OpenBSC

openbsc@lists.osmocom.org

6 participants
4274 discussions

Some initial investigation on GPRS support
by Harald Welte 26 Jun '09

26 Jun '09

Hi! I've started to analyze GPRS and was actually even starting to write some code for it, but then have given up for the time being - it's much more work than anticipated. Given the long todo list of OpenBSC right now, I think I'll have put aside GPRS for some time :( Based on looking at protocol traces, I have figured out the nanoBTS GPRS/EDGE implementation roughly looks as follows: * make sure we allow the BTS to activate the GPRS software components in abis_nm / OML activation! * BTS will use a UDP connection on port 23000 for the GPRS related frames. The GSM specs will consider this type of connection between the PCU (part of the nanoBTS) and the SGSN. The establishment/configuration of the UDP port number and SGSN ip address has not yet been identified. Probably similar to how the RSL link is activated via OML. The protocol stack looks like: IP : UDP : NSIP : BSSGP : LLC : higher-layer IP and UDP you should know and/or not care about ;) NSIP is a IP-enabled version of NS as specified in TS 08.16 BSSGP is specified in TS 08.18 LLC is as specified in TS 04.64 the higher-layer depends on the SAPI value of the LLC and can be * GMM (GPRS Mobility Management as specified in 04.08) * User Data (actual IP packets, e.g.) * SMS So what is weird about this is that the GPRS MM is actually part of 04.08, but it is not terminated at the BSC but rather at the SGSN. Also, the deep stack comprised of many headers is really weird. Furthermore, it seems that a lot of the packet scheduling and timeslot allocation is happening inside the nanoBTS - very unlike the GSM side of things. I have not yet managed to figure out how to allocate/dedicate resources to GPRS.. after all, the BTS needs to know how many timeslots it can use for it, etc. If anyone wants to dig deeper, you're most welcome to do so. A list of relevant specs: 01.61 GPRS cipher algorithm requirements 03.60 Overall GRPS logical architecture (above RL and MAC) 03.64 GPRS radio interface 04.60 RLC/MAC on PDCH 04.64 MS-SGSN LLC spec (on top of RLC/MAC) 04.65 SGSN SNDCP 08.14 BSS SGSN Gb Layer 1 08.16 BSS SGSN Gb Layer 2 08.18 BSS SGSN BSS GPRS protocol 09.95 Interworking between modified PLMN supporting legacy GPRS and GPRS mobiles 22.060 GPRS Service Spec 23.060 GPRS Radio Service Spec 29.016 SGSN - VLR Interface Gs network interface spec 29.018 SGSN - VLR Interface Gs layer3 interface spec 29.060 GPRS Tunneling (GTP) over Gn and Gp Happy hacking, -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

2 1

AW: AW: BS/MS power summary
by Andreas.Eversberg 26 Jun '09

26 Jun '09

hi, i tested the suggested values: > NM_ATT_BS11_RADIO_MEAS_GRAN, 0x01, 0x05, > NM_ATT_BS11_RADIO_MEAS_REP, 0x01, 0x01, no measurement reports during calls, never seen one before. maybe i have the wrong firmware load? i also get errors after starting bsc-hack on the lmt. i will try to load a different firmware this weekend. regards, andreas

1 0

Re: AW: BS/MS power summary
by Dieter Spaar 25 Jun '09

25 Jun '09

Hello Andreas, On Thu, 25 Jun 2009 11:16:58 +0200, "Andreas.Eversberg" <Andreas.Eversberg(a)versatel.de> wrote: > > thanx for the detailed description. i will try this out this weekend. i > will use a 900mhz radio receiver to check out the change in signal > strength. i cannot get any measurement reports yet. the change of > NM_ATT_BS11_RADIO_MEAS_GRAN value did not get me any measurement report > as before. Strange that you don't see the measurement reports. Here are the two attributes I use for the TRX attributes and they result in lots of reports when a channel is active (at least for a speech channel, for a location update there might be only one report because the connection is not active that long): NM_ATT_BS11_RADIO_MEAS_GRAN, 0x01, 0x05, NM_ATT_BS11_RADIO_MEAS_REP, 0x01, 0x01, I think I also tried it already with 0x02 to get a report every second. Best regards, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de

1 0

AW: BS/MS power summary
by Andreas.Eversberg 25 Jun '09

25 Jun '09

dieter, thanx for the detailed description. i will try this out this weekend. i will use a 900mhz radio receiver to check out the change in signal strength. i cannot get any measurement reports yet. the change of NM_ATT_BS11_RADIO_MEAS_GRAN value did not get me any measurement report as before. regards, andreas

1 0

OpenBSC with 2.5G or 3G mobile devices support?
by Nordin 25 Jun '09

25 Jun '09

Hello guys, Has anybody registered a PDA phone of 2.5G/3G type to the BS11 bts succesfully? Cause I'm still struggling with it for my nanoBTS (1800 Mhz). Thank you.

7 18

Which Pico cells are supported
by Waqas Farooq 24 Jun '09

24 Jun '09

Hi All, Can somebody please let me know which Pico cells can be interfaced with Open BSC? Any help or pointers will be be much appreciated. Thanks,

2 3

Setting BS11 output power
by Eric Cathelinaud 24 Jun '09

24 Jun '09

Hi, I was following your mails about your results for the ouput power but I don't understand how you change it. I was checking the code but I didn't find how to change TX0 output power. I tried to change the line : abis_nm_bs11_set_trx_power(&bts->trx[0], BS11_TRX_POWER_GSM_30mW); with abis_nm_bs11_set_trx_power(&bts->trx[0], BS11_TRX_POWER_GSM_250mW); in the "create_objects" fonction but I don't know how the fonction is loaded, I don't know how the bs11 enter the state "BS11_STATE_WAIT_MIN_CFG_2" case BS11_STATE_WAIT_MIN_CFG_2: bs11cfg_state = STATE_SWLOAD; rc = create_objects(g_bts); break; If anyone can help me Thanks a lot Eric Cathelinaud

2 2

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

1 0

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

2 1

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

24 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

2 1

Jump to page:

2026

2025

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

OpenBSC