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

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [CSS-Clarifications-Comparisons-and-White-Papers] Date Submitted: [14 September 2004] Source: [John Lampe] Company [Nanotron Technologies GmbH] Address [Alt-Moabit 61, 10555 Berlin, Germany] Voice:[+49 30 399 954 135], FAX: [+49 (30) 399 954 188], E-Mail: [J.Lampe@nanotron.com] Re: [This submission is in response to the TG4a CFI] Abstract: [This submission includes some clarifications from earlier presentations, comparisons of CSS to DSS, and CSS white papers that have been found in the public domain.] Purpose: [This document provides additional background information supporting the proposal of CSS as the baseline PHY for TG4a] 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. John Lampe, Nanotron Technologies, GmbH

2. CSS: Clarifications, Comparisons, and Public Papers presented by John Lampe Nanotron Technologies GmbHBerlin, Germany www.nanotron.com John Lampe, Nanotron Technologies, GmbH

3. 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. John Lampe, Nanotron Technologies, GmbH

4. 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. John Lampe, Nanotron Technologies, GmbH

5. Similar to DSSS • 2.4 GHz global band and others • Outdoor use allowed • Correlative system • Processing gain John Lampe, Nanotron Technologies, GmbH

6. Comparison of CSS to DSS John Lampe, Nanotron Technologies, GmbH

7. Review of a Few of the Public Domain White Papers on Chirp Spread Spectrum • Fast Adaptive Interference Cancellation in Low Cost SAW Based Chirp Spread Spectrum Systems • A Robust High Speed Indoor Wireless Communications System using Chirp Spread Spectrum • Gated Chirps for Signal Processing and Communication Engineering • Bit Error Rate Probabilities of Chirp Spread Spectrum Modulation in the AWGN Channel with Overlap • A Chirp Spread Spectrum DPSK Modulator and Demodulator for a Time Shift Multiple Access Communication System by using SAW devices John Lampe, Nanotron Technologies, GmbH

8. Fast Adaptive Interference Cancellation in Low Cost SAW Based Chirp Spread Spectrum Systems • Chirp impulse compression is a well known technique for reliable data transmission. • For a fast reliable data transmission in a heavily distorted indoor environment, a SAW based chirp spread spectrum system operating in the 2.45 GHz ISM is presented. • The use of a bandwidth as wide as allowed make it possible to overcome Rayleigh fading with large coherence bandwidths. • Since a matched filter system is susceptible for jammers, a technique of fast adaptive cancellation without a loss of simplicity is presented. • The system was tested in different electromagnetically polluted indoor areas John Lampe, Nanotron Technologies, GmbH

9. A Robust High Speed Indoor Wireless Communications System using Chirp Spread Spectrum • The three elements required for a CSS system to perform optimally in the multipath environment are presented: • a chirp SAW spreader/correlator for resolution of the channel multipath, • a phase-differential modulation scheme to co-phase the multipath components • a RAKE structure for recovery and recombination of the symbol energy. • An advantage of CSS is that all three of these elements can be implemented with simple analog hardware • A prototype CSS system is demonstrated along with simulated and measured performance plots in the indoor channel. • The results indicate that CSS can perform within 2 dB of Gaussian DQPSK in 10m NLOS indoor channels with excess delay > 200 ns, down to bit error rates of 10-7 with single omni antennas in transmitter and receiver and no coding, at data rates of 20 Mb/s. John Lampe, Nanotron Technologies, GmbH

10. Gated Chirps for Signal Processing and Communication Engineering • A simple and very robust spread spectrum modulation is the use of chirp signals for transmission and to implement a matched filter in the receiver. • A method of signal processing in SAW based chirp impulse compression systems, yielding a better performance and an enhanced capability of interference suppression is introduced. • The method applied, a fast adaptive interference cancellation in a low cost spread spectrum system for data transmission in ISM frequency band is practical with a high immunity against a variety of jammers as characterized in simulations and experimental measurements. • The method can be applied for a wide range of applications, for interference reduction, control of the transmitted spectrum, etc; even for low cost systems. John Lampe, Nanotron Technologies, GmbH

11. Bit Error Rate Probabilities of Chirp SpreadSpectrum Modulation in the AWGN Channel with Overlap • The focus of this paper is to present performance calculations for systems which use chirp signals in the implementation of spread spectrum communications. • Two of the most basic Chirp Spread Spectrum (CSS) systems are discussed: • Binary Orthogonal Keying (BOK), in which chirps with different characteristics are used to represent different symbols • Direct Modulation (DM), in which the data modulation is performed separately from the chirping process • Expressions for the BER in AWGN are derived for BOK CSS, and it is shown that its performance is not only highly dependant on the timebandwidth product of the chirp, but also the amount of overlap between adjacent symbols. • DM CSS, on the other hand, is shown to be relatively immune to symbol overlap, producing results similar to non-overlapping systems with an overlap below a maximum threshold. John Lampe, Nanotron Technologies, GmbH

12. This white paper describes the modulator and demodulator for a DPSK modulated chirp signal • 100 MHz spectrum • Employs non-linear chirp modulation to yield a flat amplitude in the time domain • Demodulator had 19 dB of process gain • Examined the capability of multiple access of chirp spread spectrum using time shifted sequences • The authors confirmed up to 20 multiple access links with minimum degradation to other links (~1 dB) John Lampe, Nanotron Technologies, GmbH