Satellite Communication Glossary: A-F

A

ACM (Adaptive Coding and Modulation)

A technique that dynamically adjusts the modulation scheme and forward error correction coding based on real-time link conditions to optimize throughput while maintaining reliability.

Antenna Gain

The ratio of the power radiated by an antenna in a specific direction compared to an isotropic antenna. Measured in dBi (decibels relative to isotropic).

APSK (Amplitude Phase Shift Keying)

A modulation scheme used in DVB-S2/S2X that combines amplitude and phase modulation, allowing higher spectral efficiency than pure PSK.

Availability

The percentage of time a communication link meets its performance specifications, typically expressed as a percentage (e.g., 99.7%).

B

Backhaul

The portion of a network that connects remote sites to the core network or internet backbone.

Bent-Pipe

A satellite transponder configuration that simply amplifies and frequency-converts signals without any onboard processing. Also called "transparent."

BER (Bit Error Rate)

The number of bit errors divided by the total number of transferred bits. A key quality metric for digital communications.

BUC (Block Up-Converter)

The outdoor unit component that converts the modem's intermediate frequency (IF) signal to the transmit RF frequency and amplifies it.

C

C-Band

The portion of the electromagnetic spectrum from 4 to 8 GHz. Satellite C-band typically uses 5.925-6.425 GHz (uplink) and 3.7-4.2 GHz (downlink).

CIR (Committed Information Rate)

The guaranteed minimum bandwidth available to a user, regardless of network congestion.

C/N (Carrier-to-Noise Ratio)

The ratio of received carrier power to noise power within a given bandwidth. A key parameter in link budget calculations.

D

DVB-S2X

Digital Video Broadcasting - Satellite Second Generation eXtended. The latest satellite broadcasting standard with improved efficiency and additional MODCODs.

Downlink

The transmission path from a satellite to an Earth station.

E

EIRP (Effective Isotropic Radiated Power)

The product of transmit power and antenna gain, representing the power that would be needed by an isotropic antenna to produce the same signal strength.

Elevation Angle

The angle between the local horizontal plane and the line of sight to the satellite.

F

FDMA (Frequency Division Multiple Access)

A channel access method where different users are assigned different frequency bands.

FEC (Forward Error Correction)

Error correction techniques that add redundancy to transmitted data, allowing receivers to detect and correct errors without retransmission.

FSPL (Free Space Path Loss)

The loss in signal strength as electromagnetic waves propagate through free space. Increases with distance and frequency.

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