The Influence of Pilot Symbols for Viterbi Decoding and Soft Viterbi Outut Based on the Parameters of the IEEE 802.11a Standard

H. Witschnig, R. Aichberger (Austria), H. Hutzelmann (Germany), M. Huemer (Austria), R. Weigel (Germ


Viterbi Decoding, SOVA, Decision Length


In this work we investigate the effect of pilot sequences that are multiplexed into a datastream for a Viterbi decoder as well as for the reliability of decisions in a Soft Output Viterbi Algorithm (SOVA). Parameters of comparison are decision length (maximal length of the trellis), number of forced decisions, code rate, bit error performance and implementation effort. It will be shown that pilot symbols are an excellent possibility to positively influence the reliability of decisions and to reduce the number of forced decisions as well as the necessary implementation effort. Furthermore it will be shown that a longer decision length of the Viterbi decoder leads to significant better results in terms of BER but does not correlate with a significant higher implementation effort. Finally it will be demonstrated that the use of pilot symbols in combination with puncturing combines better performance with higher coding rates (higher transmission rate).

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