User Association to Optimize Flow Level Performance in Wireless Systems with Dynamic Interference

We study the impact of user association policies on flow-level performance in interference limited wireless networks. Most research in this area has used static interference models (neighboring base stations are always active) and resorted to intuitive objectives such as load balancing. In this paper, we show that this can be counterproductive in the presence of dynamic interference which couples the transmission rates to users at various base stations. We propose a methodology to optimize the performance of a class of coupled systems, and apply it to study the user association problem. We show that by properly inducing load asymmetries, substantial performance gains can be achieved relative to a load balancing policy (e.g., 15 times reduction in mean delay). Systematic simulations establish that our optimized static policy substantially outperforms various dynamic policies and that these results are robust to changes in file size distributions, channel parameters, and spatial load distributions.