FERMI: A Femtocell Resource Management System for Interference Mitigation in OFDMA Networks

Abstract

The demand for increased spectral efficiencies is driving the next generation broadband access networks towards deploying smaller cells (femtocells) with sophisticated air interface technologies (Or- thogonal Frequency Division Multiple Access or OFDMA). The projected dense deployment of femtocells however, makes interfer- ence and hence resource management both critical and extremely challenging. In this paper, we design and implement one of the first resource management systems, FERMI, for OFDMA-based femtocell networks. As part of its design, FERMI (i) provides re- source isolation in the frequency domain (as opposed to time) to leverage power pooling across cells to improve capacity; (ii) uses measurement-driven triggers to intelligently distinguish clients that require just link adaptation from those that require resource isola- tion; (iii) incorporates mechanisms that enable the joint scheduling of both types of clients in the same frame; and (iv) employs ef- ficient, scalable algorithms to determine a fair resource allocation across the entire network with high utilization and low overhead. We implement FERMI on a prototype four-cell WiMAX femtocell testbed and show that it yields significant gains over conventional approaches.