On Uplink Interference Scenarios in Two-Tier Macro and Femto Co-existing UMTS Networks

In this paper, a two-tier UMTS network is considered where a large number of randomly deployed Wideband Code Division Multiple Access (WCDMA) femtocells are laid under macrocells where the spectrum is shared. The co-channel interference between the cells may be a potential limiting factor for the system. We study the uplink of this hybrid network, and identify the critical scenarios that give rise to substantial interference. The mechanism for generating the interference is analyzed and guidelines for interference mitigation are provided. The impacts of the cross-tier interference, especially caused by increased numbers of users and higher data rates is evaluated in the multi-cell simulation environment in terms of the noise rise at the base stations, the cell throughput and the user transmit power consumption.