OpenBSC January 2025

openbsc@lists.osmocom.org

8 participants
24 discussions

Issues with writing adoc manual for contributed library
by Mychaela Falconia 27 Jun '25

27 Jun '25

Hello Osmocom community, Over the past several months I developed my own RTP endpoint implementation library (alternative to libortp), and I seek to get it merged into libosmo-netif so it can be used by OsmoBTS as an option: https://gerrit.osmocom.org/c/libosmo-netif/+/39280 https://gerrit.osmocom.org/c/libosmo-netif/+/39281 https://gerrit.osmocom.org/c/libosmo-netif/+/39291 I am now working on documentation, which I need to finish before I can lift these patches out of WIP in Gerrit. The last of the 3 WIP patches linked above is the one adding an adoc manual, built with the same tools as other Osmocom manuals, and I need some help with this one: 1) When I run './configure --enable-manuals' followed by 'make' on the Debian machine which Vadim provided to me for Osmocom documentation work, everything seems successful and I get a PDF rendering of my WIP manual. However, as soon as I uploaded this patch to Gerrit, I see a build failure in Jenkins. What am I doing wrong? I'm afraid that my knowledge of Autotools is not good enough to figure this one out. 2) My progress in writing the actual manual has reached the point where I need to insert some graphical diagrams showing the flow of RTP packets and the latency and jitter they experience in transit. I am thinking of one horizontal axis showing regularly spaced packets as they are emitted by the source, then forward-and-down arrows showing their transit with fixed or variable latency, then another horizontal axis below showing the receiver's view of time, with marked arrival times of packets (endpoints of latency arrows) and fixed-spacing times when the GSM or TDM system polls the jitter buffer. Question: what is the appropriate tool within the accepted Osmocom adoc suite for drawing such diagrams? If I weren't trying to get my RTP implementation accepted into Osmocom, I would have written this manual in troff on my favorite 1980s UNIX system, using pic preprocessor in the troff suite for graphical drawings like this one - but I reason that I need to write my manual within Osmocom documentation framework in order to maximize the chance of the associated code library being accepted into libosmo-netif, with follow-on patches to osmo-bts to use it optionally as an alternative to libortp. 3) When I do successful test builds on Vadim's Debian machine and get a PDF rendering of my WIP manual, the cover page in the PDF features both Sysmocom and Osmocom logos just like the mainstream Osmocom manuals, with Sysmocom logo on top. While this arrangement is probably appropriate for the existing manuals which were written predominantly by members of Sysmocom crew, it seems quite wrong for an external contributor's manual that does not contain a single sentence written by Sysmocom. How do I tweak things to remove that Sysmocom logo from the cover page, or even better, put San Diego 2G Association logo in its place? My contributions to Osmocom are directly linked to my efforts to build a new GSM network in San Diego, hence there is some symmetry between Sysmocom and SD2G in terms of Osmocom FLOSS project contributions, except for the rather big asymmetry in that SD2G is strictly non-profit. M~

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dynamic traffic channels
by Neels Hofmeyr 20 May '25

20 May '25

On Tue, Jun 28, 2016 at 10:05:28AM +0200, Harald Welte wrote: > [translated from german] > is it certain that we switch a channel to PDCH only when > gprs mode != none? A TS can be GSM_PCHAN_TCH_F_PDCH; those are the only ones for which we send a PDCH ACT message. We send a PDCH ACT message - during init (CHANNEL OML's state changed to enabled -> send PDCH ACT), - and upon channel release ack when pchan == GSM_PCHAN_TCH_F_PDCH. So the question is, when we receive a channel release ack, could that be the PDCH release and we switch PDCH right back on by accident? No, because we only receive a chan rel ack when the *TCH/F* is being released. That is because the PDCH release is initiated "internally" from the PDCH DEACT, and thus this condition in common/rsl.c rsl_tx_rf_rel_ack() catches on, which existed before dyn PDCH: if (lchan->rel_act_kind != LCHAN_REL_ACT_RSL) { LOGP(DRSL, LOGL_NOTICE, "%s not sending REL ACK\n", gsm_lchan_name(lchan)); return 0; } In rsl_rx_rf_chan_rel() the rel_act_kind is set to LCHAN_REL_ACT_RSL, but not in the rsl_rx_dyn_pdch(). This is analogous to the ip.access way -- the ip.access nanobts replies to a PDCH DEACT with a PDCH DEACT ACK and doesn't send a separate channel release ack. Maybe we could set rel_act_kind to some new LCHAN_REL_ACT_IPAC_DYN_PDCH for clarity? (But we shouldn't actually send a release ack, to stay compatible.) Even though it works as-is, we should indeed add another flag check: - We do check the flags that no ACT/DEACT is already pending; - And we do send a PDCH DEACT only if ts->flags & TS_F_PDCH_ACTIVE; - But we would send a PDCH ACT despite ts->flags & TS_F_PDCH_ACTIVE. This should never happen, but it would make sense to ensure that. ~Neels

3 5

Separate RSL bootstrap to LAPD and BCCH+SACCH
by Sipos Csaba 20 Jan '25

20 Jan '25

Dear list, At the moment setting up the RSL lapd link and start its bootstrap (BCCH info and SACCH filling) is done in one go (as much as I can see). The issue with this is for the Nokia Site family: per spec. we should let the RSL lapd link to be initiated by the BTS and once that lapd link is up, the BTS sends a BTS_STATE_CHANGED message with "TRX, enabled" object id and object current state, and only after this we should start sending the BCCH info and SACCH filling (the "actual" bootstrap of the RSL). For this to work, we need the Object Identity and Object Current State attributes (which is a WIP atm), but somehow it should be possible to separate the RSL bootstrap to RSL lapd only and RSL bcch info + sacch filling. I am unaware if the above separation is possible with the current codebase, but if someone can shed some light on this, that would be appreciated. Adding the Object Identity and Object Current State will also allow us to detect the actual state changes of various BTS objects (mostly the TRX), and we can also use the BTS_CHA_ADM_STATE to actually lock/unlock TRXes, so we dont need to fake the 12.21 state anymore. Regards, Csaba

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Looking for BS11 mounting plates
by Alexander Huemer 05 Jan '25

05 Jan '25

Hi! I am in possession of a pair of Siemens BS11 mounting plates and am looking for a second pair. A photo of the plates is attached. Since - I believe - most people who play with such basestations do not mount them to a wall or pole, my hope is that some unused ones are floating around somewhere. Thanks, -Alex^Wblackbit

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OpenBSC January 2025