1. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 1 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [How Energy Detector handles Inter-Pulse Interference?] Date Submitted: [12 May 2005] Source: [Francois Chin, Lei Zhongding, Yuen-Sam Kwok, Xiaoming Peng] Company: [Institute for Infocomm Research, Singapore] Address: [21 Heng Mui Keng Terrace, Singapore 119613] Voice: [65-68745687] FAX: [65-67744990] E-Mail: [chinfrancois@i2r.a-star.edu.sg] Re: [] Abstract: [Presents signaling options to achieve precision ranging with both coherent and non- coherent receivers] Purpose: [To discuss which signal waveform would be the most feasible in terms of performance and implementation trade-offs] 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. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 2 ………………………… 123314567830 Non-inverted pulses are blue, Inverted pulses are green. Pulse Repetition Interval ~ 30ns …………… Ternary Signaling - Synchronisation with Energy Detector …………… Symbol Interval ~940ns Synchronisation / Ranging preamble = Binary Base Sequence repeated For K times….................

3. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 3 How Energy Detector despread? BPF( ) 2 LPF / integrator ADC Sample Rate 1/T c Soft Despread Noncoherent detection of OOK RAKE combiner {1,-1} Binary Sequence Soft output Figure 1. The block diagram of energy detection receiver using soft despreader and RAKE combiner Unipolar M-Seq [+ + + 0 0 0 + + 0 + + + 0 + 0 + 0 0 0 0 + 0 0 + 0 + + 0 0 + + ] Bipolar M-Seq [+ + + - - - + + - + + + - + - + - - - - + - - + - + + - - + + ] Ternary Seq [+ - - 0 0 0 + - 0 + + + 0 + 0 - 0 0 0 0 + 0 0 - 0 - + 0 0 - - ] After Square Law & Integration in PRI

4. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 4 Synchronisation with Energy Detector in AWGN Before Depreader – Unipolar M-Seq [+ + + 0 0 0 + + 0 + + + 0 + 0 + 0 0 0 0 + 0 0 + 0 + + 0 0 + + ] repeated 4x Despread Sequence – Bipolar M-Seq [+ + + - - - + + - + + + - + - + - - - - + - - + - + + - - + + ]

5. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 5 How Energy Detector handle inter- pulse interference? d1d1 d2d2 d3d3 Ternary signaling Non-inverted pulses are blue, Inverted pulses are red. Pulse Repetition Interval ~ 30ns PRI T1T1 T2T2 T3T3 T4T4 T5T5 T6T6 T7T7 T8T8 d4d4 d5d5 d6d6 d7d7 Let ’ s zoom into the channel details PRI T1T1 T2T2 T3T3 T4T4 … … …

6. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 6 Energy Integration in PRI Pulse Repetition Interval 30ns @ TX Ternary codes PRI T1T1 T2T2 T3T3 T4T4 … … … = complex channel samples @ 500MHz Multipath Channel @ RX (assume noiseless case) Received signal matrix (PRI/column) Take the 3 rd PRI as example d1d1 d2d2 d3d3 d4d4 d5d5 d6d6 d7d7

7. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 7 After square-law device at 3 rd PRI (some noise due to cross terms) The soft ADC value for 3 rd PRI: Apply integration over PRI = Column Sum More noise due to cross terms Each PRI contains partial energy from previous pulses Multipath energy spread each PRI Energy Integration in PRI

8. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 8 Energy Detector Sees An Equivalent Unipolar Sequence after integration in PRI d1d1 d2d2 d3d3 Ternary signaling Non-inverted pulses are blue, Inverted pulses are red. Pulse Repetition Interval ~ 30ns After Square Law & Integration in PRI PRI T1T1 T2T2 T3T3 T4T4 e1e1 e3e3 e2e2 + More Noise due to cross terms Sequence become Unipolar d4d4 d5d5 d6d6 d7d7 c1c1 c2c2 c3c3 c4c4 c5c5 c6c6 c7c7 c j =d j 2 integrator Output is a convolution of the equivalent Unipolar Sequence with a PRI-spaced tap-delay-line channel, each tap comprising multipath energy within a correponding PRI

9. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 9 In Multipath Channels … BPF( ) 2 LPF / integrator ADC Sample Rate 1/T c Soft Despread Noncoherent detection of OOK RAKE combiner {1,-1} Binary Sequence Soft output Figure 1. The block diagram of energy detection receiver using soft despreader and RAKE combiner Unipolar M-Seq [+ + + 0 0 0 + + 0 + + + 0 + 0 + 0 0 0 0 + 0 0 + 0 + + 0 0 + + ] Despread Sequence = Bipolar M-Seq [+ + + - - - + + - + + + - + - + - - - - + - - + - + + - - + + ] Ternary Seq [+ - - 0 0 0 + - 0 + + + 0 + 0 – 0 0 0 0 + 0 0 - 0 - + 0 0 - - ] PRI T1T1 T2T2 T3T3 T4T4 e1e1 e3e3 e2e2 T1T1 T2T2 T3T3 T4T4 e1e1 e3e3 e2e2

10. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 10 PRI T1T1 T2T2 T3T3 T4T4 e1e1 e3e3 e2e2 Equivalent to Synchronisation in Multipath Channels Sliding Correlator Output …. Simple RAKE combining at the despreader output (in fact, simple summation across despreader output) can be used to collect energy across PRI

11. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 11 Summary Square Law / Envelope Detector effectively convert a ternary sequence to a Unipolar Sequence Energy integration in PRI converts the multipath channels into a PRI-spaced tap-delay-line channel, each tap comprising multipath energy within a correponding PRI Energy collector / integrator Output is a convolution of the equivalent Unipolar Sequence with the PRI-spaced tap-delay-line channel Simple RAKE combining at the despreader output (in fact, simple summation across despreader output, no need RAKE coefficients) can be used to collect energy across PRI Energy Detector can handle inter-pulse interference just as normal direct sequence spread spectrum systems

12. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 12 Appendix

13. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 13 Ternary – Bipolar – Unipolar Conversion Seq 1+ - - 0 0 0 + - 0 + + + 0 + 0 - 0 0 0 0 + 0 0 - 0 - + 0 0 - - Seq 2- 0 + - - 0 0 0 + 0 + 0 + - 0 + 0 0 0 0 + - 0 0 + 0 0 + - - - Seq 3- + 0 + + - - - 0 + 0 0 0 - 0 0 - 0 + 0 + + 0 0 0 0 - + - 0 0 Seq 40 + 0 + - - 0 - - 0 0 0 - + - + + 0 0 + + 0 - 0 0 + 0 0 0 0 - Seq 5+ - + - 0 0 - 0 0 + + 0 0 0 0 + 0 - - 0 - 0 + 0 0 0 - - + 0 + Seq 60 0 - + - 0 0 0 0 + + 0 + 0 - 0 0 - 0 0 0 + 0 - - - + + 0 + - Seq 1+ + + - - - + + - + + + - + - + - - - - + - - + - + + - - + + Seq 2+ - + + + - - - + - + - + + - + - - - - + + - - + - - + + + + Seq 3+ + - + + + + + - + - - - + - - + - + - + + - - - - + + + - - Seq 4- + - + + + - + + - - - + + + + + - - + + - + - - + - - - - + Seq 5+ + + + - - + - - + + - - - - + - + + - + - + - - - + + + - + Seq 6- - + + + - - - - + + - + - + - - + - - - + - + + + + + - + + This is in fact m- Sequences! Ternary Bipolar Unipolar ± → + 0 → - + → + - → 0 Seq 1+ + + 0 0 0 + + 0 + + + 0 + 0 + 0 0 0 0 + 0 0 + 0 + + 0 0 + + Seq 2+ 0 + + + 0 0 0 + 0 + 0 + + 0 + 0 0 0 0 + + 0 0 + 0 0 + + + + Seq 3+ + 0 + + + + + 0 + 0 0 0 + 0 0 + 0 + 0 + + 0 0 0 0 + + + 0 0 Seq 40 + 0 + + + 0 + + 0 0 0 + + + + + 0 0 + + 0 + 0 0 + 0 0 0 0 + Seq 5+ + + + 0 0 + 0 0 + + 0 0 0 0 + 0 + + 0 + 0 + 0 0 0 + + + 0 + Seq 60 0 + + + 0 0 0 0 + + 0 + 0 + 0 0 + 0 0 0 + 0 + + + + + 0 + +

14. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 14 Properties of M-Sequence Transmit – Unipolar M-Seq [+ + + 0 0 0 + + 0 + + + 0 + 0 + 0 0 0 0 + 0 0 + 0 + + 0 0 + + ] repeated 4x Receive – Bipolar M-Seq [+ + + - - - + + - + + + - + - + - - - - + - - + - + + - - + + ] ZERO autocorrelation

15. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 15 Properties of M-Sequence Transmit – Bipolar M-Seq [+ + + - - - + + - + + + - + - + - - - - + - - + - + + - - + + ] repeated 4x Receive – Unipolar M-Seq [+ + + 0 0 0 + + 0 + + + 0 + 0 + 0 0 0 0 + 0 0 + 0 + + 0 0 + + ] ZERO autocorrelation

16. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 16 Properties of M-Sequence Transmit – Bipolar M-Seq [+ + + - - - + + - + + + - + - + - - - - + - - + - + + - - + + ] repeated 4x Receive – Bipolar M-Seq [+ + + - - - + + - + + + - + - + - - - - + - - + - + + - - + + ] HIGH peak LOW autocorrelation

17. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 17 How to make use of these properties? Transmit signaling UnipolarBipolar Receive signaling BipolarUnipolarBipolar Tx PAR2x1x Corr O/P peka Signal Amp 16 x sqrt(2)1632 Corr O/P noise Pwr 32 σ 2 16 σ 2 32 σ 2 Corr O/P SNR16 / σ 2 32 / σ 2 Despread Gain16 32 Auto-corr00Low ApplicationsEnergy Det - Ranging / Sync / Comm Coherent Det – Ranging Coherent Det - Sync / Comm

18. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 18 Ranging: Code Sequences for different Receiver Receiver TypeRanging Signaling Sequence Receive Sequence CoherentBinaryUnipolar Differential ChipBinaryUnipolar(Differential(Binary)) Energy DetectorTernaryBipolar Criteria/Target – ZERO autocorrelation sidelobes

19. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 19 Communication: Code Sequences for different Receiver Transmit SignalingReceiver TypeReceive Sequence Ternary (Mode 1) CoherentTernary Differential ChipDifferential(Ternary) Energy DetectorBipolar Binary (Mode 2) CoherentBipolar Differential ChipDifferential(Bipolar) Energy DetectorN.A. Criteria/Target – Max SNR and min inter-sequence interference after despreading

20. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 20 Snychronisation: Code Sequences for different Receiver Transmit SignalingReceiver TypeReceive Sequence Ternary (Mode 1) CoherentTernary Differential ChipDifferential(Ternary) Energy DetectorBipolar Binary (Mode 2) CoherentBipolar Differential ChipDifferential(Bipolar) Energy DetectorN.A. Criteria/Target – balance max post-despreading SNR and low auto-correlation sidelobes

21. doc.: IEEE 802.15-05-0257-00-004a Submission May 2005 Francois Chin (I 2 R) Slide 21 Synchronisation Preamble M-sequences has excellent autocorrelation properties Synchronisation / Ranging Preamble is constructed by repeating the base sequence Ternary for Common Signaling e.g. Beacon Packet Ternary for Energy Detector Bipolar for Coherent and Differential Chip Detectors Long preamble for distant nodes is constructed by further symbol repetition