.. SPDX-License-Identifier: CC-BY-4.0
+O-DU High Overview
+*********************
+
O-DU High Architecture
======================
-
O-DU implements the functional blocks of L2 layer of a 5G NR protocol stack in SA(StandAlone) mode.
These layers primarily include NR MAC, NR Scheduler and NR RLC layers.
- Thread 1: O-DU thread
-- Thread 2: DU APP inclusive of Config Handler, DU Manager, UE Manager, EGTP Handler and ASN.1 Codecs
+- Thread 2: DU APP inclusive of Config Handler, DU Manager, UE Manager, and ASN.1 Codecs
- Thread 3: 5G NR RLC DL and MAC (inclusive of 5G NR SCH and Lower MAC)
- Thread 6: Lower MAC Handler
+- Thread 7: EGTP Handler
+
+- Thread 8: O1
O-DU High Modules
--------------------------
These modules contain platform specific files and support O-DU High functionality and message exchanges.
+O1 Module
+^^^^^^^^^^
+
+.. figure:: ODU-O1-Arch.jpg
+ :width: 554
+ :alt: Figure 2 O1 Architecture
+
+ Figure 2 - O1 Architecture
+
+As shown in figure 2 the O1 module runs as a thread in O-DU High. Alarm communication happens over a Unix socket between the O1 and O-DU threads. O1 module uses API calls for interacting with the Netconf server(Netopeer) and datastore(sysrepo) for providing the Netconf interface.
+
+O1 architecture has following components:
+
+- Netconf Session Handler: Subscribe to Netconf YANG modules and events. Register callback handler methods.
+
+- VES Agent : Sends the VES events to SMO
+
+- Alarm Manager: Stores and manages(add/updated/delete) alarms.
+
+- Alarm Interface : Provides an interface to O-DU High threads for sending the alarm messages to O1 module over Unix socket.
+
+- Config Interface : Interface to handle the configurations sent from SMO to the stack
+
+- Netopeer server: Serves the northbound SMO/OAM Netconf requests.
+
+
O-DU-High Interfaces
======================
:width: 600
:alt: O-DU High Interfaces
- Figure 2 - O-DU High Interfaces
+ Figure 3 - O-DU High Interfaces
-As shown in Figure 2, O-DU High interfaces with the following modules:
+As shown in Figure 3, O-DU High interfaces with the following modules:
- O-CU: O-DU High communicates with O-CU on the F1AP interface. The control message exchanges are on F1-C while
data message exchanges are on F1-U interfaces. The below F1AP messages on F1-C are implemented, as per
- UE Context Setup
+ - UE Context Modification
+
+ - UE Context Release
+
- RRC Message Transfer
- Initial UL RRC Message Transfer
:width: 720
:alt: Cell Up and Broadcast Procedure
- Figure 3 - O-DU High Cell Up and Broadcast Procedure
+ Figure 4 - O-DU High Cell Up and Broadcast Procedure
-As seen in the Figure 3,
+As seen in the Figure 4,
- The DU APP module of O-DU High sends F1 Setup Request to O-CU. This message contains a list of cells that the O-DU High has been configured with.
- The O-CU responds with F1 Setup Response. This message contains a list of cells which must be activated.
- RRC Reconfiguration Complete
-Figure 4 below depicts the above call flow, inclusive of all interfaces:
+Figure 5 below depicts the above call flow, inclusive of all interfaces:
.. figure:: UeAttach.png
:width: 800
:alt: O-DU High UE Attach Flow
- Figure 4 - UE Attach Flow
+ Figure 5 - UE Attach Flow
+
+- UE Release Signalling flow
+
+ - RRC Release
+
+Closed Loop Automation Procedure
+-----------------------------------
+
+This section describes the closed loop automation procedure within O-DU High.
+
+.. figure:: CLA_call_flow.png
+ :width: 720
+ :alt: Closed Loop Automation Procedure
+
+ Figure 6 - O-DU High Closed Loop Automation Procedure
+
+
+1. SMO commands ODU-High to bring the cell down via O1 interface.
+
+2. DU-APP module of ODU-High sends GNB-DU configuration update message to O-CU. It contains the details of cell to be deleted. O-CU acknowledges this message by sending GNB-DU configuration update acknowledgment.
+
+3. For each UE, DU APP sends UE Context Release Request to O-CU with information about the to be released. O-CU responds with UE Context Release request. It contains the RRC release message. O-DU high sends this RRC Release message to UE.
+
+4. DU APP then sends UE delete request to MAC and RLC. Once a confirmation is received from both MAC and RLC, DU APP deletes UE from its own database as well.
+
+4. Once all UEs are released, O-DU High sends STOP.Request to L1. L1 responds with stop indication.
+
+5. Once cell has stopped, DU APP sends cell delete request to MAC. On receiving confimation from MAC, DU APP deletes cell information from its own database as well and sends UE Context Release Complete.
+
+6. On receiving cell bring up command from SMO, the complete Cell bring up and UE attach procedure will be repeated (as explained in above sections)
+
+
+O1 Netconf get-alarm list procedure
+-----------------------------------
+
+This section describes the *Health Status Retrieval* scenario of O-DU High health-check. It enables a northbound client(SMO) to retrieve the health of the O-DU High based on the last self-check performed. The alarm-list is provided as the response to the request via O1 Netconf interface.
+
+
+.. figure:: ODU-O1-GetAlarmListFlow.jpg
+ :width: 869
+ :alt: Figure 6 O1 get alarm-list flow
+
+ Figure 7 - O1 get alarm-list flow
+
+As seen in the Figure 7,
+
+- On the cell state change from de-active to activate, DU APP module raises a cell up alarm message and sends it over the Unix socket using the Alarm Interface API.
+
+- On other side a Unix socket server, running as a thread, in O1 module receives the cell up alarm message and it passes on the alarm information to the Alarm Manager.
+
+- Alarm Manager stores the alarm data in a list.
+- Whenever SMO/OAM requires the current alarm list, it sends a Netconf get request. The request is received by the Netopeer Server and a callback method, registered with the Session Handler, is invoked.
+- The callback function fetches the alarm list from Alarm Manager and sends it back to the client (SMO/OAM) via Netconf interface.
OSC Testcases Supported
=========================
Code Review / o-du / l2.git / blobdiff