Question
In digital television, what does a coding rate of 3/4 mean?
Answer Options
- A) 25% of the data sent is forward error correction data
- B) Data compression reduces data rate by 3/4
- C) 1/4 of the time interval is used as a guard interval
- D) Three, four-bit words are used to transmit each pixel
Correct Answer: A
Explanation
In digital communications, including digital television (DTV or DVB-T), reliability is crucial. Data streams often include redundant bits that are used to detect and correct errors caused by noise or fading, a process known as Forward Error Correction (FEC). The coding rate quantifies the proportion of the data stream that carries the actual information versus the portion dedicated to redundancy.
A coding rate of \frac{3}{4} means that for every 4 bits transmitted, 3 bits are genuine information (payload) and 1 bit is redundant overhead used for error correction. This translates directly to: 1 - \frac{3}{4} = \frac{1}{4}, or 25% of the data sent is dedicated to forward error correction data. This overhead sacrifices transmission speed for increased robustness and reliability against signal degradation.
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