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Our goal in digital communications was to transmit a grayscale image shown below:

This image was represented as a matrix with dimensions 512x512 with each entry having values from 0 to 255. The values from 0 to 255 in each entry of the matrix were taken, converted into a string of 0s and 1s and fed in four bits at a time into the 16 QAM modulator. This was then passed through a noisy channel which added an error of random numbers between -2.5 to 2.5 to the transmitted signal. The receiver collected the received signal, demodulated it and reconstructed the received image with noise. This was done with a raised cosine filter, a Butterworth filter and with no filter at all. We also compared the bit error with the original image for the raised cosine filter and the Butterworth filter. Below is the image received with noise using a raised cosine filter in the modulation phase:

Using the Butterworth filter in the modulation phase the received image with noise was:

Using no filter at all during the modulation scheme the received image was:

Error calculations and filter evaluations

The bit error was calculated by analyzing the bit-representation of the original grayscale image and comparing it the bit-representation of the received image. The percentage of incorrect bits was calculated to be 34.55% when using the raised cosine filter, and 34.45% when using the Butterworth filter. From these results we can see that the performance of the Butterworth filter and the raised cosine filter are about the same, with the Butterworth filter performing slightly better. The bit error in the received image using no filter was 47%, however, percent error for the number of incorrect grayscale pixels was calculated to be 99%. The percent error for the number of incorrect grayscale pixels using the Butterworth filter was 95.64%. The percent error for the number of incorrect grayscale pixels using the raised cosine filter was 95.66%. This is high because this includes even the slightest error which might be indistinguishable to the human eye.

We can also see the importance of using filters in the upsampling stage of the modulation phase of the digital communication scheme by looking at the received image without the use of a filter. The use of a digital filter allows the image to be recovered with far greater accuracy.

Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
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
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
characteristics of micro business
for teaching engĺish at school how nano technology help us
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
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
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.
what is the actual application of fullerenes nowadays?
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.
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.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
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.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Digital filters in 16-qam communication. OpenStax CNX. Dec 11, 2011 Download for free at http://cnx.org/content/col11384/1.1
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