Generalizations of the Viterbi algorithm with applications to mobile radio systems

Gives a brief overview of recent work on generalizations of the classic Viterbi algorithm (VA) in communication systems which use different types of concatenated coding schemes. The usefulness of the algorithms is illustrated by giving applications to speech and data transmission in mobile radio systems. Two classes of algorithms are considered, namely list output VA (or LVA) and soft symbol output VA (or SOVA). The LVA gives a list of the most likely output sequences while the SOVA gives output symbol by symbol reliability information. The additional list or soft symbol information is then processed by the next decoding stage. An overview is given of specific LVA and SOVA schemes including complexity and delay issues. It is demonstrated how gains in power and/or bandwidth are obtained with list and soft output VA over schemes with a conventional hard sequence output, at the expense of increased signal processing cost