NSTR Multi-Link Medium Access Recovery After Synchronization Loss
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Solution Overview
Problem
In wireless communications, multi-link devices operating on a non-simultaneous-transmission-and-reception link pair face issues with medium synchronization due to in-device coexistence interference, leading to collisions and loss of synchronization, particularly when one link transmits a PPDU with a length greater than a threshold, affecting network allocation vector updates and medium access.
Innovation Solution
Implementing a medium access recovery mechanism for peer multi-link devices, including schemes for TXOP initiators and responders to transmit control frames with medium synchronization loss indications, adjust channel access thresholds, and manage MediumSyncDelay timers to regain synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an NSTR MLD transmits on link 1 with a PPDU length greater than a threshold, then transmission throughput is improved, but medium synchronization is lost on link 2 due to transmit power leakage interference
Solution Approach 1:
The patent applies preliminary action by initiating the MediumSyncDelay timer in advance before the actual synchronization recovery is needed. When a TXOP holder transmits a PPDU longer than a threshold on one link, the timer is started before the potential synchronization loss occurs, allowing the system to prepare for and manage the synchronization recovery period proactively rather than reactively.
Solution Approach 2:
The MediumSyncDelay timer acts as an intermediary mechanism between the transmission activity on one link and the synchronization state on another link. It mediates the interference caused by transmit power leakage by introducing a controlled delay period that allows the NAV to be updated and synchronization to be recovered without immediately impacting ongoing transmissions.
2Reliability
If a TXOP initiator waits for medium synchronization recovery before accessing the medium, then communication reliability is improved, but access delay increases due to non-zero MediumSyncDelay timer
Solution Approach 1:
The TXOP initiator performs preliminary actions by transmitting control frames (such as RTS) immediately after obtaining TXOP, even before the MediumSyncDelay timer expires. This allows the initiator to prepare for the synchronization recovery period in advance, reducing the overall delay by overlapping the control frame transmission with the timer countdown.
Solution Approach 2:
The patent applies dynamics by allowing the TXOP initiator to flexibly manage the timing of control frame transmissions based on the MediumSyncDelay timer state. The initiator can dynamically adjust when to transmit control frames versus when to wait for synchronization, optimizing the balance between reliability and delay based on real-time conditions.
3Reliability
If a TXOP responder waits for medium synchronization recovery before responding, then communication reliability is improved, but response time increases due to non-zero MediumSyncDelay timer
Solution Approach 1:
The TXOP responder performs preliminary actions by preparing for and transmitting response frames during the MediumSyncDelay timer period. Instead of passively waiting for synchronization recovery, the responder actively manages the response timing by transmitting control frames at appropriate intervals during the delay period, reducing overall response time while maintaining reliability.
Solution Approach 2:
The patent implements feedback mechanisms where the TXOP initiator and responder exchange control frames that carry information about their synchronization states and timer statuses. This feedback allows both parties to coordinate their transmissions during the MediumSyncDelay period, ensuring reliable communication while minimizing response time through informed timing decisions.
4Speed
If virtual channel sensing is performed without updated NAV information, then medium access speed is improved, but collision probability increases on link 2
Solution Approach 1:
The patent applies preliminary action by updating the NAV field in advance during the MediumSyncDelay timer period. Instead of waiting for the synchronization recovery to complete before performing virtual channel sensing, the system performs the NAV update as a preliminary action during the delay period, ensuring that when virtual channel sensing occurs, the NAV is already updated with accurate information about ongoing transmissions on link 2.
Solution Approach 2:
The MediumSyncDelay timer provides a cushioning period that allows the NAV to be updated before virtual channel sensing is performed. This beforehand cushioning ensures that the NAV contains accurate information about the current transmission state on link 2, preventing collisions by ensuring that virtual channel sensing is based on up-to-date NAV information rather than stale or missing information.
Data Source
AI summary
A station (STA) affiliated with a non-simultaneous-transmission-and-reception (NSTR) multi-link device (MLD) obtains a transmission opportunity (TXOP) on a first link of an NSTR link pair as a TXOP initiator while a medium synchronization delay timer of the STA is non-zero. STA determines that an intended TXOP responder has lost medium synchronization. The STA then transmits a control frame as an initial frame in the TXOP to the intended TXOP responder on the first link responsive to the determining.