Re: some results about D8PSK (problems)

Hi, Stefan

I have tried patch file you gave me, but the result was even worse. The
receiver cannot synchronize with the transmitter.

I also tried the DBPSK and DQPSK scheme without your patch file. I found
there is a big problem with USRP. After having TX and RX rest for 20
mins, the communication between them are so good that the PDR detected
at the RX is almost 99%, but after those two USRPs run for a while, say
10 mins, the communication quality deteriorates rapidly, which means the
synchronization was worsen. So, the conclusion could be reached that
USRP could not keep on running for a long time, even 10 mins’ running
would exhaust our USRP? I do not know whether my conclusion is right or
not, but if I were wrong, please pick out my problem! Thanks a lot!


— On Thu, 3/19/09, Stefan Brüns [email protected] wrote:

From: Stefan Brüns [email protected]
Subject: Re: [Discuss-gnuradio] some results about D8PSK (problems)
To: [email protected]
Date: Thursday, March 19, 2009, 11:18 AM

Hi Bill,

I mentioned some problems with carrier offsets between different USRPs
daughterboards, for RFX non-MIMO boards) when you reported on DBPSK. I
that error rate vastly improved when I factored the offset directly into
frequency arguments of the benchmark_{rx,tx}.py programs.

Although the costas loop should be able to deal with carrier offsets, as
as these stay in the allowed range, there is a bug in the mpsk receiver
block, which leads to bad performance for larger offsets. Can you try
attached patch? (Lacking time to test it myself atm …)


On Wednesday 18 March 2009 22:19:50 Bill S. wrote:

reviewed the README file for the and, it

Stefan Brüns / Bergstraße 21 / 52062 Aachen
mailto:lurch at http://www.kawo1.rwth-aachen…de/%7Elurchi/
phone: +49 241 53809034 mobile: +49 151 50412019

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