Mast

Tegola (“rooftile” in Italian) is about bringing broadband to rural communities. The villages of Arnisdale and Corran, and the northwest shores of Knoydart are typical of many communities that are out of reach of commercial broadband. The main problem is cost. Technology that works when thousands of people live within a short distance of each other is hopelessly expensive when you have a population of 100 people living in as many square miles.

For reasons described in the Technology Brief the only viable option is wireless, so we need to use cheap wireless technology – the same technology that is used to for cordless telephones and wifi communications in your house. The hardware for this is mass-produced and therefore very cheap.

Although this hardware is designed to work indoors over short distances, with the use of directional antennae we can make it work over distances of several miles, and it can deliver very good performance. Our total investment in hardware so far is less than £10,000.

In our initial configuration we have built a ring of masts to connect us the backhaul at Mòr Ostaig. There are two reasons for building a ring: first, from any mast there are two routes to the backhaul, and we can exploit this for extra speed; second, if one of the masts fails all the other masts will still have a connection. Each mast serves a cluster of houses. We have mounted small relays on some houses. These receive a signal from the mast and transmit it to that house and nearby houses. In fact, if you open up a laptop in some parts of Arnisdale, you will get a free wireless connection.

Our current configuration is already delivering reasonably good performance, which is promising — we are already achieving speeds in excess of 10 Mbps, a speed you would be lucky to get in a city. But of course we are limited by the bandwidth available to connect to the wired backhaul. In the long-run the provision of adequate backhaul capacity to serve the whole of the Highlands and Islands may be a major problem. Additionally, the end user access speeds are dependent on a number of factors including, the number of active users, the available radio spectrum and its efficient usage and radio propagation characteristics. Efficient spectrum usage is in turn dependent on how effectively the issues such as mast placement, configuration of radios and antennas on the masts, and channel access protocol design are addressed. So even efficiently distributing the available wired backhaul capacity among end users requires an in-depth understanding and experimental study of a range of technical issues.