Hi Achilleas, I was interested in various length packets. I am taking a fixed length packet ( say 200 symbols ) and then bitstuffing it, resulting in a packet >= 200 symbols. I then receive this with the viterbi algorithm and then finally unbitstuff. So in this, case K = 200 + number of stuffed bits. I guess I could run N viterbi algorithms in parallel for the N possible different number of stuffed bits. I guess I could also have the block that bitstuffs the data pad out to a fixed block size.
Thanks again for you suggestions and help. Tim On 2/21/07, Achilleas Anastasopoulos <[EMAIL PROTECTED]> wrote:
Tim, I think there are two parts in your question: 1) how to detect an incoming packet and do something with it. 2) how to operate the viterbi algorithm block in a packet to packet basis without generating the flow graph again. I only know how to answer the latter question: The viterbi algorithm (see all examples in gnuradio-examples/python/channel-coding/) processes the incoming stream in PACKETS by design. When you instantiate the block, ie using va = trellis.viterbi_s(f,K,s0,sK) then "K" is the block size to be processed (measured in trellis steps), with initial state fixed at "s0" and final state fixed at "sK" (or put -1 in the corresponding positions if you dont want to fix them). Thus is we send a stream of n x K symbols then the va block will run the algorithm n times with the set initial/final states. If you send a continuous stream of data to the input of the VA it will break it into blocks of K symbols and process each block separately. Hope this helped clarify the use of the viterbi block. Achilleas
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