Aruba Networks Monday revealed plans to bridge two wireless technologies by letting users on enterprise networks make VoIP calls over Wi-Fi and cellular networks.

The initial phase of Aruba's plan is to include code in its line of wireless LAN switches and access points to support several relevant standards for voice QoS, call admission control, and improved battery life for mobile handsets that incorporate WLAN and cellular interfaces.

Aruba's goal is to equip its WLAN infrastructure and work with handset makers, IP PBX vendors and carriers to ensure that these dual-mode handsets eventually can operate seamlessly between Wi-Fi and cellular nets for VoIP calls, according to Keerti Melkote, an Aruba co-founder.

New software and partnerships during the next 18 months will tie together enterprise and cellular nets. The enterprise phone number can be extended wherever the user goes, and the cellular number will work within the enterprise voice-over-WLAN infrastructure, Melkote says.

This seamless interconnection is largely unrealized so far, except in some early pilot tests, such as one staged in 2005 by VeriSign.

Aruba isn't alone in addressing wireless voice. Trapeze Networks recently announced an upgrade to its wireless switch software, incorporating some of the same voice and QoS standards now being supported by Aruba.

The Aruba software will implement the full Wi-Fi MultiMedia (WMM) specification (based on IEEE 802.11e) for handling such traffic as voice and video, along with a set of enhancements to minimize delay, jitter and packet loss, all of which impact the quality of a call or video stream.

The company also is incorporating the full Tspec protocol, a step that will let Aruba access points allocate bandwidth for their associated voice calls and keep QoS parameters intact as callers move from one access point to another.

A related feature, called opportunistic key caching, for clients that support either Wi-Fi Protected Access or WPA2, will speed up client authentication as access points hand off calls, minimizing the possibility that the call will be interrupted.

"The more complex WPA2 adds latencies [to the network], potentially up to hundreds of milliseconds," Melkote says. "But you need to hold it to 50 milliseconds or less." This type of key caching is designed to do just that.