Here is the same spectra represented in two extremely different ways. The sinc pulse is also used in some UWB implementations, so there are some similarities.
Benefits of constant power: 1. Cheaper to implement. 2. Lower human exposure.
CSS is appropriate for global markets because it operates well in global bands, such as 2.4. Robustness – latency intolerant
Used for some of the measurements
Page In the heart of Berlin. Cars, fences and street lamps in the trees along the street.
Page Output power is about 13 dBir. Only two measurement points because we have no BER measurement – these are finished consumer products. 10 -3 (first cracks in voice transmitted), then complete loss of voice transmission. Dect is also 2.4 GHz. Output power is 22 – 24 dBm Result – CSS has 2.5 times longer range
Page European office. Hall walls are stronger, inner walls are lighter. G = antenna gain (asymmetric rod antenna) Blue = Tx, Red = Rx. Locations not cherry-picked.
Page -93 dBm input sensitivity, +10 dBm output power = 103 dB link budget 2 is the perfect free space value. We used 2.1 as a conservative estimate.
Page Rod antennas were used for P1 and P4, directional antennas (18 dBi antenna gain) for P2 and P3. P2 is next to a railroad station with a 900 MHz / 1.8 GHz GSM base station. P3 is on top of a shopping center with two computer stores and a cell phone store. Ref is about 3 miles from Tegel international airport. There were many disturbers – ground radar from the airport, etc.
Page At P1, we varied the height of the Rx from 1.5 – 5 meters, saw no difference. P2 output power was approximately the same as P3, perhaps a bit lower. P3 had Bluetooth disturbers from the stores below.
This is the old eavesdropping site in Berlin during the cold war, now an airport radar location.
Page Measurements indicate that with 30 dBm output power, CSS can reach 9.8 km.
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: +49 30 399 954 188, E-Mail: email@example.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.
Introduction to Chirp Spread Spectrum (CSS) Technology presented by Zbigniew Ianelli Nanotron Technologies GmbH Berlin, Germany www.nanotron.com
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 with bandwidth B and a roll-off factor of 0.25 B S(f) f
The basic Chirp signal Chirp pulse: Sinc pulse (baseband): Sinc pulse (RF band):
Properties of signal forms in the air and baseband interfaces
Chirp pulses for the RF channel:
High robustness (BT>>1)
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 (B δ=1)
Easy signal processing (threshold detector)
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.
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 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 t f 1 0 1 0 0 1 f LO f HI Chirp pulse OOK with Null and Up-Chirp
Due to the high BT product, chirp pulses are very resistant against disturbances.
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.
CSS needs no synchronization; a wireless connection can be established very quickly.
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.
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
2000 km/h is equivalent to 1243 miles/hour
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.
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
E b /N 0 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 of Chirp Spread Spectrum (CSS) Technology presented by John Lampe Nanotron Technologies GmbH Berlin, Germany www.nanotron.com
d=23 m, P out = -15 dBm = 32 µW, G=1,5 dB, BER = 10 -3 d=15 m, P out = -15 dBm = 32 µW, G=1,5 dB, BER = 10 -3 Result: d = 23 m with P out = -15 dBm Calculated: d = 50 m with P out = +10 dBm, = 3 Indoor testing with CSS
Indoor testing with CSS d=5 m, P out = -30 dBm= 1 µW, G = 1,5 dB, BER = 10 -4 d=26 m, P out = 8 dBm = 6,3 mW, G = 1,5 dB, BER = 10 -3 CSS transmits 1Mbps with P out = 1 µW over 5m and with 6,3mW over 26m Load-bearing Walls
CSS Outdoor Test Summary G ant = 1 dB P out = 9 dBm, d = 940 m P out = 7 dBm, d = 740 m P out = 26 dBm, d = 6.4 km P out = 30 dBm, d = 9.8 km 6400 m 26 dBm = 400 mW 9800 m 940 m 740 m Range @ BER=10 -3 30 dBm = 1 W 9 dBm = 7.9 mW 7 dBm = 5 mW Output Power @ antenna
Need for Standardization Ole Ploug R&D Manager Central Controls R&D Refrigeration and Air Conditioning www.danfoss.com