This commit introduces CSFB (circuit switched fall-back) capabilities to
srsLTE. Actually, all the eNB has to do is to send a
RrcConnectionRelease with the RedirectedCarrierInfo IE.
The MME triggers this by the S1AP CS Fallback Indicator IE, which may
be present either in the Initial Context Setup Requst or in the
UE Context Modification Request.
As srsLTE has no support for the UE Context Modification Request at all
yet (!), basic support for this message is introduced in this patch.
Both Mobile Originated and Mobile Terminated CSFB with a coupel of
different UE models have been verified using this patch in a setup
consisting of srsENB attached to an undisclosed EPC connected via SGsAP
to a complete Osmocom 2G network.
Closes: #358Closes: #363
RRC-PHY interface refactor. Moved RRC-MAC interface to rrc_asn1_utils and created RRC-PHY interface also in rrc_asn1_utils. All ASN1 includes should be made from rrc_asn1_utils only keeping ue_interfaces clean of ASN1
Tested with different common and dedicated configurations (64QAM UL, 256QAM, CA, SRS enabled/disabled, etc)
- add interface to RRC to allow NAS to query the DRB for a given
EPS bearer id
- extend interface for NAS to setup GW to also pass LCID of bearer
- in NAS, use this new interface to pass actual LCID of the default
DRB when creating the TUN device
- abstract UE object now consists of a radio, a PHY, and a stack layer
- add new stack abstraction layer that combines MAC, RLC, RRC, PDCP, NAS and GW
- PHY layer now has a single stack interface and does not talk to MAC and RRC seperatly
This entails:
* Adding S1AP paging messaging to the MME.
* Adding the Downlink Data Notification, Donlink Data Notification Acknoledgment, and Downlink Data Notification Failure Messages.
* Adding the logic at the GTP-U to detect that Downlink Data notification needs to be sent.
* Proper handling of the new GTP-C messages at the MME GTPC and SPGW GTPC classes
* Add queuing mechanisms at the GTP-U while waiting for paging response. Queue is flushed when paging fails (timeout or other).
* Make sure eNB's SCTP information is properly stored.
* Make sure UE's GUTI information is properly stored.
* Adding timer creation at NAS using timerfd_create
* Adding the ability to add and remove the timer file descriptor to the MME main select loop
* Adding the ability to the MME for the NAS to check if a timer is running
* Adding the timer expiry handling functionality at the MME