Wireless communication system, communication control method, and computer program

Abstract

This wireless communication system comprises an interface for a central unit (CU) that controls handover in a subordinate distributed unit (DU) to acquire calculation resource information on the DU in an O-RAN specification wireless access network.

Description

Wireless communication system, communication control method, and computer program

[0001] The present invention relates to a wireless communication system, a communication control method, and a computer program. This application claims priority to Japanese Patent Application No. 2024-170954, filed in Japan on September 30, 2024, the contents of which are incorporated herein by reference.

[0002] The Open Radio Access Network (O-RAN) Alliance is considering the open and intelligentization of next-generation radio access networks (RANs), such as 5G mobile communication systems (see, for example, Non-Patent Document 1). The O-RAN specifications formulated by the O-RAN Alliance include, for example, specifications for the O1 interface that enables information exchange between an SMO (Service and Management Orchestration) capable of monitoring O-Cloud resources, and O-CUs (O-RAN Central Units) and O-DUs (O-RAN Distributed Units).

[0003] “O-RAN O1 Interface specification for O-CU-UP and O-CU-CP 7.0”, O-RAN.WG5.O-CU-O1.0-R003-v07.00, February 2024

[0004] However, in the conventional O-RAN specifications described above, when the CU (Central Unit) has a DU (Distributed Unit) under it as the handover destination, even if the DU does not have sufficient computing resources, it responds with permission to a handover request from the CU of the handover source. As a result, the base station of the handover source sends "RRC Reconfiguration" to the user terminal (User Equipment: UE) to be handed over, and the UE executes a RACH (Random Access Channel) procedure for the DU of the handover destination. However, since the DU of the handover destination lacks computing resources, it cannot respond to the RACH procedure, and there is a problem that the UE repeats the RACH procedure.

[0005] The present invention has been made in consideration of such circumstances, and its object is to appropriately control handovers.

[0006] One aspect of the present invention is a wireless communication system in an O-RAN specification wireless access network, comprising an interface for a CU (Central Unit) that controls handovers in a subordinate DU (Distributed Unit) to obtain calculation resource information regarding the DU. One aspect of the present invention is the above wireless communication system, wherein the interface includes an inquiry of the calculation resource information from the CU and a response of the calculation resource information to the CU. One aspect of the present invention is the above wireless communication system, wherein the interface includes a periodic notification of the calculation resource information to the CU.

[0007] One aspect of the present invention is a communication control method executed by a wireless communication system. In a wireless access network of O-RAN specifications, a CU (Central Unit) that controls handovers in a subordinate DU (Distributed Unit) obtains calculation resource information regarding the DU through a predetermined interface.

[0008] One aspect of the present invention is a computer program that causes a computer to perform the step of obtaining computing resource information relating to a Distributed Unit (DU) in an O-RAN specification wireless access network, via a predetermined interface, by which a Central Unit (CU) that controls handover in subordinate DUs (Distributed Units) acquires the DUs.

[0009] According to the present invention, the effect of being able to appropriately control handover can be obtained.

[0010] This is a block diagram showing a schematic configuration example of a wireless access network (RAN) of a wireless communication system according to one embodiment. This is a diagram showing the architecture of an O-RAN specification RAN according to one embodiment. This is a diagram showing an example of the procedure of a communication control method according to one embodiment. This is a diagram showing an example of the procedure of a communication control method according to one embodiment. This is a diagram showing an example of the procedure of a communication control method according to one embodiment. This is a diagram showing an example of the procedure of a communication control method according to one embodiment.

[0011] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a block diagram showing a schematic configuration example of a wireless access network (RAN) of a wireless communication system according to one embodiment. The RAN1 shown in Figure 1 is to which the O-RAN specification applies. However, in this embodiment, information not specified in the O1 interface of the O-RAN specification is newly added to the O1 interface.

[0012] RAN1 comprises an SMO (Service and Management Orchestration) 10, O-CUs (O-RAN Central Units) 20 (20-1, 20-2), O-DUs (O-RAN Distributed Units) 30 (30-1, 30-2), and Access Points (APs) #1, #2.

[0013] SMO10 sends and receives information to and from O-CU20 via the O1 interface. The O1 interface is defined in the O-RAN specification.

[0014] O-CU20-1 controls the O-DU30-1 under its control, for example. For instance, O-CU20-1 controls the handover in the O-DU30-1 under its control.

[0015] O-CU20-2 controls the O-DU30-2 under its control, among other things. For example, O-CU20-2 controls the handover in the O-DU30-2 under its control.

[0016] Figure 1 shows an example where user terminal (UE) #1, which is the target of the handover, performs a handover from AP #1, the source AP, to AP #2, the destination AP. The destination O-CU20-2 controls the O-DU30-2 (the destination O-DU) that accommodates AP #2.

[0017] As illustrated in Figure 1, the O-DU 30 is allocated computing resources from accelerators (ACC-1, ACC-2, ..., ACC-n) from the O-Cloud (not shown). Accelerators are provided for each UE (UE-1, UE-2, ..., UE-n). For example, if all the accelerators of O-DU 30-2 are already allocated to a UE, then O-DU 30-2 does not have sufficient computing resources and therefore cannot accommodate a new UE through handover. Accelerators are also called hardware (HW) accelerators.

[0018] In this embodiment, when the O-CU20-2, the handover destination, is the O-DU30-2 under its control, and the O-DU30-2 does not have sufficient computing resources, the O-CU20-2 responds with a denial to the handover request from the O-CU20-1, the handover source. For this reason, in this embodiment, the O-CU20 is provided with an interface for obtaining computing resource information related to the O-DU30 under its control. Specifically, computing resource information related to the O-DU30 is added to the O1 interface so that the O-CU20 can obtain the computing resource information related to the O-DU30 from the SMO10 via the O1 interface. The SMO10 can obtain computing resource information related to the O-DU30 using the existing O-RAN specification. Figure 2 shows the RAN architecture of the O-RAN specification according to this embodiment.

[0019] As a result, when the O-CU20-2, the handover destination, is the O-DU30-2, if it does not have sufficient computing resources based on the computing resource information for O-DU30-2 obtained from SMO10 via the O1 interface, it will respond to the handover request from the O-CU20-1, the handover source, with a denial. Consequently, the O-CU20-1, the handover source, does not send an "RRC Reconfiguration" to the UE#1, the handover target, so UE#1 does not execute the RACH procedure on the O-DU30-2, the handover destination, and therefore the RACH procedure is not repeated, allowing for the early discovery of other handover destinations.

[0020] Figures 3-6 show an example of the procedure for the communication control method according to this embodiment.

[0021] Figures 3 and 4 show examples of the procedure for querying computing resource information and its response, as an example of the communication control method according to this embodiment. Figure 3 shows the case of an intra-CU HO (handover between O-DU 30s under the same O-CU 20). Figure 4 shows the case of an inter-CU HO (handover between O-DU 30s under different O-CU 20s).

[0022] Refer to Figure 3 to explain the Query / Response procedure in Intra-CU HO.

[0023] (Step S1) The UE sends a "Measurement Report" to the Source gNB's O-DU30 indicating that the Target gNB's O-DU30 has met the handover conditions.

[0024] (Step S2) The source base station's O-DU30 sends a "UL RRC Message Transfer" to the source base station's O-CU20. In Intra-CU HO, the source base station's O-CU20 and the target base station's O-CU20 are the same. Therefore, the target base station's O-CU20 receives the "UL RRC Message Transfer" from the source base station's O-DU30.

[0025] (Step S3) The target base station's O-CU20 sends a query for computing resource information regarding the O-DU30 (the target base station's O-DU) to the SMO10 via the O1 interface. As a result, a new query for computing resource information is added to the O1 interface.

[0026] (Step S4) The SMO 10 obtains computing resource information for the target base station's O-DU 30 from the O-Cloud via the Monitoring Service.

[0027] (Step S5) The SMO 10 responds to the target base station's O-CU 20 via the O1 interface with computing resource information regarding the target base station's O-DU 30. As a result, a new response of computing resource information is added to the O1 interface. The target base station's O-CU 20 receives computing resource information regarding the target base station's O-DU 30 from the SMO 10 via the O1 interface.

[0028] (Step S6) The O-CU20 of the target base station determines whether to approve or reject the handover based on the computing resource information of the O-DU30 of the target base station.

[0029] From step S6 onward, the default handover procedure is executed.

[0030] Referring to Figure 4, the Query / Response procedure in Inter-CU HO will be explained. In Figure 4, the parts corresponding to each step in Figure 3 are denoted by the same reference numerals, and their explanations are omitted.

[0031] Step S1 is the same as in Figure 3. Next, step S2a is executed.

[0032] (Step S2a) The source base station's O-DU30 sends "UL RRC Message Transfer" to the source base station's O-CU20.

[0033] (Step S2b) The source base station's O-CU20 sends a Handover Request to the target base station's O-CU20.

[0034] Next, steps S3 to S6 are executed. Steps S3 to S6 are the same as in Figure 3. From step S6 onward, the default handover procedure is executed.

[0035] Figures 5 and 6 show an example of the procedure for periodically transmitting computing resource information as an example of the communication control method according to this embodiment. Figure 5 is for the Intra-CU HO case. Figure 6 is for the Inter-CU HO case. In the procedure shown in Figures 5 and 6, computing resource information concerning the ODU 30 under the O-CU 20 is periodically notified from the SMO 10 to the O-CU 20 via the O1 interface.

[0036] The procedure for periodic transmission in Intra-CU HO will be explained with reference to Figure 5. In Figure 5, the parts corresponding to each step in Figure 3 are denoted by the same reference numerals, and their explanations are omitted.

[0037] Steps S1 and S2 are the same as in Figure 3.

[0038] (Step S11) The SMO 10 periodically obtains computing resource information about the O-DU 30 from the O-Cloud via the monitoring service.

[0039] (Step S12) The SMO 10 periodically transmits computational resource information regarding the O-DU 30 under the control of the O-CU 20 to the O-CU 20 via the O1 interface. Therefore, periodic notifications of computational resource information are newly added to the O1 interface. The O-CU 20 periodically receives computational resource information regarding the O-DU 30 under its control from the SMO 10 via the O1 interface. The O-CU 20 maintains the computational resource information regarding the O-DU 30 under its control.

[0040] (Step S13) The O-CU20 of the target base station determines whether to approve or reject the handover based on the computing resource information for the target base station's O-DU30 from the computing resource information for the subordinate O-DU30s that it receives and holds from the SMO10.

[0041] From step S13 onward, the default handover procedure is executed.

[0042] Referring to FIG. 6, the procedure of periodic transmission in Inter-CU HO will be described. In this FIG. 6, the parts corresponding to the steps of FIGS. 4 and 5 are denoted by the same reference numerals, and the description thereof will be omitted.

[0043] Steps S1, S2a, and S2b are the same as those in FIG. 4. Also, similar to FIG. 5, steps S11, S12, and S13 are executed. After step S13, the default handover procedure is executed.

[0044] Hereinafter, an example of calculation resource information will be described.

[0045] As an example of calculation resource information, information regarding a hardware (HW) accelerator can be cited. Information regarding the HW accelerator is, for example, the usage rate of the HW accelerator, the free status of the HW accelerator, information on whether the HW accelerator can be secured for a newly accommodated UE, and the like.

[0046] As an example of calculation resource information, information regarding the CPU (Central Processing Unit) of the O-Cloud can be cited. Information regarding the CPU is, for example, the usage rate of the CPU, the free status of the CPU, information on whether the CPU resources can be secured for a newly accommodated UE, and the like.

[0047] According to the present embodiment, an effect that appropriate control of handover can be achieved can be obtained.

[0048] Note that, as a result, for example, since an improvement in the overall service quality in a wireless communication system can be realized, it is possible to contribute to Goal 9 of the Sustainable Development Goals (SDGs) led by the United Nations, "Build resilient infrastructure, promote sustainable industrialization, and foster innovation."

[0049] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and design changes and the like within the scope not departing from the gist of the present invention are also included.

[0050] Alternatively, computer programs for realizing the functions of each of the above-mentioned devices may be recorded on a computer-readable recording medium, and the programs recorded on this recording medium may be loaded into a computer system and executed. The term "computer system" here may include hardware such as an operating system and peripheral devices. Furthermore, "computer-readable recording medium" refers to writable non-volatile memory such as flexible disks, magneto-optical disks, ROMs, and flash memory, portable media such as DVDs (Digital Versatile Discs), and storage devices such as hard disks built into a computer system.

[0051] Furthermore, "computer-readable recording media" includes volatile memory (e.g., DRAM (Dynamic Random Access Memory)) within a computer system that acts as a server or client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line, which retains the program for a certain period of time. In addition, the above program may be transmitted from the computer system that stores the program in a storage device, etc., to another computer system via a transmission medium or by transmission waves within the transmission medium. Here, the "transmission medium" for transmitting the program refers to a medium that has the function of transmitting information, such as a network such as the Internet or a communication line such as a telephone line. Furthermore, the above program may be for the purpose of realizing a part of the above-mentioned functions. In addition, it may be a so-called differential file (differential program) that can realize the above-mentioned functions in combination with a program already recorded in the computer system.

[0052] According to the present invention, appropriate control of handover can be achieved.

[0053] 1...Wireless access network, 10...SMO, 20...O-CU, 30...O-DU, ACC...Accelerator, AP...Access point, UE...User terminal

Claims

1. A wireless communication system in which a Central Unit (CU) that controls handover in a Distributed Unit (DU) under the O-RAN specification is equipped with an interface for acquiring computing resource information related to the DU.

2. The wireless communication system according to claim 1, wherein the interface includes querying the computing resource information from the CU and responding to the computing resource information with the CU.

3. The wireless communication system according to claim 1, wherein the interface includes periodic notification of the computing resource information to the CU.

4. A communication control method performed by a wireless communication system, wherein, in an O-RAN specification wireless access network, a Central Unit (CU) that controls handover in subordinate Distributed Units (DUs) acquires computing resource information relating to the DUs via a predetermined interface.

5. A computer program that causes a computer to perform the step of obtaining computing resource information relating to a Distributed Unit (DU) in an O-RAN specification wireless access network, via a predetermined interface, by which a Central Unit (CU) that controls handover in subordinate DUs (Distributed Units) acquires the DUs.

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