Explanation
According to the 5G SA Cell Search & Network Entry Matrix, the first step for a UE to perform a cell search in SA networking is to synchronize frames and obtain PCI group number. This step involves the following sub-steps:
The UE scans the available frequency range to detect the presence of Synchronization Signal Blocks (SSBs) from different base stations. SSBs are periodic signals that contain essential synchronization and system information for cell search and initial access.
The UE selects an SSB with the strongest signal strength and decodes its Primary Synchronization Signal (PSS) and Secondary Synchronization Signal (SSS). The PSS and SSS are part of the SSB and provide coarse timing synchronization and cell identity information.
The UE uses the PSS and SSS information to synchronize its internal clock with that of the base station and obtain the Physical Cell Identity (PCI) group number. The PCI group number is a 9-bit value that identifies a group of 8 cells that share the same PSS and SSS sequences. The PCI group number ranges from 0 to 1007.
The other steps for a UE to perform a cell search in SA networking are:
Synchronize half-frames and obtain the ID within a PCI group: The UE further synchronizes its timing with the base station by decoding its Narrowband Synchronization Signal (NSSS), which is also part of the SSB. The NSSS provides more precise timing information and the ID within a PCI group, which is a
3-bit value that identifies a specific cell within a PCI group. The ID within a PCI group ranges from 0 to
7. By combining the PCI group number and the ID within a PCI group, the UE can obtain the full PCI, which is a 10-bit value that uniquely identifies a cell.
Obtain other cell information: The UE decodes other signals and channels in the SSB to acquire other cell information, such as system bandwidth, subcarrier spacing, frame structure, etc. These signals and channels include Demodulation Reference Signals (DMRS), Master Information Block (MIB), System Information Block (SIB), etc.
Obtain the cell signal quality: The UE measures the cell signal quality based on various indicators, such as Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), Signal-to-Interference-plus-Noise Ratio (SINR), etc. These indicators reflect the strength, quality, and interference level of the received signal.