UE Beam Switching via Timer and MAC CE Absence
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Solution Overview
Problem
Current 5G NR wireless communication systems face challenges in handling radio link failures (RLFs) due to the absence of media access control (MAC) control elements, leading to poor user experiences and increased call drops, especially in scenarios where higher path loss and mobility affect beam stability.
Innovation Solution
User equipment (UE) measures synchronization signal block (SSB) beams, selects the highest rated beam based on selection factors, and initiates a timer to perform beam switching if a MAC control element is not received within the timer's expiration, or requests a radio resource control (RRC) reconfiguration message to switch beams, ensuring continuous connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE waits for MAC CE confirmation before switching beams, then the network can control beam switching, but the beam switching delay increases and RLF occurs under high mobility
Solution Approach 1:
The UE performs preliminary beam measurement and identification before RLF occurs, maintaining a candidate beam list and evaluating beams in advance. This allows the UE to quickly switch to a pre-evaluated beam when RLF is detected, avoiding the time-consuming process of beam search during critical moments.
Solution Approach 2:
The UE autonomously performs beam measurement, evaluation, and switching without waiting for network confirmation (MAC CE). The UE independently monitors beam quality metrics, identifies deteriorating beams, and executes beam switching based on pre-configured criteria, reducing dependency on network response time.
2Loss of time
If the UE performs autonomous beam switching without MAC CE, then beam switching speed increases, but beam switching accuracy may decrease
Solution Approach 1:
The UE performs comprehensive beam measurement and evaluation in advance, building a candidate beam list with detailed quality metrics before autonomous switching is needed. This preliminary analysis ensures accurate beam selection even when rapid switching is required.
Solution Approach 2:
The UE continuously monitors beam quality metrics and provides feedback to itself for beam evaluation. This ongoing feedback mechanism allows the UE to maintain accurate knowledge of beam conditions and make precise switching decisions based on real-time measurements.
3Reliability
If the network sends MAC CE for beam confirmation, then beam switching control is improved, but the signaling overhead increases
Solution Approach 1:
The UE independently performs beam measurement, evaluation, and switching without requiring network confirmation via MAC CE. This self-service approach eliminates the need for additional downlink signaling for beam confirmation, reducing signaling overhead while maintaining beam switching functionality.
Solution Approach 2:
The network provides preliminary beam configuration and measurement criteria to the UE in advance through RRC signaling. This allows the UE to autonomously execute beam switching based on pre-configured parameters, eliminating the need for continuous network confirmation and reducing ongoing signaling overhead.
Data Source
AI summary
In an aspect, the present disclosure includes a method, apparatus, and computer readable medium for wireless communications at a user equipment (UE) for measuring one or more synchronization signal block (SSB) beams from a network entity; selecting a highest rated SSB beam from the one or more SSB beams based on one or more selection factors; transmitting, to the network entity, a beam report including an identification of the highest rated SSB beam; initiating a timer in response to transmitting the beam report; determining whether a media access control (MAC) control element (CE) is received from the network entity before expiration of the timer; and performing beam switching from a current SSB beam to the highest rated SSB beam based on a determination that the MAC CE is not received from the network entity before expiration of the timer.