Date Added: Sep 2011
In this paper, the authors study the strategic coexistence between macro and femtocell tiers, from a game theoretic perspective. A novel regret based learning algorithm is proposed whereby cognitive femtocells mitigate their interference toward the macrocell, on the downlink. The proposed algorithm is fully decentralized relying only on the Signal-to-Interference-plus Noise Ratio (SINR) feedback to the corresponding femtocell base stations. Based on such local observations, femto base stations learn the probability distribution of their transmission strategies (power levels and frequency band) by minimizing their regrets for using certain strategies, while adhering to the cross-tier interference constraint at the macrocell tier.