Scheduling Command Replication for URLLC Reliability

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Solution Overview

Problem

Current communication technologies face challenges in achieving both high reliability and low latency for Ultra-Reliable and Low-Latency Communications (URLLC) services, as the Block Error Rate (BLER) of downlink control channels is difficult to meet the required 10−6 threshold, especially with the existing channel design in LTE, leading to increased latency and errors if scheduling commands are not received correctly.

Innovation Solution

Transmitting a scheduling command in a first subframe and replicating it in subsequent subframes, using reserved resources or downlink data traffic resources, with an indication of the first subframe, and employing numerologies with the longest duration and smallest bandwidth, associated with Machine Type Communication (MTC) resources, to enhance robustness and diversity gain.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If scheduling commands are transmitted using existing LTE control channel design, then the system maintains compatibility with current standards, but the Block Error Rate cannot meet the required 10^-6 threshold for URLLC services

Engineering Contradiction:

ImproveBlock Error RateVSAvoidcontrol channel design

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The scheduling command transmission is segmented across multiple subframes with multiple replicas transmitted at different times. This segmentation allows the terminal to receive and combine multiple copies of the same command, increasing the probability of successful decoding and achieving the required 10^-6 Block Error Rate for URLLC services.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Replicas of the scheduling command are transmitted in advance in subframes before the actual data transmission subframe. This preliminary transmission ensures that the terminal device has multiple opportunities to receive and decode the scheduling command before the data arrives, improving reliability without requiring complex retransmission protocols.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If scheduling commands are transmitted only in the subframe where downlink data transmission occurs, then the transmission timing is simple, but the reliability is insufficient for URLLC requirements

Engineering Contradiction:

Improvescheduling command receptionVSAvoidcommand transmission delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The scheduling command is transmitted periodically across multiple subframes with regular intervals. This periodic transmission pattern ensures that the terminal device can capture the command at any of the periodic opportunities, reducing the impact of timing misalignment and improving overall reception reliability.

Inventive Principle:

Principle #19Periodic action

3Reliability

If multiple replicas of scheduling commands are transmitted in different subframes, then reliability is improved, but the control channel resource consumption increases

Engineering Contradiction:

Improvescheduling command transmissionVSAvoidcontrol channel resources

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The same control channel resources are reused across multiple subframes to transmit replicas of the scheduling command. This multi-functional use of resources allows the system to achieve improved reliability through repeated transmissions without requiring additional dedicated resources, as each replica uses the same resource pattern in its respective subframe.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

Instead of creating new unique control messages for each transmission, the system creates copies of the same scheduling command replica across multiple subframes. This copying approach minimizes the information content that needs to be transmitted repeatedly, reducing the effective resource consumption compared to transmitting entirely new control messages each time.

Inventive Principle:

Principle #26Copying

4Reliability

If the scheduling command is transmitted with high robustness using current methods, then error rate decreases, but latency increases due to retransmissions

Engineering Contradiction:

Improveerror rateVSAvoidlatency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system rushes through multiple transmission opportunities by sending replicas in consecutive or near-consecutive subframes, allowing the terminal to quickly capture and decode the command without waiting for lengthy retransmission cycles. This approach skips potential error states by providing multiple rapid succession opportunities for successful reception.

Inventive Principle:

Principle #21Skipping (Rushing through)

Data Source

PatentUS11337237B2Methods and devices for transmitting/receiving scheduling commands

Publication Date: 2022.05.17 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

The present disclosure provides a method (200) in an access device for transmitting scheduling commands. The method (200) includes: transmitting (210) a scheduling command for scheduling a downlink data transmission in a first subframe where the downlink data transmission occurs; and transmitting (220) a replica of the scheduling command in each of one or more further subframes different from the first subframe.