---
title: "Need for channel coding"
subject: "Data Communication"
chapter: 8
key: "semester_5/data_communication:channel-coding-need"
source: https://www.bctengineer.com/q/semester_5/data_communication/channel-coding-need
site: BCT Engineering
---

# Need for channel coding

Data Communication · Chapter 8: Information Theory and Coding

- Asked in: 2075 Chaitra, 2 marks
- Video: [Introduction to Channel Coding  | Lecture 14| Information Theory & Coding Technique| ITCCN](https://www.youtube.com/watch?v=gr1UpinRpNs) — Dr. Sarika Panwar
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/data_communication/channel-coding-need
- Whole chapter: https://www.bctengineer.com/md/semester_5/data_communication/chapter-8

## Question

Explain why channel coding is required in data communication.

## Short answer

Chanel coding adds redundancy to combat noise and fading, enabling error detection/correction (FEC or ARQ). It reduces bit error rate, provides coding gain, and allows reliable communication near Shannon limit, essential for satellite, deep-space, and broadcast links.

## Answer

Real channels add noise, interference and fading, so bits received may differ from those sent. Channel coding adds controlled redundant (parity) bits so that the receiver can **detect and correct errors** without asking for retransmission (FEC), or at least detect them (ARQ). It lowers the bit error rate for a given signal power (coding gain), permits reliable communication near the Shannon capacity, and is vital where retransmission is costly or impossible, such as satellite and deep-space links and broadcast. Examples: Hamming, CRC, convolutional, Reed-Solomon codes.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Why is channel coding needed?
   A. To compress the data
   B. Noise, interference and fading can corrupt bits
   C. To make signals faster
   D. To remove the need for a receiver
   Answer: B. Real channels corrupt bits, so redundancy lets the receiver detect and correct errors. (Key point: Why noise matters)

2. What does forward error correction (FEC) allow?
   A. Correcting errors without retransmission
   B. Only detecting errors
   C. Compressing data
   D. Raising the signal power
   Answer: A. FEC lets the receiver correct errors itself, useful where retransmission is costly, e.g. satellite links. (Key point: FEC)

3. What does channel coding give for a fixed signal power?
   A. A higher bit error rate
   B. A lower bit error rate (coding gain)
   C. Fewer bits transmitted
   D. No change
   Answer: B. Coding gain means a lower BER at the same signal power. (Key point: Coding gain)

## Related in Data Communication

- [Source coding vs channel coding](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Asource-vs-channel-coding) — Data Communication, chapter 8
- [Required SNR for 40 Mbps over 6 MHz](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Acapacity-40mbps-6mhz) — Data Communication, chapter 1
- [Linear block coding with example](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Alinear-block-code-explain) — Data Communication, chapter 8, asked 3×
- [Huffman coding principle](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Ahuffman-principle) — Data Communication, chapter 8, asked 3×
- [B8ZS line coding](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Ab8zs-coding) — Data Communication, chapter 5, asked 2×
- [HDB3 (HD3S) line coding](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Ahdb3-coding) — Data Communication, chapter 5, asked 2×

## Related in other subjects

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- [Channel coding and types of LPC](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Achannel-coding-lpc-types) — Wireless Communication, chapter 6
- [Source vs channel coding; Huffman for five symbols](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Asource-channel-huffman-five) — Communication Systems, chapter 6
- [Digital communication system elements; Shannon-Fano coding](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Adcs-block-shannon-fano) — Communication Systems, chapter 6