Handover Algorithms For LTE-Advanced Relay Wireless Networks

The future wireless communication network has more and more requirements about high-speed, wide coverage and large-capacity wireless service. With the constantly upgrade of the wireless demand,3G network gradually can’t meet the needs of communication. So the next generation wireless communication network standard--IMT-Advanced gradually is put on the agenda. IMT-A network can offer high quality Voice service and multimedia service, 1Gb/s speed for low-speed users. As an important part of 4G network standardization, Long-term evolution advanced--LTE-A introduce relay technology which as one of the most important technology in standardization to expand coverage, improve spectrum efficiency and guarantee the edge the use of user experience. After introducing relay in cellular network, the network structure has taken a great change. Wireless communication handover scene and category become more complex. The traditional handover scheme has not completely suitable for relay cellular network. So designig a more reasonable and optimization handover scheme, improving the reliability and effectiveness of the handover, and promoting efficiency of the resources in relay-base station (Backhaul-Link) have become a research focus.This paper concentrates on the key handover technology in next generation relay wireless network. Including the research on wireless relay technology in next generation network, traditional handover algorithm in relay network, and the new Type I relay handover scheme in the LTE-A relay cellular network.In network architecture, this paper analyzes the functions and features of the relay network and relay’s advantage in performance, and the problem when executing handover in wireless relay network. The increase of node increased the frequency of handover trigger, multi-hop structure introduced new handover category, and significant increased the time delay and signaling cost during handover. So we should consider multi-objective handover decision. In order to improve efficiency of frequency of backhaul link, decision reasonable signaling procedure in handover process, and design appropriate S1/X2 handover process to ensure the efficiency and integrity of handover.In view of system level performance, design multi-object handover algorithm with the consideration of the signaling cost, throughput, time delay and the motion of the user. And according to the characteristics of the different service types, adjust the weight of different object in multi-objective handover decision function when different service trigger handover, then finish the handover. With the analysis of Matlab simulation, the theoretical analysis and simulation results both indicate that the multi-object handover algorithm based on different service type can better satisfy different service, guarantee user’s QoS. And then in order to improve the performance of backhaul link, design handover signaling report scheme which reporting the average large scale decline in all subchannels and the sequence number of limited best subchannels, to replace the report all the sub-carrier state information of each sub-carrier in pilot carrier. Effectively decrease the signaling cost in backhaul link during handover. And the handover scheme combines handover decision process and access subcarrier allocation, which guarantee the reliability of handover. At last according to the character of LTE-A network, the paper introduces optimized handover process, make data packets in relay two hop interface (Un and Uu interface) use the same PDCP code number, to avoid relay data redundant when relay handover suddenly happened. And design a LTE-A S1/X2 relay handover process which set S1/X2 handover decision entity at eNB and give a concrete relay handover process.In the end of paper, summarizes the full text paper and points out the future research direction.