Method for slice-specific overload control in wireless access networks

Abstract

A method for performing slice-specific overload control in a wireless communication system includes detecting slice-specific overload in a radio area network (RAN) based on a physical resource block (PRB) utilization threshold and a predetermined time period, wherein a specific RAN network slice is identified via network slice selection assistance information (S-NSSAI), mapping the slice to an access category in the RAN, and informing the RAN of an action to be taken to mitigate the detected slice-specific overload.

Description

[Technical Field]

[0001] In some embodiments, the subject matter herein relates generally to overload control in wireless communication systems, and more particularly to slice-specific overload control in radio access network (RAN) communication systems. [Background technology]

[0002] Under high network load conditions, networks can protect themselves from overload by using the Unified Access Control (UAC) function for 3GPP access to limit access attempts from user equipment (UE). Unified access control supports extensibility to allow the inclusion of additional standardized access identities and access categories, and flexibility to allow operators to define operator-defined access categories using their own criteria. One such criterion is network slicing, which is considered a key feature by 3GPP. Identification of a network slice is performed via a Single Network Slice Selection Assistance Information (S-NSSAI). The Network Slice Selection Assistance Information (NSSAI) contains multiple S-NSSAIs. A UE is configured to access multiple slices, and each slice may serve a specific service type agreed upon in a service level agreement (SLA) with the service provider. The definition of the operator-defined access category can be signaled to the UE using non-access stratum (NAS) signaling with the access category criteria type set to S-NSSAI. Summary of the Invention [Problem to be solved by the invention]

[0003] Currently, 3GPP specifies overload signaling from the core network to the radio access network to indicate the set of overloaded slices, but does not specify how the radio access network (RAN) should handle the overload condition or how the radio access network should map slice-specific overload to access categories in the unified access control (UAC) framework.

[0004] Therefore, there is a need for slice-specific overload control in the RAN that provides the ability to detect slice-specific overload "instances" in the RAN and alleviate slice-specific congestion by initiating access class policing through a 3GPP-specific UAC framework. There is also a need for mapping slices to access categories in the RAN. [Means for solving the problem]

[0005] In one general aspect, a method for performing slice-specific overload control in a wireless communication system is provided, the method including: detecting slice-specific overload in a radio area network (RAN) based on a physical resource block (PRB) utilization threshold and a predetermined time period, wherein a specific RAN network slice is identified via network slice selection assistance information (S-NSSAI), mapping the slice to an access category in the RAN, and informing the RAN of an action to take to mitigate the detected slice-specific overload.

[0006] In another general aspect, a wireless communication system is provided. The wireless communication system includes a core network, a radio access network (RAN), an access mobility function (AMF), and a near real-time RAN intelligent controller (near-RT RIC). The RAN includes a plurality of user equipments and a plurality of base stations (gNBs). Each of the plurality of gNBs includes at least one aggregation unit (CU) and one distribution unit (DU), and a gNB-CU control plane (gNB-CU-CP) is configured to trigger specific actions to mitigate detected slice-specific overload. At least one gNB-DU or near-RT RIC is configured to detect slice overload in the RAN based on a physical resource block (PRB) utilization threshold and a predetermined period of time, a specific RAN network slice is identified via network slice selection assistance information (S-NSSAI), mapping of the slice to an operator-specific category is performed by one of the AMF or near-RT RIC, the AMF or near-RT RIC sends the mapping information to the gNB-CU-CP, and the RAN is configured to take specific action to mitigate the detected slice-specific overload.

[0007] In another general aspect, a non-transitory computer-readable medium having stored thereon instructions for causing a processing circuit to execute a process including detecting slice-specific overload in a radio area network (RAN) based on a physical resource block (PRB) utilization threshold and a predetermined time period, wherein a particular RAN network slice is identified via network slice selection assistance information (S-NSSAI), mapping the slice to an access category in the RAN, and informing the RAN of an action to take to mitigate the detected slice-specific overload. [Brief explanation of the drawings]

[0008] In the following drawing:

[0009] FIG. 1 illustrates a message flow for slice-specific overload detection in a radio access network according to one embodiment;

[0010] FIG. 2 illustrates a process for slice-specific overload detection in a radio access network according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] As mentioned above, the standard specifies how to map slice identifiers (S-NSSAI) to access categories through NAS signaling (between the UE and the core network), but does not specify how the RAN obtains such mapping. Furthermore, the standard does not specify how a slice-specific congestion situation can be detected in the RAN or how a UAC can be autonomously initiated by the RAN to alleviate this situation. Embodiments of the present disclosure provide methods and systems for detecting slice-specific overload in a radio access network, alleviating slice-specific congestion by initiating access class policing through a 3GPP-specific unified access control (UAC) framework, and mapping slices to access categories in a radio access network.

[0012] In the RAN, the share of radio resources (physical resource blocks) to be used for a particular network slice (identified by the S-NSSAI) can be configured using the RRM policy ratios defined in 3GPP TS 28.541 section 4.3.36. This is used to determine the maximum PRB resources available for each slice in each cell. If PRB utilization is close to a threshold (e.g., 90-95%) of the maximum available resources for the slice and this utilization continues for a period of time (e.g., 15 minutes), the cell is identified as being in a persistent overload situation for the particular slice. Such an overload condition can be detected directly at the DU or in an xApp in the near-RT RIC through real-time streaming of cell-specific, S-NSSAI-specific PRB utilization to the near-RT RIC.

[0013] 1 illustrates a message flow between a UE 110, a gNB-DU 120, a gNB-CU-CP 130, and an AMF 140 for slice-specific overload detection in a RAN, according to one embodiment. At M1, the gNB-CU-CP 130 sends an NG Setup Request message to the AMF 140, and at M2, the AMF 140 responds with an AMF Setup Response message. The AMF Setup Response message includes an S-NSSAI slice support list that identifies a particular RAN network slice and further information mapping the slice to operator-specific access categories. When the network configuration changes, at M3, the AMF 140 sends an AMF Configuration Update message to the gNB-CU-CP 130. The AMF Configuration Update message includes the updated S-NSSAI slice support list and access category mapping information, and at M4, the gNB-CU-CP 130 responds with an AMF Configuration Update Confirmation.

[0014] At M5, the gNB-DU 120 sends an F1 Setup Request message to the gNB-CU-CP 130, and at M6, the gNB-CU-CP 130 responds with an F1 Setup Response message. The F1 Setup Response message includes an S-NSSAI that identifies a specific RAN network slice along with access category mapping information. When the network configuration changes, at M7, the gNB-CU-CP 130 sends a CU Configuration Update message to the gNB-DU 120. The CU Configuration Update message includes updated S-NSSAI access category mapping information, and at M8, the gNB-DU 120 responds with a CU Configuration Update Confirmation.

[0015] The gNB-DU detects slice-specific overload based on a slice-specific PRB resource sharing configuration and current PRB utilization in the cell. In one embodiment, a slice-specific overload condition occurs when utilization of the slice-specific PRB resources exceeds a threshold for a predetermined period of time. In one embodiment, the PRB utilization threshold is compared against a baseline configuration for slice-specific resources in the cell, where the baseline configuration is based on a radio resource management (RRM) policy ratio.

[0016] When overload is detected, the gNB-DU automatically determines the barring percentage depending on the percentage of access that should be barred to alleviate slice-specific congestion. In M9, the gNB-DU 120 transmits UAC barring information to the UE 110 in System Information Block 1 (SIB1), and the UE applies access barring for a specific slice depending on the operator access category to which access is barred.

[0017] 2 illustrates a process flow for slice-specific overload detection in the RAN (by xApp in a near-RT RIC) according to one embodiment. At P1, the near-RT RIC 230 obtains S-NSSAI-specific RRM policy configuration in the GNB-DU 220 through an E2 configuration update procedure or a RIC subscription request / RIC indication procedure. At P2, the near-RT RIC 230 sends a RIC subscription request to the gNB-DU 220. The RIC subscription request includes a report action request for physical resource block (PRB) activity measurements along with a measurement name (e.g., RRU.PrbUsedDI as defined in 3GPP TS 28.552 section 5.1.1.2.5), a measurement label (e.g., SNSSAI), and a reporting period. At P3, the gNB-DU 220 responds with a RIC subscription response. At P4, the near-RT RIC 230 sends another RIC subscription request to the gNB-DU 220. The RIC subscription request includes a report action request for data radio bearer (DRB) activity measurements, along with a measurement name (e.g., DRB.MeanActiveUeDI_Filter), a measurement label (e.g., SNSSAI), and a reporting period. At P5, the gNB-DU 220 responds with a RIC subscription response. At P6, the gNB-DU 220 collects the requested measurement results over the reporting period. At P7, the gNB-DU 220 sends a RIC indication to the near-RT RIC 230, along with the requested measurement reports (e.g., RUU.PrbUsedDI.SNSSAI) and (e.g., DRB.MeanActiveUeDI_Filter.SNSSAI). At P8, when the xApp in the near-RT RIC 230 detects slice overload using the reported measurement results along with some application-specific thresholds, the xApp triggers a RIC control procedure to apply slice-specific overload control procedures through the UAC.Similar to what was discussed above, a slice-specific overload condition occurs when the utilization of slice-specific PRB resources exceeds a threshold for a predetermined period of time. In one embodiment, the PRB utilization threshold is compared against a baseline configuration for slice-specific resources in the cell, where the baseline configuration is based on a radio resource management (RRM) policy ratio.

[0018] At P9, the near-RT RIC 230 sends a RIC control request to the gNB-CU-CP 240. The RIC control request includes at least the following parameters: S-NSSAI to operator-specific access category and access identity mapping, a list of cells, and a rate reduction percentage. At P10, the gNB-CU-CP 240 responds with a RIC control response. At P11, the gNB-CU-CP 240 sends an F1AP network access rate reduction message to the gNB-DU 220 indicating UAC reduction with UAC assistance information. At P12, the gNB-DU 220 sends SIB1 with UAC barring information to the UE 210. At P13, the UE 210 applies access restrictions for a specific slice depending on the operator access category to which access is barred.

[0019] As discussed above, in one general aspect, a method for performing slice-specific overload control in a wireless communication system is provided, the method including: detecting slice-specific overload in a radio area network (RAN) based on a physical resource block (PRB) utilization threshold and a predetermined time period, wherein a specific RAN network slice is identified via network slice selection assistance information (S-NSSAI); mapping the slice to an access category in the RAN; and informing the RAN of an action to be taken to mitigate the detected slice-specific overload.

[0020] Implementations of the method may include one or more of the following features. In one embodiment, a PRB utilization threshold is exceeded for a predetermined period of time, and the PRB utilization threshold is compared against a baseline configuration for slice-specific resources in the cell, the baseline configuration following a radio resource management (RRM) policy ratio. In one embodiment, the method further includes controlling a gNB aggregation unit control plane (gNB-CU-CP) to trigger specific actions to mitigate the detected slice-specific overload. In another embodiment, the mapping of slices to operator-specific access categories is performed by an Access Mobility Function (AMF), and the AMF sends the mapping information to the gNB-CU-CP. In another embodiment, the mapping information is transmitted via a Next Generation (NG) Setup Response message or an AMF Configuration Update message. The method further includes sending the mapping information from the gNB-CU-CP to the gNB-DU via an F1 Setup Response message or a CU Configuration Update message. In one embodiment, the detecting slice-specific overload is performed by an xApp running on a near-real-time RAN intelligent controller (near-RT RIC) that receives real-time streaming of cell-specific S-NSSAI-specific PRB utilization, and the near-RT RIC receives S-NSSAI-specific radio resource management (RRM) policy configuration in a gNB distributed unit (gNB-DU) via an E2 configuration update procedure or a RIC subscription request / RIC indication procedure. The method of one embodiment further includes reporting from the gNB-DU to the near-RT RIC by physical resource block (PRB) and data radio bearer (DRB) activity at a requested reporting period.In yet another embodiment of the method, the near-RT RIC sends a RIC control request to the gNB-CU-CP, where the RIC control request includes at least the following parameters: an S-NSSAI to operator-specific access category and access identity mapping, a list of cells, and a rate reduction percentage. In yet another embodiment of the method, the gNB-CU-CP triggers a network access rate reduction message to the gNB-DU, where the gNB-DU triggers unified access control (UAC) barring for one or more user equipments (UEs).

[0021] As noted above, in another general aspect, a wireless communication system is provided. The wireless communication system includes a core network, a radio access network (RAN), an access mobility function (AMF), and a near real-time RAN intelligent controller (near-RT RIC). The RAN includes a plurality of user equipments and a plurality of base stations (gNBs). Each of the plurality of gNBs includes at least one aggregation unit (CU) and one distribution unit (DU), and a gNB-CU control plane (gNB-CU-CP) is configured to trigger specific actions to mitigate detected slice-specific overload. At least one gNB-DU or near-RT RIC is configured to detect slice overload in the RAN based on a physical resource block (PRB) utilization threshold and a predetermined period of time, a specific RAN network slice is identified via network slice selection assistance information (S-NSSAI), mapping of the slice to an operator-specific category is performed by one of the AMF or near-RT RIC, the AMF or near-RT RIC sends the mapping information to the gNB-CU-CP, and the RAN is configured to take specific action to mitigate the detected slice-specific overload.

[0022] Implementations of the wireless communication system may include one or more of the following features. In one embodiment of the system, a PRB utilization threshold is exceeded for a predetermined period of time, and the PRB utilization threshold is compared against a baseline configuration for slice-specific resources in the cell, the baseline configuration following a radio resource management (RRM) policy ratio. Observing PRB utilization consistently above the threshold for the configured period of time is interpreted as indicating that the slice is overloaded. In a further embodiment, the detecting is performed by the gNB-DU, and the mapping information is sent by the AMF to the gNB-CU-CP via a Next Generation (NG) Setup Response message or an AMF Configuration Update message. In a further embodiment, the gNB-CU-CP is further configured to send the mapping information to the gNB-DU via an F1 Setup message or a CU Configuration Update message. In a further embodiment, detecting slice-specific overload is performed by an xApp running in a near-RT RIC that receives real-time streaming of cell-specific and S-NSSAI-specific PRB utilization, and the near-RT RIC receives S-NSSAI-specific RRM policy configuration in the gNB-DU via an E2 Configuration Update procedure or a RIC Subscription Request / RIC Indication procedure. In a further embodiment, the gNB-DU is configured to report physical resource block (PRB) and data radio bearer (DRB) activity to the near-RT RIC at a requested reporting period. In a further embodiment, the near-RT RIC sends a RIC control request to the gNB-CU-CP, where the RIC control request includes at least the following parameters: S-NSSAI to operator-specific access category and access identity mapping, a list of cells, and a rate reduction percentage. In a further embodiment, the gNB-CU-CP triggers a network access rate reduction message to the gNB-DU, and the gNB-DU triggers universal access code (UAC) barring for one or more user equipments (UEs).

[0023] As discussed above, in another general aspect, a non-transitory computer-readable medium having stored thereon instructions for causing a processing circuit to execute a process including detecting slice-specific overload in a radio area network (RAN) based on a physical resource block (PRB) utilization threshold and a predetermined time period, wherein a particular RAN network slice is identified via network slice selection assistance information (S-NSSAI), mapping the slice to an access category in the RAN, and informing the RAN of an action to take to mitigate the detected slice-specific overload.

[0024] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed features from the teachings of the drawings, the disclosure, and the appended claims.

[0025] In the claims, the term "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0026] A single processor, device or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0027] Operations such as obtaining, accessing, analyzing, capturing, comparing, determining, displaying, inputting, obtaining, outputting, providing, storing or storing, computing, simulating, receiving, alerting, and stopping may be implemented as program code means of a computer program and / or dedicated hardware.

[0028] The computer program may be stored and / or distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, or distributed in other forms, such as via the Internet or other wired or wireless communication systems.

Claims

1. 1. A method for performing slice-specific overload control in a wireless communication system, comprising: Detecting slice-specific overload in a Radio Area Network (RAN) based on a physical resource block (PRB) utilization threshold and a predetermined time period, wherein a specific RAN network slice is identified via network slice selection assistance information (S-NSSAI); mapping slices to access categories in the RAN; Informing the RAN of actions to take to mitigate the detected slice-specific overload; A method for providing

2. the PRB utilization threshold is exceeded for the predetermined period of time; The PRB utilization threshold is compared against a baseline configuration for slice-specific resources in a cell; the baseline configuration is in accordance with radio resource management (RRM) policy ratios; The method of claim 1.

3. 3. The method of claim 2, further comprising controlling a gNB aggregation unit control plane (gNB-CU-CP) to trigger specific actions to mitigate the detected slice-specific overload.

4. 4. The method of claim 3, further comprising detecting the slice-specific overload in a gNB distribution unit (gNB-DU).

5. said mapping of slices to operator-specific access categories being performed by an Access Mobility Function (AMF); The AMF sends mapping information to the gNB-CU-CP. The method of claim 4.

6. The method of claim 5, wherein the mapping information is transmitted via a Next Generation (NG) Setup Response message or an AMF Configuration Update message.

7. The method of claim 6 , further comprising transmitting the mapping information from the gNB-CU-CP to the gNB-DU via an F1 Setup Response message or a CU Configuration Update message.

8. The detecting of the slice-specific overload is performed by an xApp running on a Near Real-Time RAN Intelligent Controller (Near RT RIC) that receives real-time streaming of cell-specific S-NSSAI-specific PRB utilization; The near-RT RIC receives an S-NSSAI-specific radio resource management (RRM) policy configuration in a gNB distributed unit (gNB-DU) via an E2 configuration update procedure or a RIC subscription request / RIC indication procedure; The method of claim 3.

9. 10. The method of claim 8, further comprising reporting from the gNB-DU to the near-RT RIC by physical resource block (PRB) and data radio bearer (DRB) activity in a requested reporting period.

10. The near-RT RIC sends a RIC control request to the gNB-CU-CP; The RIC control request includes at least the following parameters: S-NSSAI to operator-specific access category and access identity mapping, a list of cells, and a rate reduction percentage; 10. The method of claim 9.

11. The gNB-CU-CP triggers a network access rate reduction message to the gNB-DU; The gNB-DU triggers Unified Access Control (UAC) barring for one or more User Equipments (UEs); The method of claim 10.

12. A core network; a plurality of user devices; a plurality of base stations (gNBs), each of the plurality of gNBs including at least one aggregation unit (CU) and one distribution unit (DU), wherein a gNB-CU control plane (gNB-CU-CP) is configured to trigger specific actions to mitigate detected slice-specific overload; a radio access network (RAN) comprising: Access Mobility Function (AMF) and Near Real-Time RAN Intelligent Controller (Near RT RIC) and Equipped with At least one gNB-DU or the near-RT RIC is configured to detect slice overload in the RAN based on a physical resource block (PRB) utilization threshold and a predetermined period; A particular RAN network slice is identified via Network Slice Selection Assistance Information (S-NSSAI); Mapping slices to operator-specific categories is performed by one of the AMF or near-RT RIC; The AMF or near-RT RIC sends the mapping information to the gNB-CU-CP; the RAN is configured to take the specific action to mitigate the detected slice-specific overload. Wireless communication system.

13. the PRB utilization threshold is exceeded for the predetermined period of time; The PRB utilization threshold is compared against a baseline configuration for slice-specific resources in a cell; the baseline configuration is in accordance with radio resource management (RRM) policy ratios; 13. The wireless communication system of claim 12.

14. the detecting is performed by the gNB-DU; The mapping information is sent by the AMF to the gNB-CU-CP via a Next Generation (NG) Setup Response message or an AMF Configuration Update message.

14. The wireless communication system of claim 13.

15. The wireless communication system of claim 14 , wherein the gNB-CU-CP is further configured to transmit the mapping information to the gNB-DU via an F1 setup message or a CU configuration update message.

16. The detecting of the slice-specific overload is performed by an xApp running on the near-RT RIC that receives real-time streaming of cell-specific and S-NSSAI-specific PRB utilization; The near-RT RIC receives an S-NSSAI-specific RRM policy configuration in the gNB-DU via an E2 configuration update procedure or a RIC subscription request / RIC indication procedure; 14. The wireless communication system of claim 13.

17. The wireless communication system of claim 16, wherein the gNB-DU is configured to report physical resource block (PRB) and data radio bearer (DRB) activity to the near-RT RIC in a requested reporting period.

18. The near-RT RIC sends a RIC control request to the gNB-CU-CP; The RIC control request includes at least the following parameters: S-NSSAI to operator-specific access category and access identity mapping, a list of cells, and a rate reduction percentage; 18. The wireless communication system of claim 17.

19. The gNB-CU-CP triggers a network access rate reduction message to the gNB-DU; The gNB-DU triggers Universal Access Code (UAC) barring for one or more User Equipments (UEs); 20. The wireless communication system of claim 18.

20. Detecting slice-specific overload in a Radio Area Network (RAN) based on a physical resource block (PRB) utilization threshold and a predetermined time period, wherein a specific RAN network slice is identified via network slice selection assistance information (S-NSSAI); mapping slices to access categories in the RAN; Informing the RAN of actions to take to mitigate the detected slice-specific overload; A non-transitory computer-readable medium having stored thereon instructions for causing a processing circuit to perform a process comprising:

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