Joint optimization method for user association and time/frequency-domain scheduling to maximize system throughput in heterogeneous networks

This paper proposes a jointly optimized user association and time/frequency-domain scheduling method that maximizes the downlink system throughput defined based on (p, «)-proportional fairness. A previously reported user association method by members of our research group maximizes the downlink system throughput considering the base station (BS) distribution, user distribution, and the average channel conditions between each of the BSs and user terminals. However, the overall performance of the user association and subsequent time/frequency-domain scheduling conducted at each BS against the connected users taking into account the instantaneous channel variation due to multipath fading is not sufficient, although this approach can be actualized without relying on inter-BS cooperation. The proposed method assumes the centralized radio access network (C-RAN) architecture and achieves joint optimization of the user association and time/frequency-domain scheduling with regard to the achievable system throughput defined based on (p, «)-proportional fairness. Computer simulation results show that the proposed method significantly enhances the achievable system throughput compared to the user association method based on the average channel conditions, especially when the number of pico BSs is large and the system throughput prioritizes the fairness among users.