The most common type of femtocell is based on 3rd Generation UMTS mobile phone system, which evolved from GSM. This 3G system has been enhanced to include high speed broadband data (called HSPA) at rates of 21Mbps and beyond. A typical 3G residential femtocell is shown on the left.
3G femtocells like this are compatible with operators such as T-Mobile and AT&T in the US, SoftBank in Japan and most mobile operators in the rest of the world. It is this wide adoption of the GSM family of standards (well over 90% of all mobile phones are GSM capable) that makes this the most attractive market for vendors. It also enhances the coverage and capacity of the latest mobile phones in more contained locations.
As with other femtocells, these units are similar is size and power consumption to a WiFi access point - typically the size of a paperback book and consuming around 5 Watts. They connect to your broadband internet modem, using an Ethernet cable and provide very localised, low power mobile phone service in your home or office. Typical maximum RF power levels are around 50mW, less than many cordless phone systems. They are compatible with any 3G phone or broadband data dongle and can support up to 4 simultaneous voice calls and/or many data sessions.
The limiting factor tends to be more around the capacity of the wireline broadband internet connection (especially the uplink), which is one reason for determining the maximum voice capacity at 4 simultaneous calls.
3G Residential Femtocells offer:
- Up to 8 or more simultaneous voice calls/data sessions
- Shared data capacity of up to 21Mbps between many mobile broadband data devices
- Overall lower costs to the network operator than building more outdoor cellsites, which can be passed on to customers
