Non-coherent Ranging Signal Waveforms Overview

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Ranging Signal Waveforms: Non-coherent Ranging Proposals (Overview) Date Submitted: [13 June, 2005] Source: [Zafer Sahinoglu] Company [Mitsubishi Electric.] Address [201 Broadway, Cambridge, MA 02139] Voice617 621-7588], FAX: [617 621-7549], E-Mail: [zafer@merl.com] Re: [802.15.4a.] Abstract: [Overview of ranging receiver architectures for non-coherent reception] Purpose: [To promote discussion in 802.15.4a.] 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. Outline • Signal Waveforms • Receiver Architecture • Comparison of Proposals • Issues in Non-coherent ranging • Suggestions

3. Signal Waveforms • There are 4 waveforms under consideration • Bulk PPM • IR-TR (Impulse Radio Transmitted Reference) • MTOK sequences • TH-IR (Time Hopping Impulse Radio)

4. Option-I One Bit Always Empty Always Empty Always Empty 100ns 8-chip times: 150ns 100ns 8-chip times: 150ns The Other Bit Always Empty Always Empty Always Empty 100ns 8-chip times: 150ns Enough long not to cause IFI : 100ns 8-chip times: 150ns

5. Ts = 500ns Option-II « 11 » 2-PPM + TR base M = 2 One bit/symbol « 01 » « 10 » « 00 » (coherent decoding possible)

6. To compare fairly, with option-I, which has 8 pulses in 500ns, the PRI for option-III is 62.5ns Option-III Ternary Signaling for Synchronization & Ranging • -Common signaling (Mode 1) for ALL Detectors • -Receiver-specific signaling (Mode 2) for ED Pulse Repetition Interval ~ 62.5ns 1 2 3 4 5 6 7 8 30 31 ………………………… Non-inverted pulses are blue, Inverted pulses are green. Synchronisation / Ranging preamble = Binary Base Sequence repeated For K times… …………… …………… ................. Symbol Interval =1937.5ns Symbol Interval =1937.5ns

7. Option-IV • Illustration: • Use of an 8-ary Time Hopping code of length 4 • Use of such a TH code combined with the band plan may allow to handle the SOP issue • Code order and length are scalable to meet different requirements • Tp = 4ns, Tc = 20 ns, Tf = 160 ns, Tsymbol = 640 ns PRP ± TH Tp Tc Tf

8. Recommended Architecture for Ranging with Non-Coherent Rx (MERL) • (No FFT routine is needed, being different from doc#0269) Energy image generation Removes interference 2-4ns Length-3 Vertical Median or Minimum Filtering 1D to 2D Conversion LPF / integrator BPF ( )2 ADC 2D to 1D Conversion with Energy Combining TOA Estimator

9. Recommended Architecture for Ranging with Non-Coherent Rx (I2R) TOA Estimator Energy image generation & interference suppression 2D-1D conver-sion interference suppression 2-4ns Energy combining across symbols 1D-2D conversion Sliding Correlator LPF / integrator BPF ( )2 ADC Bipolar Template

10. Recommended Architecture for Ranging with Non-Coherent Rx (FT R&D) Time base 1-2ns accurate 4ns Time-stamping "Path-arrival dates" table Analog Comparator LPF / integrator BPF ( )2 1D to 2D Conversion Filtering + Assumption/path selection Assumption path synchronization Matrix TOA measure

11. RF Part Signal LNA BPF ADC Analog comparator Commonalities • Signal energy collection architecture is the same • Sampling resolution is the same (e.g., 2ns-4ns) • 1D to 2D conversion for interference removal seems to be adopted in all the architectures Energy image generation TOA Estimator Interference removal 2D to 1D Conversion 1D to 2D Conversion

12. Post Filtering Energy Matrix Generator-I 2D-1D conversion TOA Est. Ranging Architecture Comparison • MERL architecture works with all signal waveforms • Its performance would be • Very high in Option-4 (FT) • High in Option-1 (MERL, TDC) • Moderate in Option-3 (I2R) • I2R and MERL receiver architectures have good support for scalability in TDOA applications (unsure about FT) • Receive from TDOA stations simultaneously, without changing the RF front • Decode TOA from each station at the post filtering Post Filtering Energy Matrix Generator-M 2D-1D conversion TOA Est.

13. Feature Comparison

14. Issues in Non-coherent ranging • Square-law operation is non-linear • Relative improvement in SNR by statistical multiplexing is higher, when pulse amplitudes are higher • Option-1 requires longer preamble than option-4 to achieve the same SNR level • Error floor can be lowered for the same SNR level, by having narrower integration intervals - Preamble length For a given sampling resolution Mean absolute ranging error Higher sampling resolution + EbN0 25dB

15. Suggestions • Test the ranging performance of the three proposals at a sufficiently high SNR without SOP • To see the best achievable ranging accuracy with 90% confidence level • To derive the required preamble length • Test the ranging performance of the three proposals at the 90% level SNR from step-1 with SOP (SIR=0dB, 10dB) • Quantify the degradation in ranging accuracy and confidence level