SSB QCL Configuration for NR CDRX Synchronization

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Solution Overview

Problem

In New Radio (NR) communication systems, user equipment (UE) experiences large frequency and timing errors upon waking up from long-duration discontinuous reception (DRX) or connected DRX operation, impacting downlink control information and physical downlink shared channel decoding, and the removal of 'always on' signals like CRS complicates timing and frequency estimation.

Innovation Solution

The implementation of quasi co-location (QCL) configurations between synchronization signal blocks (SSBs) and tracking reference signals (TRS) allows UE to estimate and combine frequency and timing errors, with non-uniform SSB periodicity for enhanced synchronization, including more frequent SSB transmission when close to wake-up, to quickly and accurately synchronize with the network.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If UE sleeps for long duration during DRX or CDRX operation to save power, then power consumption is reduced, but frequency and timing error increases upon waking up

Engineering Contradiction:

Improvepower consumptionVSAvoidfrequency and timing error

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

The base station transmits SSBs with enhanced periodicity (more frequent transmissions) before the scheduled DRX/CDRX wake-up time. This preliminary action allows the UE to perform frequency and timing synchronization in advance, combining measurements from multiple SSBs to estimate and compensate for expected frequency and timing errors before actually waking up, thus resolving the contradiction between power saving and synchronization accuracy

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The UE performs measurements on multiple SSBs transmitted with enhanced periodicity and combines these measurements to estimate frequency and timing errors. This feedback mechanism allows the UE to continuously refine its synchronization parameters before wake-up, ensuring accurate frequency and timing estimation even after long sleep durations, thereby maintaining measurement precision while conserving power

Inventive Principle:

Principle #23Feedback

2Measurement precision

If SSB transmission periodicity is increased to improve synchronization accuracy, then frequency and timing estimation improves, but signaling overhead and network resource consumption increases

Engineering Contradiction:

Improvefrequency and timing estimationVSAvoidsignaling overhead

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The base station applies different SSB transmission periodicities for different time periods and locations. Specifically, SSBs are transmitted with enhanced periodicity only during the window before scheduled DRX/CDRX wake-up times when synchronization is critical, while using normal periodicity at other times. This localized enhancement improves frequency and timing estimation accuracy when needed without unnecessarily increasing overall signaling overhead and network resource consumption

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS20240032141A1SSB Enhancement for NR CDRX and DRX Operation

Publication Date: 2024.01.25 APPLE INC

AI summary

A user equipment (UE) is configured to receive synchronization signal blocks (SSBs) from a wireless network to estimate frequency and timing errors. The UE receives a quasi co-location (QCL) configuration between a synchronization signal block (SSB) and at least one of a further SSB or a tracking reference signal (TRS), receives the SSB and the at least one of the further SSB or the TRS and estimates a frequency and timing error for the SSB by combining, based on the QCL configuration, measurements for the SSB and measurements for the at least one of the further SSB or the TRS.