CSI-RS/TRS Paging Synchronization for Idle NR User Equipment

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Solution Overview

Problem

In 5G/NR networks, mobile devices in reduced power states like RRC_IDLE or RRC_INACTIVE face significant power/energy consumption when waking up to monitor SSBs for paging, leading to increased battery drain due to prolonged 'awake' times until the Paging Occasion arrives.

Innovation Solution

User devices receive resource information for CSI-RS and TRS, exit reduced power state to synchronize with the base station, receive downlink control information, and determine if there is paging information, initiating a RACH procedure if necessary, returning to the reduced power state if no information is found, and optionally receiving SIBs or PDCCH messages for CSI-RS and TRS configuration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If user devices wake up to monitor SSBs for paging in reduced power states, then paging reception capability is improved, but power consumption increases significantly

Engineering Contradiction:
Improvepaging reception capabilityVSAvoidpower consumption
Core Design Contradiction:
ReliabilityVSUse of energy by moving object

Solution Approach 1:

The network provides CSI-RS/TRS resource information to UEs in advance before the paging occasion. UEs can perform preliminary synchronization and channel estimation using these reference signals, so that when the actual paging occasion arrives, the UE is already prepared and does not need to wake up early or stay awake longer, thus reducing power consumption while maintaining reliable paging reception

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

CSI-RS and TRS serve as intermediary reference signals between the SSB and the paging message. Instead of directly monitoring SSBs which require full wake-up, the UE uses CSI-RS/TRS as intermediate steps to achieve synchronization and channel estimation, reducing the need for prolonged SSB monitoring and lowering power consumption

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If user devices stay awake to monitor paging occasions, then paging message detection is improved, but battery life deteriorates

Engineering Contradiction:
Improvepaging message detectionVSAvoidbattery life
Core Design Contradiction:
ReliabilityVSDuration of action of stationary object

Solution Approach 1:

UEs perform synchronization and channel estimation in advance using CSI-RS/TRS before the paging occasion. This preliminary action ensures that when the paging occasion arrives, the UE is already synchronized and can quickly detect the paging message without needing to extend its awake time, thereby preserving battery life

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The invention changes the operational parameters by introducing CSI-RS and TRS with specific configurations (periodicity, time offsets, frequency resources) that allow UEs to achieve the same synchronization and channel estimation goals with shorter awake durations compared to traditional SSB-only monitoring, thus extending battery life

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP4169311B1Systems and methods to receive CSI-RS/TRS indication by idle/inactive mode ues for improved paging reception
Publication Date: 2026.02.11 APPLE INC
  • EP4169311B1 patent drawingFigure 1~2
  • EP4169311B1 patent drawingFigure 3~4
  • EP4169311B1 patent drawingFigure 5~6

AI summary

An example method for wireless communication includes: receiving, by a user device in a reduced power state, resource information for receiving a channel state information reference signal (CSI-RS) and tracking reference signal (TRS); exiting the reduced power state to receive the CSI-RS and TRS, based on the resource information; synchronizing with a base station, based on the received CSI-RS and TRS, to receive a downlink control information message; receiving paging information in a first physical downlink shared channel (PDSCH) transmission based on the received downlink control information message; determining whether there is paging information in the first PDSCH transmission for the user device; starting a Random Access Channel (RACH) procedure to make a Radio Resource Control (RRC) connection, based on determining that there is paging information for the user device; and returning to the reduced power state, based on determining that there is not paging information for the user device.