4   Coding

M. D. Macleod

QinetiQ Ltd and University of Strathclyde

The Need for Error Control Coding

In a digital communications system, information is represented as a sequence of digits (numbers), also known as symbols. To transmit them, the digits are first converted to an analogue (continuous) form, such as voltage on a wire or light intensity in a fiber; this is called modulation. The received signal is then converted back into digits by demodulation. The communication channel, which is analogue, introduces noise and distortion, however, and these cause the corruption or loss of some digits at the receiver. The system designer reduces the probability of these errors by appropriate design of the analogue parts of the communication system, ...

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