To get lte service, Ue has to establish radio connection(AS connection) with eNB and NAS connection with MME. To send a NAS message towards MME. UE makes radio connection with eNB, which is known as RRC connection setup procedure. For all these things, Ue need to acquire system information from eNB, eNB transmits system information in the form of MIB and SIBs. MIB is transmitted over PBCH channel and SIBs are transmitted over PDSCH channel. So UE first read MIB and get some information from MIB so that It can read SIBs. To read MIB message, UE perfroms cell synchronization (Primary and Secondary secondary synchronization).
Actually there are total 504 identifiers, that that can be used to identify a cell at physical level. Total 504 identifiers are divided in 168 groups and each group has 3 values(0,1,2)
PSS: Primary synchronization tells about one of three values(0,1,2)
SSS: Secondary synchronization tells about one of the groups ( 1 to 168)
Cell physical layer indentity is calculated by = 3 * (SSS value) + (PSS value).
PSS also known as slot level synchronization and SSS known as frame level synchronization. After doing this UE is synchronized in downlink with eNB. Now UE can reads MIB message from PBCH channel and SIBs from PDSCH channel.
