OpenBSC September 2025

openbsc@lists.osmocom.org

7 participants
20 discussions

Struggling with Your Final Research? Let's Talk About PhD Dissertation Help!
by teves20525＠binafex.com 27 Nov '25

27 Nov '25

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New MGW for E1 Abis, future ThemWi sw plans
by Mychaela Falconia 24 Nov '25

24 Nov '25

Dear Osmocom community, I am pleased to announce the first usable version of my new MGW for use with OsmoBSC and E1-based BTS: https://gitea.osmocom.org/themwi/tw-e1abis-mgw This new sw component works as a drop-in replacement for osmo-mgw in the role of BSC-associated MGW for E1 Abis. Principal new features compared to OsmoMGW-E1 are: * The path from RTP input to fixed-timing TRAU-DL output passes through ThemWi jitter buffer (twjit), instead of blindly converting every received RTP packet to a TRAU-DL frame, queueing those frames to I.460 MUX Tx and hoping for the best. * For FR codec in the present implementation and for EFR coming later, a proper UL-to-DL transform (aka TFO transform) is applied to this RTP-to-DL path. This way if the stream of UL frames from the other call leg includes gaps due to radio errors, FACCH stealing or DTXu pauses, or if gaps are caused by packet loss, the stateful transform will produce proper error concealment or comfort noise insertion per TS 28.062 section C.3.2.1.1. * CSD is supported! This development may be the first time in Osmocom history of CSD working on an E1-based BTS. I tested this new MGW with Nokia InSite BTS and confirmed it working with all 3 classic GSM voice codecs (FR, HR and EFR) and with CSD up to 9600 bps. CSD at 14400 bps (D145_SYNC and EDATA frames) is supported too, but remains untested due to lack of needed support in OsmoMSC. My eventual goal is to use OsmoBSC and this new MGW with Ericsson RBS6k BTS, consisting of DUG20 and RUS or RRUS. I already have DUG20 and RUS01 hardware, but given all other work I still have to do on ThemWi CN software, I haven't got around to playing with Ericsson gear yet. My plans going forward are: * Get back to twrtp patches in Gerrit: implement the next round of changes per last round of review, and hopefully get twrtp into libosmo-netif so we can make it an option in OsmoBTS, in addition to E1 BTS. * Finish long-deferred work on libgsmhr1 in gsm-codec-lib. HRv1 codec is of course of no practical interest, can be regarded as a "just for fun" retronetworking feature, but I need to finish it so certain ThemWi components can rely on having encoders and decoders for all GSM codecs always available, and my TFO transform for HRv1 will serve as a stepping stone toward much more important TFO transform for EFR. * After the above, the big work item for me will be ThemWi-MSC. I won't get into details as I don't like writing about vaporware, but many of you know that currently I am still stuck on 2023-02 version of OsmoMSC while running newer versions of all other components. ThemWi-MSC will be my proper solution, but I'll write about it in detail only when it becomes a reality. Never stopping work toward restoration of top-quality GSM/2G networks, Mother Mychaela

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19 Nov '25

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ip.access nano 3G S8 Configuration
by John Thewlis - Meath Broadband 18 Nov '25

18 Nov '25

We are trying to setup this AP as part of the 3.5G Osmocom project. We have the software stack operational and are now preparing the nano for testing. When we try to login via telnet at port 8090 we are getting a constant refusal to connect:- root@osm/openbsc/openbsc/src/ipaccess# telnet 192.168.192.30 8090 Trying 192.168.192.30... telnet: Unable to connect to remote host: Connection refused The device seems to be locked as indicated by the leds on the front panel. We have tried resetting the nano to see if this would help but to no avail. Any ideas as to how to access the device for initial configuration?. Thanks John

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GPRS - local and foreign TLLIs
by Luca Melette 18 Nov '25

18 Nov '25

Hello everybody, after setting up a nanoBTS with OpenBSC/SGSN/GGSN, I had some troubles trying to connect my smartphone to the GPRS cell. Investigating the BTS-to-SGSN traffic, I saw that the frames sent by the SGSN were all marked with the same N(U) value (at LLC layer), the value was 0. With some debug, I found that the there was a mismatch in the TLLI storage, used to keep the status of attached terminals. The mentioned code is contained in gprs_llc.c, involving LL Entity functions and gprs_llc_tx_ui(). /* look-up or create the LL Entity for this (TLLI, SAPI) tuple */ lle = lle_by_tlli_sapi(msgb_tlli(msg), sapi); if (!lle) { struct gprs_llc_llme *llme; LOGP(DLLC, LOGL_ERROR, "LLC TX: unknown TLLI 0x%08x, " "creating LLME on the fly\n", msgb_tlli(msg)); llme = llme_alloc(msgb_tlli(msg)); lle = &llme->lle[sapi]; } The TX function uses the previously received TLLI to lookup for the LLE. The lle_by_tlli_sapi() performs the search, but preliminary it applies a foreign2local TLLI conversion to ensure to have a local one. Since no valid entry for the searched TLLI is found, a new one is created. And the problem is here. The new entry has the foreign TLLI. Next time the lookup fails again, and a new entry is created. This way, the counter N(U) is always reset, and the mobile do not recognize the message sequence and no attach is possible. My question is about foreign and local TLLIs. I patched the lookup, avoiding the conversion, so that the LLE is found and everything works fine... but... What is the sense of the conversion? Should the TLLI be always stored as a local one? Can this problem be solved with another foreign2local while allocating new entries? Actually, my problem has been solved with that workaround. But I'm curious to know what is the right way. Hope somebody can answer :) Thanks. Cheers, LM

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More efficient RTP transport for CSD
by Mychaela Falconia 25 Sep '25

25 Sep '25

Dear Osmocom community, Those of you who had occasion to work with CSD probably noticed that the standard RTP payload format prescribed for AoIP by 3GPP Rel8+ (64 kbit/s CLEARMODE) is extremely wasteful: 160 bytes of payload every 20 ms (compared to a maximum of 33 bytes every 20 ms for voice calls), and most of that 160-byte CLEARMODE payload is constant filler. The actual information content for CSD channels traveling across A interface (data bits plus all metadata preserved, strictly lossless conversion) fits into 16 bytes for CSD modes up to 4.8 kbit/s, 32 bytes for 9.6 kbit/s or 37 bytes for 14.4 kbit/s - much more compact than the 160-byte standard! Because my non-profit org in USA (American 2G Cooperative) will soon be operating a public GSM/2G network as a membership co-op, we have a legal and ethical obligation to provide all services strictly at cost. Radio resource usage is exactly the same between voice and data calls, while CPU load on tw-border-mgw machines in the CN will often be even less with CSD than with EFR or AMR speech transcoding - hence there is no legitimate reason for CSD calls to be more expensive than voice. Yet the bloated RTP format prescribed by 3GPP Rel8+ artificially increases the cost of IP transport within the network. My solution to the problem: yet another TW-TS, specifying a modified version of AoIP interface with compressed CSD. Here is the spec: https://www.freecalypso.org/specs/tw-ts-007-v010001.txt An updated version of TW-TS-003 (BSSMAP extension spec) spells out how the MSC requests the use of compressed CSD instead of standard TS 48.103 on AoIP by adding RTPext IE to ASSIGNMENT REQUEST or HANDOVER REQUEST, with the right bit set to request TW-TS-007 RTP format. In terms of implementation of this newly defined feature in Osmocom, my plan is as follows: * Within the past couple of years I extended osmo_trau2rtp() and osmo_rtp2trau() to support CSD on E1 BTS, using standard CLEARMODE format on RTP side. I plan to extend these functions to support TW-TS-007 as well. * Combination of mainline OsmoBSC plus tw-e1abis-mgw has fully working CSD with E1 BTS, already tested with Nokia InSite. If my idea for representing TW-TS-007 compressed CSD format in MGCP/SDP is acceptable (please see chapter 9 and Annex A in the spec linked above), I would like to extend OsmoBSC to be able to command tw-e1abis-mgw via MGCP/SDP to emit either standard CLEARMODE or TW-TS-007 per request from MSC. The above points are for E1 BTS. With IP-native OsmoBTS, we have two options: 1) We could add more logic to OsmoBTS to emit either standard CLEARMODE or TW-TS-007, just like we already do for TW-TS-001/002 carrying TRAU-UL metadata bits for FR/HR/EFR. 2) We could leave OsmoBTS completely unchanged, speaking only standard CLEARMODE format for CSD, and have OsmoBSC-associated OsmoMGW convert on the fly (we are dealing with strictly lossless conversion here, not bringing back extra metadata as with other TW-TS) if the MSC asked for TW-TS-007 compressed RTP format. Option 2 seems easier to implement, and I am leaning toward this option. Of course this option only makes sense when osmo-bsc, osmo-mgw and osmo-bts-trx run on the same SBC next to or inside SDR-based BTS, or when the link between the BSC and the BTS is a local Ethernet cable, while A interface travels across public Internet or other networks where bandwidth matters. What does the community think? For my own operation E1 BTS is a higher priority (I still plan on using surplus Ericsson RBS6k gear), hence there is plenty of time for Osmocom community to provide feedback on how y'all would like to see this mechanism working with IP-native OsmoBTS. In terms of upcoming Gerrit patches related to TW-TS-007, I plan to work on libosmo-abis next, implementing lossless conversion functions and extending osmo_trau2rtp() and osmo_rtp2trau() for efficient, native support of compressed CSD. GSM/2G Forever, Mother Mychaela P.S. If anyone has constructive criticism regarding chapter 9 or Annex A in the TW-TS-007 spec linked above (AoIP and SDP aspects), it is not too late to revise those parts.

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Financial Accounting Assignment Help
by Katherine Salvator 23 Sep '25

23 Sep '25

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Mobile disassociates from sysmobts 1002 after call
by Christoph Quirin Lauter 10 Sep '25

10 Sep '25

Hello, I am sorry, this might not be the right place to ask. I am kind of a newbie to the osmocom stack as well, so please be gentle with me. I recently got an FCC license in the 900MHz range and I am running sysmobts 1002 at home. I have updated it from NITB to the modern world of course. Everything seems to work as it should but there is one issue: A Pixel 9 Pro Android phone with a sysmocom SIM card (999/70) connected to the sysmobts disassociates -in certain cases- with the BTS/BSC after a call and displays "No network". It will never reassociate again, unless I put the phone in airplane mode and back on. Then it reassociates immediately again. I cannot see anything particular in the osmo-bsc/osmo-bts-sysmo logs but as I said, I am a newbie. I will be happy to post the logs if this is helpful. The issue does not arise for each call, only certain calls. I use osmo-sip-connector to an asterisk. Is this a known issue? Is it an issue with the phone? Did I configure something in a wrong way? I will do some experiments with another GSM phone. Thank you! Christoph Lauter

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Having trouble balancing GSM projects and coursework?
by fennellmarian018＠gmail.com 08 Sep '25

08 Sep '25

As someone knee-deep in OpenBSC settings and attempting to gain a firm understanding of BTS to BSC handovers, I've struck a stumbling block in balancing my technical deep dives with academic duties. Between tracing Abis interface logs and diagnosing paging issues, I barely have time to concentrate on my finance studies. To be honest, I've pondered finding someone to take my accounting class for me so that I can continue with my telco experiments here. I'm not sure whether anyone else is dealing with the same workload, but if you've discovered a solid workflow or technique, I'd love to hear about it because OpenBSC is currently capturing my full attention. visit: https://takemycourseforme.us.com/pay-someone-to-take-my-online-accounting-c…

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Struggling with Assignments? Let’s Talk About It!
by teves20525＠binafex.com 05 Sep '25

05 Sep '25

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OpenBSC September 2025