Error detection and correction has got a great practical importance in maintaining information (data) integrity across noisy channels. Convolutional encoding is considered as one of the Forward Error Correction (FEC) schemes. A Viterbi Decoder (VD) uses the Viterbi algorithm for decoding a bit stream that has been encoded using FEC based on a convolutional code. In this proposed paper, a simulation of convolutional encoder and Viterbi decoder presented. This paper focuses on the performance study of Viterbi algorithm by varying parameters like constraint length, generating polynomials, traces back lengths and also modulation technique.