WFA certification programs to focus on improved support of voice calls over Wi-Fi

By Dorothy Stanley, Standards Architect
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This week, after several years in development, WFA announced (see the availability of the Wi-Fi CERTIFIED™ Voice Enterprise and Wi-Fi CERTIFIED™ WMM-Admission Control certification programs. The goal of these programs is to provide interoperable, standards-based mechanisms that enable improved voice performance in Wi-Fi enterprise networks.

WHY is this important?

Voice connectivity is one of the last barriers in many enterprises to fully "cutting the cord" and going to all-wireless infrastructure (see ). As client devices support the features in these new features, enterprises will have additional tools to improve voice performance on WI-Fi networks.

WHO is involved?

Wi-Fi Alliance – 2 new enterprise market focused certification programs

WHO else is involved?

Aruba Networks and other vendors with products in the WFA test-bed for the two new certification programs

WHAT are the technical components of the programs?

The technical components of the Voice Enterprise program include features from several published IEEE amendments including:

Std IEEE 802.11k™-2008 Radio Resource Measurement – Notably the Neighbor Report and Beacon Report capabilities, which enable a client device to gain information about its neighboring APs, and to report to an AP the Beacon information that the client is receiving.  Thus the client device can easily get more information about the surrounding network infrastructure. And the network infrastructure gains information on the radio network, as observed by the client device. The goal is to enable faster, better AP selection of a voice capable AP by a client device.

Std IEEE 802.11v™-2011 Wireless Network Management – Notably the BSS Transition Management service. BSS Transition Management enables an AP to request that a client device transition to another AP device, or to one of a set of other APs. This is useful for load balancing applications, for example moving a client to an AP with fewer active voice calls.

Std IEEE 802.11r™ Fast BSS Transition - enables fast, secure transitions for a client device, from one AP to another AP. The resulting behavior is similar to that achieved with opportunistic key caching. 11r introduces the concept of a "Mobility Domain". In a Mobility Domain, the initial EAP authentication generates keying material that is used to create a PMK-R0 or "top level" key, from which PMK-R1 keys are derived. Separate PMK-R1 keys are used by each AP in the Mobility Domain to derive Pairwise Temporal Keys (PTKs) to secure the wireless link to a given client. The mechanism used to deliver the PMK-R1 keys to each of the APs in the Mobility Domain (as needed) is vendor specific. Thus all APs in a Mobility Domain must be from a single vendor.

11r also includes the "Fast Transition Resource Request Protocol", a pre-association frame exchange used to request resources. Thus the transitioning client device can request resources for a voice call, essentially as part of its process of connecting to a new AP – and if the resources are not granted by a given AP, abandon that AP, and begin 802.11 authentication / association with a different AP.

Technical components of the WMM-Admission Control certification program include features from Std IEEE 802.11e™-2005 MAC Quality of Service Enhancements - Including traffic stream bandwidth management at an AP.  The WMM-Admission Control certification is a pre-requisite program for WFA Voice Enterprise, and is an extension to the existing WMM services. With WMM-Admission Control, an AP admits only traffic streams that can be supported by the AP. Thus an AP with WMM-AC enabled will admit voice calls only when the network can accommodate the call.  Admission Control is used for voice and video priority streams, and is effective only when both the client and the AP support WMM-AC.

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