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Our presentation focuses on solving problems using simple recursive (gradient)methods. Once the synchronization problems are correctly stated, techniques for their solution becomeobvious. With the exception of frame synchronization (which is approached via correlational methods)the problem of designing synchronizers is unified via one simple concept, that of the minimization (or maximization)of an appropriate performance function. [link] , [link] , and [link] contain details.

Equalization

When all is well in the digital receiver, there is no interaction between adjacent data values and allfrequencies are treated equally. In most real wireless systems (and many wired systems as well),however, the transmission channel causes multiple copies of the transmitted symbols, each scaled differently,to arrive at the receiver at different times. This intersymbol interference can garble the data. The channel may also attenuate different frequencies bydifferent amounts. Thus frequency selectivity can render the data indecipherable.

The solution to both of these problems is to build a filter in the receiver thatattempts to undo the effects of the channel. This filter, called an equalizer , cannot be fixed in advance by the system designer,however, because it must be different to compensate for different channel paths that are encountered when thesystem is operating. The problem of equalizer design can be stated as a simple optimization problem, that offinding a set of filter parameters to minimize an appropriate function of the error, given only the received data(and perhaps a training sequence). This problem is investigated in detail in Chapter [link] , where the same kinds of adaptive techniques used to solve the synchronization problemscan also be applied to solve the equalization problem.

Decisions and error measures

In analog systems, the transmitted waveform can attain any value, but in a digital implementationthe transmitted message must be one of a small number of values defined by the symbol alphabet.Consequently, the received waveform in an analog system can attain any value, but in a digital implementationthe recovered message is meant to be one of a small number of values from the source alphabet.Thus, when a signal is demodulated to a symbol and it is not amember of the alphabet, the difference between the demodulated value (called a soft decision) and the nearest element of the alphabet (the hard decision) can provide valuable information about the performance of thesystem.

To be concrete, label the signals at various points as shown in [link] :

  • The binary input message b ( · ) .
  • The coded signal w ( · ) is a discrete-time sequence drawn from a finite alphabet.
  • The signal m ( · ) at the output of the filter and equalizer is continuous valuedat discrete times.
  • Q { m ( · ) } is a version of m ( · ) that is quantized to the nearest member of the alphabet.
  • The decoded signal b ^ ( · ) is the final (binary) output of the receiver.

If all goes well and the message is transmitted, received, and decoded successfully,then the output should be the same as the input, although there may be some delay δ between the time of transmission and the time when theoutput is available. When the output differs from the message, then errors have occurred during transmission.

Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
Aislinn Reply
cm
tijani
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John Reply
what is physics
Siyaka Reply
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Jude Reply
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
David Reply
what is viscosity?
David
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emma Reply
what is chemistry
Youesf Reply
what is inorganic
emma
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
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Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
Krampah Reply
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
Sahid Reply
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
Samuel Reply
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Joseph Reply
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
Ryan
what's motion
Maurice Reply
what are the types of wave
Maurice
answer
Magreth
progressive wave
Magreth
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Muhammad Reply
fine, how about you?
Mohammed
hi
Mujahid
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
yasuo Reply
Who can show me the full solution in this problem?
Reofrir 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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