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Re: [Discuss-gnuradio] OFDM Implementation


From: waqasme
Subject: Re: [Discuss-gnuradio] OFDM Implementation
Date: Mon, 12 Sep 2011 04:12:58 -0700 (PDT)

hello, well i followed the same steps and now i can see the different options
by typing that command benchmark_ofdm_py. -h  .. now  am done up till that
now i asked my supervisor to provide me the extra USRP so hopefully i will
get it soon from him. till that time i am just try to understand how it
works . i have one question reagarding the OFDM signal block processing
diagram like which we can create in GNU Radio companion. For this particular
benchmark_OFDM is there any block diagram or blocks i have to create in GNU
radio companion? and one more question do i need 1 USRP1 device or two to
transmit and recieve? please let me know the procedure how to setup . i am
assuming it is connected through USB interface what else is required to make
a proper setup? thanks once again for your help. Thanks to u and johnny...
Please advise...


sumitstop wrote:
> 
> Hi,
> sorry my internet was down for almost 12 hrs... so whts the situation
> now.are you able to transmit and receive .... 
>  
> 
> waqasme wrote:
>> 
>> Hi Sumit,
>> Thanks you so much for ur detailed explanation . i really appriciate your
>> help.
>> I am following the same steps as you mentioned earlier but iam getiing
>> this message when i am entering these comands in terminal. here is the
>> messages .
>> 
>> address@hidden:~$ /usr/local/bin
>> bash: /usr/local/bin: is a directory
>> address@hidden:~$ directory/usr/local/bin
>> bash: directory/usr/local/bin: No such file or directory
>> address@hidden:~$ /usr/local/bin
>> bash: /usr/local/bin: is a directory
>> address@hidden:~$ benchmark_ofdm_tx.py-h
>> benchmark_ofdm_tx.py-h: command not found
>> 
>> when i enter this comand i get this result
>> address@hidden:~$ directory/usr/local/bin
>> bash: directory/usr/local/bin: No such file or directory
>> address@hidden:~$
>> No such file or directory.  how to access that directory? do i need to
>> run some other commands before that ? 
>> what could be the problem ? any suggestion ?
>> 
>> 
>> sumitstop wrote:
>>> 
>>> go to the directory /usr/local/bin
>>> there u will find benchmark files for ofdm (both transmission and
>>> reception)
>>> u need to type benchmark_ofdm_rx.py -h
>>> and benchmark_ofdm_tx.py -h
>>> 
>>> these will show you the parameters u can play with.
>>> 
>>> after that u can run these files by typing ./benchmark_ofdm_tx.py -f
>>> <frequency appropriate to ur daughter board>
>>> and ./benchmark_ofdm_rx.py -f <frequency appropriate to ur daughter
>>> board>
>>> 
>>> also there may be drift in the center frequency of the daughter board so
>>> u can do one thing. first run the transmitter part and see on the
>>> spectrum analyzer for the center frequency of the ofdm signal.
>>> 
>>> after that run the receiver part with that center frequency specified in
>>> the arguments.
>>> now run the transmitter again with the same frequency.
>>> 
>>> if u get timeouts then u need to play with the receiver gain and
>>> transmitter amplitude as well as the receiver center frequency.
>>> 
>>> u can change the bandwidth of the ofdm signal by changing the no of
>>> occupied tones or fft length because bw = occupied tones/ fft length
>>> 
>>> let me know ur results.
>>> 
>>> Regards
>>> 
>>> waqasme wrote:
>>>> 
>>>> hello sumit,
>>>> yah i have replaced the GMSK modulator and demodulator with OFDM
>>>> modulator and demaodulator. but i coudlnot find message source ,
>>>> ,message sink, probe signal and probe avg mag 2 with only input .. the
>>>> one i have found has input and output as well for probe avg mag 2
>>>> block... i couldnot able to find these blocks as in the simple
>>>> tranceiver diagram example they used these blocks... can you plesase
>>>> guide me where to get these blocks? 
>>>> Also you mentioned this command ( benchmark_ofdm.py -h )   is that a
>>>> command or what? because i have entered this command in terminal window
>>>> but it says command not found? and if i type in google to search it
>>>> opens a c ++ code ..what i am suppose to do with that. ?? please tell
>>>> me how to use this benchmark_ofdm.py code.. where to put this code to
>>>> make the simulation work. i am very new to GNU radio so i have no idea
>>>> what functions i can play with and how to implement this. please guide
>>>> me  like how to make this OFDM tranmission and reception  via USRP. 
>>>> iam using Linux Ubuntu maveric and GNU Radio companion 3.2.2 version...
>>>> I really appriciate your help because i have only few time left for my
>>>> Masters project. Thanks in advance i am looking forward to hear from
>>>> you.
>>>> 
>>>> Regards,
>>>> Waq.
>>>> 
>>>> sumitstop wrote:
>>>>> 
>>>>> http://pwnhome.files.wordpress.com/2011/04/simple_transceiver1.png
>>>>> see carefully....... it has a gmsk modulator in the bottom.u can make
>>>>> the bottom modulator part in another pc
>>>>> 
>>>>> benchmark programs are quite good to start with...
>>>>> u can type benchmark_ofdm.py -h to see all the parameters u can play
>>>>> with.
>>>>> 
>>>>> 
>>>>> waqasme wrote:
>>>>>> 
>>>>>> And sorry to mention in the last mail that i will be suing USRP 1 .
>>>>>> 
>>>>>> waqasme wrote:
>>>>>>> 
>>>>>>> Hi Sumit,
>>>>>>> Thank you so much for your quick response. yah i understand what
>>>>>>> your saying and i am trying to understand this document but it
>>>>>>> doesnot help much . As you mentioned use the same Tranceiver setup
>>>>>>> and only replace OFDM blocks with that. My question is in this basic
>>>>>>> tranciver diagram the used two UHD's source and sink and in the
>>>>>>> middle they use GMSK Demodulator right. but they didnot use any
>>>>>>> modulator any where in the design. Now i am confused what blocks i
>>>>>>> have to replace with OFDM blocks??? Please try to explain in bit
>>>>>>> detail so i can design it properly . 
>>>>>>> OR you mentioned other option that use benchmark_OFDM.py file .
>>>>>>> Somebody already told me about this benchmark file. but its just C++
>>>>>>> code . i am quite new to GNU radio and dont know much about the
>>>>>>> functions how it works. 
>>>>>>> Please let me know how to use that benchmark_OFDM.py file in order
>>>>>>> to make the simulation design? do i have to download the file or
>>>>>>> what? how it works ?? let me know if you know about the process how
>>>>>>> to compile and run that code in GNU radio.
>>>>>>> 
>>>>>>> Thanks for ur help and support really appriciate that...
>>>>>>> 
>>>>>>> Regards,
>>>>>>> 
>>>>>>> Waqas.
>>>>>>> 
>>>>>>> 
>>>>>>> sumitstop wrote:
>>>>>>>> 
>>>>>>>> Try to understand these 
>>>>>>>> 
>>>>>>>> http://pwnhome.wordpress.com/2011/04/26/intro-to-gnuradio-and-the-usrp-part-5-simple-transceiver/
>>>>>>>> 
>>>>>>>> here u need to put those ofdm blocks .. thats it.... also go
>>>>>>>> through some modifications as written in umit,
>>>>>>>> 
>>>>>>>> 
>>>>>>>> http://pwnhome.wordpress.com/2011/04/19/intro-to-gnuradio-and-the-usrp-part-4/
>>>>>>>> 
>>>>>>>> or else work with benchmark_ofdm.py  its very easy.. :)
>>>>>>>> 
>>>>>>>> may i know what daughter boards do you have... 
>>>>>>>> 
>>>>>>>> 
>>>>>>>> 
>>>>>>>> 
>>>>>>>> 
>>>>>>>> waqasme wrote:
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> Hello sumit,
>>>>>>>>> Thanks for your help i went through that document that you refered
>>>>>>>>> to, and i tried to implement that OFDM transmitter part. This
>>>>>>>>> document only explain about OFDM flow graph or transmitter. Is
>>>>>>>>> there any other document or information related to OFDM modulator
>>>>>>>>> and demodulator (Transceiver)? i haver to implement OFDM
>>>>>>>>> transmission and reception via USRP. i will really appriciate if
>>>>>>>>> you can help me that or someone else who knows how to implement by
>>>>>>>>> using GNU radio companion.
>>>>>>>>> Thanks in advance.
>>>>>>>>> Regards,
>>>>>>>>> Waq.
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>> 
>>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>> 
>>>>>> 
>>>>> 
>>>>> 
>>>> 
>>>> 
>>> 
>>> 
>> 
>> 
> 
> 

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