802.11aj MAC Timings ======================= .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **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). .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **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. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **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. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **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. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **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. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **How are Service Periods (SPs) scheduled?** The PCP assigns SPs to devices for contention-free access, with exact timing advertised in the beacon frame. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Is there a guard interval in 802.11aj MAC scheduling?** Yes, guard intervals are included between scheduled transmissions to avoid timing overlaps and collisions. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **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. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **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. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **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. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **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. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **How does MAC timing support power saving?** Stations use timing information to sleep and wake during their assigned SPs, reducing unnecessary channel monitoring. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What happens if timing drift occurs?** Periodic beacon updates correct clock drift, maintaining precise synchronization across the network. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **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. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **How are overlapping transmissions avoided?** Timing coordination ensures scheduled transmissions do not conflict, especially in beamformed and directional links. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Can MAC timing adjust for propagation delay?** Yes, timing corrections can account for propagation delays in long-range directional links to maintain alignment. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Is legacy timing behavior preserved in 802.11aj?** 802.11aj maintains compatibility with 802.11ad timing formats to ensure interoperability where needed. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What timers are used in MAC-level coordination?** Timers like NAV, SP timers, and TSF are used for access deferral, synchronization, and service scheduling. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **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. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Is there timing support for channel hopping?** Yes, MAC timing includes coordination of channel switching, including pre- and post-switch dwell times. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow Topics in this section, * :ref:`Reference links ` .. _mac_timings_aj_step17: .. tab-set:: .. tab-item:: Reference links * Reference links