Design And Implementation Of Dynamic TDD And Interference Coordination Scheme In LAA System

In recent years,due to the rapid development of mobile internet and the increasing popularity of intelligent terminals,the mobile communication traffic shows a blowout increase.Although the wireless communication technology develops quickly,the spectrum resources are limited and LTE licensed spectrum has already been very crowded.Facing with the problem of spectrum tensions,using the unlicensed spectrum to provide users with data services with the help of LTE licensed spectrum is gradually becoming an effective solution.When the LTE system is deployed on the unlicensed spectrum,the listen before talk channel detection mechanism can be employed to ensure the harmonious coexistence between LTE and other access technologies.According to the uplink and downlink traffic,the traditional TD-LTE system can use different uplink and downlink subframe configuration because of the unfixed uplink and downlink channels.Therefore,this is not only very suitable for asymmetric communication services in the heterogeneous network scenarios,but also provides a good condition for the use of dynamic TDD technology.The dynamic TDD technology in heterogeneous networks can improve the system's throughput.However,the cross-subframe interference is also brought among the base stations,thus affecting the system's performance.Aiming at the problems of dynamic subframe configuration and cross-subframe interference on unlicensed bands,the thesis mainly researches the following two aspects:First,the use of dynamic TDD technology in the LTE licensed bands is limited by the signaling control and other issues,then only the dynamic switching among the traditional seven subframes configuration is realized.It is not necessary to consider the signaling control and other issues when LTE system is deployed in the unlicensed bands,which can achieve a complete dynamic subframe configuration.According to the characteristics of unlicensed bands,two new dynamic subframe configuration algorithms are researched.The simulation results show that the UE uplink average throughput of the dynamic subframe configuration scheme is about 1.8 times higher than the static subframe configuration scheme,the UE downlink average throughput also increases by nearly 19.02% in the low load condition.In general,the dynamic subframe configuration scheme can effectively improve the system's performance.Second,the use of dynamic TDD technology also brings serious cross-subframe interference among the base stations.In order to reduce the influence of cross-subframe interference,an interference coordination scheme based on hybrid dynamic clustering algorithm is designed by analyzing the source of cross-subframe interference and the system's traffic.Via verification on LAA system level simulation platform,the UE uplink average throughput of the hybrid dynamic clustering scheme increases by nearly 16.93% and the UE downlink average throughput increases about 34.33% in the medium load condition compared with the traditional static clustering scheme.In general,the hybrid dynamic clustering algorithm has better performance than traditional static clustering algorithm and it can also effectively reduce the cross-subframe interference.