Hard-decision Decoding Research Articles

The Impact of Mismatch on the Performance of Coded Narrow-Band FM with Limiter/Discriminator Detection

The performance of uncoded narrow-band FM with limiter/discriminator (L/D) detection over the additive white Gaussian noise channel has received widespread attention [1]-[14] over the years both from simulation and analytical standpoints. By comparison, little or nothing has appeared in the literature for the performance of this modulation/demodulation technique when used together with coding/decoding. The purpose of this paper is to partially fill this void by considering the potential gain offered by the combination of convolutionally encoded narrow-band FM with L/D detection and Viterbi decoding. Both hard and soft decision decoding cases will be considered with some rather surprising differences between the performances of the two. In particular, it will be shown that a large departure exists from the 2 dB advantage traditionally associated with soft decision decoding which is explained in terms of the mismatch between the coding channel and the decoding metric peculiar to this modulation/demodulation technique.

Soft-decision error control for H.F. data transmission

This paper is concerned with the soft-decision decoding of error-correcting codes in the context of h.f. data transmission. The use of soft-decision information from the data modem results in an improvement in the performance of a forward-error-correction scheme, when compared with hard-decision decoding, without any further redundancy penalty. In the paper, we estimate the theoretical improvements that can be expected from soft-decision decoding of block and convolutional codes, in terms of both random and burst error-correcting power. Also, this is related to expected coding gains for the Gaussian and Rayleigh fading channels. In addition, we investigate the performance of soft-decision decoding on two types of h.f. modem: a multisubcarrier parallel transmission format (p.t.f.) type modem, and an experimental serial transmission s.m.i.d.d. type modem. We conclude that significant improvements in the performance of coded systems are obtainable through the use of soft-decision decoding.

A note on soft decision decoding with successive erasures (Corresp.)

This paper deals with soft decision as a means to bridge the gap in performance between a receiver using hard decision symbol estimation followed by an algebraic decoder and a maximum-likelihood receiver. A measure of the reliability of the code symbol estimates is introduced to facilitate the decoding process. The decoding operation studied erases the least reliable received symbols and then applies an algorithm capable of correcting errors and erasures. This procedure, termed successive-erasure decoding (SED), was introduced by G. D. Forney in connection with general minimum-distance decoding (GMD). It is studied for binary and nonbinary transmission using polyphase signals on the additive white Gaussian noise (AWGN) channel. The exponential behavior of the error probability at high signal-to-noise ratio (SNR) is calculated and is supplemented by computer simulations. The results indicate that soft decision by successive erasures for binary transmission has properties not present in the nonbinary case. In the binary case the procedure is asymptotically optimum for increasing SNR's. On the nonbinary channel, however, the procedure is only capable of bridging part of the gap in performance between maximum-likelihood decoding (MLD) and hard decision decoding (HDD).