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Harald Welte laforge at gnumonks.orgOn Fri, Jun 19, 2009 at 07:21:05PM +0200, Dieter Spaar wrote:
>
> And here are the measurment results for the BS-11 for each of the
> four power classes:
thanks so much.
I have extended the table by the theoretical value (i.e. nominal power
converted to dBm minus (NM_ATT_RF_MAXPOWR_R * 2dB steps-size)):
> BS-11, ARFCN 123
>
> BTS Power: 0.03 Watt
> NM_ATT_RF_MAXPOWR_R RF output Theoretical
>
> 0 12 dBm 15 dBm
> 1 9.7 dBm 13 dBm
> 2 7.8 dBm 12 dBm
> 4 4.7 dBm 7 dBm
> 6 0.9 dBm 3 dBm
>
> BTS Power: 0.08 Watt
> NM_ATT_RF_MAXPOWR_R RF output
>
> 0 17 dBm 19 dBm
> 1 15 dBm 17 dBm
> 2 13 dBm 15 dBm
> 4 8.7 dBm 11 dBm
> 6 5.5 dBm 7 dBm
>
> BTS Power: 0.25 Watt
> NM_ATT_RF_MAXPOWR_R RF output
>
> 0 22 dBm 24 dBm
> 1 20 dBm 22 dBm
> 2 18 dBm 20 dBm
> 4 14 dBm 16 dBm
> 6 9.9 dBm 12 dBm
>
> BTS Power: 2 Watt
> NM_ATT_RF_MAXPOWR_R RF output
>
> 0 32 dBm 33 dBm
> 1 30 dBm 31 dBm
> 2 27 dBm 29 dBm
> 4 23 dBm 25 dBm
> 6 19 dBm 21 dBm
>
> Values larger than 6 for NM_ATT_RF_MAXPOWR_R are not supported.
Do you get an error message (SET ATTRIBUTE NACK) if you try to set it?
According to the spec, 6 steps of 2dB is the minimum a BTS has to support.
The indication in 12.21 that NM_ATT_RF_MAXPOWR_R is read-only is thus
likely only an error in the documentation.
> There is most certainly an error in the range of 2 to 3 dB coming
> from the low-quality cable and some adaptor connectors to connect
> the BTS to the measurement equipment.
sure. Also, the BTS is 12 years old...
> I did also play with the power control of the BS-11. As far as I
> am aware the BTS power control is not enbabled per default in
> bsc_hack, the measurement results from the BTS confirm that. If
> I enable the BTS power control I can at least see that the BTS
> changes the MS power. I have not verified on the phone if the
> power is really changed, but the RX level of the BTS seem to
> indicate that it works.
BTS power control should be 'BS power control', i.e. the dynamic
adjustment of downlink power. The respective details are quite
vendor specific, as it is an optional feature (and one that is not
to be used on C0 anyway).
MS power control (the dynamic adjustment of MS power) should be used even now,
otherwise I would not understand my observation of the phone bursts becoming
much lesss loud in the speakers after the initial few very loud bursts.
> There are a lot of parameters to play with so if anyone is
> interested, just reduce NM_ATT_BS11_RADIO_MEAS_GRAN (lets
> say to 2) so that you see frequent measurement results and
> watch what is going on.
Yes, thanks.
What would be more interesting to me than dynamic BS power control is:
How do the 'BS POWER' IE's in the ACTIVATE CHANNEL and 'BS POWER CONTROL'
messages affect the BS transmit power.
Some things to confirm:
1) whatever we use as BS POWER value in ACTIVATE CHANNEL on a TCH/SDCCH8
on the C0 does not make any changes to the acutal TX power
2) if we activate a channel on the second TRX, do we see the BTS power
adjusted according to BS POWER in ACTIVATE CHANNEL ?
3) if we use a BS POWER CONTROL message on the CCCH on C0 of an otherwise idle
BTS, do we see a power change on the TRX ?
I've just written some code for OpenBSC to implement those commands, I'll
commit it later.
--
- Harald Welte <laforge at gnumonks.org> http://laforge.gnumonks.org/
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