The Art of Doing Science and Engineering: Learning to Learn

by Richard Hamming

Again, all we suppose is there is such a source, and we are going to encode it for transmission. The encoder is broken into two parts. The first half is called the source encoding, which as its name implies is adapted to the source, various sources having possibly different kinds encodings. The second half of the encoding process is called channel encoding and it is adapted to the channel over which the encoded symbols are to be sent. Thus the second half of the encoding process is tuned to the channel. In this fashion, with the common interface, we can have a wide variety of sources encoded first to the common interface, and then the message is further encoded to adapt it to the particular channel being used. Next, going to the right in Figure 10.1, the channel is supposed to have “random noise added.” All the noise in the system is incorporated here. It is assumed the encoder can uniquely recognize the incoming symbols without any error, and it will be assumed the decoder similarly functions without error. These are idealizations, but for many practical purposes they are close to reality. Next, the decoding is done in two stages, channel to standard, and then standard to the source code. Finally it is sent on to the sink, to its destination. Again, we do not ask what the sink does with it.