Last week, the IEEE 802.11n group reached agreement on the basis for a fast Wi-Fi standard using MIMO. But the initial excitement has given way to disagreement about how fast products will actually be delivered.

"I see outrageous claims in terms of where the products are - claims that can't be supported," says Greg Raleigh, chief executive of Airgo. "These claims are designed to trip us up and confuse the consumer, to convince them not to buy the best product on the market."

The proposed 802.11n standard will use MIMO (multiple input, multiple output) and other techniques to make Wi-Fi networks that reach a stated speed of 200 Mbit/s or more (but an actual throughput of somewhat less). After a prolonged standoff in the group, four silicon vendors worked outside the group in the EWC consortium, to create a draft, which has been accepted by the group as the basis (draft 1.0) for an eventual standard.

But since then, the story has got more complex. Atheros and other EWC members have claimed that the standard is now complete with only small details to be finished. Airgo - the leading vendor of MIMO chips for current systems - seems to violently disagree.

Atheros, Marvell and Broadcom have all claimed to be first to have silicon in samples, but others dispute that. "Sources say that Marvell’s 2x3 solution barely transmits two meters before failing," says network expert Paul Callahan in his blog.

Netgear has promised to deliver 802.11n-draft product by June. "We have announced our intent and enthusiasim on the 802.11n front," said David Henry product line manager for advanced consumer wireless at Netgear. "When companies like ourselves see a draft that is strong enough in terms of feature set, and meets a customer requirement, we will start to deliver as soon as possible. Range, throughpuit and security are the key tenets of 80211n."

"We also plan to have [draft-802.11n] product by the end of Q206," said Balvinder Phull, D-Link marketing communications manager.

Airgo's concern is that its latest generation of MIMO chips are only just entering the market - Netgear is using them in a "240 Mbit/s" wireless box, and Linksys launched its Airgo-based SRX400 product range at CeBIT last week.

A perception - even a false perception - that the market will quickly shift to an 802.11n standard would harm the sales of its current range.

What will happen to the standard?
The big question is what will happen to the standard? Atheros and others are giving the impression that it just needs tidying up, and we can all have products by summer.

Airgo, on the other hand, says there are other issues that should be addressed to get better performance. "Wi-Fi is 100 percent about performance," says Raleigh. "There will be a significant difference in the chip price between 802.11n, and 802.11b/g - you will only pay that because you want to do new things with Wi-Fi, because you need to shoot Ethernet speeds through three to five walls."

There are also problems with the draft, particularly in the way it shares the airwaves with other Wi-Fi networks. As well as using MIMO to multiply the paths between client and access point, the 802.11n draft - like some current MIMO products - uses a double-width (40MHz) radio channel, which leaves less spectrum for other Wi-Fi networks within range.

Atheros used two channels for a "turbo mode" in its products (used for instance in the D-Link router reviewed here but mostly disabled), and Netgear uses a wider channel in the silicon used by Netgear and Linksys for "240 Mbit/s" Wi-Fi kit.

Sorting out how 802.11n networks will "play nicely" is just one of the issues the group will have to address, says Raleigh. Cisco and Motorola are chairing an ad hoc group to work out changes, reports Glenn Fleishman in Wi-Fi Net News.

If lots of changes happen, the draft will need to go to version 2.0 or 3.0, and those product deadlines - if they ever were realistic - will slip.

Are we back to the MIMO wars?
Of course, there's another way to look at this: could Airgo's plans to ask for changes be a fillibuster, designed to delay the standard and preserve Airgo's proprietary market? Are we, in short, back to the MIMO wars that kept the 802.11n group in stand-off mode for two years?

Raleigh denies this: "We're thrilled with the progress," he said. "802.11n is Airgo's technology. Our intellectual property is wrapped up throughout. There appears to be a market north of 2.5 billion chipsets, and 80 percent of the Wi-Fi market will be 802.11n by the end of 2007. We're proud to have been able to convince the industry to standardise."

When the final standard is set, he says Airgo will still win out, thanks to its lead in making products: "Performance is not set by the standard, it only specifies the language you speak, not your fluency. One supplier's equipment can be a Shakespeare, while another's is barely literate."

The race to silicon
Set against that, there's a race to make silicon and win designs. The other vendors claim to have EWC-compliant silicon - and it is now in their interest to minimise the changes to the standard, so the chips meet a relevant spec when they reach the market.

"Commitment to silicon, even in small quantities, is expensive," points out Fleishman, "and changes in certain aspects of the radio’s functionality would almost certainly require “retaping” circuit designs — making changes to produce new chips that have to go through significant testing."

Meanwhile, Airgo has the opposite problem: "Airgo is rushing to spin up silicon that will match the standard," says Callahan. "To date, the company has yet to break out of the low margin consumer Wi-Fi space. Without more wins, Airgo’s only exit is acquisition."

What about the actual speed?
As a footnote, it's worth mentioning that the actual speed of 802.11n is as yet undetermined, and Wi-Fi has a history of overstated claims in the way speeds are quoted. 802.11g products promise "54 Mbit/s" on the box, but that is a maximum "symbol rate". More than half of that is eaten up by network overheads, and users get around 20 Mbit/s of actual data throughput.

While promises of 300 Mbit/s may turn out to be in the same category, the industry is hoping 802.11n will bring Wi-Fi speed claims more into the realm of reality. Different figures are quoted, but it may be that 802.11n gives data rates as much as 75 percent of the quoted symbol rate of 200 Mbit/s.