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doc: update FEATURE_SET.md, 5Gnas.md, rrc-dev.md

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- added Paging documentation
- updated to latest NGAP, F1AP, E1AP, NAS status
- fixed spelling errors

Signed-off-by: Guido Casati <guido.casati@openairinterface.org>
This commit is contained in:
Guido Casati
2026-05-27 18:16:59 +02:00
parent 294599d327
commit 5d309b93d1
3 changed files with 144 additions and 9 deletions
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13
doc/5Gnas.md
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@@ -17,7 +17,7 @@ Key 5GS NAS messages:
## OAI Implementation Status
The following tables lists implemented NAS messages and whether there is an encoder or decoder function, and if a corresponding unit test exists.
The following table lists implemented NAS messages and whether there is an encoder or decoder function, and if a corresponding unit test exists.
| Type | Message | Encoding | Decoding | Unit test |
|-------|-------------------------------------------|----------|----------|------------|
@@ -28,6 +28,9 @@ The following tables lists implemented NAS messages and whether there is an enco
| 5GMM | Identity Response | yes | no | no |
| 5GMM | Security Mode Complete | yes | no | no |
| 5GMM | Uplink NAS Transport | yes | no | no |
| 5GMM | Authentication Failure | yes | yes | yes |
| 5GMM | Authentication Reject | yes | yes | yes |
| 5GMM | Security Mode Reject | yes | yes | yes |
| 5GMM | Registration Request | yes | yes | no |
| 5GMM | Registration Accept | yes | yes | yes |
| 5GMM | Registration Complete | yes | yes | no |
@@ -45,10 +48,14 @@ The following tables lists implemented NAS messages and whether there is an enco
[openair3/NAS/NR_UE/5GS/fgs_nas_lib.c](../openair3/NAS/NR_UE/5GS/fgs_nas_lib.c):
* top-level encode/decode dispatch for NAS 5GMM/5GSM payloads
* delegates message-specific encoding/decoding to `5GMM/MSG` and `5GSM/MSG`
[openair3/NAS/NR_UE/5GS/NR_NAS_defs.h](../openair3/NAS/NR_UE/5GS/NR_NAS_defs.h):
* encoding and decoding functions for 5G NAS message headers and payloads
* relies on 5GMM/5GSM messages libs for payload encoding
* 5GS NAS message types and security header definitions
* shared NAS structures used by UE NAS handlers and encoders
* prototypes for 5GMM header and security-header encode/decode, implementations in `fgs_nas_lib.c`
[openair3/NAS/NR_UE/5GS/fgs_nas_utils.h](../openair3/NAS/NR_UE/5GS/fgs_nas_utils.h):

30
doc/FEATURE_SET.md
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@@ -145,6 +145,11 @@ These modes of operation are supported:
- evalution of RSRP report
- evaluation of CQI report
- MAC scheduling of SR reception
- Paging (PCCH/P-RNTI)
- CN paging records queued
- PF/PO dequeue from SIB1 PCCH-Config
- PCCH encoded at the UE's PO
- Type2 common search-space based P-RNTI PDCCH + PDSCH scheduling for PCCH
- Intra-frequency handover
- Inter-frequency handover
- Measurement gaps are automatically computed at the DU if the CU has neighbor information and the configured
@@ -230,9 +235,12 @@ These modes of operation are supported:
- NGAP Initial UE message
- NGAP Initial context setup request/response
- NGAP Downlink/Uplink NAS transfer
- NGAP UE context release request/complete
- NGAP Paging
- NGAP UE context release request/command/complete
- NGAP UE radio capability info indication
- NGAP PDU session resource setup request/response
- NGAP PDU session resource modify request/response
- NGAP PDU session resource release command/response
- NGAP Mobility Management Procedures:
* NGAP Handover Required
* NGAP Handover Request
@@ -259,6 +267,7 @@ These modes of operation are supported:
* F1 UE Context modification request/response
* F1 UE Context modification required
* F1 UE Context release req/cmd/complete
- F1 Paging
- F1 gNB CU configuration update
- F1 gNB DU configuration update
- F1 Reset (handled at DU only, full reset only)
@@ -279,10 +288,14 @@ These modes of operation are supported:
- E1 Bearer Context Setup (gNB-CU-CP initiated)
- E1 Bearer Context Setup Request
- E1 Bearer Context Setup Response
- E1 Bearer Context Setup Failure
- Bearer Context Modification (gNB-CU-CP initiated)
- E1 Bearer Context Modification Request
- E1 Bearer Context Modification Response
- E1 Reset
- E1 Bearer Context Modification Failure
- Bearer Context Release (gNB-CU-CP initiated)
- E1 Bearer Context Release Command
- E1 Bearer Context Release Complete
- Interface with RRC and PDCP/SDAP
- One CU-CP can handle multiple CU-UPs
@@ -356,9 +369,9 @@ These modes of operation are supported:
* NR-PRACH
- Formats 0,1,2,3, A1-A3, B1-B3
* NTN
- TA adjustemt based on ntn-Config-r17 information
- Different TA adjustemt algorithms between SIB19 receptions:
- Autonomous TA adjustemt based on DL time tracking
- TA adjustment based on ntn-Config-r17 information
- Different TA adjustment algorithms between SIB19 receptions:
- Autonomous TA adjustment based on DL time tracking
- Standard compliant epoch time based TA adjustment including orbital propagation
- DL Doppler compensation based on ntn-Config-r17 information
- UL Doppler pre-compensation based on ntn-Config-r17 information and residual DL FO estimation
@@ -395,9 +408,12 @@ These modes of operation are supported:
- Fallback not supported
* DCI processing
- format 10 (RA-RNTI, C-RNTI, SI-RNTI, TC-RNTI)
- format 10 with P-RNTI
- format 00 (C-RNTI, TC-RNTI)
- format 11 (C-RNTI)
- format 01 (C-RNTI)
* Paging monitoring and reception
- PF/PO-based paging PDCCH monitoring in IDLE/non-connected states
* UCI processing
- ACK/NACK processing
- Scheduling request procedures
@@ -462,6 +478,7 @@ These modes of operation are supported:
- Support for master cell group configuration
- Reception of UECapabilityEnquiry, encoding and transmission of UECapability
- Support for measurement report of Event A2/A3
- Paging: PCCH reception
* NTN according to 38.331 Rel.17
- Reception of ntn-Config-r17 from SIB19 or reconfigurationWithSync
- Handling of ntn-UlSyncValidityDuration-r17 in SIB19
@@ -472,7 +489,8 @@ These modes of operation are supported:
* Transfer of NAS messages between the AMF and the UE supporting the UE registration with the core network and the PDU session establishment according to 24.501 Rel.16
* 5GMM (5G Mobility Management) messages:
- Service Request/Accept/Reject (enc/dec library only)
- Service Request/Accept/Reject (Network-triggered Service Request TS 23.502 §4.2.3.3,
UE-Triggered Service Request after paging, TS 23.502 §4.2.3.2)
- Identity Request/Response
- Authentication Request/Response
- Security Mode Command/Complete

110
doc/RRC/rrc-dev.md
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@@ -626,6 +626,116 @@ sequenceDiagram
Note over ue,tdu: UE active on target DU
```
### Paging and Network Triggered Service Request (CM-IDLE to CM-CONNECTED)
The following flow documents the current OAI stack path for paging-triggered
service resumption in SA: context release to idle, NGAP/F1AP/PCCH paging, then
RRC setup with NAS Service Request.
End-to-end flow is split across these 3GPP procedures:
| Spec clause | Procedure name | Actor | Spec role in this flow |
|-------------|----------------|-------|------------------------|
| TS 23.502 §4.2.3.3 | Network Triggered Service Request | AMF / 5GC | Network must deliver MT signalling/data to a CM-IDLE UE. "The Paging Request triggers the UE Triggered Service Request procedure in the UE". Step 4b = Paging Request to RAN, step 6 = UE initiates §4.2.3.2 |
| TS 23.502 §4.2.3.2 | UE Triggered Service Request | UE | CM-IDLE UE may initiate SR "as a response to a network paging request" |
| TS 24.501 §5.6.2.2 | Paging for 5GS services | UE NAS | On paging indication from lower layers: initiate service request (§5.6.1.2) when in `5GMM-REGISTERED` and `5GMM-IDLE` |
| TS 24.501 §8.2.16 | SERVICE REQUEST | UE NAS | NAS PDU sent by UE |
#### OAI implementation
In summary:
- UE transitions to `RRC_IDLE` and AMF transitions UE to `CM-IDLE`
- CN-triggered paging is performed with `5G-S-TMSI` (NGAP Paging -> RRC Paging)
- One radio page per cell per NGAP PAGING at UE PO
- UE resumes via NAS Service Request and `RRCSetup`/`RRCSetupComplete`
- AMF continues §4.2.3.3 after Initial UE Message / context setup
```mermaid
sequenceDiagram
participant dn as DN
participant cn as 5GC
participant cu as gNB-CU
participant du as gNB-DU
participant ue as UE
cu->>cn: NGAP UE Context Release Request
Note over cu: example trigger: telnet `rrc ctx_rel_req`
cu->>cu: rrc_gNB_trigger_ue_context_release_req()
cu->>cu: rrc_gNB_send_NGAP_UE_CONTEXT_RELEASE_REQ()
cn->>cu: NGAP UE Context Release Command
cu->>cu: rrc_gNB_process_NGAP_UE_CONTEXT_RELEASE_COMMAND()
cu->>cu: rrc_gNB_generate_RRCRelease()
cu->>du: F1AP DL RRC Message Transfer (RRCRelease)
du->>ue: RRCRelease
ue->>ue: handle_RRCRelease()
ue->>ue: nr_rrc_going_to_IDLE()
Note over ue: RRC_IDLE, NAS remains REGISTERED and can request service
du->>cu: F1AP UE Context Release Complete
cu->>cn: NGAP UE Context Release Complete
Note over dn,ue: Trigger Paging
dn->>cn: DL user data
Note over cn: AMF paging decision [23.502 §4.2.3.3]
cn->>cu: NGAP Paging (5G-S-TMSI)
cu->>cu: ngap_gNB_handle_paging()
cu->>cu: decode_ng_paging()
cu->>cu: rrc_gNB_process_PAGING_IND()
cu->>cu: rrc_send_paging_to_dus()
cu->>du: F1AP Paging
du->>du: DU_handle_Paging()
du->>du: f1_paging()
du->>du: nr_mac_pcch_enqueue()
Note over du: at UE PO: schedule_nr_pcch()
du->>du: do_NR_Paging()
du->>ue: RRC Paging (ng-5G-S-TMSI, P-RNTI)
ue->>ue: nr_rrc_ue_decode_pcch()
ue->>ue: NAS_PAGING_IND
ue->>ue: generateServiceRequest()
ue->>ue: send_nas_initial_ul_transfer_req()
Note over ue: paging match triggers Service Request [24.501 §5.6.2]
Note over ue,cn: Resume service
ue->>ue: NAS_INITIAL_UL_TRANSFER_REQ
ue->>ue: nr_rrc_ue_prepare_RRCSetupRequest()
ue->>ue: nr_rrc_trigger_mac_ra(NR_MAC_RA_START_SETUP)
ue->>du: RRCSetupRequest
du->>cu: F1AP Initial UL RRC Message Transfer (RRCSetupRequest)
cu->>cu: rrc_handle_RRCSetupRequest()
cu->>du: F1AP DL RRC Message Transfer (RRCSetup)
du->>ue: RRCSetup
ue->>ue: do_RRCSetupComplete()
Note over ue: uses dedicatedNAS when no SRB exists
ue->>du: RRCSetupComplete + NAS SERVICE REQUEST
du->>cu: F1AP UL RRC Message Transfer (RRCSetupComplete + NAS)
cu->>cu: rrc_handle_RRCSetupComplete()
cu->>cn: NGAP Initial UE Message
cn->>cu: NGAP Initial Context Setup Request
cu->>cu: rrc_gNB_process_NGAP_INITIAL_CONTEXT_SETUP_REQ()
cu->>du: F1AP DL RRC Message Transfer (RRCReconfiguration)
du->>ue: RRCReconfiguration
ue->>du: RRCReconfigurationComplete
du->>cu: F1AP UL RRC Message Transfer (RRCReconfigurationComplete)
cu->>cu: handle_rrcReconfigurationComplete()
cu->>cn: NGAP Initial Context Setup Response
cn->>ue: DL user data
```
In OAI RFsim lab runs, a practical trigger sequence is:
1. `rrc ctx_rel_req <ue-id>` at gNB telnet
2. wait until AMF reports UE in IDLE state
3. send host-side traffic to UE IP
Relevant specs:
- TS 23.502: §4.2.3.3 Network Triggered Service Request (AMF pages, step 4b),
UE Triggered Service Request §4.2.3.2 (by network paging)
- TS 24.501 §5.6.2.2: Paging for 5G services
- TS 24.501 §5.6.1: Service Request procedure
- TS 38.331 §5.3.2: Paging
- TS 38.331 §5.3.11: UE actions upon going to RRC_IDLE
- TS 38.413 §8.5: Paging procedures (NGAP Paging)
- TS 38.473 §8.7: Paging procedures (F1AP CU-to-DU paging)
## Structures
### DUs and Cells