Faculty of Computer Science & Engineering

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FACULTY OF
COMPUTER SCIENCE &
ENGINEERING
Chapter 03. Spread
Spectrum Technologies
QUESTION 1

1. Increasing the dwell time for an FHSS system
will increase the throughput.

A. This statement is always true

B. This statement is always false

C. It depends on the manufacturer of the equipment
QUESTION 2

2. Which one of the following dwell times will
result in the greatest throughput in a FHSS
system and will still be within FCC regulations?

A. 100 ms

B. 200 ms

C. 300 ms

D. 400 ms
QUESTION 3

3. An 802.11b compliant wireless LAN
configuration using DSSS can have a maximum
of ___ non-overlapping, co-located access points.

A. 3

B. 15

C. 26

D. 79
QUESTION 4

4. Consider the following two wireless LAN configurations:
System 1. IEEE 802.11 compliant FHSS system, 6 colocated access points running at maximum data rate.

System 2. IEEE 802.11b compliant DSSS system, 3 co-
located access points running at 50% of maximum data
rate.

Which one of the following statements is true?

A. System 1 will have more throughput

B. System 2 will have more throughput

C. System 1 and System 2 will have the same throughput
QUESTION 5

5. Channels on direct sequence systems for
802.11b equipment are ___ MHz wide.

A. 5

B. 20

C. 22

D. 83
QUESTION 6

6. Which of the following are advantages of
802.11b DSSS over 802.11 FHSS?

Choose all that apply.

A. Cost

B. Throughput

C. Security

D. Resistance to narrowband interference
QUESTION 7

7. If having compatible equipment from different
manufactures were an important factor when
purchasing wireless LAN equipment, which of
the following spread spectrum technologies would
be the best choice?

A. FHSS

B. DSSS
QUESTION 8

8. The FCC has two sets of rules regarding FHSS
that are known as before and after which of the
following dates?

A. 06/30/2000

B. 08/31/1999

C. 08/31/2000

D. 08/31/2001
QUESTION 9

9. The latest published FCC rules regarding
power output for FHSS states a maximum output
of which one of the following?

A. 100 mW

B. 125 mW

C. 200 mW

D. 1 W
QUESTION 10

10. The FCC specifies how many channels in the
2.4 GHz ISM band that can be used for DSSS in
the United States?

A. 3

B. 6

C. 9

D. 11
QUESTION 11

11. You have been hired on as a consultant to increase the
capacity of an existing wireless LAN based on FHSS
technology.
After
your
research
is
completed
you
recommend that a replacement system based on DSSS
would be better. Which of the following could be your
arguments to defend your position? Choose all that apply.

A. The DSSS devices will cost less and have more throughput

B. The DSSS devices will cost more but have more throughput

C. Additional new FHSS devices may not be compatible with
the older devices

D. DSSS is more secure than FHSS
QUESTION 12

12. The statement, “802.11b wireless LAN
devices are backward compatible with 802.11
wireless LAN devices” is:

A. Always true

B. Always false

C. Sometimes true
QUESTION 13

13. What is considered to be the maximum
number of co-located FHSS access points in a
wireless LAN, if non-synchronized radios are to
be used?

A. 3

B. 16

C. 20

D. 26
QUESTION 14

14. In Frequency Hopping wireless LAN systems, the
term hopping refers to which one of the following?

A. Switching between throughput speeds from 11 Mbps to
5.5 Mbps

B. What happens when the carrier frequency is changed

C. The change that occurs as a result of the RF signal
getting weaker

D. Changing technologies from FHSS to DSSS
QUESTION 15

15. A DSSS channel is more susceptible to narrowband
interference than a FHSS channel because of which of the
following? Choose all that apply.

A. The DSSS channel is much smaller (22 MHz wide instead of the 79
MHz wide band used by FHSS)

B. The information is transmitted along the entire band
simultaneously instead of one frequency at a time

C. FHSS systems simply avoid the frequency on which the
narrowband interference is located

D. FHSS systems only use one frequency at a time, so the narrowband
interference must be on the same exact frequency at the same time
QUESTION 16

16. The noise floor is defined by which one of the
following?

A. The general level of RF noise in the environment
around the wireless LAN

B. The noise that is generated as a result of foot
traffic

C. A fixed level of -100 dBm

D. The level of noise at which a wireless LAN starts
working
QUESTION 17

17. Which one of the following is not described by
the IEEE and OpenAir standards regarding
FHSS systems?

A. What frequency bands may be used

B. Hop sequences

C. Allowable levels of interference

D. Dwell times

E. Data rates
QUESTION 18

18. An RF signal is considered spread spectrum when
which of the following are true?

Choose all that apply.

A. The system sending the signal is using infrared
technology

B. The power required to send the information is
significantly greater than is necessary

C. The bandwidth used is much wider than what is
required to send the information

D. The bandwidth used is much less than what is used to
send the information
QUESTION 19

19. Some 2.4 GHz FHSS systems operate at 3
Mbps or more. Which of the following is true
regarding these systems?

A. They are always IEEE 802.11 compliant

B. They may not interoperate with other FHSS
systems

C. They are always OpenAir compliant

D. They are backwards compatible with 900 MHz
systems
QUESTION 20

20. How many different types of implementations
of spread spectrum technology does the FCC
specify for the 2.4 GHz ISM band?

A. 1

B. 2

C. 3

D. 4
The
END
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