# A digital radio

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Though far from optimal, the receiver that you will build contains all the elements of a fully functional receiver.It provides a simple way to ask and answer what if questions. What if there is noise in the system? What if the modulation frequencies are not exactly as specified?What if there are errors in the received digits? What if the data rate is not high enough?What if there are distortion, reflections, or echoes in the transmission channel? What if the receiver is moving?

The first layer of the Software Receiver Design onion begins with a sketch of a digital radio.

## An illustrative design

The first design is a brief tour of the outer layer of the onion. If some of the terminologyseems obscure or unfamiliar, rest assured that succeeding sections and chapters will revisit the words and refine theideas. The design is shown in [link] through [link] . While talking about these figures, it will become clear that some ideas are being oversimplified.Eventually, it will be necessary to come back and examine thesemore closely.

The shaded notes are reminders to return and think about these areas moredeeply later on.

In keeping with Shannon's goal of reproducing at one pointa message known at another point, suppose that it is desired to transmit a text message from one place to another.Of course, there is nothing magical about text; however, .mp3 sound files, .jpg photos, snippets of speech,raster scanned television images, or any other kind of information would do, as long as it can be appropriately digitizedinto ones and zeros.

Can every kind of message be digitized into ones and zeros?

Perhaps the simplest possible scheme would be to transmit a pulse to represent a one and to transmit nothingto represent a zero. With this scheme, however, it is hard to tell the difference betweena string of zeroes and no transmission at all. A common remedy is to send a pulse with a positive amplitude to represent a oneand a pulse of the same shape, but negative amplitude to represent a zero.In fact, if the receiver could distinguish pulses of different sizes, then it would be possible to send two bits with each symbol,for example, by associating the amplitudes Many such choices are possible. These particular values were chosen becausethey are equidistant and so noise would be no more likely to flip a 3 into a 1 than to flip a1 into a $-1$ . of $+1$ , $-1$ , $+3$ and $-3$ with the four choices 10, 01, 11, and 00.The four symbols $±1$ , $±3$ are called the alphabet , and the conversion from the original message (the text) into thesymbol alphabet is accomplished by the coder in the transmitter diagram [link] . The first few letters, the standard ASCII (binary) representationof these letters, and their coding into symbols are:

$\begin{array}{ccc}\text{letter}\phantom{\rule{4.pt}{0ex}}& \text{binary ASCII code}& \phantom{\rule{4.pt}{0ex}}\text{symbol string}\phantom{\rule{4.pt}{0ex}}\\ a& \text{01 10 00 01}& -1,\phantom{\rule{4pt}{0ex}}1,\phantom{\rule{4pt}{0ex}}-3,\phantom{\rule{4pt}{0ex}}-1\\ b& \text{01 10 00 10}& -1,\phantom{\rule{4pt}{0ex}}1,\phantom{\rule{4pt}{0ex}}-3,\phantom{\rule{4pt}{0ex}}-1\\ c& \text{01 10 00 11}& -1,\phantom{\rule{4pt}{0ex}}1,\phantom{\rule{4pt}{0ex}}-3,\phantom{\rule{4pt}{0ex}}3\\ d& \text{01 10 01 00}& -1,\phantom{\rule{4pt}{0ex}}1,\phantom{\rule{4pt}{0ex}}-1,\phantom{\rule{4pt}{0ex}}-3\\ ⋮& ⋮& \phantom{\rule{4pt}{0ex}}⋮\end{array}$

In this example, the symbols are clustered into groups of four, and each cluster is called a frame.Coding schemes can be designed to increase the security of a transmission, to minimize the errors, or to maximizethe rate at which data are sent. This particular scheme is not optimized in any of these senses, but it isconvenient to use in simulation studies.

#### Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
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.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
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
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
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
how did you get the value of 2000N.What calculations are needed to arrive at it
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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 By OpenStax By OpenStax By Brooke Delaney By Richley Crapo By Rachel Carlisle By John Gabrieli By Mahee Boo By OpenStax By Mucho Mizinduko By Michael Sag