ULPC
Pronunciation: U-L-P-C
Also written as: ULPC — Uplink Power Control
A technique by which a ground station automatically increases its transmit power to compensate for signal attenuation caused by rain fade or other propagation impairments, maintaining a stable signal level at the satellite.
Full Definition
ULPC is an adaptive countermeasure used at professional uplink stations to maintain a consistent EIRP at the satellite transponder input despite variable atmospheric attenuation. The system monitors beacon or pilot signal levels and adjusts HPA output power in closed-loop fashion. Open-loop ULPC uses weather data or propagation models instead. Editors encounter ULPC in system design specifications, operations procedures, and ITU coordination filings. The abbreviation should be expanded on first use, and editors should note that ULPC operates only within the headroom available in the HPA, so it does not eliminate outages under extreme rain events.
Usage
Usage note: Distinguish ULPC (transmit-power adjustment at the ground station) from ACM (waveform adaptation at the modem). Both are fade-countermeasure techniques but operate differently.
In Context
- "The ULPC system increased transmit power by 4 dB during the storm to maintain the required C/N at the satellite." — System performance report
- "Section 6.4 describes the closed-loop ULPC algorithm and its interaction with the beacon receiver." — Ground station design specification