Uplink Interference Management for HSPA+ and 1xEVDO Femtocells

Abstract

Femtocells are low power cellular base stations typically deployed indoors in residential and enterprise environments as well as hotspots in order to improve voice and high rate data coverage and provide excellent user experience. The cellular operator benefits from reduced infrastructure deployment costs for capacity upgrades and coverage improvements. While improving performance, femtocells may cause some interference to other users in the network. However, with the use of proper interference management techniques, this interference may be well controlled. This paper focuses on uplink (UL) interference management techniques for 3G femtocell deployments. On the UL, the challenge is the presence of large uncontrolled interference from nearby users not associated by the femtocell that result in high noise rise (rise-over-thermal, RoT), that may lead to poor femto user experience. Femtocell users that can not be power controlled due to their very close proximity to femtocells may also cause high noise rise levels. An algorithm is proposed for both HSPA+ and 1xEVDO femtocells to desensitize the receiver when uncontrolled interference is detected, ensuring robust UL performance with minimal impact on the macro network. It is demonstrated through system level simulations that in addition to superior performance experienced by femtocell users, the macro users also benefit significantly from offloading traffic load to the femto network.