Analysis of area spectral efficiency for co-channel deployed macrocell-femtocell OFDMA networks

Deployment of femtocells is expected to overcome indoor coverage problems and enhance the Area Spectral Efficiency (ASE) in Orthogonal Frequency Division Multiple Access (OFDMA) cellular systems such as Long Term Evolution and Worldwide Interoperability for Microwave Access. However, unplanned deployment of co-channel femtocells in existing macro-cell networks results in severe interference in the system which limits the possible gain achievable in ASE. In this paper, we derive the ASE of OFDMA based co-channel macrocell-femtocell networks as a function of femtocell radio parameters such as transmit power, load and femtocell density. The ASE has been derived considering activity of interfering base stations under fractional load conditions in macrocell and femtocell networks. We investigate on the optimal femtocell radio parameters that maximizes the ASE for a given network condition while maintaining Quality of Service (QoS) requirements of both macrocell and femtocell users. It is seen that for uncontrolled deployment of femtocells in co-channel deployment mode, the maximum ASE is achieved at the cost of QoS of macrocell users. However, it is shown that if radio parameters are suitably controlled, the ASE can be maximized without affecting macrocell user performance.