HARQ Algorithm Research And Simulation Based On 3GPP LTE System

The 3GPP LTE(Long Term Evolution) project is one of the most important high technologies launched by 3GPP(the Third Generation Partner Project) in recent years. The project was implemented in order to compete with WiMAX(Worldwide Interoperability for Microwave Access),Wi2Fi and other emerging wireless broadband technology and improve its competitiveness in the emerging 3G broadband wireless access market. It is long term evolution on the UMTS(Universal Mobile Telecommunications System) technology in order to achieve 3G technology to smooth the transition of B3G and 4G.3GPP LTE is an improvemental project on the UTRA and UTRAN (Universal Terrestrial Radio Access Network).Its goal is to higher data rates,lower latency,improved system capacity,broader coverage,and lower costs.Hybrid ARQ(Hybrid Automatic Repeat Request,HARQ)technology is the most effective error control technology in order to ensure reliabal data transmission.IIt is essential to the mobile broadband system which is featured as high-speed data rate,high quality of service (Quality of Service,QoS)guarantees and high reliability.In same,HARQ is one of the key technologies in 3GPP LTE system.Based on 3 GPP LTE system and focusing on HARQ, the performance of HARQ and the achievement of the program are addressed and researched in depth along from basic research to explore innovative ideas.This paper preferred a comprehensive analysis on the technical characteristics of critical technologies in 3GPP LTE system. Around its core technology HARQ, the combination of decoding algorithm for packet retransmission is fully studied in depth. The performance of Chase combining and IR(Incremental Redundancy) were compared and the results showed that IR is better than Chase combining, the performance gain depends on the modulation size and coding rate. Based on these researches, this paper presents an improved combining decoding algorithm of HARQ based on 3 GPP LTE system. The computer simulations show that the HARQ with the new combining decoding algorithm is obviously superior to the HARQ without the combining algorithm and also a rather advantage over the HARQ with traditional Chase combining decoding algorithm in terms of the number of retransmissions and the throughput of system.In further, This paper discussed encoding schemes of HARQ and the limited-times packet re-transmission protocol. A detailed analysis of performance and explanation of operating principles were delivered. The concrete implementation steps of Turbo code compiler was presented in the improving program.And further detailed discussion and calculation of the implementation of three type of HARQ were given in the improving program. At last, an improved HARQ package retransmission mechanism was proposed for the 3GPP LTE system. The simulation shows that the improved mechanism assumes a better delay performance compared to the traditional programs when the SNR is small.