Project: IEEE P802'15 Working Group for Wireless Personal Area Networks WPANs

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• Project IEEE P802.15 Working Group for Wireless
  Personal Area Networks (WPANs)
• Submission Title Edge Detection in dense
  multipath and heavy interference
• Date Submitted 15 May 2005
• Source Zafer Sahinoglu, Mitsubishi Electric
• Contact Zafer Sahinoglu
• Voice1 617 621 7588, E-Mail zafer_at_merl.com
• Abstract This document provides a technical
  recommendation on how the first arriving signal
  energy can be detected in dense multipath and
  heavy SOP interference
• Purpose To point out basic requirements for a
  signal waveform to deal with multipath and SOP
  interference in edge detection
• Notice This document has been prepared to assist
  the IEEE P802.15. It is offered as a basis for
  discussion and is not binding on the contributing
  individual(s) or organization(s). The material in
  this document is subject to change in form and
  content after further study. The contributor(s)
  reserve(s) the right to add, amend or withdraw
  material contained herein.
• Release The contributor acknowledges and accepts
  that this contribution becomes the property of
  IEEE and may be made publicly available by
  P802.15.

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Localization via UWB Radios

• Zafer Sahinoglu,
• May 11, 2005
• Mitsubishi Electric Research Labs

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Generic Architecture for Ranging

• Received signal energy is collected
• Energy vector is processed to suppress noise
  artifacts and enhance signal containing parts
• Edge detection is performed

channel
Signal
Signal Energy Collector
Channel Characteristics
Signal Energy Edge Detector
Signal Energy Conditioner
Signal Parameters
TOA Estimate
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Outline

• Ranging signal waveforms
• SOP Interference
• Deficiencies of coherent energy combining
• A look into signal energy conditioning techniques
• Edge detection for ranging

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Signal Waveforms
optional
One Bit
TH-freedom
Always Empty
Always Empty
Always Empty
M chip times
The Other Bit
optional
TH freedom
Always Empty
Always Empty
Always Empty
Enough long not to cause IFI
M chip times
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SOP Interference

• Without time-hopping, edge information may not be
  recovered under SOP interference

Desired user signal
Interference
Received energy
Deviation from the true the TOA
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Example Acquisition Waveform

• Using the two specified bit waveforms (TH freedom
  0)

Piconet-I
Implicit TH code 1,3,3,1 bits 1,0,0,1
Bit interval
Piconet-II
Implicit TH code 1,1,3,3 - bits 1,1,0,0
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SOP Interference (2)

• Strong SOP interference even with a different
  transmission pattern can be deleterious to
  coherent energy combining
• Example simulation
• CM2 (desired and interferer with different
  channel realizations)
• Energy Window Size 4ns
• EBN0 22dB (both desired and interferer)

desired transmitter
receiver
interferer
True TOA
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How to Filter Out SOP Interference?

• Signal processing of energy samples before
  coherent combining
• Correlation properties of the samples
• Frequency domain analysis (FFT)
• Statistical multiplexing

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Generating an Energy Image
Frame interval
(1)
(2)
(M)
(1)
(2)
(M)
(1)
(2)
(M)
(N)
(1)
(2)
E(N,M)
E(1,M)
E(2,M)
E(N,1)
E(N,2)
E(1,1)
E(1,2)
E(2,1)
E(2,2)
Energy image
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Energy Image Illustrations
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Frame index
Frame index
Energy window index
Energy window index
Interference when received according to time
hopping sequence TH2 (CM2-49)
Desired user when received according to its own
time hoping sequence TH1 (CM2-43)
Frame index
Frame index
Energy window index
Energy window index
Desired user (TH1) Interferer (TH1) when
received according to the time hoping sequence
TH1 (CM2-43 for desired user and CM2-49 for
interferer)
Desired user (TH1) Interferer (TH2) when
received according to the time hoping sequence
TH1(CM2-43 for desired user and CM2-49 for
interferer)
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FFT Analysis of Energy Image

• Desired user energy forms vertical lines in
  multipath channels
• Interference forms a pattern that repeats itself
  along a vertical line
• (Left) energy window size 4ns, TH code length
  4

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Energy Image Superposition

• Simulation settings (single pulse)
• CM2 (Residential NLOS) and no SOP interference
• EBN0 18dB, TF200ns, WE 4ns
• Transmission duration 60µs (for 10 images)
• Vertical edge detection with a Prewitt method
  (see Matlab image toolbox)
• RAM 1.5KB

When pulse compression with M chips, edges will
be only thicker and MN images needed
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Recommended Edge Analysis Architecture
TOA estimate
Vertical Edge Detector
Energy Vector
Energy Matrix Generator
FFT Analysis
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Summary and Conclusion

• Coherent energy combining may not be sufficient
  to accurately detect leading edges
• Energy images provide more insight into
  whereabouts of leading edge even under dense
  multipath and SOP interference
• Signals should be transmitted with a
  distinguishable pattern for the energy detectors
• This can be achieved by
• Coarse block time-hopping
• Pulse compression with very low PRF

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Backup Slides
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