The RRC should not trigger RLC bearer establishment: this should be done
only via F1, and in the remaining code (removed here), this principle
was violated.
Further, this code was doubly wrong, as it used the CU UE ID for the
RLC, setting up bearers with IDs 1,2,3 etc instead of the RNTI.
This commit repairs the reestablishment after the introduction of the CU
UE ID in the CU, different from the DU UE ID. Now, the CU uses an
identifier different from the RNTI, used in the MAC, to refer to UEs.
To repair the reestablishment, a number of changes needed to be
introduced:
- Handle old_gNB_DU_UE_id in MAC
The MAC handles the old_gNB_DU_UE_id field in the DL RRC Message. The
commit adds encoding/decoding of the field. The MAC will drop the old
UE, but retain the CellGroup of the corresponding UE(!). Because a UE
releases the spCellGroup on reestablishment, the MAC does the same; it
needs to reapply the old configuration after a reconfiguration. For the
latter, introduce new variables to keep a "future" CellGroupConfig to be
applied (reconfigCellGroup) and a flag (expect_reconfiguration) that
applies the CellGroupConfig if a DL RRC Message transfer on DCCH, which
is assumed to be the reconfiguration.
- Add RNTI change in RLC
The RLC needs to reuse the old UE context. Hence, we simply change the
RNTI in the old context, and delete the new one.
- No PDCP UE ID change
The previous implementation of the PDCP used the RNTI; hence, the ID
needed to be switch (as above for the RLC). Since the PDCP now also uses
the CU UE ID, no identifier change is needed, and we remove all
corresponding code.
- No MAC modifications/update from CU
As foreseen by the spec, the CU does not modify or change the
cellGroupConfig in the RRC during reestablishment. This change will be
generalized in the future to all of the RRC. Also, the
nr_rrc_mac_remove_ue() function has been removed: the MAC handles any UE
changes autonomeously, without being triggered from the RRC explicitly.
- Remove reestablish_rnti_map
The RRC does not use RNTIs for UE identification. Hence, a
reestablish_rnti_map to link two UEs to each other is not necessary
anymore.
After a reestablishment, the PDCP sequence number counters have to be
reset. Implement an API to allow the RRC to reset the sequence numbers
for a particular UE in the case of reestablishment
The RRC gives its own RRC UE ID. It won't intervene if DUs assign the same RNTI to different UEs: it simply does not care what the DUs do with the RNTI.
- Use the same CU-UP in E1 as in CU-CP: we don't have a separate entity
to allocate IDs, and we just use the same as the CU-CP
- Correct gNB CU-UP/CP UE IDs in E1AP message types to 32bit
- Set CU UP UE ID explicitly for clarity
- Remove RNTI from E1 messages, E1 does not know what an RNTI is
- The CU/DU UE ID is used in DL RRC Message Transfer
- Note: The CU UE ID currently is still the RNTI
- on every DL RRC Message, the DU verifies that the UE exists
- Refactor RRC: common function to forward protected SRB PDUs
The RRC uses gNB_ue_ngap_id as its primary ID; the following commits
will introduce the usage of the (F1) gNB CU UE ID. This commits renames
the gNB_ue_ngap_id to rrc_ue_id to better reflect its usage as the RRC's
primary UE ID.
It will be used as the NGAP and F1 (CU) UE IDs.
Config options --reconfig_file and --rbconfig-file have been introduced
to modify the filenames of reconfig.raw and rbconfig.raw (e.g., in the
case of multiple UEs). These filen*ames* were to be prepended with
--rrc_config_path to set the path. In summary, three options were
necessary, when two are sufficient.
In this commit, change to the options --reconfig-file and
--rbconfig-file (slight change for harmonization with other options,
which mostly use dashes) to give the full path to the corresponding
files, and avoid to surprise users who would not expect to have three
options.
--rrc_config_path has been deprecated and an error will be printed if a
user attempts to use it.
francescomani