Research On Interference Management Technologies For LTE System

The wide deployment of LTE system brings new interference problem to wireless communication, including not only inter-cell interference within the LTE system, but also inter-system interference when it is co-existent with other wireless communication systems. All these interference degrades the performance of LTE system directly, as well as that of other co-existent system. How to solve the interference problem affects the further development of LTE system.In this thesis, we investigate on the interference management technologies for LTE systems. Our research focuses on three parts, i.e., the interference coordination in a LTE system, the interference management in a MCP (Multi-cell Cooperation Processing) network, and the interference management when a TD-LTE system is co-existent with a TD-SCDMA system. The main contributions of this thesis can be summarized as:Firstly, we analyse the interference types and their formation reasons in LTE systems, especially analyse the inter-cell interference in LTE systems and the cross-slot interference, which only appears in TD-LTE systems. Via the system simulation, we get the performance degradation level of TD-LTE system, which is caused by cross-slot interference. Some corresponding curves of system throughput based on different scheduling schemes are also presented.Secondly, based on the summary of existing interference coordination technologies, we proposed a new MCP interference coordination scheme which can be used in FFR (Fractional Frequency Reuse) network. The new method uses full-coorperation mode, and focuses on the selection of coorperative user and coorperative base sation. Simulaton results show that the proposed method improves the system throughput, and promotes the performance of cell edge users siganificantly.Thirdly, study on the users'selection and the power allocation problem in the multiple cell processing network. Based on the cooperative resource allocation network, we proposed a new resource allocation scheme with QoS guaranteed, including users'selection and power allocation. Simulation results show that the new scheme improves system performance, ensures user's QoS and reduces outage.Forthly, different types of inter-system interference in the co-existance scenario of TD-LTE system and TD-SCDMA system are analysised by using MCL method. The isolation requirement of different interference is given out, and isolation distance with different antenna installation method is also given out.Fifthly, co-existence interference between TD-LTE system and TD-SCDMA sysem is studied by using system simulation method. The relative value of performance decrease of both of the systems which is caused by adjacent channel interference between TD-LTE BS and TD-SCDMA BS is obtained.Sixthly, the inter-system interference between a TD-LTE system and a TD-SCDMA system is studied in a mathematic optimization problem with constraint, and the optimal solution is derived by using a convex optimization method. A new frequency allocating method of LTE system which suits for co-existance scenario is proposed. The proposed method reduces the inter-system interference and improves the system performance. The simulation results show that the proposed method improves the thoughput of LTE system and reduces the outage of TD-SCDMA system simutaneously.