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Cisco 200-355 > RF Standards > Flashcards

RF Standards Flashcards

1
Q

What does ITU-R stand for?

A

International Telecommunication Union Radiocommunication Sector.

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2
Q

What is the ITU-R?

A

United Nations regulatory body that manages the RF spectrum globally.

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3
Q

What are the different regions in the ITU-R?

A
  1. Europe, Africa, and Northern Asia
  2. North and South America
  3. Southern Asia and Australia
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4
Q

What does ISM stand for and who established it?

A

Industrial, Scientific, and Medical applications.

ITU-R allocated the frequencies.

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5
Q

What are the two ISM bands in the wireless LAN range?

A
  1. 400 to 2.500 GHz

5. 725 to 5.825 GHz (U-NII-3)

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6
Q

What is the organization in the US that regulates RF frequencies, channels, and transmission power?

A

FCC (Federal Communications Commission)

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7
Q

What does U-NII stand for and who allocated this for wireless?

A

Unlicensed National Information Infrastructure

FCC allocated for wireless

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8
Q

What is the frequency range and channel numbers of U-NII-1?

A

5.15 to 5.25 GHz

36, 40, 44, 48

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9
Q

What is the frequency range and channel numbers of U-NII-2?

A

5.25 to 5.35 GHz

52, 56, 60, 64

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10
Q

What is the frequency range and channel numbers of U-NII-2 Extended?

A

5.47 to 5.725 GHz

100 to 140 (increments of 4)

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11
Q

What is the frequency range and channel numbers of U-NII-3?

A

5.725 to 5.825 GHz

149, 153, 157, 161

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12
Q

What is the max transmitter power allowed by the FCC for 2.4 GHz?

A

30 dBm

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13
Q

What is the FCC rule for determining the max EIRP for 2.4 GHz point-to-multipoint links?

A

1:1 rule - for each dBm removed from tx power can add 1 dBm in gain at antenna but max EIRP is 36 dBm.

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14
Q

What is the FCC rule for determining the max EIRP for 2.4 GHz point-to-point links?

A

3:1 rule - for each dBm removed from tx power can add 3 dBm in gain at antenna but max EIRP is 56 dBm.

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15
Q

What are the FCC tx power and EIRP max limitations for U-NII bands?

A 
Band           Tx Max    EIRP Max
U-NII-1         17 dBm    23 dBm
U-NII-2        24 dBm   30 dBm
U-NII-2 Ext. 24 dBm   30 dBm
U-NII-3        30 dBm   36 dBm
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16
Q

What does ETSI stand for?

A

European Telecommunication Standards Institute

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17
Q

What are the ETSI EIRP max limitations for 2.4 GHz and 5 GHz bands?

A 
Band           EIRP Max
2.4 GHz      20 dBm
U-NII-1         23 dBm
U-NII-2        23 dBm
U-NII-2 Ext. 30 dBm
U-NII-3        NA (licensed band)
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18
Q

List which U-NII bands are for Indoor only (I) use or Indoor and Outdoor (I/O) use as indicated by the FCC and ETSI?

A 
Band            FCC     ETSI
U-NII-1             I            I
U-NII-2           I/O         I
U-NII-2 Ext.    I/O        I/O
U-NII-3           I/O        NA
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19
Q

What is DFS and why is it necessary?

A

Dynamic Frequency Selection
In the U-NII-2 and U-NII-2 Extended bands, certain approved devices like radar have priority and other devices like wireless need to move off a frequency if radar is detected.

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20
Q

The original 802.11 amendment was ratified in what year and what frequency band(s) were available?

A

1997

2.4 GHz

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21
Q

What data rates were included in the 802.11 amendment?

A

1 and 2 Mb - FHSS
1 Mb - DSSS (DBPSK)
2 Mb - DSSS (DQPSK)

22
Q

802.11b was introduced in 1999. What data rates were added?

A

5.5 Mb - DSSS (DQPSK w/CCK 4)

11 Mb - DSSS (DQPSK w/CCK 8)

23
Q

802.11g was introduced in 2003. What tranmission type was added and what band(s) were available?

A

OFDM

2.4 GHz

24
Q

With 802.11g using OFDM, what data rates where added?

A 
6 Mb (BPSK 1/2)
9 Mb (BPSK 3/4)
12 Mb (QPSK 1/2)
18 Mb (QPSK 3/4)
24 Mb (16-QAM 1/2)
36 Mb (16-QAM 3/4)
48 Mb (64-QAM 2/3)
54 Mb (64-QAM 3/4)
25
Q

What happens if an 802.11b device is detected by 802.11g devices?

A

Goes into 802.11g protective mode.

DSSS RTS and CTS is sent before OFDM data that gives the length of message. (may reduce throughput by as much as half)

26
Q

What are some of the benefits of 802.11a?

A

Only uses 5 GHz where there are more channels.

Only allows OFDM transmission.

27
Q

What are the data rates available for 802.11a?

A 
Same as 802.11g
6 Mb (BPSK 1/2)
9 Mb (BPSK 3/4)
12 Mb (QPSK 1/2)
18 Mb (QPSK 3/4)
24 Mb (16-QAM 1/2)
36 Mb (16-QAM 3/4)
48 Mb (64-QAM 2/3)
54 Mb (64-QAM 3/4)
28
Q

When was 802.11n published and what band(s) does it use?

A

2009

2.4 GHz and 5 GHz

29
Q

What is the theoretical max data rate for 802.11n?

A

600 Mb

30
Q

What 3 features introduced in 802.11n help improve throughput?

A

Channel aggregation
Spatial multiplexing (SM)
MAC layer efficiency

31
Q

What 2 features introduced in 802.11n help improve reliability of RF signals?

A 
Transmit beamforming (TxBF)
Maximal-ratio combining
32
Q

In 802.11n, how many channels can be aggregated?

A

Two 20 MHz channels which must be adjacent to create a 40 MHz channel. (not recommended in 2.4 GHz)

33
Q

How many subcarriers, including pilot ones, are in a 20 MHz and 40 MHz channel?

A

20 MHz - 52

40 MHz - 108 (guard between channels is gone)

34
Q

What does SISO and MIMO stand for?

A

Single-In, Single-Out (one receiver, one transmitter)

Multiple-Input, Multiply-Output (more that one receiver and more than one transmitter)

35
Q

How are MIMO devices labeled to designate their capabilities?

A

TxR:S
Transmitters
Radios
Spatial Streams

36
Q

In 802.11n what is the minimum MIMO requirement?

A

2 transmitters and 2 receivers is the minimum

4x4 is maximum

37
Q

In 802.11n, what to methods are used to support MAC Layer Efficiency?

A

Block acknowledgement
let’s data burst and ack after burst
Guard interval
standard 800 nanosecond separation can be configured down to 400 nanoseconds

38
Q

What is the benefit of Transmit Beamforming?

A

To improve signal strength by using multiple transmitters to send to one receiver. The phase of each transmitter is altered to have the signal arrive in phase by the receiver.

39
Q

What is Cisco’s version of Transmit Beamforming called?

A

ClientLink

40
Q

What does MRC stand for and what does it do?

A

Maximal-Ratio Combining

Combines the copies of transmitted signals to produce one signal that represents the best version.

41
Q

What does MCS stand for and how many are supported in 802.11n?

A

Modulation and Coding Schemes

32 possible schemes (8 per spatial stream)

42
Q

When was 802.11ac finalized and when fully implemented what will the maximum data rate be?

A

2013

6.93 Gb

43
Q

What performance enhancements were made in 802.11ac?

A

Better channel aggregation (80 and 160 MHz wide)
More dense mod. (256-QAM)
MAC Layer efficiency (frame aggregation)
Explicit TxBF (only 1 feedback method supported)
Scalable MIMO (up to 8 spatial streams)
Multi-user MIMO (MU-MIMO send to multiple devices at once)

44
Q

What is dynamic use with channel aggregation in 802.11ac?

A

The channel width is negotiated by frame. If needed and the channels are available (negotiated with RTS and CTS frames) it will be utilized so that AP can share channels better.

45
Q

How many Modulation Code Schemes are available in 802.11ac?

A

10 (0 - 9) Unlike 802.11n, it is not tied to spatial streams.

46
Q

In 802.11ac, what is the TxBF method called?

A

Null Data Packet (NDP)

47
Q

What are the tested features/capabilities of 802.11ac Wave 1?

A 
Max channel width: 80 MHz
Max spatial streams: 3
Max modulation: 256-QAM optional
MU-MIMO: No
Max data speed: 1.3 Gb
48
Q

What are the tested features/capabilities of 802.11ac Wave 2?

A 
Max channel width: 160 MHz
Max spatial streams: 4
Max modulation: 256-QAM
MU-MIMO: Yes
Max data speed: 2.6 Gb
49
Q

What is the organization that test wireless devices to certify compliance with 802.11 standards?

A

Wi-Fi Alliance

50
Q

What channels are exempt from DFS?

A

36 - 48 and 149 - 165

Cisco 200-355 (19 decks)

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