CCNA Wireless Chapter 6 answers

802.11e is…

QoS standard for WLANs

802.11h is…
Transmit power management
Changes transmit power to avoid creating interference for other devices

802.11i is…
Security standard

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

802.11 defines…
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…
1) topology
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…
1) Information
2) Supervisory
3) Unnumbered

A 0 in the IG header bit means
individual address

A 1 in the IG header bit means
group address

A 0 in the CR header bit means
command

A 1 in the CR header bit means
response

In control frames, what does 00 signify?
Receive ready

In control frames, what does 01 signify?
Reject

In control frames, what does 10 signify?
Receiver not ready

In control frames, what does 11 signify?
Undefined

STA’s are generally not a _______
Fixed location

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…
11mhz

802.11b uses the same PLCP as
The original 802.11

Total number of 802.11b channels…
14

Actual allowed number of channels for 802.11b for each country:
US: 11
ETSI: 13
JAPAN: All 14

Power levels for 802.11b…
US: 36dbm
ETSI: 20dbm

In 802.11b, channels 1.6 and 11 are referred to as..
Set 1

In 802.11b, channels 2,3,4,5,7,8,9,10 are referred to as…
Set 2

Channels 1, 6, and 11 exact frequencies are…
2412, 2439, and 2462 mhz

802.11a has how many channels
8

802.11a operates at what throughput potentially…
54mbps

Does 802.11a have any backwards compatibility?
No.

OFDM divides…
Communication channel into equally spaced frequency bands

OFDM creates ____ subcarriers each at _____ distance from eachother
52, 312.5khz

How many OFDM subcarriers are for data? and for syncing?
48, 4

OFDM is less sensitive to ________ than DSSS
Multipath interference

Four 802.11a modulation techniques…
BPSK
QPSK
16QAM
64QAM

802.11g throughput…
54mbps @ 2.4ghz

What is used for 20mbps+ connections in 802.11g?
OFDM

What is used for speeds under 20mbps in 802.11g?
CCK

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?
600mbps

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

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