Deck 4: IEEE 80211 Physical Layer Standards

Question 1

Increasing the speed of the WLAN will cause shorter delays in waiting for reflections.

Answer 1

False

Question 2

____ is not part of a frame.

A) Length
B) Parity
C) Channel
D) Data

Answer 2

C

Question 3

When transmitting with FHSS, if interference is encountered on a particular frequency then that part of the signal will be retransmitted on the previous frequency of the hopping code.

Answer 3

False

Question 4

What is a disadvantage of narrowband transmissions?

A) requires a complicated algorithm
B) not well regulated
C) expensive to implement
D) interference from another radio signal

Question 5

Into which layers are WLAN features isolated by IEEE standards?

A) PHY and PMD
B) MAX and PLCP
C) PHY and MAC
D) PMD and PLCP

Question 6

How does OFDM work?

A) signals are broken up and the parts are sent in parallel
B) the same signal is sent on multiple channels
C) one signal is sent twice on the same channel
D) a signal is sent over a wired network at the same time as the wireless network

Question 7

The value of layers in the OSI reference model is that it divides networking into a series of tasks, and then illustrates how those tasks relate to each other.

Question 8

According to FCC regulations, all FHSS systems in the 900 MHz band must change frequencies through 50 channels and cannot spend more than ____ on one frequency each 20 seconds.

A) 20 milliseconds
B) 30 milliseconds
C) 400 milliseconds
D) 1 second

Question 9

Because wireless technology has advanced at such a rapid pace, the earliest WLANs are now essentially obsolete.

Question 10

____ signals by nature transmit on only one frequency or a very narrow portion of the frequencies.

A) Broadband
B) Computer
C) Radio
D) Heat

Question 11

Because a device must wait to transmit until it receives the last reflected signal, this in effect puts a ceiling limit on the overall speed of the WLAN. What is the current ceiling for WLAN speed?

A) under 10 Mbps
B) between 10 and 20 Mbps
C) between 20 and 30 Mbps
D) over 50 Mbps

Question 12

Which system is preferred for 802.11b WLANs?

A) DSSS
B) FHSS
C) OFDM
D) All are equally preferred

Question 13

In FHSS, the amount of time needed to move from one frequency to another is the ____ time.

A) dwell
B) switch
C) lift
D) hop

Question 14

DSSS uses a bit pattern called a ____ code.

A) hopping
B) setting
C) dwelling
D) chipping

Question 15

Bluetooth divides the 2.4 GHz frequency into ____ different frequencies spaced 1 GHz apart.

A) 52
B) 68
C) 79
D) 93

Question 16

Which layer of the OSI reference model permits the devices on the network to hold ongoing communications across the network?

A) presentation
B) session
C) transport
D) network

Question 17

When was the concept used by FHSS technology developed?

A) during World War I
B) during World War II
C) in the 1960s
D) in the 1980s

Question 18

Of the 52 subchannels, 32 are used for standard transmissions and 20 are used for FEC transmissions.

Question 19

What is the top layer of the OSI reference model?

A) application
B) presentation
C) physical
D) transport

Question 20

IEEE has divided the ____ layer into two sublayers: Logical Link Control (LLC) and Media Access Control (MAC).

A) Physical
B) Data Link
C) Transport
D) Session

Question 21

The amount of time that a transmission occurs on a specific frequency is called the ____________________ time.

Question 22

Narrowband transmissions require significant power for the signal to be transmitted because the signal must exceed the ____________________, or the total amount of outside interference, by a substantial margin.

Question 23

The ____ coding technique consists of a set of 64 8-bit code words.

A) chipping
B) fixed scramble
C) Barker
D) complementary code keying

Question 24

The Physical Layer Convergence Procedure (PLCP) standards for 802.11b are based on ____.

A) DSSS
B) FHSS
C) OFDM
D) PYS

Question 25

What are the advantages to using DSSS with a chipping code?

Question 26

Users can upgrade from an 802.11b network to a faster 802.11g network simply by replacing the ____________________.

Question 27

What is the Open Systems Interconnection (OSI) reference model?

Question 28

Although 54 Mbps is the "official" top speed of 802.11a, the IEEE specification also allows for higher speeds. These higher speeds are known as ____________________ mode or 2X mode.

Question 29

The 802.11b standard specifies ____ frequencies that can be used, beginning at 2.412 GHz.

A) 4
B) 10
C) 14
D) 30

Question 30

There are two disadvantages to using U-NII. What are they?

Question 31

What is a disadvantage of narrowband transmissions?

Question 32

What are the fields that make up a PLCP frame?

Question 33

The _________________________ Protocol defines a set of specifications for wireless data and voice communications around the home.

Question 34

When using the Shared Wireless Access Protocol, devices can be as far as 45 meters (150 feet) apart and can send and receive data at rates up to ____ Mbps.

A) 2
B) 5
C) 10
D) 14

Question 35

What techniques are used by vendors to achieve 2x mode for transmissions?

A) combine two frequency channels
B) use different coding rate schemes
C) reallocating the individual carriers
D) All of the above

Question 36

How does OFDM avoid problems caused by multipath distortion?

Question 37

The modulation techniques used to encode the 802.11a data vary depending upon the speed. Describe the techniques used to transmit at 24 Mbps.

Question 38

The ____ field of an 802.11a frame consists of 10 repetitions of a short training sequence signal and two repetitions of a long training sequence signal.

A) Rate
B) Service
C) Synchronization
D) Parity

Question 39

Describe the FCC restrictions on FHSS.

Question 40

What are disadvantages of the 802.11g standard?

Question 41

The 802.11g standard outlines two mandatory modes along with one optional mode. Describe each mode.