Subchannel and power allocation schemes for clustered femtocells in two-tier OFDMA HetNets

We study the problem of subchannel and power allocation in a dense deployment of femtocells in a two-tier orthogonal frequency-division multiple access (OFDMA)-based HetNet with constraints on co-tier and cross-tier interferences as well as minimum data rate requirements. We also study the effect of clustering (or cooperation) of femtocells into disjoint groups on the sum-rate capacity of femtocells. The problem is formulated as a Mixed Integer Non Linear Program (MINLP) and we propose to solve the problem in two phases. In the first phase, for given power allocation, we perform subchannel allocation. To accomplish that, we propose different schemes for subchannel allocation with varying complexity. In the second phase, knowing subchannel allocation, we perform power allocation. Numerical results show that, in a dense deployment of femtocells with tight interference constraints, clustering is a very efficient technique. Also, the proposed schemes have near optimal performance with reduced complexity.