Transcript 15-04-0353-00-004a-chirp-spread-spectrum-technology.ppt

July 2004
IEEE-15-04-0353-00-004a
Project: IEEE P802.15 Working Group for Wireless Personal Area 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.
Submission
Slide 1
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
Chirp Spread Spectrum (CSS)
Technology
presented by
John Lampe
Nanotron Technologies GmbH
Berlin, Germany
www.nanotron.com
Submission
Slide 2
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
Contents
•
•
•
•
•
A brief history of Chirp pulses
Summary of RF issues
Characteristics of Chirp pulses
Key properties of CSS
Test results
Submission
Slide 3
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
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
Submission
Slide 4
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
Wireless Technology Challenges
Real world wireless technology solutions must address
SU1
Signal-Corrupting Effects
Application Demands
Frequency Selective Fading
Global Regulatory Compliance
SU4
BS
Noise & Interference
Non-LOS Situations
Fast Fading Effects
SU2
Shadowing
Path Loss
Flat Fading
Multi-Path Fading
SU3
Submission
SU n
Slide 5
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
Wireless Technology Challenges
Real world wireless technology solutions must address
SU1
Signal-Corrupting Effects
Application Demands
Low Human Exposure
Location Awareness
Global Regulatory Compliance
SU4
Design Flexibility
SU2
BS
High Reliability
High Performance (Range/Data Rate)
Low Latency
Low Power Consumption
Low System Cost
SU3
Submission
SU n
Slide 6
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
Wireless Technology Challenges
Real world wireless technology solutions must address
SU1
Signal-Corrupting Effects
Application Demands
EN
SU4
SU2
Global Regulatory Compliance
BS
Standards
ARIB
FCC
SU3
Submission
SU n
Slide 7
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
Characteristics of Chirp Pulses
A chirp pulse is a frequency modulated pulse
S(f)
f
B
Up-Chirp in the time domain
(roll-off factor 0.25)
Spectrum of the chirp pulse with
bandwidth B and a roll-off factor of 0.25
Submission
Slide 8
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
The Basic Chirp Signal
Chirp pulse:
U0
t 2
U (t ) 
cos( 2f 0t 
)
2
BT
Sinc pulse (baseband):
U (t )  U 0
sin( Bt )
Bt
Sinc pulse (RF band):
U (t )  U 0
Submission
Slide 9
sin( Bt )
cos( 2f 0t   )
Bt
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
Similar to Both UWB and DSSS
• Like UWB
–
–
–
–
Sinc pulse in baseband
Ranging
Multipath rejection
Wideband modulation
• Like DSSS
–
–
–
–
Submission
2.4 GHz global band and others
Outdoor use allowed
Correlative system
Processing gain
Slide 10
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
How to Code Using CSS
f
Modulation techniques:
fHI
On-Off-Keying (OOK), for example:
1 0 1 0 0 1
fLO
t
Up-Chirp = „1“; Null = „0“
allows 2 independent coexisting networks
Superposed Chirps (4 possible states):
Chirp pulse
Null/Up-Chirp/Down-Chirp/
Superposition of Up- and Down-Chirp
allows one network with double the data rate
Submission
Slide 12
OOK with Null and Up-Chirp
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
Scalable Technology
Frequency spreading:
Basic information theory tells us that CSS benefits when
the bandwidth B of the Chirp pulse is much higher than the
data 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 a
very high BT product can be achieved, which transforms into a very
robust signal in the channel.
Submission
Slide 13
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
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 systems
where the available frequency bandwidth B is much higher than
the data rate R
Submission
Slide 14
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
Regulatory Compliance
• North America
– FCC 15.247
• Europe
– EN 300 328 v.1.4.1 (04/2003)
• Japan
– ARIB STD-T66
Submission
Slide 15
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
Key Properties of CSS
High robustness:
Due to the high BT product and their asynchronous nature, chirp
pulses 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.
Submission
Slide 16
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
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.
Submission
Slide 17
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
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:
Duration time T of the chirp
Center frequency of the chirp (ISM band)
Processing gain, BT product of the chirp
Eb/N0 at detector input (BER=0.001)
In-band carrier to interferer ratio (C/I @ BER=0.001)
Submission
Slide 18
1 µs
2.442 GHz
18 dB
14 dB
-4 dB
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
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:
Data rate
Relative speed between transmitter and receiver
Frequency shift due to Doppler effect
Equivalent shift of the message on the time axis
1 Mbps
2000 km/h
4.52 kHz
56.5 ps
Note:
2000 km/h is equivalent to 1243 miles/hour
Submission
Slide 19
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
Comparing CSS to DECT Outdoors
CSS vs. DECT
1,00E+00
CSS
DECT
1,00E-01
BER
1,00E-02
1,00E-03
1,00E-04
1,00E-05
1,00E-06
0
100
200
300
400
500
600
700
800
900
1000
Distance [m]
Submission
Slide 20
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
Indoor Testing With CSS
Result:
d = 23 m with Pout = -15 dBm
Calculated: d = 50 m with Pout = +10 dBm, a = 3
Submission
Slide 21
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
Outdoor Testing With CSS
P2
3404±10 m
P3
P1
4626±10 m
Pout = 24 dBm = 250 mW
739±10 m
Pout = 7 dBm = 5 mW
P4
Ref
940±10 m
Pout = 9 dBm = 7.9 mW
Submission
Slide 24
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
CSS Outdoor Testing Summary
Outdoor-Propagation; a = 2.1
130
Pout = 30 dBm,
d = 9.8 km
120
110
Pout = 26 dBm,
d = 6.4 km
attenuation [dB] for outdoor
100
Gant = 1 dB
Output Power
@ antenna
7 dBm =
d1( r )
101
90
103
120
Range @
BER=10-3
740 m
9 dBm = 7.9 mW
940 m
26 dBm = 400 mW
6400 m
Submission
W
Pout = 9 dBm,
d = 940 m
80
124
5 mW
30 dBm = 1
Pout = 7 dBm,
d = 740 m
70
60
50
40
0.01
0.1
9800 m
1
10
r
Slide 25
km
distance between transmitter and receive
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
Outdoor Link-Budget
• Link budget without cable losses or antenna-gain, best
case: LBbest = 103 dB
Outdoor-Propagation, a = 2,1
120
110
100
attenuation [dB] for outdoor
• Outdoor free space
propagation: distance ~ linkbudget with a = 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…
90
d1( r )
103
d = 940 m
80
70
60
50
40
0
500
1000
1500
2000
2500
r
m
distance between transmitter and receiver
Submission
Slide 26
Lampe, Nanotron
3000
July 2004
IEEE-15-04-0353-00-004a
3rd Party CSS Evaluation
Hochschule
Rapperswil:
Test #1 - Hallway
• 76,80 m indoor distance
• -18.9 dBm CSS output
power
• Reflective environment
• No FEC
• BER 10E-3
Submission
Slide 28
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
3rd Party BT vs. CSS Comparison
Hochschule Rapperswil:
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
Submission
Slide 29
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
3rd Party BT vs. CSS Comparison
Hochschule Rapperswil:
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
Submission
Slide 32
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
3rd Party BT vs. CSS Comparison
Submission
Slide 33
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
3rd Party BT vs. CSS Comparison
Submission
Slide 34
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
Summary
• Introduced CSS technology
• Explained behavior and benefits
• Showed test results that demonstrate
some of CSS’ capabilities
Submission
Slide 37
Lampe, Nanotron
July 2004
IEEE-15-04-0353-00-004a
Conclusions
Chirp Spread Spectrum (CSS):
• Combines DSSS and UWB strengths
• Adds location-awareness
• Enhances robustness, range, and mobility
• Implementable with today’s technologies
• Globally certifiable
Submission
Slide 38
Lampe, Nanotron