Europe knows it has to act on impulse--that is, on "impulse radio," otherwise known as carrier-free or ultra-wideband (UWB) wireless technology. The European authorities are taking more time than their U.S. colleagues to consider whether UWB development and use will be permitted in Europe and, if so, what restrictions will apply. The aviation/air traffic management (ATM) community is more than a little interested in the outcome, which may be more restrictive than U.S. regulation. The eventual requirement also will apply to a more recent form of UWB, which uses multiband orthogonal frequency division multiplexing (MB-OFDM), a type of system that is not pulse based.
UWB is a radical and disruptive technology. It promises large economic benefits, particularly in consumer electronics, where it could be used to network data-intensive devices wirelessly. But there is a sting in the tail. UWB has the potential to interfere with a wide range of systems from radio astronomy to satellite communications to radio navigation equipment in aircraft.
Proponents say UWB won't cause these problems because it operates at very low power, normally well within the limits of background radio frequency (RF) noise. But tests by NASA and the National Telecommunications and Information Administration (NTIA) in the United States have shown that under certain circumstances it could interfere. If aggregated, UWB devices are used together, they could raise the general noise floor. This would make it harder for radio receivers to pick out faint signals such as GPS. Nor are the low-power devices that are being permitted (in the United States only, so far) the end of the story, since demand for increased ranges and power for UWB devices is bound to grow.
Following FCC's Lead
Europe seems likely to follow the FCC's lead in granting conditional approval for UWB to proceed. It knows that if it does not, it will face a tide of equipment that will be imported and used anyway, whether legally or not. Because UWB is seen as the next "killer technology" in consumer electronics, its momentum will simply be too powerful to resist. Better, it would seem, to swim with the tide while retaining some semblance of control by insisting on specific restrictions and standards.
Europe might indeed impose different restrictions from those mandated in the United States in light of its own particular circumstances. At the least, it probably will require modifications to the FCC's emissions mask, the technology layer that limits power that can be emitted in certain sensitive frequency bands.
Europe also will have to take greater care than the United States to avoid interference to third-generation (3G) mobile phones, a sector where, in some European countries, telecom service providers have had to pay enormous license fees for frequency allocations.
Europe first embarked on UWB coexistence studies in 2000. Now the matter has reached the European Commission (EC), which will consider the issue at various junctures this year. Influential in this process is the European Conference of Postal and Telecommunications Administrations (CEPT), which has been consulting with stakeholders and has reported its findings to the EC. CEPT's advice was based primarily on the work of its Electronic Communications Committee (ECC) and that body's Task Force 3 (ECC/TG3), which has prepared a detailed report on "The Protection Requirements of Radiocommunications Systems below 10.6 GHz from Generic UWB Applications." This "ECC Report 64," was issued in Helsinki, Finland, in February 2005.
Because neither UWB equipment nor measured UWB parameters were available, ECC/TG3 had to base its studies on theoretical data and projected characteristics provided by the UWB manufacturers. Moreover, the task force did not take into account potential mitigation techniques because they were still being developed. ECC/TG3 made some measurements in certain "victim" radio service bands, but these were limited, and the report admitted that much further practical work remained to be done.
The working group estimated that 98 percent of UWB devices would be used for home entertainment networking on wireless personal area networks (WPANs) and wireless local area networks (WLANs). Furthermore, 88 percent of all units would be used indoors. One potential source of problems, the group predicted, will be UWB "hot spots," where the densities of devices in use would be high.
Victim users of conventional radio services normally would experience the effects of UWB, if at all, as white noise, which usually would not be troublesome. However, the report drew attention to the danger that aggregations of devices could raise the noise floor and render faint signals, such as GPS, harder to detect.
Moreover, any noticeable increase in the level of noise can only mar service quality. Unfortunately, because UWB communications will be license-exempt, authorities will not be able to control the siting and density of the generic UWB devices likely to be in greatest use.
Nor will aggregation be the only problem: even a single device, finding itself on the boresight of the high-gain antenna of victim equipment, could degrade service because its emissions would be greatly amplified. This type of scenario might call for other mitigations, including physical separation.
More Stringent Limits
ECC/TG3 concluded that UWB--especially multiple emitters--could, indeed, affect aeronautical RF systems. It was particularly concerned about GPS, radar and some satellite-based services. TG3's view was that required power spectral density (PSD) limits proposed by the FCC for generic UWB devices, especially pulsed systems, would be inadequate to protect existing radiocommunications services.
According to Report 64, most of the services that were considered required limits to be more stringent, by about 20 to 30 dB. (Radio astronomy is particularly vulnerable; some of its bands require protection levels in the order of 50 to 80 dB). More protection is required for services using highly sensitive, narrowband receivers. Limits are needed for both average and peak powers, though an alternative for the latter is to limit pulse repetition frequency.
Naturally, a UWB industry unconvinced that even the FCC's mandated protection levels are necessary was not likely to welcome the CEPT/ECC findings. Leading players and their associations consider the findings to be unduly conservative. Some critics irritated the UWB industry because they would like to impose limits that would have devices pushing out less power than unintentional emitters, such as personal computers, MP3 players and mobile phones.
The European Telecommunications Standardization Institute (ETSI) also has been looking at UWB requirements for European Union (EU) countries, through its Task Group 31a. And individual European states have been conducting their own enquiries and consultations. Germany could be the next country to make legal the further development and use of UWB within its jurisdiction.
The tension between the desire to seize a promising economic opportunity and the need to protect existing services, particularly those safety-of-life services, extends to authorities in the UK. The UK Office of Communications (Ofcom), which is responsible for ensuring optimum use of radio spectrum, considers the FCC mask to be inappropriate and wishes to minimize in the UK the risks arising from use of equipment conforming to this specification.
Ofcom issued a consultative document and received responses from various interests, including aviation, during a three-month consultation period that ended on March 24. After analyzing the comments, Ofcom is due to communicate its final view to the European Commission, CEPT and the International Telecommunications Union (ITU) as part of the process of reaching a joint position for Europe. Ideally this would be within the context of a wider international consensus.
Ofcom's considerations are limited to generic, short-range emitters such as those likely to be embedded in future personal electronic devices (PEDs). It takes the view that other UWB-based systems--such as ground-probing radar, through-wall imagers and automotive anti-collision radars--would have to be licensed and therefore covered by separate legislation. While recognizing UWB's economic benefits, Ofcom has expressed concerns about interference to certain aeronautical systems, including radar.
Ofcom is not alone. In its response to the Ofcom's consultative document, the equivalent body responsible for frequency management in France, the Agence Nationale des Frequences (ANFR), expressed similar fears, adding that fixed satellite services and radio astronomy also could be affected.
It offered a crumb of comfort, however, for global navigation satellite systems (GNSS), pointing out that Galileo (Europe's GNSS, now under development) will be better able to co-exist with UWB than GPS because of Galileo's more robust, higher power signals. Like Ofcom, ANFR emphasizes the need for a European stance on UWB.
A Unified Approach
On this last point, the UWB industry agrees. It, too, favors a unified approach. Texas Instruments (TI), for one, supports Europe's desire for common restriction requirements, saying that regionally fragmented spectrum masks would add to cost. The company, which wants to market UWB products, believes that a proposed Ofcom revision of a mask already mooted by ETSI offers a viable way forward.
In its reply to the Ofcom consultation document, TI argues that since UWB technology is evolutionary, its evolution should be regulated so that it can coexist with future services, such as broadband wireless, as well as with existing services. The company believes that the UWB industry should collaborate with regulatory bodies to define common interference mitigation methods. TI appears content for UWB emissions to be constrained in bandwidth, average and peak power levels, maximum pulse repetition frequency and control parameters.
European airworthiness authorities have significant reservations about UWB technology. The UK's Civil Aviation Authority (CAA) first expressed its concerns after NASA and United Airlines conducted live tests a few years ago. The tests indicated a potential for UWB to compromise the operation of collision avoidance, instrument landing and satellite-enabled communications, navigation and surveillance (CNS) systems. At that time the CAA took the view that use of wireless PEDs might have to be banned on aircraft. It may have softened its stance since then, but the agency still sees protection of existing services as the priority.
Better Tests Needed
The CAA considers the tests conducted so far by Ofcom to be limited in scope, and it takes issue with certain economic justifications for UWB. It postulates, for instance, that, given the high financial value of a landing slot at London/Heathrow, a hypothetical failure of an approach radar due to the presence of wideband emissions, could prove expensive in terms of lost aircraft movements. CAA has particular concerns about UWB's effects on aeronautical radars and wants a special study into the matter.
In general the CAA and the pan-European Joint Aviation Authorities (JAA)/European Aviation Safety Authority (EASA), are in broad agreement on UWB issues. These agencies support a common European stance on UWB, but they would like to see it extended wordwide, since UWB-capable PEDs will be a global phenomenon. The CAA has queried Ofcom's proposed emissions mask, saying it has not proved that this will sufficiently protect existing services from interference.
UK's National Air Traffic Services Ltd. (NATS) worries about the prospect of license-exempt UWB devices operating across safety-of-life frequencies. It fears that by the time UWB interference becomes an issue of widespread debate, little protective action can be taken.
As it comments in its submission to Ofcom: "Even a single UWB device has been shown to cause harmful interference, and the cumulative effect of many such 'thinly spread' transmissions becomes a serious problem. We recognize that much technical work continues to be carried out into spectrum issues surrounding these emerging technologies."
Economics Over Risk?
NATS also fears that greater weight in the UWB argument is being given to market economics than to technical issues. The agency says the economic benefits of emerging technologies like UWB should not be allowed to outweigh the risk these systems might pose to traditional radio users through possible inappropriate spectrum management. It cautions Ofcom that certain courses of action will be irreversible, given the likely mass market applications for the new technologies. However, the ATM services provider welcomes Ofcom assurances that it will continue to deal rapidly with any interference to safety-of-life services.
Europe's air transport operators share concerns about UWB's potentially disruptive effects, even while accepting the technology's potential benefits, such as "less wired" cabins. For example, in its response to Ofcom's consultation paper, British Airways mentions potential adverse effects on radio altimeters (operating in the 4200-4400 MHz band) and microwave landing systems (5030-5150 MHz).
It cites several reports that highlight possible effects on aeronautical systems, including one from the International Civil Aviation Organization (ICAO). The airline advocates a cautious approach, citing the findings of several working groups, including the European Organisation for Civil Aviation Electronics' (EUROCAE) WG 58 and RTCA's SC202. These groups are studying the effects of increasing numbers of RF transmitters, including UWB, present in aircraft. British Airways also commends the ITU's ITU-R task group, which is working on the compatibility of UWB and radiocommunications services.
The UK-based airline advocates a provision that would have the UWB transmitters in PEDs able to be switched off and a visible indicator to show the transmitter's status. Indeed, it wants Ofcom to make such provision mandatory. It also favors more visible cooperation with the CAA and EASA, which should be regulating how airlines manage risk from a range of PEDs, not just UWB.
The air transport/ATM community is finding common cause over UWB with other interests that sense a threat. These include telecommunications, a sector that fears the compromising of existing and projected services, especially 3G mobile and satellite-based services. The European Telecommunications Network Operators Association (ETNO) has proposed that mitigation techniques adopted should be application-dependent.
Thus, an appropriate mix of limitations on indoor operation, frequency avoidance, duty cycle limitation, dynamic frequency control and power control, as well as emissions masking, would be selected for each specific application, whether the wireless interconnection of personal electronics, say, or wireless in-flight entertainment solutions. ETNO argues that such an approach will be essential if UWB and conventional radio systems are to coexist.
There are also possible biological effects to be considered from any prolonged and dense use of UWB.
Writing Is on the Wall
Which way the European Commission (EC) will jump on the UWB issue is not yet clear. As a senior EC official observed, UWB does not fit into the classical, frequency-oriented regulatory paradigm. But the EC does not wish to be seen to be blocking or delaying technologies simply because they do not fit an accepted paradigm. It knows the writing is on the wall and that UWB will soon start rolling out into the market, initially in a variety of PC, peripheral, consumer electronics and home entertainment devices.
In March the Federal Communications Commission approved the sale within the United States of certain indoor/handheld UWB products, albeit excluding the use of the 5030-5650 MHz band used by aircraft landing systems and weather radar. It would appear that, rather than attempting to buck the consumer trend, the EC might follow the FCC and give conditional approval for UWB to proceed. But it will be with safeguards, and those safeguards may well be different from those now applied in the United States.
In any case, all concerned are aware that future software-defined radio will change the paradigm again, providing a potential means to use all radio spectrum much more efficiently. So wise actions now can set the stage for the even larger decisions that will inevitably be called for as wireless technology advances still further.
At A Glance
Although Europe did not immediately follow the U.S. Federal Communications Commission's lead two years ago in granting conditional approval of the use of ultra-wideband (UWB) devices, it probably will take a similar step. However, that step may include different restrictions and/or, perhaps, greater restrictions. Clearly, many European agencies share a concern over UWB's adverse effect to existing radio frequency (RF) use. Along with the aviation industry and other spectrum users, here are some of the European organizations that are weighing the UWB issue:
-Electronic Communications Committee (ECC),
-European Aviation Safety Authority (EASA),
-European Commission (EC),
-European Conference of Postal and Telecommunications Administrations (CEPT),
-European Organisation for Civil Aviation Electronics (EUROCAE),
-European Telecommunications Network Operators Association (ETNO)
-European Telecommunications Standardization Institute (ETSI),
-France's Agence Nationale des Frequences (ANFR),
-International Telecommunications Union (ITU),
-Joint Aviation Authorities (JAA),
-UK's Civil Aviation Authority (CAA),
-UK's National Air Traffic Services Ltd. (NATS), and
-UK Office of Communications (Ofcom),