Error control in satellite links: In digital satellite communications, ARQ is a classic error-control strategy. What does ARQ stand for?

Introduction / Context:
Satellite links suffer from noise, fading, and occasional burst errors. To ensure reliable delivery, error-detection codes are often coupled with retransmission strategies. ARQ is a foundational scheme in link-layer reliability for many channels, including satellite.

Given Data / Assumptions:

• ARQ uses error detection (e.g., CRC) at the receiver.
• Receiver requests a retransmission upon detecting an error.
• Suitable for links where feedback and delay are acceptable.

Concept / Approach:

ARQ expands to Automatic Repeat Request. It contrasts with FEC (Forward Error Correction), which sends redundant parity to correct errors at the receiver without retransmissions. Hybrid ARQ combines both methods for improved efficiency over variable channels.

Step-by-Step Solution:

Verification / Alternative check:

Standard data link control literature and satellite comms texts define ARQ as Automatic Repeat Request, with variants like Stop-and-Wait, Go-Back-N, and Selective Repeat.

Why Other Options Are Wrong:

• Relay/Recovery/Quenching: not standard expansions in data communications.

Common Pitfalls:

Confusing ARQ with FEC; ARQ needs a return channel and tolerates retransmission delays, which must be considered for GEO latency.

Final Answer:

Automatic Repeat Request