An Overview of Source and Channel Coding
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The general structure of a communication system ๐
A communication system generally consists of the following stages, in order.
- Source: Provides information.
- Transmitter: Converts information into a transmission signal.
- Includes a formatter, source encoder, channel encoder, modulator, and multiplexer.
- Includes a
- Channel: Carries the transmitted signal; noise may be present.
- Receiver: Processes the received signal.
- Includes a demultiplexer, demodulator, channel decoder, source decoder, and deformatter.
- Includes a
- Destination: The final stage that receives the information.
Source coding vs. channel coding ๐
- Coding theory: Studies the properties of codes and their suitability for particular applications.
- Used in data compression, encryption, error correction, and network coding.
- Generally involves removing redundancy or correcting or detecting errors in transmitted data.
- Two main aspects:
- Data compression.
- Error correction.
- Source encoding: Compresses data at the source for more efficient transmission, as in ZIP and JPEG.
- Channel encoding: Uses additional data bits to detect or correct errors occurring during transmission, as in parity checks, CRC, and Hamming codes.
- Music CDs: Use ReedโSolomon codes.
- NASA: Uses turbo codes and low-density parity-check (LDPC) codes.