Study Of Mobile Relay Based On LTE-Advanced

Under the promotion of broadband mobile data services and smart phones, operators all over the world have picked up the pace of LTE network deployment in succession during the past several years. As the smooth evolution of LTE, LTE-Advanced (LTE-A) is able to provide higher peak rate, less control and user plane latency as well as better mobility support. Considered as the top preferred technology of4G, LTE-A has introduced several key technical features, such as carrier aggregation, enhanced MIMO, relay and coordinated multi-point processing(CoMP), to satisfy the higher requirement of International Mobile Telecommunications Advanced (IMT-A) and future wireless mobile communication.In3GPP, high speed railway (HSR) scenario was agreed as the main study scenario of Mobile Relay for LTE-A in Rel.11. Generally, user under this condition will confront much more problems than that in the traditional cellular network with normal speed, such as over-frequent handover, Doppler spread and radio link abrupt changes. Meanwhile active users in the train are more crowded and static than in other scenarios. They are more likely to enjoy higher data rate services to kill time, so it’s necessary to improve the cell throughput. When the train travels along the railway with very high speed (300-350km/h), there will be excessive frequent handovers happening in a relative short period. UE has very limited time(<2s) to measure and execute one handover procedure, which typically includes cell measurement and report, RRC connection reconfiguration, random access in new cell when passing the overlap area between two adjacent cells. Because each mobile station in the same carriage performs handover almost at the same time, this will certainly aggravate system signaling burden, cause channel congestion and result in handover failure. So how to ensure handover successful rate of HSR becomes a remarkable issue.Relay Station (RS) can be regarded as a key node in the network and it is intelligently capable of relaying data between the base station (eNB) and user equipment (UE) via air interface. It possesses common features like normal relay and can improve user’s SINR in the train. Meanwhile, mobile relay also has group mobility management function and executes group handover procedure instead of each UE in the high speed train. This can avoid signaling block and decrease handover failure rate. On the other hand, if mobile relay equips with distributed antenna, it can realize diversity function in the non-handover state to help improve system capacity and achieve coordination of distributed antenna to assist to complete the handover in the handover state to increase handover successful rate. In the aspect of scheduling for mobile relay, if we adopt optimized PF algorithm based on Diversity Degree of user’s SINR, mobile relay can guarantee the fairness between all the users and improve throughput of the users in the train. So it can make user experience better.This paper introduces the development status of LTE-ADVANCED, technique general situation, the problem of scheduling and resource allocation of mobile relay and the optimized handover algorithm under mobile relay scene. Besides, I have done a lot of work in the simulation. This paper has studied handover probability, handover failure rate, throughput of train users and system, radio link failure rate and some other technical indicators to confirm the advantages of my model and algorithm.At last, it’s the conclusion of this paper and expectation of future work.