The S-SCH also consists of a code, the Secondary Synchronization Code (SSC) that indicates which of the 64 scrambling code groups the cell’s downlink scrambling code belongs to. 16 different SSCs are defined. Each SSC is a 256 chip long sequence.
There is one specific SSC transmitted in each time slot, giving us a sequence of 15 SSCs. There is a total of 64 different sequences of 15 SSCs, corresponding to the 64 primary scrambling code groups. These 64 sequences are constructed so that one sequence is different from any other one, and different from any rotated version of any sequence. The UE correlates the received signal with the 16 SSCs and identifies the maximum correlation value.
The S-SCH provides the information required to find the frame boundaries and the downlink scrambling code group (one out of 64 groups). The scrambling code (one out of 8) can be determined afterwards by decoding the P-CPICH. The mobile will then be able to decode the BCH.