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If all has gone well, the quantized output mprime should be identical to the original message string.The function pam2letters.m rebuilds the message from the received signal. The final line of the programcalculates how many symbol errors have occurred (how many of the ± 1 , ± 3 differ between the message m and the reconstructed message mprime ).

% first run pulseshape.m to create x y=xcorr(x,ps);                     % correlate pulse with received signalz=y(N*M:M:N*M)/(pow(ps)*M);       % downsample to symbol rate and normalize mprime=quantalph(z,[-3,-1,1,3])';  % quantize to +/-1 and +/-3 alphabet pam2letters(mprime)               % reconstruct messagesum(abs(sign(mprime-m)))          % calculate number of errors
recfilt.m undo pulse shaping using correlation (download file)

In essence, pulseshape.m is a transmitter, and recfilt.m is the corresponding receiver. Many of the details of this simulation can be changedand the message will still arrive intact. The following exercises encourage exploration of some of the options.

Other pulse shapes may be used. Try

  1. a sinusoidal shaped pulse ps=sin(0.1*pi*(0:M-1));
  2. a sinusoidal shaped pulse ps=cos(0.1*pi*(0:M-1));
  3. a rectangular pulse shape ps=ones(1,M);

What happens if the pulse shape used at the transmitter differs from the pulse shape used at the receiver? Try using theoriginal pulse shape from pulseshape.m at the transmitter, but using

  1. ps=sin(0.1*pi*(0:M-1)); at the receiver. What percentage errors occur?
  2. ps=cos(0.1*pi*(0:M-1)); at the receiver. What percentage errors occur?

The received signal may not always arrive at the receiver unchanged. Simulate a noisy channelby including the command before the xcorr command in recfilt.m . What percentage errors occur? What happens as you increase or decrease the amount ofnoise (by changing the 1.0 to a larger or smaller number)?

Frame synchronization: from symbols to bits

In many communication systems, the data in the transmitted signal is separated into chunks called frames.In order to correctly decode the text at the receiver, it is necessary to locate the boundary (the start) of each chunk.This was done by fiat in the receiver of recfilt.m by correctly indexing into the received signal y . Since this starting point will not generally be known beforehand,it must somehow be located. This is an ideal job for correlation and a marker sequence.

The marker is a set of predefined symbols embedded at some specified location within eachframe. The receiver can locate the marker by cross-correlating it with the incoming signal stream.What makes a good marker sequence? This section shows that not all markers are created equally.

Consider the binary data sequence

. . . + 1 , - 1 , + 1 , + 1 , - 1 , - 1 , - 1 , + 1 , M , + 1 , - 1 , + 1 , . . . ,

where the marker M is used to indicate a frame transition. A seven-symbol marker is to be used.Consider two candidates:

  • marker A: 1 , 1 , 1 , 1 , 1 , 1 , 1
  • marker B: 1 , 1 , 1 , - 1 , - 1 , 1 , - 1

The correlation of the signal with each of the markers can be performed as indicated in [link] .

For marker A, correlation corresponds to a simple sum of the last seven values.Starting at the location of the seventh value available to us in the data sequence (two data points before the marker), marker A producesthe sequence

Questions & Answers

I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
what is the stm
Brian Reply
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industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
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What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
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what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
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What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
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Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
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.
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
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Akash Reply
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Smarajit 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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