Achieving User-Level Fairness in Open-Access Femtocell based Architecture

Femtocell based architectures have the potential to position the cellular service providers to compete head-on with the WiFi market. However, significant interference can happen due to unplanned deployments. Current use of hard partitioning approaches for resource allocation, and lack of guidelines for configuring the femtocells, make it difficult to obtain significant performance gains over traditional cellular networks. In this paper, we study the dynamic OFDMA sub-channel assignment problem while jointly considering power assignment and association control to provide maxmin fairness. Towards this objective, we first consider a non-interfering model, which disallows interfering femtocells in the solution. A more general interfering model is then considered under which the problem is transformed into the partition coloring problem. We then show the NP-hardness of the problems and design centralized approximation algorithms with provable bounds and distributed solutions. Through extensive simulations in realistic settings we show that, compared to the traditional macrocell based architecture, our solutions under the non-interfering model can achieve 2x of minimum throughput, and under the interfering model the minimum throughput can be up to 3x of the baseline algorithms.