802.11b MAC Timings
What are MAC timings in IEEE 802.11b?
MAC timings define the timing intervals used for coordinating wireless transmissions and medium access.
What is SIFS in 802.11b MAC timings?
Short Interframe Space (SIFS) is the shortest waiting time between frames, used for ACKs and control frames.
What does DIFS stand for and what is its role?
Distributed Interframe Space (DIFS) is the waiting period before a station attempts to access the medium after it is idle.
What is PIFS and when is it used?
Point Coordination Function Interframe Space (PIFS) is used by the PCF for priority medium access.
How does the backoff timer work in 802.11b?
Stations select a random backoff time within a contention window to reduce collisions when accessing the medium.
What is the slot time in 802.11b MAC?
Slot time is a fixed duration used in backoff timing, representing the basic unit for medium sensing.
Why are interframe spaces important?
They provide necessary gaps between transmissions to allow devices to detect the medium status and coordinate access.
How is the Network Allocation Vector (NAV) related to MAC timings?
NAV is a timer that indicates how long the medium will be busy, preventing other stations from transmitting during that time.
What is the relationship between SIFS and ACK frames?
ACK frames are transmitted after a SIFS interval to confirm successful reception.
How does the contention window affect timing?
The contention window defines the range for the random backoff timer used before transmission attempts.
What happens if the medium is busy during backoff?
The backoff timer pauses and resumes when the medium becomes idle again.
How are retransmission timings controlled?
Retransmissions occur after waiting for a backoff interval if no ACK is received.
What is EIFS in 802.11b?
Extended Interframe Space (EIFS) is used after detecting corrupted frames to give priority to ongoing transmissions.
Why is timing coordination critical in 802.11b?
It prevents collisions, ensures fair access, and improves overall network efficiency.
How are timing parameters standardized?
IEEE 802.11b defines fixed values for SIFS, DIFS, slot time, and contention windows to ensure interoperability.
How does timing affect QoS in 802.11b?
While basic 802.11b lacks advanced QoS, timing intervals influence prioritization of ACK and control frames.
How do timing mechanisms aid hidden node problem mitigation?
Proper timing and RTS/CTS handshakes help reduce collisions from hidden nodes.
Can timing parameters be adjusted dynamically?
Some implementations adjust contention windows based on network congestion to optimize performance.
What timing differences exist between 802.11b and other 802.11 standards?
802.11b uses longer slot times (20 µs) compared to 802.11a/g (9 µs), reflecting differences in physical layer properties.
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