Hi,
I guess, the receiver cannot synchronize to our transmitters. Is there a
way for using occupied carriers for synchronization instead of all
carriers in schmidl cox?
Best regards.
On 24.06.2019 15:00, Ramazan Çetin wrote:
Hi Michael,
Firstly, thank you for your suggestion. I have tried your solution and
i have transmitted two signals using PFB synthesizer. At the receiver,
i have used a PFB channelizer. In simulation, this system works
perfectly. I could receive two different files at the receiver from
two different transmitters.
But when i tried this system on E310s, it fails. At the transmitter,
E310 gives tGtGtGtGtGtGtGtG errors (I know this is related with length
tags but i have already provided tag to USRP). At the receiver, it
cannot receive signals. It gives this error:
gr::log :INFO: header_payload_demux1 - Parser returned #f
gr::log :INFO: packet_headerparser_b1 - Detected an invalid packet at
item 38
gr::log :INFO: header_payload_demux1 - Parser returned #f
gr::log :INFO: packet_headerparser_b1 - Detected an invalid packet at
item 76
gr::log :INFO: header_payload_demux1 - Parser returned #f
gr::log :INFO: packet_headerparser_b1 - Detected an invalid packet at
item 114
gr::log :INFO: header_payload_demux1 - Parser returned #f
gr::log :INFO: packet_headerparser_b1 - Detected an invalid packet at
item 152
gr::log :INFO: header_payload_demux1 - Parser returned #f
gr::log :INFO: packet_headerparser_b1 - Detected an invalid packet at
item 190
gr::log :INFO: header_payload_demux1 - Parser returned #f
gr::log :INFO: packet_headerparser_b1 - Detected an invalid packet at
item 228
This is obviously related with HPD. But, it does not give this error
continuously while signal is transmitting. Normally, if header cannot
be decoded, this error should be seen continuously. Instead, it just
gives at the beginning of signal.
I have attached three GRC FGs. pfb_test is simulation environment that
works perfectly. pfb_transmitter and pfb_receiver are USRP FGs.
Do you have any idea about this situation?
Best regards.
Ramazan
On 20.06.2019 21:16, Michael Dickens wrote:
Hi Ramazan - Hmmm ... I'm not coming up with anything greatly useful
when using a single OFDM block for Tx. Alternatively you could use a
2 channel PFB synthesizer on Tx, with 2 separate OFDM Tx and feed
them into the synthesizer. On Rx use a PFB channelizer and take its 2
outputs to 2 separate OFDM Rx. The complexity of the PFBs will depend
on the filtering required to keep the OFDM channels separate enough.
Maybe others have useful ideas of how to do what you're looking for?
Hope this is useful! - MLD
On Thu, Jun 20, 2019, at 10:49 AM, Ramazan Çetin wrote:
Hi MLD,
You are right. I guess, one of the transmitters' preamble overlaps
another's data. (Because gnuradio sends preamble in all carriers). I
have attached my receiver and transmitters' FGs. Both of them uses
256 carrier OFDM. One transmitter use half of the carriers as
occupied and another uses other half. I guess our receiver structure
is wrong.
Can you suggest a way for implementing multi user OFDM system?
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