Download User Restrictions Frequency Band for Operation at Part 15

An Introduction to Ultra
Wideband Communication
By Xingpeng Mao
Aug. 2006
Harbin Institute of Technology (Weihai)
References:
1.
J. H. Reed. An Introduction to Ultra
Wideband Communication Systems.
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Contents
 Chapter
1 Introduction
 Chapter 2 Channel Measurement and
Simulation
 Chapter 3 Channel Modeling
 Chapter 4 Antennas
 Chapter 5 Transmitter Design
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Contents (continued)
 Chapter
6 Receiver Design Principles
 Chapter 7 The Coexistence of UWB and NB
Systems
 Chapter 8 Simulation
 Chapter 9 Networking
 Chapter 10 Applications
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Chapter 1 Introduction
1.1 Fundamentals
1.1.1 Overview
 What is UWB? Ultra wideband (UWB) communication
systems can be broadly classified as any
communication system whose instantaneous
bandwidth is many times greater than the minimum
required to deliver particular information.
 Development:
 The first UWB: Marconi Spark Gap Emitter
 All the users efficiently share the common spectral
resource carrier-based communication
 Operate unlicensed UWB systems concurrent with existing
narrowband signals 2002, FCC (Federal Communications
Commission)
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
Difference between UWB and Narrow Band
(NB) systems
1. Large instantaneous bandwidth enable fine time
resolution for network time distribution, precision
location capability, or use as a radar
2. Short duration pulses are able to provide robust
performance in dense multipath environments by
exploiting more resolvable paths.
3. Low power spectral density allows coexistence
with existing users and has a Low Probability of
Intercept (LPI).
4. Data rate may be traded for power spectral
density and multipath performance.
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Large Relative (and Absolute)
Bandwidth
Narrowband (30kHz)
Wideband CDMA (5 MHz)
Part 15 Limit
UWB (Several GHz)
Frequency

UWB is a form of extremely wide spread spectrum where
RF energy is spread over gigahertz of spectrum
 Wider than any narrowband system by orders of magnitude
 Power seen by a narrowband system is a fraction of the total
 UWB signals can be designed to look like imperceptible random
noise to conventional radios
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 FCC
defines UWB as a signal with either a
fractional bandwidth of 20% [2(fH-fL)/(fH+fL)]
of the center frequency or 500MHz(when
the center frequency is above 6GHz).
 Two main problems faced:
How does a particular user recover a particular
data stream?
How do are the users efficiently share the
common spectral resource?
Can a UWB system be built with a sufficient
performance or cost advantage over
conventional approaches to justify the effort and
investment?
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1.1.2 Brief History
 The modern era started in the early 1960s (Harmuth);
 A major breakthrough occurred in 1960s (Tektronix and
Hewlett-Packard, sampling oscilloscope);
 The first ground-penetrating radar commercialized in
1974 (Morey);
 Nomenclature UWB is created around 1989 (the
Department of Defense);
 A multiple access technique for UWB communication
system in 1993(Robert Scholtz, University of Southern
California)
 First FCC certified commercial system was installed in
2003, and the first FCC-compliant commercial UWB
chipset were announced.
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1.1.3 Types of UWB signals
 Impulse UWB (I-UWB)
 No carrier, the transmit signal is a series of base
band pulses.
Fig.1.1 Comparison
of the Bandwidth
of NB and UWB
systems
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Multicarrier UWB (MC-UWB)
 OFDM (Orthogonal Frequency Division Multiplexing)

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survey
 Impulse
UWB (I-UWB)
TH-UWB (Time Hopping)
DS-UWB (Direct-Sequence)
 Multicarrier
UWB (MC-UWB)
OFDM (Orthogonal Frequency Division
Multiplexing)
 PAMPPM
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
Relative Merits of Impulse Versus Multicarrier
 Spread spectrum (SS) can be applied to reduce the
impact of interference on UWB system for both forms of
UWB.
 MC-UWB is well-suited for avoiding interference to or from
NB systems;
 MC-UWB provides more flexibility and scalability.
 Implementing a MC-UWB can be challenging, continuous
variations in power, high-speed FFT processing.
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
Relative Merits of Impulse Versus Multicarrier
(continued)
 I-UWB signals require fast switching times for the transmitter
and receiver and highly precise synchronization.
 High instantaneous power during the brief interval of the
pulse helps to overcome interference but increases the
possibility of interference from UWB to NB systems.
 RF front-end may resemble a digital circuit, problems
associated with mixed-signal integrated circuits.
 Simple I-UWB systems can be very inexpensive to construct.
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FCC UWB Device Classifications

5 classes of devices – Different limits for each:
 Imaging Systems
1. Ground penetrating radars(GPR), wall imaging, medical imaging
2. Thru-wall Imaging & Surveillance Systems
 Communication and Measurement Systems
3. Indoor Systems
4. Outdoor Hand-held Systems
 Vehicular Radar Systems
5. collision avoidance, improved airbag activation, suspension
systems, etc.
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Summary of Preliminary R&O Limits
Application
Frequency Band for
Operation at Part 15 Limits
User
Restrictions
Imaging
3.1 to 10.6 GHz
(GPR <960 MHz)
Yes
Through-wall and
Surveillance
1.99 to 10.6 GHz
Yes
Communications
(indoor & outdoor)*
3.1 to 10.6 GHz
No
Vehicular
24 to 29 GHz
No
*Indoor and outdoor communications devices have different
out-of-band emission limits
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UWB Emission Limit for Indoor Systems
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UWB Emission Limit for Outdoor Hand-held
Systems
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UWB Emission Limits for GPRs, Wall Imaging,
& Medical Imaging Systems
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UWB Emission Limits for Thru-wall Imaging &
Surveillance Systems
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1.2 What makes UWB unique?
 1.2.1
Time domain design
Frequency dependant pulse distortion imparted
by RF components or the wireless channel
Time jitter generated by non-ideal oscillators
 1.2.2
Impact of the antenna
Cover multi-octave bandwidths in order to
transmit pulses on the order of a nanosecond in
duration with minimal distortion
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1.2 What makes UWB unique?
(continued)
 1.2.3
Propagation and channel models
The signal may be overlaid on top of
interference (and SIR<0)
The introduction of large numbers of multipath
signals that were not resolvable in NB system.
 1.2.4
Transmitter and receiver design
The extremely wide bandwidth (BW)
Very high peak-to –average power ratio
Coexistence of UWB and existing NB systems
Most receiver techniques require highly
accurate synchronization with the transmitter
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1.2 What makes UWB unique?
(continued)

1.2.5 Difficulties in using DSP technology
 Very high data rates and ADC (Analog to Digital
Converters) sample rate

1.2.6 Networking issues
 Wireless Personal Area Network (WPAN) (<10m radius):
self-organized, dynamic, ad hoc network
 Network security (low probability of intercept)
 Variable modes of operation (long-range, low data rate
or short-range ,high speed connection)
 Unique challenges for Medium Access Control (MAC)
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1.2 What makes UWB unique?
(continued)
 1.2.7
Future Directions
Potential interference of UWB emissions to
GPS and air traffic control signals.
Help to conserve valuable battery life in sensor
network
 ensure a secure network
Application in the field of medicine
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1.3 I-UWB System Model
1.3.1 overview of the I-UWB system
An unmodulated I-UWB pulse train:

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1.3.2 Pulse Shapes
(Gaussian pulse and its derivatives)
I.
Gaussian pulse

II.
A UWB antenna may differentiate the generated
pulse (assumed to be Gaussian) with respect to
time.
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III.FCC rules
make UWB
transmission
most practical
in the 3.110.6GHz
band.
Gaussian
modulated
sinusoidal
pulse is more
practical.
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1.3.3 Modulation Schemes
I. Pulse Amplitude Modulation (PAM)

II. Pulse Position Modulation (PPM)
Time-Hopping (TH)
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Due to the low power spectral density (PSD),
multiple pulses will be associated with a single
symbol. i.e., the pulse rate is often higher than the
data rate.
 The received signal is modeled as


The channel is modeled as
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
1.3.4 Multiple Access Schemes

1.3.5 Receiver Decision Statistic
In diversity system
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1.4 The MC-UWB System Model

1.4.1 Overview of the MC-UWB System
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
1.4.2 OFDM UWB
 Can have gaps between subcarries
 A proposed physical layer standard for *02.15.3a Wireless Personal
Area Network (WPAN)
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