Deck 5: Physical Layer Standards

Question 1

Which is true about the 802.11a,802.11b,802.11g,and 802.11n standards?

A) 802.11a and 802.11g use the 5 GHz band
B) 802.11b and 802.11g use the 2.4 GHz band
C) 802.11a and 802.11b operate at up to 11 Mbps
D) 802.11b and 802.11n operate at up to 54 Mbps

Answer 1

B

Question 2

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

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

Answer 2

A

Question 3

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

Answer 3

D

Question 4

DSSS uses a bit pattern called a ____ code to transmit bits.

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

Question 5

Which of the following is true about the frequencies 802.11b uses?

A) 28 total,22 used in Japan and China
B) 14 total,only 11 used in the U.S.
C) 22 total,only 14 used in Europe
D) 52 total,48 usable

Question 6

A 1 Mbps transmission rate is achieved by sending a single symbol every microsecond.

Question 7

Which sublayer of the Physical layer reformats data received from the MAC layer when transmitting?

A) PMD
B) LLC
C) Data Link
D) PLCP

Question 8

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 9

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 10

Which type of RF signal uses only a single frequency for transmission?

A) broadband
B) narrowband
C) spread-spectrum
D) orthogonal frequency

Question 11

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 12

The 802.11a standard enables faster data rates than 802.11b due to which of the following?

A) lower frequencies and decreased power
B) lower frequencies and increased power
C) higher frequencies and increased power
D) decreased power but higher frequencies

Question 13

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 14

Because of the relatively high speeds achieved with FHSS,it is widely implemented in WLAN systems.

Question 15

Which OSI model layer picks the route packets take?

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

Question 16

Which system is preferred for 802.11 WLANs that operate at speeds in excess of 11 Mbps?

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

Question 17

The purpose of the 802.11 PHY layer is to format packets to be received by the corresponding network protocol on the receiving device.

Question 18

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 19

DSSS makes it possible to share the frequency with similar devices by assigning each device a unique chipping code,a function known as what?

A) chipping variation
B) colocation
C) multiplexing
D) intersymbol assignment

Question 20

OFDM sends the transmission in parallel across several channels.

Question 21

At which layers of the OSI model do 802.11 wireless LANs function? (Choose all that apply.)

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

Question 22

A numeric value called a ____________ is assigned to a frequency range since using frequency range values can become tedious.

Question 23

What are the two sublayers that the OSI Physical layer is broken into with the IEEE model?

Question 24

Which of the following are advantages of spread-spectrum versus narrowband transmissions? (Choose all that apply.)

A) resistance to outside interference
B) efficiency due to limited spectrum use
C) lower power requirements
D) increased security

Question 25

From top to bottom,list the 7 layers of the OSI model.

Question 26

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 27

With FHSS,the sequence of changing frequencies is called the ___________ code.

Question 28

A frame is made up of which parts? (Choose all that apply.)

A) segment
B) preamble
C) data
D) header

Question 29

What are the two basic concepts involved with OFDM?

Question 30

What is the modulation type and DSSS coding technique used by 802.11b transmitting at 11 Mbps?

Question 31

What is a disadvantage of narrowband transmissions?

Question 32

What are two safeguards used by 802.11n that can protect against interference caused by channel bonding? (Choose two.)

A) convolutional coding rate
B) Dynamic Frequency Selection
C) Phased Coexistence Operation
D) variable guard interval

Question 33

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

Question 34

List four advantages to using DSSS?

Question 35

Name and describe the fields that make up a PLCP frame?

Question 36

Which of the following are enhancements of the 802.11n standard?

A) 40 MHz channels and variable guard interval
B) 20 MHz channels and fixed guard interval
C) bonding of two 10 MHz channels
D) operation in the 40 GHz frequency range

Question 37

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

A) combining frequency channels
B) using different coding rate schemes
C) increasing and reallocating the individual carriers
D) All of the above

Question 38

The 40 MHz channels in an 802.11n WLAN are actually two 20 MHz channels that are __________ together.

Question 39

List three advantages of spread-spectrum transmissions over narrowband transmissions.

Question 40

Describe how 802.11n uses the primary and secondary channel.

Question 41

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