INTERNATIONAL TELECOMMUNICATION UNION
RADIOCOMMUNICATION
STUDY GROUPS
Source:
Document 1-8/TEMP/11-E
23 January 2003
English only
Documents 1-8/12, 1-8/16, 1-8/17, 1-8/19, 1-8/21, 1-8/23, 1-8/32, 1-8/35 and 1-8/45
TG 1-8 Working Group 1
WORKING DOCUMENT TOWARD A PRELIMINARY DRAFT NEW
RECOMMENDATION ITU-R SM.[UWB.CHAR]
Characteristics of ultra-wideband (UWB) devices
(Questions ITU-R 226/1 and ITU-R 227/1)
The ITU Radiocommunication Assembly,
considering
a)
that UWB devices are being considered for operation across numerous frequency bands and
may affect, simultaneously, several services;
b)
that UWB emissions spread over a very large frequency range;
c)
that UWB technology can be integrated into many applications such as communication
devices and radar imaging capabilities for public protection, construction, engineering, science, law
enforcement, consumer devices, and transportation systems such as near collision avoidance and
intelligent transportation system applications;
d)
that these applications could potentially result in mass usage of devices using UWB
technology in various environments (home, office, store, industry, public places, etc.) where
radiocommunication services may have already been deployed and are in operation;
e)
that the spectrum requirements and operational restrictions for devices using UWB
technology may vary according to their application;
f)
that studies are being undertaken of the impact of UWB devices and applications on the
electromagnetic environment; and
g)
that information on the technical and operational characteristics of UWB devices and
applications is needed for these studies,
recommends
1
that the definitions related to UWB devices contained in Annex 1 be used in discussions
regarding UWB devices and systems;
2
that the key features regarding UWB technology contained in Annex 2 be used in
discussions and studies regarding UWB devices and systems;
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3
that the operational characteristics devices using UWB technology contained in Annex 2, as
well as other relevant data and information, be used to initiate the studies called for in Questions
ITU-R 226/1 and ITU-R 227/1;
4
that the technical characteristics of devices using UWB technology contained in Annex 2,
as well as other relevant data and information, be used to initiate the studies called for in Questions
ITU-R 226/1 and ITU-R 227/1; and
Annex 1
1
Definitions
1.1
UWB definitions
Ultra-wideband (UWB) emission: is radio frequency energy that is intentionally generated and
transmitted by radiation or induction that spreads over very large frequency range that meets the
following criteria:
(fH – fL)/ fC > yy
[and/or]
(fH – fL)  zz
where:
yy –
zz –
fH –
fL –
fC –
fractional bandwidth is greater than [0.20],
minimum limit of bandwidth is [500 MHz],
upper frequency of the –10 dB emission point,
lower frequency of the –10 dB emission point,
centre frequency of the emission.
NOTE – UWB is typically generated by direct impulse excitation of the transmit antenna or by
using a spectrally filtered approach.
UWB transmitter: An intentional radiator that has a bandwidth equal to or greater than [500 MHz]
[and/or] a fractional bandwidth greater than [0.2].
UWB bandwidth: is the band bounded by the frequency points that are –10 dB below the highest
radiated emission, as based on the complete transmission system including the transmit antenna.
The upper and lower –10 dB frequency points are referred to as f H and f L , respectively.
UWB centre frequency: The centre frequency, fC, of an UWB emission is given by, fC= (fH-+fL)/2.
UWB fractional bandwidth: The fractional bandwidth of an UWB emission is defined as:
FBW(%) = 2(fH – fL)*100 / (fH + fL)
Activity factor: for applications that do not require the devices to operate continuously, this
represents the fraction of time during which an UWB device is actively transmitting.
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Pulse transmitter duty cycle: for pulse generated UWB, during the period in which the UWB
transmitter is active, this is the ratio of the impulse duration to the time between the start of two
adjacent impulses.
Peak to average ratio: [to be defined]
UWB radar imaging system: A UWB system that is used to obtain images of obstructed objects.
This includes in-wall/through-wall detection, ground penetrating radar, medical imaging,
construction and home repair imaging, mining, and surveillance systems.
UWB ground penetrating radar (GPR) system: A UWB radar system that operates only when in
contact with or within close proximity to the ground for the purpose of detecting or obtaining
images of underground objects.
UWB communication system: a communication system that uses UWB technology.
UWB measurement system: a measurement device that uses UWB technology.
UWB vehicular radar (VR) system: A UWB directional radar system mounted on terrestrial
transportation vehicles to detect the location and movement of persons or objects near a vehicle to
avoid collision and enable other features.
1.2
Other definitions
Editorial note: The definitions given below are derived from the present definitions of the Radio
Regulations. These definitions were developed for conventional radiocommunication systems.
Further study is necessary before using these definitions also for emissions from UWB applications.
[UWB out-of-band emission: Emission on a frequency or frequencies immediately outside the
UWBnecessary bandwidth which results from the modulation process, but excluding spurious
emissions.
UWB out-of-band domain(of an UWB emission): the frequency range, immediately outside the
UWB bandwidth but excluding the UWB spurious domain, in which UWB out-of-band emissions
generally predominate.
UWB spurious emission: Emission on a frequency or frequencies which are outside the
UWBnecessary bandwidth and the level of which may be reduced without affecting the
corresponding transmission of information. UWB spurious emissions include harmonic emissions,
parasitic emissions, intermodulation products and frequency conversion products, but exclude UWB
out-of-band emissions.
UWB spurious domain (of an UWB emission): the frequency range beyond the UWB out-of-band
domain in which UWB spurious emissions generally predominate.
UWB unwanted emissions: Consist of UWB spurious emissions and UWB out-of-band emissions.]
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Annex 2
1
Key features of UWB technology
1.1
UWB applications and operational characteristics
UWB technology can be integrated into very many applications. Some examples are included in the
Table below:
TABLE 1
Applications and operational characteristics of UWB systems
UWB system
System description
Operational characteristics
– Occasional or continuous use.
1 Radar imaging system
A system that is used to obtain images of obstructed objects.
This includes wall/through-wall detection, ground penetrating
radar, medical imaging, construction and home repair imaging,
mining, and surveillance systems.
Ground
penetrating radar
systems
A radar imaging system that operates only
when in contact with or within close
proximity to the ground for the purpose of
detecting or obtaining images of
underground objects.
– Occasional use at infrequent
intervals.
Wall radar
imaging systems
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.
– Occasional use at infrequent
intervals.
Through wall
radar imaging
systems
Designed to detect the location or
movement of persons or objects that are
located on the other side of a structure such
as a wall.
– Occasional use at infrequent
intervals.
Surveillance
systems
Operate as "security fences" by establishing
a stationary RF perimeter field and
detecting the intrusion of persons or objects
in that field
– Continuous outdoor and
indoor use.
Medical systems
May be used for a variety of health
applications for imaging inside the body of
a person or an animal
– Indoor occasional use.
– Emission is directed towards
the ground.
– Emission is directed toward
a wall.
– Emission is directed towards
a wall.
– Emission is directed towards
a body.
2 Vehicular radar systems
A directional radar system mounted on terrestrial transportation
vehicles to detect the location and movement of objects near
a vehicle to avoid collision and enable other features.
– Users are on the move.
3 UWB measurement systems
A measurement device that uses UWB technology.
Stationary indoor/outdoor use.
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– High-density use is expected
on highways and major roads.
– Terrestrial transportation only.
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4 UWB communication systems
A communication system that uses UWB technology.
– High-density use is expected
in office buildings and
business cores.
– Some applications have
occasional use such as a UWB
wireless mouse; Others will
operate for most of the time
such as a PAN in an office
building.
– Mobile indoor and outdoor
use, and indoor stationary use.
1.2
UWB general features
Some of the features of UWB wireless communication systems in comparison with conventional
radiocommunication systems are:
1)
Low Susceptibility to Multipath Fading: Multipath within and around buildings causes
significant deterioration in the performance of conventional communication systems.
Significant multipath creates great difficulty for conventional systems with precision
tracking. In environments with a great deal of clutter, conventional communication systems
have difficulty in resolving targets. Especially inside buildings, the combined effects of
multipath and diffraction phenomena cause a degradation in the propagation characteristics
of conventional radio. By comparison some UWB techniques exhibit much superior
performance indoors. They enable positioning accuracy better within a few centimetres.
Because UWB communication systems have bandwidths exceeding 0.5 GHz they are
capable of resolving multipath components with subnanosecond differential delays.
Multiple reflections with sub-nanosecond delays can be resolved and added constructively
to provide gain over a single direct path in the multipath environment.
2)
Immunity to Interference: UWB wireless communication systems exhibit excellent
immunity to interference from conventional radiocommunications systems (because …).
3)
Secure Communications: Because UWB signals can be made noise-like, communication
using transmitter/receiver pairs with a unique timing code at millions of bits per second,
have such low energy and spectral density below the noise floor of conventional receivers,
and occupy such a wide bandwidth, they are more covert and potentially harder to detect
than conventional radio. These advantageous characteristics result in UWB transmissions
with a very low extant RF signature, providing intrinsically secure transmissions with low
probability of detection (LPD) and low probability of interception (LPI).
4)
System Simplicity: The relative simplicity of the UWB architecture compared to the
super-heterodyne architecture transceiver is due to the fact that the UWB transceiver has no
phase-lock loop synthesizer, voltage-controlled oscillator (VCO), mixer or power amplifier,
which translates to lower material and assembly costs.
5)
Advantageous for Multi-User High-Speed Short-Range Communication Systems: UWB is
advantageous for high-speed, large bandwidth, high processing gain multi-user short-range
communication systems. A large number of users can share the same bandwidth for speed
greater than 100 Mbps. UWB radio signals inherently possess very fine time resolution.
As a result it is possible to resolve multipath components down to differential delays on the
order of tenths of a nanosecond (corresponding to less than 1-foot path differentials).
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This significantly reduces fading effects in indoor environments and results in fade margin
reduction. The reduction of required fade margins and power spectral density of the UWB
spectrum makes UWB technology a favorable technology for low power and short-range
communications, as required for operation in indoor environments. A very important
advantage of UWB radios is their huge processing gain, a measure of a radio's resistance to
jamming.
Challenges related to deployment of UWB radiocommunication systems in terms of interference
issues that UWB radio systems will encounter include coexistence with radiocommunication
services (e.g. GPS), and upper and lower bounding the UWB transmitter power - upper bounding
for interference regulation of UWB transmissions, and lower bounding for obtaining the UWB
transmitter power necessary for a given data rate. Among the challenges of UWB:
1)
UWB emissions spread over very large frequency bandwidth and require up to a few GHz
to operate.
2)
There are concerns about compatibility between UWB devices and radiocommunication
services especially the aggregate impact on the noise floor and potential interference to
existing radiocommunication services.
3)
UWB wireless communication systems intend to use spectrum allocated to other
radiocommunication services on license-exempt basis. There are concerns about potential
aggregate interference and UWB emissions in passive bands (EESS and radioastronomy),
auctioned bands, and other licensed bands. Among the challenges ahead is finding suitable
spectrum and a way to introduce the UWB technology without causing harmful
interference to other radiocommunication services.
4)
Requires accurate synchronization. However, systems designers are able to resolve this
issue.
5)
Some applications require special antennas to influence the shape of the radiated signal.
1.3
UWB communication system capacity
In the context of a communications system application, the UWB technology may be considered in
relation to the theoretical capacity of the channel. The system capacity may be calculated from the
"Shannon" relation. This relation shows that the channel capacity (bit/sec) equals the channel
bandwidth multiplied by the logarithm (base 2) of one plus the signal to noise ratio. This relation
apparently offers a theoretical capacity advantage to wide band systems. However, for
a low-powered UWB system overlaid on existing spectrum assignments, there is only a theoretical
advantage over WLANs at ranges of a few metres. The sharing of the spectrum with other users
reduces the practical system capacity significantly.
The following figure illustrates the theoretical capacity for a UWB system and a conventional
WLAN system assuming the noise (–154 dBm/Hz) is 20 dB above the thermal noise floor of
–174 dBm/Hz. Noise of this order must be included to account for both the intra- and inter-system
interference from other users of the spectrum. It can be seen that under these practical conditions,
the theoretical capacity advantage of the UWB system is only for ranges less than about 2 metres.
In the illustration, the WLAN system is operating at 2.4 GHz with a power spectral density of
10 mW per MHz (with a total emission of about 200 mW) and a 20 MHz bandwidth. The UWB
system is centred at 5 GHz with a power spectral density of –41.3 dBm/MHz (with a total emission
of about 150 microwatts) and a 2 GHz bandwidth. The propagation model uses line-of-sight
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(i.e. square law) out to a distance of 2 metres and fourth power beyond that1. The receiver is also
confined such that only the energy in the 20 MHz or 2 GHz allotted channel bandwidths is
considered.
FIGURE 1
Illustrating UWB and WLAN theoretical channel capacity
10000
(Shannon) Channel Capacity
C (Mbit/s)
1000
100
10
WLAN
1
1
0.1
UWB
Distance (metres)
10
100
2
Transmission characteristics of UWB devices and systems
2.1
Communications and Measurement Systems
One administration has approved regulations, including operating restrictions, authorizing the use
of UWB devices on an unlicensed basis for communications and measurement applications. The
characteristics given in Table 2 provide an example of three products that are being designed to
operate under those regulations.
TABLE 2
Characteristics of some UWB communications devices
Device A
Device B
Device C
–41.3
–41.3
-41.3
Lower –20 dB and –10 dB
emission limits (GHz)
3.1, 3.6
 3.1
(–10 dB down)
3.1, 3.6
Upper –10 dB and –20 dB
emission limit (GHz)
9.6, 10.1
 10.6
(–10 dB down)
9.6, 10.1
Antenna pattern
Omni
Omni
Omni
Pulse rate (Mpps)
> 500
1
>1000
Bit rate (Mbps)
 100
 40
 500
Max. ave. eirp (dBm/1 MHz)
____________________
1 This is consistent with wide band measurements reported, for example, by Ghassemzadeh et al,
"A statistical path loss model for in-home UWB channels", First IEEE Conference on UWB
Systems and Technologies, UWBST2002, Baltimore, May 2002, Figure 7.
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Range (m)
~10
< 100
4-10
Max. ave. eirp (dBm/1 kHz)
in 960-1 610 MHz
–90
–85.3
-90
Max. ave. eirp (dBm/1 MHz)
in 960-1 610 MHz
<–90
–75.3
-90
Max. ave. eirp (dBm/1 MHz)
in 1 610-3 100 MHz
<–63.3
–53.3
-63.3
Device A is intended for operation within an office or home applications for transmission of data up
to 100 Mbps. It is also intended for operation between hand held devices that may be outside and
that do not employ a fixed infrastructure. Such applications include links among personal digital
assistants (PDA) or lap top computers. Within a LAN, it may carry multiple digital video signals
among components of a video system such as between a video camera and a computer, between
a cable set-top box and a TV, or between a high-end plasma display and a DVD player.
Device B is a multi-purpose device intended for use indoors for industrial, commercial, and
consumer applications where communications, precision positioning or radar sensing is required.
The device can be configured to operate over a range of data rates. The operating range depends
upon the data rate.
Device C is intended for operation within an office or home applications for transmission of data up
to 500 Mbps. These higher data rate devices are intended to provide wireless connectivity for many
of the same applications as Device A, but also serve to provide wireless cable replacement for highspeed wired connections such as USB or IEEE 1394.
2.2
Vehicular radar systems
One administration has approved regulations authorizing the use of UWB devices on an unlicensed
basis for vehicular radar applications in the band surrounding 24 GHz. The characteristics given in
Table 3 provide an example of products that are being designed by several companies to operate
under those regulations. UWB vehicular radar systems use higher frequency bands than those used
by UWB communications systems. These devices are being designed 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. Accordingly,
UWB vehicular radar systems are being designed to address a high percentage of all causes of
traffic accidents.
Vehicular radars emit an UWB signal over a well-defined frequency range, and the spectral
emissions are mainly defined by the modulation characteristics and additionally by resonant
components such as antennas.
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TABLE 3
Characteristics of some UWB vehicular radar devices
Parameter
Value
Centre frequency (GHz)
~24.125
Max. PSD (eirp) (dBm/1 MHz)
–41.3*
–10 dB occupied bandwidth (GHz)
Between 22.125 and
26.125
Pulse repetition frequency (MHz)
0.1 – 5
Max. peak power (eirp)
(dBm/50 MHz)
Antenna pattern
Mounting height (m)
Range (m)
Target separation (cm)
0
Directional
~ 0.50
~ 20
15 - 25
* Regulations adopted by the administration require that
emissions in the 23.6-24 GHz band at angles of 38º or greater
above the horizontal plane be attenuated below this level by
25 dB. For equipment authorized, manufactured or imported
on or after January 1, 2005, the required attenuation applies
to emissions at angles of 30º or greater. On January 1, 2010,
the required attenuation increases to 30 dB, and on January 1,
2014, it increases to 35 dB. This level of attenuation can be
achieved through the antenna directivity, through a reduction
in output power or any other means.
Spectrum sharing calculations for vehicular radars should take into account the peak car density, the
percentage of the Earth's surface where those densities are achieved, and the market penetration of
UWB vehicular radars over time.
3
Technical characteristics of UWB devices
Editorial note: This section draws on summarized material from a number of references. Relevant
material from these references will be incorporated into the present text for clarification. A list of
abbreviations and references will be appended at the end of this PDNR.
3.1
UWB spectra
Commonly used UWB signals generated by time hopping and PPM have numerous spectral peaks
and line spectra which are likely to cause interference problems. The choice of sequences that have
lowered PSD in certain frequency bands is important since it could enable UWB systems to co-exist
with other radiocommunication systems. Another issue is the choice of sequences that not only
have good correlation properties and flat spectra, but which are also amenable to rapid acquisition
techniques.
Within an envelope that is determined by the Fourier transform of the time domain pulse shape,
an appropriate choice can allow for a better control of the frequency content of the radiated UWB
emission. This can offer better coexistence with other radiocommunication systems. The spectrum
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can be made closer to white by randomizing the actual transmission time of each monocycle pulse
by a shift over a large time frame by a code, most commonly a pseudo-random noise code
sequence.
The timing jitter smoothes the spectrum of UWB emissions. In the case of no jitter the spectrum
contains only spectral lines. When timing jitter is used it flattens the spikes.
3.2
UWB modulation schemes
The choice of the UWB modulation scheme impacts the power spectral density of the radiated
signal and consequently its compatibility. Certain modulation techniques can offer better
coexistence among UWB systems and with other radiocommunication systems. Time-modulated
UWB communication systems offer high immunity to multipath fading.
Some modulation schemes exhibit advantages when used for UWB transmission in certain
environments. For example, biphase modulation yields an advantage of 3 to 6 dB over TH-PPM in
multipath-free environments. It also has a peak power to average power ratio of less than 3
(compared to sine wave, with a ratio of 2). This leads to efficient transmitters and use of low-cost,
low-power circuitry.
Biphase (BPM) and hybrid modulation (BPM and PPM) have the same power spectral densities
containing only continuous spectra and whereas the PPM UWB signals always have spectral lines.
Also direct sequence modulated impulse trains can give smoother and lower power spectral density
(PSD) levels whereas using time-hopped sequences does not improve the PSD. It is suggested that
the use of hybrid modulation can avoid the discrete spectra while allowing the exploitation of
benefits of PPM such as noncoherent reception. One way to reduce the interference for PPM UWB
signals is to increase the period of the impulse train.
Time modulated UWB (TM-UWB) combined with a correlator receiver enables the receiver to
acquire, track and demodulate UWB transmissions that are well below the noise floor. Due to the
combination of random time modulation, pseudo-random coding, and a correlating receiver,
TM-UWB radios have a great immunity to interference from conventional radiocommunication
signals.
Pulse position modulation (PPM) distributes the RF energy more uniformly across the frequency
band, smoothing the power spectral density of the transmitted signal. Time modulation by the PN
code sequence makes the power spectral density more like pure white noise and increases system
capacity. Assigning a unique PN time hopping code to each user can provide a system with a very
large number of channels.
3.3
Multipath effects
It is noted that UWB systems are resistant to multi-path fading. This is because the very narrow
pulses of UWB waveforms enable the multiple reflections to be resolved independently rather than
combining destructively at the receiver.
One of two conditions must be present in a time-modulated system for multipath effects to exist.
Either: (1) the multipath pulse must travel a distance less than the pulse width times the speed of
light–about one foot or 0.3 metres for a pulse one nanosecond wide (i.e., [1 ns] x [300,000,000 m/sec]);
or (2) the distance that the multipath pulse travels equals the interval of time between pulses times the
speed of light, times an integral number (e.g., for a 1 Mbps data rate that would be equal to travelling
an extra 300, 600, 900, etc. metres), resulting in interference between pulses. However, the
pseudorandom time modulation decorrelates the pulses. The occurrence of either of these conditions is
highly improbable, and the pseudorandom time modulation obviates the second of these.
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3.4
RAKE receivers
During propagation a subnanosecond pulse is dispersed resulting in Rayleigh fading in the
frequency domain. However, in TM-UWB radiocommunications each of these reflections is
an independent signal so a RAKE receiver can then be used to coherently add the energy in each of
the pulses that are received from each of the multipath components to provide a gain over single
path reception.
For outdoor communications, RAKE receivers can be used to receive and resolve multipath
components measuring many microseconds. However, the multipath differential delays in the
nanosecond range due to transmission over indoor channels cannot be resolved in the relatively
narrowband conventional channels.
A close examination of measured UWB waveforms taken in standard commercial office buildings
shows that a RAKE receiver would have many suitable lock points, so such coherent addition of the
energy from the individual RAKE elements would increase the SNR. Destructive signal
interference due to reflections can occur, but this rarely happens. In any case, such destructive
signal interference can be ignored due to the large number of resolvable reflections providing
usable signals that can be combined in a RAKE receiver. Spatial diversity provided by multipath
allows UWB signals to propagate around obstacles that would otherwise attenuate them, so a
RAKE receiver implementation should always gain from multipath propagation. Indeed, the large
number of multipath signals caused by clutter in an in-building environment enables an
improvement of performance by 6-10 dB using a RAKE receiver. The number of multipath signals
required by a RAKE receiver for such performance gains has been found to be greater than 5 and
fewer than 50 in a variety of environments. The result is that UWB radiocommunication systems
can operate at lower RF power than narrowband systems.
3.5
Emission masks
3.5.1
FCC UWB emission mask
The FCC has approved UWB different spectral masks depending on the application characterize the
new UWB emission limits. Thus, there are spectral masks for: Wall imaging & medical imaging
systems, for thru-wall imaging and surveillance systems and finally for communication and
measurement systems (indoor and outdoor). Although the interference potential from UWB
imaging and surveillance systems are not to be underestimated, the following estimations will
consider only the UWB communication and measurement systems since these last systems are
expected to follow the strongest deployment and will represent about 98 % of the market. The
spectral masks for Communication and Measurement systems are depicted below in Figure 2 and
Figure 3. The emission levels are specified in dBm/MHz.
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FIGURE 2
FCC UWB emissions limits for indoor Communication and Measurement systems with centre
frequencies greater than 3.1 GHz
FIGURE 3
FCC UWB emissions limits for outdoor Communication and Measurement handheld systems
with centre frequencies greater than 3.1 GHz
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3.5.2
CEPT Masks
3.5.2.1
Modified FCC Mask
The CEPT considered a modification to the FCC UWB masks shown in Figures 2 and 3. They
proposed that below 960 MHz, the emission limit be a flat line of -75 dBm/MHz. This modification
was proposed in order to protect the numerous radiocommunication applications in Europe that are
centred at frequencies below about 1 GHz.
3.5.2.2
One proposed CEPT slope mask
FCC issued a staircase spectrum mask limit for radiated power density. UWB cannot utilize the
staircase mask fully and CEPT therefore is considering the use of a sloped mask instead. The
advantage of this mask is:
a)
a slope offers more interference protection to critical sensitive services operating below
3.1 GHz and above 10.6 GHz;
b)
a slope itself does not reduce the performance of UWB products.
At low frequencies, an attenuation roll-off for the proposed mask meets FCC's requirement at
3.1 and 1.66 GHz with a radiated power density limits of –51.3 dBm/MHz and –75 dBm/MHz
respectively.
At high frequencies the proposed spectrum mask meets FCC's requirement at 10.6 GHz with
a radiated power density limit of –51.3 dBm/MHz. The roll-off factor at high frequencies is a mirror
of the low frequency slope.
Two different spectrum masks for radiated power density are given for indoor and outdoor use
respectively. The mask for outdoor use is 10 dB lower than the indoor mask.
Proposed spectrum masks for indoor and outdoor use are shown in Table 4 below:
TABLE 4
Maximum UWB band-edge mask for average power density
Frequency, GHz
Power type
f < 3.1 GHz
3.1 GHz < f < 10.6 GHz
f > 10.6 GHz
dBm/MHz
dBm/MHz
dBm/MHz
Type I.
(Indoor use)
–51.3 + 87 log (f/3.1)
–41.3 dBm/1 MHz
–51.3 + 87 log (10.6/f)
Type II.
(Outdoor use)
–61.3 + 87 log (f/3.1)
–41.3 dBm/1 MHz
–61.3 + 87 log (10.6/f)
It should be noted that, in addition to this band-edge emission mask, all emissions are prohibited in
bands covered by ITU-R footnote 5.340.
Graphical representations of the indoor and outdoor Slope Masks are given in Figure 4 and Figure 5
below. These preliminary slope masks are at this stage in logarithmic scale instead of linear scale.
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FIGURE 4
Indoor CEPT slope mask
Indoor CEPT slope mask
FIGURE
4formaximumradiatedpowerdensity,dBm/MHz
Figur
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Note 1: Current measurement technology prevents measurements below –75 dBm in a one MHz bandwidth
FIGURE 5
Outdoor CEPT slope mask
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Note 1: Current measurement technology prevents measurements below –75 dBm in a one MHz bandwidth.
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5
Features of UWB devices and other short-range wireless communication devices
This section presents technical comparison between wireless short-range communication devices
using UWB technology and other technologies: Bluetooth, IEEE 802.11, etc.
UWB is capable of speeds between 400 and 500 Mbps and is a candidate technology for high-speed
wireless Personal Area Networks (IEEE 802.15.3a). Although the upper protocol stack associated
with the UWB transmissions may be ultimately similar to Bluetooth, (also a WPAN) the physical
layer is very different, as UWB usually transmits information based on a sequence of impulses
rather than a modulated carrier. As a consequence of the pulsed nature of the emissions, compared
to conventional wireless systems which use a modulated carrier, UWB can operate with very low
power consumption. In addition, as a consequence of the wide frequency bandwidth associated with
the short time duration of the emissions, UWB provides an unusual capability for penetration in
cluttered environments, with a capability to penetrate walls, obscurants such as mist, fog, and
foliage.
An additional attraction for the use of UWB is that the radio architecture is significantly simplified.
Compared with a superhetrodyne architecture and complex IF filtering the UWB radio operates at
baseband. The simpler radio architecture translates to a smaller die size when manufactured on
a semiconductor substrate.
In general, short-range communication devices can be classified into Wireless LANs (WLANs) and
Wireless PANs (WPANs). WPANs are differentiated from WLANs by their smaller area of
coverage, ad-hoc only topology, plug and play architecture, support of voice and data services,
and low power consumption.
Bluetooth is designed for quick, seamless short-range networks and is designed to operate as
a Wireless Personal Area Network (WPAN), as defined in IEEE 802.15.1. Bluetooth operates in the
2.4 GHz ISM band and uses FHSS.
The IEEE 802.11b and subsequently 802.11a standards are designed for infrequent mobility,
IP-based data transmission, medium range, and high data rate. These features make them ideal for
WLANs.
Bluetooth has a shorter range and lower throughput than 802.11, which results in a lower power
consumption in comparison to 802.11. This feature is attractive for the battery-powered devices
commonly used in WPANs.
The spatial capacities of the short- and medium-range IEEE 802.11 and Bluetooth standards are
different from the spatial capacity of UWB communication systems. Three 22 MHz IEEE 802.11b
systems can operate without interference in a circle of radius 100 metres, each offering a peak data
rate of 11 Mbps, which yields a spatial capacity of about 1 000 bits/sec/square-metre. Whereas 10
Bluetooth "piconets" with an aggregate peak over-the-air speed of 10 Mbps can operate
simultaneously in low-power mode in the same rated 10-metre range circle, yielding a spatial
capacity of about 30,000 bits/sec/square-metre. Twelve IEEE 802.11a systems, each with a peak
speed of 54 Mbps, can operate simultaneously with minimal degradation within a rated 50-metre
circle, in the 200 MHz of available spectrum within the lower part of the 5 GHz U-NII band, to
provide an aggregate speed of 648 Mbps and a spatial capacity of about 83,000 bits/sec/squaremetre. By comparison, based on measurements by one developer of measured peak speeds of over
50 Mbps at a range of 10 metres, it was projected that six UWB systems could operate with
minimal degradation at the 10-metre range, yielding a projected spatial capacity of over 1,000,000
bits/sec/square-metre, clearly a huge increase over the other technologies.
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TABLE 5
Technical comparison between wireless UWB communication devices
and other short-range communication devices
Data rate
Range
Frequency
band
Power level
(e.i.r.p.)
Modulation
type
Classification
Spreading
technique
Specification
Ultra-Wideband
Communication
Up to
500 Mbits/s
~15 m
TBD
TBD
PPM/Others
Personal Area
Network, etc.
(See Section 2)
Impulse
transmission
IEEE 802.15.3a*
Bluetooth
700 kbits/s
~ 15 m
ISM 2.4 GHz
Class 1: 20 dBm
Class 2: 0 dBm
GMSK
Personal Area
Network
Frequency
Hopping
IEEE 802.15.1
802.11a, RLAN
Up to
54 Mbits/s
~ 50 m
5 GHz1
Max1: 200 mW to up
to 1W
16 QAM,
64QAM,
BPSK
QPSK
Local Area
Network
OFDM
IEEE 802.11a
Rec. ITU-R
M.1450
802.11b, RLAN
Up to
11 Mbits/s
~100 m
ISM 2.4 GHz
Max. 100 mW to up
to 2W
CCK
(8 Complex
Chip
Spreading)
Local Area
Network
DSSS
IEEE 802.11b
Rec. ITU-R
M.1450
ETSI EN 300 328
802.11g, RLAN
Up to
54 Mbits/s
~100 m
ISM 2.4 GHz
Max. 100 mW to up
to 2W
16 QAM,
64 QAM,
BPSK
QPSK
Local Area
Network
OFDM, DSSS
IEEE 802.11g
ETSI EN 300 328
802.15.4 Zigbee
Alliance
< 250 kbits/s
10-75 m
ISM 2.4 GHz,
915 MHz,
868 MHz
TBD
Prelim spec:
early 2003
Low Power
Personal Area
Network
DSSS
IEEE 802.15.4
HiSWANa
Up to
54 Mbits/s
~50 m
5.15-5.25 GHz
Max: 200 mW
64-QAM,
16-QAM,
QPSK, BPSK
Local Area
Network
OFDM
MMAC HSWA
HiSWANa,
Rec. ITU-R
M.1450
Type of device
Cordless
Telephones
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Infra-Red
<3m
IR
1
Hiper LAN 1,
RLAN
23 Mbits/s
and
1.4 Mbits/s
~100 m
5 GHz
HiperLAN 2,
RLAN
Up to 54
Mbits/s
~50 m
5 GHz1
N/A
Pulse
Point-to-point
up to 200 mW
FSK and
GMSK
Local Area
Network
N/A
ETSI EN 300 652
V1.2.1 (1998-07)
Rec. ITU-R
M.1450
Max1: 200 mW to up
to 1W
16 QAM,
64QAM,
BPSK
QPSK
Local Area
Network
OFDM
ETSI EN 301 893
1
The 5 GHz band consists of several sub-bands (5 150-5 350 MHz, 5 470-5 725 MHz and 5 725-5 875 MHz), which are used in part, or in their
entirety, depending on national or regional arrangements. There may be additional restrictions imposed (e.g. on the power level) depending on the
sub-band used.
* UWB is a candidate technology for IEEE standards 802.x.
________________
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