Interference Coordination Oriented User Association Scheme in Cellular Relay Networks

Heterogeneous cellular networks (HCNs) will be the typical network structure for future mobile networks. Relay nodes (RNs), as one type of low power nodes in the HCNs, can be deployed to increase cell coverage and improve cell-edge user throughput. Since RNs may be densely deployed in hot traffic zones, the co-channel interference (CCI) is more serious and complex than that in the conventional homogeneous networks. In this paper, we propose an interference coordination oriented user association scheme in cellular relay networks for CCI coordination. Firstly, we define a relay interference matrix (RIM), which is used to decrease the interference-related information feedback overhead. Then we define a function named as interference duration density (IDD), which indicates the interference probability from a RN to a user equipment in both the time and frequency domains. Specifically, based on RIM and IDD, the proposed user association scheme can reduce the probability of the CCI from interfering RNs by adjusting the number of users associated with such interfering RNs. By doing so, the CCI among RNs can be mitigated and the system performance is improved. The proposed scheme can be applied to both the frequency reuse of RNs and the frequency sharing of RNs in one cell. In the simulation, we verify the effectiveness of the defined RIM. Then we evaluate the performance of the proposed scheme in terms of relay link user throughput, spectrum efficiency and user fairness.