CSS Tutorial

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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 [phone], E-Mail
j.lampe_at_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.
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Introduction toChirp Spread Spectrum
(CSS)Technology

• presented by
• Zbigniew Ianelli Nanotron Technologies
  GmbHBerlin, Germany
• www.nanotron.com

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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

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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

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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)
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The basic Chirp signal
Chirp pulse
Sinc pulse (baseband)
Sinc pulse (RF band)
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Properties of signal forms in the air and
baseband interfaces

• Chirp pulses for the RF channel
• High robustness (BTgtgt1)
• 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 (Bd1)
• Easy signal processing (threshold detector)

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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 gtgt 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.
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Scalable Technology (continued)
Excellent range data rate scalability Preferre
d 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
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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-Ch
irp/ Superposition of Up- and Down-Chirp allows
one network with double the data rate
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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.
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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
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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 (BER0.001) 14 dB
In-band carrier to interferer ratio (C/I _at_
BER0.001) -4 dB
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Some Applications and Measurements ofChirp
Spread Spectrum (CSS)Technology

• presented by
• John LampeNanotron Technologies GmbHBerlin,
  Germany
• www.nanotron.com

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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

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Enhanced Applications / Markets

• Applications desiring extended range, such as
• Meter Reading
• Building Automation
• And other longer-range applications where
  repeaters are not practical

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Evaluation Board

• Includes
• RF IC
• SAW filter
• Optimized balun for asymmetrical antenna
  operation
• Crystals

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Outdoor testing with CSS
Test environment
Straße des 17. Juni - Siegessäule
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Comparing CSS to DECT Outdoors
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Indoor testing with CSS
d23 m, Pout -15 dBm 32 µW, G1,5 dB, BER
10-3
d15 m, Pout -15 dBm 32 µW, G1,5 dB, BER
10-3
Result d 23 m with Pout -15
dBm Calculated d 50 m with Pout 10 dBm, a
3
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Indoor testing with CSS
d5 m, Pout -30 dBm 1 µW, G 1,5 dB, BER
10-4
d26 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
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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
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Testing CSS on Hahneberg, Berlin-Spandau
P2
P3
340410 m
P1
73910 m
462610 m
P4
94010 m
Ref
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Outdoor testing with CSS
P2
340410 m
P3
P1
73910 m Pout 7 dBm 5 mW
462610 m Pout 24 dBm 250 mW
P4
Ref
94010 m Pout 9 dBm 7.9 mW
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Outdoor testing with CSS

• Measurement Challenge Teufelsberg
• 6483 m distance
• 7.7 dBm output power
• 18 dB antenna gain
• No FEC
• BER 10E-3

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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
Output Power _at_ antenna Range _at_ BER10-3
7 dBm 5 mW 740 m
9 dBm 7.9 mW 940 m
26 dBm 400 mW 6400 m
30 dBm 1 W 9800 m
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Need for StandardizationOle PlougRD
ManagerCentral Controls RDRefrigeration and
Air Conditioningwww.danfoss.com
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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 customers application requirements

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Conclusions

• CSS has qualities of both spread spectrum and
  UWB.
• CSS enhances robustness and range
• CSS adds mobility
• CSS can be implemented with todays technologies
• CSS is a global solution