Satellite broadband: can it bridge the UK's digital divide?

Satellite broadband is a worthwhile alternative

The ka-band radio transmission system works at 30GHz for uplinks and 20GHz for downlinks and is key to the improved throughput - older satellite systems had to cover much larger areas in a single spot. These new narrow spot-beams improve performance in a number of ways, including re-using assigned frequencies multiple times - this enables them to achieve much higher capacity than conventional broad-beam satellites. The narrow-beams enable higher, more focused power and increased receiver sensitivity for 35 times the throughput of standard ku-band satellite coverage.


Tooway router
A Tooway satellite broadbandee router

At the consumer end of the equation is a 77cm satellite dish, which uses a satellite modem that demodulates and modulates the TCP-IP network information into a suitable radio signal for the dish to send and receive.

The Tooway modem offers the usual Ethernet output, so it's easy to integrate into an existing home network or build up a new one around it. Eutelsat operates eight dedicated base-stations known as gateways to which the satellite directs the appropriate signal, and the gateway - acting as the ISP - routes signals to and from the larger internet.

Interestingly, the cutting-edge ka-band system isn't as affected by adverse weather conditions. Sky and Freesat users often find that heavy rain interferes or entirely blocks satellite TV signals, an effect known as 'rain fade'. When the ka-band system was originally deployed, it was expected to handle heavy-rain conditions well, but according to Tooway, once in full service it will be largely unaffected. This is done mainly through adaptive uplink power control and an ultimately reduced bit rate to ensure a continuous service across the board.

Latent issues

The one weakness that remains for satellite broadband is latency, which is something that simply can't be eliminated. Being 22,236 miles away, it takes a radio signal travelling at the speed of light 250ms just to get to the satellite. Typically, latencies bounce around the 600 to 800ms range, making the system unsuitable for gaming as even dial-up modem latencies can be as low as 120ms.

Potentially, satellite broadband can offer far lower latencies by using lower orbiting satellites - at 5,000 miles this would be down to 125ms or as low as 10ms at 620 miles. However, as these lower orbiting satellites don't stay in a fixed position, a considerable net of multiple satellites would be required to maintain a connection. But this would cause additional complexities in the receiving antenna that would have to balance bit rate against ease of reception.

Despite this, gaming is about the only service that's unrealistic for geostationary satellite broadband. Using predictive caching web browsing can be made perfectly snappy as any land-based service, while Skype and voice services work as well as you would expect .