Uplink PDU Duplication via RLC URLLC Mode Trigger

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Solution Overview

Problem

Current communication networks face challenges in meeting the stringent reliability and low latency requirements for Ultra-Reliable and Low Latency Communication (URLLC) services, as existing retransmission schemes are not optimized for both spectrum efficiency and latency, leading to unnecessary retransmissions and latency constraints.

Innovation Solution

The implementation of an RLC URLLC mode in user equipment, which configures an RLC trigger for uplink PDU duplication, allowing for earlier retransmission of PDUs without relying on feedback, thus optimizing both reliability and latency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If existing retransmission schemes (HARQ, RLC acknowledged mode) are used to ensure reliability, then packet loss probability is reduced, but round trip latency increases due to feedback requirements

Engineering Contradiction:

Improvepacket loss probabilityVSAvoidround trip latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by proactively duplicating PDUs before transmission failures occur. Instead of waiting for feedback to trigger retransmission, the system preemptively sends duplicate copies through different logical channels, ensuring that at least one copy arrives within the stringent latency budget while maintaining high reliability.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If retransmissions are triggered on demand based on feedback (TCP, RLC, MAC layer retransmission schemes), then resource utilization efficiency is improved, but latency cannot be minimized due to round trip time requirements

Engineering Contradiction:

Improveresource utilization efficiencyVSAvoidtransmission delay

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent implements preliminary action by duplicating PDUs in advance based on predicted loss probability thresholds. When the calculated probability of packet loss exceeds a configured threshold, duplicate PDUs are proactively transmitted through alternative logical channels before any failure occurs, eliminating the need for feedback-driven retransmission loops and reducing latency while maintaining efficient resource usage.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If PDCP duplication is applied with maximum four copies on different carriers/frequency bands, then reliability is improved, but device complexity and configuration overhead increase

Engineering Contradiction:

Improvetransmission reliabilityVSAvoidconfiguration overhead

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by implementing selective PDU duplication at the RLC layer based on local conditions (calculated packet loss probability). Instead of uniformly duplicating all PDUs across multiple carriers and frequency bands, the system intelligently determines which PDUs require duplication and selects appropriate logical channels, reducing configuration overhead and device complexity while maintaining high reliability where needed.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent introduces an intermediary mechanism at the RLC layer that sits between the PDCP layer and lower layers. This RLC-layer intermediary calculates packet loss probabilities, makes duplication decisions, and manages logical channel selection, thereby simplifying the overall system architecture and reducing configuration overhead compared to PDCP-layer duplication approaches.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Reliability

If RLC acknowledged mode is used for retransmissions, then reliability is improved through feedback-based retransmission, but latency requirements cannot be met due to feedback loop delays

Engineering Contradiction:

Improveretransmission reliabilityVSAvoidfeedback loop delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by proactively duplicating PDUs before transmission failures occur, rather than waiting for feedback. The system calculates packet loss probability and, when it exceeds a threshold, immediately transmits duplicate PDUs through different logical channels, eliminating the feedback loop delay inherent in RLC acknowledged mode while maintaining high reliability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent inverts the traditional feedback-driven retransmission approach by using feedforward duplication. Instead of relying on feedback to trigger retransmission, the system uses predicted loss probability to proactively send duplicates, reversing the causality between detection and action to eliminate feedback loop latency.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS20240188111A1Duplicate Transmission of Protocol Data Units

Publication Date: 2024.06.06 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

There is provided mechanisms for triggering uplink PDU duplication from a user equipment. A method is performed by a network node. The method comprises configuring the user equipment with an RLC URLLC mode. According to the RLC URLLC mode the user equipment is configured with an RLC trigger for the user equipment to perform uplink PDU duplication for an URLLC service.