MAC-CE Bitmap Configuration for Low-Latency Beam Failure Recovery

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Solution Overview

Problem

Existing wireless communication technologies face challenges in efficiently recovering from beam failures, particularly in scenarios requiring low latency and high reliability, such as ultra-reliable low-latency communication (URLLC), where current beam failure recovery methods do not meet these demands.

Innovation Solution

Configuring a medium access control control element (MAC-CE) bitmap to indicate beam failure information for serving cells or groups of serving cells, allowing for efficient beam failure recovery without initiating random access channel procedures, by using bits to signify beam failure and new beam indications, and optimizing byte usage with reserved and unused bits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If existing beam failure recovery methods are used, then beam failure can be detected, but recovery latency is high and reliability is insufficient for URLLC scenarios

Engineering Contradiction:

Improvebeam failure recovery reliabilityVSAvoidrecovery latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent pre-configures multiple candidate beams and their corresponding CRI indices before beam failure occurs. When beam failure is detected, the UE can immediately select from pre-configured candidate beams without needing to perform new beam measurement and selection procedures, significantly reducing recovery latency while ensuring reliable connection restoration

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent divides the beam failure recovery process into separate MAC-CE reporting mechanisms for different cell groups (primary cell group and secondary cell group). Each cell group has its own bitmap indicating beam failure status, allowing independent and parallel recovery procedures for different cell groups, thereby reducing overall recovery time and improving reliability

Inventive Principle:

Principle #1Segmentation

2Loss of information

If MAC-CE bitmap is configured to indicate beam failure information for multiple serving cells, then beam failure information coverage is improved, but MAC-CE overhead increases

Engineering Contradiction:

Improvebeam failure information coverageVSAvoidMAC-CE overhead

Core Design Contradiction:

Loss of informationVSQuantity of substance

Solution Approach 1:

The patent designs a universal MAC-CE bitmap structure where each bit position can represent a serving cell or a group of serving cells. The same MAC-CE format can accommodate different numbers of serving cells and different cell group configurations, providing flexible and efficient beam failure information reporting without requiring multiple different message formats, thus controlling overhead while maintaining comprehensive coverage

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS12389255B2Techniques for configuring a MAC-CE bitmap for beam failure recovery

Publication Date: 2025.08.12 QUALCOMM INC

AI summary

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may configure a bitmap in a medium access control control element (MAC-CE) to indicate beam failure information for one or more serving cells or one or more groups of serving cells. The UE may transmit the MAC-CE to a base station via at least one serving cell. Numerous other aspects are provided.