Okay I will do that. Thanks! On the receiver side I know the equalizer block does the phase offset correction but usually pilot tones in each OFDM symbol are used for that. When I looked at the file *gnuradio <https://github.com/gnuradio/gnuradio>/gr-digital <https://github.com/gnuradio/gnuradio/tree/master/gr-digital>/lib <https://github.com/gnuradio/gnuradio/tree/master/gr-digital/lib>/ofdm_frame_equalizer_vcvc_impl.cc* I dont see that happening. If for every OFDM symbol that we receive, I want to access the frequency bin of the pilot tones how can I do that with the current equalizer block?
On Sat, Mar 25, 2017 at 8:55 AM, Bastian Bloessl <[email protected]> wrote: > Hi, > > Am 25.03.2017 um 16:12 schrieb Qurat-Ul-Ann Akbar: > >> Thanks for pointing me to the file. This list of pilot tones with >> different polarities seems to be hard coded. Is there any way of >> changing the amplitude value of this complex number encoded on the pilot >> tone. E.g. if I want to change all the pilot tone values for frequency >> bin +7 from 1 to 1.2 how can I do that dynamically without hard coding >> these values ? >> >> Something like this (1,1,1,-1) -> (1,1,1.2,-1) and so on... >> > > That, rather specific use-case, is AFAIK not supported by the upstream > block. It is, however, straightforward to create your own block based on > the OFDM Carrier Allocator. The Wiki has lots of useful information. In > particular, > https://wiki.gnuradio.org/index.php/OutOfTreeModules > > To change the amplitude of the pilots interactively, you might want to add > a callback to the block (to change it from GUI elements) or add a message > port to allow other blocks to change the amplitude. > > Best, > Bastian > > > >> >> On Fri, Mar 24, 2017 at 2:57 PM, Bastian Bloessl <[email protected] >> <mailto:[email protected]>> wrote: >> >> Hi, >> >> On 03/24/2017 08:44 PM, Qurat-Ul-Ann Akbar wrote: >> > How is a particular polarity picked for the pilot tones in each >> symbol >> > with 52 subcarriers in GNU Radio? I can see the list in the OFDM >> Carrier >> > Allocator block but where is this exactly happening in the code? >> >> the pilots are copied here: >> >> https://github.com/gnuradio/gnuradio/blob/master/gr-digital/ >> lib/ofdm_carrier_allocator_cvc_impl.cc#L185-L189 >> <https://github.com/gnuradio/gnuradio/blob/master/gr-digital >> /lib/ofdm_carrier_allocator_cvc_impl.cc#L185-L189> >> >> The vector "d_pilot_carriers" is created from the list of pilots that >> you mentioned (i.e. the argument of the carrier allocator block). >> This list contains pilots according to the polarity pattern given in >> the >> standard. >> >> Best, >> Bastian >> >> > >> > >> > >> > On Mon, Mar 20, 2017 at 3:37 PM, Bastian Bloessl <[email protected] >> <mailto:[email protected]> >> > <mailto:[email protected] <mailto:[email protected]>>> wrote: >> > >> > Hi, >> > >> > On 03/20/2017 09:17 PM, Qurat-Ul-Ann Akbar wrote: >> > > Hi, >> > > >> > > Thank you. I got it! I have another question. In the OFDM >> Carrier >> > > Allocator block, there are 127 values for pilot symbols each >> of them >> > > either (1,1,1,-1) or (-1,-1,-1,1). The pilot frequencies are >> > > (-27,-7,7,21) according to IEEE 802.11 standard. But I do not >> understand >> > > why are there 127 symbol values. Can you kindly explain that ? >> > >> > The four values indicate the four pilot symbols (on subcarriers >> -21, -7, >> > 7, 21). With 802.11, the pilots change polarity based on a >> predefined >> > sequence (of length 127). It is in this exact format also in the >> > standard (Section 18.3.5.10 of the 2012 version). >> > >> > Best, >> > Bastian >> > >> > >> > >> > > >> > > On Mon, Mar 20, 2017 at 12:09 PM, Bastian Bloessl < >> [email protected] <mailto:[email protected]> <mailto:[email protected] >> <mailto:[email protected]>> >> > > <mailto:[email protected] <mailto:[email protected]> <mailto: >> [email protected] >> <mailto:[email protected]>>>> wrote: >> > > >> > > Hi, >> > > >> > > >> > > > On 20 Mar 2017, at 17:50, Qurat-Ul-Ann Akbar < >> [email protected] >> <mailto:[email protected]> >> > <mailto:[email protected] >> <mailto:[email protected]>> >> > > <mailto:[email protected] >> <mailto:[email protected]> >> > <mailto:[email protected] >> <mailto:[email protected]>>>> wrote: >> > > > >> > > > If I want to make changes in the PHY hierarchical >> block, can >> > I just make changes in the grc file available in the examples >> folder >> > and then recompile ? Because I cant file a .cc file in the lib >> > folder in IEEE_802.11 module and the source code for most >> blocks is >> > in there. >> > > > >> > > >> > > I’m afraid I don’t get the question, but if you don’t >> see any .cc >> > > files in the lib folder, you might want to clone the >> repository >> > > again, because actually there are some >> > > >> > > https://github.com/bastibl/gr-ieee802-11/tree/next/lib >> <https://github.com/bastibl/gr-ieee802-11/tree/next/lib> >> > <https://github.com/bastibl/gr-ieee802-11/tree/next/lib >> <https://github.com/bastibl/gr-ieee802-11/tree/next/lib>> >> > > <https://github.com/bastibl/gr-ieee802-11/tree/next/lib >> <https://github.com/bastibl/gr-ieee802-11/tree/next/lib> >> > <https://github.com/bastibl/gr-ieee802-11/tree/next/lib >> <https://github.com/bastibl/gr-ieee802-11/tree/next/lib>>> >> > > >> > > If you only change the flow graph in GRC, you don’t have >> to >> > > recompile the module (i.e., recompile c++ code). Just >> click on the >> > > “generate” button (or press F5) this will rebuild the PHY. >> > Then the >> > > other flow graphs will automatically use the new version >> of >> > the PHY. >> > > >> > > Best, >> > > Bastian >> > > >> > > >> > >> > >> >> >>
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