- OpenBSC - lists.osmocom.org

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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by teves20525＠binafex.com 05 Sep '25

05 Sep '25

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Pysim error: SW match failed
by Martin Nagy 16 Aug '25

16 Aug '25

Hi all, After buying a super Sim Kit (16 in 1) from China, I tried the reader (green PCB inside a blue transparent plastic case with a blue LED) and SIM (identified as a fakesupersim) with pysim tool. However i am getting the following error: /pySim-prog.py -n 26C3 -c 49 -x 262 -y 42 -z 1234 -j 1 -t auto Insert card now (or CTRL-C to cancel) Autodetected card type fakemagicsim Generated card parameters : > Name : 26C3 > SMSP : e1ffffffffffffffffffffffff058100945555ffffffffffff000000 > ICCID : 8949262427518313026 > MCC/MNC : 262/42 > IMSI : 262422461512085 > Ki : 7b74741a1ee14337ec23f9ab92a13648 > OPC : ccd867d60797d8d45354a51b3ef568ff Programming ... Traceback (most recent call last): File "./pySim-prog.py", line 530, in <module> card.program(cp) File "/home/nadicek/pysim/pysim/pySim/cards.py", line 231, in program self._scc.update_binary('6f30', hplmn + 'ff' * (tl-3)) File "/home/nadicek/pysim/pysim/pySim/commands.py", line 53, in update_binary return self._tp.send_apdu_checksw(pdu) File "/home/nadicek/pysim/pysim/pySim/transport/__init__.py", line 87, in send_apdu_checksw raise RuntimeError("SW match failed ! Expected %s and got %s." % (sw.lower(), rv[1])) RuntimeError: SW match failed ! Expected 9000 and got 9804. I checked mailing lists and haven’t found anybody who had similar problem with pysim. Also I have tried forcing different models of SIM, but nothing is working. Obviously I can remove this check from the script file (__init__.py in /pySim/transport), however somebody had a reason to put such condition there. I would like to ask if it is safe to remove that line of code and the purpose of that line of code. Thanks a lot and best regards Martin

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by frederickgragg＠gmail.com 16 Aug '25

16 Aug '25

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16 Aug '25

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by frederickgragg＠gmail.com 16 Aug '25

16 Aug '25

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Love Beyond Memories
by frederickgragg＠gmail.com 15 Aug '25

15 Aug '25

Love is not just a fleeting moment caught in a photograph or a soft whisper carried away by time. It is the echo that lives on, long after the moment has passed—enduring, unshaken, and infinite. "Love Beyond Memories" is more than a phrase. It’s a feeling, a promise, a journey that stretches past the borders of time and space, holding strong even when the world around us changes. In every heartbeat, there is a memory. In every memory, a trace of love. But what happens when the memories begin to fade? When the laughter grows quieter, and the faces blur with time? That’s when true love reveals itself—not in the clinging to the past, but in the strength to carry it forward. Love Beyond Memories means living with the presence of love even when the moments are gone. It’s knowing that the ones we’ve loved, the ones we’ve lost, and the ones we hold close have left an indelible mark on our souls. Whether it’s the touch of a hand, the sound of a familiar song, or a scent that brings the past rushing back—these are not just memories. They are pieces of a love that never died. They are testaments to connection, to bonds that don’t break, even when life takes unexpected turns. https://beyond-memories.com/ speaks to the eternal nature of connection. It is for those who have loved deeply and lost, for those who cherish the little things, and for those who believe that love doesn’t end—it transforms. It lingers in the quiet moments, in the stories we tell, in the eyes of our children, and in the legacy we build. Whether you are commemorating a loved one, celebrating a lifelong partnership, or embracing a new chapter shaped by past joys and sorrows, Love Beyond Memories is a celebration of love that lives on. It reminds us that while time moves forward, love stays with us—quiet, constant, unwavering. Let this be your reminder: every moment you have loved, you have created something eternal. A memory, yes—but also a truth, a light, a legacy. Love doesn’t stop where memory fades. It goes beyond.

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