Hello Is it a generally accepted fact that the best punctured convolutional code performance approaches the performance of the equivalent non-punctured code at the same rate. Is there any figure of merit as to what the traceback depth should be given a certain puncturing scheme. For example, I notice that: with a rate 1/2, constraint length K=7 unpunctured code, tracebach depth D=5*K=35, I get close to 7-8 dB improvement in Viterbi decoding (unquantized) performance relative to no coding. Now, when I puncture the rate 1/2, K=7 code to get a rate 7/8 code, I have to use a traceback depth of 20*K=140 to get a performance improvement. However, this performance improvement occurs only at Eb/N0 values>8 dB, where I observe a 2-3 dB improvement in performance... Any comments regarding the traceback depth vs puncturing relationships.. Regards Vikram
Punctured Viterbi decoding
Started by ●May 26, 2005
Reply by ●May 27, 20052005-05-27
This was what I noted while working on punctured convolutional codes. =B7As the traceback length of the viterbi decoder increases, error in the decoded bit stream reduces and also the viterbi decoder approaches optimum decoding. It provides more uniform and predictable performance as can be seen by comparing performance obtained from shorter length trellis. Same is the case with the punctured conolutional codes. Since we have already weakened the data by puncturing the coded bit stream and hence viterbi decoder is more prone to make errors if we prematurely (with shorter traceback) decode the bits. But as we increase the traceback length, chance of error propagating to later states is less and hence we get better error performance.=20 Hope this helps Tarang