Reducing GNB paging traffic using 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 herein relates generally to paging in Radio Access Networks (RANs) (O-RANs), and more specifically to reducing paging traffic in next generation node Bs (GNBs) using a near real-time (RT) RAN Intelligent Controller (RIC) xApp. [Background technology]

[0002] When a User Equipment (UE) is in an active state, the network knows its location at the cell level. However, when the UE is in an idle state, its location is only known at the tracking area (TA) level. When data needs to be transmitted to an idle UE, the network must wake up the UE via paging so that the UE can enter an active state to receive the data. Currently, paging is performed across the entire TA. That is, to wake up the UE, a paging message is transmitted via the wireless 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, it returns to the active state to receive data.

[0003] It should be noted that to page a UE, the GNB broadcasts RRC PAGING in all cells under the tracking area according to the "Tracking Area Identity (TAI) List for Paging" in NGAP PAGING. However, since the 5G Core Network (5GC) sends thousands of paging messages per second, this will result in a significant waste of air interface resources as the Distributed Unit (DU) needs to send more paging messages.

[0004] For example, if a GNB with 256 cells, all of which are under the same tracking area, needs to send a page to a UE, the GNB must transmit an RRC PAGING message to 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 the next paging opportunity (PO) for that UE to schedule transmission. Therefore, a large number of paging messages from the 5GC during peak hours may cause delays, leading to the deletion (ejection) of all paging records for the DU or record drops, resulting in retransmissions from the 5GC. Therefore, there is a need for optimized paging of UEs in an O-RAN communication system without the above-mentioned drawbacks. Summary of the Invention [Means for solving the problem]

[0005] In one general aspect, a method for optimizing paging of a user equipment (UE) in an Open Radio Access Network (O-RAN) communication system is provided, the method including 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, sending cell location information of the UE by the GNB-CUCP to the near-RT RIC upon UE context release, creating and maintaining a record of cell locations to which the UE is attached via the xApp, obtaining a current list of cell location information from the near-RT RIC xApp by the GNB-CUCP, storing the current record of cell location information by the GNB-CUCP, and paging the UE at a subset of cells corresponding to the current record of cell location information, where the subset of cells is a subset of cells within a tracking area (TA) of the GNB-CUCP.

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

[0007] In another general aspect, an Open Radio Access Network (O-RAN) wireless communications system is provided, comprising: a GNB central unit control plane (GNB-CUCP) configured to establish a connection with a quasi-RT RIC over an E2 interface; a user equipment (UE); a plurality of cells within a 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 send cell location information of the UE to the quasi-RT RIC upon a 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, and the GNB-CUCP is configured to page the UE at a subset of cells of the plurality of cells within the TA that correspond to the record of cell location information created and maintained via the xApp.

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

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

[0010] [Figure 1] FIG. 1 illustrates an existing paging architecture in an open radio access network (O-RAN).

[0011] [Figure 2]FIG. 1 illustrates a paging architecture in an O-RAN according to an example embodiment.

[0012] [Figure 3A] FIG. 10 illustrates a related message flow for paging, according to an exemplary embodiment. [Figure 3B] FIG. 10 illustrates a related message flow for paging, according to an exemplary embodiment. [Figure 3C] FIG. 10 illustrates a related message flow for paging, according to an exemplary embodiment. [Figure 3D] FIG. 10 illustrates a related message flow for paging, according to an exemplary embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1 illustrates an existing paging architecture in an open radio access network (O-RAN) 100. When an incoming call or downlink (DL) data arrives for a user equipment (UE) 140 in an RRC_IDLE state, an access and mobility management function (AMF) 110 pages the UE 140 in selected tracking areas (TAs) 150 based on the UE's mobility history. In this example, the UE 140 is in a cell 170, and the TA includes the cell 170 and another cell 160. The AMF 110 sends a Next Generation Application Protocol (NGAP) PAGING message with a list of tracking area codes (TACs) to all GNBs 120 under the selected tracking area. The cells 160, 170 under each GNB 120 with the same TAC page the UE 140 by sending a UE RRC PAGING message. A UE in RRC_IDLE state is configured to wake up periodically to listen for pages at each paging frame (PF) and paging opportunity (PO), so that the UE 140 receives the page when it wakes up.

[0014] Instead of paging the UE in all cells under a TA (Tracking Area), the GNB can page in a subset of cells based on a record of the cell location to which the UE is attached. Figure 2 illustrates 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 the UE 240 is attached is created and maintained by a software tool xApp in the quasi-RT RIC 230. When an incoming call or downlink (DL) data arrives for a user equipment (UE) 240 in an RRC_IDLE state, the access and mobility management function (AMF) 210 pages the UE 240 in selected tracking areas (TAs) 250 based on the UE's mobility history. In this example, the UE 240 is in cell 270, and the TA includes cell 270 and other cells 260. The AMF 210 sends a Next Generation Application Protocol (NGAP) PAGING message with a list of tracking area codes (TACs) to all GNBs 220 under the selected tracking area. The GNBs 220 obtain a record of the cell locations to which the UEs 240 are attached, and based on the record, select a subset of the cells 160, 170 under each GNB 220 that have the same TAC and page the UEs 240 by sending a UE RRC PAGING message. Because only the subset of cells 160, 170 is involved in paging the UEs 240, paging traffic is reduced.

[0015] In one embodiment, a software tool xApp hosted in the quasi-RT RIC is used to create and maintain a UE history in the quasi-RT RIC. During UE attach, the AMF assigns a 5G-S-TMSI to the UE, and the UE uses this identity in subsequent attaches. Upon UE context release, the GNB sends the 5G-S-TMSI and NRCGI to the quasi-RT RIC. In the quasi-RT RIC, the xApp creates and maintains in a database a history of the cells to which the UE is attached, i.e., the 5G-S-TMSI for the list of NRCGIs. The GNB obtains this 5G-S-TMSI record information from the quasi-RT RIC xApp upon UE release. When NGAP PAGING arrives from the 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 on the F1 Application Protocol (F1AP) and the time synchronization error budget Uu. The reduced load at the DU helps reduce the paging load at the DU since RRC paging is more concentrated on a subset of cells, and also helps to schedule the remaining paging messages more quickly instead of keeping them in a queue for the next PO. The reduced load at the DU further helps to reduce the number of NGAP PAGING message retransmissions.

[0017] 3A-3D show relevant message flows 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 UE 310 may reside.

[0018] In an E2 connection establishment procedure 510, the CUCP 340 sends an E2 SETUP REQUEST message to the ORAN SC RIC / xApp 350, which responds with an E2 SETUP RESPONSE message. In a subscription procedure 520, the ORAN SC RIC / xApp 350 sends a RIC SUBSCRIPTION REQUEST to the CUCP 340, which responds with a RIC SUBSCRIPTION RESPONSE message.

[0019] In the 5G-S-TMSI to NRCGI list update procedure 530, upon UE context release, the CUCP 340 sends a RIC INDICATION (Report: (5G-S-TMSI.NRCGI)) to the ORAN SC RIC / xApp 350, which updates the 5G-S-TMSI record and sends the merged 5G-S-TMSI record to the CUCP 340, which stores the 5G-S-TMSI record, uses it during NGAP paging, and sends a RIC CONTROL ACKNOWLEDGE message to the ORAN SC RIC / xApp 350.

[0020] In the NGAP paging procedure 540, the AMF 360 sends an NGAP PAGING message to the CUCP 340.

[0021] In case 550(a), where the 5G-S-TMSI record from the RIC exists in the database, the CUCP starts the paging retry timer when it receives the NGAP PAGING message from the AMF. The CUCP pages the UE only in the subset of 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, so the CUCP sends an F1AP PAGING message to DU 320 in cell 1, which sends an RRC PAGING message to UE 310. In case 560(a), where the paging is successful, UE 310 accesses cell 1 and 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, UE 310 does not access cell 1, and the paging retry timer expires, CUCP pages UE 310 based on the TAI list in the NGAP PAGING message. In this example, CUCP sends an NGAP PAGING message to all cells in the TA, including DU 330 in cell 2, and DU 330 in cell 2 sends an RRC PAGING message to UE 310.

[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 DU 320 in cell 1 and also sends an F1AP PAGING message to DU 330 in cell 2. DU 320 in cell 1 sends an RRC PAGING message to UE 310, and DU 330 in cell 2 also sends an RRC PAGING message to UE 310.

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

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

[0025] In the claims, the word "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, calculating, simulating, receiving, alerting, and stopping may 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 telecommunications systems.

Claims

1. 1. A method for optimizing paging of a user equipment (UE) in an open radio access network (O-RAN) communication system, the method comprising: Establishing E2 connectivity 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 a UE subscription procedure by the quasi-RT RIC; Sending cell location information of the UE to the quasi-RT RIC by the GNB-CUCP when a UE context is released; creating and maintaining via the xApp a record of the cell location to which the UE is attached; obtaining, by said GNB-CUCP, a current list of cell location information from said quasi-RT RIC xApp; storing, by said GNB-CUCP, said current record of cell location information; and paging the UE in a subset of cells corresponding to the current record of cell location information, the subset of cells being a subset of cells within a Tracking Area (TA) of the GNB-CUCP. method.

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

3. the GNB-CUCP sends the 5G-S-TMSI and NCGI within an Experimental E2 Application Protocol (E2AP) indication; The method of claim 2.

4. The xApp creates and maintains a 5G-S-TMSI record based on the E2AP instruction; The method of claim 3.

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

6. The GNB-CUCP stores the 5G-S-TMSI received in the RIC control request; The method of claim 5.

7. and paging the UE in all cells of the TA of the GNB when a paging retry timer expires. The method of claim 1.

8. paging the UE is based on a new experimental E2 service model (E2SM); The method of claim 6.

9. The GNB-CUCP receives a Next Generation Application Protocol (NGAP) paging message from an Access Mobility Function (AMF); The method of claim 1.

10. 1. An open radio access network (O-RAN) communication system, comprising: a GNB Central Unit Control Plane (GNB-CUCP) configured to establish a connection with the quasi-RT RIC via an E2 interface; User Equipment (UE); A plurality of cells within a Tracking Area (TA) of said GNB-CUCP; 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 send cell location information of the UE to the quasi-RT RIC during a 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 is configured to page the UE in a subset of cells of the plurality of cells within the TA, the subset of cells corresponding to the record of cell location information created and maintained via the xApp; O-RAN communication system.

11. The cell location information is established according to a 5G-enabled 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 sends the 5G-S-TMSI and NCGI within an Experimental E2 Application Protocol (E2AP) indication; 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 of 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 in the RIC control request; The O-RAN communication system of claim 14.

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

17. paging the UE is based on a new experimental E2 service model (E2SM); The O-RAN communication system of claim 15.

18. Further equipped with Access Mobility Function (AMF), The GNB-CUCP receives a Next Generation Application Protocol (NGAP) paging message from the AMF. The O-RAN communication system according to claim 10.

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