HARQ-ACK Exception Control for Long-RTT NR Feedback Reliability
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Solution Overview
Problem
The inefficiency of HARQ feedback mechanisms in next-generation wireless communication systems, particularly in Non-Terrestrial Networks (NTN), due to long Round Trip Times, leads to uncertainties in Semi-Persistent Scheduling and MAC-CE activation/deactivation commands without confirmation messages, necessitating improved NR procedures for enabling/disabling HARQ feedback.
Innovation Solution
Implementing methods for UEs to generate HARQ-ACK information based on exception lists and indicators via RRC, DCI, and MAC-CE, allowing HARQ feedback transmission despite disabled configurations, with specific conditions and commands for various scenarios such as SCell activation, PUCCH power control, and PDSCH reception without corresponding PDCCH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If HARQ feedback transmission is disabled for certain HARQ processes via HARQ-ACK-less list, then signaling overhead is reduced, but reliability of HARQ operations deteriorates due to uncertainties in Semi-Persistent Scheduling and MAC-CE activation/deactivation commands
Solution Approach 1:
The patent applies local quality by enabling HARQ feedback on a per-HARQ-process basis rather than globally. The network can configure a HARQ-ACK-less list that selectively disables feedback for specific HARQ processes while maintaining feedback for others. This allows localized optimization where feedback is disabled only where unnecessary, preserving reliability for processes that require it while reducing overhead for those that don't.
Solution Approach 2:
The patent implements dynamic control of HARQ feedback through multiple mechanisms: RRC configuration for semi-static settings, MAC-CE for dynamic activation/deactivation, and DCI for real-time per-transmission control. This dynamic approach allows the system to adapt feedback requirements based on current network conditions, service types, and traffic patterns, maintaining reliability when needed while reducing overhead when possible.
2Productivity
If HARQ feedback is disabled per-UE basis to reduce overhead, then signaling efficiency is improved, but uncertainty in MAC-CE activation/deactivation commands increases
Solution Approach 1:
The patent ensures feedback mechanisms are maintained for critical operations even when HARQ feedback is generally disabled. Specifically, feedback is preserved for MAC-CE activation/deactivation commands, SCell activation commands, and other control messages that require confirmation. This selective feedback approach maintains signaling efficiency for data transmissions while ensuring reliability for control plane operations.
Solution Approach 2:
The patent segments the HARQ feedback mechanism into different categories: feedback-disabled for regular data transmissions (improving efficiency), but feedback-enabled for control messages like MAC-CE activation/deactivation and SCell activation (maintaining reliability). This segmentation allows the system to optimize different parts of the communication protocol independently based on their specific requirements.
3Reliability
If exception indicators are added via DCI or MAC-CE to override HARQ-ACK-less list, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent uses RRC configuration to pre-define HARQ-ACK-less lists and exception conditions before actual data transmission occurs. This preliminary configuration allows the UE to be pre-prepared with knowledge of which HARQ processes should disable feedback and under what exceptions, reducing the need for complex real-time decision-making during transmission.
Solution Approach 2:
The patent introduces MAC-CE and DCI as intermediary mechanisms that can override the HARQ-ACK-less list configuration when needed. These intermediaries provide a controlled way to enable feedback for specific transmissions without requiring complete reconfiguration of the HARQ processes, simplifying the overall system by maintaining a default disabled state with selective overrides rather than complex per-transmission configuration.
Data Source
AI summary
A communication method performed by a UE includes the UE receiving a HARQ-ACK-less list from a BS, the HARQ-ACK-less list indicating at least one HARQ process in which a HARQ-ACK information transmission for a DL transmission is disabled, wherein the at least one HARQ process is indicated by including a set of HARQ process IDs in the HARQ-ACK-less list; receiving a first MAC CE on a PDSCH from the BS, the PDSCH being associated with a first HARQ process ID in the set of HARQ process IDs; and transmitting HARQ-ACK information for the PDSCH in response to receiving the first MAC CE irrespective of the reception of the HARQ-ACK-less list. A UE using such method is also provided.