Karteikarten
Wi-fi Access
Karten in diesem Stapel (16)
- 1Process used to ensure that only one 802.11 radio is transmitting at a time The IEEE 802.11-2012 standard defines a function called Distributed Coordination Function (DCF) Medium access method that utilizes multiple checks and balances to try to minimize collisions This process does not specifically determine whether a collision occursCSMA/CA
- 2Is the fundamental and mandatory access method of 802.11 communicationsDistributed Coordination Function
- 3Here are the four main components of DCF/ CSMA/CA Interframe Space
Duration/ID Field
Carrier Sense
Random Backoff Timer - 4What is the funcion of the previous componentsEnsure that only one 802.11 radio is transmitting on
the half-duplex medium - 5Period of time that exists between transmissions of wireless framesInterframe Space (IFS)
- 6Mention the 6 types of IFSs with corresponding priority: Reduced Interframe Space (RIFS), highest priority
Short Interframe Space (SIFS), second highest priority
PCF Interframe Space (PIFS), middle priority
DCF Interframe Space (DIFS), lowest priority
Arbitration Interframe Space (AIFS), used by QoS stations
Extended Interframe Space (EIFS), used after receipt of
corrupted frames - 7The two most common interframe spaces used are:
- 8This value represents the time, in microseconds, that is required to transmit an active frame exchange process so that other radios do not interrupt the processDuration/ID field contains a value from 0 to
32,767 - 9virtual Carrier Sense timer that maintains a prediction of future traffic on the medium based on Duration value information seen in a previous frame transmission
- 10Physical carrier sense has two purposes:. To determine whether a frame transmission is inbound for a station to receive
.To determine whether the medium is busy before transmitting: Also known as channel assessment (CCA) - 11What is the OFDM Carrier Sense Algorithm:1) random number from a contention window of 0–15 is selected
2) The station multiplies the random number by a slot time of 9μs (random backoff timer)
3)For every slot time during which there is no medium activity, the backoff time is decremented by a slot time
4) The station decrements the backoff timer until the timer is zero
The station transmits if the medium is clear - 12This access method is a form of polling The AP performs the function of the Point Coordinator (PC) because the AP is taking on this role This method will work in only a Basic Service Set (BSS)Point Coordination Function (PCF)
- 13improves channel efficiency by aggregating several acknowledgments into one single acknowledgment frameBlock Acknowledgment
- 14Two types of Block ACK mechanisms: Immediate
Designed for use with low-latency traffic
Delayed
More suitable for latency-tolerant traffic - 15—This frame is known as BlockAckReq
- 16Instead of allocating equal access to the network between devices, the goal of this feature is to allocate equal time, as opposed to equal opportunity enables devices to maintain communications by shifting to slower data rates as they move away from an access pointAirtime Fairness
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- Informática y Comunicaciones Karteikarten am Wi-fi Access, erstellt von Hugo Castro Gould am 24/07/2022.
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- Hugo Castro Gould
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