Dynamic cross-tier interference management in heterogeneous network

As conventional single-layered network cannot satisfy the increasing demand in high-speed indoor data service, femtocell has been introduced to provide higher network capacity and better user experience. However, the downlink transmit signal from femtocell base station (FBS) may result in severe cross-tier interference to macrocell users (MUE). To address this problem, we propose a dynamic femtocell exclusion mechanism to alleviate the downlink cross-tier interference for MUE. The radius of the femtocell exclusion area, which is defined as reuse distance, is analyzed while taking account of the target outage probability and random position of the interfering FBSs. We derive the closed-form expression of the outage probability as a function of reuse distance. This expression provides a simple method to plan the exclusion area around the victim MUE. In addition, we introduce reuse table to avoid unpredictable interference caused by random appeared active FBS. Simulation results verify our theoretical analysis and show that the proposed mechanism can effectively alleviate the downlink cross-tier interference and improve the user capacity of the network.