Air Time: Running on Empty

The appeal of Wi-Fi is simple: no more Ethernet cables. Freedom from theshackles of copper wire is not just convenient, it's downright liberating. Butwalk into an enterprise conference room, and what do you see? The Cat5Ethernet cables may be gone, but step carefully, lest you catch your shoes onsomeone's power cable snaking its way across the floor. So much forliberation.

I recently moved into a newly renovated building on the campus of SyracuseUniversity. Given my interest in wireless networking, I lobbied hard for ahigh-capacity, dual-band WLAN infrastructure. Coupled with a generous helpingof conference rooms, both large and small, the wireless infrastructure is acritical element in our effort to encourage collaboration. Although theenvironment has been well received by students, faculty and staff, everyone hasone major complaint: not enough power outlets. Despite marketing claims ofleading notebook computer manufacturers, most of our wireless-intensive userscan't make it through a typical meeting without plugging their power brick intothe wall.

Limited notebook battery life is often viewed as an inconvenience, but thenomadic nature of notebook users makes the situation tolerable. For users ofemerging Wi-Fi-enabled VoIP and smartphones--so-called converged mobiledevices--however, limited battery life is an absolute showstopper. That problemis getting some much-needed industry attention, most recently in the form of anew Power Save Certification from the Wi-Fi Alliance. This new element is partof the alliance's broader WMM (Wi-Fi Multimedia) program, which alsoaddresses key issues related to quality of service.

Though the original 802.11 standard included provisions for conserving batterypower, the system has not been widely adopted, in large part because itsarchitecture results in a significant performance hit and additional networkoverhead. In addition, legacy power-savings mode is controlled by networkinterface drivers rather than by applications, a one-size-fits-none approach.For converged devices supporting real-time voice applications with strictlatency requirements, legacy 802.11 power-savings technology simply isn'tworkable.

To function properly, WMM Power Save needs to be implemented on APs(access points), in wireless device drivers and within applications running onthose devices. Wireless stations and APs negotiate power save when thestation associates with the AP. The system leverages the priority queuesdefined in WMM and 802.11e while also maintaining backward compatibility withlegacy 802.11 power-savings mode.

Because WMM Power Save requires tight integration between applications andwireless drivers, it is likely that initial applications will focus onapplication-specific mobile devices, especially VoIP phones. The Wi-Fi Alliancesuggests that such devices will realize enhanced power efficiency of between 15and 40 percent. However, to be successful, this "standard" will need to bebroadly supported by chipset and AP manufacturers. The Wi-Fi Alliance is off toa good start in that regard, with a number of products already certified. Thelist includes AP reference designs from Atheros and Broadcom, Cisco's Model1231 abg AP and several client radio modules from Broadcom, Conexant, Ralinkand Winbond.

Purists might argue that this is yet another example of an industry associationencroaching on turf that traditionally has been the domain of standards bodies.To a certain extent, that's true. But as basic 802.11 functionality becomes acommodity in the market, you don't really need the Wi-Fi Certified stamp ofapproval to ensure basic interoperability.

Extending beyond the basics has never been an easy task for the IEEE,especially when issues relate to application-layer functionality. The Wi-FiAlliance continues to assert its relevance by striving to meet the needs of itsmembership, including the many companies that see voice as a compellingWLAN application. By making WMM Power Save an optional element of thecertification, the alliance isn't forcing companies to adopt this technology. Butby offering such a certification, the alliance is advancing important capabilitiesthat will provide enterprise IT professionals with more choices. That's good forthe industry.