Re: [Discuss-gnuradio] Multiple-Transmitter OFDM

[Ramazan Çetin]

Hi Michael,

Thank you for your suggestions. After arranging the amplitude of signal.  I also used multiply tag block due to resampling process. Now i can transmit using multi-channel.

I want to make a video streaming using two channels. Thus, i connected my OFDM tx and rx to TUNTAP interface. I can ping devices from each other. I also make a throughput test using iperf3 tool. 

I have made a stream using these steps:

- Get a video from Raspberry Pi using GNU Radio TCP client from USRP1.

- Connect TCP Client to TCP server to send incoming video to  USRP2.

- In USRP2 i am playing video using mplayer (mplayer behaves like TCP client).

But after i started video streaming from the interface, after a while one of the nodes (transmitter or receiver, i got from both of them in different tries) starts giving "tP" error. Actually, in the beginning there is no such an error. I can play video for several seconds.

My FGs are attached (U2 sends video and U0 receives it. Video_client_server.grc runs in sender) .

If you have an idea, i would appreciate it. Thank you.

Best regards.

Ramazan

On 27.06.2019 03:40, Michael Dickens wrote:

Hi Ramazan - The "tP" means that a timed transmit came too early. Say you want to transmit exactly every second (via timed samples), but you provided UHD with a burst of 2 seconds of data. You will have a new timed command before the first burst is finished. Hence, UHD will print "tP". I'm guessing with this info you can work out why there are too many samples per timed command going into the UHD sink.

The "U" as you note is an underrun; as these are happening just at app startup, and not during steady-state runtime, I'd guess it has something to do with getting the data flowing between the E310 and your host running GR that you can safely ignore.

Hope this is useful! - MLD

On Wed, Jun 26, 2019, at 1:40 PM, Ramazan Çetin wrote:

Hi Michael,

We have implemented one channel OFDM using rational resampler and pfb synthesizer and multiply tag block. It's working and we can receiver packets over the air. Thanks for suggestions.

We have also tried to implement two channels. We have resampled OFDM signals to 500KHz using rational resampler and combine them using synthesizer. When we run the FG, we can receive from both of the channels in the receiver but i am seeing lots of tPtPtPtP and some Us. The log is given in below:

root@rcetin-W540:~/workarea/installs $ /home/rcetin/workspace/gohm/bitbucket/physicallayergnuradio/resampled_ofdm.py

linux; GNU C++ version 7.3.0; Boost_106501; UHD_003.009.002-0-gf18abe54

-- Initializing core control...

-- Performing register loopback test... pass

-- Performing register loopback test... pass

-- Performing register loopback test... pass

-- Performing CODEC loopback test... pass

-- Performing CODEC loopback test... pass

-- Setting time source to internal

-- Asking for clock rate 16 MHz

-- Actually got clock rate 16 MHz

-- Performing timer loopback test... pass

-- Performing timer loopback test... pass

set_min_output_buffer on block 31 to 65536

ControlPort Monitor running.

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gr::log :INFO: controlport - Apache Thrift: -h rcetin-W540 -p 37521

monitor::endpoints() = -h rcetin-W540 -p 37521

running: ['gr-perf-monitorx', 'rcetin-W540', '37521']

Press Enter to quit: tPtPUtPtPUtPUtPtPtP/home/rcetin/workarea/installs/bin/gr-perf-monitorx requires networkx and matplotlib. Please check that they are installed and try again.

tPUUtPtPtPtPtPUtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPUtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPUtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPUtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtPtP

So, do you have any idea what the reason of PtPt?

Another problem is U (underrun). Does underrun related with CPU capability or network (We are using E310 in network mode)?

Thank you so much for suggestions. The FG is attached.

Best regards.

Ramazan

resampled_ofdm_master_U2.grc
Description: XML document

resampled_ofdm_slave_U0.grc
Description: XML document

video_client_server.grc
Description: XML document