Issues in Femtocell Deployments in Broadband OFDMA Networks: 3GPP-LTE a Case Study

Fourth Generation and beyond broadband wireless mobile networks, specifically 3rd Generation Partnership Project (3GPP)-Long Term Evolution (LTE) and beyond are considering issues related to the deployment of femtocells. Femtocells have the potential to improve Area Spectral Efficiency (ASE) several folds. However, interference is added to the system due to large number of uncontrolled, user-deployed femtocells. Hence improvement of overall system throughput becomes limited. In this paper, downlink coexistence between macro/micro cells and cochannel femtocells in a single frequency Orthogonal Frequency Division Multiple Access (OFDMA)/Frequency Division Duplex (FDD) network is investigated. The impact of density, load and transmit power variation of the femtocells on the performance of macro/micro cell and femtocell users as well as the effect of macro/micro cell load on femtocell performance is presented. Guidelines for femtocell deployment with the objectives of maximizing sum-cell-throughput and maximizing number of active femtocells are derived. Methods of centralized control as well mixed centralized and distributed control of femtocell radio parameters to meet the above objectives are presented. The analysis is done with International Telecommunication Union (ITU) specified channel models using system level simulator.