Deploying large numbers of small cells requires, first and foremost, that the femtocell itself has a high degree of self-configuring capability. For home use it must offer the same level of plug-and-play functionality that consumers expect from a Wi-Fi access point. But even when they are operator-deployed, they must be simple to install. Similarly, they must include ongoing management and optimization features to ensure that they adapt to a changing network environment.

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Just as important, the network architecture itself must gracefully accommodate small cells. Existing cellular radio access networks (RANs) comprise hundreds of basestations connected to a single radio network controller or basestation controller (RNC or BSC). Integrating femtocells (in their thousands) into such an architecture challenges both existing RNCs and BSCs, as well as the interfaces used to communicate between them and the basestations.

3GPP has defined new network elements and interfaces that fit seamlessly into current mobile network operators’ RANs, while driving many of the radio resource management functions into the femtocell itself. The resulting configurations are complex, but implementation can be practical with modern multi-processor chips and DSP (Fig. 2).

LTE excels in providing extra coverage and capacity in targeted metropolitan hotspots and, in particular, indoors. Networks based on macrocells cannot deliver sufficient benefits to warrant deployment for such purposes. They are too expensive and in many cases are hamstrung by fundamental limitations of physics and communications systems.

Femtocells provide many of the answers, a fact that is recognized by organizations such as the NGMN Alliance, which has stated: “The NGMN RAN shall be designed in a way that it allows a large scale deployment of cost-optimized plug-and-play NGMN-only indoor radio equipment at a price level of commercial quality WLAN (wireless local-area network) components.”

In short, LTE needs femtocells—from day one.

Rupert Baines has 20 years of experience in technology marketing, working on commercializing many leading-edge technologies. He spent six years with Analog Devices in Boston, working on semiconductors for GSM and wireless infrastructure before managing the company’s broadband product line and holding responsibility for the industry-standard ADSL chipset. He has also worked for operators, most recently as Director of Product Development and Strategy for Atlantic Telecom, where he ran a large pan-European DSL rollout and trialled wireless broadband deployments.