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Source encoding vs channel encoding

Short answer

Source encoding removes redundancy to compress data, reducing bit rate; channel encoding adds controlled redundancy for error detection/correction. Source aims for efficiency (compression), channel aims for reliability (error control).

How does source encoding differ from channel encoding?

Source encoding removes redundancy from the source output to cut the number of bits. Channel encoding adds controlled redundancy so that errors caused by the channel can be detected or corrected.

PointSource encodingChannel encoding
AimCompression (efficiency)Reliability (error control)
RedundancyRemovedAdded (parity/check bits)
Effect on bit rateLoweredRaised (code rate k/n<1k/n < 1)
Based onSource statistics (entropy HH)Channel noise (capacity CC)
Governing theoremShannon source coding theorem: Lˉ≥H\bar L \ge HShannon channel coding theorem: R≤CR \le C
Position in systemRight after the sourceAfter the source encoder, before the modulator
ExamplesHuffman, Shannon–Fano, LZW, PCM/DPCM, MP3, JPEGParity, Hamming, CRC, BCH, convolutional, turbo, LDPC
 Source -> [Source enc.] -> [Channel enc.]
        -> [Modulator] -> Channel

Example: text is first Huffman-coded to make it smaller (source coding). A Hamming (7,4) code is then added so that single-bit errors can be corrected (channel coding).

✓ Answer checked by Claude Opus 5.5 (high effort)

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