Two possible procedures:

1. initial cell selection

2. cell selection based on stored information


1. Initial cell selection procedure occurs. That is, UE tries to find a cell (not necessarily the best cell, but a usable cell) for it to camp on the cell.

For a given frequency, UE does the below until it finds a working cell:

There are roughly four steps for initial cell selection:

1. search for primary synchronization channel (P-SCH):

chip and slot synchronization is done

2. frame synchronization via secondary synchronization channel (S-SCH):

3. find the primary scrambling code from the common pilot channel(CPICH):

4. tune to Primary common control physical channel (P-CCPCH) and decode the system information;

check whether it is a suitable cell for camping ( PLMN code is broadcast)


Once you successfully camped on a cell, you can get the neighbor list from the system information and tries to camp on the best cell.

2. Frequency and scrambling code may be saved on the phone. The UE may try to synchronize into the cell after switch on, and if it fails, it may do the initial cell selection as above.

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