In his “Do you know where your femtocell is?” commentary on AT&T’s 3G Microcell rollout, Paul Callahan says that “GPS is fast becoming a requirement for femtocells” (Airvana FemtoHub, Oct 6). That’s certainly true in the US market, but the global picture is very different.For CDMA networks GPS is part of the system - it’s a pre-requisite. But one of the key reasons why CDMA failed to take off across the world was its reliance on GPS, which is owned and controlled by the US Government. For UMTS, the 3G network choice of most operators around the world, GPS is not required.
With femtocells, operators need to meet national location regulations for emergency calling. Customers want to know that their emergency call will result in an accurate response. And several operators have told me that they see a robust emergency location system as a moral obligation, not just a regulatory one.
In reality there are many ways that a femtocell’s location can be determined. These provide different levels of granularity, complexity for the consumer, device cost and probability of success. There are pros and cons for each method which I’ll cover on another day.
Location determination methods employed by femtocells:
- GPS
- 3G and 2G Network Listen Mode: where the femtocells listen to surrounding macro cells and determine their location based on the location of these cells.
- Using the Broadband Access Database – where available (market by market) this allows a location lookup based on IP Address.
- Customer Declaration – currently used in European femtocell deployments to supplement Network Listen, where the customer takes responsibility for registering the installation address.
