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add some document about the channel release procedure 

also note how we are not doing what the spec says :)
This commit is contained in:
Harald Welte 2009-08-10 11:35:33 +02:00
parent 100325a87e
commit d26d3d953a
1 changed files with 74 additions and 0 deletions
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openbsc/doc/channel_release.txt Normal file
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GSM 04.08 7.1.7 / 9.1.7 RR CHANNEL RELESE
RSL 08.58 3.4 / ? RLL Link Release Request
RSL 08.58 4.6 / 8.4.5 DEACTivate SACCH
* Deactivate SACCH according to Channel Release Proc 04.08
* to be sent after RR CHANNEL RELEASE is sent to MS
RSL 08.58 4.7 / 8.4.14 RF CHANnel RELease
* tells the BTS to release a radio channel
* "when an activated radio channel is no longer needed"
* BTS responds with RF CHANnel RELease ACKnowledge
GSM 04.08 3.4.13: RR connection release procedure
* network sends RR CHANNEL RELEASE to MS on the DCCH
* start T3109
* deactivate SACCH
* MS disconnects main signalling link (by sending DISC)
* all other data links are disconnected by local end link release
* network receives DISC (BTS sends RLL REL IND to BSC)
* stop T3109
* start T3111
* when T3111 times out, the network can reuse the channls
* if T3109 times out, the network deactivates the channels
and can reuse them
* this probably means simply RF CHANnel RELease
== Implementation in OpenBSC ==
chan_alloc.c:lchan_auto_release()
* checks if use count still > 0 (abort)
* calls gsm48_send_rr_release()
* which calls rsl_deact_sacch()
* calls rsl_release_request()
* which sends RLL Link Release request
RX of RELease INDication:
* call rsl_rf_chan_release() (send RF_CHAN_REL)
RX of RELease CONFimem:
* call rsl_rf_chan_release() (send RF_CHAN_REL)
* RX of RF_CHAN_REL_ACK
* call lchan_free()
* subscr_put()
* delete release_timer
=== Integration with SMS ===
* RX of CP_ERROR or unimplemented MT
* trigger trans_free() which will lchan_auto_release()
* CP TC1* expired while waiting for CP-ACK
* trigger trans_free() which will lchan_auto_release()
* RX of RP_ERROR
* trigger trans_free() which will lchan_auto_release()
* TX of CP-ACK in MT DELIVER
* trigger trans_free() which will lchan_auto_release()
* RX of CP-ACK in MO SUBMIT
* trigger trans_free() which will lchan_auto_release()
* RX of RP-ACK in MT DELIVER (and no more messages)
* trigger rsl_release_request() for SAPI3
* RX of RP-SMMA in MT DELIVER (and no more messages)
* trigger rsl_release_request() for SAPI3