# 6.37 Information communication problems  (Page 7/8)

 Page 7 / 8

## Selective error correction

We have found that digital transmission errors occur with a probability that remains constant no matter how "important"the bit may be. For example, in transmitting digitized signals, errors occur as frequently for the most significantbit as they do for the least significant bit. Yet, the former errors have a much larger impact on the overallsignal-to-noise ratio than the latter. Rather than applying error correction to each sample value, why not concentratethe error correction on the most important bits? Assume that we sample an 8 kHz signal with an 8-bit A/D converter.We use single-bit error correction on the most significant four bits and none on the least significant four. Bits aretransmitted using a modulated BPSK signal set over an additive white noise channel.

1. How many error correction bits must be added to provide single-bit error correction on the mostsignificant bits?
2. How large must the signal-to-noise ratio of the received signal be to insure reliablecommunication?
3. Assume that once error correction is applied, only the least significant 4 bits can be received in error.How much would the output signal-to-noise ratio improve using this error correction scheme?

## Compact disk

Errors occur in reading audio compact disks. Very few errors are due to noise in the compact disk player; mostoccur because of dust and scratches on the disk surface. Because scratches span several bits, a single-bit error israre; several consecutive bits in error are much more common. Assume that scratch and dust-inducederrors are four or fewer consecutive bits long. The audio CD standard requires 16-bit, 44.1 kHz analog-to-digitalconversion of each channel of the stereo analog signal.

1. How many error-correction bits are required to correct scratch-induced errors for each 16-bitsample?
2. Rather than use a code that can correct several errors in a codeword, a clever 241 engineer proposes interleaving consecutive coded samples. As the cartoon shows, the bits representing coded samples are interpersed before they are written onthe CD. The CD player de-interleaves the coded data, then performs error-correction. Now, evaluate thisproposed scheme with respect to the non-interleaved one.

## Communication system design

RU Communication Systems has been asked to design a communication system that meets the following requirements.

• The baseband message signal has a bandwidth of 10 kHz.
• The RUCS engineers find that the entropy $H$ of the sampled message signal depends on how many bits $b$ are used in the A/D converter (see table below).
• The signal is to be sent through a noisy channel having a bandwidth of 25 kHz channel centered at 2 MHzand a signal-to-noise ration within that band of 10 dB.
• Once received, the message signal must have a signal-to-noise ratio of at least 20 dB.

b H
3 2.19
4 3.25
5 4.28
6 5.35

where we get a research paper on Nano chemistry....?
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
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
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
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
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?
what is a peer
What is meant by 'nano scale'?
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 ?
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?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe