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When the MSC allocates a channel through the ASSIGNMENT REQUEST, it may
ask for a TCH/H and a TCH/F at the same time and tell which of the two
types it prefers.
The process of channel allocation currently selects, based on the BTS,
MSC and MS capabilites exactly one apropriate codec/rate (e.g. TCH/H)
and then tries to allocate it. If that allocation fails, there is no way
to try the second choice and the assignment fails.
For example: The MSC asks for TCH/F and TCH/H, prefering TCH/F, then the
channel allocator will try TCH/F and if it fails (all TCH/F are
currently in use), then TCH/H is never tried.
Since the BSC currently only trys the first best codec/rate that is
supported it also ignores the preference.
Lets fix those problems by including the preference information and both
possible codec/rate settings into the channel allocation decision.
Change-Id: I5239e05c1cfbcb8af28f43373a58fa6c2d216c51
Related: OS#3503
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The function check_codec_pref() currently only does a basic check over
the general codec configuration of bts and msc. However, it does not yet
check if the amr codec rate settings for the BTSs contradict the
allowed/forbidden amr codec rates of the MSC. When the two settings do
contradict AMR would not work, even when everything else is correctly
configured. We need to check this on startup to spot configuration
problems quickly.
- Add function to calculate intersections of struct
gsm48_multi_rate_conf variables.
- Calculate the intersection between the multi rate config of
each BTS with the one of the MSC
Change-Id: I3537d1c89e2520d35cc0e150ba8e6d3693e06710
Related: OS#3529
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In networks with a couple of different BTSs it may be likely that one
accidently sets up a codec configuration (codec-support)) that will be
mutually exclusive towards the codec configuration for the MSC
(codec-list). We need a check that validates the configuration before
start to catch such configuration flaws quickly.
- Add a check that checks each MSC codec-list against each BTS
codec-support setting.
Change-Id: Ice827896bab1a2330741e0fccc731a04f1a07d38
Related: OS#3625
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Opposed to all other codecs that are common in GSM, AMR requires a codec
configuration that is expressed by a bitmask (S0 to S15) in the speech
codec list in the ASSIGNMENT REQUEST. Also the BSC acknowledges those
configuration in the ASSIGNMENT COMPLETE message.
At the moment osmo-bsc ignores all incoming configuration bits. The bits
in the ASSIGNMENT COMPLETE speech codec (choosen) field are hardcoded.
- Store the configuration bits while parsing the ASSIGNMENT COMPLETE
- Create an intersection with the configuration that is actually
supported by the BSS
- Return the resulting (chosen) configuration bits with the assignment
complete message.
- Use the (highest of the) agreed codec rates in RSL channel activation.
Change-Id: I2d8ded51b3eb4c003fe2da6f2d6f48d001b73737
Related: OS#3529
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The COMPLETE LAYER 3 INFORMATION message lacks the Codec List (BSS Supported)
information element. This information element is mandatory for networks
that use an IP based user plane (AoIP).
- Add function to generate the speech codec list from the current codec
settings (Available codecs)
- Generate and embed information element in L3 Compl. message
Depends: libosmocore I4e656731b16621736c7a2f4e64d9ce63b1064e98
Change-Id: Id6f2af3fdab45bf05f06aec03e222734d7a4cf70
Related: OS#3548
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Add FSMs:
- timeslot_fsm: handle dynamic timeslots and OML+RSL availability.
- lchan_fsm: handle an individual lchan activation, RTP stream and release,
signal the appropriate calling FSMs on success, failure, release.
- mgw_endpoint_fsm: handle one entire endpoint with several CI.
- assignment_fsm: BSSMAP Assignment Request.
- handover_fsm: all of intra, inter-MO and inter-MT handover.
Above FSMs absorb large parts of the gscon FSM. The gscon FSM was surpassing
the maximum amount events (32), and it is more logical to treat assignment,
handover and MGW procedures in separate FSMs.
- Add logging macros for each FSM type:
- LOG_TS()
- LOG_LCHAN()
- LOG_MGWEP(), LOG_CI()
- LOG_ASSIGNMENT()
- LOG_HO()
These log with the osmo_fsm_inst where present.
New style decision: logging without a final newline char is awkward,
especially for gsmtap logging and when other logs interleave LOGPC() calls;
we have various cases where the final \n goes missing, and also this invokes
the log category checking N times instead of once.
So I decided to make these macros *always* append a newline, but only if
there is no final newline yet. I hope that the compiler optimizes the
strlen() of the constant format strings away. Thus I can log with or without
typing "\n" and always get an \n termination anyway.
General:
- replace osmo_timers, state enums and program-wide osmo_signal_dispatch()
with dedicated FSM timeouts, states and events.
- introduce a common way to handle Tnnn timers: gsm_timers.h/.c: struct T_def.
These can be used (with some macro magic) to define a state's timeout once,
and not make mistakes for each osmo_fsm_inst_state_chg().
Details:
bsc_subscr_conn_fsm.c:
- move most states of this FSM to lchan_fsm, assignment_fsm, handover_fsm and
mgw_endpoint_fsm.
- There is exactly one state for an ongoing Assignment, with all details
handled in conn->assignment.fi. The state relies on the assignment_fsm's
timeout.
- There is one state for an ongoing Handover; except for an incoming Handover
from a remote BSS, the gscon remains in ST_INIT until the new lchan and conn
are both established.
- move bssmap_add_lcls_status() to osmo_bsc_lcls.c
abis_rsl.c:
- move all dynamic timeslot logic away into timeslot_fsm. Only keep plain send/receive functions in
abis_rsl.c
- reduce some rsl functions to merely send a message, rename to "_tx_".
- rsl_ipacc_mdcx(): add '_tx_' in the name; move parts that change the lchan state out into the
lchan_fsm, the lchan->abis_ip.* are now set there prior to invoking this function.
- move all timers and error/release handling away into various FSMs.
- tweak ipa_smod_s_for_lchan() and ipa_rtp_pt_for_lchan() to not require an
lchan passed, but just mode,type that they require. Rename to
ipacc_speech_mode*() and ipacc_payload_type().
- add rsl_forward_layer3_info, used for inter-BSC HO MO, to just send the RR
message received during BSSMAP Handover Command.
- move various logging to LOG_LCHAN() in order to log with the lchan FSM instance.
One drawback is that the lchan FSM is limited to one logging category, i.e. this moves some logging
from DRR to DRSL. It might actually make sense to combine those categories.
- lose LOGP...LOGPC logging cascades: they are bad for gsmtap logging and for performance.
- handle_classmark_chg(): change logging, move cm2 len check out of the cm3 condition (I hope that's
correct).
- gsm48_send_ho_cmd(): split off gsm48_make_ho_cmd() which doesn't send right away, so that during
inter-bsc HO we can make an RR Handover Command to send via the MSC to the remote BSS.
assignment_fsm.c:
- the Chan Mode Modify in case of re-using the same lchan is not implemented
yet, because this was also missing in the previous implementation (OS#3357).
osmo_bsc_api.c:
- simplify bsc_mr_config() and move to lchan_fsm.c, the only caller; rename to
lchan_mr_config(). (bsc_mr_config() used to copy the values to mr_bts_lv
twice, once by member assignment and then again with a memcpy.)
- During handover, we used to copy the MR config from the old lchan. Since we
may handover between FR and HR, rather set the MR Config anew every time, so
that FR rates are always available on FR lchans, and never on HR lchans.
Depends: I03ee7ce840ecfa0b6a33358e7385528aabd4873f (libosmocore),
I1f2918418c38918c5ac70acaa51a47adfca12b5e (libosmocore)
Change-Id: I82e3f918295daa83274a4cf803f046979f284366
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The vty option bts->codec-support allows the user to set the supported
codecs per BTS level. However, those values are currently only used to
make the handover decision but the logic that handles the BSSMAP
ASSIGNMENT REQUEST does not check those flags.
- Do not ignore bts->codec-support flags on BSSMAP ASSIGNMENT REQUEST
Change-Id: I285234e9c81de74d9fb9907fca2c443b08537435
Closes: OS#3361
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At the moment there are three sources that may advertise a list of
supported audio codec/rate settings. There is the MS that advertises
advertises a speech codec list and the MSC that sends a channel type
information element over A and there are also settings in the bsc
configuration file that may restrict the codec/rate types that are
allowed to use.
The function match_codec_pref() looks at all of the three buckets and
selects a codec that satisfies all three. This is already a somewhat
complicated process, overit is very isolated, so lets give it its own
c-file.
Due to the lack of unit-tests it is very hard to make changes here so
lets add also unit-test to make sure that regressions are catched early.
- Put match_codec_pref() and all its helper functions into a separate
c-file.
- Add a unit test.
Change-Id: Iabedfdcec8b99a319f2d57cbea45c5e36c7b6e29
Related: OS#3361
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