WCDMA Synchronization Channel (SCH) Explained

This section provides a tutorial on the Synchronization Channel (SCH) within the WCDMA (UMTS) system.

This page specifically describes the SCH, a crucial element for initial synchronization and cell search in WCDMA/UMTS networks.

The Synchronization Channel (SCH) is a downlink channel. Its primary function is to facilitate the initial synchronization process and assist in cell search procedures for User Equipment (UE). It enables the UE to determine key timing and cell identity parameters before it can decode control channels and establish a connection.

The SCH is comprised of two sub-channels:

• Primary SCH (P-SCH) : Short (256-chip) pre-defined code transmitted in every slot , Helps to find slot timings
• Secondary SCH (S-SCH) : one of 64 unique sequences (each sequence is a combination of 16 codes). Helps to find frame timing and scrambling code group

Functions of SCH

1. Cell Search : UE uses SCH to find and synchronize with the cell.
2. Slot Synchronization P-SCH allows detection of WCDMA time slots (every 0.666 ms).
3. Frame Synchronization S-SCH enables identification of frame timing (every 10 ms).
4. Scrambling Code Group Detection S-SCH narrows down the UE’s search for the correct primary scrambling code used by the cell.
5. Foundation for Decoding P-CCPCH Once synchronized using SCH, the UE can decode the P-CCPCH, which carries system information.

Summary

With the help of WCDMA-SCH, UE can determine timing or scrambling code information. It can decode the broadcast control channels like P-CCPCH.