Faculty of Computer Science & Engineering

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F
ACULTY

OF

C
OMPUTER

S
CIENCE

&
E
NGINEERING

Chapter 03. Spread
Spectrum Technologies

Q
UESTION

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

Q
UESTION

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

Q
UESTION

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

Q
UESTION

4


4. Consider the following two wireless LAN configurations:
System 1. IEEE 802.11 compliant FHSS system, 6 co
-
located 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

Q
UESTION

5


5. Channels on direct sequence systems for
802.11b equipment are ___ MHz wide.


A. 5


B. 20


C. 22


D. 83

Q
UESTION

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

Q
UESTION

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

Q
UESTION

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

Q
UESTION

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

Q
UESTION

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

Q
UESTION

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

Q
UESTION

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

Q
UESTION

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


Q
UESTION

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

Q
UESTION

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

Q
UESTION

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

Q
UESTION

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

Q
UESTION

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

Q
UESTION

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

Q
UESTION

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