Thanks Nick for your answer. Well, so I am working with OpenBTS and I understand that it sets parameters such as the LNA gain at the Rx chain of the USRP B210. So in my research I got to think that I should know How my RECEIVER works in terms of noise floor it detects at a certaing LNA gain, so I can set the minimum uplink RSSI target value on OpenBTS to ensure that the mobile stations (MS) will reach the Base Station at a maximum radiolink distance as possible. For example:
Lets say that with a LNA gain = 40 dB, a 500kHz GSM channel bandwidth (270kHz ch carrier +200kHz ch spacing) has a noise floor of around -85 dB wrt A/D full scale. Then I will have to set the uplink RSSI target on OpenBTS around -75 dB (10dB over noise floor) wrt A/D full scale. This will set a maximum radiolink distance when MS transmits at maximum power. Then, if there is a LNA gain that will produce lower the noise floor, it will allow to set a lower RSSI and that will lead to allow more path loss, which can be translated into a greater radiolink distance? Also I noticed on an simple flowgraph on gnuradio (UHD-Source - QT Gui Freq Sink) that with lower USRP LNA Gain a very sharp signal on the center frequency appears. I understand that this is the DC Offset. I don't know but I assume that OpenBTS has a method to eliminate/filter that DC Offset but I noticed that when increasing the LNA Gain the noise floor increments and at some point DC spike was surpassed by the noise floor. So I Guess that the chosen LNA Gain should do some of this too. What do you think? Thanks On Sun, Jun 3, 2018 at 4:14 AM, Nick Foster <bistrom...@gmail.com> wrote: > Oscar, that document covers a *lot* of testing using quite a lot of > expensive calibrated instrumentation. Maybe you could elaborate a bit on > what exactly you want to test, and why? > > On Sun, Jun 3, 2018 at 9:49 AM oscar llerena via USRP-users < > usrp-users@lists.ettus.com> wrote: > >> Thanks Nick and Neel for the help. >> >> So, do you have any suggestion how I can obtain the following curves: >> https://kb.ettus.com/images/c/cb/B200_RF_Performance.pdf >> with for example GNURadio flowgraph? >> >> Thanks >> >> On Tue, May 22, 2018 at 3:33 PM, Nick Foster <bistrom...@gmail.com> >> wrote: >> >>> Neither. It will depend on the gain setting and individual variation in >>> the device. It is not calibrated to any specific dBm value and if you >>> require dBm you must calibrate your readings against a known source. The >>> listed maximum power figure is a maximum to avoid damage to the device. >>> >>> Nick >>> >>> On Mon, May 21, 2018 at 10:35 AM oscar llerena via USRP-users < >>> usrp-users@lists.ettus.com> wrote: >>> >>>> Hi everyone >>>> >>>> On the following OpenBTS parameter: >>>> >>>> OpenBTS> devconfig GSM.Radio.RSSITarget >>>> GSM.Radio.RSSITarget -50 [default] >>>> - description: Target uplink RSSI (Received Signal Strength >>>> Indication) for MS power control loop, in dB wrt to A/D full scale. >>>> >>>> The description indicates that the RSSI value is minus 50 dB with >>>> respect to the A/D full scale. Now, according to Ettus on link [1] the >>>> USRP B210 has a maximum input power of 0 dBm, although other sources [2] >>>> state that maximum input power is -15dBm. In this case, which dBm power >>>> level will mean the term "with respect to A/D full scale". >>>> >>>> Thanks >>>> >>>> [1] https://kb.ettus.com/B200/B210/B200mini/B205mini >>>> [2] https://files.ettus.com/manual/page_usrp_b200.html >>>> >>>> >>>> -- >>>> Oscar Llerena >>>> Tlf: 997575596 >>>> _______________________________________________ >>>> USRP-users mailing list >>>> USRP-users@lists.ettus.com >>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>>> >>> >> >> >> -- >> Oscar Llerena >> Tlf: 997575596 >> _______________________________________________ >> USRP-users mailing list >> USRP-users@lists.ettus.com >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> > -- Oscar Llerena Tlf: 997575596
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