In a stop-and-wait Automatic Repeat reQuest (ARQ) system, how does the transmitting terminal operate after sending a data block?
Electronics and Communication Engineering
Satellite Communication
Difficulty: Easy
Choose an option
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AIt waits for positive or negative acknowledgement from the receiving terminal
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BIt sends another block if positive acknowledgement (ACK) is received
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CIt resends the previous block if negative acknowledgement (NAK) is received
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DIt does not wait for acknowledgement after sending a block
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EIt continuously transmits blocks without waiting
Answer
Correct Answer: It waits for positive or negative acknowledgement from the receiving terminal
Explanation
Introduction / Context:Stop-and-Wait ARQ is one of the simplest error-control protocols in data communication. It ensures reliable delivery of data frames by requiring acknowledgements before sending new blocks.
Given Data / Assumptions:
- Sender transmits one block at a time.
- Receiver responds with ACK (positive) or NAK (negative).
- Timeout is set if no response is received within a fixed duration.
Concept / Approach:The sender must wait for confirmation before transmitting further data. This prevents data loss and ensures order but reduces throughput compared to more advanced ARQ protocols.
Step-by-Step Solution:
Step 1: Sender transmits one block of data.Step 2: Receiver checks and responds with ACK (if correct) or NAK (if error).Step 3: Sender either proceeds (ACK) or retransmits same block (NAK).Step 4: If no response within timeout, retransmission occurs.Verification / Alternative check:
Networking textbooks confirm Stop-and-Wait ARQ as a fundamental example of reliable transmission.Why Other Options Are Wrong:
Immediate sending without waiting breaks reliability.Only ACK and NAK responses govern transmission control.Continuous transmission is Go-Back-N or Sliding Window, not Stop-and-Wait.Common Pitfalls:
Confusing Stop-and-Wait ARQ with Go-Back-N ARQ or Selective Repeat ARQ.Final Answer:
It waits for positive or negative acknowledgement from the receiving terminal