HARQ-ACK Transmission for Multicast PDSCH Retransmission Control
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Solution Overview
Problem
In future radio communication systems like NR, the method for user terminals to transmit Hybrid Automatic Repeat reQuest Acknowledgment (HARQ-ACK) in response to Physical Downlink Shared Channel (PDSCH) using multicast has not been sufficiently studied, leading to potential throughput reduction.
Innovation Solution
A terminal with a receiving section for initial transmission of downlink data scheduled by first DCI and a control section for retransmission based on second DCI, allowing appropriate HARQ-ACK transmission for multicast PDSCH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multicast PDSCH is used for high capacity communication, then system capacity is improved, but HARQ-ACK transmission control becomes insufficient leading to throughput reduction
Solution Approach 1:
The patent segments HARQ-ACK transmission into two distinct paths: initial transmission uses multicast PDSCH for high capacity, while retransmission uses unicast PDSCH for reliable control. This segmentation allows each transmission type to use the most appropriate method, resolving the contradiction between capacity and control reliability.
Solution Approach 2:
The system dynamically switches between multicast and unicast modes based on transmission requirements. The terminal determines whether to use multicast or unicast retransmission based on decoding results of the initial multicast transmission, enabling adaptive control that maintains both high capacity and reliable HARQ-ACK transmission.
2Reliability
If unicast retransmission is used for multicast PDSCH, then HARQ-ACK control is improved, but system complexity increases
Solution Approach 1:
The terminal autonomously determines whether to use unicast retransmission based on its own decoding results of the multicast PDSCH. The control section automatically switches between multicast and unicast modes without requiring complex network coordination, reducing system complexity while maintaining reliable HARQ-ACK control.
3Productivity
If HARQ-ACK transmission method is not controlled, then system simplicity is maintained, but throughput is reduced
Solution Approach 1:
The patent changes the transmission mode parameter dynamically - switching from multicast to unicast based on decoding results. This parameter change enables the system to optimize throughput by selecting the appropriate transmission mode without requiring complex control mechanisms, as the switch is triggered automatically by decoding performance.
Data Source
AI summary
A terminal according to an aspect of the present disclosure includes a receiving section that receives an initial transmission of downlink (DL) data, the DL data being scheduled based on first downlink control information (DCI) and multicasted, and a control section that controls reception of a retransmission of the DL data based on a result of decoding the initial transmission, the DL data being scheduled based on second DCI and unicasted. According to an aspect of the present disclosure, a HARQ-ACK in response to a multicast PDSCH can be appropriately transmitted.