Hi Folks.
I have a simple and straight forward question:
in the openbsc.cfg i find a parameter "ms max power" which is set to 15 dBm (apporox 30mW) by default.
http://openbsc.osmocom.org/trac/wiki/osmo-nitb_VTY says the following: "maximum transmit power (in dBm) to be used by MS in this BTS. This is used in the System Information on the BCCH as well as for the MS power level at the time a dedicated channel is activated."
My question is how low may i set ms max power level? Is 15dBm already the lowest possible minimum or can i set it down to 1dBm if i like?
regards Philipp
Hi,
On Tue, Apr 09, 2013 at 10:57:38PM +0200, dexter wrote:
in the openbsc.cfg i find a parameter "ms max power" which is set to 15 dBm (apporox 30mW) by default.
http://openbsc.osmocom.org/trac/wiki/osmo-nitb_VTY says the following: "maximum transmit power (in dBm) to be used by MS in this BTS. This is used in the System Information on the BCCH as well as for the MS power level at the time a dedicated channel is activated."
My question is how low may i set ms max power level? Is 15dBm already the lowest possible minimum or can i set it down to 1dBm if i like?
I'd say it's 0..40.
Kind regards, -Alexander Huemer
[?] http://openbsc.osmocom.org/trac/wiki/osmo-nitb_VTY#msmaxpower0-40 [?] http://cgit.osmocom.org/openbsc/tree/openbsc/src/libbsc/bsc_vty.c#n1934
On Tue, Apr 09, 2013 at 10:57:38PM +0200, dexter wrote:
in the openbsc.cfg i find a parameter "ms max power" which is set to 15 dBm (apporox 30mW) by default.
http://openbsc.osmocom.org/trac/wiki/osmo-nitb_VTY says the following: "maximum transmit power (in dBm) to be used by MS in this BTS. This is used in the System Information on the BCCH as well as for the MS power level at the time a dedicated channel is activated."
My question is how low may i set ms max power level? Is 15dBm already the lowest possible minimum or can i set it down to 1dBm if i like?
I just looked it up. GSM 05.05 speaks of values 0..39dBm, although the underlying thing is the 'Power control level', MS_TXPWR_MAX_CCH, which has a range of 0..31. This is also mentioned in GSM 05.08. I also found [1].
Kind regards, -Alexander Huemer
[1] http://gsm-optimization.blogspot.com/2012/04/mstxpwrmaxcch.html
dexter wrote:
My question is how low may i set ms max power level? Is 15dBm already the lowest possible minimum or can i set it down to 1dBm if i like?
hi,
set ms max power to 0 to get 1 milliwatts to start with (rach and initial power). set it to 30 to get 1 watts (1800) or 33 to get 2 watts (900). during dedicated channel, it is up to the bts to change the power level up or down, depending on the uplink level/quality.
regards,
andreas
Hello Andreas,
Does this setting has linear dependence? Or is there something like a calibration table for max_power_red value?
Thanks, Sergey.
On Apr 11, 2013, at 12:20 AM, Andreas Eversberg wrote:
dexter wrote:
My question is how low may i set ms max power level? Is 15dBm already the lowest possible minimum or can i set it down to 1dBm if i like?
hi,
set ms max power to 0 to get 1 milliwatts to start with (rach and initial power). set it to 30 to get 1 watts (1800) or 33 to get 2 watts (900). during dedicated channel, it is up to the bts to change the power level up or down, depending on the uplink level/quality.
regards,
andreas
Hi Sergey
Does this setting has linear dependence? Or is there something like a calibration table for max_power_red value?
I think i can answer this (please correct my if i am wrong). To my understanding "nominal power" is the maximum power the BTS is capable to transmit. In the case of the nanoBTS it is 23dBm which is about 200mW. So the "nominal power" is the calibration value you asked for.
The "max_power_red" value is the setting for the actual output power. In my case it has been set to 20dBm. This should result in an output power of 23dBm-20dBm=3dBm=ca. 2mW. This is the default setting. I do not know if it is the lowest possible setting. I transmit into a dummyload anyway which results into a cell radius of approx 1m.
The dBm scale is not linear, just look it up yourself It's easy ;-)
regards. Philipp
Dear Sergey,
On Thu, Apr 11, 2013 at 01:13:39AM +0400, Sergey V. Efimov wrote:
Does this setting has linear dependence? Or is there something like a calibration table for max_power_red value?
dB values are never linear, they're logarithmic. dBm is vs. Power.
The value is the absolute tranmission power of the MS (uplink) in dBm. It has nothing to do with max_power_red, whcih is about the relative reduction of downlink transmit power respective to the nominal transmit power of the BTS in downlink.
The values are all specified in the relevant GSM specs.
Hello Andreas,
set ms max power to 0 to get 1 milliwatts to start with (rach and initial power). set it to 30 to get 1 watts (1800) or 33 to get 2 watts (900). during dedicated channel, it is up to the bts to change the power level up or down, depending on the uplink level/quality.
Thank you very much for your hint. I have set it to 0 dBm now and it works fine. I have my phones directly next to the BTS so i think it will not raise the power above 1 or 2 mW.
regards. Philipp
-
Alexander Huemer -
Andreas Eversberg -
dexter -
Harald Welte -
Sergey V. Efimov