Realization of simple decoders for high-coding-rate convolutional codes

This paper describes a method to configure pre-decoders for the high coding 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 convolution codes with a minimum of hardware. The configuration method is studied here for general convolution codes with a constraint length K and a coding rate n/m. A specific circuit configuration for a pre-decoder is presented for the commonly used, punctured type, high coding rate 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 operates 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 power consumption Viterbi decoder is possible. As an example of the proposed high coding rate pre-decoder, a high-speed transmission error rate estimation circuit is proposed and its characteristics are obtained.