Wireless Personal Area Networks

Introduction toChirp Spread Spectrum (CSS)Technology : 

November 2003 Lampe, Ianelli, Nanotron Slide 1 Introduction toChirp Spread Spectrum (CSS)Technology presented by Zbigniew Ianelli Nanotron Technologies GmbHBerlin, Germany www.nanotron.com

Contents : 

November 2003 Lampe, Ianelli, Nanotron Slide 2 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

A brief history of Chirp pulses : 

November 2003 Lampe, Ianelli, Nanotron Slide 3 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

Characteristics of Chirp pulses : 

November 2003 Lampe, Ianelli, Nanotron Slide 4 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)

The basic Chirp signal : 

November 2003 Lampe, Ianelli, Nanotron Slide 5 The basic Chirp signal Chirp pulse: Sinc pulse (baseband): Sinc pulse (RF band):

Properties of signal forms in the air and baseband interfaces : 

November 2003 Lampe, Ianelli, Nanotron Slide 6 Properties of signal forms in 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)

Scalable Technology : 

November 2003 Lampe, Ianelli, Nanotron Slide 7 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.

Scalable Technology (continued) : 

November 2003 Lampe, Ianelli, Nanotron Slide 8 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

How to code using CSS : 

November 2003 Lampe, Ianelli, Nanotron Slide 9 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

Key Properties of CSS : 

November 2003 Lampe, Ianelli, Nanotron Slide 10 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.

Mobility Properties of CSS : 

November 2003 Lampe, Ianelli, Nanotron Slide 11 Mobility Properties of CSS Resistance against Doppler effect: The Doppler effect causes a frequency shift of the chirp pulse, which introduces a 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

Coexistence Properties of CSS : 

November 2003 Lampe, Ianelli, Nanotron Slide 12 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

Some Applications and Measurements ofChirp Spread Spectrum (CSS)Technology : 

November 2003 Lampe, Ianelli, Nanotron Slide 13 Some Applications and Measurements ofChirp Spread Spectrum (CSS)Technology presented by John LampeNanotron Technologies GmbHBerlin, Germany www.nanotron.com

New Applications / Global Markets : 

November 2003 Lampe, Ianelli, Nanotron Slide 14 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 New Applications / Global Markets

Enhanced Applications / Markets : 

November 2003 Lampe, Ianelli, Nanotron Slide 15 Applications desiring extended range, such as: Meter Reading Building Automation And other longer-range applications where repeaters are not practical Enhanced Applications / Markets

Evaluation Board : 

November 2003 Lampe, Ianelli, Nanotron Slide 16 Evaluation Board Includes: RF IC SAW filter Optimized balun for asymmetrical antenna operation Crystals

Outdoor testing with CSS : 

November 2003 Lampe, Ianelli, Nanotron Slide 17 Outdoor testing with CSS Test environment: Straße des 17. Juni - Siegessäule

Comparing CSS to DECT Outdoors : 

November 2003 Lampe, Ianelli, Nanotron Slide 18 Comparing CSS to DECT Outdoors

Slide 19: 

November 2003 Lampe, Ianelli, Nanotron Slide 19 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 Indoor testing with CSS

Indoor testing with CSS : 

November 2003 Lampe, Ianelli, Nanotron Slide 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 CSS transmits 1Mbps with Pout = 1 µW over 5m and with 6,3mW over 26m Load-bearing Walls

Outdoor Link-Budget : 

November 2003 Lampe, Ianelli, Nanotron Slide 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

Testing CSS on Hahneberg, Berlin-Spandau : 

November 2003 Lampe, Ianelli, Nanotron Slide 22 Testing CSS on Hahneberg, Berlin-Spandau 4626±10 m 3404±10 m 739±10 m Ref P1 P2 P3 P4 940±10 m

Outdoor testing with CSS : 

November 2003 Lampe, Ianelli, Nanotron Slide 23 Outdoor testing with CSS 4626±10 m Pout = 24 dBm = 250 mW 3404±10 m 739±10 m Pout = 7 dBm = 5 mW Ref P1 P2 P3 P4 940±10 m Pout = 9 dBm = 7.9 mW

Outdoor testing with CSS : 

November 2003 Lampe, Ianelli, Nanotron Slide 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

CSS Outdoor Test Summary : 

November 2003 Lampe, Ianelli, Nanotron Slide 25 Gant = 1 dB Pout = 9 dBm, d = 940 m Pout = 7 dBm, d = 740 m Pout = 26 dBm, d = 6.4 km Pout = 30 dBm, d = 9.8 km CSS Outdoor Test Summary

Need for StandardizationOle PlougR&D ManagerCentral Controls R&DRefrigeration and Air Conditioningwww.danfoss.com : 

November 2003 Lampe, Ianelli, Nanotron Slide 26 Need for StandardizationOle PlougR&D ManagerCentral Controls R&DRefrigeration and Air Conditioningwww.danfoss.com

Summary : 

November 2003 Lampe, Ianelli, Nanotron Slide 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

Conclusions : 

November 2003 Lampe, Ianelli, Nanotron Slide 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