Hybrid Access Design for Femtocell Networks with Dynamic User Association and Power Control

In this paper, we propose a universal power control (PC) algorithm that can provide QoS support in minimum signal-to-interference-plus-noise ratios (SINRs) for all users while exploiting differentiated channel conditions to enhance the network throughput. In particular, we design the PC algorithm by using non-cooperative game theory and establish sufficient conditions for its convergence. Then, we apply it to design a hybrid access scheme for two-tier macrocell-femtocell networks. Specifically, we devise a distributed load-award association algorithm for macro users, which enables flexible user association to BSs of either tier. In addition, we develop an efficient mechanism based on which users can steer the equilibrium in such a way that they achieve their desirable performance targets. Numerical results are then presented to validate the theoretical results and demonstrate the desirable performance of the proposed algorithms.

I. Introduction

Deployment of low-power femto BSs (FBSs) can significantly enhance indoor coverage and capacity [1], [2]. However, FBSs operate on the same licensed frequency bands with the existing macrocell network, which can create severe crosstier interference for MUEs. There are three different access modes for spectrum sharing between the macro and femto tiers, namely closed, open, and hybrid access. In general, open access is more effective in mitigating cross-tier interference compared to the closed access while it may result in uncontrollable performance degradation for macro users [2]. Design of an efficient hybrid access scheme that can balance between advantages and disadvantages of the other two access modes is an interesting and important research topic.