Boosting capacity through small cell data offloading: A comparative performance study of LTE femtocells and Wi-Fi

Due to the significant increase in mobile data traffic volume during the last few years, offloading techniques have been considered for alleviating the traffic load from cellular networks. Two principal small cell offloading solutions are LTE femtocells and Wi-Fi. Femtocells are low power user-deployed LTE base stations that overlay the macro-cellular network and share its licensed spectrum, whereas Wi-Fi devices operate in unlicensed bands using the distributed CSMA/CA MAC protocol to coordinate neighbouring transmissions. Given the fundamentally different spectrum use regulations, MAC, and PHY layer capabilities of these two technologies, the resulting interference environments of the respective small cell networks are significantly different. It is thus not trivially obvious which offloading solution realistically provides a better and future-proof capacity extension for service providers. In this paper we present a thorough system-level comparative study of IEEE 802.1 In Wi-Fi against LTE femtocell performance for a range of representative network densities and deployment scenarios, considering realistic propagation effects, multiple interference sources, and several resource allocation schemes. Our results show that in low density suburban and rural scenarios the high spectral efficiency of LTE femtocells yields a higher throughput than Wi-Fi, but that the CSMA/CA MAC protocol enables Wi-Fi to outperform LTE femtocells in dense urban scenarios, where the need for extra capacity is most urgent. We show that future high density heterogeneous networks may be best served by a new hybrid small cell offloading solution, combining the superior PHY of LTE and the distributed co-tier interference coordination afforded by the MAC of Wi-Fi.