On Fri, Jan 29, 2016 at 12:38 AM, Gonzalo Arcos <gonzaloarco...@gmail.com> wrote:
> Hello Tom, > > Thank you for your answer. > > I dont see how using the viterbi decoder from gr-fec would fix my problem. > I would still need the viterbi decoder to work on K=5 to be able to > integrate it with gr-ieee802-11, it is the same situation i am now with the > decoder i linked. My question is first if there is a highly optimized > decoder at least for 1/2 K=5, or in case it does not exist, if it is > possible for me to modify an existing implementation. I repeat, i am a > novice in the field of convolutional decoding. > > Thanks > Apologies, I misread your first email and swapped the constraint lengths. But no, modifying the implementation for different values of K is /not/ trivial. Tom > 2016-01-28 20:05 GMT-03:00 Tom Rondeau <t...@trondeau.com>: > >> On Thu, Jan 28, 2016 at 11:13 PM, Gonzalo Arcos <gonzaloarco...@gmail.com >> > wrote: >> >>> The dvbt project im talking about is: >>> https://github.com/gnuradio/gnuradio/tree/master/gr-dtv/lib/dvbt >>> >>> And the gr-ieee-80211 project is: >>> https://github.com/bastibl/gr-ieee802-11 >>> >>> thanks in advance >>> >> >> >> We have a highly optimized Viterbi decoder for K=7, rate 1/2 in gr-fec, >> which is done mostly in a VOLK kernel. Those parameters (R=1/2, K=7) are >> fixed, but the polynomials can be set externally. >> >> Tom >> >> >> >> >>> 2016-01-28 19:11 GMT-03:00 Gonzalo Arcos <gonzaloarco...@gmail.com>: >>> >>>> I am trying to optimize the current performance of gr-iee802-11. Ive >>>> done some profiling and came to the conclusion that there is a lot of work >>>> being put in decoding the convolutional code at the receiver. >>>> >>>> I have done some research, and found out that there exists a viterbi >>>> decoder that was developed for the digital tv branch, that supposedly >>>> outperforms IT++ by a factor of 9x!, IT++ being the library that >>>> gr-iee802-11 uses to decode the convolution. >>>> >>>> When trying to adapt this decoder to gr-iee802-11 ive found some >>>> hassles. First, the constraint length for the viterbi decoder in dvbt is K >>>> = 7, while in gr-ieee802-11 uses a constraint length of K=5. >>>> In addition, the generator polynomials also differ. >>>> >>>> I would appreciate if someone could help me here, i am a beginner in >>>> the matter of convolutional codes, i would like if someone could asses me >>>> if it is possible to adapt this viterbi decoder to gr-iee802-11 at all, and >>>> in case it is indeed possible, if it is very complex task for a non expert >>>> on the matter. >>>> >>>> The source file d_viterbi.c has a comment that says: >>>> That changing the polynomials would need me to "regenerate the >>>> BUTTERFLY macro calls in viterbi()" I am not certain about what should the >>>> new parameters be for the polinomials 0133 0171. >>>> https://github.com/gnuradio/gnuradio/tree/master/gr-dtv/lib/dvbt >>>> >>> >>> >>> _______________________________________________ >>> Discuss-gnuradio mailing list >>> Discuss-gnuradio@gnu.org >>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>> >>> >> >
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