UK SG1
CP(01)27
SE21(01)117 Rev 4
Working Document on a Paper for Submission to ITU-R WP1A
CEPT Views and Identified Regulatory Issues on the Impact of UWB Systems
on Other Radio Services, in Particular the Passive Services
1. Introduction
Ultra-Wideband Transmission (UWB) systems will utilise spread spectrum technology.
Various modulation schemes will be used that will occupy a minimum bandwidth, normally
in excess of 500 MHz dependent upon the application. Due to the extremely large bandwidth
occupied, when compared to traditional radio applications, these devices would be expected
to operate with a power spectral density level close to the noise floor.
UWB is a new technology, which may require a new approach and thinking in the way it is
handled with regard to the regulatory definitions.
Communications as well as radar applications are foreseen as potential applications of UWB
technology and some of the applications envisaged are listed below: 
Automotive applications

High performance data communications systems

Consumer communications applications

Ground penetrating radar (GPR) systems

Consumer and industrial construction applications

Medical applications

Industrial gauges
Some of these applications, e.g. high performance data communications systems and car anticollision radar’s, are expected to operate with a high density of systems especially in densely
populated areas.
2. Technical Characteristics
UWB devices are expected to operate at frequencies above 1 GHz due to their requirement
for large bandwidth.
There are no specific frequency ranges that UWB systems will use, although the systems that
are currently proposed intend to use frequencies that are centred on 3.5 GHz, 6 GHz and 24
GHz
UWB can be characterised by its pulse repetition frequency, average power/1 MHz and peak
power in any 50 MHz bandwidth and relative bandwidth, which may be defined as the
quotient of the required (necessary) bandwidth and the centre frequency. Typical values are
larger than 0.25.
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Suggested transmitter in-band filtering at sensitive frequencies is not viable due to
unacceptable degradation of system performance.
The new UWB technologies will require certain minimum levels to be viable for the intended
applications.
Due to the generally low level of emissions from UWB equipment new measurement
techniques might need to be developed.
3. Effect on other services
There is a potential risk of interference with the proposed introduction of UWB systems,
especially as they may be deployed as license exempt devices. The potential of interference
to any radio service that operates in frequency bands above 1 MHz, from UWB devices
results from the large transmitted bandwidth plus the expected density of operation of the
devices. The interference levels that would be tolerable by the radio services under
consideration would be below the system’s intrinsic noise floor, in order to avoid any burden
on existing and currently planned services.
The potential victims are expected to be the point-to-area services that operate at the lower
frequencies, and the fixed service that operate at the higher frequencies. Of course, there are
some services such as the passive and safety services that will require particular consideration
and protection. The safety services, which include the aeronautical navigation service,
employ receivers that operate with low levels of wanted signal. The coverage area of an
aeronautical navigational aid (with a typical aircraft altitude of 10 km) would be about
160,000 km2 and the aircraft receivers would therefore be susceptible to low levels of
interference.
The effect on these other services, especially the passive and safety service’s that will require
particular consideration and protection, has still to be fully assessed. However it should be
noted that some of the UWB systems currently proposed will transmit as a requirement of
their bandwidth in bands that are covered by footnote S5.340 of the Radio Regulations.
S5.340 states that all emissions are prohibited in those frequency bands listed in the footnote,
which has resulted in discussion on the interpretation of S5.340 with regard to the proposed
introduction of UWB services and hence the possible implications.
Passive services undertake measurements of natural radiation, sometimes these are at very
low levels, and hence the protection required is in absolute terms. Footnote S5.340 is seen as
valuable regulatory tool for the protection of passive services in frequency bands where the
highest requirements of sensitivity and freedom from interference are required.
The risk to all radio services are enhanced, since many of the UWB proponents state that
certain regulatory concepts and terminologies may not be applicable to UWB transmissions
(e.g. centre frequency, necessary bandwidth, and spurious emission). Therefore the potential
risk to any radio service will vary according to their technical characteristics and operational
conditions as well as the aggregation of several devices.
The impact of UWB devices on a receiver level should not jeopardise the operation of the
services concerned. Since the interference from UWB devices may appear as an increase of
the background noise, the tolerable interference levels for the other radio services need to be
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defined very carefully. Depending on the increase in background noise of the receiver, this
will result in a decrease of quality of service in terms of a loss of capacity, coverage or
availability.
However the possibility of allowing UWB systems with necessary regulatory constraints
placed upon their operation should be investigated
Currently the parameters of the UWB devices are not clearly defined, and it is therefore
difficult to assess the probability of interference from these devices into existing services.
Especially in the case of the passive services, such as the radio astronomy service (RAS),
earth exploration-satellite service (EESS) (passive) or the space research service (SRS)
(passive), which are very susceptible to low-level interference. Also, an UWB device
generates wanted emission over a range of frequencies used by various services, which each
have different requirements and protection criteria and related regulations. Because of the
wide bands used, it will be hard to avoid generating intentional emissions within the passive
frequency bands to which footnote S5.340 applies.
Given the levels of sensitivity of the instruments used by the passive services and the fact
they typically operate by integrating a very low level of signal over time and across a
relatively large band. Even a very low level of interference spread across the whole band
could result in significant interference over the entire bandwidth of the instrument. This
would especially be the case when considering the aggregating factor of a number of UWB
devices, however the deployment density of the UWB devices are unknown at this time, but
for certain applications the densities are expected to be very high.
3.1
EESS Passive -- Radiometers
Basically, in radiometry levels of change are sought which are typically just above the noise
floor1. The risk of deploying these Ultra Wide Band (UWB) devices in bands where these
passive instruments operate, is that the noise floor could be elevated and therefore that the
typical characteristics sought after are being missed and thus making the equipment obsolete.
Given the size of the EESS footprint (typically in the order of 100 km2), the aggregating
factor of UWB devices would need to be considered.
The interference criteria for satellite passive remote sensing are given in Rec. ITU-R
SA.1029, which is currently under review.
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The rationale behind the working principle of radiometers is that every interaction between
a charged particle and energy must change the state of motion of the particle; every change
of motion of a charged particle gives rise to a radiated electromagnetic wave. Since
charged particles are the basis of all matter and all matter in the real world contains and is
receiving energy (i.e., is at a temperature above absolute zero), all matter must be
continually radiating electromagnetic waves.
When the energy in matter is high enough (i.e., when the temperature is high enough), the
radiation is directly observable as heat and light. Radio frequencies, though, are also being
radiated, and can be detected by the appropriate equipment.
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3.2
Radio Astronomy
The protection requirements of radio astronomy are based on the sensitivity of a typical
receiver used in an operational mode, which is representative of a large range of observations.
Celestial sources are observed over a huge range of power flux densities, and new and ever
weaker sources are regularly detected and analysed.
Additionally, astronomical sources do not transmit signals that obey any standard. The
scientifically most challenging projects are the ones, that lead to the detection of a new class
of objects, as has happened on a number of occasions in radio astronomy. In order to enable
future detection of the unexpected, a few clear windows in the radio spectrum, free from any
artificial transmission, are a minimal requirement. Footnote S5.340 contains an agreed set of
such bands.
4. Regulatory Issues
In order to accommodate UWB systems the following regulatory issues have to be addressed
within the ITU framework: 
It is currently unclear in which service categories UWB can be classified.

Alternative ways may be required to define the necessary bandwidth that can be applied
to UWB systems.

Consider the applicability of the current ITU-R Recommendations SM.329-9 “Spurious
Emissions”, SM.1539 “Variation of the boundary between the Out-of-Band Domain and
Spurious Domains required for the application of Recommendations ITU-R SM.1540
AND ITU-R SM.329”, SM.1540 “Unwanted Emissions in the Out-of-Band Domain
falling into adjacent allocated bands”, SM.1541 “Unwanted emissions in the Out-of-Band
Domain”, SM.1542 “The Protection of Passive Services from Unwanted Emissions”,

UWB signals can not be considered as spurious emissions due to continuous frequency
coverage over the whole used band. Spurious emissions are usually sporadic emissions
and do not cover intentionally the whole adjacent spectrum.

The assumption about average power used in compatibility studies put forward by the
manufacturer may not always be sufficient to describe the characteristics of the UWB
signal. Depending on the repetition rate of the UWB signal and of the bandwidth of the
victim receiver the peak power may be more appropriate to be considered.

UWB systems usually produce a very wideband noise like signals. UWB are designed to
achieve a very high spatial bit rate (for example Mb/s/km2). If the density of UWB
equipment is high, i.e. this spatial bit rate covers a considerable area, victim services
employing wide bandwidths may suffer from increased aggregate interfering power.

It should be mentioned that all emissions are prohibited in certain bands (according to
footnote S5.340 of RR). It should also be pointed out, that there are many other radio
services that will also require to be protected.
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
It should also be mentioned that the assessment of the interference potential is
complicated by the fact that not one single propagation model exists that covers the whole
frequency range, particularly for low frequencies.

Detailed compatibility studies are being undertaken within the CEPT on UWB systems
and other radio systems in the same frequency bands. In this context ITU-R Rec RA.769,
SA. 1029 and Footnote S5.340 are taken into account.

Consideration of the aggregation effect from a large number of UWB-units should be
taken into account when defining suitable emission levels.
5. Request to ITU-R Working Party 1A
This contribution tries to summarise the impact of UWB technology on regulatory issues and
attempts to stimulate discussion about open questions, which require to be solved before the
introduction of UWB systems in the “frame” of the ITU RR.
The CEPT wishes to indicate that the present regulations in the ITU-R do not fully cover all
aspects and requirements, which might be necessary to protect existing Radio Services.
It is understood that UWB development is progressing rapidly and therefore the issue needs
to be addressed as a matter of urgency.
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