July 2004 Lampe, Nanotron Slide 1 IEEE-15-04-0353-00-004a Submiss ion Project: IEEE P802.15 Working Group for Wireless Personal Area Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Networks (WPANs) Submission Title: Introduction to Chirp Spread Spectrum (CSS) Technology Date Submitted: July 13, 2004 Source: John Lampe Company: Nanotron Technologies Address: Alt-Moabit 61, 10555 Berlin, Germany Voice: +49 30 399 954 135, FAX: +49 30 399 954 188, E-Mail: [email protected]Re: Discussion of interesting RF technology Abstract: Presentation on CSS for IEEE 802.15.4a Purpose: Technology introduction 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.
Transcript
July 2004
Lampe, NanotronSlide 1
IEEE-15-04-0353-00-004a
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)
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.
July 2004
Lampe, NanotronSlide 2
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Submission
Chirp Spread Spectrum (CSS)Technology
presented by
John Lampe Nanotron Technologies GmbH
Berlin, Germany
www.nanotron.com
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Contents
• A brief history of Chirp pulses
• Summary of RF issues
• Characteristics of Chirp pulses
• Key properties of CSS
• Test results
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A Brief History of Chirp Pulses
• Used by dolphins and bats• Patent for radar applications about 1940 by Prof.
Hüttmann, further developed by Sidney Darlington (Lifetime IEEE Fellow) in 1947 („Pulse Compression Radar“)
• Patented by Canon for data transmission in fiber optic systems in mid-90s
• Chirp Spread Spectrum for commercial wireless data transmission investigated since 1997
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Wireless Technology Challenges
SU1
SU2
SU3
SU4
BS
SU n
Signal-Corrupting Effects
Application Demands
Global Regulatory Compliance
Real world wireless technology solutions must address
Path Loss
Multi-Path Fading
Frequency Selective Fading
Fast Fading Effects
Flat Fading
Noise & Interference
Shadowing
Non-LOS Situations
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Wireless Technology Challenges
SU1
SU2
SU3
SU4
BS
SU n
Signal-Corrupting Effects
Application Demands
Global Regulatory Compliance
Real world wireless technology solutions must address
Low Power Consumption
Low System Cost
Low Human Exposure
Low Latency
Design Flexibility
High Reliability
Location Awareness
High Performance (Range/Data Rate)
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Wireless Technology Challenges
SU1
SU2
SU3
SU4
BS
SU n
Signal-Corrupting Effects
Application Demands
Global Regulatory Compliance
Real world wireless technology solutions must address
FCC
EN
ARIB
Standards
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Characteristics of Chirp Pulses
A chirp pulse is a frequency modulated 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
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The Basic Chirp Signal
Bt
BtUtU
)sin(
)( 0
)2cos()sin(
)( 00
tfBt
BtUtU
)2
2cos()(2
0
0 t
tfBT
UtU
Chirp pulse:
Sinc pulse (baseband):
Sinc pulse (RF band):
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Similar to Both UWB and DSSS
• Like UWB– Sinc pulse in baseband– Ranging– Multipath rejection– Wideband modulation
• Like DSSS– 2.4 GHz global band and others– Outdoor use allowed– Correlative system– Processing gain
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
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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.
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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 systemswhere the available frequency bandwidth B is much higher thanthe data rate R
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Regulatory Compliance
• North America– FCC 15.247
• Europe– EN 300 328 v.1.4.1 (04/2003)
• Japan– ARIB STD-T66
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Key Properties of CSSHigh robustness:
Due to the high BT product and their asynchronous nature, chirppulses are very resistant against disturbances.
Multipath resistant:Due to the frequency spreading of chirp pulses, CSS is very immune against multipath fading; CSS can even take advantage of RF echoes.
Long range:Due to high system gain, as well as noise, interference and fading resistance, CSS has exceptional range for a given transmit power and conditions.
Location awareness:CSS gives the ability to determine the distance (range) between two stations.
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Key Properties of CSS
Low power consumption:CSS allows the designer to choose a simple analog implementation, which often consumes much less power.
Low PHY latency:With CSS a wireless connection can be established very quickly because synchronizations on carrier frequency and data clock are not required.
Antenna position:Reception is possible with almost any antenna position due to the wide bandwidth.
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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-bandinterferences.
Example:Duration 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
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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:Data rate 1 MbpsRelative 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
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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
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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
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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
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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 Testing Summary
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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 had 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
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3rd Party CSS Evaluation
Test #1 - Hallway • 76,80 m indoor distance
• -18.9 dBm CSS output power
• Reflective environment
• No FEC
• BER 10E-3
HochschuleRapperswil:
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3rd Party BT vs. CSS Comparison
Test #2 - Enclosed Metal Cabinet
• No external wires
• Reflective environment
• No FEC
• BER 10E-3
• 25 m distance indoor
• 7.7 dBm output power
• WLAN with +20 dBm active
Hochschule Rapperswil:
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3rd Party BT vs. CSS Comparison
Test #3 – Parking Garage
•Transmitter located in parking garage
• Shielded by metal cable conduit
• Metal ventilation pipe in front of TX
• 7.7 dBm output power
• Reflective environment (concrete, metal)
• Measurement through door
• No FEC
• BER 10E-3
Hochschule Rapperswil:
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3rd Party BT vs. CSS Comparison
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3rd Party BT vs. CSS Comparison
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Summary
• Introduced CSS technology
• Explained behavior and benefits
• Showed test results that demonstrate some of CSS’ capabilities
