ElasticWISP: Energy-Proportional WISP Backhaul Networks
The provision of rural broadband infrastructure is a challenge for network operators across the globe, irrespective of their size. Wireless Internet Service Providers (WISPs) have shown that the small-scale deployment of wireless broadband infrastructure is a viable alternative to relying on cellular network providers for remote coverage. However, WISPs must often resort to using off-grid renewable energy sources such as solar energy for powering network sites, often resulting in undesirable, low-performance backhaul radios being used between sites out of concern for excessive energy consumption. The challenges of managing performant wireless backhaul networks in respect to energy constraints at remote, off-grid sites informs the need for energy-proportional design. Backhaul radios typically used by WISPs are not energy-proportional, meaning they use a consistent amount of energy, irrespective of wireless link utilisation. Using data from a real WISP network, diurnal traffic patterns show that WISP networks could benefit from energy-proportional design, without having to sacrifice performance. To encourage the development of high-performance, energy-proportional WISP backhaul networks, ElasticWISP, an optimisation architecture that reduces network-wide backhaul energy consumption while satisfying the user-demand for traffic, is introduced. ElasticWISP dynamically controls the configuration of backhaul radios based on bandwidth demands and the network-wide energy consumption of these radios. Through simulations driven by real WISP topology and data traffic, results show that ElasticWISP can offer energy savings of approximately 65% when WISP operators follow the proposed backhaul design methodology. Finally, a lightweight Multiprotocol Label Switching (MPLS)-based traffic engineering scheme, based on Segment Routing, is proposed. The implementation, named Segment Routing over MPLS (SR-MPLS), keeps traffic engineering path-state within each packet, meaning per-flow state is only held at SR-MPLS ingress routers. The lightweight approach of SR-MPLS also eliminates the otherwise necessary network-wide label flooding of traditional Segment Routing, making it ideal for bandwidth-sensitive wireless backhaul networks. Evaluation of SR-MPLS shows that it can perform as well as – and sometimes better than – competitor schemes.