US officials will this week decide the fate of a wireless replacement for USB, planned for PCs by the end of next year.

The US regulator, the FCC, will decide a dispute on the precise interpretation of its rules on Thursday, which could settle the useful range of a form of ultra wide band (UWB), slated to do away with USB and Firewire cables. The following week, the IEEE will take a vote that could settle which kind of UWB will be the standard.

The FCC is judging the legality of multi-band OFDM, the flavour of UWB favoured by Intel - which has said it could be available in a USB dongle this Christmas. To bolster the technology, the two promotional groups behind this UWB flavour have merged, to form a group that will promote it in standards bodies and, will eventually certify products. The WiMedia Alliance will absorb the MBOA SIG.

Despite support from Intel, multi-band OFDM has had a rough ride. It has faced stiff opposition in the IEEE's 802.15.3a standards group for personal area networks, and a challenge to its legality under the rules of the FCC. Both have come from Motorola's Freescale subsidiary, and the UWB Forum which promotes it. Freescale is closer to real products than WiMedia , but is more focused on consumer electronics.

With agreement on an IEEE standard for UWB as far away as ever, start-ups are now concentrating on worldwide wireless regulators, to ensure the best market for the technology. "Standards apparently will take care of themselves in the market," said Jim Lansford, chief technology officer of WiMedia member Alereon.

The regulatory issues could be just as fraught though. The FCC ruling could influence European regulation. Ofcom is leading the way, asking for comments by the end of March to a proposal to allow UWB under terms very like the FCC's. International regulation will be discussed by the ITU (the International Telecommunications Union) in San Diego in May. "I would hope we will have regulations worldwide before products are delivered," said Steven Moore, director of intellectual property at Pulse-Link, a UWB start-up which stands outside the WiMedia/Freescale debate.

UWB is a challenge to regulators like the FCC and the UK's Ofcom, which are accustomed to licensing most frequencies exclusively, because it spreads radio signals across a broad range of spectrum at low powers that are not expected to interfere with other radio equipment (see our explanation). The FCC has approved it, so long as it emits less radiation than devices such as PCs or CD players are already allowed to leak.

Multi-band OFDM is charged with contravening these FCC rules, an argument that focuses on how the power level of products is measured. The Alliance hopes to get a waiver which will allow it to bring products to market until the matter is finally settled. If the ruling goes against it, WiMedia might have to reduce the range to keep within FCC power limits - Alliance members are confident this will not happen.

International regulations may limit UWB uneccesarily, warned Moore: "Some people are asking the ITU for power limits at some frequencies that are less than the power emitted by the human body. Some suggestions are less than thermal noise, and you can't do that without using a cryo-pump to cool down the surface of the Earth."

WiMedia members are hoping that a favourable result from the FCC will swing things their way when standards will come to the fore again. The deadlocked IEEE 802.15.3a task group will vote at the IEEE's plenary meeting in Atlanta on 13 to 18 March, but neither of the two contenders, which have slugged it out for the last 18 months, is expected to get the required 75 percent majority.

A third contender, Pulse-Link's CWave alliance - see UWB standards war splits to three contenders - promises faster speeds still, in a more LAN-like style. However CWave is further from products than WiMedia and Freescale, and is not formally proposing a standard at the IEEE, but has demonstrated its technology widely.