Coexistence of pico- and femto-cellular LTE-unlicensed with legacy indoor Wi-Fi deployments

Due to the high expected increase in mobile data traffic and the scarcity of licensed spectrum for cellular networks, 3GPP has started preliminary work for standardizing LTE operation in the 5 GHz unlicensed band (LTE-U). However, LTE-U would interfere with other legacy technologies operating in the unlicensed band, the most important being contention-based Wi-Fi, which would be blocked by conventional LTE, which is designed for dedicated licensed spectrum. Consequently, some coexistence-enabling mechanisms have been proposed for LTE-U, but their evaluation is still at an early stage. In this paper we present a detailed system-level study on the downlink throughput performance of legacy indoor IEEE 802.11n and LTE-U deployments coexisting in the 5 GHz band. We consider several LTE-U coexistence mechanisms (i.e. listen-before-talk and interference-aware channel selection) in indoor LTE-U femtocell and outdoor LTE-U picocell scenarios with a realistic range of network densities and real outdoor picocell locations. We also study coexistence of LTE-U networks deployed by multiple operators, and evaluate the impact of different LTE-U transmit power levels. Our results show that in general both Wi-Fi and LTE-U benefit from the large number of available channels and isolation provided by building shielding at 5 GHz. Additionally, in typical indoor coexistence scenarios, interference-aware channel selection is more efficient for both Wi-Fi and LTE-U than listen-before-talk mechanisms. For outdoor LTE-U picocells and indoor Wi-Fi deployments, the two networks are isolated from each other, but listen-before-talk can increase LTE-U user throughput when multiple outdoor LTE-U networks deployed by different cellular operators coexist.