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Re: [Discuss-gnuradio] About GNURadio

From: Kyeong Su Shin
Subject: Re: [Discuss-gnuradio] About GNURadio
Date: Tue, 14 May 2019 02:03:49 +0000

Hello Hasan,

If you are transmitting from one hardware to another hardware, that is an expected behavior (due to various hardware imperfections - especially the master clock mismatch. ). Synchronization and equalization blocks on the receiver flowgraph must correct such problems. If you have such blocks on the receiver, but the angles of the symbols are rotating, then you know that there are problems on your synchronizer codes.

Also, please note that many GNU Radio PSK demodulation tutorials use blind synchronization & equalization methods using a polyphase clock sync, CMA equalizer, and a costas loop, which may not work very well unless the transmitter starts first and is persistently transmitting strong signals to the receiver. You are better off using non-blind synchronization & equlization methods (using training symbols and a matched filter). Unfortunately, I haven't done that using GNU Radio's synchronization blocks (so I cannot give much recommendations about that).

Finally, the "DPSK Mod" block in your Tx flowgraph is deprecated, and I am not sure why it has a Polyphase Clock Sync (which is something that I expect to see on the Rx flowgraph).


Kyeong Su Shin

보낸 사람: Hasan Konanç <address@hidden> 대신 Discuss-gnuradio <discuss-gnuradio-bounces+address@hidden>
보낸 날짜: 2019년 5월 13일 월요일 오후 8:21:50
받는 사람: address@hidden
제목: [Discuss-gnuradio] About GNURadio


I'm Hasan. We are working on GNURadio. When broadcasting from a USRP device, we are experiencing some difficulties in the broadcast from other USRP devices.

For example, we send a 4PSK modulated signal from the transmitter. Then we observe the signal sent from the constellation diagram. However, this constellation diagram is constantly rotating around itself, with a continuous phase shift.

How do you think we can handle this problem?


Thank you so much.

Good work.



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