Uplink Timing Correction in LAA Channel Access

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Solution Overview

Problem

The existing uplink transmission timing adjustment mechanisms in LTE networks, particularly in scenarios involving Licensed Assisted Access (LAA), are inadequate when the UE is configured to transmit but cannot due to channel inaccessibility or LBT failure, leading to undefined behavior and potential interference issues.

Innovation Solution

A method for a wireless device to determine whether an error in uplink transmission timing exceeds a threshold, adjust timing accordingly, and reverse adjustments when LBT assessment indicates non-permission to transmit, ensuring accurate timing adjustments based on LBT success likelihood.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If uplink transmission timing is adjusted based on downlink reception timing in LAA scenarios, then transmission timing accuracy is improved, but interference occurs when LBT fails and the eNB does not see the adjusted timing

Engineering Contradiction:

Improvetransmission timing accuracyVSAvoidinterference

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent implements feedback by having the UE monitor whether its timing adjustments are observed by the eNB through timing advance commands. When the eNB sends a timing advance command, it confirms to the UE that its timing adjustment was seen and validated. This feedback loop prevents the UE from making uncoordinated timing adjustments that could cause interference, while still allowing accurate timing when conditions permit.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent makes the timing adjustment mechanism dynamic by conditionally applying timing adjustments based on LBT success and eNB observation. Rather than continuously adjusting timing, the UE dynamically adjusts timing only when LBT succeeds and the adjustment is confirmed by the eNB through timing advance commands. This dynamic approach balances timing accuracy with interference prevention.

Inventive Principle:

Principle #15Dynamics

2Reliability

If LBT assessment is performed before each transmission opportunity, then channel access reliability is improved, but transmission delays increase due to channel contention

Engineering Contradiction:

Improvechannel access reliabilityVSAvoidtransmission delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by performing LBT assessment before each scheduled uplink transmission opportunity in advance. This ensures that the UE is ready to transmit immediately when the channel becomes available, minimizing actual transmission delays while maintaining reliable channel access through proactive channel sensing.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If timing adjustments are made autonomously by the UE, then timing accuracy is improved, but system coordination is worsened due to undefined behavior in LAA scenarios

Engineering Contradiction:

Improvetiming accuracyVSAvoidsystem coordination

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent resolves the coordination issue by introducing feedback from the eNB through timing advance commands. The UE autonomously adjusts timing based on downlink reception timing, but the eNB validates these adjustments by sending timing advance commands. This feedback mechanism coordinates the autonomous UE behavior with the network, ensuring system-wide timing consistency while maintaining the benefits of autonomous adjustment.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent inverts the traditional timing adjustment approach by having the UE autonomously adjust timing first (rather than waiting for network commands), and then having the network validate and refine these adjustments through timing advance commands. This inversion allows the UE to take initiative in maintaining timing accuracy while the network ensures coordination.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS10716143B2Method and device for timing correction in a channel access using a Listen-Before-Talk protocol

Publication Date: 2020.07.14 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

According to some embodiments, a wireless device maintains timing associated with uplink transmissions by performing steps for each of a plurality of scheduled LBT transmission opportunities. The steps include determining whether an error in a current uplink transmission timing, with respect to a reference point based on a downlink timing for a reference cell, exceeds a predetermined threshold and adjusting the timing associated with uplink transmissions, for each scheduled LBT transmission opportunity for which the error exceeds the predetermined threshold. The steps also include performing an LBT assessment to determine whether the wireless device is permitted to transmit in the scheduled LBT transmission opportunity and, for each scheduled LBT transmission opportunity in which the LBT assessment indicates that the wireless device is not permitted to transmit, reversing any adjustment to the timing associated with uplink transmissions made for that scheduled LBT transmission opportunity.