Chapter 12 - Supplement - Sheet 1 Flashcards
3 unlicensed bands by the FCC
900Mhz, 2.4Ghz, 5Ghz
ISM Bands
Industrial, scientific, and medial. 900Mhz, 2.4Ghz
UNII Bands
Unlicensed National Information Infrastructure. 5GHz
Number of channels FCC released for the 2.4GHz band
14
Number of configurable channels in the 2.4GHz band
11
Non overlapping channels in the 2.4GHz band
1,6,11
Max Data speeds for 802.11b
11mbps
Data rate shifting
Ability to reduce transmission speeds without restarting a connection to accommodate for various distances from an AP. EXAMPLE: 1mbps when farthest. 11mbps when a little closer. All 802.11 WLAN technologies have this
Frequency and max speed of 802.11g
2.4GHz, 54mbps
Frequency and max speed of 802.11a
5Ghz, 54mbps
Frequency and max speed of 802.11b
2.4GHz, 11mbps
Frequency and max speed of 802.11n
2.4GHz or 5GHz, up to 250mbps
Although 802.11g devices operate on the same frequency as 802.11b devices, 801.11b devices can’t be software upgraded to 802.11g because
802.11g uses a different chipset to attain the 54mbps speeds at 2.4GHz
Although you can use 802.11b equipment in an 802.11g environment, what happens?
All clients must use the 802.12b modulation technique, DSSS. This is not as efficient and results in speeds
DSSS
Direct sequence spread spectrum. Modulation technique used by 802.11b devices.
OFDM
Orthogonal frequency division multiplexing. Modulation technique used by 802.11g devices
How wide are each of the 14 channels in the 2.4Ghz range?
22MHz wide
Common devices that operate on (and interfere with) the 2.4Ghz bamd
Microwaves, cordless phones, Bluetooth devices
Number of channels available to 802.11a devices, which operate on the 5Ghz band
12 non-overlapping channels at first. 11 more added in 2004
DFS
Dynamic frequency selection. Feature of 802.11a that detects radar signals operating at the 5GHz band and marks that specific channel as unavailable to clients
TPC
Transmit power control. Feature of 802.11a devices that allows for changing the power of transmission. Example: reducing to 5mW reduces transmission radius and improves performance for clients in I,mediate area
MIMO
Multiple input, multiple output. Feature of 802.11n that allows for multiple trams,otters and recovers to increase data throughout.
802 standard that introduced DFS, TPC
802.11h
Max antennae on an 802.11n device
8
Year 802.11 ratified
1997