Femtocell architectures with spectrum sharing for cellular radio networks

Abstract

Femtocells are an emerging technology aimed at providing gains to both network operators and end-users. These gains come at a cost of increased interference, specifically the cross network interference between the macrocell and femtocell networks. This interference is one of the main performance limiting factors in allowing an underlaid femtocell network to share the spectrum with the cellular network. To manage this interference, we first propose a femtocell architecture that orthogonally partitions the network bandwidth between the macrocell and femtocell networks. This scheme eliminates the cross network interference thus giving the femtocells more freedom over their use of the spectrum. Specifically, no interference constraint is imposed by the cellular network allowing femto users to transmit at a constant power on randomly selected channels. Although simple, this scheme is enough to give gains up to 200 % in sum rate. We then propose a second architecture where both networks share the bandwidth simultaneously. A femtocell power control scheme that relies on minimal coordination with the macrocell base station is used in conjunction with an interference sensing channel assignment mechanism. These two schemes together yield sum rate gains up to 200 %. We then develop a technique for macro users to join a nearby femtocell and share a common channel with a femtocell user through the use of successive interference cancellation. By adding this mechanism to the power control and channel assignment schemes, we show sum rate gains over 300 % and up to 90 % power savings for macrocell users.