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Satellite orbital parameters and outline satellite communication principles
Published in L. Tetley, D. Calcutt, Understanding GMDSS, 2012
An advantage of using SCPC is to facilitate the use of voice-activated carriers. Such carriers are switched off during the periods between speech activity, thus reducing the power consumption. It has been established that on average a speaker will talk for only 40% of the time and switching off the carrier for the remaining 60% of the time reduces the satellite power consumption by up to 4 dB. This would enable a corresponding increase in power available and hence channel capacity for the transponder. To minimize inter-modulation between transmissions to acceptable levels, the output of the transponder power device must be backed off; typically this would be about 4 to 6 dB for a travelling wave tube amplifier (TWTA), and about 2 dB for a solid-state power amplifier (SSPA). The SSPA has a reasonably linear characteristic provided it is not over-driven. A small earth station, however, may suffer because of increased down-link noise and require a higher value of power per channel than otherwise would be the case. This would require less backoff for the transponder output power device. SCPC has the advantage that the power of individual transmitted carriers can be adjusted to optimize for particular link conditions.
From launch to transmission: satellite communication theory and SNG
Published in Jonathan Higgins, Satellite Newsgathering, 2012
The HPA can be operated near maximum power (termed ‘saturation’) when a single signal is being uplinked. This mode of operation is termed ‘single channel per carrier’ (SCPC). If there are multiple carriers being combined and uplinked, this is termed ‘multiple carriers per channel’ (MCPC). A larger amount of input back-off is always required in MCPC operation.
A Survey of National Disaster Communication Systems and Spectrum Allocation - an Indian Perspective
Published in IETE Technical Review, 2020
Shrayan Das, Kirtan Gopal Panda, Debarati Sen, Wasim Arif
Lower bandwidth requirement allows DMS User Nodes to use low-cost Time Division Multiplexing / Time Division Multiple Access (TDM/TDMA) technologies. This also facilitates bandwidth sharing among User Nodes. In the case of Primary nodes, Single Channel per Carrier (SCPC) is used due to higher bandwidth requirement and dedicated point-to-point connectivity.