OpenBSC November 2020

openbsc@lists.osmocom.org

13 participants
18 discussions

Understanding GSM BTS Tx power levels
by Mychaela Falconia 20 Nov '20

20 Nov '20

Hello GSM network side community, I am doing some research in preparation for possibly setting up my own GSM/2G BTS in my rural town of Middle-of-Nowhere, California to serve as a replacement for our current GSM/2G service provided by T-Mobile USA, a contingency plan to be activated if and when the evil corporate owners of T-Mobile shut down their 2G service. I haven't bought my BTS hardware yet - I am still doing research and comparing options, and I also need to do some other preparatory work without which the BTS won't be of any use. I have a question about GSM BTS Tx power levels. Some BTS vendors advertise models with up to 10 W power output, but I don't understand how such high power output from a BTS can be useful when MS power output in the other direction is limited to 1 W in high bands or to 2 W in low bands. The whole point of a BTS is to provide service to subscribers, and in order for a subscriber to be able to make a call or to engage in a text conversation, there has to be two-way communication between the BTS and the MS: the MS needs to hear the downlink signal from the BTS, and the BTS needs to hear the uplink signal sent by the MS. If you have a BTS that puts out 10 W on the downlink, wouldn't the effective range be limited at the point where the BTS can no longer receive the 1 W (high bands) or 2 W (low bands) uplink put out by the MS? And if the range limit is set by the Tx power limit of standard GSM MS units, what is the point of having the BTS put out more power on the downlink than the very same 1 W or 2 W limit that applies to uplink Tx power? I can only reason that I must be missing something big here, as those BTS manufacturers who offer models with 10 W output surely make such hardware for some very valid use cases - but I would like to understand it better. Can someone perhaps explain this mystery to me? TIA, Mychaela

3 3

Osmocom C files syntax understanding
by Mario Lucas 19 Nov '20

19 Nov '20

Dear openBSC society, Would you be so kind to advise me on the following: I desire (dramatically want very much) to learn / understand Osmocom projects. I am a beginner in programming and i try to understand / learn C files that the project is build of. As an example i tried to learn / understand for example an Osmocom message buffer — msgb.h file. But immediately faced some syntax difficulties: This is the extract of msgb.h file: struct msgb { struct llist_head list; /*!< \brief linked list header */ /* Part of which TRX logical channel we were received / transmitted */ /* FIXME: move them into the control buffer */ union { void *dst; /*!< \brief reference of origin/destination */ struct gsm_bts_trx *trx; }; As it can be seen a structure «msgb» has as one of its components another structure — «gsm_bts_trx» But in whole Osmocom BB project files i could not find definition / description of struct «gsm_bts_trx». Would you kindly advise me please how to see which components / constituents / elements are in this gsm_bts_trx structure? From which components is struct gsm_bts_trx build of? Thank you so much for your kind advise. -- Mario Lucas

1 0

Ericsson RBS-2206 startup with OSMO
by Ivan Babanov 17 Nov '20

17 Nov '20

Hello all! I'm still trying to bring onAir any of BTS in lab. Today we were trying with Ericsson RBS-2206. We limited hardware to the minimal possible setup containing: DXU-21 dTRU-1800 CDU-G 1800 And we created IDB with 1 cell 1TX 2RX After it we tried to use default config from master branch initially created for RBS-2308. It worked pretty fine except RF Power which was configured as 41dBm and 41 - 12 = 29 dBm. Value 29 was not acceptable for our RBS. I checked with Ericsson BSC Doc and found that our RBS2206 has max RF output 47dBm for DCS1800. (btw, RBS2308 has only 34dBm max output according to the same document, maybe config needs to be corrected) After setting 47dBm to config, TX-0 was configured correctly and Operational led was on. The main problem we are faced now is unavailability to perform "Enable"action on TX and RX objects and all next steps are not successful too. After getting logs from RBS (all files are attached) I see that TX and RX enabling fails with line: [20-11-03 11:51:27.264] 0\RC_HWU_TX hwu_tx_state.c:223 TRACED:TX Enable FAILED!, RCFW_ATC_State NOT Synchronized Looks like internal oscillator is not ready. So, the question is how to make internal oscillator synchronized? Could it be an E1 Sync stability issue caused by Digium cards? I remember we discussed it on earlier steps of bringing up OSMO-BSC. Now I have just 2 ideas what to do: 1. Set Digium card to get Sync from RBS. Now Digium is configured for Internal clocking and acts as master. Maybe in case when both sides will be configured to get sync from E1 it will decrease difference between internal clock of RBS and E1 and RBS will get Synced state. 2. Theoretically I can try to use Nokia DX200 BSC as a clock master for Digium and deliver sync to RBS from Digium. I'm not sure if timing accuracy is the same for Nokia and Ericsson HW. One more question is where can I find some info about timing accuracy for BTS and any possible way to check it on the existing E1 line? Thank you Babanov Ivan

4 5

pySim incorrectly detecting as OpenCells-SIM?
by Albert Franklin 06 Nov '20

06 Nov '20

Hello I tried to buy a sysmoISIM-SJA2 but it was not available to my region, so I acquired a Chinese writable sim card with adm keys (https://www.aliexpress.com/item/32813645415.html). With their software I can read PIN, PUK, ADM, ISMI, PLMN, EHPLMN, etc exactly as on the image on the link mentioned. pcsc_scan detected it (even with a weird name) from a Chinese brand manufacture using https://github.com/LudovicRousseau/pcsc-tools/blob/master/smartcard_list.txt. I tried pySim-read and it failed on the end saying that OpenCellsSim' object has no attribute 'read_ehplmn'. I'm sharing the full output if anyone is interested. It's weird because it fails to read ISMI and ICCID for example and other fields. I started recently studying this area, I took a look at pySim code and looks like that it's based on size of data to detect if it's OpenCells or not (which I believe is not my case). Is there a easy way to know if my Chinese card is OpenCells or whatever they are? $ ./pySim-read.py -p 0 Using PC/SC reader interface Reading ... Autodetected card type: OpenCells-SIM ICCID: IMSI: None GID1: ffffffff GID2: ffffffff SMSP: ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff SPN: CMCC Display HPLMN: False Display OPLMN: False PLMNsel: 32d00032d01034f06045f08032f32212f020ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff PLMNwAcT: ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused OPLMNwAcT: 32d0004000 # MCC: 460 MNC: 000 AcT: E-UTRAN 32d0008000 # MCC: 460 MNC: 000 AcT: UTRAN 32d0000080 # MCC: 460 MNC: 000 AcT: GSM ... ffffff0000 # unused ffffff0000 # unused ffffff0000 # unused HPLMNAcT: 32d0004000 # MCC: 460 MNC: 000 AcT: E-UTRAN 32d0008000 # MCC: 460 MNC: 000 AcT: UTRAN 32d0000080 # MCC: 460 MNC: 000 AcT: GSM ACC: ffff MSISDN: Not available Administrative data: 00000002 MS operation mode: normal operation Ciphering Indicator: disabled SIM Service Table: ff33ffff00003f033000f0c3 Service 1 - CHV1 disable function Service 2 - Abbreviated Dialling Numbers (ADN) Service 3 - Fixed Dialling Numbers (FDN) Service 4 - Short Message Storage (SMS) Service 5 - Advice of Charge (AoC) Service 6 - Capability Configuration Parameters (CCP) Service 7 - PLMN selector Service 8 - RFU Service 9 - MSISDN Service 10 - Extension1 Service 13 - Last Number Dialled (LND) Service 14 - Cell Broadcast Message Identifier Service 17 - Service Provider Name Service 18 - Service Dialling Numbers (SDN) Service 19 - Extension3 Service 20 - RFU Service 21 - VGCS Group Identifier List (EFVGCS and EFVGCSS) Service 22 - VBS Group Identifier List (EFVBS and EFVBSS) Service 23 - enhanced Multi-Level Precedence and Pre-emption Service Service 24 - Automatic Answer for eMLPP Service 25 - Data download via SMS-CB Service 26 - Data download via SMS-PP Service 27 - Menu selection Service 28 - Call control Service 29 - Proactive SIM Service 30 - Cell Broadcast Message Identifier Ranges Service 31 - Barred Dialling Numbers (BDN) Service 32 - Extension4 Service 49 - MExE Service 50 - Reserved and shall be ignored Service 51 - PLMN Network Name Service 52 - Operator PLMN List Service 53 - Mailbox Dialling Numbers Service 54 - Message Waiting Indication Status Service 57 - Multimedia Messaging Service (MMS) Service 58 - Extension 8 Traceback (most recent call last): File "./pySim-read.py", line 255, in <module> (res, sw) = card.read_ehplmn() AttributeError: 'OpenCellsSim' object has no attribute 'read_ehplmn' As I can't buy the sysmoISIM-SJA2 where I live, I searched for other sellers. I found this one (https://www.aliexpress.com/i/32272726951.html) where an user wrote "+ Devices work. + Use GRSIMWrite to program them initially. After you do this, you will know PIN-ADM so then pysim will work. - PsiWords could spend a little time pointing people at correct software to program cards. That would be, as they like to say, much more professional! (Especially if they want repeat business!) 21 Aug 2018 16:43". I'm curious if this card sold by other user just have a different encoding / format to read/write data from mine, because the PIN + ADM keys I also can obtain from their software, however, since my card is in another format I don't believe that I will have success to write it. Am I wrong? I saw the list of supported SIM cards and some of them are very limited. Someone already acquired a SIM card with great compatibility with pysim from China? I searched for supersim, fakemagicsim and some combinations and no success. fakemagicsim supersim magicsim grcardsim sysmosim-gr1 sysmoSIM-GR2 sysmoUSIM-GR1 sysmoUSIM-SJS1 Fairwaves-SIM OpenCells-SIM Wavemobile-SIM sysmoISIM-SJA2 Any help or advise is very welcome. -- Sent with https://mailfence.com Secure and private email

1 0

osmo-st-* projects
by Mykola Shchetinin 04 Nov '20

04 Nov '20

Hello there! The question out of curiosity. Hard to not notice quite a few of projects written in Smalltalk. Why was cellular network implementation in Smalltalk abandoned? Or was everything in C initially and you just tried out Smalltalk as a possible alternative? What was your thinking back then? Interested to know some history. Thanks a lot! P.S. of course, I see some stuff in Erlang as well, but it has an awesome Diameter support which kind of answers a similar question but related to Erlang.

2 1

Final death of the NITB, really this time.
by Keith 02 Nov '20

02 Nov '20

Hi all, I just noticed that osmo-bts commit 6d117891c93da969e0ff8b293bef97c699490f2b is the last version that can be brought up by the openBSC aka osmo-nitb. Which makes me wonder now, should the openbsc / osmocom-nitb package continue to be published to repositories?

2 1

GGSN operation / feature
by Keith 02 Nov '20

02 Nov '20

Hi All, I have scanned 3GPP documents for info on the GGSN IP network facing side, IIUC how the GGSN responds there is "out of scope" - I'm specifically wondering about sending ICMP host unreachable messages in response to packets for IPs that are not currently active in the pool. Sometimes it would happen where I was pinging an IP assigned to an MS while looking at other things in the SGSN and PCU but in the meantime the MS would cycle the PDP context and have a new IP. For this and maybe other reasons I wrote a proof of concept, probably not great code, but working, patch to have the GGSN send ICMP host unreachable. Do you think this is a desirable feature? If so I would try to clean it up and submit to code review. Also if in agreement, would it be worth making it switchable via a vty param? I am thinking of where one might not want the IP space to be probable, although I would assume that kind of thing is best left to the local firewall implementation. Patch here: http://git.osmocom.org/osmo-ggsn/?h=keith%2Ficmp Thanks. K.

2 1

Re: NMT-450
by Sipos Csaba 01 Nov '20

01 Nov '20

Hi Andreas, I pulled the new master, rebuilt my setup from source in a clean state and it works as it should. One more question though: is it possible to use the MNCC socket to connect the NMT-450 network to 2G (via Osmo-BSC), or to SIP via LCR? Thanks again! Regards, Csaba

2 1

2025

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

OpenBSC November 2020