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This module presents introductory material on data communication, focusing on a high-level summary/comparison of analog and digital communication.

Goal: Transmit a message from one location to another.

When message is a...
continuous waveform, use analog comm (e.g., FM radio),
sequence of numbers, use digital comm (e.g., mp3 file),
but keep in mind that the sequence of numbers might represent a sampling of a continuous waveform (as in the case of digital audio).

Typical communication media:

twisted pair wire (e.g., telephone A )
coaxial cable (e.g., TV A , D , data D )
fiber optic cable (e.g., ethernet D )
EM waves (e.g., cellular phones A , D , WiFi D , TV A , D )
water waves (e.g., underwater network A , D )
power lines A , D
compact disc D
hard drive D
magnetic tape A , D

where A = analog and D = digital.

Note that, whether the message signal is discrete-time or continuous-time, the transmitted signal is continuous-time!

Analog communication

This is a flowchart with movement to the right. It begins with an arrow moving to the right, labeled analog message. The arrow points at a box labeled modulator. To the right of the box is another arrow pointing to the right, labeled transmitted message. This arrow points at a box labeled channel. To the right of the channel box is an arrow pointing to the right, labeled received signal. To the right of this arrow is a box labeled de-modulator. Following this is a final arrow, pointing to the right, labeled recovered message. This is a flowchart with movement to the right. It begins with an arrow moving to the right, labeled analog message. The arrow points at a box labeled modulator. To the right of the box is another arrow pointing to the right, labeled transmitted message. This arrow points at a box labeled channel. To the right of the channel box is an arrow pointing to the right, labeled received signal. To the right of this arrow is a box labeled de-modulator. Following this is a final arrow, pointing to the right, labeled recovered message.
  • Perfect recovery is impossible in the presence of noise!

Digital communication

This is a long flowchart moving to the right, with labeled arrows pointing at  boxes to their right. The first arrow is labeled binary message, with the label below, ... 010110 .... This is followed by a box labeled coder/mapper. To the right of this is an arrow labeled symbol sequence, ... 3, -1, 1, -3 ... After this is a box labeled pulse shaper. To the right of this is an arrow labeled baseband message, with a small graph showing a wave and a half. This arrow points at a box labeled modulator. To the right of this is an arrow labeled passband message. This arrow points at a box labeled channel. to the right of this is an arrow labeled received passband. This points at a box labeled demodulator. To the right of the box is an arrow labeled received baseband. This points at a box labeled sampler. To the right of the sampler box is an arrow labeled received sequence. This arrow points at a box labeled equalizer. To the right of this box is an arrow labeled equalized sequence, with a numbered sequence below, ... 3.1, -0.9, 1.1, -2.9 ... This arrow points at a box labeled de-mapper/decoder. To the right of this is a final arrow labeled recoevered message ... 010110 ... This is a long flowchart moving to the right, with labeled arrows pointing at  boxes to their right. The first arrow is labeled binary message, with the label below, ... 010110 .... This is followed by a box labeled coder/mapper. To the right of this is an arrow labeled symbol sequence, ... 3, -1, 1, -3 ... After this is a box labeled pulse shaper. To the right of this is an arrow labeled baseband message, with a small graph showing a wave and a half. This arrow points at a box labeled modulator. To the right of this is an arrow labeled passband message. This arrow points at a box labeled channel. to the right of this is an arrow labeled received passband. This points at a box labeled demodulator. To the right of the box is an arrow labeled received baseband. This points at a box labeled sampler. To the right of the sampler box is an arrow labeled received sequence. This arrow points at a box labeled equalizer. To the right of this box is an arrow labeled equalized sequence, with a numbered sequence below, ... 3.1, -0.9, 1.1, -2.9 ... This arrow points at a box labeled de-mapper/decoder. To the right of this is a final arrow labeled recoevered message ... 010110 ...
  • A digital message is converted to an analog message coding and pulse-shaping, and then transmitted usinganalog modulation. To recover the message, the received signal is demodulated, sampled, and digitally processed.
  • Perfect recovery is possible even in the presence of noise!

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, Introduction to analog and digital communications. OpenStax CNX. Sep 14, 2009 Download for free at http://cnx.org/content/col10968/1.2
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