Implementation Of Link Adaptive Technology On MAC Layer In LTE System

It is the need of market development and social economy to provide userscommunications services with higher rates, greater bandwidth. The wideband wirelessaccess technologies and mobile communications industry are continually becomingintegrated and developed, the result is mobile communications industry becomes widelyand widedband wireless access technologies becomes mobile. In response to these needs,3GPP officially launched the Long Term Evolution （LTE） of mobile communicationtechnologies project in March2005. As the changes in wireless channel character, how tomaximize the data transfer rates in limited bandwidth, how to make effective use of thechannel changes, and how to maximize the frequency efficiency, become the key point ofmobile communication research. Link adaptive technique has been considered as the keytechnologies of LTE because of its strong advantage in improving the frequency efficiencyand data transfer rates.This paper studied the link adaptive technique in TD-LTE system and itsimplementations in MAC layer. The specific work as follows:1. Firstly, the origin, development and system architecture of LTE was introduced, anddiscussed its protocol, after that link adaptive technology as the main research of this paperwas analyzed. In order to propose a new algorithm and improve the current technology, theactualities of Hybrid Automatic Repeat request （HARQ） and Adaptive Modulation andCoding （AMC） research was expatiated.2. The basic principle and TD-LTE protocol of HARQ was researched, then especiallyanalyzed the design of uplink and downlink HARQ to introduce the scheme of HARQ inTD-LTE system, and analyzed its feasibility and superiority.3. The basic principle and TD-LTE protocol of AMC was researched. And in order toachieve the adaption of modulation and coding, the Dynamic Offset AMC algorithm wasproposed. Then a scheme of AMC was designed, which can interact with the HARQ and dynamic choose the right MCS for LTE system.4. Finally, simulated the scheme and algorithm proposed in this paper, the resultshows that Dynamic Offset AMC can improve the transmission efficiency and reduce theblock error rate. Then a real experimental environment was build, the practical applicationin LTE BBU tell us that the scheme and algorithm proposed in this paper are very useful inprojects, and the system downlink transmission rate can achieve a stable68Mb/s.