ARQmehhanismid

ARQmehhanismid refers to a class of error-control protocols used in data communications to provide reliable data delivery over channels that may introduce errors or losses. The core idea is automatic repeat requests: the sender transmits a data unit and waits for an acknowledgment from the receiver. If the acknowledgment is received correctly, the sender proceeds; if not, or if a timeout occurs, the sender retransmits. The approach relies on sequence numbers, acknowledgments, and sometimes negative acknowledgments, timers, and error-detection codes to detect corrupted frames.

Typical variants include Stop-and-Wait ARQ (one unacknowledged frame at a time), Go-Back-N ARQ (a window of frames is sent and, on error, all subsequent frames are resent from the erroneous one), and Selective Repeat ARQ (only erroneous frames are resent, allowing out-of-order delivery). Hybrid ARQ (HARQ) combines forward error correction with ARQ, using redundant information to reduce retransmissions and improve throughput.

ARQmehhanismid is used across various layers and media, including wired, wireless, satellite, and storage systems. Performance depends on channel error characteristics, the round-trip time, and the chosen window size or redundancy level. Key metrics include throughput, latency, and efficiency. Design considerations include synchronization of sender and receiver state machines, robust error-detection codes (such as CRC), and the management of timers and sequence numbers to prevent misinterpretation of duplicates or lost acknowledgments.

In practice, ARQ mechanisms are often implemented as components of transport protocols or link-layer protocols and are complemented by forward error correction in scenarios with high loss rates or limited feedback channels.