When a UE is switched on how does it knows to which cell it should camp on ?
This is done by cell search and system acquisition procedure.
According to TS 38.300 – 18.104.22.168 cell search procedure can be defined as below:
In cell search procedure, UE will acquires time and frequency synchronization with a cell and detects the Cell ID of that cell.
NR cell search is based on the primary and secondary synchronization signals, and PBCH DMRS, located on the synchronization raster.
Below steps tells the overall 5G NR Cell Search and System Acquisition Procedure :
1. UE tunes into a specific frequency.
2. UE tries to detect SSB and decode PSS and SSS. If UE is not able to detect and decode, it will go to step 1.
3. UE tries to decode PBCH.
4. It will decode MIB. It will contain the parameters required to decode SIB1.
5. Based on MIB.pdcch-ConfigSIB1, UE will find the location of CORESET0 and SearchSpace information. Then decode DCI 1_0.
6. Based on content of DCI 1_0 detect and decode PDSCH for SIB1.
7. Decode SIB1.
8. RACH procedure.
The procedure overall is similar to LTE Cell search procedure.
In NR, PSS, SSS and PBCH are transmitted in SSB Sync Signal Block.
We will learn about SSB in coming chapters.
Below image shows 5G Cell Search Procedure:
Below image shows 5G Cell Search and System Acquisition Procedure
MSI: Minimum System Information
RMSI: Remaining Minimum System Information
OSI: Other System Information
Click on below topics to understand each topics in depth.
UE performs cell selection/cell re-selection according to TS 38.304  and PLMN selection according to TS 23.122 .