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doc: add ms-channel-request.msc 

Change-Id: Iab22b8ae85a1a54d2f4002733e6068356368101b
This commit is contained in:
Neels Hofmeyr 2018-05-29 02:48:08 +02:00 committed by Harald Welte
parent 9d8d0c6731
commit c4bb31dcad
2 changed files with 64 additions and 0 deletions
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1
doc/Makefile.am
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@ -6,6 +6,7 @@ msc: \
$(builddir)/handover.png \
$(builddir)/assignment.png \
$(builddir)/lchan-release.png \
$(builddir)/ms-channel-request.png \
$(NULL)
$(builddir)/%.png: $(srcdir)/%.msc

63
doc/ms-channel-request.msc Normal file
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@ -0,0 +1,63 @@
msc {
hscale=3;
ms [label="MS"], bts [label="BTS"], bsc[label="BSC"], bsc_gscon[label="BSC conn FSM"];
ms note bsc_gscon [label="lchan allocation sequence for RSL Channel Request"];
ms => bts [label="RR Channel Request"];
bts => bsc [label="RSL Channel Request"];
bsc box bsc [label="rsl_rx_chan_rqd()"];
bsc note bsc [label="Obtain RACH data from Request: - Reference - Access Delay (TA)
- Request Reason - Channel Type"];
bsc note bsc [label="If the reason is PDCH, the RACH Request is forwarded to PCU and BSC is no
longer concerned (rsl_rx_pchan_rqd())."];
bsc note bsc [label="Always try to allocate an SDCCH regardless of the requested type, only if no
SDCCH is available, look for the actually requested channel type."];
bsc box bsc [label="lchan_alloc(SDCCH, allow_bigger=0)"];
--- [label="IF no lchan is available (neither SDCCH nor requested type)"];
bsc note bsc [label="Figure out T3122 value from bts->T3122, network->T3122 or
GSM_T3122_DEFAULT"];
bsc box bsc [label="rsl_send_imm_ass_rej()"];
bsc note bsc [label="..."];
bts <= bsc [label="RR Immediate Assign Reject"];
ms <= bts [label="RR Immediate Assign Reject (possibly grouped with up to 4 others)"];
bsc note bsc [label="rsl_rx_pchan_rqd() exits, no channel is allocated."];
---;
bsc box bsc [label="Store RACH data in lchan->rqd_ref, rqd_ta"];
bsc abox bsc [label="Start lchan->act_timer (4s, lchan_act_tmr_cb())"];
bsc box bsc [label="rsl_chan_activate_lchan(RSL_ACT_INTRA_IMM_ASS)"];
--- [label="is the chosen lchan on dynamic timeslot that is currently used as PDCH?"];
bsc box bsc [linecolor=red,label="Osmocom style dyn TS use the lchan->act_timer for an RSL RF
Channel Release, to release PDCH mode. This will actually overwrite above act_timer!"];
bts <= bsc [label="i) RSL RF Chan Release of PDCH (Osmocom dyn TS)"];
bts <= bsc [label="OR ii) RSL PDCH Deact (ip.access dyn TS)"];
bsc -> bsc_gscon [label="gsm0808_assign_req() returns early"];
bsc_gscon abox bsc_gscon [label="ST_WAIT_ASS_COMPL (GSM0808_T10_VALUE=6s)"];
...;
bts note bsc_gscon [linecolor="red",
label="Osmocom style dyn TS use lchan->act_timer to watch over RF Chan Release, but there
seems to be no timer watching over PDCH Deact!"];
...;
bts => bsc [label="i) RSL RF Chan Release ACK (Osmocom dyn TS)"];
bts => bsc [label="OR ii) RSL PDCH Deact ACK (ip.access dyn TS)"];
bsc box bsc [label="rsl_chan_activate_lchan() re-invoked"];
---;
bsc box bsc [label="lchan->state = LCHAN_S_ACT_REQ"];
bts <= bsc [label="RSL Chan Activ: Immediate Assignment"];
...;
bsc note bsc [label="Timeout of lchan->act_timer causes the
lchan->state to go to LCHAN_S_BROKEN, but no events or actions
are triggered."];
...;
bts => bsc [label="RSL Chan Activ ACK"];
bsc box bsc [label="rsl_rx_chan_act_ack()"];
bsc box bsc [label="Stop lchan->act_timer"];
bsc box bsc [label="lchan->state = LCHAN_S_ACTIVE"];
bsc -> bsc [label="S_LCHAN_ACTIVATE_ACK (has no effect)"];
bsc note bsc [label="Since this was an Immediate Assignment, no further action is required on
behalf of the BSC. The MS is now free to use the lchan."];
}