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- 1 , - 1 , 1 , 1 , 1 , 3 , 5 , 7 , 7 , 7 , 5 , 5 .

For marker B, starting at the same point in the data sequence and performing the associated moving weighted sum, produces

1 , 1 , 3 , - 1 , - 5 , - 1 , - 1 , 1 , 7 , - 1 , 1 , - 3 .

With the two correlator output sequences shown, started two values prior to the start of the seven-symbol marker, we want theflag indicating a frame start to occur with point number 9 in the correlator sequences shown.Clearly, the correlator output for marker B has a much sharper peak at its ninthvalue than the correlator output of marker A. This should enhance the robustness of the use of marker Brelative to that of marker A against the unavoidable presence of noise.

The binary signal from Equation 8 is shown with a seven symbol embedded marker m_1, m_2, ..., m_7. The process of correlation multiples successive elements of the signal by the marker, and sums. The marker shifts to the right and the process repeats. The sum is largest when the marker is aligned with itself because all the terms are positive, as shown in the bottom part of the diagram. Thus the shift with the largest correlation sum points towards the embedded marker in the data sequence. Correlation can often be useful even when the data is noisy.
The binary signal from [link] is shown with a seven symbol embedded marker m 1 , m 2 , . . . , m 7 . The process of correlation multiples successive elementsof the signal by the marker, and sums. The marker shifts to the right and the process repeats. The sum is largest when the marker is aligned with itselfbecause all the terms are positive, as shown in the bottom part of the diagram. Thus the shift with the largest correlation sum pointstowards the embedded marker in the data sequence. Correlation can often be useful even when the data is noisy.

Marker B is a “maximum-length pseudonoise (PN)” sequence. One property of a maximum-length PN sequence { c i } of plus and minus ones is that its autocorrelation is quite peaked:

R c ( k ) = 1 N n = 0 N - 1 c n c n + k = 1 , k = N - 1 N , k N .

Another technique that involves the chunking of data and the need to locate boundaries between chunksis called scrambling . Scrambling is used to “whiten” a message sequence(to make its spectrum flatter) by decorrelating the message.The transmitter and receiver agree on a binary scrambling sequence s that is repeated over and over to form a periodic string S that is the same size as the message. S is then added (using modulo 2 arithmetic) bit by bit to the message m at the transmitter, and then S is added bit by bit again at the receiver.Since both 1 + 1 = 0 and 0 + 0 = 0 ,

m + S + S = m

and the message is recaptured after the two summing operations.The scrambling sequence must be aligned so that the additions at the receiver correspond to theappropriate additions at the transmitter. The alignment can be accomplishedusing correlation.

Redo the example of this section, using M atlab .

Add a channel with impulse response 1 , 0 , 0 , a , 0 , 0 , 0 , b to this example. (Convolve the impulse response of the channel with the data sequence.)

  1. For a = 0 . 1 and b = 0 . 4 , how does the channel change the likelihood that the correlation correctly locatesthe marker? Try using both markers A and  B .
  2. Answer the same question for a = 0 . 5 and b = 0 . 9 .
  3. Answer the same question for a = 1 . 2 and b = 0 . 4 .

Generate a long sequence of binary random data with the marker embedded every 25 points. Check that marker Ais less robust (on average) than marker B by counting the number of times marker A misses the frame start comparedwith the number of times marker B misses the frame start.

Create your own marker sequence, and repeat the previous problem. Can you find one that does better thanmarker B?

Use the 4-PAM alphabet with symbols ± 1 , ± 3 . Create a marker sequence, and embed it in a long sequenceof random 4-PAM data. Check to make sure it is possible to correctly locate the markers.

Add a channel with impulse response 1 , 0 , 0 , a , 0 , 0 , 0 , b to this 4-PAM example.

  1. For a = 0 . 1 and b = 0 . 4 , how does the channel change the likelihood that the correlation correctly locatesthe marker?
  2. Answer the same question for a = 0 . 5 and b = 0 . 9 .

Choose a binary scrambling sequence s that is 17 bits long. Create a message that is 170 bits long, andscramble it using bit-by-bit mod 2 addition.

  1. Assuming the receiver knows where the scrambling begins, add s to the scrambled data and verify that the output is the same as the original message.
  2. Embed a marker sequence in your message. Use correlation to find the marker and toautomatically align the start of the scrambling.

Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
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Source:  OpenStax, Software receiver design. OpenStax CNX. Aug 13, 2013 Download for free at http://cnx.org/content/col11510/1.3
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