More Room on 5Ghz
McFarland notes that the so-called politeness requirements are not nearly as strict for 802.11n networks that use the 5GHz band (which will be backwards compatible with today's 802.11a products). Before sending a 40mhz packet on a 5GHz network, the equipment just has to check that neither 20mhz channel is in use by a nearby network. But channel overcrowding is not nearly as big an issue for 5GHz networks as it is for 2.4GHZ ones since the 5GHz band has some 20 non-overlapping 20mhz channels. And legacy 802.11a networks, which exist primarily in corporate environments, are far less common than 802.11b/g networks to begin with.
However precisely because of channel overcrowding on 2.4GHz networks, 5GHz 802.11n network are expected to become increasingly popular--especially for high-bandwidth applications such as media streaming, which can really benefit from being able to use fat 40mhz pipes. But because so many 802.11b and g notebooks and other devices are still in use, several vendors are now preparing to release dual-mode routers that can support both types of network traffic.
If shopping for such a router, McFarland notes, be sure to look for one that allows concurrent access, meaning it can simultaneously support both 2.4GHz and 5GHz traffic. Some "configurable" dual-mode routers will only support one frequency or another, so devices using different bands won't be able to communicate.
What's Next for 802.11n
If, as expected, draft 2 of 802.11n is announced in the next few days, the road to a final standard is still long and complicated. The first step will be the immediate submission of draft 2 to all 600 or so members of the 802.11 working group as a candidate for the final standard. Group members will have 30 days to vote, and 75 percent approval is required.
But even if Draft 2 gains that approval, the standard process is far from over. McFarland says members of the working group will still submit comments that must be considered and addressed (to the extent possible) in the standard. Additional rounds of balloting are required with ever-increasing pools of voters. McFarland says that at this point, the target date for final publication of the 802.11n standard is October 2008.
But draft 2 software updates should deal with the major issues that plagued draft one products, and Wi-Fi Alliance certification should give buyers a measure of confidence that they are buying standardized technology, and that products from different vendors will work together, McFarland said.
Getting Ready for Testing
Karen Hanley, senior director of communications for the Wi-Fi Alliance, says informal "plugfests" where vendors test their 802.11n products' compatibility with other vendors' products, have been underway for some time. The Alliance uses these events to gather information that will help them choose their testbed products--the ones that products submitted for certification will be tested against.
One of the Alliance's biggest challenges will be to help consumers identify products certified for interoperability with draft 2 products, as opposed to products that will eventually be certified for the final draft, when it appears. The Alliance will update its testing program then, Hanley said, and such differentiation could matter.
"Part of the logoing challenge is making sure consumers do have the information that they need, but not asking them to understand too much of the inner workings of the IEEE," Hanley said.
But she expressed optimism about the potential of 802.11n to further expand Wi-Fi's availability and use. "New and different devices are coming into the fold," she said, noting that the 802.11n standard also addresses the needs of a range of non-traditional networked devices such as handhelds and consumer electronics.
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