Joint Signal Processing in Femtocell Based Distributed Antenna Systems in High Buildings

In wireless systems, coverage and capacity is a major challenge especially in high buildings. The system performance is impaired by cochannel interference created due to the need to reuse the limited available spectrum in nearby floors. Each base station (BS) does not only receives signals from the desired user but also from cochannel interferers in the neighbouring floors, thereby limiting the coverage and capacity of the indoor networks. Joint processing of the received signal among cochannel receivers has drawn considerable attention in recent years due to its enormous benefits from an interference cancellation point of view. This paper proposes and investigates the uplink of a femtocell based distributed antenna systems (DAS) in high buildings where remote antenna units deployed (RAU) on each floor of the building are connected to femto BS. The femto BSs can cooperate through joint signal processing for all femtocells in order to estimate the received signal, reduce cochannel interference introduced by frequency reuse among the femtocells and maintain high spectral efficiency. Investigation and numerical results show remarkable gains especially when interference cancellation is employed at each cooperative femto BS, resulting in large capacity increase when compared with the traditional system with no interference cancellation technique.