Interference avoidance via resource scheduling in TDD underlay femtocells

In this paper, we proposes a resource reuse scheme for femtocell networks. In this context, macrocells operate in a Frequency Division Duplexing mode while all femtocells employ the macrocellular uplink spectrum in a Time Division Duplexing mode. We propose two solutions. In the first one, a centralized scheduling is performed via list-coloring based on the overall conflict graph. The second solution is distributed and autonomously performed by each femto access point (FAP), based on local conflict graph. The two solutions are compared to a coordinated LTE-A compatible and a random allocation schemes in terms of spectral efficiency and activity factor in the superframe. Finally, given a target Quality of Service requirement, the proposed distributed scheme is evaluated. Results show that self-organizing femtocell operating in an uncoordinated way achieves a good tradeoff of performance when a limited feedback from femto users is exchanged.