Throughput Utility Optimization in HetNets

The deployment of pico cells to cover traffic hot spots within the footprint of a macro cell provides a powerful approach to meet the massive growth in traffic demands fueled by smartphones and bandwidth-hungry applications. Joint optimization of resource allocation and user association is of critical importance to achieve the maximal capacity benefits in such heterogeneous network deployments (HetNets). We specifically examine the problem of maximizing the aggregate throughput utility of the various users. We characterize the structure of the optimal solution, and identify a simple optimality condition in terms of the transmission rates of the edge users between the macro cell and the various pico cells. Exploiting the structural properties, we develop distributed online algorithms for the broad class of alpha-fair utility functions, which includes several common fairness notions. Numerical experiments are presented to illustrate the results.