path: root/doc/old/ms-channel-request.msc
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Diffstat (limited to 'doc/old/ms-channel-request.msc')
1 files changed, 63 insertions, 0 deletions
diff --git a/doc/old/ms-channel-request.msc b/doc/old/ms-channel-request.msc
new file mode 100644
index 000000000..c0ef60fc7
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+++ b/doc/old/ms-channel-request.msc
@@ -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."];