Optimized asymmetric cooperation for downlink cloud radio access network under per-base station data transfer constraint

Abstract

Using multicell cooperation between several base stations (BSs) connected to a central processor (CP) via finite capacity digital backhaul links, the inter-cell interference, which is known to limit the standard cellular systems, can be mitigated. When all user data is sent to each BS through the CP, which is referred as the full cooperation, the interference can be perfectly eliminated, however, this may cause the capacity of backhaul links to be exceeded. In this study, it is aimed to find the optimal asymmetric cooperation strategy for downlink cloud radio access network (C-RAN) which minimizes the total transmitted power from BSs where each user's signal-to-interference-and-noise ratio (SINR) is lower bounded and the number of user data streams sent by each BS is limited. The original problem is NP-hard and requires a combinatorial search. In this paper, we propose two sub-optimal cooperation methods. The first method is based on iteratively increasing the number of users served by the BSs until all users are chosen, and the second is based on iteratively adding a user data stream to be sent to a BS. We also consider a known method, iterative link removal, which is based on iteratively removing a user data from a BS by starting the full cooperation scheme, and a modified version of this method as a comparison. The simulation results show that the proposed methods can provide better performance in comparison to other methods in the literature.