A HARDWARE IMPLEMENTATION OF PUNGURED CONVOLUTIONAL CODES TO COMPLETE A VITERBI DECODER CORE

Abstract

This paper presents a VLSI (Very Large Scale Integration) implementation of high punctured convolutional codes.We present a new circuit architecture that is capable of processing up to 10 convolutional codes rate (n-1)/n withthe constraint length-7 derived by the puncturing technique from the basic rate-1/2. The present circuit wasdesigned in order to complete an existing Viterbi decoder core, adding some extra functionality such as aconvolutional encoder, differential encoder/decoder, punctured convolutional encoder and symbol insertion todepuncture the received data. This extra functionality includes 10 different programmable coding rates without theneed to add additional logic in the system implementation, while other existing coders need it to attain highercoding rates. Therefore, a single chip solution is presented. The design was implemented in VHDL (Very High SpeedIntegrated Circuit Hardware Description Language) synthesized in Synopsys tool, and tested in a FPGA. Functionalverification was done, by means of simulation, to ensure that the circuit implements intended functionality. Suchsimulations were executed using Synopsys and a Sun Ultra Sparc 10 workstation. Different bit error probabilityperformance curves show an agreement between simulated and theoretical values.