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

1. 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 Voice:[+1 617 621 7588, E-Mail: zafer@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.

2. Localization via UWB Radios Zafer Sahinoglu, May 11, 2005 Mitsubishi Electric Research Labs

3. 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

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

5. 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

6. 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

7. 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}

8. 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

9. 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

10. Generating an Energy Image Frame interval (M) (M) (2) (2) (1) (M) (1) (1) (2) (N) (1) (2) E(N,M) E(N,1) E(N,2) E(2,M) E(1,M) E(2,1) E(2,2) E(1,1) E(1,2) Energy image

11. frame interval Energy matrix Energy matrix Desired user code-2 {2,1,2,1} Interference code {1,3,1,2} Pulsecompression or Thicker vertical edges Narrower energy windows Energy Image Illustrations

12. 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)

13. 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 FFT Analysis of Energy Image

14. 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 N=1 N = 10 30 30 Frame index Frame index 1 1 50 Energy window index 50 Energy window index 1 1 Energy Image Superposition • When pulse compression with M chips, edges will be only thicker and MN images needed

15. Recommended Edge Analysis Architecture TOA estimate Vertical Edge Detector Energy Vector Energy Matrix Generator FFT Analysis

16. 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

17. Backup Slides