VoWiFi standards situation

A variety of wireless standards are in the works to address the technical limitations of running voice over wireless. The following are some of the key enabling standards for quality of service, security, radio resource management and fast roaming.

802.11e

The 802.11e task group is adding QoS to the wireless standard.  The group has come up with two different types of QoS:

Prioritized QoS uses priority tagging to place different types of traffic in different queues.  Certain applications – such as voice – get priority treatment, but not a reserved or guaranteed bandwidth.  This Wireless Multimedia Extensions (WME) specification is the standard the VoWiFi industry awaits.

Parameterized QoS effectively reserves a certain amount of bandwidth for a certain stream, much like the use of virtual circuits in TDM-based switching.  Content providers need this Wireless Scheduled Multimedia (WSM) standard for such applications as HDTV.

The 802.11e draft standard has gone through general review (letter ballot) and now is being reviewed by a select group of experts (sponsor ballot).  To accommodate VoWiFi needs, interim approval of the WME portion of the standard is proceeding separately, with finalization of WME now expected in the September time frame.

802.11i

The 802.11i task group is enhancing wireless with security that is stronger and better suited to voice.  Data security mechanisms, however robust, often introduce more latency than voice can tolerate – especially if they require re-authenticating to each new access point.  Also, voice devices can be used to gain unauthorized data access.

The 11i task group has developed two new algorithms – TKIP and CCMP – to provide confidentiality, data integrity, and data source authentication.  The group also came up with a protocol for mutual authentication and key management.

TKIP is not as strong as CCMP, but can be implemented on today’s existing hardware with a firmware upgrade.  The stronger CCMP algorithm is based on the federal government’s Advanced Encryption Standard (AES). It will require new hardware.

Like 802.11e, 802.11i is in the sponsor ballot stage, but probably a bit farther along.  It is hoped that the task group can finish the standard in the July timeframe.

802.11k

The 802.11k task group is working on radio resource management that will make more efficient use of WLAN resources.  Feedback from clients will enable switches and access points to make better roaming decisions, thus providing faster and uninterrupted wireless service.  Network elements will be able to determine who is using the RF and what the quality of each RF connection is, among other things.

802.11k is just now entering the “letter ballot” stage in which it receives general review.  At this point, it is unknown when the standard will be finished.

802.11r

  The recently founded 802.11r task group is addressing fast roaming among access points.  Meanwhile, some experts think technology emerging from the 802.11i and 802.11k efforts will provide for handoffs in the 50ms range.  They say this is fast enough – human perception is in the 150ms range – to render the 802.11r group unnecessary.

Basically, protocols from 802.11k could be used by a station to discover where it should move prior to losing its current connection.  And PMK caching from 802.11i enables quick (20ms-30ms) establishment of a secure connection.  Together, these protocols allow fast, secure, seamless handoff of a VoWiFi connection among access points.

This group is still defining its scope and does not have a draft yet.