Research On Position Assisted Handover Schemes For Lte-a Network Under High Mobility Senarios

How to provide communication services with a higher rate and better quality for users at a speed as high as350km/h, has become an important research directions in the field of mobile communications. LTE-A system, which has flattened IP network structure, up to1Gbps downlink and500Mbps uplink peak rate, and shorter control plane latency and user plane latency, has shown great prospects in the high-speed railway communication system.Cross-cell Handover which is an important part of the mobility management in the LTE-A system, maintains the continuity of communication services, avoiding the communication interruption because of the fast moving between cells. In high mobility scenario, inter-carrier interference caused by severe Doppler effect can affect the transmission of signaling messages; because of the very high speed of users, the overlapping area between adjacent cells could be passed in a really short time, which means the handover delay should be very small; In order to avoid frequent handover, cells become larger which leads to deterioration of the signal quality at the cell edge. In addition, users of high-speed trains will suffer carriage penetration loss and signaling storm caused by large number of users triggering handover at the same time. This article will research position assisted handover techniques for LTE-A in high mobility scenarios, several fast and reliable handover schemes are proposed here.In this thesis, a simple overview of LTE-A system and its handover mechanism is presented first, then the impact of the high mobility on handover scheme for LTE-A are analyzed. Combined with positioning technology, position assisted handover schemes are studied, four different handover algorithms are proposed. Scheme A is designed to reduce handover delay by making handover preparation before handover starts. Scheme B aims at reducing unnecessary handovers and improving handover success rate, by calculating the geographically best target handover cell, thus making it easier for UE to access to the target cell. Scheme C and Scheme D propose new handover triggering algorithms to replace the original LTE-A event A3criterion. A system level simulation is conducted to evaluate the performance of these four schemes. Simulation results show that, scheme A could reduce inter-site handover delay by50ms while scheme B could cut down nearly50%of all handovers when TTT=0ms and improve success rate when TTT is higher. Scheme C and Scheme D could achieve high handover success rate in appropriate parameter settings.