ZinWave, a startup based in Cambridge UK, is planning to launch a system that will improve wireless coverage inside buildings - using the outmoded fibre-optic cables that are already installed.

By the end of June, ZinWave said it will deliver base stations that can send wireless signals over installed multi-mode fibre to give blanket coverage inside buildings for GSM, 3G, Wi-Fi and private radio systems such as Tetra. "We will sell these in the UK, and very quickly in the US too," said Mike Baker, chief executive of the firm.

Distributed antenna systems (DAS) improve the coverage of radio within buildings by centralising the base stations in wiring closets, and distributing the antennas throughout the building. Most systems use a fibre-coax network, which has to be purpose-built, but Zinwave claims its proprietary technology lets it use installed multimode fibres, instead of having to pull new ones through the building.

"The vast majority of buildings have multi-mode fibre," said Baker. These fibres were put in for old-fashioned networking backbones, and carry a 100MHz signal for 100baseF Ethernet signal up to 700m, but until now, they have had a much shorter range for the higher frequencies at which Wi-Fi and 3G operate.

DAS systems sold by companies like antenna specialist Andrew and MobileAccess (read a case study of Lehman Bros DAS system) use more expensive single-mode fibre whch often has to be pulled specially.

"Currently, 1GHz signals tail off at a limit of 50m on multi-mode fibre," said Martin Cassidy, senior vice president of business development at ZinWave. "Our technology allows signals at least up to 2.4GHz to travel at least 550m." The 550m distance is significant, explains Baker, since it complies with building standards

Zinwave would not talk about its technology, but there is plenty on the web about it. Radio-over-fibre has been developed since 2000 by the Friday project (fibre radio for in-building distributed antenna systems) led by University College London, with Cambridge University, Agilent and Remec. The project demonstrated (PDF) the ability to carry 802.11b signals 1km over "worst case" fibres in 2003, and Dr David Wake of UCL has published an interesting paper (PDF) on the principles of radio over fibre.

Sponsored by the UK government's Link scheme which supports R&D, and forming part of the Optical Systems for the Digital Age programme, Friday concluded in 2003. "The project successfully developed techniques for transmitting wireless signals over multimode optical fibre and these have been used in demonstrator hardware for the distribution of IEEE 802.11B/G wireless local area network (WLAN) signals," says a report at the home site of government backed UK research in the field, Photonics Focus. "This technology is now being exploited commercially by ZinWave Ltd."

The approach could be useful in removing one main objection to DAS systems (the expense of the fibre), however, it seems most likely that ZinWave will have to form partnerships with Wi-Fi switch vendors and structured cabling providers in order to reach customers.