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Mobile phone calls may no longer be quite so mobile - at least at home.

British mobile users are to begin experimenting with a technology which routes their mobile calls through their home broadband connection, rather than across the traditional phone network.

The technology, which is similar to that which allows computers to connect wirelessly onto the internet via wi-fi, is being trialled because of the increasing strain that is placed on the regular network as more and more people access the web on their phones.

'Femtocells' are small pockets of wireless connectivity in the home created by a base station that sits in one room, like a wireless router. The idea is that as soon as a phone comes into the house, it latches onto the point of connectivity, and any communication - for instance if the owner makes a call, or uses the web - takes place via the broadband connection.

As more and more people embrace services like music and video downloads - which involve transferring enormous amounts of data, the pressure on networks will increase, forcing operators to look elsewhere for capacity.

"There's going to be an explosive growth in data services, and the regular 3G network simply will not be able to cope as these services are rolled out," Steve Mallinson, chief executive of ip.access, a Cambridge-provider of femtocells, said.

By one estimate, a cell that would be capable of supporting 500 people all talking on their phone could be reduced to serving only 15 if the owners simultaneously using multimedia services like video downloads. Routing mobile signals over a broadband connection will also overcome another of the problems with 3G signals - that they are severely impaired by walls.

O2 will be the first British network to begin public trials of the technology when it introduces them to 500 homes across the summer. Assuming the trials are successful, the company plans to begin selling the boxes - expected to cost about £50 - in early 2009.

Carriers are increasingly looking for new ways to bolster their revenue at a time when the regular phone market is saturated. There are now 1.2 phones per person in the UK, and the home has been mooted as relatively untapped source of revenue, because of the potential to bundle services like TV and phones together.

"The home is the last unchartered battlefield for technology providers - nobody controls that eco-system," Stuart Carlaw, vice president of Mobile Wireless at ABI Research, the analyst firm, said. "At the moment you've got a wireless router from one manufacturer, and a broadband connection from another, but no-one is really tying up everything - mobile, TV, broadband, and fixed line."

The market for femtocells will grow from almost nothing to $4 billion - or about 100 million users worldwide - by 2011, according to ABI Research.

Other applications of femtocells are expected to be easier transferral of content - such as videos and songs - from other devices to phones, as well as so-called location-based services. A child's arrival home, for instance, could trigger a text to be sent to their parents, while a search on the web could be made to deliver more relevant results - in each case because the network is aware of the phone's position once it parks on the cell.

According to research by Nokia, 44 per cent of all data use on phones - for instance browsing the internet - takes place at home.

Both Orange and Vodafone said they were looking at the technology, but neither had plans to begin public trials yet.

Advocates of femtocells say that the technology will be a more practical way of routing mobile calls than, say, piggybacking on a wireless broadband connection, because not many phones yet have wi-fi chips, whereas any 3G phone can connect with a femtocell.

The only existing femtocell networks are on the Sprint network, in the US.

O2 will be supplied with its femtocell equipment by NEC, the Japanese technology giant. Motorola, the network equipment firm, meanwhile, has said that its first femtocell technology will be commercially available in the second half of the year.

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