Hi Dave, obviously 95% success means a 5% packet error rate. That sounds pretty physically sound -- for most constellations, you can calculate the symbol error rate from the SNR, and from the symbol error rate it's a matter of combinatorics to derive the lower boundary for packet error rate. Again, this is wireless communication. It's not a "works perfectly/works not at all" world, but a "works stochastically" world. 5% packet error rate might or might not be acceptable, depending on a specific application.
Best regards, Marcus On 09/25/2015 12:07 AM, Rama V wrote: > Hi all, > I have tried to send packets to the receiver from /digital/narrowband > folder and it has mostly succeeded. The output I was able to get when > I sent the following commands were > > Sender: ./benchmark_tx.py -p 4 -M 2 -f 2.435000061G --tx-gain=28 -r 250000 > Receiver: ./benchmark_rx.py -p 4 -f 2.435000061G --rx-gain=54 -r 250000 > > ok = True pktno = 1323 n_rcvd = 1303 n_right = 1294 > ok = True pktno = 1324 n_rcvd = 1304 n_right = 1295 > ok = True pktno = 1325 n_rcvd = 1305 n_right = 1296 > ok = True pktno = 1326 n_rcvd = 1306 n_right = 1297 > ok = True pktno = 1327 n_rcvd = 1307 n_right = 1298 > ok = True pktno = 1328 n_rcvd = 1308 n_right = 1299 > ok = True pktno = 1329 n_rcvd = 1309 n_right = 1300 > ok = True pktno = 1330 n_rcvd = 1310 n_right = 1301 > ok = False pktno = 1331 n_rcvd = 1311 n_right = 1301 > > But there were a few packets where I have not received them correctly. > I guess only 95% of them were efficient in transmitting. I have tried > changing the gain settings and what I observed was that if I decrease > the gain from its normal value, the reception of packets are somewhat > less efficient. Can I kindly know what I might be able to do in order > to receive those packets in a more efficient way or is that what > generally happens in a real world transmission? Thanks > > Regards, > Dave > > On Tue, Sep 22, 2015 at 1:02 PM, Marcus Müller > <marcus.muel...@ettus.com <mailto:marcus.muel...@ettus.com>> wrote: > > Ok, >> This is because I have changed my folder to /digital/ofdm, I have >> started to receive packets. > this means that you're using something *completely* different than > before. It's simply a completely different transceiver system. >> kindly advise if I need to figure out the combination settings >> till most of them receive properly? > Yes. You will need to figure out the optimum settings. Increase > gain on the RX end, see if things get better or worse. Find an > optimum for that. Do the same with the TX gain. >> Because even though I did not set any sample rate, the >> transmitter sent the information. > As mentioned before multiple times: run the programs with > "--help". They will show you what default settings they have. > >> Please help. Please excuse me if I am being naive in asking these. > It's alright to ask questions, but please remember to apply the > things we tell you. > > Best regards, > Marucs > > > On 22.09.2015 00:59, Rama V wrote: >> Hi, >> As advised, the problem has been solved to a little extent where >> I have got the below results by giving the commands as >> >> Sender : ./benchmark_tx.py -f 2.435G --tx-gain=25 >> Receiver: ./benchmark_rx.py -f 2.435G --rx-gain 50 >> >> ok: True pktno: 1971 n_rcvd: 1687 n_right: 358 >> ok: False pktno: 1972 n_rcvd: 1688 n_right: 358 >> ok: False pktno: 1973 n_rcvd: 1689 n_right: 358 >> ok: False pktno: 1974 n_rcvd: 1690 n_right: 358 >> ok: True pktno: 1975 n_rcvd: 1691 n_right: 359 >> ok: False pktno: 1976 n_rcvd: 1692 n_right: 359 >> ok: True pktno: 1977 n_rcvd: 1693 n_right: 360 >> ok: False pktno: 1978 n_rcvd: 1694 n_right: 360 >> ok: True pktno: 1979 n_rcvd: 1695 n_right: 361 >> ok: True pktno: 1980 n_rcvd: 1696 n_right: 362 >> ok: False pktno: 1981 n_rcvd: 1697 n_right: 362 >> ok: True pktno: 1982 n_rcvd: 1698 n_right: 363 >> ok: False pktno: 1983 n_rcvd: 1699 n_right: 363 >> ok: True pktno: 1984 n_rcvd: 1700 n_right: 364 >> ok: False pktno: 1985 n_rcvd: 1701 n_right: 364 >> ok: True pktno: 1986 n_rcvd: 1702 n_right: 365 >> ok: False pktno: 1987 n_rcvd: 1703 n_right: 365 >> ok: True pktno: 1988 n_rcvd: 1704 n_right: 366 >> >> This is because I have changed my folder to /digital/ofdm, I have >> started to receive packets. But I guess this is only 50% >> efficient in receiving packets. Not all of them have been >> receiving properly. kindly advise if I need to figure out the >> combination settings till most of them receive properly? Because >> even though I did not set any sample rate, the transmitter sent >> the information. Please help. Please excuse me if I am being >> naive in asking these. >> >> Regards, >> Dave >> >> On Mon, Sep 21, 2015 at 11:00 AM, Rama V <ramav...@gmail.com >> <mailto:ramav...@gmail.com>> wrote: >> >> Hi, >> Thanks Marcus. I will do as you have advised and approach if >> any uncertainties. >> >> Regards, >> Dave >> >> On Mon, Sep 21, 2015 at 10:16 AM, Marcus Müller >> <marcus.muel...@ettus.com <mailto:marcus.muel...@ettus.com>> >> wrote: >> >> Hi Dave, >> >> you shouldn't be modifying the python files before you >> understand what they do exactly. Please revert your >> edits, because it will be impossible to help you if you >> don't use the same scripts as we do, obviously. We've >> talked about this[1]. >> >> So: >>> Sender : benchmark_tx.py -f 2.435G -r 250k >>> Receiver : benchmark_rx.py -f 2.435G >> That's wrong! Now, your transmitter sends 250,000 bits >> per second, but your receiver expects 100.000 (the >> default value, which doesn't work with your hardware), so >> that's not good. Use the same setting for both >> benchmark_tx and benchmark_rx. >> >>> So all you say is I need to change and play with the >>> sampling rates and --tx-amplitude until the received >>> packet becomes 'n_rcvd=1' >> No. RF is not "hey, there's this correct setting, let's >> apply it everywhere"; you'll have to figure out which >> combination settings work best. Generally, I'd leave the >> --tx-amplitude untouched, because 0.25 is a sane value >> for the digital samples; what you want is analog gain, >> not digital scaling. >> >> You should really set a TX gain and a RX gain. Try around >> with a few different gain settings for RX and TX gain -- >> a good approach would be to set something like 25 dB TX >> gain, and around 50 dB RX gain, if you place your TX and >> RX antennas far enough from each other. Notice that I'm >> assuming you're using antennas, and no direct connection! >> If you're using a direct cable between TX and RX, please >> use an attenuator, because you might otherwise damage >> your hardware. >> >> To find out how to change the gains, please read the >> output of >> benchmark_tx.py --help >> and of >> benchmark_rx.py --help >> >> >> Best regards, >> Marcus >> >> >> [1] >> >> http://lists.gnu.org/archive/html/discuss-gnuradio/2015-09/msg00124.html >> >> >> On 21.09.2015 16:48, Rama V wrote: >>> >>> I have tried the following commands in the terminal >>> >>> Sender : benchmark_tx.py -f 2.435G -r 250k >>> Receiver : benchmark_rx.py -f 2.435G >>> >>> But the data packets are not being sent correctly. I >>> have been receiving the packets as ok=false. I have >>> tried modifying benchmark python scripts. Can I do the >>> modification of those scripts or evrything needs to be >>> given in the command line. Please excuse me as I am >>> slightly unable to understand. Thanks >>> >>> Regards, >>> Dave >>> >>> On Sep 18, 2015 2:21 PM, "Rama V" <ramav...@gmail.com >>> <mailto:ramav...@gmail.com>> wrote: >>> >>> Thanks for the reply Michael. I will look into that >>> as you have advised. So all you say is I need to >>> change and play with the sampling rates and >>> --tx-amplitude until the received packet becomes >>> 'n_rcvd=1' and CRC check changes to 'ok=true' from >>> the narrowband folder? >>> >>> Regards, >>> Dave >>> >>> On Fri, Sep 18, 2015 at 12:40 PM, Michael Dickens >>> <michael.dick...@ettus.com >>> <mailto:michael.dick...@ettus.com>> wrote: >>> >>> Hi Dave - I'm thinking that you are confusing >>> "--samples-per-symbol" for the sample rate. I >>> think the option you're looking for is "-r". >>> Look at the "--help" for those examples when you >>> get a chance. - MLD >>> >>> On Thu, Sep 17, 2015, at 02:01 PM, Rama V wrote: >>>> >>>> Thank you very much Michael. I will follow up >>>> on your advice. I am sorry that I wasn't able >>>> to understand some parts in GNU RADIO and >>>> didn't specify enough information. Regarding >>>> the question, I have been doing the benchmark >>>> in the digital/ narrowband/ folder. The exact >>>> commands I have been working on are >>>> >>>> Sender: benchmark_tx.py -f 2.435G --tx-gain 25 >>>> --samples-per-symbol 250000 >>>> >>>> Receiver: benchmark_rx.py -f 2.435G >>>> >>>> When I give 250kS/s, my laptop freezes. USRP is >>>> XCVR2450. So I started to give less Samples >>>> like 50kS/s so that they communicate with each >>>> other without errors. But I couldn't figure out >>>> the solution to that. So I just have a doubt >>>> whether I need to modify benchmark scripts or >>>> is it enough for the parameters I give in the >>>> command line. Thanks for the help. Please advice >>>> >>> >>> >>> >>> >>> >>> _______________________________________________ >>> Discuss-gnuradio mailing list >>> Discuss-gnuradio@gnu.org <mailto:Discuss-gnuradio@gnu.org> >>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org <mailto:Discuss-gnuradio@gnu.org> >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> >> > >
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