[srslte-users] RSRP/SINR issues with pdsch_ue

Sina Khanifar sina at rsrf.com
Wed May 10 17:41:31 UTC 2017


Thanks Ismael. I'll switch to a B200, and will also test in some differing
signal conditions to see if the RSRQ numbers stay within a +/- 2dB range.

On Wed, May 10, 2017 at 10:38 AM, Ismael Gomez <
ismael.gomez at softwareradiosystems.com> wrote:

> Ok there is no RSSI sensor on that board (or if there is, we don't use it)
> so you'll have to calibrate it manually for each band and bandwidth.
>
> Regarding the RSRQ I think the results you are obtaining are correct.
> Think that you are comparing two completely different RF frontends (the
> handset and the blade). The handset has been specifically designed for
> certain bands (RF filters, LNA, etc.) whereas the blade is a general
> purpose broadband frontend so you can expect +-2 dB signal quality when
> comparing them.
>
>
> On Wed, 10 May 2017 at 19:34 Sina Khanifar <sina at rsrf.com> wrote:
>
>> No, I'm using a Nuand bladeRF x40.
>>>>
>> On Wed, May 10, 2017 at 10:26 AM, Ismael Gomez <ismael.gomez@
>> softwareradiosystems.com> wrote:
>>
>>> Are you using B200/B210?
>>>
>>> On Wed, 10 May 2017 at 19:13 Sina Khanifar <sina at rsrf.com> wrote:
>>>
>>>> Hi Ismael,
>>>>
>>>> Thanks for the reply.
>>>>
>>>> > That's because the frequency response of the RF frontend is not flat
>>>> throughout all the frequencies. That's why we use the RSSI on-chip sensor
>>>> to compute the rf_gain_offset automatically. Have you tried that?
>>>>
>>>> The pdsch_ue script doesn't have the rf_gain_offset variable, but I
>>>> switched over to testing with cell_measurement.c where that variable is
>>>> included. Unfortunately I'm seeing similar results.
>>>>
>>>> Here is a summary of results using cell_measurement: https://www.
>>>> dropbox.com/s/xxejcc0pc5u0zl3/srslte-measurements.png?dl=0
>>>>
>>>> As you can see, the RSRP varies from the handset measured values. For
>>>> consistency all the handsets I am testing with are from the same vendor.
>>>>
>>>> > The way SINR is computed is vendor-specific so it's difficult to
>>>> compare across devices. You can try looking at RSRQ and compare that value.
>>>> RSRQ is a standarized equivalent metric of the SINR.
>>>>
>>>> If you look at the screenshot in the Dropbox link, I was actually
>>>> seeing a similar inconsistency with the RSRQ values.
>>>>
>>>> Thanks again for the help,
>>>>
>>>> Sina.
>>>>
>>>> On Wed, May 10, 2017 at 4:55 AM, Ismael Gomez <ismael.gomez@
>>>> softwareradiosystems.com> wrote:
>>>>
>>>>> Hi Sina,
>>>>>
>>>>> On Tue, 9 May 2017 at 21:38 Sina Khanifar <sina at rsrf.com> wrote:
>>>>>
>>>>>> Similar to the recent thread around issues with the cell_measurement
>>>>>> thread, I'm seeing problems with the pdsch_ue example script. I've tried
>>>>>> changing the RSRP and SINR calculations to make them better match real UE
>>>>>> measurements. For example, I am currently using:
>>>>>>
>>>>>>
>>>>> rsrp = 12*log10(rsrp/rf_gain_offset) where rf_gain_offset is set via
>>>>>> an arg to 2e9
>>>>>> sinr = 20*log10(sinr/noise/5)
>>>>>>
>>>>>> I've experimented with various values here, but continue to have
>>>>>> issues. In particular:
>>>>>>
>>>>>> * The RSRP gain offset appears to vary both with frequency and the
>>>>>> carrier signal's bandwidth. srs-lte shows higher rsrp at higher
>>>>>> frequencies, and higher rsrp at higher bandwidths.
>>>>>>
>>>>>
>>>>> That's because the frequency response of the RF frontend is not flat
>>>>> throughout all the frequencies. That's why we use the RSSI on-chip sensor
>>>>> to compute the rf_gain_offset automatically. Have you tried that?
>>>>>
>>>>>
>>>>>> * The SINR in the default code is never negative, whereas it is often
>>>>>> negative as measured by test UEs. It also generally doesn't match up to the
>>>>>> UE measurements, hence my 20*log10(sinr/noise/5) adjustment. This
>>>>>> alternative equation is still not very accurate, but at least generates
>>>>>> some negative values.
>>>>>>
>>>>>
>>>>> The way SINR is computed is vendor-specific so it's difficult to
>>>>> compare across devices. You can try looking at RSRQ and compare that value.
>>>>> RSRQ is a standarized equivalent metric of the SINR.
>>>>>
>>>>>
>>>>>>
>>>>>> Any thoughts on what might be causing these two issues?
>>>>>>
>>>>>> Thanks.
>>>>>>>>>>>> _______________________________________________
>>>>>> srslte-users mailing list
>>>>>> srslte-users at lists.softwareradiosystems.com
>>>>>> http://www.softwareradiosystems.com/mailman/listinfo/srslte-users
>>>>>>
>>>>>
>>>>>>>>
>>>
>>>>
>
ᐧ
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