Low-duty mode operation of femto base stations in a densely deployed network environment

Interference management is an important issue due to the wide deployment of femtocells by subscribers. An elementary solution to the interference mitigation problem is to restrict transmission of pilot signals by femto base stations (BSs) which have no serving subscribers, i.e. idle listening state operation. However, the implementation of the idle listening state in a femto BS opens a possibility of having a problem in location update because a femto BS in idle listening state and a user equipment (UE) in idle mode are not able to communicate with each other. This happens because none of these initiates communication, i.e. the deadlock problem. We consider three types of solutions to this problem; UE based, femto BS based, and network assisted solutions. Our proposed solutions handle the deadlock problem as well as the interference mitigation problem. In addition, our proposed solutions are able to be with any existing power control based interference mitigation scheme. Through simulations and numerical analysis, we show that our proposed solution considerably enhances the network capacity and save energy consumption.