Bristol Wireless are currently halfway through rolling out a backbone expansion of their, allready large, public wireless network. This will increase the size of the network many many times and improve the expandability, reliability and lots of other words ending in 'ity'. I have been heavily involved in the choice of hardware, software and implimentation of this backbone and hope to explain alittle more about it in this article.
There are three main backbone locations, which together will form a point to point radio triangle over the city centre. This triangle is run using licenced 802.11a 5.8GHz radios built into a modified compaq small form factor pc. Each site will also supply client access via four 90degree sectors running on the more common 802.11g 2.4GHz.
The wireless hardware at each site was mounted ontop of council owned, sixteen story, tower blocks with the help of John and Richard, engineers from Westcom.
The routers run a cut down linux distribution called voyage linux, this boots from solid state flash memory rather than a normal harddisk for reliability reasons. Each router has: 5* 10/100 ethernet ports, 4* Atheros minipci a/b/g wireless cards and a modified backing plate for the antenna connectors.
The sector antennas are driven by linksys wap54g's mounted in a waterproof boxes as to reduce antenna cable loss. These are connected to the router inside via ethernet cable which also supplys the power to the device with PoE. The wap54g is actually just a slower version of the more popular wrt54g, but since we are doing all our routing on a single router we did not require this extra power so went with the cheaper option. Each of the wap's run hyperwap, a linux distribution which gives a few extra features over the stock linksys firmware. The reason for not just using the original firmware was the fact we need to be able to turn the transmit power down!.
Each towerblock will have its own seperate ospf area on our network for client access for that area of the city, while the backbone triangle will be area 0. This will hopefully lead to a much more stable Bristol Wireless network, aswell as a huge increase in capacity.
Article written by: Matt Leonard
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