Re: [Discuss-gnuradio] channel estimation in gnuradio narrowband

[yeran]

Hi Alex,

yes, I'm using the original generic_mod_demod.py, and just adding a file_sink after the time_recov block, so there is a freq_recov before. But thanks all the same! :)

Ada

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Date: Thu, 30 May 2013 00:28:45 -0500
Subject: Re: [Discuss-gnuradio] channel estimation in gnuradio narrowband
From: address@hidden
To: address@hidden
CC: address@hidden

So, actually, your code already has the freq recov block? If so, I really have no idea on how to solve your problem.

On Wed, May 29, 2013 at 11:34 PM, yeran <address@hidden> wrote:

Hi Alex,

I have read the  generic_mod_demod.py and find the fll block you mentioned is in freq_recov block, which is before the time_recov block. However, the file sink I use to collect data is after time_recov block. So I think in this case, it's already been through carrier frequency correction. But as shown in the picture I attached with the original email, the channel I get still seems to be with carrier frequency. 

Please correct me if there is a misunderstanding in my thought!

Thanks! Look forward to your reply!!

Best,

Ada

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Date: Wed, 29 May 2013 22:27:14 -0500

Subject: Re: [Discuss-gnuradio] channel estimation in gnuradio narrowband
From: address@hidden

To: address@hidden; address@hidden

FLL = Frequency lock looping. 

The corresponding C++ block is digital_fll_band_edge_cc. 

and you can find the usage example in generic_mod_demod.py in /gnuradio/gr-digtial/python. 

There are some discussions within this community before, just search it for how to use it properly.

On Wed, May 29, 2013 at 10:07 PM, yeran <address@hidden> wrote:

Hi Alex,

Thank you for your prompt reply! 

But I don't quite understand what you said about FLL filter for CFO correction. What is the full name of the FLL filter? In which block?

Thanks! Look forward to your reply!

Ada

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Date: Wed, 29 May 2013 21:55:29 -0500
Subject: Re: [Discuss-gnuradio] channel estimation in gnuradio narrowband
From: address@hidden
To: address@hidden
CC: address@hidden

I don't think the RRC filter is used for carrier frequency correction. In gnuradio, the FLL filter can be used for CFO correction. 

Please correct me if I am wrong.

On Wed, May 29, 2013 at 9:43 PM, yeran <address@hidden> wrote:

Hi everyone,

I’m doing channel estimation in gnu radio narrowband. But the result is different than I expect.

I’m using the example in grc, uhd_tx_dpsk.grc and uhd_rx_dpsk.grc. Send vector (255,255,255) repeatedly using BPSK.  At the receiver, I add a file sink after the time_recov block and store the data.

Y=X*H +N,  the data after time_recov is Y, and in BPSK, when sending 1 is mapped to 1+0j, so X=1+0j. Thus, Y/X is the estimate channel frequency I get. I plot the absolute value of the channel frequency and get a figure as in the attachment. But it seems that it has the carrier frequency with it. It is so well organized and changes regularly. But I’m pretty sure that before the file sink, in the time_recov block, the rrc filter already take off the carrier frequency.

Has anyone come across the same problem before? Or find any mistakes or suggestions on my method? Please let me know!

Thank you very much!

Ada 

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Alex,

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Alex,

Dreams can come true �C just believe.

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Alex,

Dreams can come true �C just believe.