Distributed load balancing via message passing for heterogeneous cellular networks

This paper presents a distributed load-balancing algorithm that maximizes the network-wide sum rate in heterogeneous cellular networks (HetNets). Unlike previous studies that have considered a logarithmic utility defined with respect to the sum rate, we maximize the sum rate directly to achieve the best user association for the HetNet. To capture realistic communication scenarios, we also consider a minimum rate constraint for individual users. The corresponding problem is formulated as a combinatorial optimization of which finding the solution becomes computationally demanding as the size of the network grows. Another challenge in HetNets is that the information exchange among base stations (BSs) is limited if each tier of BSs is deployed by different network vendors or users, and this brings about the need for distributed control. To resolve these challenges, we introduce a promising approach based on a message-passing framework and derive a distributed load-balancing algorithm. The proposed algorithm developed via message passing provides a very efficient solution for the load-balancing problem with reduced computational complexity. We compare the proposed algorithm with existing load-balancing strategies. Simulation results verify that the proposed algorithm significantly improves resource utilization and mitigates the congestion of macro BSs, thereby resulting in a multifold gain to the sum rate.