Ch 8 802.11 Channel Access Methods

Question 1

is used in 802.11 WLANs

Answer 1

CSMA/CA

Question 2

The foundational channel access function is

Answer 2

DCF (Distributed Coordination Function)

Question 3

Blank is both physical (802.11 frame detection and energy detection) and Blank (nav timers set based on frame duration values).

Answer 3

Carrier sensing and virtual

Question 4

The frame duration value is the time required to complete the transaction after the current PPDU completes.

Answer 4

Frame duration

Question 5

enhances DCF with QoS options.

Answer 5

EDCA (Enhanced Distributed Channel Access)

Question 6

an blank is a function assigned to an AC that is used to gain access during a transmit opportunity for that AC.

Answer 6

EDCAF

Question 7

four ACs are used in EDCA: Blank, and they are listed here in order of lowest to highest priority.

Answer 7

ac_bk, ac_be, ac_vi, and ac_vo

Question 8

Blank (eight of them) map to ACs.

Answer 8

User priorities

Question 9

Each AC has varying ifs delays and contention window ranges. the highest priority ACs have the blank CW range value, blank

Answer 9

the lowest maximum and the shortest AIFS.

Question 10

Blank frames are used as protection mechanism so that newer phys can silence the channel and transmit at their higher data rates.

Answer 10

RTS/CTS

Question 11

APS can use blank, which is just a cts frame without an RTS frame.

Answer 11

CTS-to-Self

Question 12

The blank process is used to set the NAV timer in STAs in the channel.

Answer 12

RTS/CTS process

Question 13

Blank devices can operate in legacy, mixed or greenfield modes.

Answer 13

HT (High Throughout)

Question 14

Blank devices support the three ht modes, and also add a new PPDU format that is compatible with all 5 GHz phy devices.

Answer 14

VHT (Very High Throughout)

Question 15

Blank save is based on STAs awaking and looking at the beacon frame to see if frames are waiting on the ap.

Answer 15

Legacy Power

Question 16

Blank is based on STAs awakening and transmitting anything at all to the AP, and the AP, in turn, will let the STA know if frames are waiting in the queue.

Answer 16

U-APSD