[srslte-users] RSRP/SINR issues with pdsch_ue

Sina Khanifar sina at rsrf.com
Wed May 10 17:13:25 UTC 2017


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
>>
>
ᐧ
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