Distributed and QoS-driven cell association in HetNets to minimize global outage probability

This paper addresses the cell association problem in the downlink of a multi-tier heterogeneous network (HetNet), where base stations (BSs) have finite number of resource blocks (RBs) available to distribute among their associated users. We define the global outage probability as the event where at least one user in the network experiences outage. An optimization problem is defined to minimize this global outage probability while maintaining quality of service (QoS) through two phases: Cell association phase followed by the optional RB distribution phase. The cell association problem is an NP-hard problem. We transform the cell association problem into a linear program, for which we propose a distributed cell association algorithm by using Lagrange dual decomposition method. An admission control scheme is also proposed to address the infeasibility problem and achieve load balancing. Finally, the effectiveness of our proposed distributed algorithm is examined through numerical simulations.