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## 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.

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#### 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.