Research On LTE-A System Coverage Enhancement And Its Key Technology

Due to the ability of improving the peak data rate and cell edge user performance, coverage enhancement techniques are concerned widely in the field of academic and industry. In LTE-A system, because of the poor channel condition and power limitation of cell edge user, there are problems in completion of normal communication, so that the uplink coverage is limited. With the rapid development of mobile Internet technology, the demand for data service is growing fast in downlink, and then downlink peak data rate of existing networks can not meet the need of users, so that the downlink coverage quality is limited. So how to improve the coverage performance of LTE-A system, is worthy of further research.The research was supported by the Enterprise cooperation project "Research on LTE coverage and coverage enhancement technology".This thesis focused on the target of improving coverage performance, researched higher order modulation techniques to improve the downlink coverage quality and enhanced TTI bundling techniques to expand the uplink coverage.Firstly, this thesis introduced the classic coverage enhancement techniques in3G and4G systems, and summarized coverage enhancement techniques related to the goals of improving coverage quality and expanding coverage. Secondly, higher order modulation techniques were researched in this paper, including coverage quality evalution in different modulations, EVM expression derivation under three different RF losses, and influence analysis of modulation order on EVM. In addition, this paper evaluated the required EVM under higher order modulation by the method of performance simulation and constant throughput. For the research of enhanced TTI bundling techniques, this thesis evaluated coverage quality of different LTE-A uplink physical channels, identified the most seriously coverage limited channel, and did the coverage performance evaluation of TTI bundling technique in PUSCH VoIP and PUSCH Medium data rate. Moreover, this thesis designed two different enhanced TTI bundling transmission schemes, the corresponding traffic process and scheduling mode, as well as evaluted coverage performance of this two schemes. Simulation results show that, higher order modulation and enhanced TTI bundling techniques can effectively improve the coverage quality and expand coverage.