AT&T 3G micro cell, some facts and figures

I was recently looking through some Cisco Live! presentation material on the web and came across an interesting presentation given in June 2012 in San Diego about femto cells. In it, the presenter provides some interesting numbers about AT&T's femto cell offering which is marketed under the name 3G micro cell.

AT&T's micro cell has been around since April 2010 and just over two years later it seems they have a network of 650,000 femto cells! Quite an impressive number in my opinion and probably the largest femto cell deployment in the world.

Looking at some additional figures from their roadmap the 3G micro cell is based on Cisco's DPH-153 product with an AT&T casing. It is capable of 4 simultaneous users which is a typical value for a residential femto cell.

In terms of maximum Tx power it is capable of 13dBm which translates to 20mW. This is actually a very low considering most residential Wi-Fi routers are capable of around 100mW (e.g. Belkin N1, Apple Airport Extreme etc).

HSPA capability is stated as 14.4Mbps for the DL, so 16QAM @ 15 HS-PDSCH codes and 1.5Mbps UL, so 10ms TTI @ 2 x SF4 E-DPDCH. Obviously the ADSL/cable has to be capable of supporting these speeds as well.

Looking at the AT&T 3G micro cell website, there is also an interesting capability that AT&T have enabled and that is for the customer to be able to configure whether the femto cell hands out to the macro or not. At first I thought this was strange but looking through the FAQ it seems this is a recommendation when a customer experiences dropped calls in their house. As the AT&T macro network does not have the capability to hand into the femto, it is possible that a user initiates a call on the femto and as he moves around the house (towards a window, garden, balcony etc) he hands out to the macro. Then as he moves back into the house the macro signal strength deteriorates and the call drops. So to avoid this happening all mobility is disabled and the user stays connected to the femto until a radio link failure occurs which typically is at a much lower point than a handover threshold.

There is a lot more information about femto cells (from Cisco's perspective at least) including the figures above at the Cisco Live! website.