Method

A common method used in chaos engineering is direct-sequence spread-spectrum (DSSS)

technique which require good periodic

variation properties ,good correlation,a

wideband spectrum, initial condition must be sensitive to improve the

security at physical layer. Studies show that

if an intruder may possibly recover a

chaotic sequences by a method called blind estimation which will use the

data given from the different sequences to identify the symbols period given

from the this information from your

original data. We can enhance this security issue by creating using a

varied period according to the behavior of the chaotic spread in the

communication system. How this works exactly is the information given from the

system is given in a variable symbol period and is multiplied with a chaotic sequence to perform

the spread-spectrum process. Below are different examples of different discrete-time

models that show the synchronization, and analyzation for a spreading scheme with variable symbol

periods as well as a despreading scheme

with sequence. We cover a series of Multi-access performance of white Gaussian

noise (AWGN) which is calculated by

both numerical computation and

theoretical derivation . After this we compare and contrast the computer and

actual simulations to verify that received data is correct our obtained results

point out that our proposed technique can protect the DSSS systems against the

detection of symbol period from the intruder, even if he has full information

on the used chaotic sequence

Spreading scheme with variable bit period

Block diagram demonstrates a spreading scheme with a pulse

chain that has a variable inter-pulse intervals. We used {pl}, as the variable interval pulse

generator (VIPG) The input we used is the

{xk} to stand for the chaotic sequence. Which is sampled at each

triggered input pulse. (1)pl=P(t?tl),

with (2)P(t)={10?t??,0 Then the tl is the when you generate the lth pulse

and the

output sample xl is then converted into a positive integer ?l.This

happens by using a transformation

function example (?l=f(xl)).Once f( · )

is determined the sequence {xl} varies

range is discovered and the xmin

& xmax, {?l} is then in direct

correlation to the range

?min=f(xmin)=0,?max=f(xmax)=?m.So in order to determine the function

f( · ), we had to usea fixed value for ?m. After we choose the value the xmin, xmax of the function is then divided

into (?m+1) value intervals, xmin+j?,xmin+(j+1)?,with j varying from 0 to ?m

and ? being a constant defined by(3)?=(xmax?xmin)/(?m+1).Once the input number

xl falls in the range of xmin+j?,xmin+(j+1)?, the value for the other

source value ?l can finally be determined for example:

(4)?l=f(xl)=?xl?xmin??,Depending on the value of ?l, will determine (l+1)after that the pulse is created at the

output of the VIPG at the tl+1 given by (5)tl+1=tl+(?+?l)?,? is the chip period

of the chaotic sequence {xk} and ? is a fixed integer and the value is fixed.