09-11-2012, 04:02 PM
A Simulation Model of an Optical Communication CDMA System
[attachment=38779]
INTRODUCTION
The rapid evolution of communication technique and data handling defines the
following problem related to the constructing of orthogonal signal as a carrier of user data
in modern communication systems which use ideal or close to ideal autocorrelation
function and minimal values of cross correlation function.
It is necessary to overcome the problem of signal orthogonality and respectively the
code applied when we want to design an optical CDMA system [1]. In order to ensure the
required orthogonality of optical signals they should be constructed with pulse sequences
based on the property “no more then one hit”. As a result of this the relative level of the
indefiniteness function has a value no more then1/N , where N is the code length.
The impact of using pulse sequences with a property “no more then one hit” have
high speed and can provide huge number of active users in the common optical channel.
This is due to the minimal interference between users called multiple access interference
(MAI).
The finding sequences with this property “no more then one hit” resulting in close
ideal autocorrelation function and minimal values of cross correlation function is equivalent
to different mathematical tasks and well known combinatorial problem of defining
difference set balanced in two levels [3,4,5].
This paper suggests a simulation model of optical communication system using code
division multiple access, which use optical orthogonal codes for signature sequences of
active users in common optical channel.
A SIMULATION MODEL OF AN OPTICAL COMMUNICATION CDMA SYSTEM
The functional schema of simulation model of optical communication system using
code division multiple access, which use optical orthogonal codes for signature sequences
of active users in common optical channel with i pair transmitter and receiver is shown on
fig. 1.
The transmitter of functional schema includes blocks for input data which are used to
form model of different user’s messages and blocks for providing coding of information
data by using a proper signature code sequence. This signature code is an element of
family optical orthogonal code (OOC).
All signals from different users are multiplexed in the common optical communication
cannel, which in reality could be fiber optic media.
A decoder in the receiver for every individual user compares the input pulse
sequences with recorded copies of signature code word in order to define information data
for a definite user.
CONCLUSIONS
A simulation model of optical code division multiple access system using optical
orthogonal code is realized and proposed in this paper.
The experimental settings are invariant to algorithms for constructing optical
orthogonal codes.
The simulation model is developed in the graphical application Simulink of Matlab
program environment. The experiment includes modules for transmitters and receivers for
four users and it can ensure a possibility for arbitrary asynchronous access to common
optical channel.
The model can be expanded for arbitrary number of users and it won’t lead to bad
impact of the experiment conditions and assuming constraints.
It is foreseen a possibility to analyze and evaluate the parameters and characteristics
of the optical orthogonal codes under circumstances with existence of different by
structure and kind random noises in common communication channel.
The developed simulation schema of optical CDMA system can be used for tracking
the reaction of communication system when one wants to research different optical
orthogonal codes with arbitrary parameters.
[attachment=38779]
INTRODUCTION
The rapid evolution of communication technique and data handling defines the
following problem related to the constructing of orthogonal signal as a carrier of user data
in modern communication systems which use ideal or close to ideal autocorrelation
function and minimal values of cross correlation function.
It is necessary to overcome the problem of signal orthogonality and respectively the
code applied when we want to design an optical CDMA system [1]. In order to ensure the
required orthogonality of optical signals they should be constructed with pulse sequences
based on the property “no more then one hit”. As a result of this the relative level of the
indefiniteness function has a value no more then1/N , where N is the code length.
The impact of using pulse sequences with a property “no more then one hit” have
high speed and can provide huge number of active users in the common optical channel.
This is due to the minimal interference between users called multiple access interference
(MAI).
The finding sequences with this property “no more then one hit” resulting in close
ideal autocorrelation function and minimal values of cross correlation function is equivalent
to different mathematical tasks and well known combinatorial problem of defining
difference set balanced in two levels [3,4,5].
This paper suggests a simulation model of optical communication system using code
division multiple access, which use optical orthogonal codes for signature sequences of
active users in common optical channel.
A SIMULATION MODEL OF AN OPTICAL COMMUNICATION CDMA SYSTEM
The functional schema of simulation model of optical communication system using
code division multiple access, which use optical orthogonal codes for signature sequences
of active users in common optical channel with i pair transmitter and receiver is shown on
fig. 1.
The transmitter of functional schema includes blocks for input data which are used to
form model of different user’s messages and blocks for providing coding of information
data by using a proper signature code sequence. This signature code is an element of
family optical orthogonal code (OOC).
All signals from different users are multiplexed in the common optical communication
cannel, which in reality could be fiber optic media.
A decoder in the receiver for every individual user compares the input pulse
sequences with recorded copies of signature code word in order to define information data
for a definite user.
CONCLUSIONS
A simulation model of optical code division multiple access system using optical
orthogonal code is realized and proposed in this paper.
The experimental settings are invariant to algorithms for constructing optical
orthogonal codes.
The simulation model is developed in the graphical application Simulink of Matlab
program environment. The experiment includes modules for transmitters and receivers for
four users and it can ensure a possibility for arbitrary asynchronous access to common
optical channel.
The model can be expanded for arbitrary number of users and it won’t lead to bad
impact of the experiment conditions and assuming constraints.
It is foreseen a possibility to analyze and evaluate the parameters and characteristics
of the optical orthogonal codes under circumstances with existence of different by
structure and kind random noises in common communication channel.
The developed simulation schema of optical CDMA system can be used for tracking
the reaction of communication system when one wants to research different optical
orthogonal codes with arbitrary parameters.