MAC-PHY Layer Conflict Handling for Uplink PDU Retransmission

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Solution Overview

Problem

In wireless communication systems, particularly in 5G and LTE, the PHY layer often experiences conflicts due to differences in priority handling between the MAC and PHY layers, leading to preempted PDU transmissions, where higher-priority grants are de-prioritized at the PHY layer due to ongoing or preparation-phase transmissions.

Innovation Solution

The PHY layer in user equipment (UE) sends a 'failure' indication to the MAC layer when a conflict occurs, triggering a retransmission procedure using the next configured grant occasion, allowing recovery of PDUs that the PHY layer was unable to transmit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the PHY layer transmits higher-priority PDUs preemptively, then transmission reliability is improved, but transmission conflicts and PDU losses occur due to timing conflicts with pre-scheduled grants

Engineering Contradiction:

Improvetransmission reliabilityVSAvoidtransmission conflicts

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The system performs preliminary prioritization at the MAC layer before PHY layer transmission. The MAC layer identifies higher-priority PDUs in advance and triggers retransmission procedures for lower-priority PDUs before the conflict occurs, preventing PDU loss while allowing preemptive transmission at PHY layer

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback mechanisms where the PHY layer reports transmission status and conflicts back to the MAC layer. The MAC layer uses this feedback to manage retransmissions and adjust scheduling decisions, ensuring that preemptive transmissions don't cause permanent data loss

Inventive Principle:

Principle #23Feedback

2Productivity

If the MAC layer implements intra-UE prioritization, then communication efficiency is improved, but complexity increases due to MAC-PHY layer interaction and retransmission procedures

Engineering Contradiction:

Improvecommunication efficiencyVSAvoidlayer interaction complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The system segments the prioritization function across different layers: the MAC layer handles high-level prioritization decisions and retransmission management, while the PHY layer handles actual transmission and conflict detection. This segmentation allows each layer to focus on specific tasks, improving overall efficiency while distributing complexity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The MAC layer is designed to perform multiple functions including prioritization, retransmission management, and coordination with PHY layer. This multi-functionality reduces the need for separate dedicated mechanisms, thereby improving efficiency without proportionally increasing complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS11595974B2Intra-user equipment traffic prioritization on uplink with medium access control-physical (MAC-PHY) layer interaction

Publication Date: 2023.02.28 QUALCOMM INC

AI summary

A method of wireless communication by a UE (user equipment) includes receiving, from a MAC (media access control) layer, a first configured grant PDU (protocol data unit). The method also includes receiving, from the MAC layer, a second configured grant PDU. The method also includes determining whether a conflict exists between the first configured grant PDU and the second configured grant PDU. The method further includes triggering, at the MAC layer, a retransmission procedure for the second configured grant PDU when the conflict exists. The triggering can occur in response to receiving a message indicating failure to send.