Guido Casati
806a15da01
This commit implements transparent forwarding of CellGroupConfig
as required by TS 38.473, eliminating CU-side decode/re-encode
cycles that violate transparency requirements.
Main Design Change:
- Before: CU decoded CellGroupConfig from DU, stored in the UE
context then re-encoded when sending to UE. CU constructed
new CellGroupConfig after RRCReestablishmentComplete.
- After: CU requests CellGroupConfig from DU via UE Context Modification
Request with `gNB_DU_Configuration_Query=true`, DU sends CellGroupConfig
which CU stores as encoded `byte_array_t` and forwards transparently
via reconfiguration without decode/re-encode cycles
To this purpose, all decode operations of CellGroupConfig were removed
from DU and all encode operations were removed from the CU.
Key Changes:
CU:
- Replace NR_CellGroupConfig_t* masterCellGroup with byte_array_t mcg in
gNB_RRC_UE_t for storing encoded CellGroupConfig
- Rename cell_group_config to cgc in nr_rrc_reconfig_param_t for brevity
- Implement transparent forwarding in build_RRCReconfiguration_IEs()
- Add helper functions:
- `store_cgc()` to store encoded bytes
- `get_meas_gap_config()`: Decode MeasGapConfig from DU to CU response
- `rrc_detect_reestablishment()` to detect re-establishment by decoding
temporarily (only for detection)
- Remove legacy decode/re-encode paths in RRC message generation
- Update all CellGroupConfig storage to use encoded bytes
- Update reconfiguration generation to accept is_reestablishment parameter
DU:
- Add `get_cellgroup_config()` to select source (CellGroup vs reconfigCellGroup)
based on re-establishment state
- Add re-establishment detection logic in `ue_context_modification_request()`
- Add `update_cellgroup_for_reestablishment()` to set reestablishRLC flags and
remove SRB1 from bearer list
- When `gNB_DU_Configuration_Query` is present and re-establishment detected:
- Clones from reconfigCellGroup (which contains spCellConfig) instead of
CellGroup (where spCellConfig was removed)
- Sets `reestablishRLC` flags for all bearers except SRB1
- Removes SRB1 from bearer list (already re-established)
Data Structure Changes:
- gNB_RRC_UE_t: Add byte_array_t mcg field
- nr_rrc_reconfig_param_t: Change cell_group_config to cgc (byte_array_t*)
- Remove masterCellGroup field usage in favor of encoded mcg
New re-establishment flow:
1. UE sends RRCReestablishmentRequest
2. CU processes -> sends RRCReestablishment
3. CU sends RRCReestablishmentComplete
4. CU sends UE Context Modification Request to DU with `gNB_DU_Configuration_Query=true`
5. DU detects re-establishment (`UE->reestablish_rlc && UE->reconfigCellGroup != NULL`):
- Clones `UE->reconfigCellGroup` -> `new_CellGroup` (contains spCellConfig)
- Sets `reestablishRLC` flags for all bearers except SRB1
- Removes SRB1 from bearer list (already re-established)
- Encodes `new_CellGroup` and sends to CU
6. CU receives encoded CellGroupConfig -> stores in `UE->mcg` via `store_cgc()`
7. CU detects re-establishment via `rrc_detect_reestablishment()`
8. CU calls `rrc_gNB_generate_dedicatedRRCReconfiguration()` with `is_reestablishment=true`:
- Creates SRB/DRB lists with re-establishment flags
- Generates RRC Reconfiguration with transparent CellGroupConfig
- Sends to UE
Why spCellConfig must be added in the DU in case of re-establishment:
With transparent forwarding, CU requests CellGroupConfig from DU instead
of constructing it. During re-establishment, DU's runtime CellGroup has
spCellConfig = NULL (removed per TS 38.331 §5.3.7.2). However, for the
gNB_DU_Configuration_Query response, DU must provide a complete CellGroupConfig
including spCellConfig. Therefore, DU restores spCellConfig by encoding
reconfigCellGroup (with the original spCellConfig) in CellGroupConfig.
In the old design CU constructed CellGroupConfig itself in
`rrc_gNB_process_RRCReestablishmentComplete()` and used `spCellConfig`
from its stored `masterCellGroup`.
Closes #837
OpenAirInterface License
It is distributed under OAI Public License V1.1.
The license information is distributed under LICENSE file in the same directory.
Please see NOTICE file for third party software that is included in the sources.
Where to Start
- General overview of documentation
- The implemented features
- System Requirements for Using OAI Stack
- How to build
- How to run the modems
Not all information is available in a central place, and information for specific sub-systems might be available in the corresponding sub-directories. To find all READMEs, this command might be handy:
find . -iname "readme*"
RAN repository structure
The OpenAirInterface (OAI) software is composed of the following parts:
openairinterface5g
├── charts
├── ci-scripts : Meta-scripts used by the OSA CI process. Contains also configuration files used day-to-day by CI.
├── CMakeLists.txt : Top-level CMakeLists.txt for building
├── cmake_targets : Build utilities to compile (simulation, emulation and real-time platforms), and generated build files.
├── common : Some common OAI utilities, some other tools can be found at openair2/UTILS.
├── doc : Documentation
├── docker : Dockerfiles to build for Ubuntu and RHEL
├── executables : Top-level executable source files (gNB, eNB, ...)
├── maketags : Script to generate emacs tags.
├── nfapi : (n)FAPI code for MAC-PHY interface
├── openair1 : Layer 1 (3GPP LTE Rel-10/12 PHY, NR Rel-15 PHY)
├── openair2 : Layer 2 (3GPP LTE Rel-10 MAC/RLC/PDCP/RRC/X2AP, LTE Rel-14 M2AP, NR Rel-15+ MAC/RLC/PDCP/SDAP/RRC/X2AP/F1AP/E1AP), E2AP
├── openair3 : Layer 3 (3GPP LTE Rel-10 S1AP/GTP, NR Rel-15 NGAP/GTP)
├── openshift : OpenShift helm charts for some deployment options of OAI
├── radio : Drivers for various radios such as USRP, AW2S, RFsim, 7.2 FHI, ...
├── targets : Some configuration files; only historical relevance, and might be deleted in the future
└── tools : Tools for use by the developers/ci machines: code analysis and formatting
How to get support from the OAI Community
You can ask your question on the mailing lists.
Your email should contain below information:
- A clear subject in your email.
- For all the queries there should be [Query] in the subject of the email and for problems there should be [Problem].
- In case of a problem, add a small description.
- Do not share any photos unless you want to share a diagram.
- OAI gNB/DU/CU/CU-CP/CU-UP configuration file in
.confformat only. - Logs of OAI gNB/DU/CU/CU-CP/CU-UP in
.logor.txtformat only. - In case your question is related to performance, include a small description of the machine (Operating System, Kernel version, CPU, RAM and networking card) and diagram of your testing environment.
- Known/open issues are present on GitLab, so keep checking.
Always remember a structured email will help us understand your issues quickly.