Research On Anti-interference Of LTE System Based On Dynamic TDD Technology

With the popularity of smart mobile devices and the exploding of multimedia data traffic,user demand is increasing at an exponential rate.Compared with FDD,the TDD system transmits the uplink and downlink data based on the different time slot resources of same channel and not need to occupy on the symmetric spectrum resource.When the spectrum resource is tight,it is more advantageous.Dynamic TDD could improve the system capacity,in which uplink and downlink subframes can be dynamically configured in small cells to adapt their communication service in either direction.However,different uplink and downlink directions for the same subframe in adjacent cells will result in new destructive interference components,i.e.,eNodeB-to-eNodeB and UE-to-UE,with levels that can significantly differ from one subframe to another.Therefore,how to reduce the cross-link interference and improve the efficiency of spectrum utilization has become an urgent problem in TD-LTE system.Firstly,this thesis introduces the basic knowledge of TD-LTE system and describes the dynamic TDD technology and the slot cross interference in detail.Then,we will study the anti-jamming schemes based on cell clustering technology,and propose a simplified complexity method to solve the optimization problem when to get the results of the clustering.After compared with a predefined threshold,the cluster set will be obtained.From the results of the simulation,the average cell throughput and edge user throughput are promoted.To order to reduce the interference between the base stations in the multiple outdoor co-channel pico-cells,this thesis will propose a power control scheme in which users adjust the transmit power according to different interference levels.In particular,we consider the geometric location information and the subframe set selection process of interfering cells to measure the interference level.Then,it determines the number of adjacent interference cells by the reasonable rules and sets the threshold to isolate interference region.The power control period follows the uplink/downlink reconfiguration period,e.g.10ms,200ms,640ms,etc.The performance of the proposed scheme was evaluated through system level simulation and it is shown that the scheme can achieve preferable improvement in terms of average uplink throughput and edge user throughput compared with the original scheme without power control.Also,the UE-to-UE interference is not worse when the UE transmit power become higher.