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The near-RT RIC (RIC for short) Self-Health-Check flows fulfill the requirement that all systems need to monitor their own health – internal subsystems, hosted software, and external interfaces. 

Internal Self-Check - At configurable intervals, the RIC is to trigger Health-Check requests to its internal common platform modules and hosted xAPPs. Platform modules and xAPPs are required to support Health-Check requests and to perform a self-check. 

Alarms and Notifications - Based on Health-Check results, the RIC is required to maintain a list of alarms which represents the state of the overall RIC health.  Alarm conditions are to be raised and sent as notifications.


Self-Check of Platform Modules and xAPPs

The RIC is responsible to check the health of RIC Platform modules and xAPP instances hosted on the RIC.  Specific requirements are as follows: 

  • Ability to internally initiate self-checks on each of the common platform modules within the RIC.  Examples of platform modules are: O1 Termination, A1 Mediator, E2 Termination, E2 Manager, xAPP Manager, Subscription Manager, etc.
  • Internal self-checks are to be done at default intervals.  Intervals are to be configurable during run-time.  
  • Each platform module is required to support health-check requests.  Initially, the modules may simply need to send a response message to indicate that the connectivity is still up and messaging pathway still operational.  (In later releases, additional diagnostics may be needed to ensure RIC lifecycle management is robust and carrier-grade.)  
  • Self-check results on platform modules are to be logged.

Implementation Option[1]: The self-check can potentially leverage Kubernetes Liveness and Readiness probes. Liveness probes can be configured to execute a command against the pod (and/or open TCP socket, issue http-get).   Readiness probes can be configured to ensure the pod is ready before allowing it handle traffic.  To further check a module’s (pod) ability to communicate with other modules over RMR (RIC Message Router), each module could subscribe to its own topic, send a hello-world message regularly to itself and ensure it can send and receive messages.

[1] Implementation options are suggested at the use case level, to be further refined/finalized during user stories phase.

Alarms, Clearings and Notifications

  • As anomaly conditions are encountered as part of the self-check process or during normal operation (e.g., cannot send message to another module/xApp via RMR), the RIC and/or the specific platform module/xAPP needs to determine the severity and whether they are mappable to an alarm type.  If mappable to an alarm type, the RIC needs to declare the alarm condition.  
  • The alarm type definitions for platform modules and xAPPs should be consistent with 3GPP TS 28.545 Fault Supervision technical specification.  
  • New alarms declared in either case (self-check or normal operation) require notifications to be sent immediately via the O1 VES interface, after verifying against the current RIC alarm list that the alarm is indeed new.
  • New alarms are to be stored and captured as part of the alarm list of the RIC.  To support queries from NB clients for outstanding alarms via O1 Netconf interface, the RIC needs to make the alarm list available in the yang operational tree.  The yang model may need to be updated to support the alarm queries.  
    • Since alarms are sent as VES events over O1 VES, a mapping or translation function between VES alarms and Netconf/Yang model might needed. 
  • Similarly, the RIC needs to identify alarms that are not longer present by comparing self-check results against the current alarm list.  Any cleared alarms need to be removed from the RIC alarm list and clearing notifications sent over O1 VES. 


To support this flow, a new Health-Check functional block within the RIC is being proposed, which can be implemented as a separate software module, as a distributed function across one or more existing modules, and/or as existing capabilities already available from the underlying container infrastructure such as Kubernetes' container/pod lifecycle management.  The Health-Check functional block has to perform the following:

  • Perform health-checks on the common RIC platform functions/modules and on xAPP instances hosted on the RIC (self-checks at configured intervals and on-demand requests)
  • Map failures and anomalies to alarms and alerts
  • Send out notifications for alarms and alerts
  • Determine the state of the RIC based on alarms and alerts
  • Store health-check results for queries
  • Clear alarms and alerts when conditions clear


Figure 1 below shows the flow of RIC Self-Checks – regular heartbeats over O1 and A1, the Health-Check Module initiating health-check requests within the RIC to assess its overall health, and issuing alarms/alerts, as appropriate based on health results.



Note 1: Figure 1 above shows the flows assuming that SMO is the northbound client that triggers the near-RT RIC.  The SMO consists of the O1 OAM adapter (supporting both O1VES and O1NetConf related messages/data) and the non-RT RIC (containing the A1 adapter).  The O-RAN SC implementation of the flows associated with this Health-check use case should create a simulated SMO for invoking requests and processing responses.  The simulated SMO should also provide a Test Driver (shown in Figures 2-4) for initiating requests to SMO and receive response from SMO.  Alternatively, a Dashboard can also be the NB client to trigger these requests.


External Interfaces

For health of external interfaces, the RIC is responsible to check its interface module health and the reachability/connectivity by external systems.  For RIC interface modules - O1 Termination, A1 Mediator, and E2 Termination modules - the requirement is already described above as part of the RIC Self-Check.  For connectivity, the RIC needs to support heartbeats or keep-alive signals to ensure northbound (SMO-RIC including other NB clients) and southbound connectivity (RIC-RAN Resources).  

  • SMO-RIC connectivity over O1 Netconf and O1 VES
  • SMO-RIC connectivity over A1
  • RIC-RAN Resources over E2

RIC connectivity resources 

The RIC also checks heartbeat message come from RAN resources over the E2 interface.

Note: Since the role of RIC is to enable near realtime control loop actions, latency is an important set of telemetry to be collected and reported - E2 latency and RIC processing latency.  As RIC matures release over release, latency telemetry should be defined and implemented.








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