The Wireless Propagator: External Standards to Address Internal VoWLAN Complexity

Talking on a mobile handset. For a concept that seems so familiar and commonplace, the underlying infrastructure--and associated complexity-- required to support VoWLANs (voice over wireless LANs) has been somewhat intimidating. Helping to tackle all the related issues and bring...

September 22, 2005

5 Min Read
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Talking on a mobile handset. For a concept that seems so familiar andcommonplace, the underlying infrastructure--and associated complexity--required to support VoWLANs (voice over wireless LANs) has been somewhatintimidating. Helping to tackle all the related issues and bring some clarity tothe marketplace are standards bodies such as the Wi-Fi Alliance and the IEEE(Institute of Electrical and Electronics Engineers). This week, we'll look atwhat the Wi-Fi Alliance is doing.

Formerly WECA, the Wi-Fi Alliance was formed in 1999 to provide a basicinteroperability testing ground for the new IEEE 802.11 equipment flooding themarket. Initial standards focused on 802.11b, then on 802.11g and 802.11a,with testing along the way for WEP (wired equivalent privacy) support. In 2002,the alliance developed WPA (Wi-Fi protected access) as an interim butcompatible solution for the still developing IEEE 802.11i security standard. Sincethat time, the Wi-Fi Alliance has become more expansive in its scope.

Early in 2004, the alliance formed the Voice over Wi-Fi task group. Made up ofwireless infrastructure, handset and test equipment vendors and headed up byMeru Networks' Chief Software Architect Joe Epstein, this group has focusedon two cases: home and enterprise. Similar to the division between WPA pre-shared keys (home) and WPA with 802.1X support (enterprise), the home caseis simpler because only one AP (access point) is required, so little emphasis isplaced on roaming capabilities. It will include some level of QoS (quality ofservice), likely in the form of WMM (Wi-Fi multimedia) and perhaps WMM-SA (Wi-Fi multimedia scheduled access). The average number of traditional handsets inthe home case ranges from two to four, so security provided via manuallyentered WPA pre-shared keys should be enough. The MRD (marketingrequirements document) for the home case has been completed, and the Voiceover Wi-Fi technical task group is now generating the methodology andproducing test cases.

With some of the groundwork laid, the home case has been expanded andextended into the enterprise case, where issues such as roaming and batterylife become more significant. Because pre-shared keys have limited scalability inthe enterprise, network-based authentication schemes will have to beconstructed to accommodate the cramped or reduced keypads found onVoWLAN devices. The Wi-Fi Alliance is concurrently working on the "SimpleConfiguration Security" concept, which ideally will draw on the features found inBroadcom's SecureEasySetup and Buffalo Technology's AOSS. This push-buttonsecurity mechanism allows even headless devices to create secure connectionswithout a keyboard and monitor. The Voice over Wi-Fi technical task grouphopes to complete the enterprise case in the first half of 2006.

Similar to how WPA was an initial subset of IEEE 802.11i, WMM is a subset ofthe almost completed IEEE 802.11e. WMM is a QoS standard that specifies fourlevels of priority for traffic, of which voice is the highest. Certificationbegan last September, but the uptake by VoWLAN handset manufacturers hasbeen disappointing. Cisco, which just released new firmware for its enterprise7920 VoWLAN handset in June, did not include WMM support. SpectraLinkincluded WMM support in its latest release, but the company will continue topitch its own proprietary SVP (SpectraLink Voice Protocol) in the interim untilenterprises support WMM throughout their infrastructure.Also available are admission control and unscheduled APSD (automatic powersave delivery). The first prevents the number of calls and phones on a single APfrom overwhelming its capacity. APSD works by having the device sleep duringtimes of non-communication, waking up only to send or receive traffic on a"scheduled" basis. In an attempt to match the talk and standby times ofcellular phones with each generation of WLAN chipsets, wireless chip vendorsAtheros and Broadcom have placed a strong emphasis on power usage.Coming up in the first half of 2006, the Wi-Fi Alliance will be certifying WMM-SAwith the equivalent APSD. Scheduled access is deterministic; therefore, trafficcan be planned rather than contended for, as is the case with current accessschemes.

Last fall, the Wi-Fi Alliance created the WCC (Wi-Fi/Cellular Convergence) taskgroup, which has been working on a standard relating to combination Wi-Fi andcellular products. Given the fact that mobile carriers have been testinghandset interoperability for years, the group is coordinating with the CTIA(Cellular Telecommunications & Internet Association). Until now, the alliancehas tested wireless network cards and access points; the move to convergedhandsets and non-Wi-Fi wireless service such as HP's iPAQ PocketPC h6315 willprove challenging. Wireless data communication test solutions provider AzimuthSystems, working closely with both the Wi-Fi Alliance and the IEEE, hasdeveloped a testing solution that enables testing labs and large organizationsalike to verify roaming times not just between access points but also fromWi-Fi to cellular and back. Certification should start early next year with asimple SOHO (small office/home office) case and then proceed to the morecomplex enterprise case thereafter.

Unlike data over wireless networks, it's clear that voice is much moredemanding in its QoS, security needs and battery usage patterns. Homenetworks, without the roaming and authentication concerns, will likely be able toadopt this kind of voice mobility much sooner than enterprise networks. Whileenterprises have had to perform network evaluations before embarking onwireline VoIP, wireless network planners should take the time to build aninfrastructure that will support voice. Doing so will enhance the reliabilityand performance of data networks, too. Enterprise wireless networks seekingto provide VoWLAN will have to wait and subscribe to a host of standards, fallback on a single vendor such as Cisco or work with any number of the vendortested and integrated solutions available today.

Frank Bulk is a contributing writer to Network Computing Magazine covering wireless and mobile technologies and works for a telecommunications company based in the Midwest.

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