Convergence in handheld devices has been on the mobility radar as an imminent, key enabling trend. Eventually, enough integration elements will come together to allow voice/data users to seamlessly roam among Wi-Fi networks and cellular WANs.

Together, access to the two types of networks in a single device should offer higher throughput inside businesses and hot spots (Wi-Fi) and better coverage in more remote areas (cellular). When appropriately integrated, the combo should ease user pain of having to re-start sessions, reauthenticate and lose calls across network boundaries.

The key thing here is the service providers working out how to do it (and there is plenty of confusion sowed by the various groups).

The handset issue is less crucial. Handsets that can manage both worlds (handing cellular voice over to voice over Wi-Fi, for instance) are theoretically possible, but won't get made in big numbers till the operators work out how to sell them and profit by them.

The arrival of more or less "experimental" dual-mode devices is important, however, in catalysing the market by showing users - and vendors - what might be possible.

Devices appear:

As usual, Asia has beaten the rest of the world to the punch: NTT DoCoMo, Japan's biggest mobile phone carrier, has launched NEC N900iL dual-network handsets for corporate use. The phones have access to both 802.11b Wi-Fi networks and to DoCoMo's Wideband Code Division Multiple Access (W-CDMA) cellular WAN, which runs at 64 kbit/s to 384 kbit/s and which DoCoMo considers a 3G network.

Users can receive incoming calls on either the WAN, or on the corporate wireless LAN - but not yet in public hot spots.

In other vendor activity, the fourth quarter expects to see the long-awaited shipment of the Motorola CN620 handset (announced earlier this year), a dual-mode GSM/Wi-Fi (802.11a) flip phone that can make and receive voice calls on a cellular network or enterprise WLAN. The phone has been integrated with Avaya's Enterprise Seamless Mobility infrastructure, co-developed with WLAN vendor Proxim, and the phone is to be available from Avaya resellers (as announced in July).

The infrastructure will reportedly allow CN620 users to roam between cellular and corporate voice-over-WLAN networks, supporting Avaya PBX-phone features even when out of the office.

Finally, the Nokia 9500 Communicator, which supports 802.11b and EDGE cellular connections, is currently available in Europe. It is due to ship in the US in the first quarter of 2005, according to a company spokeswoman.

However, the Wi-Fi support is focused more on data applications and, to date, no integration has been done to enable seamless roaming without session interruption across networks. Nokia indicated that would be left to the work of third-party software.