SCCPCH Secondary Common Control Physical Channel

The SCCPCH (Secondary Common Control Physical Channel) is a physical channel used in the Universal Mobile Telecommunications System (UMTS) to carry control signaling information between the mobile device and the base station (Node B). It is part of the UMTS air interface, which provides a wireless communication link between the mobile device and the network infrastructure.

The SCCPCH is specifically designed to carry secondary common control channels, which are used for various control functions in the UMTS system. These control functions include the establishment and maintenance of connections, power control, handover procedures, and other signaling exchanges between the mobile device and the network.

Here's a breakdown of the SCCPCH and its characteristics:

1. Physical Layer: The SCCPCH operates at the physical layer of the UMTS air interface. It is implemented using a dedicated frequency carrier and a specific spreading code.
2. Spreading Code: The SCCPCH uses a unique spreading code to differentiate it from other physical channels in the UMTS system. This spreading code is specific to the cell and is assigned by the network.
3. Time Division Multiplexing (TDM): The SCCPCH utilizes time division multiplexing to share the available resources with other channels in the UMTS system. Multiple SCCPCHs can be allocated within a time slot, and each mobile device is assigned specific time slots to transmit and receive control signaling.
4. Slot Format: The SCCPCH is divided into time slots, with each slot having a specific format. Each slot contains a predefined number of chips and carries control signaling information. The slot format depends on the type of control signaling being carried, such as access control, paging, or dedicated control signaling.
5. Transmission Rate: The SCCPCH has a fixed transmission rate, which is determined by the spreading factor used. The spreading factor defines the ratio between the chip rate and the data rate. Higher spreading factors provide better resistance to multipath fading but result in lower data rates.
6. Mapping to Physical Channels: The control signaling information carried by the SCCPCH is mapped onto physical channels for transmission over the air interface. These physical channels include the Primary Common Control Physical Channel (P-CCPCH) and the Secondary Common Control Physical Channel (S-CCPCH), among others.
7. S-CCPCH Configuration: The S-CCPCH can be configured in different modes, depending on the specific control signaling requirements. These modes include continuous transmission, discontinuous transmission, or periodic transmission, which are determined by network signaling and resource allocation strategies.
8. Synchronization: The mobile device must synchronize with the SCCPCH in order to receive and decode the control signaling information correctly. This synchronization is achieved by acquiring the primary synchronization channel (P-SCH) and secondary synchronization channel (S-SCH) transmitted by the base station.

In summary, the SCCPCH is a dedicated physical channel in the UMTS system used to carry control signaling information. It operates at the physical layer and uses a specific spreading code and time division multiplexing to transmit control signaling between the mobile device and the base station. The SCCPCH is configured in different modes and has a fixed transmission rate, and synchronization is required for proper reception and decoding of the control signaling.