Cable giant NTL is to field test a 100Mbits/sec broadband service for homes from March at Ashford in Kent, the company revealed today.

The trial, which we flagged last week, is basically of a bandwidth-on-demand system – you get 100Mbits/sec when you need it, for instance to download movies.

NTL staged a demonstration at a show flat in Pimlico, London, in which the system delivered three high-definition TV streams simultaneously, leaving bandwidth to spare for other internet uses.

Kevin Baughan, NTL's director of network strategy, pointed out that cable has far more capacity than ADSL+, the latest version and fastest broadband technology to use existing phone lines. That can deliver at most 20Mbit/sec to users close to the exchange, but speeds fall off rapidly with distance because there is no way to boost the signal.

NTL takes fibre with virtually unlimited bandwidth to neighbourhood boxes, where the signals are transferred to a twin cable known as Siamese because it is 'joined at the hip'. One half is coax cable, carrying about 3Gbits/sec, and the other carries three copper twisted pairs for telephony. The latter gives NTL an extra option of delivering ADSL2+ to the home.

But the 100Mbit trial uses the coax half, the new DOCSIS 3.0 cable-data standard, and a wideband modem from Arrisi with technology that segments the available bandwidth into broadcast TV, Video-on-demand, downloads, and ordinary internet traffic. For more details and pictures see here