PUCCH Carrier Switching and Repetition for URLLC Latency
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Solution Overview
Problem
Current frameworks for HARQ-ACK information transmission in mobile communications, particularly for URLLC, face challenges in reducing latency and enhancing reliability due to limitations in PUCCH resource allocation and cross-carrier scheduling, especially in TDD systems with asymmetric traffic patterns.
Innovation Solution
Implementing PUCCH carrier/cell switching and repetitions with dynamic or semi-static cross-carrier scheduling to align uplink slots across different carriers, reducing latency and improving UCI transmission reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple HARQ-ACK feedbacks are accumulated and multiplexed in a single PUCCH resource, then transmission efficiency is improved, but transmission latency increases
Solution Approach 1:
The patent segments the PUCCH transmission by introducing PUCCH repetition, where multiple PUCCH messages are transmitted in different slots. Each slot can carry a portion of the HARQ-ACK feedback, allowing the UE to transmit feedback more quickly without accumulating all feedback in a single resource, thus reducing latency while maintaining efficiency.
Solution Approach 2:
The patent applies preliminary action by enabling the UE to transmit PUCCH repetitions in advance of the final feedback deadline. By spreading out the transmission of multiple PUCCH messages across multiple slots, the system can start transmitting feedback earlier and complete the transmission before the required deadline, reducing the effective latency.
2Loss of time
If PUCCH carrier switching is implemented to reduce alignment delay, then transmission latency is reduced, but device complexity increases
Solution Approach 1:
The patent implements dynamic PUCCH carrier switching where the selected PUCCH carrier can change based on the scheduling DCI. The network can dynamically indicate which carrier should be used for PUCCH transmission, allowing the system to adapt to different traffic patterns and carrier configurations. This dynamic approach reduces alignment delay by selecting the optimal carrier for each transmission opportunity.
Solution Approach 2:
The patent changes the carrier parameter dynamically based on the scheduling decision. When a carrier switching indication is received in the DCI, the system changes the PUCCH carrier from the default carrier to the indicated carrier. This parameter change allows the system to align transmissions across different carriers more effectively, reducing alignment delay without requiring complex static reconfiguration.
3Productivity
If cross-carrier scheduling is used to balance loads across carriers, then transmission efficiency is improved, but control reliability requirements become stricter
Solution Approach 1:
The patent incorporates feedback mechanisms where the UE reports carrier information and PUCCH carrier selection to the network. This feedback loop allows the network to verify that the selected carrier and scheduling configuration are appropriate, ensuring control reliability is maintained while cross-carrier scheduling improves transmission efficiency. The feedback ensures that any carrier switching or load balancing decisions are validated.
Data Source
AI summary
Various solutions for PUCCH carrier switching and PUCCH repetition with respect to user equipment and network apparatus in mobile communications are described. An apparatus may receive downlink control information (DCI) on a physical downlink control channel (PDCCH) configuring a carrier switching indication and a PUCCH repetition indication. The apparatus may receive downlink data on a physical downlink shared channel (PDSCH). The apparatus may perform a PUCCH carrier switching or a PUCCH cell switching according to the carrier switching indication when transmitting uplink control information (UCI) corresponding to the downlink data. The apparatus may perform a PUCCH repetition by retransmitting the UCI according to the PUCCH repetition indication.