About Viterbi algorithm

[hunter555persia]

Hi, I have written a MATLAB code for decoding convolutional codes using Viterbi algorithm. MATLAB also have Viterbi decoder function. So I ran a simulation to compare my code with MATLAB function. I see that my code performs worse than MATLAB function in both soft and hard modes. My code decodes perfectly when there is no noise. It also decodes the punctured codewords perfectly in the absence of noise. So everything seems OK, I don't understand why my performance curves are above MATLAB's. The decoding depth for continuous window is also the same for both my code and MATLAB function.

Any ideas ???
Thanks

 

[permute]

have you tried the 0's with errors case?
this is when you transmit all 0's, and then add a few errors at random (with acceptably low probability).

 

[hunter555persia]

I tried a stream of 1000bits and toggled 5 zeros in the 2000bit code (R=1/2). The decoder works fine.