a variety of mechanisms and current methods of channel coding are described in detailed.Since both of the two technologies have their strengths and weaknesses, people put forward the advantages of both rolled into one hybrid automatic repeat reques. Then this paper details the three basic types of hybrid automatic retransmission mechanism and a nearly constant transmission delay of the hybrid automatic retransmission mechanism to achieve the principle and the advantages as well as disadvantages in order to improve the program for the final preparation.In this paper, the RTP/RTCP protocol is improved based on an analysis of shortcomings of the two protocols TCP and UDP and the specific mobile communication applications of streaming media. Data between the transmitter and receiver must comply with the relevant transmission protocol; Real-time Transport Protocol (RTP) and Real-time Transport Control Protocol (RTCP) are the set for IETF multimedia data stream transfer protocol, in which the former is responsible for data transmission; while the latter guarantees the reliable transmission of data. However they only provide a framework for an agreement, and specific applications must be added as needed or excision. Finally, in the setting of existence of additive white Gaussian noise (AWGN) channel error packet loss, the hybrid ARQ type II technique recommended by the third generation mobile communication protocol will be used to compare the improved version of the protocol and TCP protocol in simulation which shows to the performance advantages of the improved protocol.The technique of nearly constant transmission delay for the hybrid automatic repeat have been improved and the adaptive HARQ technology based on RTP/RTCP protocol are proposed. Whether retransmission is needed is determined by report from the sender and receiver; The adaptive coding rate are used to distinguish the reason for retransmission between packet loss and decoding failure. It has been shown that the proposed method has effectively improved the utilization of feedback to reduce the number of retransmission and can ensure the correct information at a higher transmission rate by selecting the appropriate redundancy rate.