CWNA

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Flashcards for the Certified Wireless Network Administrator Exam

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List the three types of wave modulation:

Amplitude
Frequency
Phase

What are the three ways a wave can be modulated?

Amplitude
Frequency
Phase

How does a "Keying Method" relate to wave forms?

A keying method describes the type of modulation used. Amplitude Shift Keying - ASK
Frequency Shift Keying - FSK
Phase Shift Keying - PSK

Which keying method is used for WiFi?

PSK - Phase Shift Keying

What is the wavelength of the center 2.4ghz frequency?

4.82in - 12.24cm

What is the wavelength of the center 5ghz frequency?

2.04in - 5.19cm

What are the first and last channels and center frequencies used in the US for the 2.4Ghz band?

1 - 2412mhz 11 - 2462

What are the first and last channels and center frequencies used in the US for the 5 Ghz band?

36 - 5180
165 - 5825

What is the formula used to translate channels to frequency in the 5Ghz band?

(channel) x 5 + 5000

What are the center frequencies for channels 1 6 and 11?

2412
2437
2462

How many mhz separate each channel in the 2.4ghz band?

5mhz

How many mhz separate each 20 mhz wide channel in the 5ghz band?

20 mhz

What is the standard attenuation of sheetrock?
brickwall?
Elevator?

3db
12db
10db

How many DB does 2.4ghz attenuate by in 1 meter?
100 meters?
200 meters?

40dbm
80
86

How many DB does 5ghz attenuate by in 1 meter?
100 meters?
200 meters?

47dbm
87
93

How many DB does signal attenuate when the distance between systems is doubled?

6db

Which WiFi frames require an ACK?

Any unicast data frames.

Convert dbm to mw:
10dbm
20dbm
26dbm
36dbm

10mw
100mw
400mw
4000mw

Convert dbm to mw:
-16dbm
-20dbm
-26dbm
-60dbm

.025mw
.01mw
.0025mw
0.000001mw

What does the E plane show you on an azimuth chart?

elevation view - from the side

What does the H plane show you on an azimuth chart?

top down - overHead view

What are the three types of beamforming and how are they generally used?

Static beamforming - fixed anteanns - cell towers
Dynamic beamforming - adaptive antenna array used to switch power and signal patterns - Used by Ruckus
Transmit Beamforming - TxBF used in WiFi

List the two types of TxBF

implicit beamforming - uses channel sounding to guess optimied phasing
explicit beamforming - uses vmatrix received from client to determine correct phase shift

What is contained in the TxBF V matrix?

amplitude and phase per TX antenna per RX antenna per subtone

How much gain can be derived from TxBF?

5db

How much can the first fresnel zone be obscured before causing an unrealiable link?

40 percent

Does the beamwidth of the antenna have any bearing on the size of the fresnel zone?

no

Which fresnel zones are in-phase with the point source signal?

1 - 3 - 5

Which fresnel zones are out-of-phase with the point source signal?

2 - 4 - 6

At what distance must earth bulge be considered?

more than 7 miles or 11 kilometers

What antenna issue can cause a loss of 15-20db below expected received signal level?

incorrect polarization

What is the standard impedence for WiFi antenna systems?

50 ohms

What is the standard loss in db for each connection in an antenna system?

0.5db

What is the standard db loss for 2.4 ghz in LMR 400 cable:
100ft?
100m?

0.2bd
0.6db