HARQ-ACK Feedback Switching to Mitigate Unlicensed NR LBT Blockage
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Solution Overview
Problem
In standalone New Radio (NR) systems operating on unlicensed bands, the timing-based HARQ-ACK feedback is prone to failure due to Listen Before Talk (LBT) blockage, as there is no licensed band involved for feedback, leading to inefficiencies in HARQ-ACK transmission.
Innovation Solution
Implementing a method where a network device transmits first and second triggers to manage HARQ-ACK feedback on unlicensed bands, allowing for trigger-based or timing-based modes, and employing Clear Channel Assessment (CCA) to reduce LBT failures, with mechanisms for resource allocation and encoding to ensure efficient HARQ-ACK transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If timing-based HARQ-ACK feedback is used on unlicensed bands, then the feedback mechanism is simple, but the transmission reliability deteriorates due to LBT blockage
Solution Approach 1:
The patent implements dynamic switching between timing-based and trigger-based HARQ-ACK feedback modes. The network device can adaptively select the appropriate feedback mode based on channel conditions and LBT success, transforming a static timing-based mechanism into a dynamic system that responds to real-time channel state, thereby resolving the contradiction between simplicity and reliability
Solution Approach 2:
The patent introduces trigger signals as intermediary elements between the network device and terminal device. These triggers mediate the HARQ-ACK feedback process by allowing the network device to request feedback at appropriate times after successful LBT, separating the uplink grant transmission from the HARQ-ACK feedback timing and thus improving transmission reliability without significantly increasing system complexity
2Reliability
If trigger-based HARQ-ACK feedback is implemented, then the transmission reliability improves, but the device complexity increases
Solution Approach 1:
The patent designs a universal feedback mechanism that can operate in both timing-based and trigger-based modes using the same underlying framework. The network device and terminal device maintain consistent processing logic for both modes, reducing the incremental complexity of implementing trigger-based feedback while gaining its reliability benefits
Solution Approach 2:
The patent implements preliminary configuration of feedback parameters and resources before actual HARQ-ACK transmission. The network device pre-configures terminal devices with feedback resources, timing relationships, and trigger conditions, so that when trigger-based feedback is activated, the devices can execute the protocol efficiently without complex real-time decision-making, thereby limiting the increase in device complexity
3Reliability
If LBT is performed before HARQ-ACK transmission, then the transmission reliability improves, but the transmission delay increases
Solution Approach 1:
The patent maintains continuous monitoring of channel conditions and keeps feedback resources pre-configured and ready. When LBT succeeds, the network device can immediately transmit triggers and terminal devices can promptly send HARQ-ACK feedback without needing to re-establish connections or reconfigure resources, thus minimizing the time penalty of LBT while ensuring reliable transmission
Solution Approach 2:
The patent performs preliminary setup of feedback resources, timing relationships, and transmission parameters before LBT is executed. This pre-configuration allows the system to quickly transition from LBT completion to actual feedback transmission, reducing the effective delay introduced by LBT while maintaining the reliability benefits of channel access assessment
Data Source
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AI summary
Embodiments of the disclosure generally relate to feedback of a HARQ acknowledgement. A network device transmits, to a terminal device, a first trigger indicating a feedback mode of a HARQ acknowledgement. The feedback mode is selected from at least one of: a trigger mode, a timing mode, and a mixed mode. In response to successful access to an unsilenced band allocated to the HARQ acknowledgement, the network device transmits, to the terminal device, a second trigger indicating at least one target terminal device that is to feedback the HARQ acknowledgement based on the feedback mode indicated by the first trigger.