Optimal Adaptive Uplink Attenuation Algorithms for WCDMA Femtocell

Femtocells are assuming an increasing important role to extend the cellular network coverage and provide high speed data service for indoor environments. To cope with the extreme interfering cases in the WCDMA uplink scenario, Home NodeB (HNB) receivers need to employ uplink attenuation at the RF frontend to suppress the interfering signals introduced by unattached co-channel users, e.g., a penetrating signal from macro-connected users in the proximity. The optimal level of uplink attenuation at the HNB receiver should be designed to balance the requirements between the noise rise limitation in HNB and maximum transmit power cap for the femto-connected users. In this paper, we introduce two optimal adaptive schemes that apply the minimum and necessary level of attenuation to the received signal and show the outage probability improvement by the method of simulation.