AdvancedTopic 84 of 101Signals, Control & Comms
Channel coding
Error-correcting codes add redundancy to fix errors.
In depth
Channel coding adds structured redundancy to detect and correct errors: parity, Hamming, CRC (detection), Reed-Solomon, convolutional, turbo, LDPC, polar. Code rate R=k/n; coding gain; ARQ and HARQ combine detection and retransmission. Choice depends on latency, complexity and channel type.
Key points
- Minimum distance d_min
- Burst errors and interleaving
- Soft vs hard decision
ExampleA CRC-32 detects errors in Ethernet frames.
What is Channel coding?
Error-correcting codes add redundancy to fix errors.
Why is it important to understand channel coding?
Channel coding adds controlled redundancy so receivers can detect and correct errors, which is essential for reliable links.
What is redundancy in channel coding?
Extra bits added to the message that let the receiver detect or correct errors without asking for retransmission.
What is the trade-off?
More redundancy gives better protection but reduces the useful data rate, so the code is chosen to balance the two.
How is Channel coding used in practice?
Typical applications include adding parity to a serial data link to detect errors, using forward error correction on a satellite link and protecting stored data from bit flips with error-correcting codes.
What should I learn before Channel coding?
Study "Source coding" first (topic 83 of 101 in Signals, Control & Comms). It covers the groundwork this topic builds on.
What are the key points of Channel coding?
Minimum distance d_min. Burst errors and interleaving. Soft vs hard decision.
Can you give an example of Channel coding?
A CRC-32 detects errors in Ethernet frames.
What comes after Channel coding?
The next topic is "Block and convolutional codes", which builds directly on this one.
How difficult is Channel coding?
It is classed as Advanced in Signals, Control & Comms (topic 84 of 101). It is an advanced topic. It assumes you are comfortable with the intermediate topics in Signals, Control & Comms.