Karl Marx said that history is like the weather--many people talk about it but few do anything to change it. It is not quite the same case with WiFi/cellular converged services, but we do note that the there is a certain lack of proportion between the volume of talk and the number of announcements about convergence and what is actually available in the field, at least so far. Last time we checked, only a few convergence services have been commercially launched. Example: BT Group offers a service in the U.K., but roaming from a cellular network onto a WiFi network is limited and allowed only on the user's home WiFi network.
T-Mobile International may redress this imbalance. The company will start offering a converged WiFi/cellular service this summer, using network equipment from Nortel Networks. The service will first be available in Germany. It will be a rich and versatile service. T-Mobile customers will be able to use laptops and PDAs to use services such as video calling, video conferencing and IM without disruptions, even as they move between WiFi and cellular networks. Their connections will not be dropped, customers will not have to do anything to assure continuation of connection and they will be able to use one phone number regardless of which network they are near.
Customers will be able to connect to any of the 6,000 T-Mobile and T-Com hotspots in Germany but will not be able to use the service through other hotspots. Customers will be able to connect over 3G, EDGE, GPRS and WiFi. In addition to PC cards and converged handsets, customers will also be able to connect by using laptops from Fujitsu-Siemens which come with WiFi and HSDPA technology. The plan limits downloads to 5GB on the cellular network and 200 hours of use on the WiFi network. Note that BT and other operators involved in convergence support UMA, while the T-Mobile's system is based on SIP.