Question: Which is smaller, a pico or a femto?

Answer: A femto, which is one-quadrillionth, while the larger pico is one-trillionth.

It follows then that femtocells are deployed mostly in residential settings, while the more robust picocells are deployed in larger buildings. Both femtocells and picocells are mini base stations that connect to the Internet to improve wireless reception.

The key difference is that femtocells are user-deployed, said Aditya Kaul, senior analyst with U.K.-based ABI Research. Consumers hook up the femtocell to their DSL or broadband connection. Picocells are more rugged and deployed by mobile operators to improve reception in large buildings.

A study by ABI Research found that the top picocell vendors worldwide are: (1) ip.access, based in the UK; (2) ZTE in China; and (3) Huawei in China.
Kaul said the technology is basically the same for picocells and femtocells, which both provide an interface among cell phones, cell towers and the Internet. The cell phone talks to the antenna in the base station. The base station uses the Internet.

"Femtocells solve a backhaul issue for (mobile) operators," Kaul said. "Operators don’t need to provide a dedicated connection."

Andy Tiller, VP marketing at ip.access, said T-Mobile is the company’s largest picocell customer in the United States.

"T-Mobile installs (picocells) in large buildings, often where there’s a problem in a particular part of the building such as underground car parks," Tiller said. "They also put them in their own T-Mobile stores."

For more on the costs/benefits of femtocells, see this December 2008 CT story.

Besides femtocells and picocells, there are other technologies to improve cell phone reception in very large buildings. Kaul said repeaters are deployed in large public spaces such as shopping malls, stadiums and airports. Repeaters borrow coverage from an outside network.

Distributed antenna systems (DAS) are used in buildings of 500,000 square feet or more. They are basically a base station installed in the basement with antennas running along the building. DASs generate their own coverage, Kaul said.

– Linda Hardesty

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