Since switching to AT&T for my iPhone 3G, one the few technologically advanced features T-Mobile USA has these days that I miss is their HotSpot@Home feature. This feature allows you to make unlimited calls (for a monthly $10 fee) with a T-Mobile router and/or a HotSpot@Spot enabled cell phone using a broadband Internet connection. The technology is based on UMA which I wrote about back in 2007. The specialized cell phones incorporate WIFI with special programming which wraps a cell call into Internet compatible data packets. The downside of the technology is that it requires a special cell phone and there are very few models. T-Mobile has not even enabled the G1 with this technology, something I don't understand.
Now a new technology called Femtocells is being deployed by Sprint and is in testing with AT&T. The principle is basically the same as UMA (use the Internet to transmit cell phone calls), but it differs in one big respect, you can use an unmodified cell phone. This means I could use it with my iPhone 3G. This would be great and very exciting on two fronts. First I do get a fair amount of failed calls in my house when 3G tries to switch back to 2G and second with unlimited calling in my house I could reduce my monthly minutes. I am quite excited about using this technology and plan to call AT&T to see if I can get in on the testing (I know, good luck in making that happen), but probably worth a shot. Femtocell deployment is more problematic than UMA since the devices use the same frequencies as cell towers and the carriers need to ensure that there is no interference, however it looks like the technology is ready for prime time. Hopefully AT&T will move quickly...
To be clear, because a lot of people miss this, femtocells and UMA don't entirely overlap in terms of the problems they solve.
Femtocells have the advantage that they work with any cellphone, but UMA phones have the advantage that they can work anywhere there's an available wifi connection.
I hear many people encouraging T-Mobile to immediately give up on UMA and rush to femtocells, but plenty of people like myself have absolutely no need for a cellphone repeater but a critical need for a cellphone that can work over existing wifi.
It's important to realize that they're not entirely interchangeable; both have their places.
Posted by: Chris Carlin | January 13, 2009 at 11:59 AM
Chris,
Two points of clarification:
1. A Femtocell is not a repeater. It is a micro cell site which transmits and receives calls over a broadband connection.
2. UMA WIFI cell phones do not necessarily works on every WIFI HotSpot. The HotSpot may block IPSec ports and/or require a log on via a web page which is not gracefully handled by a phone's UMA software.
That said, I want to make clear that I don't think one is necessarily better than the other. The Femtocell addresses weak indoor signal while UMA addresses that plus the ability to make UMA calls at compatible WIFI HotSpots like Starbucks.
Posted by: Stephen Skarlatos | January 13, 2009 at 07:57 PM