Statement of Research

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27 Νοε 2013 (πριν από 3 χρόνια και 10 μήνες)

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Statement of Research

Topic:
Chaos
-
Based Secure Communication

THANG MANH
HOANG


A.

Overview


Over the last few decades,
communication systems have been developed rapidly to
meet the
increasing
human needs.
Those are not only
in the variety of

services, but a
lso
in

quality of services.
Hence, the
conventional
fundamental
s

of

communication
techniques ha
ve

been

faced with strict challenges such as the increase in transmission
rate
and

in privacy
.

For a band
wide
requirement, optical

systems offer
a transmission
about
terabit
s

per seconds

in the distance of hundreds of kilometers
, and wireless
systems can support the services required the rate of hundreds megabits per second
. It
can be regarded that the
most of
available services can be run reliably
. However, such

transmission rates
have

not
reached
natural one
s

yet
, and will be exhausted by s
ome
future services such as multimedia and others
.

Moreover,
conventiona
l modulation
techniques
are
mostly
based on periodic signals
. As a result, the system security can not
be deployed on the phy
sical layer due that periodic signals are easily detected by
eavesdroppers
. For that reason, mathematic algorithms such as RAS, DES and so on
are developed to maintain the systems secure.

With the hope of improving bit rate as
well as

security, applications of nonlinear dynamics in communication have received
much interest and become an active area of research.

Recent years, researchers working on the nonlinear field have developed some novel
modulation methods

[
1
]
-
[5
]

which utilize no
n
-
periodic signals.
More specifically, a group
of
logical bits
can be represented
by
a piece of a
non
-
periodic signal

or
by a sequence of
real values which are generated by
dynamical

systems [
6
].
The advantage offering by
such methods
is

that non
-
periodic
signals are produced easily by s
ome
nonlinear
circuit
s
.

In addition,
security of communication
system
s

[
7
]
can be assured if
highly
-
dimensional chaotic systems as well as appropriate
modulation schemes
are
employed.

My research concentrates on

(i)

investig
ation on synchronous regimes of
dynamical

systems
which present potential applications in communication
s
,
(ii)

application of
synchronization of
chaotic

systems in communication
s

including
chaotic
modulation
technique
s

and security
, and
(iii)

implement cha
otic communication systems on VLSI.


B.

Background


Since Pecora and Caroll introduced the model of synchronization of dynamical
systems [
8
], there has been several synchronization models proposed and pursued
[
9
]
-
[
13
].

Roughly speaking, one chaotic system (pl
ays a role of master) sends a driving
signal to other system(s) (plays a role of slave(s)) to establish the synchronous regime.
As a result, their chaotic trajectories remain in step with each other during temporal
evolution.

In practical
, models of synchr
onization of dynamical systems has been
utilized in many fields, i.e. lasers [
14
]
[15]
, biological [
16
]
[17]
, control [
18
], etc.
Recently,
o
ne of
a
pplication
s

of synchronization
has been investigated actively is
in
communication
s

[
6
][
19
]
[20]
.

More specifical
ly, synchronization of chaotic systems is
applied to design chaotic secure communica
tion systems and to propose new
transmission methods.

For the application of synchronization of dynamical systems in transmission, there
are several models proposed to modu
late the information signal on chaotic signal, i.e.
multiplicative [1] and parametric [2][3] modulations, additive masking [2],
chaos shift
keying
(CSK)
[
4
],
synchronization
-
manifold shift keying [
5
].

F
or a short
period

of
development, chaotic communicatio
ns has shown
a potential alternative for
conventional one.

However, one of disadvantages of chaotic communication is the
robustness.
A c
haotic signal
is easy to be distorted by noise when it is sent

via a noise
channel
. As a result, BER

of proposed models

is slightly low in compared with that of
conventional ones
.
Recently, some new improvement

in BER

has been reported [
21
]
with orthogonal
-
CSK.

For the security application of synchronization of dynamical
systems, there are many models proposed [
22
]

in diffe
rent ways

but they has been
broken thereafter
.

Anyway, a secure system must be based on existing modulation
methods, and some schemes are used to hide the information in chaotic signals.
So far,
there are two
categories of
methods used to
unmask
message si
gnal in

chaotic secure
communication systems, i.e. characteristic
-
based

[23]
-
[26]

and identification
-
based

[27][28]
. Characteristic
-
based method
s

are

analyzed
different features of transmitted
signals to extract message signal

without knowing the detail of

chaotic system at the
transmitter. In contrast to Characteristic
-
based methods, identification
-
based one
s

require knowing the structure of chaotic dynamics of master system at the transmitter.
Full detail about structure of master can be found by some rec
onstruct methods

by
observing transmitted signals
.

Therefore
, security
of chaotic communication
is
considered by two main points in a secure communication system.
First of all,
chaotic

system playing as master at the transmitter should exhibit complex dyna
mics (high
dimension)
.
Typically, o
ne of choices is delay systems which create very
highly
-
dimensional dynamics [
29
]
. For second point
, it is that the transmitter should
produce and send a complex signal. Complexly transmitted signal sent on the channel
ma
ke

eavesdroppers difficult in reconstructing processes
. In practical, observer
-
based
synchronization schemes
[
30
]
allow to produce complex signals

for modulation process
.

In conclusion, chaos synchronization has been applied in communication
, but in fact
t
here are
numerous

issues which ha
ve

not been addressed yet, i.e. improving for the
performance of proposed systems

and making them suitable for various transmission
environments

of

radar,
ultra wide

band,
and
CDMA

systems
, etc
.


Reference

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