Reducing GNB paging traffic using the near real-time RAN intelligent controller XAPP

Abstract

An open radio access network (O-RAN) communication system includes a GNB central unit control plane (GNB-CUCP) for establishing a connection with a near-RT RIC via an E2 interface, a user equipment (UE), multiple cells within a tracking area (TA) of the GNB-CUCP, and an O-RAN near-real-time (Near-RT) RAN intelligent controller (RIC) for hosting an xApp and initiating a subscription procedure with the UE. The GNB-CUCP transmits cell location information of the UE to the near-RT RIC during a UE context release procedure, the near-RT RIC creates and maintains a record of the cell location information received from the GNB-CUCP via the xApp, and the GNB-CUCP pages the UE at a subset of cells from the multiple cells within the TA that correspond to the record of cell location information created and maintained via the xApp.

Description

Technical Field

[0001] In some example embodiments, the subject matter here generally relates to paging in a Radio Access Network (RAN) (O-RAN), and more specifically to reducing paging traffic at a next generation node B (GNB) using a quasi-Real-Time (RT) RAN Intelligent Controller (RIC) xApp.

Background Art

[0002] When a User Equipment (UE) is in an active state, the network recognizes its location at the cell level. However, when the UE is in an idle state, its location is only recognized at the Tracking Area (TA) level. When there is a need to send data to an idle UE, the network needs to wake up the UE via paging so that the UE can become active to receive the data. Currently, paging is performed across the entire TA. That is, to wake up the UE, paging messages are sent via the radio network in all cells belonging to the TA associated with the UE. An idle UE is configured to wake up periodically to check for paging messages to see if there is incoming data. If the UE receives a paging message, the UE returns to the active state to receive the data.

[0003] It should be noted that GNB broadcasts RRC PAGING to all cells under a tracking area according to the "Tracking Area Identity (TAI) list for paging" in NGAP PAGING in order to page UEs. However, since the 5G Core Network (5GC) sends thousands of paging messages per second, this results in a significant waste of air interface resources, as Distributed Units (DUs) need to send even more paging messages.

[0004] For example, if a GNB with 256 cells, all under the same tracking area, needs to send pages to a UE, the GNB must send an RRC PAGING message in all 256 cells. Note that one RRC PAGING message can carry a maximum of 32 paging records. If a DU has more than 32 paging records, the DU must wait for its next Paging Opportunity (PO) to schedule a transmission. Therefore, a large number of paging messages from the 5GC during peak hours can cause delays, potentially leading to the deletion (ejection) of all paging records from the DU or record drop, resulting in retransmission from the 5GC. Thus, optimized paging for UEs in O-RAN communication systems that avoids the aforementioned drawbacks is required. [Overview of the Initiative] [Means for solving the problem]

[0005] In one general embodiment, a method is provided for optimizing the paging of user equipment (UEs) in an Open Radio Access Network (O-RAN) communication system. This method includes establishing an E2 connection between a GNB Central Unit Control Plane (GNB-CUCP) and an O-RAN near-real-time (Near-RT) RAN intelligent controller (RIC) hosting an xApp; initiating a UE subscription procedure by the Near-RT RIC; transmitting the UE's cell location information to the Near-RT RIC by the GNB-CUCP upon UE context release; creating and maintaining a record of the cell locations to which the UE is attached via the xApp; obtaining a current list of cell location information by the GNB-CUCP from the Near-RT RIC xApp; storing a current record of cell location information by the GNB-CUCP; and paging the UE in a subset of cells corresponding to the current record of cell location information, wherein the subset of cells is a subset of cells within the tracking area (TA) of the GNB-CUCP.

[0006] The implementation of this method may include one or more of the following features. In one embodiment of this method, the cell location of the UE is verified according to the 5G-Serving Temporary Mobile Subscriber Identity (5G-S-TMSI) and the New Radio (NR) Cell Global Identifier (NCGI or NRCGI). In one embodiment of this method, the GNB-CUCP transmits the 5G-S-TMSI and NCGI within an Experimental E2 Application Protocol (E2AP) instruction. In one embodiment of this method, the xApp creates and maintains a 5G-S-TMSI record based on the E2AP instruction. In one embodiment of this method, the GNB obtains the current list of 5G-S-TMSI and NCGI via an RIC control request. In one embodiment of this method, the GNB-CUCP stores the 5G-S-TMSI received within the RIC control request. According to one embodiment, the method further includes paging UEs in all cells of the GNB's TA when the paging retry timer expires. In one embodiment, the method relies on a novel experimental E2 Service Model (E2SM) for paging UEs. In one embodiment, the GNB-CUCP receives Next Generation Application Protocol (NGAP) paging messages from the Access Mobility Function (AMF).

[0007] In another common embodiment, an Open Radio Access Network (O-RAN) wireless communication system is provided. The Open Radio Access Network (O-RAN) wireless communication system comprises a GNB Central Unit Control Plane (GNB-CUCP) configured to establish a connection with a Near-Real-Time (Near-RT) RIC via an E2 interface, user equipment (UE), multiple cells within the tracking area (TA) of the GNB-CUCP, and an O-RAN Near-Real-Time (Near-RT) RAN Intelligent Controller (RIC) configured to host an xApp and initiate a subscription procedure with the UE, wherein the GNB-CUCP is configured to transmit the cell location information of the UE to the Near-RT RIC during the UE context release procedure, the Near-RT RIC is further configured to create and maintain a record of the cell location information received from the GNB-CUCP via the xApp, and the GNB-CUCP is configured to page the UE in a subset of cells among the multiple cells in the TA corresponding to the record of cell location information created and maintained via the xApp.

[0008] Implementations of the O-RAN wireless communication system may include one or more of the following features. In one embodiment, the O-RAN wireless communication system establishes cell location information according to a 5G-enabled temporary mobile subscriber identity (5G-S-TMSI) and a New Radio (NR) cell global identifier (NCGI). In one embodiment, the O-RAN wireless communication system transmits the 5G-S-TMSI and NCGI within an experimental E2 application protocol (E2AP) instruction. In one embodiment, the O-RAN wireless communication system creates and maintains a 5G-S-TMSI / NCGI record based on the E2AP instruction. In one embodiment, the O-RAN wireless communication system obtains the current 5G-S-TMSI / NCGI list via a RIC control request. In one embodiment, the O-RAN wireless communication system stores the 5G-S-TMSI / NCGI received within a RIC control request. In one embodiment of the O-RAN wireless communication system, the GNB-CUCP is further configured to page UEs in all cells of the GNB-CUCP's TA when the paging retry timer expires. In one embodiment of the O-RAN wireless communication system, paging UEs is based on a new experimental E2 service model (E2SM). In one embodiment, the O-RAN communication system further includes an Access Mobility Function (AMF), and the GNB-CUCP receives Next Generation Application Protocol (NGAP) paging messages from the AMF.

[0009] In the following drawings: [Brief explanation of the drawing]

[0010] [Figure 1] This diagram shows an existing paging architecture in an Open Radio Access Network (O-RAN).

[0011] [Figure 2]This figure shows a paging architecture in O-RAN according to an exemplary embodiment.

[0012] [Figure 3A] This figure shows the relevant message flow for paging according to an exemplary embodiment. [Figure 3B] This figure shows the relevant message flow for paging according to an exemplary embodiment. [Figure 3C] This figure shows the relevant message flow for paging according to an exemplary embodiment. [Figure 3D] This figure shows the relevant message flow for paging according to an exemplary embodiment. [Modes for carrying out the invention]

[0013] Figure 1 shows the existing paging architecture in an open radio access network (O-RAN) 100. When an incoming call or downlink (DL) data arrives at a user device (UE) 140 in the RRC_IDLE state, the Access and Mobility Management Function (AMF) 110 pages the UE 140 in a selected tracking area (TA) 150 based on the UE's mobility history. In this example, the UE 140 is in cell 170, and the TA includes cell 170 and other cells 160. The AMF 110 sends Next Generation Application Protocol (NGAP) PAGING with a list of Tracking Area Codes (TACs) to all GNBs 120 under the selected tracking area. Cells 160, 170 under each GNB 120 with the same TACs page the UE 140 by sending UE RRC PAGING messages. Since a UE in the RRC_IDLE state is configured to wake up periodically to listen for paging in each paging frame (PF) and paging opportunity (PO), UE140 receives pages when it wakes up.

[0014] Instead of paging a UE in all cells under a Tracking Area (TA), the GNB can paging in a subset of cells based on a record of the cell location to which the UE is attached. Figure 2 shows a paging architecture in an Open Radio Access Network (O-RAN) 200 according to one embodiment. Here, the record of the cell location to which UE 240 is attached is created and maintained by a software tool xApp within a quasi-RT RIC 230. When an incoming call or downlink (DL) data arrives at a user device (UE) 240 in the RRC_IDLE state, the Access and Mobility Management Function (AMF) 210 pages UE 240 in selected Tracking Areas (TAs) 250 based on the UE's mobility history. In this example, UE 240 is in cell 270, and the TA includes cell 270 and other cells 260. The AMF 210 sends Next Generation Application Protocol (NGAP) PAGING with a list of Tracking Area Codes (TACs) to all GNBs 220 under the selected Tracking Area. The GNB220 retrieves a record of the cell location to which the UE240 is attached, and based on that record, selects a subset of cells 160 and 170 under each GNB220 that have the same TAC, and pages the UE240 by sending a UE RRC PAGING message. Since only a subset of cells 160 and 170 are involved in paging the UE240, paging traffic is reduced.

[0015] In one embodiment, a software tool xApp hosted on the quasi-RT's RIC is used to create and maintain UE history on the quasi-RT's RIC. During UE attachment, AMF assigns a 5G-S-TMSI to the UE, and the UE uses this identity for subsequent attachments. Upon UE context release, the GNB sends the 5G-S-TMSI and NRCGI to the quasi-RT RIC. On the quasi-RT RIC, the xApp creates and maintains in a database the history of the cells to which the UE is attached, i.e., the 5G-S-TMSI against the list of NRCGIs. The GNB retrieves this 5G-S-TMSI record information from the quasi-RT RIC xApp upon UE release. When NGAP PAGING arrives from 5GC, if the GNB has a 5G-S-TMSI record in its database based on the received "NGAP PAGING -> UE Paging Identity -> 5G-S-TMSI", the NGB can optimally page the UE based on the UE history. This significantly reduces the paging load on the GNB.

[0016] This also reduces the number of RRC PAGING messages and the time synchronization error budget Uu on the F1 Application Protocol (F1AP). The reduced load on the DU helps to reduce the paging load on the DU, as RRC paging is more concentrated on a subset of cells, and also helps to schedule remaining paging messages more quickly instead of holding them in a queue for the next PO. The reduced load on the DU further helps to reduce the number of NGAP PAGING message retransmissions.

[0017] Figures 3A to 3D show the relevant message flow for optimizing paging traffic according to one embodiment. For simplicity, the TA in this example includes only two cells (cell 1 and cell 2) where UE310 may reside.

[0018] In the E2 connection establishment procedure 510, CUCP340 sends an E2 SETUP REQUEST message to ORAN SC RIC / xApp350, and ORAN SC RIC / xApp350 responds with an E2 SETUP RESPONSE message. In the subscription procedure 520, ORAN SC RIC / xApp350 sends a RIC SUBSCRIPTION REQUEST to CUCP340, and CUCP340 responds with a RIC SUBSCRIPTION RESPONSE message.

[0019] In the 5G-S-TMSI list update procedure 530 to NRCGI, CUCP340 sends RIC INDICATION(Report:(5G-S-TMSI.NRCGI)) to ORAN SC RIC / xApp350 upon UE context release, ORAN SC RIC / xApp350 updates the 5G-S-TMSI record and sends the integrated 5G-S-TMSI record to CUCP340, CUCP340 stores the 5G-S-TMSI record, uses it during NGAP paging, and sends a RIC CONTROL ACKNOWLEDGE message to ORAN SC RIC / xApp350.

[0020] In NGAP paging procedure 540, AMF360 sends an NGAP PAGING message to CUCP340.

[0021] In case 550(a) where the 5G-S-TMSI record from the RIC exists in the database, when the CUCP receives an NGAP PAGING message from the AMF, it starts the paging retry timer. The CUCP pages the UE only in a subset of the cells under the CUCP according to the 5G-S-TMSI record. In this simplified example, Cell 1 is in the subset, but Cell 2 is not in the subset, and the CUCP sends an F1AP PAGING message to the DU320 in Cell 1, and the DU320 in Cell 1 sends an RRC PAGING message to the UE310. In case 560(a) where paging is successful, the UE310 accesses Cell 1, establishes an RRG connection, and the CUCP stops the paging retry timer for the UE and updates the paging as successful. In case 560(b) where paging fails, the UE310 does not access Cell 1, and the paging retry timer expires, the CUCP pages the UE310 based on the TAI list in the NGAP PAGING message. In this example, the CUCP sends an F1AP PAGING message to all cells within the TA, including the DU330 in Cell 2, and the DU330 in Cell 2 sends an RRC PAGING message to the UE310.

[0022] In case 550(b) where the 5G-S-TMSI record from the RIC is not found in the database, since both Cell 1 and Cell 2 are included in the TA, the CUCP sends an F1AP PAGING message to the DU320 in Cell 1 and also sends an F1AP PAGING message to the DU330 in Cell 2. The DU320 in Cell 1 sends an RRC PAGING message to the UE310, and the DU330 in Cell 2 also sends an RRC PAGING message to the UE310.

[0023] Therefore, the above exemplary message flow for optimizing paging traffic according to one embodiment clearly demonstrates an overall reduction in paging traffic in ORAN.

[0024] Other variations to the disclosed embodiments can be understood and achieved by those skilled in the art when implementing the claimed features, from a study 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 perform the functions of several items recited in the claims. The mere fact that certain means are recited in mutually different dependent claims does not indicate that a combination of these means cannot be used advantageously.

[0027] Operations such as obtaining, accessing, analyzing, capturing, comparing, determining, displaying, inputting, acquiring, outputting, providing, storing or storing, calculating, simulating, receiving, warning, and stopping can be implemented as program code means of a computer program and / or as 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, but may also be distributed in other forms, such as via the Internet or other wired or wireless electrical communication systems.

Claims

1. A method for optimizing user equipment (UE) paging in an open radio access network (O-RAN) communication system, the method being: Establish an E2 connection between the GNB Central Unit Control Plane (GNB-CUCP) and the O-RAN Near-Real-Time (Near-RT) RAN Intelligent Controller (RIC) hosting the xApp; Initiating the UE subscription procedure using the aforementioned quasi-RT RIC; When the UE context is released, the cell location information of the UE is transmitted to the quasi-RT RIC by the GNB-CUCP; The UE creates and maintains records of the cell location information to which it is attached via the xApp; Obtaining the current record of the cell position information from the aforementioned quasi-RT RIC xApp using the GNB-CUCP; The current record of the cell location information is stored by the GNB-CUCP; and, Paging the UE in a subset of cells corresponding to the current record of the cell location information, wherein the subset of cells is a subset of cells within the tracking area (TA) of the GNB-CUCP, method.

2. The cell location information of the aforementioned UE is verified according to a 5G-compatible temporary mobile subscriber identity (5G-S-TMSI) and a New Radio (NR) cell global identifier (NCGI). The method according to claim 1.

3. The GNB-CUCP transmits the 5G-S-TMSI and NCGI within the experimental E2 application protocol (E2AP) instruction. The method according to claim 2.

4. The aforementioned xApp creates and maintains a 5G-S-TMSI record based on the E2AP instruction. to hold, The method according to claim 3.

5. The aforementioned GNB obtains a list of current 5G-S-TMSI and NCGI via a RIC control request. The method according to claim 4.

6. The GNB-CUCP stores the 5G-S-TMSI received within the RIC control request. The method according to claim 5.

7. The further includes paging the UE in all cells of the TA of the GNB when the paging retry timer expires. The method according to claim 1.

8. Paging the aforementioned UE is based on a new experimental E2 service model (E2SM). The method according to claim 6.

9. The aforementioned GNB-CUCP receives Next Generation Application Protocol (NGAP) paging messages from the Access Mobility Function (AMF). The method according to claim 1.

10. An open radio access network (O-RAN) communication system, A GNB central unit control plane (GNB-CUCP) configured to establish a connection with a quasi-RT RIC via an E2 interface; User equipment (UE); Multiple cells within the tracking area (TA) of the aforementioned GNB-CUCP; The system comprises an O-RAN Near-Real-Time (Near-RT) RAN Intelligent Controller (RIC) configured to host an xApp and initiate a subscription procedure with the UE, wherein, The GNB-CUCP is configured to transmit the cell location information of the UE to the quasi-RT RIC during the UE context release procedure. The quasi-RT RIC is further configured to create and maintain a record of the cell location information received from the GNB-CUCP via the xApp. The GNB-CUCP receives the current cell position information from the quasi-RT RIC xApp. It is configured to retrieve the record of the cell location information and store the current record of the cell location information, The GNB-CUCP is further configured to page the UE in a subset of the cells in the TA that correspond to the current record of the cell location information. O-RAN communication system.

11. The cell location information is established according to a 5G-compatible temporary mobile subscriber identity (5G-S-TMSI) and a New Radio (NR) cell global identifier (NCGI). The O-RAN communication system according to claim 10.

12. The GNB-CUCP transmits 5G-S-TMSI and NCGI within the experimental E2 application protocol (E2AP) instruction. The O-RAN communication system according to claim 11.

13. The xApp creates and maintains a 5G-S-TMSI / NCGI record based on the E2AP instruction. The O-RAN communication system according to claim 12.

14. The GNB-CUCP obtains the current 5G-S-TMSI / NCGI list via a RIC control request. The O-RAN communication system according to claim 13.

15. The GNB-CUCP stores the 5G-S-TMSI / NCGI received within the RIC control request. The O-RAN communication system according to claim 14.

16. The GNB-CUCP is further configured to page the UE in all cells of the TA of the GNB-CUCP when the paging retry timer expires. The O-RAN communication system according to claim 10.

17. Paging the aforementioned UE is based on a new experimental E2 service model (E2SM). The O-RAN communication system according to claim 15.

18. It also features Access Mobility Function (AMF), The GNB-CUCP receives Next Generation Application Protocol (NGAP) paging messages from the AMF. The O-RAN communication system according to claim 10.

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