Boffins stretch Wi-Fi signals to 100km
Long-distance 'rural' comms on the cheap.
By John Dunn | Techworld | Published: 14:33, 20 March 2008
Intel’s researchers have come up with a way to send Wi-Fi signals up to 60 miles (100km), while maintaining a usable throughput of up to 6.5Mbits/s.
According to MIT’s Technology Review, the system is known as the 'rural connectivity platform' (RCP) for the way it can, at relatively low cost, connect towns to out-of-the-way locations otherwise bypassed by new communication technologies.
This is to be more than a lab engineer’s daydream and has been field tested in India, Panama, Vietnam and South Africa.
The technology is innovative on a number of levels. It works using a point-to-point design, which automatically lowers cost to a quoted region of $500-$1,000 (£250-£500) for a single connection – way below rival systems such as cable broadband or satellite.
Once terminated at the remote location, the connectivity it provides could be distributed using off-the-shelf Wi-Fi hardware.
It is also low-power, using around five to six watts for a system with three radios in a link, making it possible to power it during the day from solar power or by battery during the night.
A lot of this is down to clever re-engineering of the software used by conventional Wi-Fi hardware to keep data acknowledgements to a minimum. This also has benefits for bandwidth because it shaves back-channel chatter in favour of sending and receiving usable data.
"Applying a TDMA modification to the MAC layer of standard 802.11, Intel RCP is able to achieve connection distances of up to 100km unobstructed line-of-sight," says one of the researchers. "Additionally, the relay and fork modes of operation allow for more complex topologies. So even if there are mountains or rough terrain, the connection between the base station and the rural end point can be maintained."
The main limitation on the system looks as if it is the number of obstructions and the curvature of the earth, hence the 100km limit.
Intel has a video demonstration of the system on the Intel Research Berkeley lab website.
The RCP, while hugely attractive to locations without connectivity, nevertheless looks like a low-bandwidth connection. Higher bandwidths and lower latencies would still need custom-designed wireless systems such as WiMax.
