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Ultra-wideband wireless technology

Ben Kelland - bk100@ecs.soton.ac.uk - 10/12/2002 Abstract Ultra-wideband (UWB) is a wireless technology that has the potential for very high data transfer rates, and properties that allow it to travel through walls and smoke. It has a whole host of user applications, from networking to radar, and can even be used to “see” through walls. This paper looks at the technological specifications behind ultra-wideband, current and possible applications, and the licensing and regulation of UWB systems. Introduction Ultra-wideband (UWB) is a revolutionary wireless technology for transmitting digital data over a wide spectrum of frequency bands with very low power. Not only can UWB transmit data at very high rates but it also has the ability to carry signals through doors and other obstacles that tend to reflect signals at more limited bandwidths and a higher power. [UWB working group]. As well as traditional networking applications there are a host of other uses for the technology from radar to medical imaging. One big area is in systems developed for rescue workers, such as fire-fighters, where UWB’s properties of being able to travel through walls, debris and smoke combined with high speed transmissions will make it the ideal technology. This paper will attempt to outline some of the possible future uses of ultra-wideband, and give examples of how it is already being used. The technology behind ultra-wideband is somewhat different to existing wireless technologies. A summary of the concepts of the technology will be given, together with a comparison between UWB and current short range wireless networking systems. Finally this paper will discuss the current regulatory issues connected to ultra-wideband, and how this has affected and will affect UWB development. What is the technology behind UWB? Whilst traditional wireless systems take up a narrow band of frequencies assigned by government regulatory authorities, ultra-wideband occupies a broad swathe of frequencies, typically 1.5 to 4 GHz wide, that cover many already assigned frequency bands in the 1 to 6 GHz range. [D Leeper, Computer]. UWB is supposed to produce no undue interference to existing systems, and emits a power so low that it meets US Federal Communication Commission (FCC) constraints under FCC Part 15, set for incidental radiation from devices like laptops, hairdryers and electric drills, however UWB systems need a waiver from this because they function as intentional radiators. [D Leeper, Computer] A typical 200-microwatt UWB transmitter, for example, radiates only one three-thousandth of the average energy emitted by a conventional 600-milliwatt cell phone. [D Leeper, Scientific

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American] There has been a recent revision to the Part 15 rules by the FCC allowing the limited use of UWB, which is covered in a later section of this paper. Technically, a UWB system is defined as any radio system that has a bandwidth greater than 25 percent of its centre frequency, or greater than 1.5 GHz. Conventional “narrowband” and “wideband” systems use Radio Frequency (RF) carriers to move the signal in the frequency domain from baseband to the actual carrier frequency where the system is allowed to operate. Conversely, UWB implementations can directly modulate an “impulse” that has a very sharp rise and fall time, thus resulting in a waveform that occupies several GHz of Bandwidth. [J Foerster et al.] If wireless were an ideal medium then we could use it to send � a lot of data, � very far, � very fast, � for many users, � all at once [J Foerster et al.] However if one or more of these are to do well then others must be sacrificed. Due to ultra-wideband having a very low radiated power, UWB systems are not suitable for long-range communication use, but appear ideal for short-range, very fast wireless use, particularly for PANs (Personal Area Networks), which have a range of around 10 metres. [D Leeper, Computer]. A table showing various wireless standards specifications is found in figure 1. It indicates UWB as being the most favourable in all the categories.

Technology Data Rate Range Cost Power Spectrum Summary

UWB 50-100Mb/s (theoretically up to 500Mb/s)

500 ft Low Low Ultra-wideband

Only high data rate WLAN in 300-500 ft. range

802.11a 54 Mb/s 90-100 ft

High High 5.0 GHz Power, cost issues

HyperLAN 25 Mb/s 100 ft High High 2.4 GHz European standard, same as 802.11b issues

802.11b 11 Mb/s 250-300 ft

Med Med 2.4 GHz Speed issues

Home RF 11 Mb/s 150 ft Med Med 2.4 GHz Lost Intel support; speed issues

Bluetooth 1 Mb/s 30 ft Low Low 2.4 GHz Speed issues

Figure 1. Table showing short-range wireless properties. [R Mathieson Nov 02] One of the limiting factors of wireless technologies relates to the “spatial capacity” of the system. Spatial capacity is the term used to describe how much data can be transmitted in a given area during a certain amount of time. With all wireless standards there is a limit on its spatial capacity, figure 2 displays a comparison between several wireless technologies.

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It can be seen that Ultra-wideband way out performs the best of the current technologies in terms of spatial capacity by almost 20 times. This can be attributed to the Hartley-Shannon Law (fig 3), which offers that because the upper bound of a channel’s capacity grows linearly with the total bandwidth, UWB systems, which occupy 1.5GHz or more, have a much greater amount of space for expansion than the narrower band systems. What are the main applications for UWB There are numerous possible uses for UWB, the FCC (US Federal Communication Commission) has set guidelines for UWB use in the following areas (see also appendix A): � Ground Penetrating Radar Systems, � Wall Imaging Systems, � Through-wall Imaging Systems, � Medical Systems, � Surveillance Systems, � Vehicular Radar Systems, � Communications and Measurement Systems

[FCC First Report And Order]

0100200300400500600700800900

1000S

paci

al C

apac

ity (k

bps/

m2)

IEEE802.11b

Bluetooth IEEE802.11a

Ultra-wideband

Figure 2. Comparison of Short-Range Wireless Spatial Capacities [D Leeper, Scientific American]

��

����+=

NS

BC 1log2

Where: C = Maximum channel capacity, in bits per second B = Channel bandwidth, in Hertz S = Signal power, in watts N = Noise power, in watts

Figure 3. The Hartley-Shannon Law

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These areas outlined show how varied the uses and users for the technology could be. Some of the more common uses that have been developed or are currently in development are featured below.

Networking for Personal Area Networks There are many different and varying applications for the use of ultra-wideband technology. Probably the most likely to be encountered by the average person in the future are its uses in networking and communications. UWB’s closest relation in this market is Bluetooth. Bluetooth is designed as a replacement for serial and USB cables in computing, with its inclusion on an ever-expanding array of electronic products likely. However, UWB has the potential to perform that function a lot better, with improved transfer speeds making wireless video transmission a possibility. UWB can also handle a lot more devices in the same area without bandwidth reducing (see fig 2), so as wireless electronic devices become more prevalent and demand for higher speeds increases, so bluetooth may be succeeded by the newer technology. "With ultra-wideband, you could see throughput rates of 100 to 500 megabytes per second over distances of up to 500 feet," says Rajeev Chand, a senior analyst with investment bank Rutberg & Company. [R Mathieson Nov 02]. It is debated in many online articles whether bluetooth will be made obsolete by UWB devices or whether they will be used for different applications and hence complement each other. This is something that will likely be decided by consumers, however as serial cables have slowly been made obsolete by usb cabled devices there is a possibility the same could happen to bluetooth, it is unlikely to happen soon because UWB devices are not going to be available until bluetooth has had a long time to get a foothold in the consumer market, but for those applications that bluetooth cannot fulfil such as video, UWB could find its niche.

Surveillance/law enforcement There is a potentially controversial use for UWB technology. UWB can be used to “see” through walls. It has the ability to detect moving people behind walls. This has obvious uses for police and other security services with police officers able to track criminals or assess a hostage situation [R Mathieson Oct 02],"You can actually see through the walls," says David Hoover, a senior analyst for research firm Precursor Group. "It's kind of like when you see heat sensors picking up the aura of a person in the other room." In July 2001, Time Domain were awarded a $3,000,000 contract from the U.S. Department of Defense Advanced Concept Technology Demonstrator Program to develop a through-wall surveillance radar for use by the military in urban environments. The new system called SoldierVision will build on their existing current commercial through-wall motion detection technology called RadarVision. RadarVision uses10 million UWB pulses per second, to detect motion behind walls. When the device is held up to a wall (within about 30 feet), a "map" of detected motion is displayed on its screen to give the operator a real-time depiction of direction and distance to the motion contact. [Time Domain website]

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Figure 4: (from left) Example use for RadarVision, an example of how the device may look, and a sample output from the display.

Fire fighting and other rescue services Fire fighting and other rescue services could benefit greatly. [R Mathieson Oct 02]. Traditional wireless communications have difficulty travelling through walls and smoke, however UWB has the potential to transfer 100Mb/s or more in a lot more difficult environment than existing technology. Mobile solutions provider Florian Wireless is one developer of communication devices for fire and rescue services, however they say that due to the stringent regulations of the FCC it severely limits ultra-wideband’s capabilities. "Our system enables us to track firefighters from 1000 feet away," says Valania, COO, Florian Wireless. "But with the restrictions, we can only track from 150 feet. We can do it, but as a firefighter, I'm shocked the FCC has made this kind of decision." But UWB has been the “holy grail” of wireless firefighting applications since 1998, when Time Domain was granted a waiver by the FCC to sell 2,500 of its x-ray-style "Radar Vision" devices to Houston-area law enforcement officers and rescue workers. Using Time Domain technologies, Florian's First Call communications and tracking system integrates with firefighters' PASS (personal alert safety systems) devices and Self-Contained Breathing Apparatuses. The device transmits each firefighter's location, heart rate, sinus rhythms, air bottle usage, and the air pressure and temperatures in the vicinity, to a base station set up at a command post outside. [R Mathieson Oct 02] Regulatory Issues On February 14 2002, the US Federal Communication Commission (FCC) adopted a First Report and Order that permits the marketing and operation of certain products using ultra-wideband (UWB) technology (See appendix A for details). “This First Report includes standards designed to ensure that existing and planned radio services, particularly safety services, are adequately protected. The FCC will act vigorously to enforce the rules and act quickly on any reports of interference.” [FCC Press Release] A review has been planned in 6-12 months, and represents “a cautious first step with UWB technology.” [FCC Press Release]. However, in the separate statement of Commissioner Michael J. Copps of the FCC [FCC Commissioner’s Statement] he says “We owe it to our citizens and our businesses to determine, just as quickly as we prudently can, whether we can loosen the ultra-conservative restrictions we put in place today.” This indicates a willingness that further loosening of the regulations could come later.

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Whilst it has been welcomed that the FCC has made a ruling allowing ultra-wideband use, many see it as too conservative. One UWB system for use by fire-fighters can no longer be employed outside as a result of signal strength being limited. Fire-fighters must now place UWB base stations within a burning building, with wired connections then piping the information out to the command post. "To show you how ludicrous this is, if a firefighter is five feet outside the front door of a burning building and activates [the device], he's technically broadcasting illegally," says Valania. "You have to actually set the base station up inside the front door. The FCC has made this an indoor-only technology." [R Mathieson Oct 02]. The FCC has provided regulatory approvement in the USA, however, has permission been obtained in the rest of the world? Not at this time, however there is significant interest in many countries and steps are being taken to explore a number of foreign markets and regulatory processes. [UWB working group]. It is likely other bodies around the world will follow a similar line to the FCC with a cautious acceptance of the technology in 2003. Conclusion: The biggest limiting factor to the introduction of ultra-wideband systems is most likely going to be in terms of regulation, with only the USA’s FCC having licensed the technology, and then only in a somewhat limited capacity. This is unlikely to continue and the EU and Japan are currently investigating UWB for their own licensing proposals and the FCC is planning a review of the February ruling. However another problem could come if further research shows UWB produces greater interference than originally thought, yet this is likely to slow the widespread use of UWB for only a while. Ultra-wideband is here to stay. There are so many different uses for the technology that it will be around in some form or another. Figure’s 1 and 2 both show how the technology has the potential to perform much better than current systems in terms of data carrying. It also has some very good physical properties allowing it to travel through walls, smoke and the like, making it the first technology that can be seriously employed in difficult conditions by fire-fighters. When mass produced UWB chipset costs are similar to that of existing wireless technologies, but need less power to operate allowing for use in smaller devices. Devices employing UWB could become as ubiquitous as lights in our homes or offices, with all electronic goods potentially being interconnected. Ultra-wideband has ultra-wide potential, whether it’s to produce faster short-range wireless networks, new radar and surveillance systems or helping save lives when employed by fire and rescue services. It’s a technology with too many possibilities for us to ignore.

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References [FCC First Report And Order] First Report And Order “Revision of Part 15 of the Commission’s Rules Regarding Ultra-Wideband Transmission Systems”, ET Docket 98-153, February 14 2002. [FCC Press Release] FCC Press Release, February 14 2002. [FCC Commissioner’s Statement] Separate statement of Commissioner Michael J. Copps, RE FCC First Report And Order - ET Docket 98-153, February 14 2002. [J Foerster et al.] Jeff Foerster, Evan Green, Srinivasa Somayazulu, David Leeper, “Ultra-Wideband Technology for Short-or Medium-Range Wireless Communications”, Intel Corp. [D Leeper, Computer] David G Leeper, “A Long-Term View of Short-Range Wireless”, Computer, June 2001. [D Leeper, Scientific American] David G Leeper, “Wireless Data Blaster”, Scientific American, May 2002. [R Mathieson Oct 02] Rick Mathieson, ”'band' of brothers”, mpulse magazine, Oct 02, www.cooltown.hp.com/mpulse/1002-firefighters.asp. [R Mathieson Nov 02] Rick Mathieson, “ultra-cool, ultra-controversial, ultra-wideband technology”, mpulse magazine, Nov 02, www.cooltown.hp.com/mpulse/1002-ultrawideband.asp. [Time Domain Website] Time Domain, www.timedomain.com/radarvision (last accessed Dec 10 2002) [UWB working group] ultra-wideband working group, www.uwb.org

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Appendix A Federal Communications Commission Washington, D.C. 20554 Revision of Part 15 of the Commission’s Rules Regarding Ultra-Wideband Transmission Systems Extract detailing UWB usage guidelines Imaging Systems: Provides for the operation of GPRs and other imaging devices under Part 15 of the Commission’s rules subject to certain frequency and power limitations. All imaging systems are subject to coordination with NTIA through the FCC. NTIA has indicated that coordination will be as expeditious as possible, requiring no longer than 15 business days, and may be expedited in emergency situations. The operators of imaging devices must be eligible for licensing under Part 90 of our rules, except that medical imaging devices may be operated by a licensed health care practitioner. Imaging systems include: • Ground Penetrating Radar Systems: GPRs must be operated below 960 MHz or in the frequency band 3.1-10.6 GHz. GPRs operate only when in contact with, or within close proximity of, the ground for the purpose of detecting or obtaining the images of buried objects. The energy from the GPR is intentionally directed down into the ground for this purpose. Operation is restricted to law enforcement, fire and rescue organizations, to scientific research institutions, to commercial mining companies, and to construction companies. • Wall Imaging Systems: Wall imaging systems must be operated below 960 MHz or in the frequency band 3.1-10.6 GHz. Wall-imaging systems are designed to detect the location of objects contained within a “wall,” such as a concrete structure, the side of a bridge, or the wall of a mine. Operation is restricted to law enforcement, fire and rescue organizations, to scientific research institutions, to commercial mining companies, and to construction companies. • Through-wall Imaging Systems: These systems must be operated below 960 MHz or in the frequency band 1.99-10.6 GHz. Through-wall imaging systems detect the location or movement of persons or objects that are located on the other side of a structure such as a wall. Operation is limited to law enforcement, fire and rescue organizations. • Surveillance Systems: Although technically these devices are not imaging systems, for regulatory purposes they will be treated in the same way as through-wall imaging systems used by police, fire and rescue organizations and will be permitted to operate in the frequency band 1.99-10.6 GHz. Surveillance systems operate as “security fences” by establishing a stationary RF perimeter field and detecting the intrusion of persons or objects in that field. Operation is limited to law enforcement, fire and rescue organizations, to public utilities and to industrial entities. • Medical Systems: These devices must be operated in the frequency band 3.1-10.6 GHz. A medical imaging system may be used for a variety of health applications to “see” inside the body of a person or animal. Operation must be at the direction of, or under the supervision of, a licensed health care practitioner.

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• Vehicular Radar Systems: Provides for the operation of vehicular radar in the 22-29 GHz band using directional antennas on terrestrial transportation vehicles provided the center frequency of the emission and the frequency at which the highest radiated emission occurs are greater than 24.075 GHz. These devices are able to detect the location and movement of objects near a vehicle, enabling features such as near collision avoidance, improved airbag activation, and suspension systems that better respond to road conditions. Attenuation of the emissions below 24 GHz is required above the horizontal plane in order to protect space borne passive sensors operating in the 23.6-24.0 GHz band. • Communications and Measurement Systems: Provides for use of a wide variety of other UWB devices, such as high-speed home and business networking devices as well as storage tank measurement devices under Part 15 of the Commission’s rules subject to certain frequency and power limitations. The devices must operate in the frequency band 3.1-10.6 GHz. The equipment must be designed to ensure that operation can only occur indoors or it must consist of hand held devices that may be employed for such activities as peer-to-peer operation.