TDC 460
Take-Home Midterm Exam
Summer I 2008
Due: Tuesday July 8th at 6:00pm CDT
1. Given the three types of fiber - graded index multimode, step index multimode, and single
mode - rank them from fastest to slowest. What makes one faster than another?
2. Using twisted pair wiring, list the different techniques / technologies / protocols / anything that
can be used to increase the data transmission speed over that wiring.
3. For each of the following functions, list the Internet layer (TCP/IP protocol suite) that
normally performs that function:
This layer is encapsulated over the network layer:
TCP is performed at this layer:
The top-most layer:
IP is performed at this layer:
error detection is performed at this layer:
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4a. What is the primary advantage of using a Manchester encoding technique?
b. Primary disadvantage?
c. What is the primary advantage of using an NRZ scheme?
d. Primary disadvantage?
e. What is the primary advantage of using B8ZS?
f. What is the primary advantage of using 4B/5B?
g. What is the disadvantage?
5. Show the constellation for a modem that has a phase change every 45 degrees (starting at 0
degrees) with two amplitudes on 0, 90, 180, and 270 degrees and one amplitude elsewhere.
6. What frequency signal do you need if you want to transmit at 56,000 bps with a signal to noise
ratio of 700 to 1?
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7. How many signal levels are necessary to support a noiseless connection at 128 kbps using a
6000Hz signal?
8. Using Shannon’s equation, what is the data rate (bps) if a signal has a bandwidth of 22,000 Hz
and the signal to noise ratio is 60 dB?
9. You are given an analog signal with a frequency range of 20,000 - 50,000 Hz. You want to
perform pulse code modulation on this signal using 8-bit A/D conversion. How many bits will
be generated in 1 second? How many quantization levels will be required?
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10. Given a periodic composite signal composed of 4 individual frequencies: 1000Hz at 5v,
3000Hz at 8v, 5000Hz at 10v, and 7000hz at 6v, draw the frequency domain representation for
this composite. Also include a DC component of 10v.
11. What is the required bandwidth for FSK with 2Df = 3kHz and for 64-QAM if we need to
send 56 kbps? Assume d = 1 for the FSK and d = 0 for the 64-QAM.
12. Given the 7-bit character 1010011, generate the 11-bit Hamming code.
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13. The following 11-bit Hamming-coded (single-bit correction) string was received. What
ASCII-coded letter does it represent? (Just show the remaining 7 data bits.)
10101011110
14. Compress the following bit sequence using run-length encoding:
110000000010000000000111000000000000000000100000010000000
15. Given the generating polynomial x6 + x3 + x2 + 1 and the data 10101010, show the remainder
that is the result from calculating the cyclic redundancy checksum.
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