QoS standard for WLANs
Transmit power management
Changes transmit power to avoid creating interference for other devices
The original 802.11 standard used…
FHSS and DSSS to achieve 1 and 2 mbps
802.11 is a ___________ standard
layer 2 standard
802.11 is focussed on the delivery of…
MSDU’s between peer LLC devices
MAC and PHY sublayer characteristics
The 2 lesser used 802.11 standards are…
802.11ac – bonded channel 802.11n
802.11ad – WiGig 60ghz ISM band
LLC sublayer makes 802.11 look like…
every other L2 protocol to other high level protocols
The MAC layer ________, but the LLC layer __________
changes, stays the same
LLC is independent of…
2) trans medium
3) MAC techniques used
LLC provides 3 basic services:
1) Unack’d connectionless
2) Ack’d conn-oriented
3) Ack’d connectionless
The 3 purposes of control frames are…
A 0 in the IG header bit means
A 1 in the IG header bit means
A 0 in the CR header bit means
A 1 in the CR header bit means
In control frames, what does 00 signify?
In control frames, what does 01 signify?
In control frames, what does 10 signify?
Receiver not ready
In control frames, what does 11 signify?
STA’s are generally not a _______
STA’s can be ___________ in 802.11, but not 802.3
Hidden from eachother
802.11 can handle 2 types of stations…
Mobile and portable
In 802.11 context, mobile means… and portable means….
Mobile means device accesses LAN in motion
Portable means device can move but is stationary upon accessing LAN
The PLCP… (PHY layer definition)
Maps MAC sub layer data units to a framing format
The PMD…(PHY layer definition)
Defines characteristics of tx/rx through wireless medium
The PLME…(PHY layer definition)
Manages local PHY functions with MAC management entity
4 speeds of 802.11b
1,2,5.5 and 11mbps
802.11b uses DSSS and CCK
The chipping rate of 802.11b is…
802.11b uses the same PLCP as
The original 802.11
Total number of 802.11b channels…
Actual allowed number of channels for 802.11b for each country:
JAPAN: All 14
Power levels for 802.11b…
In 802.11b, channels 1.6 and 11 are referred to as..
In 802.11b, channels 2,3,4,5,7,8,9,10 are referred to as…
Channels 1, 6, and 11 exact frequencies are…
2412, 2439, and 2462 mhz
802.11a has how many channels
802.11a operates at what throughput potentially…
Does 802.11a have any backwards compatibility?
Communication channel into equally spaced frequency bands
OFDM creates ____ subcarriers each at _____ distance from eachother
How many OFDM subcarriers are for data? and for syncing?
OFDM is less sensitive to ________ than DSSS
Four 802.11a modulation techniques…
54mbps @ 2.4ghz
What is used for 20mbps+ connections in 802.11g?
What is used for speeds under 20mbps in 802.11g?
What is protection mode?
B clients on a G network are protected from OFDM which causes a significant decrease in throughput of 802.11g
Max possible throughput of 802.11n?
802.11n operates at…
2.4 and 5ghz
2 techniques for 802.11n
1) MIMO – uses maximum ratio combining
2) Channel bonding
3) Frame aggregation – multiple LLC’s put into one MAC frame
3 legacy modes of 802.11n…
1) greenfield (HT) – assumes no legacy devices
2) Legacy mode (non-HT) – 20mhz channels only, no channel bonding
3) HT mixed mode – RTS/CTS must be a/g format
802.11h is required by…
ETSI for 5ghz range
2 main features of 802.11h…
1) Dynamic frequency selection to avoid interference
2) Transmit control power – minimizes interference on other systems