802.11aj MAC Timings
What are MAC timing functions in 802.11aj?
MAC timing in 802.11aj includes precise scheduling, timing synchronization, and beacon interval coordination for high-frequency bands (45 GHz and 60 GHz).
How is time synchronization maintained in 802.11aj?
Synchronization is achieved using beacons with timing information, allowing stations to align clocks accurately even in directional transmission environments.
Does 802.11aj use a timing synchronization function (TSF)?
Yes, the TSF is used to maintain synchronized timing across devices within a PBSS or infrastructure-based network.
What is the Beacon Interval in 802.11aj?
The beacon interval defines how often the PCP sends timing beacons; it is configurable and optimized for low-latency and directional operation.
What are the types of access periods controlled by MAC timing?
CBAP (Contention-Based Access Period) and SP (Service Period) are both time-based channel access methods controlled by MAC timing.
How are Service Periods (SPs) scheduled?
The PCP assigns SPs to devices for contention-free access, with exact timing advertised in the beacon frame.
Is there a guard interval in 802.11aj MAC scheduling?
Yes, guard intervals are included between scheduled transmissions to avoid timing overlaps and collisions.
How does 802.11aj handle timing in beamformed links?
Directional transmission requires precise timing coordination, which is managed using scheduled time slots and beam refinement intervals.
What timing granularity is used for access period scheduling?
High-resolution timers are used to define CBAPs and SPs with fine granularity for better efficiency.
What is the role of Target Beacon Transmission Time (TBTT)?
TBTT marks the scheduled time for the next beacon, helping devices wake up and synchronize efficiently.
Are timing parameters adjustable in 802.11aj?
Yes, parameters like beacon interval, SP duration, and CBAP windows can be dynamically adjusted by the PCP based on network conditions.
How does MAC timing support power saving?
Stations use timing information to sleep and wake during their assigned SPs, reducing unnecessary channel monitoring.
What happens if timing drift occurs?
Periodic beacon updates correct clock drift, maintaining precise synchronization across the network.
Is timing coordination needed for handovers?
Yes, accurate timing is essential during fast band switching or beam realignment to avoid dropped packets or service gaps.
How are overlapping transmissions avoided?
Timing coordination ensures scheduled transmissions do not conflict, especially in beamformed and directional links.
Can MAC timing adjust for propagation delay?
Yes, timing corrections can account for propagation delays in long-range directional links to maintain alignment.
Is legacy timing behavior preserved in 802.11aj?
802.11aj maintains compatibility with 802.11ad timing formats to ensure interoperability where needed.
What timers are used in MAC-level coordination?
Timers like NAV, SP timers, and TSF are used for access deferral, synchronization, and service scheduling.
Do beacons contain timing for both 45 GHz and 60 GHz?
Yes, when operating in dual-band mode, beacons may carry timing and scheduling info for both bands for seamless switching.
Is there timing support for channel hopping?
Yes, MAC timing includes coordination of channel switching, including pre- and post-switch dwell times.
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