Dynamic Spectrum Sharing for Hybrid Access in OFDMA-Based Cognitive Femtocell Networks

Abstract

Cognitive femtocell has emerged as one of the promising ways to solve the indoor coverage and spectrum shortage problems in cellular networks. However, it is a challenge to motivate both macro base station ( $\text{MBS}$ ) and femtocell access points ( $\text{FAPs}$ ) to adopt this hybrid access policy. In this paper, we propose a systematic dynamic spectrum sharing framework for hybrid access in orthogonal frequency-division multiple-access-based cognitive macro-femtocell networks. In this framework, the $\text{MBS}$ offloads some macro user equipments ( $\text{MUEs}$ ) to $\text{FAP}$ to improve the transmission performance and save energy. In return, the MBS leases a portion of its spectrum to $\text{FAP}$ . Then, the $\text{FAP}$ can use a part of spectrum for its own transmission and use another part to serve $\text{MUEs}$ . We design an auction-based approach where each $\text{FAP}$ receives additional $\text{MUE}$ as bidders, while MBS acts as auctioneer. We formulate the dynamic resource sharing as a sum utility maximization problem. Numerical results demonstrate that both the macro and femtocell could get benefit from our framework.