Soft Decision Viterbi Decoding Research Articles

FM/TV Interference into rate 1/2 FEC encoded SCPC/QPSK

AbstractThis paper presents some results obtained in laboratory measurements of interference caused by FM television signals to encoded SCPC/QPSK carriers. Certain parameters, such as the TV energy dispersal excursion, the frequency spacing between wanted and interfering carriers, the SCPC bit rate, etc., were varied during the measurements in order to study their influence on the amount of interference suffered by the SCPC channel.Computer simulations were also carried out in order to analyse and interpret measurement results obtained in some cases.Conclusions are drawn on the use of a possible interference criterion when rate 1/2 convolutional encoding and soft decision Viterbi decoding is used in the SCPC system as well as on the expected improvement with frequency offset.

A coded frequency diversity system for HF data transmission

An error control scheme based on convolutionally-coded frequency diversity transmission and soft-decision Viterbi decoding is proposed for HF data transmission. Simulation and experimental results are presented that show that the block error rate performance of the system is much better than that of conventional frequency diversity systems. It is also shown that the new scheme achieves significant throughput under channel conditions where conventional systems fail. A real-time microprocessor implementation of the system is described.

Real-Time Application of Trellis Coding to High-Speed Voiceband Data Transmission

We describe the application of multilevel trellis coding to the transmission of high-speed' voiceband data. The implementation aspects of soft-decision Viterbi decoding associated with such coding are discussed, Real-time performance comparison is made of two coded systems at 9600 bits/s with respect to an uncoded system. The performance sensitivity Of the three systems to DDD channel impairments other than additive Gaussian noise are also described. It is shown that the experimental results agree well with those from theory, and that trellis coding provides significant improvement in performance in the presence of impairments other than additive Gaussian noise.

High-Rate Punctured Convolutional Codes for Soft Decision Viterbi Decoding

The high-rate punctured codes of rates 2/3 through 13/14 are derived from rate 1/2 specific convolutional codes with maximal free distance. Coding gains of derived codes are compared based on their bit error rate performances under soft decision Viterbi decoding.

Practical applications of coding

Coding applications have grown rapidly in the past several years with cost-effective performance demonstrated on several channels. Convolutional coding with soft-decision Viterbi decoding has emerged as a standard technique and is particularly well adapted to the commnnication satellite channel. Decoder implementations are discussed and examples are cited. Robustness of code performance is emphasized and instances of actual coding gain surpassing theoretical or basic coding gain are given. Some promising future directions are noted.