Triggered Random Access in Unlicensed Spectrum

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Solution Overview

Problem

Wireless networks operating in unlicensed radio frequency spectrum bands face challenges in accessing preconfigured random access resources due to unsuccessful listen-before-talk procedures, leading to limited availability of physical random access channel resources.

Innovation Solution

The implementation of triggered random access occasions, where a base station configures user equipment with random access parameters and transmits a downlink control signal to indicate the location and trigger random access occasions, allowing the user equipment to transmit random access signals during designated times and establish connections with the base station.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If preconfigured random access resources are used in unlicensed spectrum, then resource availability is limited due to unsuccessful listen-before-talk procedures, but implementing triggered random access occasions increases system complexity

Engineering Contradiction:

Improverandom access resource availabilityVSAvoidrandom access procedure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent implements dynamic triggering of random access occasions through downlink control signals that indicate specific time-frequency locations where random access may occur. This transforms the static preconfigured approach into a dynamic system that adapts to listen-before-talk outcomes, allowing the base station to trigger random access only when channel conditions permit, thereby improving reliability without permanently increasing complexity

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The base station performs listen-before-talk procedures and prepares triggering decisions in advance before actual random access is needed. By pre-configuring potential random access occasions and having triggering mechanisms ready, the system ensures rapid response when channels become available, improving resource availability while managing complexity through advance preparation

Inventive Principle:

Principle #10Preliminary action

2Reliability

If triggered random access occasions are implemented to increase access opportunities, then random access reliability improves, but signaling overhead and procedure complexity increase

Engineering Contradiction:

Improverandom access opportunity availabilityVSAvoidsignaling overhead

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

Instead of continuously signaling all possible random access occasions, the system uses partial action by triggering only specific occasions when needed. The downlink control signal indicates a subset of pre-configured random access resources, reducing signaling overhead while maintaining reliability by activating only the necessary access opportunities based on current channel conditions

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The random access resources are segmented into multiple pre-configured occasions with different time-frequency locations. The triggering mechanism selectively activates specific segments based on listen-before-talk outcomes, allowing the system to provide multiple access opportunities without signaling all of them continuously, thus reducing overhead while maintaining reliability

Inventive Principle:

Principle #1Segmentation

3Reliability

If random access parameters are configured for each user equipment, then connection establishment reliability improves, but configuration complexity and processing time increase

Engineering Contradiction:

Improveconnection establishment reliabilityVSAvoidconfiguration processing time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent employs universal random access parameters that can be applied across multiple user equipments and scenarios. Instead of configuring unique parameters for each UE, the system uses a set of common parameters that work for all UEs in the cell, reducing configuration complexity and processing time while maintaining connection establishment reliability through the universal applicability of the parameters

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS11445552B2Triggered physical random access channel for new radio unlicensed

Publication Date: 2022.09.13 QUALCOMM INC

AI summary

Methods, systems, and devices for wireless communications are described. A user equipment (UE) may obtain a signal received over a wireless channel, the signal configuring one or more random access parameters for the wireless channel. The UE may obtain a downlink control signal over the wireless channel, wherein the downlink control signal comprises an indication of a trigger and a location of one or more random access occasions for the UE. The UE may output, based at least in part on the downlink control signal, a random access signal for transmission on the wireless channel during at least one of the one or more random access occasions and according to the one or more random access parameters and the location. The UE may establish a connection with a base station based at least in part on the random access signal.