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Nokia, the world largest handset maker, has begun testing technology in a Finnish city that lets users to make calls on both cellular and Wi-Fi networks and switch between networks without interruption.

Nokia's new 6136 phone automatically transfers voice or data connections from GSM networks to Wi-Fi when the device recognizes a compatible wireless network, Doug Dawson, a spokesman with Nokia, says. And, vice versa, when users make a call or data transfer via Wi-Fi and step out of the Wi-Fi network's coverage area, the connection is transferred to a GSM link without interruption.

Around 50 people in Oulu, Finland, are testing the new service as part of a two-month pilot initiated by Nokia in cooperation with Finnet and the City of Oulu. The city has been offering free access to Wi-Fi hot spots since last year as part of a project to spur wireless Internet service.

UMA Technology

The Finnish vendor is one of several vendors, including Motorola, to offer handsets with UMA (Unlicensed Mobile Access) technology, which enables a "seamless" handover of voice and data connections between GSM mobile and Wi-Fi or other local wireless networks.

BT Group, which launched one of the world's first UMA commercial services last year using Bluetooth technology, plans in the third quarter of this year to extend its service to Wi-Fi networks with Motorola's A910 UMA-enabled phone.

TeliaSonera in Sweden and Finland and T-Mobile USA plan UMA service in the coming months.

UMA allows consumers to enjoy better indoor coverage and lower calling charges when within range of a compatible Wi-Fi terminal, by having it carry their calls over the fixed broadband network using VoIP (voice over Internet Protocol) technology. UMA handsets such as Nokia's 6136 create a secure tunnel to the network operator's UMA Network Controller, which uses the handset's SIM (subscriber identity module) to authenticate the caller with the operator's billing system just as it would over a cellular network.

The new Nokia 6136 phone, which Nokia announced in February, will be available in the third quarter, according to Dawson. The phone, to cost $350, will be equipped with a 1.3 megapixel camera and removable micro SD format memory card.