S-SCH stands for "Secondary Synchronization Channel in UMTS" (
Universal Mobile Telecommunications System
The Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the In ...
).
S-SCH is a pure
downlink
In a telecommunications network, a link is a communication channel that connects two or more devices for the purpose of data transmission. The link may be a dedicated physical link or a virtual circuit that uses one or more physical links or shar ...
physical channel
In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer; The layer most closely associated with the physical connection between devices. This layer may be implemented by a PHY chip.
Th ...
broadcast over the entire cell. It is transmitted unscrambled during the first 256 chips of each time slot, in
time multiplex with Primary Common Control Physical Channel (P-CCPCH). It is the only channel that is not spread over the entire radio frame.
The S-SCH is repeated at the beginning of each
time slot
Broadcast programming is the practice of organizing or ordering (scheduling) of broadcast media shows, typically radio and television, in a daily, weekly, monthly, quarterly or season-long schedule.
Modern broadcasters use broadcast automation ...
and the same code is used by all the cells and enables the UE to detect the existence of the UMTS cell. The slot synchronization is done using the
P-SCH but S-SCH is used to synchronize the UE with the frame boundaries. It also enables the UE to identify the Primary Scrambling Code Group for the cell.
There are sixteen different codes for the 256 chips that are transmitted at the start of each time slot. Using these sixteen unique codes, 64 different code sequences are transmitted which serve two purposes. First the UE can identify the frame boundaries since the 64 sequences are known to a user equipment. Secondly the UE can identify the Primary Scrambling Code (PSC) group of the cell as every code sequence is assigned to a PSC group
References
*Andrew Miceli. Wireless Technician's Handbook. Artech House. Second Edition. 2003. . Page 188.
*Ajay R Mishra (ed). Advanced Cellular Network Planning and Optimisation: 2G/2.5G/3G ... Evolution to 4G. John Wiley & Sons Ltd. 2007. . Pages 89 and 92.
UMTS
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