Made a mistake. The DVB-T receiver is not part of the 3.7.8 release.
It's a recent commit on the master branch (3.7.9git).
Ron
On 09/15/2015 01:31 AM, Ron Economos wrote:
The author of gr-dvbt looked at this issue when he developed the DVB-T
receiver. Here's a blog entry on his findings.
http://yo3iiu.ro/blog/?p=1393
He benchmarked the IT++ decoder in last place.
IT++ = 2-3 Mbps
gr-trellis = 5 Mbps
Karn C = 7-8 Mbps
gr-dvbt = 39-40 Mbps
The gr-dvbt receiver is now part of GNU Radio as of the last release,
3.7.8. The SSE2 viterbi decoder module is here:
https://github.com/gnuradio/gnuradio/blob/master/gr-dtv/lib/dvbt/dvbt_viterbi_decoder_impl.cc
In addition, I believe there's another decoder in gr-fec. I'm not very
familiar with it, so maybe someone else can comment on it. Looks like
it's in this module:
https://github.com/gnuradio/gnuradio/blob/master/gr-fec/lib/cc_decoder_impl.cc
Ron
On 09/15/2015 12:47 AM, Jeon wrote:
I've measured time taken by convolutional decoding in gr-ieee802-11.
The module is using Punctured Convolutional Code class from IT++
library
(http://itpp.sourceforge.net/4.3.0/classitpp_1_1Punctured__Convolutional__Code.html)
I've used chrono (chrono.h, chrono) to measure time taken. You can
see how I made it from the following page
(https://gist.github.com/gsongsong/7c4081f44e88a7f4407a#file-ofdm_decode_mac-cc-L252-L257)
I've measure time with a loopback flow graph (w/o USRP;
examples/wifi_loopback.grc)
The result says that it takes from 5,000 to 30,000 us, which is 5 to
30 ms to decode a signal with a length of 9,000 samples (samples are
either 1 or -1.)
* Test environment: Ubuntu 14.04 on VMWare, 2 CPUs and 4 GB RAM allocated
* Host environmetn: Windows 7 with i7-3770 3.7 GHz
Since I am not familiar with error correcting codes, I have no idea
how large the order of time taken is. But I think that one of the
most efficient decoding algorithm is Viterbi and that IT++ must use it.'
Then I can deduce that CC decoding takes a quite long time even
though the algorithm (Viterbi) is very efficient. And is it a natural
limitation of software decoding and SDR?
Another question comes that, the commercial off the shelf (COTS)
Wi-Fi device achieves really high throughput and that must be based
on super faster CC decoding. Is that because COTS is using heaviliy
optimized FPGA and dedicated decoding chips?
Regards,
Jeon.
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