[srslte-users] Ouput power USRP-2901

Fri Apr 9 15:31:00 UTC 2021

Hello Neel Pandeya,

Thank you for your answer. If we can have an output power of +10dBm as indicated, it will be more than expected in our case.

We measured the output power with a spectrum analyzer. By adding amplifier and pre-amplifier, we can increase the output power by 50dBm but that is not normal that we can only achieve -60dBm with the USRP alone. Also we would like to not use additional equipment.

Please find attached the results on the spectrum analyzer. In yellow the output power with a USRP alone and in blue with amplifiers added.

We are using UHD 3.15. Do you think there could be bad behaviors by using this version instead of the 3.9?

Thank you,

Simon

________________________________
De : Neel Pandeya <neel.pandeya at ettus.com>
Envoyé : vendredi 9 avril 2021 15:00:09
À : Francisco Paisana
Cc : Taillefer Simon; srslte-users at lists.softwareradiosystems.com
Objet : Re: [srslte-users] Ouput power USRP-2901

Hello Taillefer Simon:

The maximum output power for the USRP B200/B210 is approximately between +10 and +18 dBm, depending on frequency and gain setting.

How exactly are you measuring the output power of your USRP B210?

Which version of UHD are you using?

https://kb.ettus.com/B200/B210/B200mini/B205mini

--Neel Pandeya

On Fri, 9 Apr 2021 at 07:21, Francisco Paisana <francisco.paisana at softwareradiosystems.com<mailto:francisco.paisana at softwareradiosystems.com>> wrote:
Hey,

Regarding the MCS, I believe you can either set a maximum MCS or a fixed MCS in the enb.conf. See the parameters "pdsch_mcs", "pdsch_max_mcs", "pusch_mcs", "pusch_max_mcs".

For the bandwidth, I don't think that changing a UE's DL grant bandwidth will affect the maximum DL tx power. For the UL, our eNB will only support UL power control and PHR handling in the upcoming release, so changing the bandwidth will not have a noticeable impact, I believe.

With regard to the USRP tx power, maybe some other users on the mailing list can help.

Kind Regards,
Francisco

On Fri, Apr 9, 2021 at 11:35 AM Taillefer Simon <simon.taillefer at telespazio.com<mailto:simon.taillefer at telespazio.com>> wrote:

Hello srsLTE team,

We are encountering an issue regarding the ouput power of the SDRs we are using between the ENB and the UE.

We are using 2 laptops with 2 USRP-2901 from National Instrument on what we flash the firmware of the USRP B210 when running srsENB and srsUE using UHD.

The maximum output power from the NI documentations is +15dBm but in our case, the maximum output power we can achieve is around -60dBm that allow us to have around 10 meters of range between the two USRPs. In the conf files. the TX and RX gains are already at the maximum value (respectively 89 and 40 dB).

So do you know how we can manage to have more output power from our USRPs? Is there a limit in the code of file conf that does not allow the USRPs to work at their maximum output power? Our goal is to achieve at least -30dBm.

Also, how can we set the modulation to only BPSK or QPSK instead of QAM? We saw that it is maybe possible to fix the MCS index? And can we decrease the bandwidth to maybe have more power?

Thank you for your help,

Simon Taillefer

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