With all the new wireless standards coming out of the woodwork lately, you may be forgiven for thinking that our airwaves are becoming pretty crowded. This tends to be the view espoused by regulators and government agencies – “Wireless bandwidth is scarce, and therefore costs”. However this is not the view of proponents of a “new” wireless technology – Ultra-Wideband (or UWB). Their view is that the percentage of the whole radio spectrum (i.e. including into the Gigahertz range) already occupied is small, but which bit is being used by something else varies considerably over time and from country to country. Not only that, UWB “will change everything”, replacing both Wireless LAN (WiFi) and Bluetooth in the process, and giving 3G a run for its considerable amount of license money.

Not new – just reborn

There is no internationally recognised definition for how wide an emission has to be to be called ultra-wideband. As a result, there are various definitions of what UWB actually is. Most of them, however, are not very revealing to the layman. For example, one plausible definition is that it is loosely defined as “any wireless transmission scheme that occupies a bandwidth of more than 25% of a centre frequency, or more than 1.5GHz”. So what does that mean and, more importantly, why should we care anyway?

UWB has been used since the 1980s in specialist applications, particularly military ones. It is very good for precise measurement of distances for radar applications and for obtaining images of objects buried underground or behind surfaces like walls. It is based on very short, sharp pulses spread over a very broad range of frequencies at very low power, enabling high data rates to be transmitted over short distances. For example, over about 5 metres a data rate of up to 500 Mbit/s may be achievable. As a result, there is a lot of interest in it for short-range high-speed data transmissions suitable for broadband access to the Internet. A speeded up WiFi in fact.

It works on the principle that spreading these pulses with very low power generates an “ethereal buzzing” which is indistinguishable from background radio noise, making it difficult to detect and therefore potentially more secure than spread spectrum technologies like Bluetooth and WiFi.

Further, as a result of recent developments in high-speed switching technology, UWB is becoming more attractive for low cost integrated circuits. Intel, for example, sees lots of opportunities for low cost consumer communications applications.

Difficult Europeans

Needless to say, there is considerable opposition in some circles. Because it encroaches on a very wide range of frequencies, there is real concern regarding possible interference with licensed uses in some of the frequency bands utilised. For example it is considered that, with a large population of UWB devices operating, the general level of background noise may increase to the point of causing significant general interference. Testing this under laboratory conditions is difficult but recent measurements in Europe have suggested that UWB may for example interfere with third generation mobile phone services (3G). With the enormous license fees paid in some countries for 3G, it is not surprising that the merest suggestion of possible interference would be taken seriously. Needless to say, this type of concern has led to calls to prevent it being implemented in Europe. Nevertheless, there are also equally strong advocates for the technology in Europe who maintain that any interference is entirely marginal and substantially less than current GSM mobiles inflict on other services, for example. Given time, a compromise therefore looks likely.

In the US, though, the prevailing sentiment is much more positive. The IEEE has been involved for some time in measuring potential interference with other services, and has concluded so far that the threat is minimal. As a result, the FCC released an Order in June 2002 permitting the marketing and operation of certain types of new products incorporating low power UWB technology.

Applications, applications

This Order established different technical standards and operating restrictions for three types of UWB devices based on their potential to cause interference. These are:

These categories therefore indicate where UWB may initially be used. The technology has been used for some time in Ground Penetrating Radar (GPR) applications. It now offers potential for new types of imaging systems that would, for example, enable police, fire and rescue personnel to locate people hidden behind a wall or under debris in crises or rescue situations. UWB imaging devices also could be used to improve the safety of the construction and home repair industries by locating steel reinforcement bars in concrete, or wall studs, electrical wiring or pipes hidden inside walls.

Further, as the vehicle radar category indicates, it could be used to improve automotive safety with collision avoidance systems and air bag proximity measurement for safe deployment. It could tell you just how close you are to the car behind when reversing into a parking space, for example. Needless to say, the car manufacturers are already on to this.

The other key area is the third category – communications systems.

Replacing Bluetooth and WiFi?

UWB offers some particular benefits in this category. For example, UWB transceivers use low power short burst radio waves, so they do not take as much planning to build. This makes them easy and cheap to build compared to typical spread spectrum transceivers – as used in Bluetooth and WiFi for example.

Also, UWB systems consume very little power, around one ten-thousandth of that of cell phones. This makes UWB practical for use in smaller devices, such as cell phones and PDAs.

Thirdly, it operates anyway at very low power, considerably reducing its potential interference impact on other systems.

In its current restricted state, UWB probably represents more of a threat to Bluetooth in the US than to WiFi. This is due to the current power limitations imposed by the FCC. As a Bluetooth competitor, it offers speeds of up to 500 Mbit/s over short distances compared with Bluetooth’s 1 Mbit/s. Projected hardware costs are also similar.

As far as WiFi is concerned, the situation is likely to change as a result of further reviews as the IEEE completes more work looking at whether UWB interferes with other services or not. The prospect is that, at some stage, UWB will represent a suitable replacement for WiFi as well, with much higher short-range speeds highly compatible with Home Network requirements for fast video entertainment applications.

So what happens then to all those WiFi hotspots currently being deployed everywhere? Clearly, this is potentially disruptive technology.

 © e-principles 2003

Robin Duke-Woolley