Beam Failure Recovery Random Access for Narrow-Beam Mobility

Resolve Bottlenecks,
Find Innovative Solutions
Generate Solutions

Solution Overview

Problem

In wireless communication systems, beam failure can occur when user equipment (UE) moves out of the coverage of a narrow beam, leading to inefficiencies in data scheduling and control channel detection, which existing random access procedures struggle to address effectively.

Innovation Solution

A specific random access configuration is implemented for beam failure recovery, optimizing parameters such as maximum preamble transmission attempts, RAR window size, and contention free random access resources to enhance the success and reduce the delay of beam recovery.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If beamforming is used to improve coverage and data rate, then SINR is improved, but beam coverage becomes narrow causing beam failure when UE moves

Engineering Contradiction:
ImproveSINRVSAvoidbeam coverage
Core Design Contradiction:
ReliabilityVSAdaptability or versatility

Solution Approach 1:

The system dynamically switches between beamformed communication and random access procedures based on beam quality. When beam failure is detected, the system transitions to a dynamic random access process that selects from multiple candidate beams, allowing the communication system to adapt to changing channel conditions and UE movement patterns.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of beam selection by introducing multiple candidate beams with different spatial directions. The system modifies the communication parameters by switching from a single fixed beam to a set of alternative beams, enabling the system to adapt when the primary beam becomes inadequate.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If existing random access procedures are used for beam failure recovery, then beam recovery can be attempted, but success rate is low and delay is high

Engineering Contradiction:
Improvebeam recovery success rateVSAvoidbeam recovery delay
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The system performs preliminary actions by pre-configuring multiple candidate beams and their associated random access resources before beam failure occurs. When beam failure is detected, the UE can immediately utilize the pre-prepared candidate beams without needing to search for new beams, thereby reducing recovery delay and increasing success rate.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent introduces candidate beams as intermediaries between the failed beam and the UE. These candidate beams serve as alternative pathways that the UE can use to re-establish communication, acting as a mediator that facilitates faster and more reliable beam recovery compared to traditional random access procedures.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Productivity

If narrow beam is used to improve data rate, then SINR increases, but UE may suddenly go out of coverage leading to beam failure

Engineering Contradiction:
Improvedata rateVSAvoidcoverage continuity
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The system maintains high data rates through narrow beamforming while dynamically monitoring beam quality and having ready alternative candidate beams. This dynamic approach allows the system to switch quickly when coverage is lost, maintaining both high productivity and reliability by combining narrow beam benefits with fast recovery capabilities.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent prepares cushioning measures by configuring multiple candidate beams in advance. These candidate beams act as a safety buffer that prevents complete communication failure when the primary narrow beam becomes inadequate, thereby cushioning against the loss of coverage continuity while maintaining high data rates during normal operation.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentEP3669602B1Random access for beam failure recovery
Publication Date: 2025.12.17 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
  • EP3669602B1 patent drawingFigure 1
  • EP3669602B1 patent drawingFigure 2
  • EP3669602B1 patent drawingFigure 3~4

AI summary

A method for random access for beam failure recovery is disclosed. In the method, specific random access configuration for the beam failure recovery is received. In the event of a beam failure, a random access procedure is performed according to the specific random access configuration.