Macro- and femtocell interference mitigation in OFDMA wireless systems

We conceive an interference mitigation scheme, for twin-layer networks for protecting the macrocell-users, from the interference imposed by the femtocells as well as for mitigating the interference amongst femtocells. Femtocells are capable of finding the available sub-bands using cognitive radio techniques, where the lowest interference is observed by the nearby macrocell-users. A sub-channel allocation algorithm is developed with the aid of graph-theoretic approaches for optimizing the femtocell throughput in dense femtocells deployment scenarios. The femto-users are grouped into different clusters for suppressing the interference amongst them. Each cluster is assigned a unique sub-channel by using the classic cluster-coloring approach. Adaptive power allocation is performed among the femtocells for further enhancing the system throughput and the attainable performance is quantified.