Mobile operators join in the battle for home hubs

COMPETITION BETWEEN OPERATORS could prevent future 3.5g and 4g networks from achieving optimal performance.

HSPA+ and emerging LTE 4G cellular links will quickly hit the limits in terms of the data they can carry per megahertz of bandwidth, and with little available spectrum the only way to increase capacity and real world speeds is to reduce the size of cells.

This is the idea behind femtocells, which in their first generation are simply home or office base stations that improve inhouse cellular coverage and provide near maximum data rates because users are so close to the antenna.

They are also great for operators because they can increase user density, offload radio traffic from the wider network and use the site's own fixed broadband line for the backhaul link to the wider network. Vodaphone is the first UK operator to introduce femtocells, quietly launching a service called Sure Signal, which is expected to be ramped up this year.

Charges for the base station vary from nothing to £50, depending on contract, but in any case the cost is heavily subsidised.

Clever network management allows femtocells to operate without contending with neighbouring ones or with the wider macro-cell network. The optimal configuration, so far as the network is concerned, is to remove the distinction between the two and allow femtocells to serve passers-by as well as local subscribers, producing a massive grid of pico cells.

This is similar in principle to what BT's Von system does with WiFi. A subscriber allows public access to an access point in return for the right to use the links of other Von users.

But femtocells seem unlikely to go public in this way in the short term, let alone reach the optimum of a single pico grid.

Rupert Baines, vice president of marketing for Picochip, a Bath-based company that makes the chips used in most current femtocells, points out that the operator who installs a femtocell is likely to 'own' all the people living or working at the location.

This means operators will fight tooth and nail to get their network into the home for fear of losing subscribers to rivals. The result could be not one set of femtocells but several attached to different networks coexisting in the same area. And the fixed network could add another constraint on performance. Current BT DSL lines can not support anything like the 42Mbps theoretical maximum downlink speed of an HSPA+ femtocell link.

The fun and games will not stop there. Cable, telephone and satellite companies, and even PC and TV manufacturers have been angling for years to own the home gateway, the communications hub that all assume will be a feature of future homes.

Combined WiFi routers and femtocells were already on show at the Mobile World Congress (MWC) this week. There is no reason why set-top boxes should not be thrown into the mix. So femtocells are bringing yet another player, mobile operators, into the battle for the heart of the digital home.

This is fine as far a Picochip is concerned. "The more companies who are interested, the more customers there are for our products," said Baines.

Picochip announced two new HSPA+ femtocell systems-on-a-chip with an integrated software suite at the MWC, and a reference design for an LTE femtocell co-developed with Continuous Computing and Cavium Networks.

Baines said that Picocell has sold more products already this year than in the whole of 2009, showing that momentum is building for the technology. µ