XD, I'm having real trouble understanding what you're doing.
Try this: generate white noise and put it into the detector. Do you see any 1s? I would guess no. M On 07/15/2014 03:11 PM, xianda wrote: > Hi Marcus: > Thank you.Sorry for that. > I wrongly use the read_complex_binary to analyse the > detect at the second time.As I said(But I test again and again,the > rx_detect don't exist 1.And some little value approach 0 exists.).If I > use the read_char_binary to analyse the detect.There is 1 under every > test.I said the truth.It isn't stochastic problems maybe.And I attached > my modified rx_ofdm.grc.You can run it when no tx signal exist.And you > will see r_detect.dat will exist 1.(In matlab,use the > read_char_binary.m).And a1.dat and a.dat isn't null.(In matlab,use the > read_complex_binary.m).You can test it.Thank you. > Maybe I am wrong,please correct me.Thank you. > Best regards, > xd > > > > > > At 2014-07-15 08:48:15, "Marcus Müller" <[email protected]> wrote: > Hi Xianda, > > how should we possibly tell? You expect us to be able to guess what is > going wrong with your measurement, in an environment that is unknown > to us, using a receiving antenna, modified flowgraph and tx signal > that you did not really define. > > As Martin said, if a detector outputs a 1, it might be a false alarm, > also known as bad luck. > > With stochastic problems, you always have to make a trade off between > false alarm rate and type II errors. This is called receiver operating > characteristic. With most detectors, you can adjust their parameters > to accommodate your false alarm rate/detection rate needs. > > Greetings, > Marcus > > > > On 15.07.2014 12:56, xianda wrote: >> Oh,I guess that because i receive signal which at the frequency of >> 2.45e9.It is like the wifi.May be I receive the wifi signal?Am i >> right? Thank you. > > > > > > > > > >> At 2014-07-15 05:17:35, "Martin Braun" <[email protected]> >> wrote: >>> On 07/15/2014 09:39 AM, xianda wrote: >>>> Hi Martin: Thank you for your kindly reply. Another question I >>>> want to ask. When I use the rx_ofdm,I add a UHD:USRP >>>> Source.(Environment: USRP N210)I know when the block Schmidl >>>> &Cox OFDM synch. detect the signal,the port "detect" will >>>> output 1.And I test it.I use the rx_ofdm when I don't use the >>>> tx_ofdm.It means that no signal exist.But I find 1 in the port >>>> "detect".Why?When no signal exist,it should output 0.Why I see >>>> 1 from it? >>> >>> ...bad luck? It's not impossible to generate false alarms. What >>> did you feed the block? >>> >>> Martin >>> >>> >>> >>>> Thank you so much. Best regards, xd >>>> >>>> >>>> >>>> >>>> At 2014-07-14 04:37:37, "Martin Braun" <[email protected]> >>>> wrote: >>>>> On 07/13/2014 01:06 PM, xianda wrote: >> Hi all: >> Have you >>>>> ever using >>>> the >> gnuradio/gr-digital/examples/ofdm/rx_ofdm.grc?And I >>>> change the >> rx_ofdm.py as follows: >> >>>> self.connect((self.digital_ofdm_chanest_vcvc_0, 1), >> >>>> blocks.file_sink(gr.sizeof_gr_complex * fft_len, >>>> 'channel-estimate.dat')) >> And i use the matlab: > >Please >>>> read the fine manual: >>>>> http://gnuradio.org/doc/doxygen/classgr_1_1digital_1_1ofdm__chanest__vcvc.html#details. >>>>>> >>>>> > The channel estimate is on a tag. > >M > >>>>> _______________________________________________ >>>>> >Discuss-gnuradio >>>> mailing list >[email protected] >>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradi >>>> >>>> >>> >>> >>> _______________________________________________ Discuss-gnuradio >>> mailing list [email protected] >>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>> >>> >>> _______________________________________________ Discuss-gnuradio >>> mailing list [email protected] >>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >>_______________________________________________ >>Discuss-gnuradio mailing list >>[email protected] >>https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > > > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >
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