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This module shows the results and conclusions for our DMT project.

Results

In order to test our DMT system, we investigated how the probability of bit error changed with the signal-to-noise ratio of the transmitted signal in our channel. In particular, we compared how these PE - SNR curves changed as the cyclic pad length was varied. As a comparison, we also looked at how DMT stacked up with a simple model of single-carrier modulation in these same regards.

Dmt vs single - carrier (sc)

We ran our tests of the system with the following constraints:

  • Bitstream length: 512
  • Block-size: 128 (DMT), 1 (SC)
  • AWGN amplitude: .00001 - 1
  • Channel impulse response length: 1 (wire), 16
  • Cyclic prefix length (DMT): 0, 8, 16
  • Impulse noise: 0
  • Constellation size: 16-point
The results of our tests were as expected. For wire channel, SC and DMT were comparable. They both demonstrated a Q-function behavior, dropping to zero error once the SNR was high enough and leveling off to about 0.5 (i.e. a coin flip) for very low SNR. For impulse response length L less than cyclic prefix C , DMT dropped to a error fell from 0.5 as SNR increased, but leveled off once ISI began to have a more prominent effect. Single-carrier also demonstrated this same behavior, though there was no cyclic prefix involved. This was a little strange, but this project's goal was to study DMT, not SC. Once the cyclic pad length was larger than the impulse response length, DMT again displayed Q-function behavior as ISI was no longer a problem.

L = 1

This is shows how bit error probabilities compare for DMT (red) and SC (blue) with a wire channel impulse response (length L = 1).

L>C

This is shows how bit error probabilities compare for DMT (red) and SC (blue) with a length L = 16 channel impulse response and a DMT cyclic prefix of length C = 8.

L<C

This is shows how bit error probabilities compare for DMT (red) and SC (blue) with a length L = 16 channel impulse response and a DMT cyclic prefix of length C = 16.

Conclusions

From our results and experience implementing our DMT system, we reached the following conclusions:

  • It is possible to implement a working DMT system in MATLAB. It looks as though a more complicated extension of the system, possibly involving variable frequency allocation, a time-varying channel freq. response, more complicated constellations or a transmitter-receiver synchronization process, should also be quite feasible.
  • DMT's advantages over other modulation schemes are difficult to see with such a simple system; they would be more apparent in a system including a more realistic model of data assignment to the various frequencies (instead of evenly distributing all data over the first 256).
  • The need for a cyclic prefix is readily verifiable; as soon as the prefix length is correct, bit error drops to zero at high SNR.
  • Communications engineering and DSP are fun (except when you have to stay up all night writing connexions modules)! Looking forward to 431 next semester!

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Questions & Answers

what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
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
Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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
How can I make nanorobot?
Lily
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
how can I make nanorobot?
Lily
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
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Ece 301 projects fall 2003. OpenStax CNX. Jan 22, 2004 Download for free at http://cnx.org/content/col10223/1.5
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