Random Access Latency Reduction in Unlicensed Spectrum

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Solution Overview

Problem

The two-step random access procedure in wireless communication networks experiences increased latency when performed in unlicensed frequency spectrum, due to unsuccessful clear channel assessments.

Innovation Solution

The method involves selecting an occasion or resource unit for transmitting a payload based on specific criteria, such as priority and timing gaps, to reduce the number of clear channel assessments required, thereby minimizing latency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If two-step random access procedure is performed in unlicensed frequency spectrum, then random access latency is reduced, but clear channel assessment failures increase

Engineering Contradiction:

Improverandom access latencyVSAvoidclear channel assessment success rate

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The network node pre-configures multiple occasions for payload transmission with different time gaps to the random access preamble. The wireless device selects an occasion based on whether it can perform single or multiple clear channel assessments, thereby preliminarily determining the transmission strategy to balance latency and reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces a time gap parameter between random access preamble and payload transmission occasions. By adjusting this time gap parameter, the system changes the clear channel assessment requirements - smaller gaps enable single assessment while larger gaps require multiple assessments, thus adapting to different reliability requirements

Inventive Principle:

Principle #35Parameter changes

2Productivity

If payload transmission occasion is selected with small time gap to random access preamble, then single clear channel assessment is enabled, but transmission reliability may decrease

Engineering Contradiction:

Improveclear channel assessment efficiencyVSAvoidtransmission success rate

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The wireless device dynamically selects between different payload transmission occasions based on its capability to perform clear channel assessments. The selection is not fixed but adapts to the device's operational state and capability, enabling optimal balance between efficiency and reliability

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent segments the payload transmission opportunities into multiple occasions with different time gap characteristics. This segmentation allows the system to offer different reliability- efficiency trade-offs, with the wireless device selecting the appropriate segment based on its capabilities and requirements

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS12267877B2Random access to a wireless communication network

Publication Date: 2025.04.01 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A wireless device selects an occasion or resource unit to use for transmitting a payload within a slot that is the same as or immediately after a slot in which the wireless device transmits a random access preamble for random access to a wireless communication network. The occasion or resource unit is selected based on one or more selection criteria. The one or more selection criteria may include a type, purpose, and/or priority of the random access, of an event that triggered the random access, or of the payload. Alternatively or additionally, the one or more selection criteria may include a capability of the wireless device to transmit both the random access preamble and the payload based on the same clear channel assessment. Regardless, the wireless device transmits the payload using the selected occasion or resource unit.