Group Acknowledgement Buffering for Reliable Uplink Feedback
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Solution Overview
Problem
In wireless communication systems, particularly in LTE, transmitting HARQ feedback and CSI can be unreliable due to unclear channel assessments and the unavailability of uplink subframes, leading to potential loss of feedback in both licensed and unlicensed spectra.
Innovation Solution
Implementing a method where the UE buffers CSI and ACK/NACKs as a GACK until a DCI trigger is received from the eNB, allowing reliable communication even if clear channel assessment does not clear or specific uplink subframes are not available, by monitoring and responding to the DCI trigger in subsequent subframes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If HARQ feedback and CSI are transmitted in predetermined uplink subframes, then the transmission schedule is simple and fixed, but the transmission reliability deteriorates when clear channel assessment does not clear or uplink subframes are unavailable
Solution Approach 1:
The UE buffers HARQ feedback and CSI in advance before the predetermined uplink subframe, so that when the subframe becomes available or when a trigger is received, the feedback is already prepared and can be transmitted immediately, ensuring reliability without complex scheduling
Solution Approach 2:
The eNB sends a DCI trigger signal to dynamically indicate when the UE should transmit buffered feedback. This feedback mechanism allows the system to adapt to changing channel conditions and subframe availability while maintaining transmission reliability
2Ease of operation
If periodic CSI feedback is configured to transmit every 20ms, then the feedback timing is regular and predictable, but the reliability deteriorates when no uplink subframe is configured for CSI feedback
Solution Approach 1:
The UE buffers CSI reports in advance according to the periodic schedule, so when an uplink subframe becomes available or a trigger is received, the CSI is already prepared and can be transmitted immediately, maintaining both predictability and reliability
Solution Approach 2:
The system combines periodic buffering with dynamic triggering. While the buffering follows a predictable periodic pattern, the actual transmission is dynamically adjusted based on uplink subframe availability and eNB triggers, resolving the contradiction between predictability and reliability
3Reliability
If the UE waits for clear channel assessment to clear before transmitting feedback, then the transmission is reliable, but the time delay increases and feedback may be lost if uplink subframes are unavailable
Solution Approach 1:
The UE performs preliminary buffering of feedback data before the channel is cleared and before the uplink subframe arrives. This allows the UE to prepare the feedback in advance and transmit it as soon as the channel becomes available, minimizing delay while maintaining reliability
Solution Approach 2:
By buffering the feedback in advance, the system creates a cushion that protects against channel unavailability and subframe mismatches. The buffered feedback ensures that even if the channel assessment fails or uplink subframes are unavailable, the feedback can still be transmitted through alternative means, reducing time loss and maintaining reliability
Data Source
AI summary
In the present disclosure, CSI and/or a plurality of ACK/NACKs related to a group of DL data transmissions may be buffered at the UE as a GACK until a DCI trigger is received from the eNB. When the DCI trigger is received, the UE may transmit the CSI and/or GACK. In this way, HARQ feedback and/or CSI may be reliably communicated even if a CCA does not clear and/or UL subframes are unavailable. In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. In an aspect, the apparatus may be a UE. The apparatus monitors one or more subframes for a DCI trigger. In a further aspect, the apparatus receives the DCI trigger in a subframe. In another aspect, the apparatus transmits UCI using a subsequent subframe.