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Re: [Discuss-gnuradio] ofdm channel estimation

From: xianda
Subject: Re: [Discuss-gnuradio] ofdm channel estimation
Date: Tue, 15 Jul 2014 21:11:05 +0800 (CST)

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,

At 2014-07-15 08:48:15, "Marcus Müller" <address@hidden> wrote: >-----BEGIN PGP SIGNED MESSAGE----- >Hash: SHA1 > >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" <address@hidden> >> 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" <address@hidden> >>>> 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 >address@hidden >>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradi >>>> >>>> >>> >>> >>> _______________________________________________ Discuss-gnuradio >>> mailing list address@hidden >>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>> >>> >>> _______________________________________________ Discuss-gnuradio >>> mailing list address@hidden >>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >-----BEGIN PGP SIGNATURE----- >Version: GnuPG v1 >Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ > >iQEcBAEBAgAGBQJTxSMPAAoJEBQ6EdjyzlHtRwEH+gPol6VhuE5BBqyq5GUD7H9P >GhTufylcZhwuK5XLbZg1l5ZrcqrcJu8+CZRFmWuK2vIml4JhzVPre5gPSbYeRdFs >e+aZ+mT3TN62oXXurvq+YM6mnBdewR2bi8h/DtkC77OkB5SvL6j6rREWSg73flCB >/sh2hgHuQkJ8d2sh8ut0L1NF6rlbB3l+unwEgjGeLnDyH3fdFjfUDPlh7OiX318w >GmfPasCiSMMmcSqXCIaXcHaaVF/cdip7Yd8LQACMKJvZBT9AvGh5i725z3Drytdl >20B69ymrWD93bEdBjN7WAyAAvDJVbE6nWv1gXuUYfkbnGHwIaGomXfU8PQrPY14= >=qRmz >-----END PGP SIGNATURE----- > >_______________________________________________ >Discuss-gnuradio mailing list >address@hidden >https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

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