Cwna Chapter 18 802.11N

Front 1

All certified Wi-Fi products must support what two mechanisms?

Back 1

Wi-Fi Multimedia (MM) Quality of Service (QoS) mechanisms and WPA/WPA2 security mechanisms

Front 2

MIMO requires the use of multiple radios and antennas called what?

Back 2

radios chains

Front 3

This is a propagation phenomenon that results in two or more paths of the same signal arriving at a receiving antenna at the same time or within nanoseconds of each other.

Back 3

Multipath

Front 4

MIMO receivers will use this to sort out originally transmitted signals.

Back 4

digital signal processing (DSP)

Front 5

This allows for transmitting multiple streams of data which provides for greater throughput and takes advantage of multipath.

Back 5

spatial multiplexing (SM)

Front 6

A ________ is defined as a single radio and all of its supporting architecture, including mixer, amplifiers, and analog/digital converters.

Back 6

radio chain

Front 7

In a mimo system, the first number for example 3x3:3 always references what? The second number references what?

Back 7

transmitters (TX)

Receivers (RX)

Front 8

In a mimo system, the third number for example 3x3:3 always references what?

Back 8

how many unique streams of data can be sent or received

Front 9

A MIMO radio has the ability to send independent unique data streams which are known as what?

Back 9

spatial streams

Front 10

When a 3x3:3 access point and a 2x2:2 client device are communicating with each other, how many spatial streams will be used for unicast transmissions?

Back 10

2

When a client radio joins a BSS, the AP is advised about the client radio MIMO capabilities.

Front 11

The 802.11n amendment does allow for the use of up to ________ MIMO system.

Back 11

4x4:4

Front 12

Multiple spatial streams can be sent with ________ or ___________ modulation.

Back 12

Equal; unequal

Front 13

Antenna diversity is a method of using multiple antennas to survive the negative effects of what?

Back 13

multipath

Front 14

Most pre 802.11n radios use this.When receiving RF signals, this system listens with multiple antennas. Multiple copies of the same signal arrive at the receiver antenna with different amplitudes. The signal with the best amplitude will be chosen.

Back 14

switched diversity

Front 15

These are used to combine multiple received signals by looking at each unique signal and optimally combining the signals in a method that is additive as opposed to destructive.

Back 15

MRC algorithms

maximal ratio combining algorithms

Front 16

A method where the same information is transmitted on two or more antenna.

Back 16

Space time block coding (STBC)

Front 17

STBCand cyclic shift diversity (CDS) are _______ ________ techniques where the sametransmit data is sent out of multiple antennas.

Back 17

transmit diversity

Front 18

Specifiedin the 802.11n standard. This is another transmit diversity technique. A signalfrom a transmitter that used this can be received by legacy 802.11g and 82.11adevices.

Back 18

Cyclic Shift Diversity (CSD)

Front 19

_________________ can be used when there are more transmitting antennas than there arespatial data stream. The 802.11n amendment proposes an optional PHY capability.

Back 19

Transmit Beamforming

Front 20

When controlling the phase of signals transmitted from multiple antennas, what effect can occur?

Back 20

Emulating a direction antenna

Front 21

By using __________ _________ transmitters that use beamforming they will try to adjust the phase of the signals based on feedback from the receiver.

Back 21

sounding frames (any frame can be used as a sounding frame)

Front 22

When transmitters use beamforming, the transmitter is considered the _________, while the receiver is considered the _________.

Back 22

beamformer; beamformee

Front 23

Which band does Orthogonal Frequency Division Multiplexing (OFDM) technology operate in the 802.11n standard?

Back 23

802.11n (HT) radios can operate in both the 2.4 and 5 GHz frequencies.

Front 24

An HT 20 MHz OFDM channel has how many subcarriers and how many of these subcarriers are used as pilot tones for dynamic calibration between the transmitter and receiver?

Back 24

64 subcarriers

52 transmit data, while 4 are used for pilot tones.

Front 25

802.11 (HT) that transmit using the 40 MHz OFDM channel use how many subcarriers? How many of these subcarriers transmit data? How many of these subcarriers are used for pilot tones for dynamic dynamic calibration between the transmitter and receiver?

Back 25

40 MHz HT channels use 128 OFDM channels. 108 transmit data and 6 are used as pilot tones.

Front 26

In a multi path environment, symbols travel different paths, and therefore some symbols arrive later. A "new" symbol may arrive at a receiver before a "late" symbol has been completely received. This is known as what?

Back 26

intersymbol interference (ISI)

Front 27

What is the maximum delay spread?

Back 27

200 nanoseconds

Front 28

802.11n data rates are defined with a modulation and coding scheme (MCS) matrix. How many mandatory modulation and coding schemes are there for 20 MHz HT channels?

Back 28

8

Front 29

When an MPDU is sent down from layer 2 to the Physical layer, a preamble and PHY header are added to the MPDU. This creates what?

Back 29

Physical Layer Convergence Procedure Protocol Data Unit (PPDU)

Front 30

non-HT PPDU was defined in what Clause of the 802.11-2012 standard?

Back 30

Clause 18

Front 31

HT Short Training Field (HT-STF) and HT Long Training Field (HT-LTF) are used for synchronization between what?

Back 31

MIMO radios

Front 32

A method of combining multiple frames into a single frame transmission is known as what?

Back 32

Frame aggregation

Front 33

The 802.11n amendment introduced two new methods of frame aggregation to help reduce overhead. What are these two methods?

Back 33

Aggregate MAC Service Data Unit (A-MSDU)

Aggregate MAC Protocol Data Unit (A-MPDU)

Front 34

What is defined for used by 802.11n (HT) radios that is an extension of automatic power save delivery (APSD) that was defined by the 802.11e admendment?

Back 34

Power Save Multi Poll (PSMP)

Front 35

Reduced Interframe Space (RIFS) interval is only _____ microseconds

Back 35

2