Verizon's Wireless Network Extender

Femtocells are edging closer to the office. The technology provides a path to fixed-mobile convergence, in which one wireless phone can be used in the office and on the road.

Femtocells are small cellular base stations that are installed in homes and offices and connect to a service provider's network via broadband. They work with any kind of cell device and use the same standards and protocols as external "macro" cells. When users are indoors, their cell phone or data card connects to the femtocell instead of searching for an external base station. Calls are smoothly handed off between inside and outside cells as the user moves.

New standards, increasing vendor support, and new heavier-duty networks make femto more suitable for enterprise use. The questions now are how businesses will integrate femtocells, and how quickly. The answers will depend on the emphasis operators place on business deployments and how attractive they can make the price.

Although femtocells are simple architecturally, enterprise femto networks aren't. For network operators, management of femtocells, including cell provisioning and traffic prioritization, must be handled carefully. Customers must plan femtocell placement to avoid interference and may need to address issues with Wi-Fi and finicky VPN configurations in their existing networks.

Furthermore, the costs of a large-scale deployment will be much higher than a consumer plan, because businesses require higher quality of service from their Internet service providers, and providers must be able to carry more data as well as voice.

Loud And Clear
This makes femto very different from Wi-Fi-enabled handsets, which require not only the Wi-Fi radio, but also support of specific cellular tunneling protocols such as defined in Unlicensed Mobile Access (UMA). There are also some similarities between femto and Wi-Fi: A femtocell's backhaul connection is via the customer's Internet connection, be it DSL, cable modem, T1, or fiber. The femtocell uses the Internet to communicate with a femto gateway managed by the ISP. This central gateway connects to the cellular operator core network, and the femtocells look like so many additional base stations on the operator network. A central configuration server performs management and security functions, including femtocell configuration.

Femtocells transmit at very low power levels -- typically, tens of milliwatts versus multiple watts for a large cell -- so the same frequencies can be reused from one building to the next, and fewer users share bandwidth. This might not make much difference for voice quality, but it will mean a huge difference for data throughput. With mobile broadband traffic expected to more than double every year for the next five years (as projected in Cisco's "Approaching The Zettabtye Era" white paper), any capacity relief will be crucial to keep WANs humming.

New standards will aid network interoperability. Mobile specifications group 3GPP recently approved a standardized core network interface that's based on existing circuit-switched and packet-switched base-station-to-core-network standards. This interface will standardize communications between femtocells and the femtocell gateway.

Industry associations such as the Femto Forum also are weighing in. Femto Forum members have agreed to use the Broadband Forum's TR-069 CPE WAN management protocol -- the same protocol used for DSL equipment -- to manage customer femtocells in real time.

(click image for larger view)