Wireless Flashcards
What do wireless client receivers use to measure the received signal power level?
Received signal strength indicator (RSSI)
In which mode does an AP passively monitor the WLAN environment over a specifically configured channel?
Sniffer mode
Which AP mode facilitates simplified management and is ideal for environments where a large number of APs are required in a WLAN deployment?
Lightweight mode
Which type of antenna is designed to provide a 360-degree radiation pattern?
Omnidirectional antenna
When multiple wireless clients are encountering connectivity issues in the same area, where would be a good starting point for troubleshooting?
On the access point
A range of frequencies can be used for the same purpose, and such a range is often referred to as what?
band of frequencies
Channels are spaced at regular intervals, and this channel spacing is known as what?
Channel width or separation
The frequency range that is needed to transmit a signal is known as what?
Signal bandwidth. In WLAN communication, the signal bandwidth is defined as part of a wireless standard
True or False: The signal bandwidth should preferably be greater than the channel width.
False. The signal bandwidth should preferably be less than the channel width. This allows for different signals to be transmitted on every possible channel, with no possibility of two signals overlapping and interfering with each other.
A WLAN transmitter typically has a signal strength between what range?
0.1 W (100 mW) and 0.001 W (1 mW)
What term is used to describe the power gain rating of a wireless antenna?
dBi
What can be measured on a scale of 0 to 255, as defined by the 802.11 standards?
Received Signal Strength Indicator (RSSI)
What is the difference between a wireless signal that is received and the noise floor?
Signal-to-noise ratio (SNR). SNR is measured as positive value between 0 dB and 120 dB. The closer the value is to 120 dB, the better.
What is the term for wireless communication that can be multiplexed across two or more radio chains?
Spatial multiplexing
What can improve signal quality and SNR by altering the phase of the signal as it is being fed into the transmitting antenna so that the RF signal can arrive in phase at a receiver?
Transmit beamforming
What combines the multiple copies of the signal to present the best one at a particular time and thus improves SNR?
Maximum-ratio combining
What unit does the FCC use to refer to the power gain rating of a wireless antenna?
dBi
Although vendors can use a different range, what is the range used to measure RSSI as defined in the 802.11 standards?
0 to 255
If a client device receives a –70 dBm signal, and the floor noise is –90 dBm, what is the effective SNR?
20 dB
What type of chart shows how the signal spreads ahead, behind, to the right, and to the left, but not how the signal spreads up or down?
Azimuth chart or H-plane
What type of chart shows how the signal spreads ahead, behind, to the top, and to the bottom, but not how the signal spreads to the right or left?
Elevation chart or E-plane
What type of antenna radiates all around itself equally or at 360 degrees?
Omnidirectional antenna
What type of antenna radiates toward a certain direction, but the beam might be wide or narrow?
Directional antenna
What are the most basic omnidirectional antennas?
Dual-band dipole antennas
What type of antenna provides an RF pattern of thin on the vertical and horizontal planes and reaching far in a narrow beam? Also is well adapted to covering long corridors or large warehouses.
Yagi
What type of antenna is adaptable to long-range outdoor links, mainly in a point-to-point scenario?
parabolic dish