Dear Osmocom community,
It's my pleasure to announce the next OsmoDevCall at
September 24, 2021 at 20:00 CEST
at
https://meeting4.franken.de/b/har-xbc-bsx-wvs
This meeting will have the following schedule:
20:00 meet + greet
20:15 presentation on "ISO 7816 smart card interface FPGA softcore" by tnt
21:00 USSE: unstructured supplementary social event [*]
22:00 close of call
Attendance is free of charge and open to anyone with an interest
in Osmocom.
More information about OsmoDevCall, including the schedule
for further upcoming events can be found at
https://osmocom.org/projects/osmo-dev-con/wiki/OsmoDevCall
Looking forward to meeting you on Friday.
Best regards,
Harald
[*] this is how we started to call the "unstructured" part of osmocom
developer conferences in the past, basically where anyone can talk about
anything, no formal schedule or structure.
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- Harald Welte <laforge(a)osmocom.org> http://laforge.gnumonks.org/
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"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)
Dear Forum members i am not sure this question directly relates to Osmocom, but I don’t know where I can post it else …. If you know some active / alive technical forum which relates to GSM side (frequencies, modulations, GMSK etc etc) it would be very great if you could advise me …..
Meanwhile I ll continue with my question….
51 TDMA multiframe starts with a FCCH which carries frequency correction burst on TS0.
Due to nature of GMSK modulation and initial zeros of frequency correction burst the aired signal (signal that GSM modulator emits into air) as I understand is nothing but sine wave of an approximately 67Khz on top of the carrier frequency. Once mobile finds the frequency correction burst on some frequency it subtracts 67 Khz and precisely gets / sits on beacon frequency. So when it is said that upon switching the mobile phone on - it is looking for frequency correction bursts means in different words that it is looking for sine wave in GSM frequency interval it can work. Let’s say if my phone can work only in E-GSM900 interval (925 - 960 Mhz) it is looking for sine wave (frequency correction burst) and once finds it will subtract 67 Khz and it will be precisely the carrier frequency of beacon channel ?
So if I use my rtl-sdr and software that analyzes RF spectrum (something like only oscilloscope) in 925 960 Mhz interval and I notice sine waves with periodic occurrence - as many times as FCCH appears in 51 multiframe - can I say that got frequency correction burst and subtracting 67 Khz I got beacon frequency ?
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Mario Lucas
Dear All,
Could you please advise me based on what logic (how) can i decompose logical channel configuration CCCH+SDCCH4 which is mapped on TS0… ?
So my understanding is as follows:
There are 51 TDMA frames in multiframe, therefore i am having 51 consecutive TS0 slots. So CCCH+SDCCH4 should be redistributed in these 51 slots.
SDCCH4 means that there are 4 SDCCH blocks, each block is having 4 bursts or 4 timeslots in another words (as i understand to transmit SDCCH «unit data» it is needed 4 burts), so 16 slots are occupied by SDCCH.
Does it mean 51-16 = 35 slots to be occupied by CCCH ?
If i use following notation CCCH=C, SDCCH1=S1, SDCCH2=S2, SDCCH3=S3 and SDCCH4=S4 does the decomposition looks like:
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC S1S1S1S1 S2S2S2S2 S3S3S3S3 S4S4S4S4
If so should not there be an idle slots … ?
Thank you so much.
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Mario Lucas
Dear All,
I try to run a virtual BTS:
systemctl start osmo-stp
systemctl start osmo-hlr
systemctl start osmo-msc
systemctl start osmo-bsc
and finally i run osmo-bts-virtual…. but i am getting following outcome:
DOML <0001> oml.c:91 OC=GPRS-CELL INST=(00,ff,ff): Sending PCU version report to BSC: PCU socket has LOST connection
DPCU <0009> pcu_sock.c:1084 PCU socket connected to external PCU
DPCU <0009> pcu_sock.c:967 Received 212 bytes on PCU Socket, but primitive size is 1006, discarding
DPCU <0009> pcu_sock.c:895 PCU socket has LOST connection
I tried to run osmo-pcu (I thought may be this will resole above issue) but it keeps saying:
<000b> gprs_ns.c:322 NSVCI=65534 Creating NS-VC with Signal weight 1, Data weight 1
<000e> telnet_interface.c:104 Available via telnet 127.0.0.1 4240
<0001> osmobts_sock.cpp:224 Opening OsmoPCU L1 interface to OsmoBTS
<0001> osmobts_sock.cpp:248 osmo-bts PCU socket /tmp/pcu_bts has been connected
<0001> pcu_l1_if.cpp:114 Sending 0.8.0 TXT as PCU_VERSION to BTS
PCU interface version number of BTS (10) is different (9).
Please re-compile!
I have
OsmoPCU version 0.8.0
OsmoBTS version 1.2.0.307-6e27
Would you kindly advise whats going on please….
As i understand osmo-pcu is to implement GPRS into my GSM network… ok but if i dont want GPRS implemented thus i dont need PCU …. can i run virtual bts without this PCU things ?
pls help …..
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Mario Lucas
