SCPC Systems

The term "Single Channel Per Carrier" or SCPC is widely used term in satellite communication. We know that satellite transponder will have some bandwidth and it is divided into number of carriers considering bandwidth across each carrier. For example C band satellite having total bandwidth of 500MHz is divided among many transponders having 36MHz bandwidth. Each transponder's band is used to carry information in the form of voice or data. This voice or data lines are called as channel.

SCPC means single channel (i.e. either voice channel or data channel) per RF carrier of a satellite transponder. As shown in the figure below either voice or data channel is modulated over RF carrier and transmitted using VSAT to the satellite and the same modulated signal down converted/amplified and sent down to the receiving VSAT on the other side by transponder. This is for mesh configuration. For Star configuration it will have two hops. Information flows from Transmitting VSAT to satellite, satellite to hub station, hub to satellite and further from satellite to receiving VSAT.

In this SCPC system, MUX can be configured for various bit rates as per channel and also data/voice can be configured. Various voice formats such as 2 wire E&M; 4wire E&M and so on can also be configured. The voice line can be interfaced with EPABX/PBX.

As it is imperative from SCPC concept that only single channel is occupying the carrier all the time, hence it is not an efficient system in the use of satellite resource (i.e. carrier for FDMA access assignment). Hence VOX feature is enabled to save power, which will only enable RF when voice activity is detected.

SCPC is mainly useful for defense applications requiring dedicated connection from one end to the other with encryption always enabled.