SAN JOSE, Calif.—Interoperability among the various IEEE 802.11 technologies will become “a real challenge” as the industry moves into a phased program for deploying multimedia services over Wi-Fi next year, industry executives said.
In a panel discussion presented at the Wi-Fi Planet show here, industry executives responsible for the evolution of the IEEE 802.11 “alphabet soup” presented an updated road map of future 802.11 technologies, including the rollout of 802.11e, which will undergo a two-phase deployment beginning next year.
The evolution of 802.11e will have a direct effect on voice-over-IP networks, which will need to be upgraded possibly several times, executives said.
With initiatives like Intel Corp.s Centrino program and the development of Wi-Fi-enabled cellular handsets, the 802.11 standards body has moved out of the province of a few engineers and has become a mainstream topic of discussion, noted Greg Ennis, technical director of the WiFi Alliance, the industry body that conducts interoperability tests among the various Wi-Fi vendors. At the same time, those vendors now require a steady evolution of the technology.
By the end of 2003, the IEEE hopes to finalize the specification for 802.11h, a Europe-specific addition to the MAC layer for 5GHz WANs. In 2004, the IEEE is slated to finalize 802.11j, a similar specification for Japan, plus the 802.11i security standard as well as the phased implementation of 802.11e. In 2005, the group will meet to hammer out the specs for 802.11n, a next-generation Wi-Fi spec with speeds expected to top 100M bps.
The WiFi Alliance has begun to work more closely with the IEEE engineering standards body in monitoring technology development, Ennis said. Although the alliance does not test new standards, the body stepped in to promote the development of the Wireless Protected Access (WPA) security specification as a replacement for Wired Equivalent Privacy (WEP), an early and largely inadequate security protocol.
Although the IEEE and the WiFi Alliance have successfully rolled out the standards 802.11a, .11b and .11g, a number of future improvements are planned for next year. However, testing a new wireless standard with new equipment adds a tremendous number of variables to any engineering test bed, and Ennis warned the complexity could affect future alliance certification programs.
Ennis said maintaining compatibility “will be a real challenge.” “We have interoperability challenges going forward,” he said. “Here we have an established base of interoperability among Wi-Fi manufacturers, but it will be more critical as we move into the next phase.”
The trickiest part of the next phase may well be 802.11e, designed to allow quality-of-service protocols to run over Wi-Fi. Although video is often considered the stress test of a network, users wont often notice an error or two in a video stream, said Ian Sherlock, who manages wireless LAN product development for Texas Instruments. Users speaking in VOIP phones, on the other hand, quickly pick up on any network latency, which translates into unexpected pauses in the conversation.
The 802.11e upgrade will probably follow the example of the Wi-Fi security protocols, which have evolved through WEP through WPA and onto 802.11i.
Today, VOIP networks run on top of 802.11a, .11b or .11g, or in conjunction with some proprietary implementation of a Wi-Fi technology, Sherlock said.
In the first half of 2004, a substandard known as Wireless Multimedia Extensions (WME) will be rolled out, which uses a function called Enhanced Distributed Channel Access, Sherlock said, a simpler contention-based scheme. In simulated tests, TI found that a WME-based network could support about 50 handsets before a noticeable loss of data.
Currently, an 802.11e subgroup is defining Wireless Scheduled Multimedia, the second phase of 802.11e. If all goes as planned, WSM should roll out in the latter half of 2004, Sherlock said, using a more complex function called Hybrid Coordination Function Controlled Channel Access, or HCCA. HCCA allows the access point to initiate exchanges by “polling” the handsets every so often, and has proven less susceptible to data loss under load, Sherlock said. This protocol will probably support twice the number of handsets WME will, he said.
In all, VOIP networks will have to undergo at least two upgrades to take full advantage of 802.11e, Sherlock said. “With proper management, this will only require a software upgrade,” he said, noting that equipment makers may opt to skip the first WME deployment and jump straight to WSM, which should begin to be designed into certified products by the third quarter of 2004.
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