Performance of a viterbi decoder using simplified digital metric calculation
Makoto Miyake, Tadashi Fujino, Ken-ichi FUJIWARA · Electronics and Communications in Japan (Part I Communications) · 1988
Abstract Recently, convolutional coding with Viterbi decoding has been used widely in digital satellite communication systems. This paper addresses the problem of simplifying the process of digital metric calculation in a Viterbi decoder to realize reduced hardware complexity and increased operating speed. An analytical expression is introduced for the bit error rate (BER) performance of such a Viterbi decoder, and effects of the simplifications are evaluated for a typical convolutional code. It is shown that measured data agree well with theoretical curves, and that the simplifications can be introduced with no significant performance degradation. Finally, a method is proposed to design Viterbi decoders so that the degree of soft decision is increased and the number of bits for branch metrics is reduced to a specified value using a nonlinear transformation. For a constant number of bits for branch metrics, the BER performance realized by the proposed design method can be superior to that realized by the conventional design method. Results in this paper would be useful in designing simple Viterbi decoders for high‐speed applications.