FPGA Implementation of Viterbi Algorithm for Decoding of Convolution Codes

Abstract: Convolutional code is a coding scheme used in communication systems including deep space communications and wireless communications. It provides an alternative approach to block codes for transmission over a noisy channel. The block codes can be applied only for the block of data. The Convolutional coding has an advantage over the block codes in that it can be applied to a continuous data stream as well as to blocks of data. Viterbi decoder employed in digital wireless communication plays a rife role in the overall power consumption of trellis coded modulation decoder. Power reduction in Viterbi decoder could be achieved by reducing the number of states. A pre-computation architecture with T-algorithm was implemented for this purpose, and when we compare this result with full Trellis Viterbi decoder, this approach significantly reduces power consumption without degrading decoding speed. Convolutional encoding with viterbi decoding is a powerful FEC technique that is particularly suited to a channel in which the transmitted signal is corrupted mainly by Additive White Gaussian Noise (AWGN). It operates on data stream and has memory that uses previous bits to encode. The Viterbi Algorithm (VA) is proposed, used for decoding a bit stream that has been encoded using FEC code. The Convolutional encoder adds redundancy to a continuous stream of input data by using a linear shift register. A pre-computation architecture with Viterbi algorithm is implemented for this purpose, Viterbi (Convolutional) encoder and Viterbi decoder are designed and implemented using FPGA technology, which are the essential blocks in digital communication systems. It is particularly suited to a channel in which the transmitted signal is corrupted mainly by AWGN. The Viterbi decoder of Constraint length 7 and code rate 1⁄2 is considered. The design is implemented using verilog on Xilinx Spartan 3E and advanced Spartan 6 board and the results and Comparisons are presented.