Outage Probability Analysis for Collocated Spectrum-Sharing Macrocell and Femtocells

Femtocells have been considered by the wireless industry as a promising solution not only to improve indoor coverage, but also to unload traffic from already overburdened macrocells. In spite of potentially excessive interference caused by densely deployed femtocells, macrocells may have to share the same spectrum with femtocells, due to spectrum availability and network infrastructure considerations. In this paper, we derive closed-form expressions for downlink outage probabilities (OP) of collocated spectrum-sharing macrocell and femtocells, based on the stochastic geometry theory. Orthogonal frequency division multiple access (OFDMA) is considered in the downlink of both macro- and femto-cells. Simulation results show that the derived OP expressions are able to predict OP performance of collocated spectrum-sharing macro- and femto-cells, and provide insights on the effects of different system and channel parameters on co-channel femtocell deployments.