* Switch On the UE.
* Frequency Search
* Cell Synchronization.
When we switch on the UE, It will scan and tune it's radio to a frequency depending on which band it is supporting. Now suppose UE is tuned to a particular frequency channel, it will try finding PSS (primary synchronization signal) and SSS (secondary synchronization signal ). PSS is transmitted in the last OFDM symbol of first time slot of the first sub-frame and from PSS, UE will get Cell Identity In Group ranges form 0 to 2. Once UE got PSS, next is SSS. SSS signals are transmitted in the same sub-frame as of PSS but in the symbol just before PSS. From SSS, UE will get Physical Layer Cell Identity Group ranges from 0 to 167.
Using Cell Identity in Group and Physical Cell Identity Group Number, UE calculate PCI (Physical Cell ID) for the cell as follows:
PCI (Physical Cell ID) = 3*(Physical Cell Identity Group)+ Cell Identity In Group
Using the above equation, 504 unique physical cell identities can be created.Using this PCI, UE will detect the cell specific Reference Signal which is used in channel estimation and cell selection. Thus if we summarize this frequency search & cell synchronization procedure or you can say this complete blog post, it will be like this:
Switch-On the UE ---> it will find frequency and tune it's radio to the same ----> UE will find PSS & SSS to figure out Phy Cell ID. ----> Using this Phy Cell ID, UE find Reference Signal for channel estimation and cell selection.
After cell synchronization procedure, UE will proceed to read Master information block (MIB) and other System information blocks (SIBs). Further read: LTE System Information Acquisition.