>1 through 108-4. The low power nodes 106-1 through 106-4 can be small base stations (such as pico or femto base stations) or RRHs, or the like. Notably, while not illustrated, one or more of the small cells 108-1 through 108-4 may alternatively be provided by the base stations 102. The low power nodes 106-1 through 106-4 are generally referred to herein collectively as low power nodes 106 and individually as low power node 106. Likewise, the small cells 108-1 through 108-4 are generally referred to herein collectively as small cells 108 and individually as small cell 108. The cellular communications system 100 also includes a core network 110, which in the 5G System (5GS) is referred to as the 5GC. The base stations 102 (and optionally the low power nodes 106) are connected to the core network 110.

The base stations 102 and the low power nodes 106 provide service to wireless communication devices 112-1 through 112-5 in the corresponding cells 104 and 108. The wireless communication devices 112-1 through 112-5 are generally referred to herein collectively as wireless communication devices 112 and individually as wireless communication device 112. In the following description, the wireless communication devices 112 are oftentimes UEs, but the present disclosure is not limited thereto.

FIG. 2 illustrates a wireless communication system represented as a 5G network architecture composed of core Network Functions (NFs), where interaction between any two NFs is represented by a point-to-point reference point/interface. FIG. 2 can be viewed as one particular implementation of the system 100 of FIG. 1.

Seen from the access side the 5G network architecture shown in FIG. 2 comprises a plurality of UEs 112 connected to either a RAN 102 or an Access Network (AN) as well as an AMF 200. Typically, the R(AN) 102 comprises base stations, e.g., such as eNBs or gNBs or similar. Seen from the core network side, the 5GC NFs shown in FIG. 2 include a NSSF 202, an AUSF 204, a UDM 206, the AMF 200, a SMF 208, a PCF 210, and an Application Function (AF) 212.

Reference point representations of the 5G network architecture are used to develop detailed call flows in the normative standardization. The N1 reference point is defined to carry signaling between the UE 112 and AMF 200. The reference points for connecting between the AN 102 and AMF 200 and between the AN 102 and UPF 214 are defined as N2 and N3, respectively. There is a reference point, N11, between the AMF 200 and SMF 208, which implies that the SMF 208 is at least partly controlled by the AMF 200. N4 is used by the SMF 208 and UPF 214 so that the UPF 214 can be set using the control signal generated by the SMF 208, and the UPF 214 can report its state to the SMF 208. N9 is the reference point for the connection between different UPFs 214, and N14 is the reference point connecting between different AMFs 200, respectively. N15 and N7 are defined since the PCF 210 applies policy to the AMF 200 and SMF 208, respectively. N12 is required for the AMF 200 to perform authentication of the UE 112. N8 and N10 are defined because the subscription data of the UE 112 is required for the AMF 200 and SMF 208.

The 5GC network aims at separating UP and CP. The UP carries user traffic while the CP carries signaling in the network. In FIG. 2, the UPF 214 is in the UP and all other NFs, i.e., the AMF 200, SMF 208, PCF 210, AF 212, NSSF 202, AUSF 204, and UDM 206, are in the CP. Separating the UP and CP guarantees each plane resource to be scaled independently. It also allows UPFs to be deployed separately from CP functions in a distributed fashion. In this architecture, UPFs may be deployed very close to UEs to shorten the Round Trip Time (RTT) between UEs and data network for some applications requiring low latency.

The core 5G network architecture is composed of modularized functions. For example, the AMF 200 and SMF 208 are independent functions in the CP. Separated AMF 200 and SMF 208 allow independent evolution and scaling. Other CP functions like the PCF 210 and AUSF 204 can be separated as shown in FIG. 2. Modularized function design enables the 5GC network to support various services flexibly.

Each NF interacts with another NF directly. It is possible to use intermediate functions to route messages from one NF to another NF. In the CP, a set of interactions between two NFs is defined as service so that its reuse is possible. This service enables support for modularity. The UP supports interactions such as forwarding operations between different UPFs.

FIG. 3 illustrates a 5G network architecture using service-based interfaces between the NFs in the CP, instead of the point-to-point reference points/interfaces used in the 5G network architecture of FIG. 2. However, the NFs described above with reference to FIG. 2 correspond to the NFs shown in FIG. 3. The service(s) etc. that a NF provides to other authorized NFs can be exposed to the authorized NFs through the service-based interface. In FIG. 3 the service based interfaces are indicated by the letter “N” followed by the name of the NF, e.g. Namf for the service based interface of the AMF 200 and Nsmf for the service based interface of the SMF 208, etc. The NEF 300 and the NRF 302 in FIG. 3 are not shown in FIG. 2 discussed above. However, it should be clarified that all NFs depicted in FIG. 2 can interact with the NEF 300 and the NRF 302 of FIG. 3 as necessary, though not explicitly indicated in FIG. 2.

Some properties of the NFs shown in FIGS. 2 and 3 may be described in the following manner. The AMF 200 provides UE-based authentication, authorization, mobility management, etc. A UE 112 even using multiple access technologies is basically connected to a single AMF 200 because the AMF 200 is independent of the access technologies. The SMF 208 is responsible for session management and allocates Internet Protocol (IP) addresses to UEs. It also selects and controls the UPF 214 for data transfer. If a UE 112 has multiple sessions, different SMFs 208 may be allocated to each session to manage them individually and possibly provide different functionalities per session. The AF 212 provides information on the packet flow to the PCF 210 responsible for policy control in order to support QoS. Based on the information, the PCF 210 determines policies about mobility and session management to make the AMF 200 and SMF 208 operate properly. The AUSF 204 supports authentication function for UEs or similar and thus stores data for authentication of UEs or similar while the UDM 206 stores subscription data of the UE 112. The Data Network (DN), not part of the 5GC network, provides Internet access or operator services and similar.

An NF may be implemented either as a network element on a dedicated hardware, as a software instance running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, e.g., a cloud infrastructure.

FIG. 4 is a flowchart of an exemplary method performed by a network node, such as an SMF or a PGW-C, in a CN for handling a failure during traffic steering. In a non-limiting example, the network node can be an SMF or a Packet Data Network Gateway Control Plane (PGW-C). The network node receives traffic steering control information from a second network node (step 400). In a non-limiting example, the second network node can be a PCF or a Policy and Charging Rules Function (PCRF). The network node can detect an error during N6-LAN traffic steering, SGi-LAN traffic steering, AF influence traffic steering (step 402). In one embodiment, the network may detect the error by evaluating the received traffic steering control information (402-1). In another embodiment, the network node may request a UPF to implement a Packet Detection Rule (PDR) based on the received traffic steering control information (step 402-2a). The network node may receive an error code that indicates the UPF cannot enforce the PDR (step 402-2b). Accordingly, the network node may detect the error based on the error code received from the UPF (step 402-2c). Accordingly, the network node can report detected error to the second network node (step 404). In a non-limiting example, the network node can provide a failure report that includes a selected failure code to the PCF (step 404-1). The network node may receive updated traffic steering control information from the second network node (step 406).

FIG. 5 is a flowchart of an exemplary method performed by a PCF or PCRF in a CN for handling a failure during traffic steering. The PCF or PCRF provides traffic steering control information to an SMF or PGW-C (step 500). The PCF or PCRF receives a failure report from the SMF or PGW-C that indicates an error during N6-LAN traffic steering or SGi-LAN Traffic Steering, and/or AF influence traffic steering (step 502). The PCF or PCRF may receive the failure report that includes a selected failure code (step 502-1). Accordingly, the PCF or PCRF performs one or more actions in response to receiving the failure report (step 504). In a non-limiting example, the PCF or PCRF can provide updated traffic steering control information to the SMF or PWG-C (step 504-1).

FIG. 6 is a flowchart of an exemplary method performed by a UPF for handling a failure during traffic steering. The UPF receives a request from an SMF to implement a PDR based on traffic steering control information received by the SMF (step 600). The UPF can provide an error code to the SMF in response to the UPF being unable to enforce the PDR (step 602).

Specific embodiments of the present disclosure are now discussed. In an embodiment of the present disclosure, the following data types are to be added to Table 5.6.3.9-1: Enumeration FailureCode in Chapter 5.6.3.9 of 3GPP TS 29.512.

Enumeration

value
Description
Applicability

TRAFFIC_STEERING_ERROR
This value is used to indicate that:

the enforcement of the steering of traffic to

the N6-LAN or 5G-LAN failed; or

the dynamic PCC rule could not be

successfully installed/modified at the NF

service consumer because e.g., there is an

invalid traffic steering policy identifier(s)

within the provided Traffic Control Data

policy decision to which the PCC rule refers.

DNAI_STEERING_ERROR
This value is used to indicate that:

the enforcement of the steering of traffic to

the indicated DNAI failed; or

the dynamic PCC rule could not be

successfully installed/modified at the NF

service consumer because there is invalid

route information for a DNAI(s) (e.g.,

routing profile id is not configured) within

the provided Traffic Control Data policy

decision to which the PCC rule refers.

In an embodiment of the present disclosure, the following data types are to be added to Rule-Failure-Code AVP in Chapter 5.3.8 of 3GPP TS 29.212:

- TRAFFIC_STEERING_ERROR: This value is used to indicate that:
- the enforcement of the steering of traffic to the SGi-LAN;

FIG. 7 is a flowchart of an exemplary failure handling signaling according to an embodiment of the present disclosure.

Step 1: PCF provisions new or modifies existing policy decision with traffic steering control information (e.g., steps 400, 500).

Step 2: SMF validates PCF provisioned policy decision (e.g., step 402-1). SMF detects an error(s) during N6-LAN Traffic Steering and/or AF Influence Traffic Steering.

Step 3: SMF reports the error to PCF using SmPolicy_Update Request including error reports to indicate the error (e.g., steps 404, 502).

Step 4: PCF makes corresponding decision, and may provision updated new decision if applicable, based on the reported error (e.g., steps 406, 504-1).

FIG. 8 is a flowchart of an exemplary failure handling signaling according to another embodiment of the present disclosure.

Step 1: PCF provisions new or updates existing policy decision with traffic steering control information (e.g.,