CGI Reporting for NR Cells Without SIB1 via CD-SSB
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Solution Overview
Problem
Current RRC specifications face challenges in CGI reporting for NR cells that do not transmit System Information Block 1 (SIB1), as UEs behave as if they have not detected CGI, preventing immediate network setup of EN-DC X2 or Xn interfaces.
Innovation Solution
The UE is configured to synchronize with a Cell-Domain Synchronization Signal Block (CD-SSB) and search for SIB1 using a specified PCI rule, allowing it to acquire and report CGI information even if the associated SSB is not transmitting SIB1, with the introduction of a protection timer T322 to manage the reporting process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the UE behaves as if it has not detected CGI when SIB1 is not transmitted, then the current RRC specification behavior is maintained, but the network cannot immediately trigger the setup of EN-DC X2 or Xn interfaces
Solution Approach 1:
The system separates CGI acquisition into two paths: one for cells transmitting SIB1 (using current procedures) and one for cells not transmitting SIB1 (using the new CD-SSB based method). This segmentation allows the network to immediately trigger interface setup when CD-SSB is available, while maintaining existing behavior for SIB1-transmitting cells.
Solution Approach 2:
The CD-SSB acts as an intermediary carrier for CGI information when SIB1 is not transmitted. The UE acquires CGI from CD-SSB and reports it to the network, enabling immediate interface setup without waiting for SIB1 transmission.
2Loss of information
If the UE searches for SIB1 on the associated SSB frequency, then CGI can be acquired from cells transmitting SIB1, but additional complexity is introduced for cells not transmitting SIB1
Solution Approach 1:
The network pre-configures the UE with CD-SSB frequency location information before the UE needs to acquire CGI. This preliminary provision of frequency information eliminates the need for the UE to perform wide-band searches, reducing complexity while ensuring CGI information availability.
Solution Approach 2:
The CD-SSB serves as an intermediary that carries both synchronization signals and CGI information at a known frequency location. This intermediary structure simplifies the UE's search procedure by providing a predetermined frequency target rather than requiring exhaustive searches.
3Ease of operation
If a protection timer is introduced to manage the reporting process, then the UE can manage the reporting process more effectively, but the system complexity increases
Solution Approach 1:
The protection timer is started by the UE automatically upon detecting CD-SSB and is stopped when CGI reporting is completed. This self-service timer management reduces the need for complex network-UE coordination while improving reporting process management.
Solution Approach 2:
The timer mechanism provides feedback control to the reporting process: it starts when CD-SSB is detected and stops when CGI is successfully reported, ensuring the process is managed effectively without excessive complexity.
Data Source
AI summary
A wireless device receives (1502) configuration information indicating that the wireless device is to report identifier information for a cell. The configuration information identifies a first frequency. The wireless device acquires (1504) a first part of system information for the cell on the first frequency, using the configuration information. The wireless device determines (1506) that a second part of system information for the cell is not transmitted on the first frequency. The second part of system information for the cell is necessary for determining the identifier information. The wireless device receives (1508) the second part of system information, including the identifier information, on a second frequency and reports (1510) the identifier information for the cell to the wireless communications network.