HARQ Process ID Determination for Configured Grant Retransmission
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Solution Overview
Problem
In 5G wireless communication systems, when Listen-Before-Talk (LBT) fails or Cyclic Redundancy Check (CRC) fails for Configured Grant (CG) Physical Uplink Shared Channel (PUSCH) transmissions, the Node B (gNB) cannot schedule dynamic retransmissions due to lack of knowledge about the Hybrid Automatic Repeat Request (HARQ) process identifier (HPID) selected by the User Equipment (UE), leading to delayed retransmissions and initial transmissions.
Innovation Solution
The proposed solution involves the gNB transmitting Downlink Control Information (DCI) that includes a field indicating the CG configuration index for HARQ retransmissions, allowing the UE to determine the correct HPID and initiate retransmissions autonomously, and the gNB monitoring for HARQ retransmissions from the UE.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gNB schedules dynamic retransmission for CG-PUSCH transmission, then retransmission reliability is improved, but the gNB cannot determine the HPID selected by the UE for the CG-PUSCH transmission
Solution Approach 1:
The patent implements feedback by having the UE transmit HARQ-ACK information on the CG-UCI to indicate the HPID selected for the CG-PUSCH transmission. The gNB uses this feedback to determine which HARQ process failed and schedules appropriate dynamic retransmissions. This resolves the contradiction by enabling the gNB to obtain HPID information through UE feedback.
Solution Approach 2:
The patent introduces CG-UCI as an intermediary carrier to transmit HPID information. Instead of directly exchanging HPID between gNB and UE, the system uses CG-UCI as a mediator channel where the UE reports its selected HPID. This intermediary mechanism enables the gNB to identify the failed HARQ process without direct HPID sharing.
2Loss of time
If the UE autonomously retransmits on the next available CG resource, then retransmission delay is reduced, but the gNB cannot schedule dynamic retransmission without knowing the HPID
Solution Approach 1:
The patent applies preliminary action by having the UE pre-select and report its HPID choice through CG-UCI before the gNB needs to schedule retransmission. This advance information allows the gNB to quickly schedule dynamic retransmissions without waiting for additional signaling, reducing overall retransmission delay while maintaining reliability.
Solution Approach 2:
The UE provides feedback about its selected HPID through CG-UCI, enabling the gNB to make informed scheduling decisions. This feedback mechanism allows the gNB to balance between autonomous UE retransmission (low delay) and scheduled gNB retransmission (high reliability) based on the reported HPID information.
3Reliability
If the gNB monitors for HARQ retransmission from the UE, then retransmission reliability is improved, but the system requires additional signaling overhead
Solution Approach 1:
The patent makes the CG-UCI multi-functional by using it both for its original purpose (carrying uplink control information) and for reporting HPID information. This universal use of existing signaling resources enables HPID feedback without adding separate dedicated signaling channels, thus improving reliability while minimizing additional overhead.
Solution Approach 2:
The patent recovers existing CG-UCI signaling resources to carry additional HPID information. Instead of discarding the limited signaling capacity or adding new overhead, the system repurposes existing CG-UCI structures to convey multiple pieces of information efficiently, reducing the net increase in signaling overhead.
Data Source
AI summary
Apparatuses, methods, and systems are disclosed for dynamic retransmission for a failed configured grant (CG) transmission. One method includes receiving, at a UE, downlink control information (DCI) scheduling uplink resources for a hybrid automatic repeat request (HARQ) retransmission at a first time-instance, where the DCI includes a first field indicating a CG configuration index. The method includes determining, by the UE, a HARQ process identifier (HPID) based on the CG configuration index signaled within the DCI and triggering, at the UE, a HARQ retransmission for a HARQ process corresponding to the determined HPID.