Energy Efficiency Consideration for Indoor Femtocell Networks in TV White Spaces

The federal communications commission (FCC) took the unprecedented step to approve the usage of TV white spaces, i.e., locally vacant TV channels, in 2012. This TV spectrum will present new opportunities for wireless access technologies and applications, e.g. femtocell networks. The utilization of TV white spaces in femtocell networks also comes with some technical challenges. One of the most fundamental is that how much capacity and energy efficiency can be achieved in TV white spaces network. Prior works only focused on capacity consideration for cellular network in outdoor scenario leaving important femtocell network in indoor scenario largely open for investigation. In this paper, we explore the capacity and energy efficiency for femtocell network by developing a TV white spaces reuse and power allocation scheme. The problem is formulated into an optimization problem with the objective to maximize the energy efficiency achieved by a femtocell network, while keeping the interference to the primary receiver and macro receiver at an acceptable level. We demonstrate the existence of a unique globally optimal transmit power vector for all the femtocells, and propose a gradient absent algorithm to obtain it. Simulation results show that the femtocell can have a considerable capacity and energy efficiency improvement by using the TV channels.