MBS SPS Configuration Using Timer Feedback for Grant Confirmation

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Solution Overview

Problem

The challenge in 5G NR multicast and broadcast services is the inability to reliably distinguish between ACK and DTX errors in group-common NACK-only HARQ feedback, leading to uncertainty about successful SPS grant reception by UEs, especially in large audiences.

Innovation Solution

Implementing a timer-based mechanism at the UE to send a message indicating failed SPS activation, allowing the network to retransmit the SPS configuration, ensuring reliable SPS activation and deactivation through minimal uplink resources.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If group-common NACK-only HARQ feedback is used for multicast and broadcast services, then control signaling overhead is reduced, but the ability to reliably distinguish between ACK and DTX errors is lost

Engineering Contradiction:

Improvecontrol signaling overheadVSAvoidreliability of SPS grant reception confirmation

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent introduces a timer-based feedback mechanism where the UE starts a timer upon receiving SPS configuration and stops it upon receiving activation information. If the timer expires without receiving activation, the UE sends a failure message to the network, providing reliable feedback about SPS grant reception status without requiring continuous HARQ feedback signaling.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The UE autonomously monitors for SPS activation information within the timer period and self-determines whether to send a failure message based on whether activation information is received, eliminating the need for network-controlled feedback scheduling while ensuring reliable confirmation.

Inventive Principle:

Principle #25Self-service

2Reliability

If timer-based mechanism with failure messages is implemented, then reliability of SPS activation confirmation is improved, but uplink signaling resources are consumed

Engineering Contradiction:

Improvereliability of SPS activation confirmationVSAvoiduplink signaling resources

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

Instead of requiring continuous or frequent feedback signaling, the patent uses a timer-based approach where feedback (failure messages) is sent only partially - specifically when the timer expires without receiving activation information. This reduces uplink signaling resources compared to continuous feedback mechanisms while maintaining reliability.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The failure message is a lightweight, simple uplink signaling element that is disposed of after delivering its confirmation purpose. It uses minimal uplink resources (a single message rather than sustained signaling) to achieve the reliability goal, treating the signaling resource as a cheap, disposable element used only when necessary.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS12526608B2Reliable SPS configuration for MBS

Publication Date: 2026.01.13 NOKIA TECHNOLOGIES OY

AI summary

Embodiments of the present disclosure relate to reliable SPS configuration for MBS. In the solution, a first device starts a first timer upon receiving, from a second device, configuration of a semi-persistent scheduling (SPS) for a multicast and broadcast service (MBS). Then if the first timer expires and there is no information received to activate corresponding SPS scheduled transmissions, the first device transmits to the second device a message indicating that the first device failed to receive the information. This solution allows reliable SPS configuration for MBS.