I suggested a virterbi decoder because I thought it would be a good learning experiance and a practical design experiance.Apart from suggesting that you get yourself a good book on digital communications systems or maybe even starting here :- http://en.wikipedia.org/wiki/Convolutional_code I dont know how else to help you.
I think that maybe its too advanced rather than you cannot find any information on the subject.Also please dont say that youve found some code off the internet because if you dont understand what convolutional coding is you wont understand how the code works.the idea is that you dont copy someone elses work, the idea is that you read about it,understand it and you write your implementation in order to show that you understand it.It seems that isnt a fasionable concept.
Something else about it that might shock is that most references on the subject require that you have a slight modicum of understanding of the basic principles, I know thats not a very fashionable idea either.