Energy efficient network for rural broadband access

• Main Author: McGuire, Colin
• Published: University of Strathclyde 2014
• Subjects: 621.3
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.640869

This thesis proposes and discusses aspects of a low-cost wireless network called "Hopscotch" as a potential solution to the rural broadband problem. Providing broadband internet access to rural locations is challenging due to the long distances between internet backbone and households, the sparse population density and difficult terrain. Hopscotch uses a network of renewable powered base stations, termed "WindFi", connected by point-to-point links, to deliver internet access to rural communities. A combination of frequency bands are used within Hopscotch. Standard IEEE 802.11 5 GHz WiFi access technology is used for high capacity links, and an ultra high frequency TV "white space" spectrum overlay in the 600-800 MHz band provides long distance coverage. The advantages of "white space" spectrum are demonstrated for a rural wireless scenario; reducing the number of base stations required to cover a community and decreasing the transmit power required to create long distance links over challenging terrain. The use of renewable power allows WindFi base stations to be well placed to serve a community, irrespective of available infrastructure. The power system is the biggest cost component of the base station therefore the system must be carefully sized. The design of the WindFi base station is presented and the specification of the renewable power generation system validated with operational data. To reduce the energy required, and therefore the demand on the renewable power system, aspects of energy use within the base station are considered. Models of the power consumption and data rate selection for radios used in Hopscotch are presented. Hopscotch trials have been running on the Scottish islands of Bute and Tiree. Measurement based models of household distribution, daily network internet traffic and large-scale path loss for a rural community are presented based on trial results, which are useful for simulating rural broadband networks. To minimise the power consumption of the WindFi base station, an energy optimisation is presented for a Hopscotch scenario. Dynamically altering the assignment of users between two overlay radio access networks, based on the instantaneous capacity required, is shown to reduce power consumption. The optimum assignment between the networks to maximise individual user throughput is also presented.