Re: [Discuss-gnuradio] Resampling with USRP

[Dincer Beken]

I just mixed up things I guess.

 

After searching a bit more, I saw that the taps below whre for the frac. Resampler. I again looked at python in the NONE case and saw the def design_filter function and implemented it in C++. Did not reached my ultimate goal yet but I think that this is the real solution for the taps in C++ code.

 

Von: Dincer Beken [mailto:address@hidden
Gesendet: Dienstag, 8. Oktober 2013 14:55
An: address@hidden
Cc: address@hidden
Betreff: Re: [Openlte-discuss] Resampling with USRP

 

Interpolator_taps.h in include file solves my issue I guess. Could not see it before.

 

For the LTE Part, I still am not sure if this is ok for the openLTE project as resampling taps.

 

 

Von: Dincer Beken
Gesendet: Dienstag, 8. Oktober 2013 14:32
An: Dincer Beken; address@hidden
Cc: address@hidden
Betreff: AW: Resampling with USRP

 

I found the folder: General interpolator Taps (over 3.6). That Is probably my answer…

Though I don’t know if I have to separately install it…

 

Von: Dincer Beken [mailto:address@hidden]
Gesendet: Dienstag, 8. Oktober 2013 10:00
An: address@hidden
Cc: address@hidden
Betreff: [Openlte-discuss] Resampling with USRP

 

Hi all,

 

I want to implement a low pass for the resampler. I am going to use not a polyphase filterbank, because I don’t know its details.

 

My USRP output is configured to 10Msps. I want to catch a 10Mhz LTE carrier. I want to use a normal resampler with decimation 1000 and interpolation 1536. I guess, need to fill in the taps part with an appropriate low pass filter (H(e^jw)).

 

 

Since I never implemented in practice a resampler, according to the DSP books, I need to have a low pass filter with gain of L(1536), if I want to use a resampler with non-integer rate (1,536). The low pass filter will have a gain of 1536.  

 

 

So I have to following questions:

 

1-      Can I use the rational_resampler_base_ccc ­or rational_resampler_base_ccf? I am tending more towards the ccc, sing H(e^jw) is usually complex. Or do I need to use a PFB filter?

2-      Is a gain with 1536 really necessary? I fear of destroying the Daughterboard.

3-      For the low pass filter, I want to use the gr::filter::firdes::low_pass (1). The sampling rate is L (15,36M). No idea about cutoff frequency and transition with. Can anyone please, please help me with those parameter..

a.       http://gnuradio.org/doc/doxygen/classgr_1_1filter_1_1firdes.html#a772eb5c542093d65518a6d721483aace

I would be very happy, if I could get some help. Especially from anyone who tried to implement openLTE on the USRP.

 

Thanks,

Dincer