UMA (Unlicensed Mobile Access)

Being a fan of all sort of wireless technologies, the recent announcement by T-Mobile USA to start UMA service grabbed my attention. The service has been rolled out as Hotspot@Home. Not long ago I thought UMA is just another dream tangled in technical and regulations problems and would not see the light for some time. So this surprised me and I started digging around, being soon redirected to http://www.umatoday.com/. There I quickly learned actually the leading carrier in UMA deployments is not T-Mobile, but Orange, and - funny - the service has been available in Poland since April 2007 as Unifon.

UMA is an abbreviation of Unlicensed Mobile Access, another TLT (Three Letter Technology), being recently renamed to GAN or Generic Access Network. Whichever acronym we take, the concept itself is really cool. In short, by using dual mode (GSM + WiFi) handsets, it allows a handset to connect to your home / office WiFi hotspot instead of connecting to a cellular tower. It does not require any setup, software, nothing but a UMA - capable handset (currently not many can do that, but the number is growing). In return you get basically two things: better coverage when being at home (provided your home is well covered by WiFi) and cheap calls. Myself I like both features, but actually the coverage is a breakthrough for me, as living in a remote deep valley I have extremely poor cellular reception, very often being just out of the network, when I am not close to the big window on the first floor).

Once the phone is paired with a WiFi access point, the handoff is seamless. Actually you can start a conversation on a WiFi network at home, get into a car and drive away, the call will not be dropped, only the connection will go via the usual GSM radio network. The only noticeable difference is the green circle meaning WiFi connection is active, instead of an antenna symbol (when GSM connection is active) left to the signal bar indicator (see the Nokia 6136 picture above). Everything else works the same as you were using a standard cell phone. Just dial a number and talk. Or write an SMS or reach for a WAP page (there is even the "G" indicator standing for active GPRS session...). But technically things are substantially different. Normally when a phone is connected to a cellular tower, it establishes a GSM (or UMTS) radio link, registering itself with the tower and the signal once reaches the tower goes down the private telecommunications link of the service operator. On the other hand when a UMA phone connects to a WiFi hotspot, it establishes a secure (IPSec) tunnel through the public Internet. The tunnel starts at the phone and ends at the mobile carrier's UMA gateway, so from the MSC (Mobile Switching Center) perspective it looks like an ordinary cellular handset.

This concept brings a lot of advantages to the carriers. Suddenly it is the subscribers who build and pay for the radio access network - instead of expensive, carrier-founded base stations, UMA makes use of inexpensive, subscriber-founded WiFi hotspots and free Internet. It relieves the radio network congestion, increasing the network capacity at virtually no cost. And - as in my case - it brings network coverage where there are no towers, that should be especially interesting for carriers who do not have broad coverage.

For users there are cheaper calls - most carriers offer either flat rate UMA calls across the entire network or significant discounts. There is an interesting benefit for international roamers - if you are abroad and happen to have a WiFi network access (most cheap hotels offer one for free, luxury hotels charge a lot - like for bottled water :P), you log in direct to your home network as you were in the home country, so no roaming charges.

UMA has been included in the 3GPP Release 6. While most 3G networks are operating at Release 4 level now, this bodes well for the future. With the convenience of personal cellphone in a pocket bridged with Internet (flat / free) call rates, the service seems to be the carrier's primary weapon targeted at Skype et al. Especially when the voice quality (given more available bandwidth on WiFi network) is upgraded as well, who would bother to launch Skype on the PC when you could just use the phone to make a call?