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Broadband Wireless Access |
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Cambridge Public
Fixed Wireless Access Trial - A Description of the Study A networking
system delivering high-speed broadband connectivity by radio has been
rolled out in the Cambridge area under the management of Cotares Ltd.
It was part of a research programme sponsored by Ofcom to promote the
efficient use of radio spectrum. The system continues to deliver fast
broadband connectivity to 75 locations in both Cambridge City and some
rural locations. After the end of the research project in March 2004
the running of the network was handed over to Cambridge Broadband Ltd. 
The project infrastructure consists of five Fixed Wireless Access base stations, four in Cambridge and one in a rural location, and 50 subscriber units. The subscriber units were placed on volunteer users’ homes. Some subscriber units connect WiFi Access Points to the Internet forming wireless Hot Spots for a further 25 users. A bonus to those users taking part in the experiment is the use of an internet connection up to 30 times faster than current domestic wired broadband. The project is using wireless kit operating in the 3.5 GHz band supplied by Cambridge Broadband Ltd. who also providing initial advice and expertise. Besides Cotares Ltd and CBL the third member of the research consortium formed to perform this research was the Laboratory for Communications Engineering (LCE). This was then part of the Cambridge University Engineering Dept. and is based in the William Gates Building on the West Cambridge site. The Fixed Wireless Access base stations consist of four antennae, each handling a 90 degree wide sector. Fibres from each antenna are aggregated in a small, nearby, equipment rack. The whole base station is connected to the Gates Building, which houses the hub of the radio network, either by fibre connection or by a further radio link. Wireless base stations are to be sited on the roof of Addenbrooke’s Hospital; at Cambridge Water’s Lime Kiln Hill site; the William Gates Building; and possibly the Anglia Polytechnic University. At the Gates Building the connections from all the radio subscriber units are routed through to the Internet via the project’s own ISP connection. A number of server PC’s log all the system activity and are programmed to generate test data streams to simulate a wide variety of network operating conditions. The project is sponsoring a Research Assistant in the LCE who will develop a 3D ray-tracing simulation model of urban and rural wireless propagation. The model will use real high definition 3D terrain data. To verify the accuracy and permit further refinement of the model Cotares Ltd. will make a very detailed radio survey of the coverage area using an elaborately equipped radio measurement vehicle. The research has generated a report, published by Ofcom, which gives advice on some key issues concerning the rollout and management of Fixed Wireless Access networks. Wireless operators will need to be able to plan their networks to avoid coverage problems at operator boundaries. One large and expensive radio system could be efficiently used by multiple operators simultaneously - this raises questions about the maintenance of service quality for each operator. Radio systems are inevitably rolled out cautiously - starting with one base station for a large area and progressing to a patchwork of many base stations as the network attracts subscribers. This study makes recommendations on maintaining spectral efficiency during such a rollout. We are also interested in studying the question of when it may become efficient to migrate heavy users to alternative point-to-point networks. Finally, we acquired experience in how to manage and backhaul WiFi radio hotspots over Fixed Wireless Access networks.
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Contact Details:
Cotares Ltd - 67 Narrow Lane
Histon Cambridge B4 9YP |