PTM HARQ Feedback Delay Scheduling for Larger Multicast Groups
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Solution Overview
Problem
The challenge of supporting large multicast groups in 5G NR transmission is the high demand for Physical Uplink Control Channel (PUCCH) resources due to simultaneous HARQ feedback from all users, leading to potential PUSCH throughput reduction.
Innovation Solution
Implementing methods to spread HARQ feedback in time by configuring different delay times for user equipment (UE) in a multicast group and using varying PDSCH aggregation factors based on radio link quality, allowing UEs to share PUCCH resources and reducing the number of required PUCCH resources per slot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all users in a multicast group send HARQ feedback simultaneously, then reliability of multicast transmission is improved, but PUCCH resource requirement increases significantly
Solution Approach 1:
The patent segments the simultaneous HARQ feedback from all M users into N separate feedback opportunities, where N < M. Users are divided into different groups that send feedback at different time instances or using different resources, thereby reducing the peak PUCCH resource requirement from M to N while still maintaining reliable multicast transmission through distributed feedback collection.
Solution Approach 2:
The patent implements periodic HARQ feedback collection by scheduling feedback from different user groups at different time instances within a feedback window. Instead of requiring all users to feedback simultaneously, the system collects feedback periodically from subsets of users, reducing instantaneous PUCCH resource demand while maintaining overall feedback completeness for reliability assessment.
2Adaptability or versatility
If more PUCCH resources are allocated for HARQ feedback, then more users can be supported in multicast group, but PUSCH throughput decreases due to shared uplink resources
Solution Approach 1:
The patent segments the PUCCH resource allocation across multiple time instances or frequency resources, allowing M users to be supported in the multicast group without requiring M simultaneous PUCCH resources. By distributing feedback requirements over N resource instances where N < M, the system supports larger multicast groups while preserving PUSCH throughput for unicast traffic.
Solution Approach 2:
The patent introduces additional dimensions for HARQ feedback differentiation, such as time instances, frequency resources, or spatial layers, allowing multiple users to share the same PUCCH resource pool. This dimensional expansion enables M users to be supported with N PUCCH resources (N < M) by multiplexing feedback in the introduced dimensions, thereby supporting larger multicast groups without compromising PUSCH throughput.
Data Source
AI summary
Various embodiments of the present disclosure provide a method implemented at a terminal device in a PTM group. The method comprises receiving a message from a network node. The message indicates at least one of: delay information for a Hybrid Automatic Repeat request (HARQ) feedback for a Point to Multipoint (PTM) transmission for the terminal device, a Physical Downlink Shared Channel (PDSCH) aggregation factor for the terminal device, and a HARQ feedback reporting mode for the PTM transmission for the terminal device. The method further comprises determining whether to transmit the HARQ feedback for the PTM transmission based on the message, and/or determining timing information for transmitting the HARQ feedback for the PTM transmission based on the message.