The problem

BT's priorities for phone-based broadband are clear. They would rather concentrate on sexy high profile projects in densely populated urban areas where there are lots of potential customers.

Grafting high speed broadband onto a rural network that was installed half a century ago for simple voice communications is in the "too difficult" category, and receives relatively little attention. Our telephone service in the Norbury area comes from the Whitchurch (01948) exchange, which is over 12 km away for many users. This is well beyond the effective range of conventional ADSL phone-based broadband. TalkTalk have installed their own equipment in Whitchurch exchange as part of Local Loop Unbundling, and have managed to enable a limited number of customers in the local area, but the service quality is patchy and speeds very low (around 256 kbps, which doesn't really qualify as broadband at all!).

There are other local telephone exchanges at Aston (01270) and Cholmondeley (01829) that are broadband-enabled, and these are considerably closer for many subscribers than the distant exchange at Whitchurch. However, utilising these exchanges by laying short lengths of new cable to "bridge the gap" is something that BT have shown no interest in exploring. They must have been very clever fellows who planned the network, if their decisions on routing are still sacrosanct fifty years later!

The solution

Bickleywood radio mast

Close-up of radio gear, showing two units broadcasting to relays and one (top) back to house

We tap into the BT broadband network at Bickleywood, No Man's Heath, about 1.5 km from the Hampton Heath exchange. There is no advanced broadband equipment installed here, but it does give us access to a basic 4 Mbps ADSL signal. Radio transmitter/receivers operating at 4.8 GHz relay the signal onto to local masts at Outridge Barn, Holtridge, and Villa Farm, Norbury Common. A second unit at Villa Farm sends it on to Higher Hall Farm, Norbury.

Relay at Villa Farm

These three relays provide the link to the end users. A small subscriber unit mounts on the outside wall of the customer's premises and plugs into the user's computer. Alternatively it can connect to a DSL router to provide broadband connectivity to a local network, either wired or wireless, or a mixture of the two.

The subscriber unit must have clear line of sight to the relay. Objects such as buildings or trees will seriously degrade the signal. For the same reason, the subscriber unit must be mounted on an outside wall facing the relay. The signals are too weak to pass through walls, so cannot be received indoors. All the radio equipment is fully weather-proof, and is designed to withstand the elements.

Subscriber Unit

The system is controlled by a small dedicated Linux box installed at Bickleywood. This provides gate-keeper functions, and ensures that only authorised users connect to the system. It also allocates the available bandwidth to ensure that all users get a fair share. All the radio units run unattended, and network management functions are all provided remotely.

Relay map

The three local relays are shown on the map below. Subscribers need a line of sight to one of these relays in order to user the service