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Re: [Discuss-gnuradio] how to deal with "underride"

From: zhengxiangwei
Subject: Re: [Discuss-gnuradio] how to deal with "underride"
Date: Wed, 12 Dec 2012 23:20:07 +0000

I think frequency offset may not be the reason.

The attachment is the oscilloscope picture. The first one use DBPSK modulation, which can be received by simple_trx.py. The second one use GMSK modulation, which can be successfully  received by simple_trx.py.

I wonder is there any reason may cause simple_trx.py fail to work using DBPSK.
Thank you.

Xiangwei Zheng
Research Assistant
ECE Department, Virginia Tech
Office: Durham Hall 365
Tel: 540-553-6235

From: address@hidden
Date: Wed, 12 Dec 2012 12:07:31 -0500
Subject: Re: [Discuss-gnuradio] how to deal with "underride"
To: address@hidden
CC: address@hidden

On Wed, Dec 12, 2012 at 11:49 AM, zhengxiangwei <address@hidden> wrote:

I compared the difference when using GMSK and PSK in simple_trx.grc which use radio_hier.grc.
When use GMSK, 
it calls
gr_fir_fff: using SSE

When use PSK,
it calls 
gr_fir_ccf: using SSE
gr_fir_ccc: using SSE

Also I compare with benchmark_tx,
when use PSK
it calls gr_fir_ccf: using SSE

when use gmsk
it calls
gr_fir_fff: using SSE

I know c, f means different data type: complex and float.

Is it the reason why PSK fail to work? which calls additional  "gr_fir_ccc: using SSE"?

If it is not the reason, I will dive into framer, which may also cause failure in TX.
Thank you. 

Xiangwei Zheng

No, this is not the reason. This is probably a channel filter used in PSK signals and not in the GMSK signals.

Most likely the reason is frequency offset or too much or too little power.


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