The following exam is worth 20% of your course grade. It consists of xxx questions, each question's point total is given below. Exam #1 covers material from chapters 1, 2, and 3, of the text, and any material discussed/given/assigned during the course thus far.

1. True or false. (30 points total - two points each). Circle the best answer. If I cannot distinguish your answer, you will not receive the points!

i.	The Open Systems Interconnection (OSI) model consists of seven layers.	True	False
ii.	Four layers of the OSI model deal primarily with network operations	True	False
iii.	Datagrams are better than virtual circuits in dealing with congestion in networks.	True	False
iv.	A store-and-forward network uses message switching.	True	False
v.	Packets are units of a message.	True	False
vi.	Using odd or even parity increases the number of bits transmitted by one.	True	False
vii.	Microwave transmission is a type of satellite transmission.	True	False
viii.	Frequency is inversely related to the amplitude.	True	False
ix.	Analog signals vary continuously.	True	False
x.	Lasers and light emitting diodes (LEDs) are sources of light.	True	False
xi.	A periodic signal is a signal which may change over time.	True	False
xii.	Sputnik traveled in the geosynchronous orbit.	True	False
xiii.	Quadrature Amplitude Modulation (QAM) is a technique wherein a group of bits is assigned a signal defined by its amplitude and phase shift.	True	False
xiv.	In a Huffman code, the characters with the highest frequency have the longest codes.	True	False
xv.	It is impossible to have a collision without contention.	True	False

2. Match the columns. Write the best match (item from right) in the box next to the term on left. (20 points total - two points each.)

 

i.	Digital-to-Analog Conversion	AM
ii.	Analog-to-Digital Conversion	PM
iii.	Period	Frequency
iv.	Transport Layer	Buffering
v.	Multiplexing	Time Division
vi.	Listen to medium protocol	CSMA
vii.	Air medium protocol	Aloha
viii.	Signal value: High = 0, Low = 1	NRZ
ix.	7-bit code	ASCII
x.	Data Link Layer	Error Detection

 

 

 

Aloha Protocol

Amplitude Modulation (AM)

ASCII

Buffering

Carrier Sense Multiple Access

Differential Manchester

EBCDIC

Error Detection

Frequency

Manchester

Non-Return-to-Zero (NRZ)

Pulse Amplitude Modulation (PM)

Routing

Time Division

Wavelength

3. (25 points) What is one problem with world-wide mobile communication and how can it be solved?

Communication frequencies are all different!

Solve by: 1. Change all frequencies to the same, or 2. Handset changes in different geographic areas.

 

4. (5 points) What is the difference between a quantum-bit (qubit) and a binary digit (bit)?

A binary digit has two possibilities, 0 and 1, but not at the same time. A qubit has two states, up and down, or 0 and 1, at the same time.

5. (10 points) Given the following function, draw the signal and show amplitude and period.

 

Amplitude = 4, period = 2p /2 - 4 = p - 4, 1/2 period = p /2 - 4.

Not shown here!

 

6. (10 point) Given a device operating at 125 baud. Give the bit rate if:

1.Binary symbols are used.

Answer:

When two symbols are used, the bit rate and baud rate are the same. That is because:

2 = 2¹, so n = 1 bit/symbol

bit rate = baud rate x n = 125 symbols/sec x 1 bit/symbol = 125 bits/sec = 125 bps

2.Multivalued symbols (16 symbols) are used.

Answer:

When more than two symbols are used, the bit rate and baud rate are the different. For 16 symbols:

16 = 2⁴, so n = 4 bits/symbol

bit rate = baud rate x n = 125 symbols/sec x 4 bits/symbol = 500 bits/sec = 500 bps