[srslte-users] RSRP/SINR issues with pdsch_ue

Ismael Gomez ismael.gomez at softwareradiosystems.com
Wed May 10 17:26:07 UTC 2017


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 at 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
>>>
>>
>>
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