Abstract: A wireless communication network handles Session Management Function (SMF) outage in a Tracking Area (TA). An external SMF that is outside the TA registers with an internal Network Repository Function (NRF) that is inside in the TA. The internal NRF detects the SMF outage for an internal SMF inside the TA. The internal NRF receives an SMF request from an internal Access and Mobility Management Function (AMF) inside the TA. In response to the SMF outage, the internal NRF transfers an SMF response to the internal AMF that indicates the external SMF. The external SMF receives network signaling from the internal AMF and responsively directs an external User Plane Function (UPF) that is outside the TA to exchange user data with internal wireless access nodes that are inside the TA.

Abstract: In a cellular system having both 4th-Generation (4G) and 5th-Generation (5G) cellular networks, cellular device sends a Session Initiation Protocol (SIP) INVITE message to initiate a voice call. The message is received and acted upon by a Proxy-Call Session Control Function (P-CSCF) of an IP Multimedia Subsystem (IMS). Cellular devices that support 5G services are configured to include an information element (IE) in the SIP INVITE message to indicate support for 5G services. When responding to a SIP INVITE message, the P-CSCF determines whether the SIP INVITE message includes such an IE. If the SIP INVITE message contains an IE indicating 5G support, the P-CSCF sends an Authorization Authentication Request (AAR) message to a 5G Policy Control Function (PCF) to initiate a 5G dedicated bearer. Otherwise, the P-CSCF sends the AAR to a 4G Policy and Charging Rules Function (PCRF) to initiate a 4G dedicated bearer.

Abstract: In a cellular system having both 4th-Generation (4G) and 5th-Generation (5G) cellular networks, cellular device sends a Session Initiation Protocol (SIP) INVITE message to initiate a voice call. The message is received and acted upon by a Proxy-Call Session Control Function (P-CSCF) of an IP Multimedia Subsystem (IMS). Cellular devices that support 5G services are configured to include an information element (IE) in the SIP INVITE message to indicate support for 5G services. When responding to a SIP INVITE message, the P-CSCF determines whether the SIP INVITE message includes such an IE. If the SIP INVITE message contains an IE indicating 5G support, the P-CSCF sends an Authorization Authentication Request (AAR) message to a 5G Policy Control Function (PCF) to initiate a 5G dedicated bearer. Otherwise, the P-CSCF sends the AAR to a 4G Policy and Charging Rules Function (PCRF) to initiate a 4G dedicated bearer.

Abstract: A solution for initiating a network session (e.g., a voice call) for a user equipment (UE) on a network includes: receiving a session initiation message at a first network node; appending, to the session initiation message, an identification of a policy node; passing the appended session initiation message to a session management node; selecting, by the session management node, the identified policy node; and based at least upon selecting the identified policy node, initiating the network session for the UE. This improves call setup reliability by reducing the risk that an error in the subscriber information at the session management node (e.g., proxy-call session control function (P-CSCF)) indicates the incorrect policy node (e.g., policy and charging rule function (PCRF) or policy charging function (PCF)). In some examples, the session initiation message may comprise a session initiation protocol (SIP) message.