Study On Interference Mitigation Scheme For TD-LTE On Licensed And Unlicensed Band

With TD-LTE being commercially deployed gradually,how to mitigate the interference in and out of the TD-LTE system is becoming more and more important.Seven DL/UL configurations are defined in long term evolution(LTE)TDD systems.Dynamic DL/UL reconfiguration enables flexible DL/UL reconfiguration according to the traffic demand.However,transmis-sion in opposite directions in neighboring cells,which is caused by the cells'frequent DL/UL reconfiguration,will significantly increase cross-subframe co-channel interference.This article introduced a cell clustering interference mitigation(CCIM)scheme,in this scheme,a cluster can compromise one or more cells.By choosing an appropriate threshold,excellent isolation can be achieved among cell clusters.The base stations of the network optimize and reconfigure the DL/UL configurations on the basis of a cluster.Transmission directions in cells belonging to different clusters can be opposite in a sub-frame.However,this cell clustering scheme has its drawbacks.In isolated cell scenario,each cell is able to adjust DL/UL configuration freely according to the traffic.Things become different when cells are densely deployed,as the size of cluster increases,the complexity of selecting appropriate DL/UL con-figuration increases exponentially.In other words,the more cells a cluster comprises,the less throughput gain dynamic configuration achieves.In this paper,we propose an enhanced cell clustering interference mitigation(eCCIM)scheme to increase the efficiency of dynamic configuration and reduce CCI at the same time.Finally scheduling and power adjustment are conducted on the interference isolation area.System level simulations show that the proposed scheme yields significant throughput gain over the conventional cell cluster-ing interference mitigation scheme.On the other hand,since licensed band is limited and crucial for mobile operators,mobile operators are considering deploying TD-LTE on unlicensed band.However,Wi-Fi" is deployed on unlicensed band too.The key point of deploying TD-LTE on unlicensed band is to ensure the harmonious coexist-ence with Wi-Fi system on the basis of mitigating interference between these two systems.This article designed an interference mitigation scheme based on frame based clear channel assessment and load based clear channel assess-ment,simulation results reveal that the proposed interference mitigation scheme greatly improved the throughput of Wi-Fi at the sacrrifice of slightly reducing the throughput of TD-LTE in coexistence system,guaranteeing the performance of the whole coexistence system.