Intro_chaos_communication.ppt

School of Electrical & Computer Engineering : September 2004
Yuu Seng. Lau (Jimmy)
Supervisors: Dr. Zahir M. Hussain
RMIT PhD Research Candidate
Centre for Advanced Technology in Telecommunications (CATT)
School of Electrical and Computer Engineering
RMIT University , Melbourne, Victoria, Australia
Chaos theory application in
communications

Slide 2
Outline
 Introduction to communication
 Current trend and technology
 General communication scheme
 Overview of chaos theory in communications
 Potential use of chaos in communications
 Advantage and aspect of the use in communications
 Simulation result and performances
 Future research and direction
 Use of chaos theory in future communication
 Analysis tool for chaos theory

Slide 3
Communications technology
 Past and future wireless communications
 Early mobile communications
 (analog system using AM , FM and other method) used for voice
 2G (GSM, IS-95 )
 Voice and low rate data
 Current 3G
 (multi-user system used CDMA technique), Voice and high rate data
 Future trend 4G
 (multi-carrier combine of CDMA and OFDM), High speed data for
multimedia application in
 Other technology
 Fix line communication
 Broadband (ADSL, Cable network, WLAN, etc)
 Wide area wireless network communication (Wireless broadband, Wi-
MAX, etc)
 Other (Home network, trunk radio, Bluetooth, infra-red and etc)

Slide 4

Slide 5
Limitation of a communication system
 Physical link layer is the major limitation for
communication technology
 Physical channel has a limited physical property and
capacity
 Transmitted signal is distorted by physical channel during
the transmission and receiving
 Active research in overcome this physical limitation and
problem
 Advance DSP techniques
 Modulation, channel estimation, channel equalization,
noise reduction, beamforming, source coding, error
correction coding, interleaving and etc.

Slide 6
Communication transmitter block diagram
Data Encoding Channel Coding
Data
Source coding
(turbo code,
convolution code,
etc)
Redundancy
coding (CRC)
Digital modulation
(BPSK, QPSK, QAM,
etc)
Multi-User modulation /
Multi-carries modulation
(Spread spectrum,
CDMA, TDMA, FDMA,
OFDM)
Interleaving/
scramble coding
Antenna

Slide 7
General communication block diagram
Data
Encoding
Channel
Encoding
Data Antenna/
transmitter
Data
Decoding
Channel
Decoding
Data Antenna/
receiver
Physical
Channel

Slide 8
Communication issues and requirements
 Bandwidth limitation vs efficiency
 Physical channel limitation due to technical constraints, Government
regulation, and technical standard.
 Redundancy of message or data (voice data) is not needed.
 Efficiency use of physical channel or frequency spectrum
 Publicity vs Security
 Standard format are known to public domain
 Physical media used to transmit or receive signals are publically
accessible.
 Sharing resource on physical media
 Robustness vs imperfections
 Received a distorted version of transmitted signal due to interfering
from noise, channel distortion
 Hardware noise and distortion
 Algorithm robustness again different condition.
 Standard transmission scheme is needed. However receiver format is
not always standard.

Slide 9
Communication use of chaos theory
 Chaotic signal : random, irregular behavior, uncorrelated aperiodic, and
is impossible to predict over longer times period.
 These properties have beneficial and are highly required for spread
spectrum communication (current 3G and future 4G), secure
communications (military communication)
 In early 1990, The possible use of chaos theory for analog
communication is introduced.
 In mid 90’s, the ideal is extended to Digital communications in spread
spectrum communications.
 Provide better auto- and cross-correlation property for communication
systems suitable for multi-user communications
 Used in encryption and cryptographic which provide better secure
communications

Slide 10
Proposal used in communications
Data
Encoding
Channel
Encoding
Data Antenna/
transmitter
Data
Decoding
Channel
Decoding
Data Antenna/
receiver
Physical
Channel
Encryption /
Cryptography
Digital modulation
(CSK, DCSK,
COOK, Masking)
CDMA code (Chaos
code sequences)

Slide 11
Chaos generator used in communications
 A few simple chaos equation :
 One dimension
 1.
 2.
 3.
 multi dimension
 e.g.
 Lorenz equation
 Lyapunov map
2
1 1 n
n ax
x 


)
1
(
1 n
n
n x
rx
x 


))
cos(
cos(
2
1 n
n
n x
px
x 

))
cos(
cos( 2
2
1 

 n
n
n x
px
x

Slide 12
Advantage of chaos in communications
 Broad-band and long sequence
 Non-linear, non-periodic and is continue sequence provided a broad-
band aspect for communications
 Spread over wide range of frequency (broad-band signal)
 Broad-band signals used to combat narrowband imperfections or
frequency-selective fading
 Orthogonality and correlation property
 AWGN noise like property
 Spread spectrum communication
 Can transmit below noise floor which provide some secrecy of
transmission (PSD is noise like)
 Orthogonal property
 Useful in multi-user or multi-carries communication.
 Security and complexity
 Irregular behaviors make attacker hard to guess or predict the signal
over long period of time

Slide 13
Multi-user CDMA simulation results
-5 0 5 10 15 20 25 30
10
-4
10
-3
10
-2
10
-1
10
0
Eb/No (dB)
BER BER versus Eb/No in the Rayleigh and AWGN channel for multi users system
PN with 16 spreading sequence , K = 2
Chaos with 16 spreading sequence , K = 2

Slide 14
Future direction and research
 Study different chaos generator for communications use.
 Finding the simple yet efficient chaos generator for communications
use.
 Analysis tool for chaos theory (high order statically analysis)
 Interesting result had been seen using second order statistical property
analysis
 Study of different sequence generated with different initial condition.
 Study the continue sequence generated using the same condition (primary
study show this will provide better property in high order statistic analysis.
 Extend the idea for 4G communications.
 Possible analog communications for home network.
 Study the effect of chaos sequence apply in MC-CDMA, CDMA-
OFDM and other spread spectrum communication

Intro_chaos_communication.ppt

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