Research On Cell Search And Random Access In LTE-A Heterogeneous Networks

In order to meet the rising market demand,3 GPP and other international standardization organizations actively promote the standardization of wireless communication system.Heterogeneous deployment is one of the important research topics in 3 GPP LTE and LTE-A standardizations.Typical heterogeneous deployment scenario is small cell deployed within the macro-cell coverage.D2D,as well as V2V,is important auxiliary communication technology in LTE-A heterogeneous network.The new network deployment and communication technology make the network architecture more complex,which introduce challenges for the network access procedure,such as,cell search and random access.Considering cell search and random access in LTE-A heterogeneous network,the main research areas of this thesis are summarized as follows:In small cell dense deployment scenario,small cell On/Off induces dynamic change of neighbor cell relationship.The method of dynamic PCI allocation is proposed,which is applicable to the small cell On/Off scenario.Within the small cell cluster,PCI is allocated to small cells dynamically to support cell discovery for off-state small cell and enhance the performance of cell search and measurement for on-state small cell.Simulation results show that compared to fixed configuration,the proposed method can effectively improve the performance of cell search and measurement for on-state small cell.Considering the end-to-end delay and reliability requirements of V2V communication,a method of random access procedure optimization is proposed based on priority.The vehicle transmits random access request taking advantage of dedicated random access resource.Then the optimized initial random access procedure and optimized mechanism for access failure are triggered.The proposed random access is combined with resource allocation for V2V,thus the resource allocation delay of V2V is also decreased.Meanwhile,the vehicle failed in initial random access can access the network by further interaction with the eNB.Therefore,the access delay is reduced and the access success rate is increased.Considering D2D communication in multi-operator scenario with shared spectrum,a mechanism for inter-operator D2D-relay discovery and access is proposed in this thesis based on cell search procedure.In this mechanism,UE takes advantage of Relay-UE activation process and Remote-UE activation process to support inter-operator D2D-relay device discovery and access.Relay-UE broadcasts discovery signal and monitor access request from Remote-UE on the shared spectrum.Remote-UE detects discovery signal broadcast by Relay-UE to obtain the frame timing and monitor timing of Relay-UE,and then sends access request to the Relay-UE,establishing D2D connection.With limited assistance from eNB and a little signaling,this mechanism achieves inter-operator D2D connection establishment.In summary,this thesis studies three research points about cell search and random access under LTE-A heterogeneous network.Corresponding optimization methods and solutions are proposed respectively,with part of proposed methods verified through simulation.