Clustering-based co-tier interference coordination in dense small cell networks

Along with the exponential growth of mobile data traffic over the past few years, dense small cell networks are considered an attractive solution to cope with the mobile traffic demand. However, users of small cells in dense environment are exposed to serious co-tier interference problem and users at the edge of small cells have worse performance especially. In order to improve the performance of redefined edge users and maintain the throughput of the network, we propose a clustering-based co-tier interference coordination (CCIC) scheme on the downlink (DL) side to mitigate co-tier interference to edge users. Firstly, small cells are clustered based on the graph coloring algorithm (GCA). Secondly, we schedule frequency resources into two bands as well as group users into two categories. Different kinds of bands are assigned to corresponding users. Accordingly we reduce power on a band defined as center band to mitigate interference to edge users. Then a utility function is proposed to find the optimal transmission power of each small cell base station (SBS) on center band. Finally, differential evolution (DE) algorithm is applied to obtain the optimal transmission power. System level simulation results show that our proposed scheme can greatly improve the edge user throughput with slightly sacrificing the overall throughput. Meanwhile, it can improve the network energy efficiency (EE) dramatically.