Question
How does ARQ accomplish error correction?
Answer Options
- A) Special binary codes provide automatic correction
- B) Special polynomial codes provide automatic correction
- C) If errors are detected, redundant data is substituted
- D) If errors are detected, a retransmission is requested
Correct Answer: D
Explanation
Error correction techniques are used in digital communication to ensure the integrity of the data stream. These techniques are broadly divided into Forward Error Correction (\text{FEC}) and Automatic Repeat reQuest (\text{ARQ}). \text{FEC} adds redundancy to the data before transmission so the receiver can fix errors independently.
\text{ARQ} (Automatic Repeat reQuest) is a two-way protocol used in modes like \text{PACTOR} and \text{AMTOR}. When the receiving station detects an error in the received data block (using a cyclic redundancy check or similar method), it sends a negative acknowledgment (\text{NAK}). Therefore, \text{ARQ} accomplishes error correction because if errors are detected, a retransmission is requested from the transmitting station until the block is received correctly.
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