Well, you can go ahead and at least to a degree enforce a known relative phase between transmitter and receiver, but yeah, without extensive external synchronization effort (e.g. GPSDOs – hi there, u- blox :) ), the receiver phase is random relative to the transmitter's phase. So, the distance can't be recovered from a one-way transmission.
Best regards, Marcus On Fri, 2019-06-07 at 10:21 +0000, Jonas Manthey wrote: > Hi Andrew, > > What do you mean by “information from the carrier data”? I’m no OFDM expert, > but my intuition tells me that in a zero-IF architecture (which I assume your > USRP has) any carrier phase information is lost. There’s some results when > googling for “OFDM ranging” maybe that helps. > > Cheers, > Jonas > > From: Discuss-gnuradio > [mailto:discuss-gnuradio-bounces+jonas.manthey=u-blox....@gnu.org] On Behalf > Of Andrew Wolfram > Sent: Donnerstag, 6. Juni 2019 01:20 > To: discuss-gnuradio@gnu.org > Subject: [Discuss-gnuradio] Determining distance from OFDM signals > > Hi, > > I'm trying to alter the file ofdm_txrx.py > (https://github.com/gnuradio/gnuradio/blob/master/gr-digital/python/digital/ofdm_txrx.py) > to get phase information from the carrier data so I can calculate an > approximate distance between two USRP devices. Ideally I want to grab data > from one of the blocks in the rx pipeline in the above python file after the > frequency/timing corrections have been applied. I tried using the data after > the serializer block, but it appears that this has no phase information. I > tried with the equalizer block output but I'm not sure how to interpret its > output data. For my particular payload with 300 occupied carriers and an fft > size of 512 only the first 214 items of the equalizer output vector have any > phase information, so I'm somewhat confused. Any ideas? > > Thanks, > Andrew > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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