[srslte-users] TX Power and Signal Power received at UE

[Francisco Paisana]

Hey Rúben,

I don't think this is a srsLTE issue. Have you asked about this in the
BladeRF and USRP mailing lists?

Kind Regards,
Francisco


On Tue, Jun 23, 2020 at 1:38 PM Rúben Queirós <up201504489 at fe.up.pt> wrote:

> Good afternoon,
>
> After some testing done with VNA's to figure it out if the problem was
> the antennas or something else related to the configuration, i realised
> both the antennas and the SDR frontend had some issues that could be
> fixed.
>
> First of all, the antenna wasn't completely adapted to the frequencies
> used. That was fixed with the replacement of the antennas that were
> tested and showed a return loss of less than -10dB.
>
> However, the SDR had also an issue. I was expecting that the SDRs would
> transmit atleast at 0dBm, and when i measured the TX Power that came out
> from the SDR when using srsENB i read on the VNA an average number of
> -40dBm which is quite lower than what it was advertised.
>
> Is there any configuration in enb.conf or any similar file that could be
> limiting the TX gain or TX power that is coming out of the SDR? Im using
> the max gain possible.
>
> Sorry for the spam, but i didn't get an answer last time!
> Rúben Queirós
>
> Em 26.05.2020 16:55, Rúben Queirós escreveu:
> > Good Afternoon,
> >
> > First of all thank you for developing srsLTE. I'm currently
> > researching to my MSc degree and i'm using srsLTE to evaluate the
> > performance of different SDR hardwares namely, BladeRFx40, BladeRF
> > micro 2.0 and USRP B210 The antennas used are TriBand from Nuand. For
> > the UE i'm using a commercial Samsung J7 that connects sucessfully to
> > the srseNB and srsEPC.
> >
> > I've been using the software for a couple months already and i'm
> > running out of options so i'm writing you this e-mail hoping that you
> > can help me with my problem.
> >
> > Im transmitting in Band 3, 7 and 20, Central frequencies, switching
> > between NRBs ( from 15 up to 50 sucessfully ) and according to some
> > LTE Throughput Calculators, the results are way lower than the
> > expected at Low range ( 1 Meter between the eNB station and UE ).
> > After logging the Signal Power Received at the UE, i realised the
> > signal power is way weaker than it should be.
> >
> > Assuming the information in
> > https://www.pasternack.com/t-calculator-friis.aspx is correct, and
> > considering no antenna gains in RX or TX, i should be expecting
> >
> >
> > Tx Power   1m ( range)          2600 MHz       1800 MHz        800 MHz
> > 8dBm     Blade Micro  -32,75 dBm      -29,55 dBm      -22,51 dBm
> > 6dBm     Blade x40    -34,75 dBm      -31,55 dBm      -24,51 dBm
> > 10dBm    USRP B210    -30,75 dBm      -27,55 dBm      -20,51 dBm
> >
> > However the values im getting are between -70 to -95 dBm. This tests
> > were done with LOS between the eNB and the UE and i've noticed the
> > software always sets the TX Gain of the RF hardware to the max, yet it
> > is still a weak signal.
> > I will attach an example of an enb.conf used in one of this tests. If
> > it is not enough to detect the problem, i also attach the other logs i
> > capture for the same test performed.
> >
> > Thank you in advance!
> > Ruben Queirós
>
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