Cellular Network Infrastructure » Radio Access Network » OsmoBSC

osmo-bts.git loops.c ms_power_diff() currently contains:

// FIXME: to go above 1W, we need to know classmark of MS

* pespin trying to find out whether we already retrieve/calculate MS power class in some place
<fixeria> pespin: AFAIR, MS Power Class is a part of the Mobile Station Classmark 1
<fixeria> pespin: so the MSC should know it
<pespin> fixeria, yeah just found it has a "RF power capability"  field in it
<pespin> fixeria, in which message is that IE send? I was expecting to gather it in BTS
<pespin> in order to know the maximum power level we can ask the MS to use in loops.c ms_power_diff()
<fixeria> pespin: it is a part of Location Updating Request and CM Service Request messages
<fixeria> pespin: most likely, a part of Paging Response too
<pespin> ok many thanks
<pespin> fixeria, maybe it should actually be parsed by BSC and taken into account when sending Chan ACT
<fixeria> huh, now it's also interesting to me how to know the MS Power Class from the BTS
<pespin> well if the BSC takes it into account in MS Power Level during CHAN ACT then the BTS doesn't need to know about it
<pespin> it simply applies that power level as maximum
<fixeria> pespin: as far as I can see, the BSC already does parsing of some messages
<fixeria> there is handle_classmark_chg()
<pespin> yeah, looks like that's the intended way
<pespin> I'll check if there's a ticket to implement that and otherwise I'll create it
<fixeria> pespin: the question is how to inform the BTS about the MS Power Class? is there any A-Bis IE for that?
<pespin> fixeria, during CHAN ACT and during MS Power Control messages
<pespin> the MS Power IE contains the maximum power level allowed on that chan
<pespin> it is so far calculated based on "ms max power" param from VTY
<pespin> but we can take into account the rf power capability from classmark1 there too so restrict more the maximum power level
<fixeria> ok, so the MS Power IE coming from the BSC would contain the restricted power level (according to the band and MS Power Class), right?
<pespin> that's my guess indeed
<fixeria> makes sense
<fixeria> pespin: FYI: https://git.osmocom.org/osmo-bsc/tree/src/osmo-bsc/gsm_04_08_rr.c#n922

• TS 05.05 sec 4.1.1 "Mobile station" contains MS Power class and MS Power level <-> dBm tables: https://www.etsi.org/deliver/etsi_gts/05/0505/05.01.00_60/gsmts_0505v050100p.pdf
• TS 24.008 sec 10.5.1.5 "Mobile Station Classmark 1" is the IE containing "RF Power capability": https://www.etsi.org/deliver/etsi_ts/124000_124099/124008/13.07.00_60/ts_124008v130700p.pdf
• classmark1 is implemented in libosmocore/include/osmocom/gsm/protocol/gsm_04_08.h, "struct gsm48_classmark1", the interesting field is named "uint8_t pwr_lev:3"
  osmo-bsc.git contains "struct gsm_classmark" which in turn contains "struct gsm_classmark1", and it is already used in some places.
• https://www.electronics-notes.com/articles/connectivity/2g-gsm/power-amplifier-control-classes.php