Whoever makes the wireless replacement for USB is onto a big thing: USB 2.0 is the most successful interface in history, included in 500 million PCs, and expected to be in five billion devices by 2007/2008.

Ultra-wideband (UWB) is a radio technology that could replace all those USB cables. It offers up to 1 Gigabit/s (with current implementations normally at 480 Mbit/s) over distances of a few feet.

It's no surprise that the first UWB implementations, from Freescale, are wireless replacements for USB - delivered by Belkin and Gefen. PBut they aren't alone. The USB Implementors' Forum has created its own specification, "Certified Wireless USB" based on the Intel-backed rival WiMedia version of UWB.

Despite Freescale's headstart, the Forum is confident that its own Wireless USB will win. Jeff Ravencraft, the Intel strategist who is president of the USB Implementors' Forum, explained why.

Freescale's start in the market should count for more now, since the IEEE has given up hope of getting the factions to agree on a UWB standard. If the market decides, it should favour the first products out there, right?

There are technical differences
"Other solutions use the USB 2.0 wire protocol wrapped up and put on top of a wireless medium, but it's not optimised," said Ravencraft. "Certified Wireless USB was created by the same people as USB 2.0: they designed the specification from the ground up, so it is optimised to run on a wireless medium."

Wireless protocols have to take more account of power management, and the security issues of associating with devices that perhaps can't be seen directly, or might be spoofed, says Ravencraft.

There's also a more basic difference. The Certified Wireless USB standard allows 127 devices to attach to one wireless hub, while more basic replacements for USB will simply put a dongle each end of a one-to-one connection. "With the current alternative you need another host dongles for every peripheral," said Ravencraft. "With our solution, a host will talk to multiple devices, on the same port, with the same dongle."

Freescale makes a virtue of the fact that it supports plain vanilla USB 2.0, saying that the Certified approach will need hardware upgrades and new protocols. Ravencraft concedes that Certified Wireless USB makes changes to the protocol, to get the benefit of wireless, but the hardware change is minimal. "For a legacy PC, you will just need a host adapter," he says. "The alternative needs new hardware, for the radio."

A one-stop shop for short-range radio?
Running Wireless USB over WiMedia's MB-OFDM gives more benefits, says Ravencraft: "It will be a one-stop shop."

This will have the benefit of allowing multiple vendors' radios, while the alternative looks like being limited to radio technology from Freescale: "That will drive competitive pricing," promises Ravencraft. "You will also have known interoperability."

WiMedia's MB-OFDM will become a universal carrier too, he says. Hosts that can support Certified Wireless USB can also support other stacks, such as Bluetooth Ethernet-on-UWB or encapsulated IP. All these protocols will share the air using a time-division scheme.

If the WiMedia protocol gets implemented at all widely, it will become a benefit for any other protocol group, such as Bluetooth, to make sure its products use the same radio technology, to get a share of the communication from these host dongles.

WiMedia as an underlying medium
It's a vision in which WiMedia will become the universal short-range radio. "WiMedia is more than just a PHY and MAC layer," says Ravencraft. "It allows multiple applications on the same radio. We can't keep putting multiple radios in devices. We have to try and minimise the number of radios."

It will also be the most adaptable radio possible, he promised, in order to meet regulatory requirements in any given country. "For example, we know Japan has a proposal on the table, that devices will have to be able to 'detect and avoid' other radios. Wimedia is well adapted to do that, because it has multiple bands, that can be adjusted, turned down or turned off.

But it's still basic
Despite this level of sophistication, the actual Wireless USB protocol is kept as simple as possible, retaining USB's distintion of hosts and peripherals. "When we designed Wireless USB, we didn't try to enhance that," says Ravencraft. There may be some dual role devices, such as printers, that can act as a peripheral to a PC, or a host to a camera.

Will the tortoise win?
Despite all this, there's no denying that Freescale beat Certified Wireless USB to the punch. Although the specification has been out since last May, there are as yet no Certified Wireless USB products that are actually certified and available, even at the silicon level.

"There have been a number of announcements from siliocon providers, and there is production silicon out there now," says Ravencraft. "Early products will be on shelves, in Q3, the back half of this year." Certificates will be issued to silicon vendors in the second quarter of this year, he added.

The price on the first hubs will start out high and drop, but Ravencraft believes users will be find the initial prices surprisingly low. "They could be $35 to $45," he says.

The end of the IEEE's UWB standards work means the products must struggle in the market, but Ravencraft points out that the original USB standards were developed outside the IEEE. "Standards bodies are great organisation, but there are a number of standards made outside."

In the gap before Certified Wireless USB arrives, analysts are predicting good sales for the Freescale-based products, but Ravencraft is complacent: "As the tortoise said to the hare, 'see you at the finish line'".