# 0.8 Stuff happens  (Page 2/14)

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"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

find the 15th term of the geometric sequince whose first is 18 and last term of 387
I know this work
salma
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
hmm well what is the answer
Abhi
how do they get the third part x = (32)5/4
can someone help me with some logarithmic and exponential equations.
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
hmm
Abhi
is it a question of log
Abhi
🤔.
Abhi
I rally confuse this number And equations too I need exactly help
salma
But this is not salma it's Faiza live in lousvile Ky I garbage this so I am going collage with JCTC that the of the collage thank you my friends
salma
Commplementary angles
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
hii
Uday
hi
salma
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
a perfect square v²+2v+_
kkk nice
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
rolling four fair dice and getting an even number an all four dice
Kristine 2*2*2=8
Differences Between Laspeyres and Paasche Indices
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
how do you translate this in Algebraic Expressions
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
what's the easiest and fastest way to the synthesize AgNP?
China
Cied
types of nano material
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.
what is nano technology
what is system testing?
preparation of nanomaterial
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
what is system testing
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
how did you get the value of 2000N.What calculations are needed to arrive at it
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