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" <address@hidden> wrote:
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>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
>>>>
>>>>
>>>
>>>
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