Directional Ultra Wideband (UWB) Channel Characterization

1

forward-looking

• Directional Ultra Wideband (UWB) Channel
  Characterization

By Dr. Ali Hussein Muqaibel
King Fahd University of Petroleum
Minerals Electrical Engineering Department 1st
CIT research Open Day 30-Mar-08
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Topics

• Definition
• Advantageous
• CRITICALITIES
• Applications
• Prototypes
• Modulation
• Multiple Access UWB Communication
• UWB Coexistence Issues
• Channel Measurements
• Channel Modelling (Temporal / Directional)
• Research Areas in UWB Communication
• Research groups Companies

UWB is an old technology with the potential
to significantly impact the traditional way of
managing the spectrum
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What is UWB ?

• An UWB transmitter is defined as an intentional
  radiator that, at any point in time, has a
  fractional bandwidth of greater than or equal to
  0.2 or occupy a bandwidth greater than 500 MHz
  regardless of the fractional bandwidth FCC.
• Generally exhibits a transient impulse response.
• Impulse Radio-UWB Communication uses fairly short
  (sub-nano) pulses instead of continuous waves to
  transmit information.
• OFDM-UWB.

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Channel Capacity of UWB

• Shannons Channel Capacity Theorem

Computed Bandwidths
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Historical Perspective on Ultra-Wideband (UWB)

• Todays Environment
• Scarcity of available spectrum for new
  applications
• Proliferation of digital consumer electronics
  devices
• Advances in microprocessor power
• Numerous improvements in process technology (such
  as SiGe, CMOS and GaAs)

• UWB Revolution
• By 2000 Large companies had applied UWB to
  networking applications
• UWB meets requirements for high throughput
  applications
• Recycles scarce spectrum

• History
• lt1900 Hertz generated pulsed spark discharge
• In 1940s used for radar
• In 1970s matured as solution for covert military
  communications
• In 1990s developed for location and positioning
  applications

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Promised! UWB System Advantages

• New technology considerable development
  potential.
• Nearly "all-digital", with minimal RF
  electronics.
• An LPD signature produces minimal interference
  to proximity systems , minimal RF health hazards
  and is hardly interceptible.
• Extremely high data rate performance in
  multi-user network applications.
• Can provide very fine range resolution and
  precision distance and/or positioning measurement
  capabilities.
• Relativity immune to multipath cancellation
  effects as observed in mobile and in-building
  environments.
• Low Power Consumption

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UWB CRITICALITIES

• Coexistence (FCC)
• Multi-user capability
• Real world performance
• Implementation complexity
• Cost and competitiveness
• Connectivity with narrowband systems

Do many UWB devices operating within a small area
cause serious interference to existing licensed
services ?
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Some UWB Applications

• Wireless USB
• Digital Video Networks
• Short range radios
• High Speed (tens Mb/s) WLANs, microphones, etc.
• Precision Geo-location Systems
• Industrial RF Monitoring Systems
• Collision Avoidance Sensors
• Motion and Intrusion Detection Radar
• Automobile and aircraft proximity radar,
  including precision automatic landing
• Subsurface in-ground penetration radar

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Networking

• Personal Area Networking (PAN), connecting cell
  phones, laptops, PDAs, cameras, MP3 players.
• Much higher data rates than Bluetooth or 802.11.
• Can be integrated into automotive in-car services
  and entertainment.
• Download driving directions from PDA/laptop for
  use by on-board navigation system using GPS.
• Download audio and videos for passenger.

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UWB Radar

• Radar signal changes as it travels and is
  reflected and absorbed (causing additions,
  subtractions, differentiations and integrations).
• Conventional Radar uses sinusoidal and
  quasi-sinusoidal signals
• These changes cause amplitude and time shift
• UWB radar uses pulses
• These changes cause amplitude and time shifts
  but also change in the shape of the waveform
• Many possible levels of complexity depending on
  the application.
• More information can be extracted with more
  complex processing.

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Vehicular Short Range Radar (SRR)

• UWB radar allows detection of moving targets
  without using Doppler effect.
• Ability to measure both stationary and moving
  objects on and nearby the road.
• Calculation of the cartesian position of the
  objects requires a high ranging accuracy as well
  as target separation capability necessitating
  large bandwidth.
• Different materials and environments distort of
  pulses differently. This information could be
  used for better object identification. (Need for
  accurate channel models).
• Reduce post detection signal processing, esp. for
  some radar applications that require fast Fourier
  and inverse fast Fourier transforms, because of
  the time resolution of the UWB system.

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Information Services

• Info-station concept
• Road side markers containing UWB transmitters.
• Short burst of very high rate data (100s of Mbps
  for 1-3 sec at a time)
• Messages could contain road conditions,
  construction, weather advisories.
• Allow for emergency assistance communication.

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Information Services

• Info-station concept
• Service station
• While, pumping gas, latest video or other content
  could purchased for download and viewing later at
  home or by passengers in the vehicle.

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Vehicular Radar

• Collision Avoidance/Detection
• Driver aid/alert to avoid collisions.
• Aid for airbag/restraint deployment
• Resolution to distinguish cars/people/animals on
  or near road

Image from presentation by Prof. Dr. Knoll of
SARA at 2nd Workshop on introduction of Ultra
Wideband Services in Europe
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Collision Avoidance Example

• 600 MHz instantaneous BW
• High-speed, dual tunnel detector
• Range
• 1 - 50 feet against human target
• 1 - 200 feet against pickup truck
• Clutter resistant
• Extremely low false alarm rate

Reference Fontana, R. Ultra Wideband Technology
- The Wave of the Future? ITC/USA 2000, Oct.
2000.
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Vehicular Radar

• Road Conditions Sensing
• UWB radar has the resolution to sense road
  conditions (i.e. dips, bumps, gravel vs.
  pavement).
• Information to dynamically adjust suspension,
  braking, and other drive systems.

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Communication Prototypes

• Time Domain has built several prototypes
  including the following
• A full duplex 1.3 GHz system with an average
  output power of 250 microWatts, and a variable
  data rate of either 39 kbps or 156 kbps.  The
  radio has been tested to beyond 16 kilometers (10
  miles).
• A full duplex 1.7 GHz walkie-talkie with an
  average output power of 2 milliWatts, a data rate
  of 32 kbps and a range of 900 meters.   The unit
  was also capable of measuring the distance
  between radios with an accuracy of 3 cm (0.1 ft).
  
• A simplex 2.0 GHz data link with an effective
  average output power of 50 microWatts, a data
  rate of 5 Mbps at bit error rate (BER) of 0 with
  no forward error correction (FEC) and a range of
  10 meters (32 ft) through two walls inside an
  office building.

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UWB Products, Location

• Aether Wire Locations (AWL)
• Development of pager-sized units that are capable
  of localization to submeter accuracy over
  100-meter distances in networks of up to a few
  hundred localizers.
• A prototype localizer consists of two chips
• Actual size TX (Driver2) RX
  (Aether5)
• with Dime

Reference http//www.aetherwire.com/
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Trinity Chip Set

• Xtreme Spectrum Inc. has released Trinity chip
  set.
• Data rates of 25, 50, 75 and 100 Mbps.
• MAC, baseband processor, RF transceiver, LNA, and
  antenna
• Streaming video applications.
• Wireless Fast Ethernet, USB2, and 1394.

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PulsON ASICs

• Time Domain Corporation is marketing PulsON
  family of UWB silicon products.
• Indoor wireless networking, 100's Mbps
• Indoor personnel and asset tracking systems.
• Precision measurement systems for surveying and
  measurement.
• Radar, 20 cm accuracy
• Through wall sensing.
• Industrial sensing for robotic controls.
• Automotive sensing for collision avoidance.
• Security bubbles for home and industrial security
  systems.

Image from Kelley, D., Reinhardt, S., Stanley,
R., Einhorn, M. PulsON Second Generation Timing
Chip Enabling UWB Through Precise Timing, Proc.
of the IEEE Conference on Ultra Wideband Systems
and Technology 2002.
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UWB Products, Communications

• MultiSpectral Solutions Inc.
• Communications, Mobile ad hoc Network (MANET)
• 128 kbps voice, 115.2 kbps data or 1.544 Mbps
  (T1)
• Range 1-2 km (node-to-node) with omni antennas

Reference Fontana, R. Ultra Wideband Technology
- The Wave of the Future? ITC/USA 2000, Oct.
2000.
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UWB Products, Location

• MultiSpectral Solutions Inc.
• High resolution, geolocation system, 3-D
  positioning
• Sub-foot resolution
• Range
• Up to 2 km outdoors
• Up to 100 meters indoors
• UWB Geopositioning Example

Reference Fontana, R. Ultra Wideband Technology
- The Wave of the Future? ITC/USA 2000, Oct.
2000.
Reference Fontana, R. Ultra Wideband Technology
- The Wave of the Future? ITC/USA 2000, Oct.
2000.
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Received Signal

• Multiple Access, when the physical layer is UWB,
  is achieved by using time hopping codes
• When the number of users is Nu , the received
  signal is

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Pulse Position Modulation
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Gaussian, Monocycle and Doublet Waveforms

• 2GHz (gt1Mhz) , noise like.
• fc typically 650 MHz 5MHz.
• Tightly controlled pulse-to-pulse interval.
• Pulse width 0.2 1.5 nanoseconds.
• Pulse-to-Pulse interval 100-1000 nano-seconds.

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Co-existence Issue Reply Comments

• Wide agreement that this technology is very
  promising, there is a very broad applications
  range
• Strong concern to allow the UWB devices operate
  below 2 GHz or even below 3 GHz.
• they should be licensed !
• This technology should not use (re-use the paid
  spectrum by others) the spectrum for free !
• This technology is still immature and we dont
  know what the interference problems may rise
• Extend the period of time to complete the
  interference tests
• Worldwide regulation

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Regulatory Issues

• FCC has released First Report and Order (RO)
  permitting the manufacture of UWB devices (April
  22, 2002).
• Defined 3 types of UWB devices
• Imaging Systems.
• Communications and Measurement Systems.
• Vehicular Radar.
• Below 960 MHz, all types must meet FCC 15.209
  limits.

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FCC Mask for Vehicular Radar

• Must have a center frequency greater than 24.075
  GHz.
• Requires use of a directional antennas or other
  method that will attenuate the emissions 38
  degrees or higher above the horizontal plane in
  the 23.6-24.0 GHz band by additional 25 dB
• High enough in frequency to permit the use of an
  antenna small enough to be mounted on an
  automobile. -FCC RO

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FCC Mask for Comm/Meas

• Transmit only will operating with a receiver.
• Indoor
• Must show that they will not operate when taken
  outside (ex require AC power).
• Handheld (outdoor)
• Operate in a peer-to-peer mode without location
  restriction.

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FCC Mask for Imaging (Low Freq)

• GPR, wall imaging, through wall imaging.
• -10 dB bandwidth below 960 MHz
• Use restricted to those licensed under Part 90
  rules and complete a coordination procedure with
  the Government.

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FCC Mask for Imaging (Mid Freq)

• Through-wall and surveillance systems
• -10 dB bandwidth between 1.99 and 10.6 GHz
• Use restricted to those licensed under Part 90
  rules and complete a coordination procedure with
  the Government.

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FCC Mask for Imaging (High Freq)

• GPRs, wall, and medical imaging devices
• -10 dB bandwidth between 3.1 and 10.6 GHz
• Must complete a coordination procedure with the
  Government.

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Channel Measurement

• Propagation for communications and radar system.
• Interference to narrowband communications and
  other electronics.
• Resistance of UWB to interference.
• Must understand channel effects to fully exploit
  the unique properties of UWB.
• Affects communications waveform/modulation/receive
  r design.
• Material/shape/range of objects affect radar
  signature.

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Measurement Metrics

• Path loss
• Impact of environment
• Impact of signal type/frequency band
• Multipath characteristics
• Number of multipath components
• Multipath amplitude distribution
• Multipath Delay distribution
• Spatial variation (fading)
• Spectral Characteristics
• Impact of modulation, center frequency, distance
• Material penetration/attenuation measurements
• Drywall, concrete, windows, office partitions,
  etc.
• Angle (Direction of Arrival)

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Channel Measurement Environments

• Indoor
• Within a room (LOS, NLOS), Between rooms/floors,
  Down hallways
• Will investigate the impact of
• distance
• Rx/Tx Antenna Height
• antenna polarization
• Indoor-to-outdoor
• Outdoor
• Campus environment
• Rural, Hilly, Impact of foliage
• Urban
• Low altitude
• Impact of distance (up to 1km)
• Mobility (Pedestrian, Vehicular)
• In Vehicle
• Automotive, airliner

Ex Indoor Measurements
Ex Outdoor Measurements
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Time Domain (TD) Measurement Setup
Tektronics 11801/HP 54120A Digitizing
Oscilloscope
Running LabView 6.0i
LN Amplifiers
Data Acquisition Unit
trigger input
Balun and wideband transmitting antenna
Balun and wideband receiving antenna
pretrigger
trigger
Pulse Generator Pico-second Pulse Labs model
4050A/4100
Step Generator Driver
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Bandpass Pulse Sounder
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Frequency Domain (FD) Measurement Setup
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Directional UWB Simulator

• Includes the Transfer Function of the Transmit
  antenna the receive antenna.
• Utilize IEEE802.15 model (temporal)

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Antennas and Radiated Measurements
Antenna1 TEM Horn
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Multipath Angle and Pulse Shape

• Sources and Antennas Characterization
• Compare and test the measurement setups
• Maximum and average power measurements and
  dynamic range.
• Evaluate the ringing and mismatch.
• Understand the effect of the antenna on the
  radiated pulse shape.
• Characterization bandwidth.
• The effect of the angle of transmission and angle
  of arrival on the captured pulse shape.

H-Scan (Azimuth Angle)
E-Scan (Elevation Angle)
(c)
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Acquired Signals

• The transmitted signal could get differentiated
  before it is decoded
• Multiple reflection cannot be avoided

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Measurements in Hand (or through web)
Photo for location 4C with cubical partitions
Hallways in Durham Hall, location 2B
Blueprint for the fourth floor of Durham Hall
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Multipath Scenarios
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Models

• System models
• path loss estimation
• appropriate for link budget analysis and
  interference prediction
• perhaps similar to Hata model for cellular
• Receiver models
• multipath statistical characterization
• appropriate for receiver design
• perhaps similar to Hashemi model or
  Saleh/Valenzuela model for wideband indoor

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Path Loss Model

• The commonly used Friis transmission formula may
  give misleading or incorrect results when applied
  to UWB systems.
• Friis, or "path loss," formulas predict that the
  received signal power will decrease with the
  square of increasing frequency.
• UWB signals span a very large bandwidth such that
  change in received power over the bandwidth
  cannot be ignored as in narrowband systems.
• This will distort the frequency spectrum of UWB
  pulses and thus distort the pulse shape.

Reference Sweeney, D. Towards a Link Budget for
Ultra Wideband (UWB) Systems. Presented to VT
UWB Working Group, June 2002.
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Different Measurements
Source 1
Source 2
Network Analyzer (ifft)
Antenna 1
Antenna 2
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Marital Pictures (Bricks, Blocks, Styrofoam)
w 8.53542 cml 19.8 cm h 5.82676 cma
3.5179 cm b 4.15036 cmd1 1.905 cm d2 2.159
cm
a 12.2 cm b 12.5 cm c 4.8 cm d 3.7 cm e
3.2 cm
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More Materials
Sample Door
Structure Wood
Wall-board
PlyWood
Office Partition
TDL Reinforced Concrete Pillar
Glass
Whittemore 3rd floor Reinforced Concrete Pillar
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Transient Insight
Bricks wall

• Applicability of matched filter receiver
  (LOS/NLOS).
• Effect of multiple reflections inside the wall.
• Extended time-domain response.

Blocks wall
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• Model Deconvolution
• The impulse response of the NB propagation
  channel is often modeled as
• Does not fit the UWB channel because the delta
  function at the receiver implies a wide channel
  bandwidth relative to the bandwidth of the
  excitation pulse.
• Deconvolution is need!

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Subtractive Deconvolution
(a) Received profile, (b)reconstructed with
zero-insertion, (c) reconstructed with
subtractive deconvolution
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Energy capture

• Goal "best" values for the amplitude, delay and
  template shape (angles) such that the synthesized
  waveform is well matched to the received
  waveform. Energy capture, EC,

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Energy capture using zero-insertion and
subtractive deconvolution
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Energy capture for different number of reference
templates
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Extracted angle distribution for LOS and NLOS
scenarios
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Current Conclusions on Directional UWB
Characterization
The captured energy increases by more than 10
when using five directional correlators rather
than one. The use of subtractive deconvolution
rather than zero-insertion used by previous
authors allowed for resolving overlapping
components and increased the captured energy.
Further extension of the work would include
optimizing the choices of reference templates
based on extensive antenna measurements.
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Areas in UWB Research Communication
Measurements

• Interference Measurements
• Antenna Design
• Spread Spectrum Techniques
• Multiple Access Techniques
• Multi-user detection
• Time Hopping Codes
• System Performance Evaluation under different
  channel conditions (Gaussian, Raleigh)
• Coding and Diversity Applications
• Pulse Shaping and Modulation

Models
Signal Processing Receiver Design
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Working Towards UWB Wireless Communication
Dr. Ali Hussein Muqaibel muqaibel_at_kfupm.edu.sa Kin
g Fahd University of Petroleum
Minerals Electrical Engineering Department
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Research Groups

• Ultra Wideband Working Group (UWBWG) www.uwb.org
• Ultra Lab Web ultra.usc.edu/ulab/
• University of Texas, Center of Ultra Wideband
  Research and Engineering sgl.arlut.utexas.edu/asd/
  Cure/impulse.html
• Time Domain Laboratory (VT) tdl.ece.vt.edu
• Time Domain www.time-domain.com
• Bibliography Of Ultra-wideband Technology
  www.aetherwire.com/CDROM/General/biblio.html
• Presentations from the 1st European Ultra
  Wideband Workshop www.cordis.lu/ist/ka4/mobile/uwb
  _workshop.htm
• Ultra Wideband (UWB) Frequently Asked Questions
  (FAQ) www.multispectral.com/UWBFAQ.html