Energy optimizations in broadband access networks

Despite the increased interest in competitive technologies, access network operators are keen to deploy digital subscriber line (DSL) that uses the existing copper-based telephony infrastructure. This is because of its low deployment cost compared to fiber to the user based access networks and relatively high bandwidth compared to wireless access networks. As power costs and sustainable business operations become key concerns, energy-efficient access networks including DSL is getting traction. In this book chapter, we study different ways to save energy in access networks: spectral optimization at the physical layer and deployment practices. While we focus on DSL technology the concepts as described can be readily applied to other access technologies such as fiber, cable or wireless. Traditionally, communication systems are focused on the rate maximization as an end-user utility and hence do not care about the energy consumption. We show that we can trade-off power against data rate, as long as this doesn't impact the required service by taking into account the power cost to achieve certain user's social utility e.g. data rate. The potential energy gains depend on both the hardware technology and the aggregate transmit power. The second part of this chapter focuses on deployment practices and describes how different access network architectures can improve the energy consumption, when considering both the telecom equipment and its supporting functions. We show that introducing an access network architecture which distributes more functions in the outside plant does not negatively impact energy consumption of the access network.