Soft decision decoding
So far in this chapter, it has been implied that the decoding process is performed on
the demodulated bit stream at the receiver output the so-called hard decision data.
A hard decision means that the decoder is given no information of how close the received symbol
was to the decision boundary, before the decision was taken.

By providing a decoder with 'side' information about how close each symbol was to the
decision boundary, the decoder is able to place greater or lesser emphasis on the validity
of any given symbol in its decoding process. In essence, the decoder tries to weight
the decisions and form an overall view over many symbols as to the most likely transmitted
symbol sequence. This enhanced decoding process is called soft decision decoding.