Random Access Preamble Transmission in Unlicensed Spectrum

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Solution Overview

Problem

In NR-U systems, user equipment attempting to transmit a random access preamble may cause its own LBT failure due to other users transmitting uplink signals at the same time, leading to a waste of random access resources and reduced probability of successful transmission.

Innovation Solution

The method involves determining an available random access occasion and timing advance value, performing listen before talk (LBT) before the first available random access occasion, and transmitting the random access preamble if LBT is successful, with options for adjusting timing advance values and counters based on failure conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If user equipment transmits random access preamble in unlicensed spectrum, then random access function is achieved, but LBT failure occurs due to other users transmitting uplink signals at the same time

Engineering Contradiction:

Improvesuccessful random access preamble transmissionVSAvoidLBT failure caused by other users' uplink signals

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by performing LBT procedure before the timing advance (TA) of the random access occasion. Specifically, the LBT is executed at time T - TA, where T is the random access occasion timing. This advance LBT allows the UE to detect potential uplink signals from other users before its own transmission, enabling it to identify and avoid resources that would cause self-interference or LBT failure.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements preliminary anti-action by using the advance LBT to detect and preemptively avoid conflicting uplink signals. When the LBT performed before TA detects that other users are transmitting, the UE can select a different random access occasion or adjust its transmission timing, thereby counteracting the harmful interference before it affects the random access preamble transmission.

Inventive Principle:

Principle #9Preliminary anti-action

2Stability of the object's composition

If LBT is performed at normal timing advance, then transmission timing is maintained, but self-LBT failure occurs due to interference from other simultaneous uplink transmissions

Engineering Contradiction:

Improvetransmission timing synchronizationVSAvoidLBT success probability

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent separates the LBT timing from the transmission timing by performing LBT at T - TA while maintaining transmission at T. This preliminary LBT action allows timing synchronization to be preserved for the actual transmission while the earlier LBT provides a clear view of the channel state without being affected by the UE's own upcoming transmission signal.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11968713B2Method and apparatus for transmitting and receiving signal in wireless communication system

Publication Date: 2024.04.23 SAMSUNG ELECTRONICS CO LTD

AI summary

The present disclosure provides a signal transmission/reception method, user equipment, and network equipment, the method including: determining, by a user equipment, an available random access occasion and a timing advance (TA) value; performing listen before talk (LBT) before a TA of the first available random access occasion; transmitting, if the LBT is successful, the random access preamble on the random access occasion.