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