# 0.8 Stuff happens  (Page 2/14)

 Page 2 / 14

"Other Impairments: More “What Ifs”" presents a series of “what if” questions concerning the various assumptionsmade in the construction of the ideal system, focusing on performance degradationscaused by synchronization loss and various kinds of distortions:

• What if there is channel noise? (The ideal system is noise free.)
• What if the channel has multipath interference? (There are no reflections or echoes in the ideal system.)
• What if the phase of the oscillator at the transmitter is unknown (or guessed incorrectly) at the receiver? (The ideal systemknows the phase exactly.)
• What if the frequency of the oscillator at the transmitter is off just a bit from its specification? (In the ideal system,the frequency is known exactly.)
• What if the sample instant associated with the arrival of top-dead-center of the leading pulse isinaccurate so that the receiver samples at the “wrong” times? (The sampler in the ideal system is never fooled.)
• What if the number of samples between symbols assumed by the receiver is different from that used at the transmitter? (These are the samein the ideal case.)

These questions are investigated via a series of experiments that require onlymodest modification of the ideal system simulation. These simulations will show (as with the time-varying channel gain)that small violations of the idealized assumptions can often be tolerated.However, as the operational conditions become more severe (as more stuff happens),the receiver must be made more robust.

Of course, it is not possible to fix all these problems in one chapter. That's what the rest of the book is for!

• Chapter [link] deals with methods to acquire and track changes in the carrier phase and frequency.
• Chapter [link] describes better pulse shapes and corresponding receive filters that perform wellin the presence of channel noise.
• Chapter [link] discusses techniques for tracking the symbol clock so that the samples can be taken at the best possibletimes.
• Chapter [link] designs a symbol-spaced filter that undoes multipath interference and can reject certain kinds ofin-band interference.
• Chapter [link] describes simple coding schemes that provide protection against channel noise.

## Simulating the ideal system

The simulation of the digital communication system in [link] divides into two parts just as the figure does.The first part creates the analog transmitted signal, and the second part implements the discrete-time receiver.

The message consists of the character string

01234 I wish I were an Oscar Meyer wiener 56789

In order to transmit this important message, it is first translated into the 4-PAM symbol set $±1,±3$ (which is designated $m\left[i\right]$ for $i=1,2,...,N$ ) using the subroutine letters2pam.m . This can be represented formally asthe analog pulse train ${\sum }_{i=0}^{N-1}m\left[i\right]\delta \left(t-iT\right)$ , where $T$ is the time interval between symbols. The simulation operates with an oversampling factor $M$ , which is the speed at which the “analog” portion of the system evolves.The pulse train enters a filter with pulse shape $p\left(t\right)$ . By the sifting property [link] , the output of the pulse shaping filteris the analog signal ${\sum }_{i=0}^{N-1}m\left[i\right]p\left(t-iT\right)$ , which is then modulated (by multiplication with acosine at the carrier frequency ${f}_{c}$ ) to form the transmitted signal

what is variations in raman spectra for nanomaterials
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
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
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
anyone know any internet site where one can find nanotechnology papers?
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
what does nano mean?
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?
absolutely yes
Daniel
how did you get the value of 2000N.What calculations are needed to arrive at it
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!