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: Introduction to Chirp Spread Spectrum (CSS) Technology Date Submitted: November 11, 2003 Source: John Lampe, Zbigniew Ianelli Company: Nanotron Technologies Address: Alt-Moabit 61, 10555 Berlin, Germany Voice: +49 30 399 954 135, FAX: +49 30 399 954 188, E-Mail: j.lampe@nanotron.com Re: Discussion of interesting RF technology Abstract: Tutorial Presentation on CSS for IEEE 802 – part 1 Purpose:November Plenary Tutorial #4. 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. Lampe, Ianelli, Nanotron

2. Introduction toChirp Spread Spectrum (CSS)Technology presented by Zbigniew IanelliNanotron Technologies GmbHBerlin, Germany www.nanotron.com Lampe, Ianelli, Nanotron

3. Contents • A brief history of Chirp pulses • Characteristics of Chirp pulses • The basic Chirp signal • Properties of signal forms • Scalable technology • How to code using CSS • Key Properties of CSS Lampe, Ianelli, Nanotron

4. A brief history of Chirp pulses • Used by whales and dolphins • Patent for radar applications in 1944 by Prof. Hoffmann • Further developed by Sidney Darlington (Lifetime IEEE Fellow) in 1947 („Pulse Compression Radar“) • Patented by Canon for data transmission in fiber optic systems • Chirp Spread Spectrum for commercial wireless data transmission is investigated since 1997 Lampe, Ianelli, Nanotron

5. S(f) f B Spectrum of the chirp pulse with bandwidth B and a roll-off factor of 0.25 Characteristics of Chirp pulses • A chirp pulse is a frequency modulated pulse. • Its duration is T; within this time the frequency is changing in a monotonic manner from a lower value to a higher one („Up-Chirp“) or reverse („Down-Chirp“). • The difference between these two frequencies is a good approximation for the bandwidth B of the chirp pulse. Up-Chirp in the time domain (roll-off factor 0.25) Lampe, Ianelli, Nanotron

6. The basic Chirp signal Chirp pulse: Sinc pulse (baseband): Sinc pulse (RF band): Lampe, Ianelli, Nanotron

7. Properties of signal formsin the air and baseband interfaces • Chirp pulses for the RF channel: • High robustness (BT>>1) • Wideband signal • Constant envelope of the RF waveform • Constant, uniform PSD (Power Spectral Density) • well controlled spectrum in very simple way • Sinc pulses in the baseband: • High speed (Bδ=1) • Easy signal processing (threshold detector) Lampe, Ianelli, Nanotron

8. Scalable Technology Frequency spreading: Basic information theory tells us that CSS benefits when the bandwidth B of the Chirp pulse is much higher than thedata rate R: B >> R Time spreading: The data rate can scale independently of the BT product. The duration T of the Chirp pulse can be chosen freely. A signal with avery high BT product can be achieved, which transforms into a very robust signal in the channel. Lampe, Ianelli, Nanotron

9. Scalable Technology (continued) Excellent range – data rate scalability: Preferred for system where range and/or data rate requirement varies rapidly. Especially promising for wideband or ultra wideband system where available frequency bandwidth B is much higher than the data rate R Lampe, Ianelli, Nanotron

10. f 1 0 1 0 0 1 fHI fLO t OOK with Null and Up-Chirp Chirp pulse How to code using CSS Modulation techniques: On-Off-Keying (OOK), for example: Up-Chirp = „1“; Null = „0“ allows 2 independent coexisting networks Superposed Chirps (4 possible states): Null/Up-Chirp/Down-Chirp/ Superposition of Up- and Down-Chirp allows one network with double the data rate Lampe, Ianelli, Nanotron

11. Key Properties of CSS • High robustness: • Due to the high BT product, chirp pulses are very resistant against disturbances. • Multipath resistant: • Due to the broadband chirp pulse, CSS is very immune against • multipath fading; CSS can even take advantage of RF echoes. • Low power consumption: • CSS allows the designer to choose an analog implementation, • which often consumes much less power. • Low latency: • CSS needs no synchronization; a wireless connection can beestablished very quickly. Lampe, Ianelli, Nanotron

12. Mobility Properties of CSS Resistance against Doppler effect: The Doppler effect causes a frequency shift of the chirp pulse, which introducesa negligible shift of the baseband signal on the time axis. • Example: • Bandwidth of the chirp 80 MHz • Duration of the chirp 1 µs • Center frequency of the chirp (ISM band) 2.442 GHz • Relative speed between transmitter and receiver 2000 km/h • Frequency shift due to Doppler effect 4.52 kHz • Equivalent shift of the message on the time axis 56.5 ps • Note: • 2000 km/h is equivalent to 1243 miles/hour Lampe, Ianelli, Nanotron

13. Coexistence Properties of CSS Immune to in-band interferer: Scalable processing gain (determined by BT product of the chirp) enables selection of appropriate immunity level against in-band interferences. • Example: • Bandwidth B of the chirp 64 MHz • Duration time T of the chirp 1 µs • Center frequency of the chirp (ISM band) 2.442 GHz • Processing gain, BT product of the chirp 18 dB • Eb/N0 at detector input (BER=0.001) 14 dB • In-band carrier to interferer ratio (C/I @ BER=0.001) -4 dB Lampe, Ianelli, Nanotron

14. Some Applications and Measurements ofChirp Spread Spectrum (CSS)Technology presented by John LampeNanotron Technologies GmbHBerlin, Germany www.nanotron.com Lampe, Ianelli, Nanotron

15. New Applications / Global Markets • Applications requiring mobility faster than 11 mph, such as: • Tire pressure • Assets in vehicles (in-car communications) • Drive-by • Drop boxes • Drive-by AMR • Toll booths • Applications requiring robustness or fewer retransmissions in multipath environments, such as: • Industrial mission-critical • Airplanes • Ships / engine rooms • Gaming • New WINA alliance one example of this need • Applications requiring ranging accuracy better than 0.5 meters, such as: • Asset tracking (active RFID) • Personnel tracking • Motion detection • Automatic network installation Lampe, Ianelli, Nanotron

16. Enhanced Applications / Markets • Applications desiring extended range, such as: • Meter Reading • Building Automation • And other longer-range applications where repeaters are not practical Lampe, Ianelli, Nanotron

17. Evaluation Board Includes: • RF IC • SAW filter • Optimized balun for asymmetrical antenna operation • Crystals Lampe, Ianelli, Nanotron

18. Comparing CSS to DECT Outdoors Lampe, Ianelli, Nanotron

19. Indoor testing with CSS d=23 m, Pout = -15 dBm = 32 µW, G=1,5 dB, BER = 10-3 d=15 m, Pout = -15 dBm = 32 µW, G=1,5 dB, BER = 10-3 Result: d = 23 m with Pout = -15 dBm Calculated: d = 50 m with Pout = +10 dBm, a= 3 Lampe, Ianelli, Nanotron

20. Indoor testing with CSS d=5 m, Pout = -30 dBm= 1 µW, G = 1,5 dB, BER = 10-4 d=26 m, Pout = 8 dBm = 6,3 mW, G = 1,5 dB, BER = 10-3 Load-bearing Walls CSS transmits 1Mbps with Pout = 1 µW over 5m and with 6,3mW over 26m Lampe, Ianelli, Nanotron

21. Outdoor Link-Budget • Link budget without cable losses or antenna-gain, best case: LBbest = 103 dB • Outdoor free space propagation: distance ~ link-budget with  = 2.1 … 2.3 • But: Outdoor propagation is not always free space propagation, due to e.g. hills, trees, houses, … • Therefore: Measurements have to be done! d = 940 m Lampe, Ianelli, Nanotron

22. Testing CSS on Hahneberg, Berlin-Spandau P2 P3 3404±10 m P1 739±10 m 4626±10 m P4 940±10 m Ref Lampe, Ianelli, Nanotron

23. Outdoor testing with CSS P2 3404±10 m P3 P1 739±10 m Pout = 7 dBm = 5 mW 4626±10 m Pout = 24 dBm = 250 mW P4 Ref 940±10 m Pout = 9 dBm = 7.9 mW Lampe, Ianelli, Nanotron

24. Outdoor testing with CSS • Measurement Challenge: Teufelsberg • 6483 m distance • 7.7 dBm output power • 18 dB antenna gain • No FEC • BER 10E-3 Lampe, Ianelli, Nanotron

25. CSS Outdoor Test Summary Pout = 30 dBm, d = 9.8 km Pout = 26 dBm, d = 6.4 km Pout = 7 dBm, d = 740 m Pout = 9 dBm, d = 940 m Gant = 1 dB Lampe, Ianelli, Nanotron

26. Need for StandardizationOle PlougR&D ManagerCentral Controls R&DRefrigeration and Air Conditioningwww.danfoss.com Lampe, Ianelli, Nanotron

27. Summary • Introduced CSS technology • Explained behavior and benefits • Suggested some additional applications that can be satisfied • Shown test results that demonstrate some of CSS’ capabilities • Shown one customer’s application requirements Lampe, Ianelli, Nanotron

28. Conclusions • CSS has qualities of both spread spectrum and UWB. • CSS enhances robustness and range • CSS adds mobility • CSS can be implemented with today’s technologies • CSS is a global solution Lampe, Ianelli, Nanotron