Will mobile calls take WLAN route?

Voice over IP (VoIP) and IP telephony are already widely supported by companies' wired networks, though many IT managers remain sceptical about the benefits and cost savings commonly attributed to converged voice and data systems.

Channelling voice calls over wireless data networks is a relatively new proposal, however, and one that has just been given a substantial boost from Motorola, Proxim and Avaya. They are pooling their resources to research and develop reliable, cost-efficient wireless communication solutions targeted at corporate buyers. Their first products are due to ship in 2004.

The idea is to give roaming staff access to cellular voice and data networks, as well as public and private WLANs, from a single mobile handset that incorporates both GSM and 802.11 capabilities. Motorola will develop dual-mode GSM and 802.11 handsets able to transfer calls from one type of network to the other. Proxim will supply voice-enabled 802.11 access points, and Avaya will supply the VoIP switches and telephony software needed to link the wireless part of the infrastructure to converged systems.

According to Avaya's vice president of marketing, Jorge Blanco, such solutions could result in significant cost savings by consolidating access devices and reducing the burden of network management.

There is also potential to reduce company telephone bills, if staff are able to use their mobile handsets to make VoIP calls either over public WLAN hotspots or whenever they find themselves within range of their own firm's access points.

But this depends very much on the establishment of interconnection agreements between mobile operators, hotspot providers and corporate users, something which Motorola, Avaya and Proxim do not appear to have yet considered.

"The billing aspect represents a big challenge, because handover between WAN and corporate WLAN will require specific interconnect agreements that define where one call stops and the other starts," said Jason Chapman of analyst firm Gartner. "If the mobile operators set up [such agreements] with firms, they are in effect agreeing to hand over some of their revenues so they will be reluctant to move quickly."

Therefore, mobile operators will certainly want to provide integrated solutions to corporates themselves in order to maximise their own revenues.

Another difficulty is that the 802.11b access points that currently dominate the WLAN market up are not up to the job of carrying voice traffic. Faster, more reliable 54Mbit/s 802.11g and 802.11i equipment will be required to offer better quality of service. But the IEEE has not yet sanctioned final standards for these two specifications.

One more hurdle to consolidated systems is the extra battery life that will be required to power two communications chips in the dual-mode handsets.

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