A dispute over spectrum regulations could hamper the arrival of fast WiFi in Europe. New regulations have been created which affect 100 Mbit/s Draft N - but the French are insisting those regulations are introduced in a way that will cause problems with existing WiFi equipment.

Anyone with a long memory for WiFi will feel that, if a spanner is thrown in the WiFi works, the chances are the hand holding it is French. In 2002, French regulators delayed approval of the 802.11a specification in Europe, and the current issue is in some ways a continuation of that problem.

802.11a, the fast WiFi that never really flew

In 2002, the main WiFi standard was 802.11b, operating in the licence-exempt-2.4GHz band, at a symbol rate of 11 Mbit/s. To offer faster speeds, vendors moved to the 5GHz band where a greater number of channels allowed them to create 802.11a, operating at 54 Mbit/s.

In Europe, however, that band included frequencies used by military radar; the European regulator, ETSI, would not allow it until dynamic frequency selection (DFS) and transmit power control (TPC) had been included to prevent interference. DFS allowed a WiFi system to back off from a channel where radar was detected - an early approach towards so-called cognitive radio. ETSI defined a common European test for radar, Euro Norm (EN) 301 893.

The ETSI standards were endorsed by the IEEE, and "harmonized" WiFi was called 802.11h - but since vendors implemented the ETSI tweaks in all their 5GHz kit, the term was rarely used as all 802.11a kit met the 802.11h specifications (read a white paper on the subject, and the EC Decision 2005/513/EC).

Unfortunately, 802.11a was also hardly used. The 802.11g specification had taken WiFi's 2.4GHz branch to a 54 Mbit/s symbol rate, so few people actively took up 802.11a, despite the appearance of dual-band a/b/g devices.

Since 2004, despite occasional reports that it was improving, and vendor backing, 802.11a has been doggedly uninteresting.

Draft N brings life to 5GHz

The emerging 802.11n standard looks like bringing 5GHz back to life, as it operates in both bands, as a successor to a/b/g products using MIMO (multiple input, multiple output) technology to create faster speeds. Early products have been single-band, operating only in 2.4GHz, but dual-band products are appearing, such as the Apple Airport Extreme.

Dual-band products will be better - assuming that both client and access point are dual-band - because the 2.4GHz band is becoming increasingly crowded, with WiFi, Bluetooth and leakage from microwave ovens. If 2.4GHz isn't working well, dual-band devices can move to 5Ghz for better throughput.

The 802.11h tweaks may not have achieved much in getting us to use 802.11a, but you would think that at least they have paved the way for 802.11n to move smoothly into 5GHz. Unfortunately, this isn't the case.

But the 5GHz harmony gets a tweak

Just as WiFi kit is set to move into the 5GHz band, ETSI has brought out a new version of its DFS tweak - known as EN 301 893 version 1.3.1 - published in October 2006.

The new version tightens up the requirements for detecting radar in the 5GHz bands, and vendors were originally given until March 2008 to comply with it.

Over Europe as a whole, regulations in the 5 GHz are supposed to become identical, according to the EC's decision 2005/513/EC. France's regulatory authority, however, decided to demand compliance with the newer version sooner than the rest of Europe, in a decision dated December 13 2005, from ARCEP, the French spectrum regulator.

As a result, equipment complying with 1.2.3 of the DFS specification - essentially all current 5GHz WiFi equipment - cannot legally be sold in France.

"The reference to EN 301 893 version 1.3.1 in the above mentioned radio interface was
a surprise," said Tony Graziano, director of technical and regulatory affairs at European industry group EICTA, in a letter to the EC complaining about the impact of this decision.

Industry groups attempted to broker a compromise, which would bring in the newer specification sooner across Europe, but that was still not soon enough for France, apparently. Demanding compliance earlier makes no sense when wide deployment of 5GHz equipment isn't expected till next year anyway.

"EICTA is of the view that the position from France is in conflict with Community law," says Graziano. The earlier version of EN 301 893 was published in the Official Journal of the European Commission, so there should be no problem using it, he says, and France should remove its specific insistence on the later version.

The trouble with chips

The problem with the newer version is that current silicon can't support it. Firmware bringing today's chips into line results in false positives, according to Michael Coci, director of technical marketing at Trapeze.

The only practical fix is to disable many of the 11a channels, which ends up reducing the 11a band to around 3 channels, so the equipment ends up with the same performance issues as the 2.4GHz band.

Chips that can handle the new DFS specification, without this problem, will be available next year. It would make more sense to update the requirement at the same time as the silicon is available, so the market can develop this year - especially as the amount of equipment actually sold this year will be too small for the difference in DFS specifications to have any impact on military radar.

It's too early to say whether the issue will cause any trouble outside France, but vendors are lobbying hard to get France into line with the rest of Europe, and avoid troubles with the arrival of N-grade WiFi in Europe.