Investigation on Distributed Optimization of User Association and Inter-Cell Interference Coordination Based on Proportional Fair Criteria

摘要

Small cell deployments, which increase the base station (BS) density, are promising solutions to support the continuous growth of mobile traffic. In small cell deployments, the combined usage of user association and inter-cell interference coordination (ICIC) is inevitable; this requires the joint optimization of both techniques. Although joint optimization can be performed by solving the utility maximization problem, it is difficult to realize in an actual mobile communication system. This is because the achievable data rates for the users to all BSs should be known at the BSs. Meanwhile, in the small cell deployments in the LTE-Advanced, the reference signal received power (RSRP) plus cell-specific offset is used to select the connecting BSs; this connecting process is called cell range expansion (CRE). Although CRE is easy to implement in a system, it is difficult to optimize the cell-specific offset. This paper therefore proposes distributed optimization. The global offset value for the CRE is used to select the first candidate for the connecting BS. Furthermore, additional candidates are selected if the RSRP difference from the first candidate is within the predetermined value. Each BS performs the corresponding resource allocation based on the “proportional fair” criteria. The effectiveness of the proposed distributed optimization is verified via computer simulation. Based on the simulation results, the proposed distributed optimization scheme can achieve the performance comparable to that of the joint optimization scheme.