Bringing the femtocell outdoors

To date, the discussion on femtocells has always centered on indoor coverage—providing a better signal and more capacity for a handful of people at home or at work. But this week ,Ubiquisys introduced an outdoor femtocell that would serve the same small number of subscribers but over sizable distances.

The difference between and indoor and outdoor femtocells isn’t power or processing capability; it’s merely range, said Keith Day, vice president of marketing for Ubiquisys. It doesn’t matter if the subscribers are in the same room or mile and a half away, the same architecture that provides a private home connection could be used to support a public wide-area network. To that end, Ubiquisys had revamped its standard indoor femtocell with a software upgrade to turn it into what is essentially a miniature outdoor base station.

Calling it a wide-area femtocell, Day said the box is not some scaled down macro-cellular network platform, such as a micro-or pico-cell. “Unlike the macro network, it’s not engineered in place,” Day said. “You switch it on and it immediately and constantly analyzes the landscape for the macro network and then optimizes itself for the conditions it encounters. It is always subsidiary to the macro network.”

In fact, that’s exactly what an indoor femtocell does, monitoring network conditions and reconfiguring itself not to interfere with the prevailing wide area network or neighboring femtocells. That allows an operator or its customers to deploy the outdoor cell much like they would an indoor cell, placing it wherever they please without having to reconfigure or redesign the entire nearby network topology. And like an indoor femtocell, it can be hooked up to a broadband connection, which will backhaul traffic to operator’s core network. The 20 to 30 watt device can deliver a clear voice signal up to 1.5 km, and can deliver HSPA capacity within 700 m, Day said. But the platform can only support 16 simultaneous calls.

“In rural areas, 16 simultaneous calls in a village is pretty good for an operator,” Day said. It’s for those types of deployments that Ubiquisys is primarily marketing the new femtocell. It already has a win for the device Softbank, the Japanese UMTS/HSPA operator that helped Ubiquisys with the development of the platform and is already deploying it as a means of extending its 3G footprint to out-of-the-way places.

But Day added that the wide area femtocell could eventually be deployed in urban settings, used as a means to expand capacity rather than coverage. HSPA has a more limited range on the femtocell—only about 700 m—but it’s perfectly adequate for offering spot capacity in highly trafficked areas, Day said.

Many experts in the industry believe that some type of smaller cell architectures are the future of the network. The amount of additional spectral efficiency that can be squeezed out of wireless technologies is rapidly dwindling, and without new spectrum operators will be forced to reuse their existing spectrum more and more if they want to support the higher and higher capacities customers are demanding. Femtocells have the advantage of being cheap, easy to deploy and self-configurable, eliminating the need for massive scale network planning.

The Femto Forum has long promoted the idea of the femtocell not as a means of filling in coverage holes, but as fundamentally new way of architecting the cellular network. If femtocells can be brought out of the home and into the public square, as Ubiquisys is proposing, operators may be able to shift the burden of capacity of the costly macro network.