Grouped HARQ Feedback Transmission in LTE-U Networks
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Solution Overview
Problem
In wireless communication systems, particularly in LTE-U networks using listen-before-talk (LBT) mechanisms, the asynchronous nature of clear channel assessments (CCA) and extended CCA (ECCA) can lead to unreliable feedback transmission due to timing issues and resource acquisition challenges, causing burdens on network resources and delays in transmitting hybrid automatic repeat/request (HARQ) feedback.
Innovation Solution
The solution involves grouping feedback for multiple subframes and process identifiers into a single communication, allowing asynchronous transmission triggered by the evolved Node B (eNB), using a feedback tag to synchronize UE and eNB, and transmitting on control or shared data channels, thereby reducing the number of feedback transmissions and conserving network resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HARQ feedback is transmitted according to scheduled LTE grants, then feedback reliability is improved, but channel acquisition delays and resource burdens increase due to LBT mechanisms
Solution Approach 1:
The patent performs preliminary grouping of HARQ feedback for multiple subframes and process identifiers before transmission. By organizing feedback data in advance and preparing it for asynchronous transmission, the system eliminates the need for timing-critical scheduled transmissions, thereby resolving the contradiction between reliability and channel acquisition delay
Solution Approach 2:
The patent implements dynamic feedback transmission timing that adapts to LBT outcomes. Instead of fixed scheduled grants, the system transmits grouped feedback asynchronously based on when the channel becomes available, making the transmission timing flexible and adaptive to random LBT results, thus eliminating channel acquisition delays while maintaining reliability
2Adaptability or versatility
If CCA is executed for each feedback transmission, then channel access compliance is improved, but network resource burden and transmission delay increase
Solution Approach 1:
The patent merges multiple individual feedback transmissions into a single grouped feedback message that contains HARQ acknowledgments for multiple subframes and process identifiers. This consolidation reduces the total number of CCA executions required, thereby improving feedback transmission efficiency while maintaining LBT compliance through asynchronous transmission of the combined feedback
Solution Approach 2:
The patent enables continuous accumulation of feedback data across multiple subframes without interrupting the feedback collection process. By continuously gathering HARQ feedback and transmitting it as a grouped message when the channel becomes available, the system maintains high productivity while ensuring LBT compliance through asynchronous transmission
3Productivity
If feedback is transmitted asynchronously independent of CCA/ECCA completion, then scheduling flexibility is improved, but timing synchronization between UE and eNB may be challenged
Solution Approach 1:
The patent implements a feedback tag mechanism that provides timing and synchronization reference information within the grouped feedback message. This feedback tag allows the eNB to correctly interpret and process the asynchronously received feedback, maintaining timing synchronization accuracy despite the flexible asynchronous transmission timing
Solution Approach 2:
The feedback tag acts as an intermediary element that carries timing reference information between the UE and eNB. This intermediary structure enables the system to bridge the timing gap created by asynchronous transmission, ensuring that the eNB can accurately associate the received feedback with the correct subframes and process identifiers
Data Source
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AI summary
Aspects described herein relate to communicating feedback in a wireless network. An indication to communicate feedback for a plurality of subframes to an access network node can be received from the access network node. A plurality of process identifiers related to transport blocks received in the plurality of subframes can be determined. Feedback for the plurality of process identifiers received in the plurality of subframes can be grouped, and the grouped feedback and/or a feedback tag indicative of the plurality of subframes can be transmitted to the access network node.