[srslte-users] Problem with srsLTE captures using bladerf

[Ismael Gomez]

Thanks for the contribution Nicola, looks great!

I'll add that to the code as soon as possible.

On Wed, 23 Mar 2016 at 11:00 Nicola Bui <nicola.bui at imdea.org> wrote:

> Dear Ismael, all,
>
> I solved by changing the bandwidth configuration for bladerf set rx_srate
> function: since, bladerf can only choose one out of a set of filters and,
> lte does not use all the carriers that are recorded I set the bandwidth to
> be:
> bw = rx_srate * used/fftlen
> then the board piccks the closest filter. In particular, I have been able
> to remove the high power noise using a 10MHz filter on a 11.52 Msps
> sampling rate (filtering down to 8.75 MHz also works, but I am afraid the
> filter start attenuating the signal).
>
> Below is a snippet of my code.
>
> ---------------------------------------------------------------------
> double rf_blade_set_rx_srate(void *h, double freq)
> {
>   uint32_t bw;
>   rf_blade_handler_t *handler = (rf_blade_handler_t*) h;
>   int status = bladerf_set_sample_rate(handler->dev, BLADERF_MODULE_RX,
> (uint32_t) freq, &handler->rx_rate);
>   if (status != 0) {
>     fprintf(stderr, "Failed to set samplerate = %u: %s\n", (uint32_t)
> freq, bladerf_strerror(status));
>     return -1;
>   }
>   if (handler->rx_rate < 2000000) {
>  status = bladerf_set_bandwidth(handler->dev, BLADERF_MODULE_RX,
> handler->rx_rate, &bw);
>  if (status != 0) {
>    fprintf(stderr, "Failed to set bandwidth = %u: %s\n", handler->rx_rate,
> bladerf_strerror(status));
>    return -1;
>  }
>   } else {
>  status = bladerf_set_bandwidth(handler->dev, BLADERF_MODULE_RX,
> handler->rx_rate*0.8, &bw);
>  if (status != 0) {
>    fprintf(stderr, "Failed to set bandwidth = %u: %s\n", handler->rx_rate,
> bladerf_strerror(status));
>    return -1;
>  }
>   }
>
>   printf("Set RX sampling rate %.2f Mhz, filter BW: %.2f Mhz\n", (float)
> handler->rx_rate/1e6, (float) bw/1e6);
>   return (double) handler->rx_rate;
> }
> ---------------------------------------------------------------------
>
> Best regards,
> Nicola Bui
>
> Research Engineer
> IMDEA Networks Institute
> Av. Mar del Mediterraneo, 22
> 28918 - Leganés (Madrid) - Spain
> mobile: +34 657 633 987
> phone: +34 91 481 6986
> fax: +34 481 6965
>
> On Wed, Mar 23, 2016 at 12:02 AM, Ismael Gomez <
> ismael.gomez at softwareradiosystems.com> wrote:
>
>> Hi,
>>
>> It could also be the LO leakage. I think you can mitigate that by adding
>> some frequency offset to the frequency tunning process. You can play with
>> the bladeRF driver as much as you want. The interface is implemented in
>> srslte/lib/rf/src/rf_blade_imp.c
>>
>> Hope that helps, let me know if you need any further info
>>
>> Cheers
>> Ismael
>>
>> On Tue, 22 Mar 2016 at 17:24 Nicola Bui <nicola.bui at imdea.org> wrote:
>>
>>> Dear all,
>>>
>>> first of all let me thanks the team for the great job and the support
>>> they gave me throughout my development.
>>> I am capturing some lte traces with both a bladerf x40 and usrp x310.
>>> Both are fine in most of the cases, but I found the bladerf x40 to
>>> introduce some high power noise inband. You can find attached two pictures
>>> related to similar captures:
>>> - frequency 1854.1 MHz
>>> - samplerate 11.52 Msps
>>> - resource blocks 50
>>> As you can see the bladerf capture shows two high power carrier on the
>>> right side of the spectrum, which, usually are not a big problem, but when
>>> I try to decode DCIs using that part of the spectrum (ncce 5, 24, etc.)
>>>
>>> I tried a similar capture with bladeRF-cli and gnuradio (osmosdr
>>> interface): the former got the same problem, the latter did not. My guess,
>>> it is something related to how the bladerf is opened (I am thinking about
>>> how the signal is filtered), but I have no clue on how to test it.
>>>
>>> Is there any way to control the bladerf configuration from within
>>> pdsch_ue or usrp_capture_sync?
>>>
>>> Thanks a lot,
>>> Nicola Bui
>>>
>>> Research Engineer
>>> IMDEA Networks Institute
>>> Av. Mar del Mediterraneo, 22
>>> 28918 - Leganés (Madrid) - Spain
>>> mobile: +34 657 633 987
>>> phone: +34 91 481 6986
>>> fax: +34 481 6965
>>> _______________________________________________
>>> srslte-users mailing list
>>> srslte-users at lists.softwareradiosystems.com
>>> http://www.softwareradiosystems.com/mailman/listinfo/srslte-users
>>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.srsran.com/pipermail/srsran-users/attachments/20160323/2bf6bd86/attachment.htm>