MAC CE Latency Control in NTN HARQ Feedback

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Solution Overview

Problem

The long propagation delays in Non-Terrestrial Networks (NTN) lead to insufficient MAC CE latency and inefficiencies in HARQ mechanisms, disrupting UL procedures and causing inconsistencies in MAC CE command application timing due to the lack of consistent reference points for HARQ ACK feedback.

Innovation Solution

Introduce configurable HARQ ACK feedback enabling/disabling on a per-UE and per-HARQ process basis, and define new timing mechanisms for MAC CE command application, including slot offsets and processing delays to harmonize operations regardless of HARQ ACK feedback status.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If HARQ mechanisms are activated to ensure reliable data transmission, then transmission reliability is improved, but latency increases due to re-transmission delays and insufficient MAC CE latency in NTN environments

Engineering Contradiction:

Improvetransmission reliabilityVSAvoidMAC CE latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements dynamic HARQ-ACK feedback control by enabling the network to configure whether HARQ-ACK feedback is required for MAC CE commands on a per-command basis. This dynamic configuration allows the system to switch between feedback-based and feedback-less operations, optimizing the balance between reliability and latency according to specific transmission conditions and MAC CE command types.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent introduces new timing parameters (K_offset, K2_offset, and processing time parameters) that can be configured by the network to adjust MAC CE application timing. These parameter changes enable flexible control over when MAC CE commands are applied, allowing the system to compensate for NTN propagation delays and achieve consistent timing regardless of HARQ-ACK feedback status.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If consistent MAC CE command application timing is implemented across all UEs, then system consistency is improved, but device complexity increases due to additional timing configuration and coordination mechanisms

Engineering Contradiction:

Improvesystem consistencyVSAvoidtiming configuration complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent creates a universal timing mechanism that works for both HARQ-ACK feedback-based and feedback-less operations. The same MAC CE application timing rules and parameter configurations apply regardless of whether HARQ-ACK feedback is enabled or disabled, simplifying the system design by avoiding separate timing mechanisms for different operation modes.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent introduces network-configured offset parameters (K_offset, K2_offset) as intermediaries that mediate between the received MAC CE command and its application timing. These parameters act as configurable buffers that allow the network to control exactly when MAC CE commands are applied, ensuring consistency across all UEs while keeping the implementation straightforward through parameter configuration rather than complex logic.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of time

If HARQ-ACK feedback is disabled to reduce latency, then latency is improved, but reliability deteriorates due to lack of acknowledgment and re-transmission capability

Engineering Contradiction:

ImproveMAC CE latencyVSAvoidcommand application reliability

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

Data Source

PatentEP4042771B1Communication method and apparatus for medium access control (MAC) control element (CE) latency control

Publication Date: 2025.06.25 SHARP KK

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AI summary

A communication method performed by a UE, the communication method comprising: receiving DCI on a PDCCH from a BS, the DCI indicating a PDSCH; receiving a MAC CE command on the PDSCH; determining, according to the DCI, whether a HARQ ACK feedback for a data reception on the PDSCH is needed to be transmitted; applying, after determining that the HARQ ACK feedback is needed to be transmitted, the MAC CE command after a first slot identified by n+K0+K1+Np+M; and applying, after determining that the HARQ ACK feedback is not needed to be transmitted, the MAC CE command after a second slot identified by n+K0+M.