Radioactive: Bluetooth - survival of the fastest

May the best wireless technology win...

Bluetooth continues to confound analysts who have long predicted its imminent demise. Analysts IDC estimate 13 per cent of mobile handsets sold in 2004 incorporated Bluetooth and that figure looks set to increase in 2005.

Those who believe it will soon be sidelined by Wi-Fi will be surprised to hear that the Bluetooth Special Interest Group, the industry association that ratifies the Bluetooth standard, has announced plans to work with the developers of the precocious ultrawideband (UWB) technology and incorporate this radio access technique in its future technology road map. Essentially this means that all future high-speed Bluetooth devices will use UWB radio frequency technology.

UWB addresses the same cable replacement market as Bluetooth technology but with theoretical speeds from 100Mbps to over 2Gbps, allowing connection of multimedia devices such as televisions and PCs. The Bluetooth SIG has been debating a higher-speed technology for some years and this move allows it to both eliminate its main competitor for short range wireless and take advantage of the existing body of UWB technology.

The convergence of the standards is also of benefit to engineers working on UWB. The idea is that UWB devices will be able to use all of the existing components of Bluetooth besides the radio technology, such as its tried-and-tested solution for service and device discovery, and the application layer, for example.

Many of the Bluetooth SIG members are already involved in UWB development and so they need not reinvent the wheel. In fact, Mike McCamon, the recently appointed executive director of the UWB Forum, formerly held the same role with the Bluetooth SIG.

UWB technology has been around for a surprisingly long time. The first work was the development of what was then called impulse radio, baseband or carrier-free communications back in the 1960s. The term 'ultra-wide band' was first coined by the US Department of Defence in 1989 which was using it for ground-penetrating radar. The US Federal Communications Commission (FCC) currently defines UWB as a radio technology with a minimum spectrum of 500MHz. In 2002 the FCC allocated unlicensed radio spectrum from 3.1GHz to 10.6GHz for its use.

This broad definition of UWB covers a number of different approaches and despite standardisation attempts by the IEEE, the future of the technology is far from clear. In fact one of the reasons why UWB has been unable to present a credible alternative to Bluetooth is that the standards development has deteriorated into political infighting between two opposing factions, backed by US giants Intel and Motorola respectively.

The opposing technology approaches are orthogonal frequency division multiplexing (OFDM) and direct sequence (DS)-UWB. The former method, backed by Intel, is more complex: it chops up the signal and sends it over multiple frequency bands. This increases the signal's range by reducing interference. The other approach sends out the signal in a single stream which reduces the complexity of the transmitter and the power it requires. This latter method is more attractive to handheld devices such as those from Motorola.

The Bluetooth SIG is hedging its bets with both camps. Indeed its press release announcing the initiative quoted both Motorola and Intel representatives, which of course are both active participants in the Bluetooth SIG. When Radioactive spoke to Anders Edlund from the Bluetooth SIG, he acknowledged that while there are still many outstanding standardisation issues, there is no need to rush products to market.

Details of how the Bluetooth SIG will work with the fragmented UWB camps are still sketchy but Edlund said they will be available shortly - by the end of this year at the very latest. Although let's hope he is not holding his breath if the track record of UWB's adherence to deadlines is anything to go by.

The general direction they will be taking is to create a convergence layer that will allow device manufacturers to abstract the radio frequency (RF) part from the rest of the device. This is vital because the RF portion of Bluetooth is quite different from UWB.

This abstraction will allow manufacturers to use both the slower Bluetooth and faster UWB radio technologies in one device, and should insulate developers from any changes in UWB standardisation. The first devices will use two separate RF chips, with integrated basebands planned for the future.

The faster UWB-based version of Bluetooth will not supersede the existing Bluetooth RF technology completely. Existing lower-speed Bluetooth applications such as audio headsets, for example, should survive in the original format and the technology is also designed to be fully backwards compatible.

While the technologies are well matched, there is no doubt the Bluetooth SIG is going out on a limb by trusting that the political rows which have continued to plague the standardisation of UWB are going to be peacefully resolved. Furthermore, the UWB specification has also only been approved in the US and has still not been accepted in Europe and Asia. But these sorts of problems have been overcome before, and the worldwide success of Wi-Fi is testament to this.

Anthony Plewes is a freelance journalist and director at Futurity Media.