83 lines
3.3 KiB
Plaintext
83 lines
3.3 KiB
Plaintext
# Handover between cells, intra-BSC
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msc {
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hscale=2;
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ms [label="MS via BTS"], lchan[label="BSC lchan FSM"], ho[label="BSC Handover FSM"],
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gscon[label="BSC conn FSM"], msc_[label="MSC"];
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ms note msc_ [label="intra-BSC Handover"];
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gscon abox gscon [label="ST_ACTIVE"];
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ms => ho [label="Measurement Report"];
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ho box ho [label="Handover Decision"];
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ho box ho [label="handover_request\n(struct handover_out_req)"];
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ho note gscon [label="To make sure the conn FSM permits a handover, trigger an event:"];
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ho -> gscon [label="GSCON_EV_HANDOVER_START\ndata=handover_out_req"];
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gscon abox gscon [label="ST_HANDOVER"];
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ho <- gscon [label="handover_start\n(handover_out_req)"];
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ho box ho [label="handover_start_intra_bsc()"];
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ho abox ho [label="allocate\nHO_ST_NOT_STARTED"];
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...;
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...;
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--- [label="On any error or timeout"];
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ho box ho [label="handover_end(fail)"];
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ho -> gscon [label="GSCON_EV_HANDOVER_END"];
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gscon abox gscon [label="ST_ACTIVE"];
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ms note gscon [label="MS happily continues on the old lchan."];
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--- [label="END: 'On any error or timeout'"];
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...;
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...;
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ho box ho [label="lchan_select_by_type()"];
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ho abox ho [label="HO_ST_WAIT_\nLCHAN_ACTIVE"];
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lchan <- ho [label="lchan_activate(ACTIVATE_FOR_HANDOVER)"];
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lchan rbox lchan [label="(most details omitted, see lchan_fsm diagrams)"];
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...;
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...;
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--- [label="On lchan error or timeout"];
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lchan -> ho [label="HO_EV_LCHAN_ERROR"];
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ho rbox gscon [label="same as above"];
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--- [label="END: 'On lchan error or timeout'"];
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...;
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...;
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lchan abox lchan [label="LCHAN_ST_WAIT_ACTIV_ACK"];
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ms <= lchan [label="RSL Chan Activ"];
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...;
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ms => lchan [label="RSL Chan Activ ACK"];
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lchan -> ho [label="HO_EV_LCHAN_ACTIVE"];
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ho abox ho [label="HO_ST_WAIT_\nRR_HO_DETECT"];
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...;
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ms => ho [label="RR Handover Detect\nHO_EV_RR_HO_DETECT"];
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lchan note ho [label="At this point we should start to switch the MGW over to the new lchan.
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But this is not implemented yet, as was not before introducing these FSMs."];
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ho abox ho [label="HO_ST_WAIT_\nRR_HO_COMPLETE"];
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...;
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lchan note ho [label="The lchan FSM will continue with RSL and RTP while the HO FSM waits.
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HO_EV_LCHAN_ESTABLISHED means that both RSL and RTP are established.
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Usually, RTP will be done first, and the HO_EV_LCHAN_ESTABLISHED may be
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received even before HO_EV_RR_HO_COMPLETE.
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ho_fsm_wait_lchan_established_onenter() decides whether to wait or not."];
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...;
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ms => lchan [label="RSL EST IND"];
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lchan -> ho [label="HO_EV_LCHAN_ESTABLISHED",ID="(may come as early as this, or...)"];
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ms => ho [label="RR Handover Complete (from EST IND)\n HO_EV_RR_HO_COMPLETE"];
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ho abox ho [label="HO_ST_WAIT_\nLCHAN_ESTABLISHED"];
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...;
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lchan rbox lchan [label="when lchan FSM is done with setting up RTP"];
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lchan -> ho [label="HO_EV_LCHAN_ESTABLISHED",ID="(...may come only now)"];
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ho abox ho [label="HO_ST_WAIT_\nMGW_ENDPOINT_TO_MSC"];
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ho -> gscon [label="gscon_connect_mgw_to_msc()"];
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...;
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ho <- gscon [label="HO_EV_MSC_MGW_OK"];
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ho box ho [label="handover_end(OK)"];
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ho -> gscon [label="gscon_change_primary_lchan()"];
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lchan <- gscon [label="LCHAN_RTP_EV_ESTABLISHED"];
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ho -> gscon [label="GSCON_EV_HANDOVER_END"];
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gscon abox gscon [label="ST_ACTIVE"];
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ho box ho [label="detach from parent to not fire another meaningless GSCON_EV_HANDOVER_END"];
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ho abox ho [label="terminate"];
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}
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