Standard set to boost wireless QoS

A standard to define QoS in Wi-Fi networks is coming soon, but even before it is finalized users can expect QoS improvements from vendors that have implemented their own performance-enhancing technologies.

Wireless hardware vendor Colubris Networks says a pending software upgrade will improve its monitoring of call quality, so perceived bad quality can trigger automatic adjustments to a wireless network or alert administrators to deal with problems it has identified elsewhere on a connection.

Aruba Wireless Networks will support an informal QoS standard created by the Wi-Fi Alliance that is already supported by more than a dozen other wireless vendors. Similarly, Trapeze Networks will support the same Wireless Multimedia (WMM ) specification with its next software release, due within 90 days.

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A standard to define QoS in Wi-Fi networks is coming soon, but even before it is finalized users can expect QoS improvements from vendors that have implemented their own performance-enhancing technologies.

Wireless hardware vendor Colubris Networks says a pending software upgrade will improve its monitoring of call quality, so perceived bad quality can trigger automatic adjustments to a wireless network or alert administrators to deal with problems it has identified elsewhere on a connection.

Aruba Wireless Networks will support an informal QoS standard created by the Wi-Fi Alliance that is already supported by more than a dozen other wireless vendors. Similarly, Trapeze Networks will support the same Wireless Multimedia (WMM ) specification with its next software release, due within 90 days.

The flurry of activity surrounding Wi-Fi QoS is mainly due to the growing popularity of voice over Wi-Fi (VoWi-Fi ) and the demand that phone calls be reliable and intelligible, says Ellen Daley, an analyst with Forrester Research. A host of vendors, including 3Com, Broadcom, Cisco, Linksys, Conexant, D-Link Systems, HP, IBM, Intel, NEC and Netgear, already have certified their gear is WMM-compliant.

WMM is a subset of the IEEE RFC known as 802.11e , which vendors expect will be approved this year. WMM was created to promote use of QoS that would be interoperable among multivendor Wi-Fi gear, she says. "That means businesses can do voice over wireless pretty respectably today. They may need to upgrade when the standard comes out if they want to be standards-compliant," Daley says.

But for most users, the life cycle of wireless gear is short enough that just about the time wireless gear bought today is ready for replacement, the 802.11e gear should be ready to buy, says Craig Mathias, a principal at Farpoint Group. In the meantime, most Wi-Fi customers are getting by with single-vendor deployments of QoS-enabled devices or deployments of multiple vendors' gear whose QoS schemes have proven interoperable, he says.

The overriding challenge for QoS is that Wi-Fi is a shared medium, much as Ethernet was in the days before switching. There is just so much bandwidth and client devices have to share.

Three years ago, Bob Longhini was evaluating BreezeCom VoWi-Fi gear for door and window maker Kolbe & Kolbe, but pulled the plug on the project because of QoS issues. "We had echo and breakup in the calls, especially if there was activity from handhelds and laptop computers," says Longhini, who now is evaluating VoWi-Fi for his new employer, Jennie-O Turkey Store, a billion dollar subsidiary of Hormel.

Only workers with desperate need for mobile phones liked the early equipment, he says. "They really saw the benefit of having the phone on their hip even if they ran into quality problems," Longhini says. But things have greatly improved with a clear road map being set for QoS and many vendors already implementing early versions of the standards-bound technology.

Ideally, client devices - in the case of VoWi-Fi that means phones - would announce their bandwidth requirements and the wireless network would take steps to accommodate them, if possible. In its WMM implementation, Cisco's wireless gear (formerly Airespace) checks whether an access point in range of the phone has enough free bandwidth to accommodate the call, says Kathy Small, Cisco's marketing manager for wireless and mobility. WMM then can offer four levels of service.

WMM addresses how clients and access points communicate what they need and what they can provide, respectively, but not how devices decide whether to accept an available connection, says Partha Narasimhan, wireless architect for Aruba. Even with WMM, that is left up to individual vendors to implement, he says.

Once a phone is accepted by an access point, algorithms determine when each device connected to a single access point gets to send, with top priority voice traffic getting to send more often, says Roger Sands, vice president of enterprise development for Colubris. These algorithms were created to deal with collisions and retransmissions on Wi-Fi networks but have been fine-tuned to give voice the edge over other applications. Properly adjusting these algorithms in Colubris gear shaves at least 20 microsec off a packet's wait time, according to Colubris engineers.