As HDTV (high-definition television) was being developed,
the FCC restricted this digital system to use in the samebandwidth (6 MHz) as its analog (AM) counterpart. HDTV
video is sampled on a
raster at 30 images per second for each of the
three colors. The least-acceptable picture received bytelevision sets located at an analog station's broadcast
perimeter has a signal-to-noise ratio of about 10 dB.
Using signal-to-noise ratio as the criterion, how
many bits per sample must be used to guarantee that ahigh-quality picture, which achieves a signal-to-noise
ratio of 20 dB, can be received by any HDTV set withinthe same broadcast region?
Assuming the digital television channel has the same
characteristics as an analog one, how much compressionmust HDTV systems employ?
Digital cellular telephones
In designing a digital version of a wireless telephone, you
must first consider certain fundamentals. First of all, thequality of the received signal, as measured by the
signal-to-noise ratio, must be at least as good as thatprovided by wireline telephones (30 dB) and the message
bandwidth must be the same as wireline telephone. Thesignal-to-noise ratio of the allocated wirelss channel,
which has a 5 kHz bandwidth, measured 100 meters from thetower is 70 dB. The desired range for a cell is 1 km. Can
a digital cellphone system be designed according to thesecriteria?
Optimal ethernet random access protocols
Assume a population of
computers want to transmit information on a random access
channel. The access algorithm works as follows.
Before transmitting, flip a coin that has
probability
of coming up
heads
If only one of the
computer's coins comes up heads, its transmission occurs
successfully, and the others must wait until thattransmission is complete and then resume the
algorithm.
If none or more than one head comes up, the
computers will either
remain silent (no heads) or a collision will occur (morethan one head). This unsuccessful transmission
situation will be detected by all computers once thesignals have propagated the length of the cable, and the
algorithm resumes (return to the beginning).
What is the optimal probability to use for flipping
the coin? In other words, what should
be to maximize the
probability that exactly one computer transmits?
What is the probability of one computer
transmitting when this optimal value of
is used as the number of
computers grows to infinity?
Using this
optimal probability, what is the average number of coinflips that will be necessary to resolve the access so
that one computer successfully transmits?
Evaluate this algorithm. Is it realistic? Is it
efficient?
Repeaters
Because signals
attenuate with distance from the transmitter,
repeaters are frequently employed for both analog
and digital communication. For example, let's assume that thetransmitter and receiver are
m apart, and a repeater is
positioned halfway between them (
[link] ). What the repater does is amplify its
received signal to exactly cancel the attenuationencountered along the first leg and to re-transmit the
signal to the ultimate receiver. However, the signal therepeater receives contains white noise as well as the
transmitted signal. The receiver experiences the same amountof white noise as the repeater.
What is the block diagram for this system?
For an amplitude-modulation communication system, what
is the signal-to-noise ratio of the demodulated signal atthe receiver? Is this better or worse than the
signal-to-noise ratio when no repeater is present?
For digital communication, we must consider the
system's capacity. Is the capacity larger with therepeater system than without it? If so, when; if not, why
not?
Designing a speech communication system
We want to examine both analog and digital communication alternatives for a dedicated speech transmission system.
Assume the speech signal has a 5 kHz bandwidth.The wireless link between transmitter and receiver is such that 200 watts of power can be received at a pre-assigned carrier frequency.
We have some latitude in choosing the transmission bandwidth, but the noise power added by the channel increases with bandwidth with a proportionality constant of 0.1 watt/kHz.
Design an analog system for sending speech under this scenario.
What is the received signal-to-noise ratio under these design constraints?
How many bits must be used in the A/D converter to achieve the same signal-to-noise ratio?
Is the bandwidth required by the digital channel to send the samples without error greater or smaller than the analog bandwidth?
Digital vs. analog
You are the Chairman/Chairwoman of the FCC.
The frequency band 3 MHz to 3.5 MHz has been allocated for a new “high-quality” AM band.Each station licensed for this band will transmit signals having a bandwidth of 10 kHz, twice the message bandwidth of what current stations can send.
How many stations can be allocated to this band and with what carrier frequencies?
Looking ahead, conversion to digital transmission is not far in the future.
The characteristics of the new digital radio system need to be established and you are the boss!Detail the characteristics of the analog-to-digital converter that must be used to prevent aliasing and ensure a signal-to-noise ratio of 25 dB.
Without employing compression, how many digital radio stations could be allocated to the band if each station used BPSK modulation?
Evaluate this design approach.
Questions & Answers
Three charges q_{1}=+3\mu C, q_{2}=+6\mu C and q_{3}=+8\mu C are located at (2,0)m (0,0)m and (0,3) coordinates respectively. Find the magnitude and direction acted upon q_{2} by the two other charges.Draw the correct graphical illustration of the problem above showing the direction of all forces.
To solve this problem, we need to first find the net force acting on charge q_{2}. The magnitude of the force exerted by q_{1} on q_{2} is given by F=\frac{kq_{1}q_{2}}{r^{2}} where k is the Coulomb constant, q_{1} and q_{2} are the charges of the particles, and r is the distance between them.
Muhammed
What is the direction and net electric force on q_{1}= 5µC located at (0,4)r due to charges q_{2}=7mu located at (0,0)m and q_{3}=3\mu C located at (4,0)m?
Capacitor is a separation of opposite charges using an insulator of very small dimension between them. Capacitor is used for allowing an AC (alternating current) to pass while a DC (direct current) is blocked.
Gautam
A motor travelling at 72km/m on sighting a stop sign applying the breaks such that under constant deaccelerate in the meters of 50 metres what is the magnitude of the accelerate
velocity can be 72 km/h in question. 72 km/h=20 m/s, v^2=2.a.x , 20^2=2.a.50, a=4 m/s^2.
Mehmet
A boat travels due east at a speed of 40meter per seconds across a river flowing due south at 30meter per seconds. what is the resultant speed of the boat
which has a higher temperature, 1cup of boiling water or 1teapot of boiling water which can transfer more heat 1cup of boiling water or 1 teapot of boiling water explain your . answer
I believe temperature being an intensive property does not change for any amount of boiling water whereas heat being an extensive property changes with amount/size of the system.
Someone
Scratch that
Someone
temperature for any amount of water to boil at ntp is 100⁰C (it is a state function and and intensive property) and it depends both will give same amount of heat because the surface available for heat transfer is greater in case of the kettle as well as the heat stored in it but if you talk.....
Someone
about the amount of heat stored in the system then in that case since the mass of water in the kettle is greater so more energy is required to raise the temperature b/c more molecules of water are present in the kettle
pratica A on solution of hydro chloric acid,B is a solution containing 0.5000 mole ofsodium chlorid per dm³,put A in the burret and titrate 20.00 or 25.00cm³ portion of B using melting orange as the indicator. record the deside of your burret tabulate the burret reading and calculate the average volume of acid used?
No. According to Isac Newtons law. this two bodies maybe you and the wall beside you.
Attracting depends on the mass och each body and distance between them.
Dlovan
Are you really asking if two bodies have to be charged to be influenced by Coulombs Law?
Specific heat capacity is a measure of the amount of energy required to raise the temperature of a substance by one degree Celsius (or Kelvin). It is measured in Joules per kilogram per degree Celsius (J/kg°C).
AI-Robot
specific heat capacity is the amount of energy needed to raise the temperature of a substance by one degree Celsius or kelvin
ROKEEB
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