PDU Session Release
This MR implements end-to-end PDU Session Release functionality
according to 3GPP TS 38.413 and TS 38.331 specifications.
Reason for Change Previous implementation had incomplete and wrongly
places tunnel cleanup during PDU session release. UP cleanup shall be
done at CUUP, RRCReconfiguration shall be sent after retrieval of
updated CellGroupConfig from the DU. This implies F1 and E1 exchanges
during PDU session release procedure.
Major Changes:
1. RRC PDU Session Release: DRBs and PDU session teardown in NGAP PDU
Session Release Response callback
- Helper Functions: Introduced rm_pduSession,
find_drb_by_pdusession_id and rm_drbs() helpers to locate and clean
up DRBs linked to a specific PDU session
- Targeted Cleanup: RRC PDU Session and per-session DRB removal in
rrc_gNB_send_NGAP_PDUSESSION_RELEASE_RESPONSE()
- Status Cleanup: Removed unused PDU_SESSION_STATUS_RELEASED status
2. RRC PDU Session Release: Refactor
rrc_gNB_process_NGAP_PDUSESSION_RELEASE_COMMAND
- Any PDU session in the pdusession_release_params list that is
present in the RRC list can be set to release, regardless of its
status
- Function Signature Update: Updated function signature and other
minor changes
- Response Handling: rrc_gNB_send_NGAP_PDUSESSION_RELEASE_RESPONSE is
sent upon completion of RRCReconfiguration
3. RRC PDU Session Release: add missing procedures E1AP Integration:
- Populates E1AP Bearer Modification for each to be released session
- PDCP Enhancement: Added nr_pdcp_release_drbs() to remove all DRBs
linked to a given PDU session in CUUP
- GTP-U Cleanup: GTP tunnel teardown handled in CUUP
e1_bearer_context_modif() using correct F1 or N3 GTP instance
4. NR PDCP/GTP:
- Enhanced Tunnel Deletion Logic: Separate handling for N3 tunnels (1
per PDU session) and F1-U tunnels (1 per DRB)
- New PDCP API Function: Added nr_pdcp_get_drb_ids_for_pdusession()
function to retrieve all DRB IDs associated with a specific PDU
session
5. RRC PDU Session Release: F1AP-based UE Context Modification:
- Replaced direct RRC message transfer with F1AP UE Context
Modification Request for proper retrieval from DU
- Cell Group Configuration: handling of updated CellGroupConfig from
DU ensures DRB release at CU
6. Docs and testing:
- Added PDU session add/remove test cases to 25 PRB RFSIM pipeline
- Documentation: Added PDU Session Release sequence diagram
- Telnet Commands: Added ci command to trigger NGAP PDU Session
Release and ciUE command to trigger establishment of a new PDU
Session
7. Additional fixes:
- UE RLC Management: ensure release of RLC entities
- Unify NG delay control before calling the RRC NGAP handler, for both
Setup and Release
8. Code Cleanup: Cleaned up unused GTP teardown functions.
Closes#867
Reimplement nFAPI message exchange between L1 and L2 following the
changes in parent commit removing msgDataTx.
Avoid direct calls and use NR_IF_module fptrs to avoid linking problems.
allowing to remove some function definitions that are not needed.
Refactor DLSCH scheduler
Refactor the DLSCH post processor similarly to what has been done in
!3521 with the goal of saving an additional iteration through all UEs,
hopefully making the DLSCH scheduler faster.
It further includes changes to make working with and debugging multi-UE
operation easier:
- add some measurements in L1 (for total TX/RX time)
- a new option MACRLCs.[0].stats_max_ue to limit the number of UEs in
the periodic output (default: 8, 0=disable)
- avoid stack overflow in the MAC
- fix the writing of stats to nrMAC_stats.log and nrL1_stats.log when
the written output reduces by truncating the files
- avoid to schedule retransmission with 0 RBs.
The gNB will stop the periodical logging of UEs in MAC Info level after
a configurable number of UEs have been printed, by default 8.
Set it to 17 in some CI tests to ensure we still get all UEs for the
time being, as the CI might depend on this.
Refactor SDAP adaptation work for QoS
This MR is an adaptation of the code introduced in !2703.
The goal is a cleanup and functional refactor of the SDAP/PDCP
integration, that is:
- centralize SDAP configuration logic
- simplify entity creation
- improve robustness of role-based SDAP handling
- prepare the codebase for clean support of DRB reconfiguration and
teardown flows
More concretely:
1. New sdap_config_t and get_sdap_Config()
- Introduced an internal struct sdap_config_t to abstract SDAP config
input
- Centralized SDAP config parsing into new get_sdap_Config() function
that translates ASN.1 NR_SDAP_Config into this internal
representation. This is called during RRC triggered
(re)configuration procedures.
- Enable mapping of number of QoS flows > 1
2. Unified role handling with bitmasks
- Added a bitmask-based entity_role field to track SDAP directions:
SDAP_UL_RX, SDAP_UL_TX, SDAP_DL_RX, SDAP_DL_TX: header presence was
determined by simple direction (UE vs gNB) and individual
is_sdap_rx/tx() checks, however nr_sdap_rx_entity behaves
differently depending on the direction of the RX entity (DL/UL),
therefore this change can help enable a more accurate SDAP header
handling across directions and node types.
- Replaces old helpers is_sdap_rx() / is_sdap_tx() with internal
checks against the role bitfield
- QFI-to-DRB mapping is now annotated with direction for both data and
control PDUs
3. Simplified DRB and SDAP setup
- add_drb() in PDCP API now delegates SDAP config processing cleanly
- new_nr_sdap_entity() is used consistently to register a fresh SDAP
context for the UE and PDU session.
- Also, re-use and reconfigure existing SDAP entity if already
exists.
- logging has been added to trace mapped QFIs from RRC and resulting
table entries
4. Improved QFI-to-DRB management
- Refactored nr_sdap_qfi2drb_map_update() to register QFIs based on
parsed config
- Ensures control PDUs are correctly routed even after reconfiguration
- Extended nr_sdap_ue_qfi2drb_config: perform UL QoS flow to DRB
mapping configuration for a SDAP entity has already been established
according to TS 37.324, 5.3 QoS flow to DRB Mapping, 5.3.1
Configuration Procedures. Handle both UL QoS Flows mapping rules to
add and to remove. QFIs will now be properly unmapped if specified
via mappedQoS_FlowsToRelease, this might prevent stale QFI mappings
from being used incorrectly.
- nr_sdap_qfi2drb() and sdap_map_ctrl_pdu() now strictly fallback to
default_drb only if a QFI mapping is missing. Missing default DRB
now triggers LOG_E() (previously silent or misrouted to DRB 0).
5. Other cleanup
- Remove dependencies from legacy rb_id_t
* use get_sdap_Config to process sdap_Config
* move SDAP config logic to the scope where it is relevant
* add SDAP entity direcly in RRC, not from PDCP
* replaced nr_pdcp_add_drbs with single add_drb call: it was no longer
efficient to keep it in the new logic. The addMod list can be looped directly in RRC.
* add specific function to add bearers from addMod list in E1, NSA, and UE
CI: Upgrade Aerial setup to 25-2.1
The purpose of this MR is to upgrade the cuBB image in the Aerial setup to
release 25-2.1 and update the doc/Aerial_FAPI_Split_Tutorial.md accordingly.
CI: Upgrade HO setup to use an attenuator
The goal of this MR is to upgrade HO CI setup to include a digital attenuator
that will allow us to trigger handover by attenuating the signals on the DUs.
Remove NR L2 simulator code from UE
This MR removes NR (SA and NSA) L2 simulator from the codebase. The code, at
least at the UE side, was done at a time where there was no clear L2/L1 split
leading to a complex implementation that never worked as expected. The L2
simulator has been broken and removed from testing for long time and, once it
needs to be revived, it would require a complete new implementation.
- Move 'What is a gNB neighbor?' explanation from rrc-usage.md to handover-tutorial.md where it belongs
- Replace generic parameter names with actual configuration parameter names and specific descriptions (e.g. gNB_ID, nr_cellid)
- Add example configuration structure showing proper syntax
- Add missing 'band' parameter that was not listed before
- Provide concrete examples and exact constraints for each parameter
- Cross-reference between documents for better organization
This addresses documentation issues where generic parameter descriptions were
not useful for developers configuring neighbor cells.
N2 handover
This MR introduces full support for N2 handover, covering handover
decision, preparation, execution, and notification between source and
target NG-RAN nodes.
Key features:
1. Handover Decision & Preparation:
- Implement N2 handover decision based on UE measurement reports.
- Generate the Handover Preparation Information message, including
RRCReconfiguration.
- Send Handover Required message from the source NG-RAN to the AMF.
2. Handover Execution:
- Decode and handle the Handover Request on the target NG-RAN.
- Process the Handover Command on the source gNB, triggering
RRCReconfiguration.
- Initiate Handover Notify after successful completion.
3 NGAP & RRC Enhancements:
- Implement NGAP encoding/decoding functions for Handover Required,
Handover Request, Handover Command, Handover Failure, and Handover
Notify (3GPP TS 38.413).
- Adds NG-RAN Status Transfer support (UL/DL) for PDCP COUNT
preservation during mobility:
- support for NGAP Uplink and Downlink RAN Status Transfer messages
(TS 38.413 §9.2.3.13-14) to enable proper PDCP COUNT value
transfer during handover or recovery: NGAP encoding/decoding for
RAN Status Transfer, PDCP helpers to extract and apply COUNT (HFN
+ SN) per DRB. This aligns with TS 38.300 §9.2.3.2.1 and TS 23.502
§4.9.1.3.3, ensuring PDCP status preservation in AM.
4. Testing:
- Introduce a Telnet command to manually trigger N2 handover using UE
ID and neighbor PCI.
- Add configuration file for testing N2 handover with a target gNB.
CI: build images on Jetson (armv8)
Add a new build pipeline for NVIDIA Jetson (armv8). Images have tag
prefix armv8_ to distinguish from gracehopper-built images prefixed arm_
(should have maybe been better with armv9_?)
Robert Schmidt