Asynchronous vs Synchronous Efficiency Comparison | Generated by AI
Question: For data links with the same transmission rate, when using asynchronous protocol or synchronous protocol to control large-volume data transmission, what is the transmission efficiency ratio (asynchronous protocol / synchronous protocol)?
A. Close to 80%
B. Close to 1
C. Close to 50%
D. Equal to 1
Answer:
A
Explanation:
In serial data communication:
-
Asynchronous protocol (most commonly referring to UART-style asynchronous serial communication):
Each character/byte is independently framed with 1 start bit + 8 data bits + 1 stop bit (most common format is 8N1).
→ Total bits per byte = 10 bits
→ Efficiency = 8 / 10 = 80% -
Synchronous protocol (e.g. HDLC, SDLC, synchronous serial protocols, or modern high-speed synchronous links):
Usually transmits data in blocks/frames with only a small amount of overhead for frame synchronization, flags, headers, CRC/checksum, etc.
When transmitting large volumes of data, the overhead per byte becomes very small (often <1–5%).
→ Efficiency is typically very close to 100% (or 95%+ for practical large-block transfers)
Therefore, for large-batch / bulk data transmission, the efficiency ratio is:
Asynchronous efficiency / Synchronous efficiency ≈ 80% / ~100% ≈ 80%
Hence the correct answer is A. close to 80%.
Why not the other options?
- B. close to 1 → This would be true only if both protocols had similar overhead, which is not the case for large data volumes.
- C. close to 50% → This is too pessimistic; even asynchronous UART is 80%, not 50%.
- D. equal to 1 → Clearly incorrect due to the fixed start/stop bit overhead in asynchronous mode.
Memory tip (as given in the explanation):
“异步低效八成满，同步高效更划算”
→ Asynchronous is about 80% full (efficient), synchronous is more cost-effective (higher efficiency).
References:
- None (standard data communication theory)