Uplink SRS Beam Adjustment in RRC Inactive Positioning
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Solution Overview
Problem
In the RRC inactive state of 5G mobile communication, the gNB cannot timely update the configuration parameters for the SSB reference signal of UE, leading to poor reception of uplink SRS due to UE movement without information exchange, disrupting uplink positioning.
Innovation Solution
A method for a terminal in RRC inactive state to measure candidate reference signals, determine an optimal beam direction and power based on signal parameters, and send positioning assistance information to the serving base station without switching states, using preconfigured and candidate configuration parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the UE remains in RRC inactive state to save power and maintain fast connection restoration, then power consumption is reduced and control plane delay is shortened, but the gNB cannot timely update configuration parameters for SSB reference signal leading to poor uplink SRS reception
Solution Approach 1:
The UE autonomously measures candidate reference signals and determines optimal transmit beams and powers without gNB intervention. The UE self-updates configuration parameters by selecting from pre-configured candidate SSB reference signals based on measurement results, enabling self-service beam management while in RRC inactive state.
Solution Approach 2:
The gNB pre-configures multiple candidate SSB reference signals with different beam directions and powers before the UE enters RRC inactive state. The UE uses these pre-configured candidates for autonomous measurement and selection, eliminating the need for real-time parameter updates during inactive state.
2Reliability
If the UE switches to RRC connected state to update configuration parameters, then uplink SRS reception quality is improved, but power consumption increases and the advantage of fast connection restoration is lost
Solution Approach 1:
The UE performs autonomous beam management by measuring candidate reference signals and selecting optimal transmit parameters without transitioning to RRC connected state. This self-service approach maintains positioning functionality while preserving the power-saving benefits of RRC inactive state.
Solution Approach 2:
The UE changes transmission parameters (beam direction and power) by selecting from pre-configured candidate SSB reference signals based on measured signal qualities. This parameter selection approach enables adaptive beam management without state transition.
3Reliability
If the gNB continuously updates configuration parameters via RRC signaling, then uplink SRS reception quality is maintained, but the complexity of the system increases and the efficiency of RRC inactive state is reduced
Solution Approach 1:
The gNB performs preliminary configuration of multiple candidate SSB reference signals with different beam parameters before the UE enters RRC inactive state. This advance preparation enables the UE to autonomously adapt to channel changes without requiring continuous gNB intervention or frequent state transitions.
Data Source
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Figure 2b~3
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AI summary
A configuration parameter update method and an apparatus are provided. The method includes: when detecting that a first signal power of a first reference signal is less than a preset power, measuring, by a terminal in an RRC inactive state, candidate reference signals corresponding to candidate configuration parameters; determining, from the candidate reference signals, a first candidate reference signal that meets a preset condition, and sending a signal parameter of the first candidate reference signal to a first serving base station; and adjusting a beam direction and/or a transmit power of an uplink SRS based on the first candidate reference signal. According to the method, the terminal in the RRC inactive state adjusts the beam direction of the uplink SRS in a timely manner without switching a status. In addition, a base station participating in positioning may adjust a receive beam of the uplink SRS in a timely manner based on a signal parameter, thereby implementing positioning of the terminal in the RRC inactive state.