Energy-Efficient Design and Optimization of Wireline Access Networks

Access networks, in particular, Digital Subscriber Line (DSL) equipment, are a significant source of energy consumption for wireline operators. Replacing large monolithic DSLAMs with smaller remote DSLAM units closer to customers can reduce the energy consumption as well as increase the reach of the access network. This paper attempts to formalize the design and optimization of the "last mile" wireline access network with energy as one of the costs to be minimized. In particular, the placement of remote DSLAM units needs to be optimized. We propose solutions for two scenarios. For the case where an existing all-copper tree is to be transformed into a fiber-copper tree with remote DSLAM units, we present an optimal polynomial-time solution. The green field case is when when both the tree layout and the placement of remote DSLAM units must be determined. We show that this problem is NPcomplete. We present an ILP formulation and design an efficient heuristic-based approach to build a power-and-cost-optimized access network.