Multiple Antennae Interference Suppression With Cell Coordination

Inter user interference and inter cell interference have long been bottleneck to system capacity’s enhancement, especially for multi-antenna LTE-A system. Since each antenna is regarded as a resource of interference, cell-edge users will suffer from serious inter cell interference. Their throughput would be hard to satisfy high-speed service. Meanwhile, the hardware of terminals limits the computation complexity and makes it hard to implement complex detection algorithm dealing with interference.The birth of Multiple Input and Multiple Output (MIMO) precoding provides solution to suppressing interference. What the precoding does is force zero scheme or judging minimum mean square at the receiver thus isolating useful signals. But traditional precoding schemes could only suppress interference among streams of single user or interference inside the cell. To deal with inter cell interference, it needs combing all antennae of different cells to one array, namely, transferring interference channel to broadcasting channel to nullify interference completely. However, these joint precoding schemes require center eNB high computing ability and produce heavy interact burden for the network. The trend of large-scale wireless network makes them unrealistic. So coordinated scheduling comes to birth. It needs no data interaction and eases burden but cannot nullify interference completely.In order to solve these problems above, nowadays’studies of special interference suppression includes Block Diagonalization(BD), max-SLNR precoding scheme, clustering and so on. They consider inter-user interference and inter-cell interference at the same level and base on either nullifying interference completely or transmitting user data. In fact, in a multi-antennae system, the special degree of freedom (DoF) used for suppressing interference or transmitting data is limited by number of antennae. For some users, the gain from suppressing interference is no more than transmitting data; and inter user interference is no more serious than inter cell interference.Thus, if DoF can be used more reasonably, there would be more room for enhancing throughput. So this thesis puts forward an interference suppression algorithm based on usage of DoF. It trades off between suppressing interference and transmitting data as well as inter user interference and inter cell interference. It also overcomes interact burden and DoF limitation from antennae. The algorithm achieves its goal by selecting different precoding schemes for different users and gets solution through modified Hungarian algorithm. Simulation testifies its performance by comparing it with other traditional precoding schemes and the algorithm of scarifying DoF.