Homework 2 is to be done on your own.
This homework is divided into two sections. Part A must be
word-processed. Use good writing skills in your answer. Part B may be
handwritten in your best handwriting. If it cannot be read
it will not be graded. Be sure to show your work for
full credit. Point values are estimated and may change up or down by
a point or so at the time of grading. This homework is due at the
start of class on Friday, February 25.
(15 points) Read the Southwestern Bell Internet at Home
products pages, including the current information about dialup access,
Internet access services. For each of the three services, answer
the following questions:
for the time being any other prices or services that may be
available from Southwestern Bell or another provider,
if you were going to purchase one of these Internet access
services from Southwestern Bell, which of them would you
Justify your answer with both technical and cost
arguments. (For example, don't just say "I want the fastest and so
I'll get XXX.") Explain your choice on the basis of the cost, the
expected performance of the service, and your expected
- Is the data sent using a digital or analog signal? Include
in your answer a basic description of how the signal is encoded.
- What is the basic data rate? Is the rate the same in both
- Will you need a separate phone line for voice with this
service (and under what circumstances might you not) ?
- Are there extra features provided that you would find useful?
- Not including setup fees, what is the best price per month
that you can get for each service from Southwestern Bell? Be sure
to note if this price includes unlimited access or not.
- (3 points) Consider a LAN with a maximum distance of 2 km. At
what bandwidth would propagation delay (at a speed of 200m/usec) equal
transmit delay of 100-byte packets?
- (2 points) A noiseless 6-kHz channel is sampled every
1msec. What is the maximum data rate?
- (3 points) If a binary signal is sent over a 5Khz channel whose signal to
noise ratio is 25dB, what is the maximum achievable data rate?
- (2 points) What is the difference between a passive star and an
active repeater in a fiber optic network?
- (2 points) Is the Nyquist theorem true for optical fiber, or only
for copper wire?
- (2 points) Suppose that a signal is received at 90% of its original
transmitted power. What is its attenuation in decibels?
- (3 points) Radio antennas often work best when the diameter of the antenna
is equal to the wavelength of the radio wave. Reasonable antenna
range from 1 cm to 5 meters in diameter. What frequency range does
- (4 points) Some cable channels used for distributing multimedia to homes
will be modulated using quadrature amplitude modulation.
Suppose that the bandwidth supplied is 48Mbps
over a 6MHz channel. What is the number of points
in the constellation diagram for QAM? Draw a sample QAM
constellation pattern (that you make up).
- (3 points) What is the percent overhead on a T1 carrier. That
is, what percent of the 1.544 Mbps are not delivered to the end
- (2 points) If the bit string
0 1 1 1 1 1 1 0 0 1 1 1 1 1 0 1 1 1 1 0
is bit stuffed, what is the output string?
- (3 points) What is the remainder obtained by dividing
x7 + x5 + 1 by the generator polynomial
x3 + 1 ?
- (4 points) A channel has a bit rate of 4Kbps and a propagation delay of
20msec. For what range of frame sizes does stop-and-wait give an
efficiency of at least 50 percent?
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