Re: [Discuss-gnuradio] Determining distance from OFDM signals

[CEL]

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=address@hidden] On Behalf Of 
> Andrew Wolfram
> Sent: Donnerstag, 6. Juni 2019 01:20
> To: address@hidden
> 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
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