15 03-0460-00-0000-css-tutorial

November 2003

Lampe, Ianelli, NanotronSlide 1

doc.: IEEE 802.15-03-0460-00-0000

Submission

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Submission Title: Introduction to Chirp Spread Spectrum (CSS) TechnologyDate Submitted: November 11, 2003Source: John Lampe, Zbigniew Ianelli Company: Nanotron TechnologiesAddress: Alt-Moabit 61, 10555 Berlin, GermanyVoice: +49 30 399 954 135, FAX: +49 30 399 954 188, E-Mail: [email protected]

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.

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

Introduction toChirp Spread Spectrum (CSS)

Technology

presented by

Zbigniew Ianelli Nanotron Technologies GmbH

Berlin, Germany

www.nanotron.com

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

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

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

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

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

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)

Spectrum of the chirp pulse withbandwidth B and a roll-off factor of 0.25

B

S(f)

f

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

The basic Chirp signal

Bt

BtUtU

)sin(

)( 0

)cos()sin(

)( 00

tBt

BtUtU

)2

cos()(2

0

0 t

tBT

UtU

Chirp pulse:

Sinc pulse (baseband):

Sinc pulse (RF band):

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

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)

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

Scalable Technology

Frequency spreading:

Basic information theory tells us that CSS benefits whenthe 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.

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

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 systemwhere available frequency bandwidth B is much higher thanthe data rate R

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

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-Chirpallows one network with double the data rate

t

f1 0 1 0 0 1

fLO

fHI

Chirp pulse

OOK with Null and Up-Chirp

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

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.

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

Mobility Properties of CSS

Resistance against Doppler effect:The Doppler effect causes a frequency shift of the chirp pulse, whichintroduces a negligible shift of the baseband signal on the time axis.

Example:Bandwidth of the chirp 80 MHzDuration of the chirp 1 µsCenter frequency of the chirp (ISM band) 2.442 GHzRelative speed between transmitter and receiver2000 km/hFrequency shift due to Doppler effect 4.52 kHzEquivalent shift of the message on the time axis 56.5 ps

Note:2000 km/h is equivalent to 1243 miles/hour

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

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-bandinterferences.

Example:Bandwidth B of the chirp 64 MHzDuration time T of the chirp 1 µsCenter frequency of the chirp (ISM band) 2.442 GHzProcessing 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

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

Some Applications and Measurements ofChirp Spread Spectrum (CSS)

Technology

presented by

John LampeNanotron Technologies GmbH

Berlin, Germany

www.nanotron.com

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

• 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

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

• Applications desiring extended range, such as:– Meter Reading– Building Automation– And other longer-range applications where repeaters

are not practical

Enhanced Applications / Markets

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

Evaluation BoardIncludes:

• RF IC

• SAW filter

• Optimized balun for asymmetrical antenna operation

• Crystals

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

CSS vs. DECT

1,00E-06

1,00E-05

1,00E-04

1,00E-03

1,00E-02

1,00E-01

1,00E+00

0 100 200 300 400 500 600 700 800 900 1000

Distance [m]

C SS D EC T

BE

R

Comparing CSS to DECT Outdoors

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

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 dBmCalculated: d = 50 m with Pout = +10 dBm, = 3

Indoor testing with CSS

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

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

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

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! 0 500 1000 1500 2000 2500 3000

40

50

60

70

80

90

100

110

120Outdoor-Propagation, a = 2,1

distance between transmitter and receiver

atte

nuat

ion

[dB

] fo

r ou

tdoo

r

d1( )r

103

r

m

d = 940 m

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

Testing CSS on Hahneberg, Berlin-Spandau

4626±10 m

3404±10 m

739±10 m

Ref

P1

P2

P3

P4940±10 m

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

Outdoor testing with CSS

4626±10 m Pout = 24 dBm = 250 mW

3404±10 m

739±10 mPout = 7 dBm = 5 mW

Ref

P1

P2

P3

P4

940±10 m Pout = 9 dBm = 7.9 mW

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

Outdoor testing with CSS

Measurement Challenge: Teufelsberg

•6483 m distance

• 7.7 dBm output power

• 18 dB antenna gain

• No FEC

• BER 10E-3

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

0.01 0.1 1 1040

50

60

70

80

90

100

110

120

130Outdoor-Propagation; a = 2.1

distance between transmitter and receive

atte

nuat

ion

[dB

] for

out

door

d1( )r

101

103

120

124

r

km

Output Power @ antenna

Range @ BER=10-3

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

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

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

Need for Standardization

Ole PlougR&D Manager

Central Controls R&DRefrigeration and Air Conditioning

www.danfoss.com

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

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

November 2003


doc.: IEEE 802.15-03-0460-00-0000

Submission

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

Documents

15 03-0460-00-0000-css-tutorial