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.
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?