Research On Enhanced TDD-LTE/LTE-A UL-DL Interference Mitigation And Traffic Adaptation

In wireless communication system, Time Division Duplex(TDD) method doesn’t need pairs of spectrum resources, thus enable flexible system deployment. Currently TDD-LTE/LTE-A can provide7configurations of asymmetric uplink/downlink (UL/DL) resources which offer40to90percent DL subframes to adapt to traffic fluctuation flexibly. The feature of flexible adaptation to traffic is rather desirable in current and future wireless heterogeneous communication system for the spring up of UL/DL asymmetric multimedia traffic.In a dynamic TDD system, a LPN, or a cell, can choose UL/DL configurations dynamically to adapt to the fluctuation of UL/DL traffic load, thus can expect higher system throughput and lower network energy consumption. But the introduce of dynamic TDD UL/DL configuration will bring extra interference and cause HARQ timing disorder. This dissertation is based on dynamic TDD systems and has three research points which can be summarized as follows:While dynamic UL/DL configuration can flexibly adapt to the traffic fluctuation, it also brings UL/DL cross-subframe interference between cells, thus impairs the system throughput improvement. This dissertation proposes an interference mitigation and traffic adaptation scheme, which is easy for deployment. And the system simulation proves that the proposed scheme can decrease the cross-subframe interference and, at the meantime, maintain the flexibility of traffic adaptation, thus ensure the system throughput improvementMeanwhile, UL/DL reconfiguration of a certain cell will cause disorder in HARQ timing, which means some HARQ processes are not able to get corresponding feedback or scheduling resources. This dissertation designs UL/DL HARQ timing for dynamic TDD system, which is low in complexity and can effectively solve the HARQ conflicts.Last, power consumption is investigated in dynamic TDD LTE/LTE-A system. Based on system power consumption model and convex optimization theory, we propose a joint optimization scheme of UL/DL resource, subcarrier and power allocation. And the performance gain on power consumption reduce of dynamic TDD system is verified by the numerical simulation.