april 25th 2005doc: ieee 15-05-0269-004a zafer sahinoglu, mitsubishi electric slidetg4a1 project:...

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April 25th 2005 Doc: IEEE 15-05-0269-004a

Zafer Sahinoglu, Mitsubishi Electric Slide 1

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) (WPANs)

Submission Title: [Edge Detection in dense multipath and heavy interference]Date Submitted: [15 May 2005]Source: [Zafer Sahinoglu, Mitsubishi Electric]Contact: Zafer SahinogluVoice:[+1 617 621 7588, E-Mail: [email protected]]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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Zafer Sahinoglu,

May 11, 2005Mitsubishi Electric Research Labs

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Signal Parameters

Signal Energy ConditionerChannel

Characteristics

Signal Energy Collector

Signal

TOAEstimate

Signal Energy Edge Detector

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

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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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M chip times

One Bit

The Other Bit

TH-freedom Always EmptyAlways Empty

M chip times

Always EmptyTH freedomAlways Empty

Signal Waveforms

Always Empty

Always Empty

Enough long not to cause IFI

optional

optional

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SOP Interference

Desired user signal

Interference

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

Received energy

Deviation from the true the TOA

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Implicit TH code: {1,3,3,1} – bits: {1,0,0,1}

Implicit TH code: {1,1,3,3} - bits: {1,1,0,0}

Example Acquisition Waveform

Piconet-I

Piconet-II

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

Bit interval

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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)

receiver

desired transmitter

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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(1) (2) (M) (1) (2) (M)

(1) (2) (N)

E(N, TH(N)) E(N, TH(N)+1) … E(N, TH(N)+M)

… … … …

E(2, TH(2)) E(2, TH(2)+1) … E(2, TH(2)+M)

E(1, TH(1)) E(1, TH(1)+1) … E(1, TH(1)+M)

(1) (2) (M)

E(1

,1)

E(1

,2)

E(1

,M)

E(2

,1)

E(2

,2)

E(2

,M)

E(N

,1)

E(N

,2)

E(N

,M)

Frame interval

Generating an Energy Image

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Desired user code-2 {2,1,2,1}

Interference code {1,3,1,2}

Pulse compression

Narrower energy windows

or

Energy matrix Energy matrix

Thicker vertical edges

frame interval

Energy Image Illustrations

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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)

“Desired user (TH1) + Interferer (TH1)” when received according to the time hoping sequence TH1 (CM2-43 for desired user and CM2-49 for interferer)

Fra

me

inde

x

Fra

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inde

x

Energy window index Energy window index

Energy window index

“Desired user (TH1)+ Interferer (TH2)” when received according to the time hoping sequence TH1(CM2-43 for desired user and CM2-49 for interferer)

Fra

me

inde

x

Energy window index

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inde

x

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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, TF=200ns, WE = 4ns– Transmission duration 60µs (for 10 images)– Vertical edge detection with a “Prewitt” method (see Matlab image toolbox)

– RAM: 1.5KB

N

1

Energy window index

Fra

me

inde

x

N=1

1

30

1 50 Energy window index

Fra

me

inde

x

N = 10

30

11 50

When pulse compression with M chips, edges will be only thicker and MN images needed

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Recommended Edge Analysis Architecture

Energy Vector Energy Matrix Generator Vertical Edge Detector

FFT Analysis

TOA estimate

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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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april 25th 2005doc: ieee 15-05-0269-004a zafer sahinoglu, mitsubishi electric slidetg4a1 project:...

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