Autonomous Uplink Power Headroom Reporting with LBT Attempt Timing
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Solution Overview
Problem
In wireless communication networks using autonomous uplink (AUL) for unlicensed access (NR-U), the base station (gNB) cannot determine when an uplink transmission was initially generated due to potential listen-before-talk (LBT) failures, leading to inaccurate power headroom reporting (PHR) that affects scheduling and link adaptation.
Innovation Solution
The user equipment (UE) signals timing information to the RAN node indicating whether the uplink transmission is a first or subsequent attempt, updates PHR values for each transmission attempt, always reports a predefined PHR type, includes a field in the PHR MAC CE to indicate the type, prioritizes PHR transmission on licensed cells, or reports virtual PHR for carrier aggregation scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If autonomous uplink transmission is used on unlicensed serving cells, then uplink transmission efficiency is improved, but power headroom reporting accuracy deteriorates due to LBT failures
Solution Approach 1:
The patent applies preliminary action by having the UE indicate in advance whether an AUL transmission is a first or subsequent transmission attempt through timing information in the PHR MAC CE. This allows the gNB to proactively adjust scheduling and link adaptation parameters before actual transmission issues occur, rather than reacting after LBT failures have already degraded PHR accuracy.
Solution Approach 2:
The patent implements feedback mechanisms by incorporating timing information about transmission attempts into the PHR reporting. The gNB receives feedback on whether the PHR corresponds to a first or subsequent transmission attempt, enabling it to adjust scheduling decisions and link adaptation parameters based on this feedback loop, thereby maintaining accurate power headroom reporting despite AUL transmissions on unlicensed cells.
2Reliability
If PHR transmission is prioritized on licensed cells, then PHR reporting reliability is improved, but transmission latency increases
Solution Approach 1:
The patent applies local quality by differentiating transmission priorities based on cell type. PHR transmissions on licensed serving cells are given high priority to ensure reliability, while PHR transmissions on unlicensed serving cells can use normal or lower priority. This localized quality assignment ensures that critical PHR reporting maintains high reliability on licensed cells without unnecessarily increasing latency across all transmissions.
Data Source
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AI summary
Apparatuses, methods, and systems are disclosed for reporting power headroom. One apparatus 400 includes a processor 405 that identifies 605 a transmission occasion for AUL transmission on an unlicensed serving cell and generates 610 a PHR MAC CE. The apparatus 400 includes a transceiver 425 that transmits 615 the PHR MAC CE with an AUL transmission to a RAN node in the mobile communication network, wherein transmitting the PHR MAC CE includes indicating timing information corresponding to the PHR.