OpenBSC

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4317 discussions

BS/MS power summary
by Dieter Spaar 24 Jun '09

24 Jun '09

Hello, I try to give a short summary of the MS and BS power settings. It is not intended to replace the GSM specs, it just contains the important things for the current BS-11 configuration. MS power: - The MS power is usually specified as an absolute value, a lower value means higher power. Some values for GSM 900 (GSM 1800 has a different encoding): 15 -> 13 dBm (0.02 W) 10 -> 23 dBm (0.2 W) 5 -> 33 dBm (2 W) - The power used to access the RACH before any channel is active, is defined by a Cell Selection parameter in SYSTEM INFORMATION TYPE 3 and 4. Remark: bsc_hack currently uses "2" which should be increased (lower power) to avoid interference with the public networks. - When the BTS activates a channel, it sets the MS power. bsc_hack currently sets it to 15 which should be OK for testing (see rsl_rx_chan_rqd() in abis_rsl.c). - Dynamic power control of the MS power by the BTS is currently not enabled. BS power: - For the BS-11 the PA power can be configured to 0.03W, 0.08W, 0.25W or 2W (b11_config can be used for this purpose). - The attribute NM_ATT_RF_MAXPOWR_R of each TRX of the BS-11 can be set to a value from 0 (0dB) to 6 (12dB) to reduce the power in steps of 2dB (see bsc_hack.c). - for the TRX which carries the BCCH, there is no dynamic BS power control possible. In the meantime I have read at several places that the BCCH TRX has to use a fixed power and additionally cannot use a different ARFCN for example for the TCH (which also means that no hopping is possible). To use hopping or dynamic BS power control, the second TRX has to be used and configured in a way that it does not carry a BCCH. Best regard, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de

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AW: location update problem
by Andreas.Eversberg 24 Jun '09

24 Jun '09

harald, i checked the msg_4 array. i found the power info in the description, but i cannot see where the values are in the array. also i don't really know the maximum power value for BS11 (GSM 900). is 0db maximum? is it relative to the BS power class? > Check > * the 'MS POWER' attribute in the ACTIVATE CHANNEL > * the cell selection parameters in SYSTEM INFORMATION TYPE 4 (max tx power for CCH) anyway, i found the bug about holding the location update process. i fixed it, but before i supply a patch, i will check if this really works when the link fails during location update again. regards, andreas

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AW: location update problem
by Andreas.Eversberg 23 Jun '09

23 Jun '09

hi, how can i advice the phone to use the "full" power level according to the power class of the bs11? what parameter and what value is required? currently we have "kieler woche", an event with up to 3.000.000 visitors over one week. for the "mobile base station" i use a standard PC with E1/S0 card, a BS11, a laptop, an ISDN phone, and an UPS with 4 * 200Ah batteries. andreas -----Ursprüngliche Nachricht----- Von: Dieter Spaar [mailto:spaar@mirider.augusta.de] Gesendet: Dienstag, 23. Juni 2009 10:36 An: Andreas.Eversberg Cc: openbsc(a)lists.gnumonks.org Betreff: Re: location update problem Hello Andreas, On Mon, 22 Jun 2009 19:40:17 +0200, "Andreas.Eversberg" <Andreas.Eversberg(a)versatel.de> wrote: > > after location update fails. "DB: Failed to find the Subscriber...", get > an "ERROR INDICATION" with cause 1. it seems that the mobile just stops > sending on the channel. the channel ressource hold by location update > process is not freed. the last messages show that. > > i will look on this the next days and report if i found something. if > you have any idea, please tell me. the way to test any change/fix is > quite complicated. the bug only occurrs when many phones are available > and when they move from a different network to my network (built in a > car, moving arround.) Just a wild guess: Could it be a reception problem ? If you have set the BS-11 to a high power level, many phones will see it. Currently the BS-11 advises the phones to use a very low power level when activating a channel. So the BS-11 might receive the phone with a low signal strength and the receiption is just too bad (although the phones will receive the BS-11 quite well). The measurement reports should indicate if this is the problem. Out of interest, do you also have a PC with an E1 card in the car or do you use a laptop with an USB (or PCMIA) to E1 interface ? Best regards, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de

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Re: AW: location update problem
by Dieter Spaar 23 Jun '09

23 Jun '09

Hallo Kai, On Tue, 23 Jun 2009 14:19:20 +0200, "=?ISO-8859-15?Q?Kai_M=FCnz?=" <squ(a)tent.at> wrote: > > There is an even lighter setup possible. > > I'm using an old IBM Thinkpad R50p with a Thinkpad DockII (Ebay, 30Eur) > > http://www.bildschirmtext.org/thinkpad-e1.jpg > > Just connect the BTS and play %) Nice, and it even has DECT connnectivity (looks like a COM-ON-AIR card in the background :-) Best regards, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de

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Re: AW: AW: location update problem
by Dieter Spaar 23 Jun '09

23 Jun '09

Hello Andreas, On Tue, 23 Jun 2009 13:30:17 +0200, "Andreas.Eversberg" <Andreas.Eversberg(a)versatel.de> wrote: > > picture! Even more cool :-). I expected a bigger car, maybe a van, to but all the stuff inside. Really nice GSM war-driving setup ;-) Best regards, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de

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Re: AW: location update problem
by Dieter Spaar 23 Jun '09

23 Jun '09

Hello Andreas, On Tue, 23 Jun 2009 10:12:38 +0200, "Andreas.Eversberg" <Andreas.Eversberg(a)versatel.de> wrote: > > how can i advice the phone to use the "full" power level according to > the power class of the bs11? what parameter and what value is required? Currently the BS power is set in rsl_rx_chan_rqd() (file abis_rsl.c), its the "lchan->ms_power" assignment. Currently the value 0x0F (13 dBm) is used (I am not sure if this is still true for the latest version of OpenBSC). If you set this value to 0, the MS will use the maximum power (usually only 5 is supported for GSM900, 2 Watt). I did only a few tests, but I could see that my phone uses the modified value. You can of course also look at the measurement report and check the used values. > currently we have "kieler woche", an event with up to 3.000.000 visitors > over one week. > > for the "mobile base station" i use a standard PC with E1/S0 card, a > BS11, a laptop, an ISDN phone, and an UPS with 4 * 200Ah batteries. Cool, do you have some pictures of the setup ? :-) Best regards, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de

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AW: AW: location update problem
by Andreas.Eversberg 23 Jun '09

23 Jun '09

picture! > Cool, do you have some pictures of the setup ? :-)

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Re: location update problem
by Dieter Spaar 23 Jun '09

23 Jun '09

Hello Andreas, On Mon, 22 Jun 2009 19:40:17 +0200, "Andreas.Eversberg" <Andreas.Eversberg(a)versatel.de> wrote: > > after location update fails. "DB: Failed to find the Subscriber...", get > an "ERROR INDICATION" with cause 1. it seems that the mobile just stops > sending on the channel. the channel ressource hold by location update > process is not freed. the last messages show that. > > i will look on this the next days and report if i found something. if > you have any idea, please tell me. the way to test any change/fix is > quite complicated. the bug only occurrs when many phones are available > and when they move from a different network to my network (built in a > car, moving arround.) Just a wild guess: Could it be a reception problem ? If you have set the BS-11 to a high power level, many phones will see it. Currently the BS-11 advises the phones to use a very low power level when activating a channel. So the BS-11 might receive the phone with a low signal strength and the receiption is just too bad (although the phones will receive the BS-11 quite well). The measurement reports should indicate if this is the problem. Out of interest, do you also have a PC with an E1 card in the car or do you use a laptop with an USB (or PCMIA) to E1 interface ? Best regards, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de

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location update problem
by Andreas.Eversberg 22 Jun '09

22 Jun '09

hi, i got a leak of channel ressource. (currently i cannot look at the source code.) ignore the first 3 lines, they are just part of testing/debugging code i use. after location update fails. "DB: Failed to find the Subscriber...", get an "ERROR INDICATION" with cause 1. it seems that the mobile just stops sending on the channel. the channel ressource hold by location update process is not freed. the last messages show that. i will look on this the next days and report if i found something. if you have any idea, please tell me. the way to test any change/fix is quite complicated. the bug only occurrs when many phones are available and when they move from a different network to my network (built in a car, moving arround.) andreas <8000> chan_alloc.c:164 looking for free signalling subchannel on CCCH <8000> chan_alloc.c:168 requesting SDCCH* channel <8000> chan_alloc.c:135 free lchan (1) found on trx 0 ts 1 <0010> abis_rsl.c:894 Activating ARFCN(123) TS(1) SS(1) lctype SDCCH chan_nr=0x49 r=LOCATION_UPDATE ra=0x15 <0010> abis_rsl.c:744 channel=(bts=0,trx=0,ts=1) chan_nr=0x49 CHANNEL ACTIVATE ACK <0001> abis_rsl.c:988 channel=(bts=0,trx=0,ts=1) chan_nr=0x49 ESTABLISH INDICATION <0004> gsm_04_08.c:1528 LOCATION UPDATING REQUEST <0004> gsm_04_08.c:1200 LUPDREQ: mi_type=0x04 MI(1293316309) type=NORMAL <0002> gsm_04_08.c:347 lchan (bts=0,trx=0,ts=1,ch=1) increases usage to: 1 <0004> gsm_04_08.c:1226 <0002> gsm_04_08.c:990 (bts 0 trx 0 ts 1 pd 05) Sending 0x18 to MS. DB: Failed to find the Subscriber. '1' '1293316309' <0002> gsm_04_08.c:990 (bts 0 trx 0 ts 1 pd 05) Sending 0x18 to MS. <0008> gsm_04_08.c:1250 <- Can't find any subscriber for this ID <0001> abis_rsl.c:988 channel=(bts=0,trx=0,ts=1) chan_nr=0x49 DATA INDICATION <0008> gsm_04_08.c:1634 CLASSMARK CHANGE CM2(len=3) CM3(len=4) <0001> abis_rsl.c:988 channel=(bts=0,trx=0,ts=1) chan_nr=0x49 ERROR INDICATION cause=0x01 <0001> chan_alloc.c:256 Recycling the channel with: 0 (0) <0010> abis_rsl.c:530 Channel Release CMD channel=(bts=0,trx=0,ts=1) chan_nr=0x41 <0010> abis_rsl.c:744 channel=(bts=0,trx=0,ts=1) chan_nr=0x41 RF CHANNEL RELEASE ACK <8000> chan_alloc.c:203 freeing logical channel on trx 0, ts 1 <0010> abis_rsl.c:744 channel=(bts=0,trx=0,ts=1) chan_nr=0x49 CONNECTION FAIL: CAUSE: 18 01 49 Cause 0x18 IGNORING, lchan in use! (1 times) <0010> abis_rsl.c:744 channel=(bts=0,trx=0,ts=1) chan_nr=0x49 CONNECTION FAIL: CAUSE: 18 01 49 Cause 0x18 IGNORING, lchan in use! (1 times) <0010> abis_rsl.c:744 channel=(bts=0,trx=0,ts=1) chan_nr=0x49 CONNECTION FAIL: CAUSE: 18 01 49 Cause 0x18 IGNORING, lchan in use! (1 times) <0010> abis_rsl.c:744 channel=(bts=0,trx=0,ts=1) chan_nr=0x49 CONNECTION FAIL: CAUSE: 18 01 49 Cause 0x18 IGNORING, lchan in use! (1 times)

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Trying to understanding the source
by Nordin 22 Jun '09

22 Jun '09

Hello guys, I was studying the sourcecode of OpenBSC to get a good understanding of how things work. But due to my lack of experience in Linux programming I have some difficulties to understand the source. I understand that the way bsc_hack works is based on event-queue concept, am I right? Anyway, in select.c I don't understand what's going on when it comes to registering and unregistering fd's in combination with linuxlist.c. Can someone please give me some links where such concepts are being explained, so I can study it? Thanks in advance.

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