depicts the optional deployment network structure of PWS architecture in 5GS with AMF to CBC inter-connection via PWS-IWF using the reference point representation showing how the network functions interact with each other. In this option the PWS-IWF implements functionality to transfer messages between N50 and SBc reference points, and vice versa.
The PWS architecture using PWS-IWF contains the following reference points:
Reference point between the NG-RAN and the AMF.
Reference point between the PWS-IWF and the CBC.
Reference point between the AMF and the PWS-IWF.
The CBE and the interface between CBE and CBC are out of scope of 3GPP specifications.
The present document describes logical functional entities, and how these are realized in actual deployments is an implementation and deployment issue. It can however be foreseen that the PWS-IWF functionality may be co-located with the AMF, with the CBC, or deployed as a stand-alone network function. At AMF/PWS-IWF co-location, the AMF/PWS-IWF entity interacts with the CBC via SBc. At CBC/PWS-IWF co-location, the CBC/PWS-IWF interacts with the AMF via N50. At stand-alone PWS-IWF, the PWS-IWF interacts with the AMFvia N50 and with the CBC via SBc.
A PWS-IWF co-located with AMF or a stand-alone PWS-IWF may interface to one CBC or multiple CBCs (i.e. the PWS-IWF is allowed to have SCTP transport associations established with one or multiple CBCs). A stand-alone PWS-IWF or a PWS-IWF co-located with the CBC may interface to several AMFs.
The PWS-IWF is a logical function which functionality is to translate from N50 to SBc.
If the Write-Replace-Warning-Indication and Stop-Warning-Indication or the Restart-Indication-E-UTRAN and Failure-Indication-E-UTRAN are supported on SBc then the PWS-IWF shall manage the subscriptions for the corresponding notifications that may be received over N50.
The PWS-IWF may interface to one or multiple AMFs. The PWS-IWF may interface to one or multiple CBCs. Exceptions from straightforward mapping by the PWS-IWF from SBc based messages and parameters to SBI based messages and parameters are described in the following clauses.
If the PWS-IWF receives a Write-Replace-Warning Request message from the CBC which contains the Extended Repetition-Period IE then the PWS-IWF shall map the Extended Repetition-Period IE onto the Repetition-Period NG-RAN IE in the Write-Replace-Warning Request message towards the AMF and shall ignore the Repetition-Period IE that is received from the CBC.