Additional SRS Power Headroom Reporting Under LAA Channel Uncertainty
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Solution Overview
Problem
Existing wireless communication systems face challenges in accurately reporting power headroom for additional SRS transmissions, particularly in scenarios involving Licensed-Assisted Access (LAA) SCells where channel access is uncertain due to Listen Before Talk (LBT) procedures.
Innovation Solution
Introduce a new power headroom reporting mechanism, specifically defining a new PH type (Type-3A), which calculates power headroom assuming aperiodic additional SRS transmission on LAA SCells, irrespective of actual channel access, using equations that account for maximum transmit power, path loss, and power control adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If power headroom reporting is based on actual SRS transmission in LAA SCells, then reporting accuracy reflects real channel conditions, but channel access uncertainty due to LBT prevents reliable reporting
Solution Approach 1:
The patent applies preliminary action by calculating and reporting power headroom values before actual SRS transmission occurs. The UE computes PH type 3A based on scheduled aperiodic additional SRS transmissions in LAA SCells, assuming the transmission would occur, thereby providing power headroom information to the eNB before channel access uncertainty is resolved through LBT procedures
Solution Approach 2:
The patent introduces PH type 3A as an intermediary reporting mechanism that bridges the gap between scheduled SRS transmissions and actual LAA channel access. This intermediate power headroom report allows the eNB to plan resource allocation and power control strategies without being blocked by LBT-induced transmission uncertainties
2Productivity
If multiple SRS types (additional SRS, legacy SRS, Rel-14 SRS) are transmitted in the same subframe, then SRS capacity and coverage are enhanced, but complexity of power headroom reporting increases
Solution Approach 1:
The patent segments power headroom reporting into distinct types: PH type 1 for PUSCH-based SRS, PH type 2 for PUCCH-based SRS, and PH type 3A for additional SRS without PUSCH/PUCCH. This segmentation allows each SRS transmission type to have its own dedicated power headroom report, simplifying the overall reporting mechanism while supporting multiple simultaneous SRS configurations
Solution Approach 2:
The patent applies local quality by configuring different power headroom reporting behaviors for different SCells based on their specific characteristics. The eNB can selectively enable PH type 3A reporting for LAA SCells with additional SRS configurations while using traditional PH types for other cells, optimizing reporting complexity locally rather than globally
3Measurement precision
If aperiodic additional SRS transmission is configured in LAA SCells, then uplink channel estimation capability is improved, but power headroom calculation becomes uncertain due to LBT
Solution Approach 1:
The patent applies preliminary action by calculating power headroom for aperiodic additional SRS transmissions before actual transmission occurs. The UE computes PH type 3A based on the scheduled SRS transmission parameters and assumed channel access, providing the eNB with advance power headroom information that enables proper resource allocation even though the actual transmission may be blocked by LBT
Solution Approach 2:
The patent introduces a new parameter PH type 3A that specifically handles power headroom calculation for additional SRS without PUSCH/PUCCH. This parameter change enables the system to distinguish and separately manage power headroom reporting for different SRS transmission scenarios, allowing reliable power control decisions despite LBT-induced transmission uncertainty
Data Source
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AI summary
Methods and apparatuses for power headroom report for additional SRS are disclosed. A method at a UE comprises calculating a power headroom (PH) according to additional SRS if SRS is transmitted on the additional SRS symbol (s) in a normal subframe; and reporting at least one type of the PH calculated according to the additional SRS, Type-3 PH and Type-1 PH by a MAC CE.