REALIZATION OF SIMPLE DECODERS FOR HIGH-CODING-RATE CONVOLUTIONAL-CODES

This paper describes a method to configure pre-decoders for the high c oding rate convolution codes needed when the SST method is used, thus enabling low power consumption in a Viterbi decoder. The proposed pre- decoders have no correcting capability, but do allow decoding of convo lution codes with a minimum of hardware. The configuration method is s tudied here for general convolution codes with a constraint length K a nd a coding rate n/m. A specific circuit configuration for a pre-decod er is presented for the commonly used, punctured type, high coding rat e convolution codes with coding rates 3/4 to 7/8 and 15/16. The use of the SST method is now possible for high coding rate codes. The gate o perates with a coding rate of 7/8 and an error rate after decoding of 10(-4) that is 40% of that in the conventional type. Hence, a low powe r consumption Viterbi decoder is possible. As an example of the propos ed high coding rate pre-decoder, a high-speed transmission error rate estimation circuit is proposed and its characteristics are obtained. ( C) 1998 Scripta Technica.