Efficient joint user association and resource allocation for cloud radio access networks

Coordinated scheduling is an efficient resource allocation technique employed to improve the throughput, utilization, and energy efficiency of radio networks. This work focuses on the coordinated scheduling problem for cloud radio access network (CRAN). In particular, we consider the downlink of a CRAN where a central cloud performs the scheduling and synchronization of transmitting frames across the base stations (BSs). For each BS, the transmit frame is composed of several time/frequency slots called resource blocks (RBs). We formulate an optimization problem for joint users to BS association and resource allocation with an objective to maximize the overall network utilization under practical network constraints. The formulated problem is combinatorial and an optimal solution of such a problem can be obtained by performing an exhaustive search over all possible users-to-BSs assignments that satisfy the network constraints. However, the size of search space increases exponentially with the number of users, BSs, and RBs, thus making this approach prohibitive for networks of practical size. This work proposes an interference-aware greedy heuristic algorithm for the constrained coordinated scheduling problem. The complexity analysis of the proposed heuristic is also presented and performance is compared with the optimal exhaustive search algorithm. Simulation results are presented for various network scenarios which demonstrate that the proposed solution achieves performance comparable to the optimal exhaustive search algorithm.