Capacity comparison for CSG and OSG OFDMA femtocells

The low-power and low-cost femtocells can improve indoor coverage and capacity. However, when femtocells are deployed extensively, the serious two-tier interference problem occurs. The method to access the femtocell is the key to manage the interference in the femtocell systems. In this paper, we investigate the impacts of access methods and directional antenna on link reliability and capacity for the orthogonal frequency-division multiple access (OFDMA)-based femtocell systems. Simulation results show that the open access method can improve the femtocell capacity over the traditional closed access method. Nevertheless, under the link reliability requirement of indoor and outdoor users, the improvement in femtocell capacity due to open access method is minor. Thanks to the narrow-beam pattern, the switched-beam directional antenna can be used to further reduce the interference and enhance the capacity. It is shown that the open access method using the switched-beam antenna can achieve higher femtocell capacity than that using the omnidirectional antenna.