Patent Publication Number: US-2022232508-A1

Title: Device and method for relaying service registration event via e2 interface in wireless access network communication system

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation application, claiming priority under § 365(c), of an International application No. PCT/KR2020/013816, filed on Oct. 8, 2020, which is based on and claims the benefit of a U.S. Provisional application Ser. No. 62/912,237, filed on Oct. 8, 2019, in the U.S. Patent and Trademark Office, and of a Korean patent application number 10-2020-0130501, filed on Oct. 8, 2020, in the Korean Intellectual Property Office, the disclosure of each of which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     1. Field 
     The disclosure relates to a radio access network communication system. More particularly, the disclosure relates to message relay apparatus and method if a service event occurs for a base station conforming to an open radio access network (O-RAN) standard using an E2 message of the radio communication system. 
     2. Description of Related Art 
     To meet the demand for wireless data traffic having increased since deployment of 4 th  generation (4G) communication systems, efforts have been made to develop an improved 5 th  generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post long term evolution (LTE) System’. 
     The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems. 
     In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like. 
     In the 5G system, hybrid frequency shift keying (FSK) and quadrature amplitude modulation (QAM) (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed. 
     The 5G system and new radio or next radio (NR) are commercialized to satisfy demand for wireless data traffic, and provide a high data rate service to a user through the 5G system like 4G, and it is also expected that wireless communication services for various purposes such as internet of things and a service requiring high reliability for a specific purpose may be provided. Open radio access network (O-RAN) established by operators and equipment providers in a system where the current 4G communication system and the 5G system are mixed defines a new network element (NE) and an interface standard based on the existing 3rd generation partnership project (3GPP) standard, and suggests an O-RAN structure. 
     The above information is presented as background information only to assist with an understanding of the disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the disclosure. 
     SUMMARY 
     As a 4 th  generation (4G)/5 th  generation (5G) communication system (hereafter, a 4G/5G system, new radio or next radio (NR)) is commercialized, a virtualized network requires a differentiated service support for users. Open-radio access network (O-RAN) newly defines the existing 3rd generation partnership project (3GPP) network entity (NE), radio unit (RU), distributed unit (DU), central unit (CU)-control plane (CP), and CU-user plane (UP) as O-RU, O-DU, O-CU-CP, and O-CU-UP respectively, and additionally standardizes a near-real-time RAN intelligent controller (RIC). 
     Aspects of the disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the disclosure is to provide an apparatus relaying an E2 subscription message for requesting a service from the newly defined RIC to the O-DU, the O-CU-CP or the O-CU-UP. 
     Another aspect of the disclosure is to provide a method for subdividing and processing an E2 subscription message based on a user equipment (UE), a group, a cell, and a network slice. Herein, the O-RU, the O-DU, the O-CU-CP, and the O-CU-UP may be understood as objects constituting the RAN which may operate according to the O-RAN standard, and may be referred to as E2 nodes. 
     Another aspect of the disclosure is to provide a RIC generating an E2 subscription request message, and setting a call processing EVENT by relaying it to the E2 NODE (e.g., the O-CU-CP, the O-CU-UP, the O-DU), and the E2 node relays the subscription request response message relayed to the RIC after the event setup. The disclosure relates to an E2 indication message for a newly defined RIC to divide a call processing message corresponding to an E2 event occurring in O-DU, O-CU-CP, O-CU-UP for a whole message set in a subscription event condition or for each specific application protocol per I/F, and received in a container form in a cell unit, a group ID unit, a network slice unit, and a UE unit. 
     Another aspect of the disclosure is to provide a method of a first node of a wireless communication system. The method includes dividing a call processing message received at an E2 NODE from a call processing block for each I/F, generating the divided message in a cell unit, a user equipment (UE) unit, a group ID unit, and a network slice unit container, and relaying an E2 indication message from the E2 node to the RIC. In addition, the E2 indication message may be identified based on a detailed information element of the E2 indication transmitted from the RIC, and the information element information may include MESSAGE TYPE identifier information, RIC REQUEST ID identifier information, E2 NODE FUNCTION ID identifier information and RIC SUBSCRIPTION TYPE identifier information set based on the call processing function of E2 NODE. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
     In accordance with an aspect of the disclosure, a method performed by an E2 node is provided. The method includes transmitting a radio access network (RAN) intelligent controller (RIC) indication message to an RIC via an E2 interface, the RIC indication message may include indication type information, and the indication type information may indicate one of an ‘insert’ type or a ‘report’ type. 
     In accordance with another aspect of the disclosure, a method performed by an RIC is provided. The method includes receiving an RIC indication message from an E2 node via an E2 interface, the RIC indication message may include indication type information, and the indication type information may indicate one of an ‘insert’ type and a ‘report’ type. 
     In accordance with another aspect of the disclosure, an apparatus functioning as an E2 node is provided. The apparatus includes at least one transceiver, and at least one processor coupled with the at least one transceiver, the at least one processor may be configured to transmit an RIC indication message to an RIC via an E2 interface, the RIC indication message may include indication type information, and the indication type information may indicate one of an ‘insert’ type or a ‘report’ type. 
     In accordance with another aspect of the disclosure, an apparatus functioning as an RIC is provided. The apparatus includes at least one transceiver, and at least one processor coupled with the at least one transceiver, the at least one processor is configured to receive an RIC indication message from an E2 node via an E2 interface, the RIC indication message may include indication type information, and the indication type information may indicate one of an ‘insert’ or a ‘report’ type. 
     An apparatus and a method according to various embodiments of the disclosure, may indicate a type of a radio access network (RAN) intelligent controller (RIC) service through an indication message of an E2 node, and thus provide an effective service procedure between a near real time (RT) RIC and the E2 node. 
     Effects obtainable from the disclosure are not limited to the above-mentioned effects, and other effects which are not mentioned may be clearly understood by those skilled in the art of the disclosure through the following descriptions. 
     Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of certain embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates an example of a 4 th  generation (4G) long term evolution (LTE) core system according to an embodiment of the disclosure; 
         FIG. 2A  illustrates an example of a 5 th  generation (5G) non-standard alone (NSA) system according to an embodiment of the disclosure; 
         FIG. 2B  illustrates an example of architecture for open (O)-radio access network (RAN) according to an embodiment of the disclosure; 
         FIG. 3  illustrates a protocol stack of an E2 application protocol message in a radio access network according to an embodiment of the disclosure; 
         FIG. 4  illustrates an example of a connection between a base station and a RAN intelligence controller (RIC) in a radio access network according to an embodiment of the disclosure; 
         FIG. 5  illustrates a configuration of a device in a radio access network according to an embodiment of the disclosure; 
         FIG. 6  illustrates logical functions related to E2 messages of an E2 node and an RIC in a radio access network according to an embodiment of the disclosure; 
         FIG. 7A  illustrates an example of a signaling procedure between an E2 node and an RIC according to an embodiment of the disclosure; 
         FIG. 7B  illustrates an example of a subscription procedure between the E2 node and the RIC according to an embodiment of the disclosure; and 
         FIGS. 8, 9, 10, 11, and 12  illustrate examples of messages used for an E2 indication-based message relay procedure according to various embodiments of the disclosure. 
     
    
    
     The same reference numerals are used to represent the same elements throughout the drawings. 
     DETAILED DESCRIPTION 
     The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness. 
     Terms and words used in the following description and claims are not limited to the bibliographical meanings, but are merely used by the inventor to enable a clear and consistent understanding of the disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the disclosure is provided for illustration purpose only and not for the purpose of limiting the disclosure as defined by the appended claims and their equivalents. 
     It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces. 
     Among the terms used in the disclosure, terms defined in a general dictionary may be interpreted as having the same or similar meanings as those in the context of the related art, and unless explicitly defined in the disclosure, may not be interpreted as ideal or excessively formal meanings. In some cases, even terms defined in the disclosure may not be interpreted to exclude embodiments of the disclosure. 
     A hardware-based approach will be described as an example in various embodiments of the disclosure to be described hereafter. However, various embodiments of the disclosure include technology which uses both hardware and software, and accordingly various embodiments of the disclosure do not exclude a software-based approach. 
     Hereafter, the disclosure relates to an apparatus and a method for performing a subscription procedure between a device in a radio access network (RAN) and a device for controlling the RAN in a wireless communication system. 
     Terms for signals, terms indicating channels, terms indicating control information, terms indicating network entities, and terms indicating components of a device used in the following explanation are illustrated for convenience of description. Accordingly, the disclosure is not limited to the terms to be described, and other terms having the same technical meaning may be used. 
     In addition, the disclosure describes various embodiments using terms used in some communication standard (e.g., 3rd generation partnership project (3GPP)), but this is only an example for description. Various embodiments of the disclosure may be easily modified and applied in other communication systems. 
     Hereafter, an uplink indicates a radio link for transmitting data or a control signal from a user equipment (UE) or a mobile station (MS) to an eNode B or a base station (BS), and a downlink indicates a radio link for transmitting data or a control signal from the eNode B to the UE in the disclosure. Also, the eNode B is an entity which performs resource allocation of the UE, and may be at least one of an eNode B, a Node B, a BS, a generation node B (gNB) radio access unit, a BS controller, or a node on the network. The UE may include a UE, an MS, a cellular phone, a smart phone, a computer, or a multimedia system for performing a communication function. 
     A 5 th  generation (5G) communication system (hereafter, may be used interchangeably with a 5G system, a new radio or next radio (NR) system) is commercialized to satisfy demand for wireless data traffic, and provides a high data rate service to users through the 5G system like 4G, and it is also predicted that wireless communication services for various purposes such as internet of things and a service requiring high reliability for specific purposes may be provided. 
     Open-RAN (O-RAN) established by operators and equipment providers in a system where the current 4G communication system and the 5G system are mixed defines a new network element (NE) and an interface standard based on the existing 3GPP standard, and thus presents an O-RAN structure. The O-RAN newly defines the existing 3GPP network entity (NE), radio unit (RU), distributed unit (DU), central unit (CU)-control plane (CP), and CU-user plane (UP) as O-RU, O-DU, O-CU-CP, and O-CU-UP respectively, and besides, the O-RAN has standardized a near-real-time RAN intelligent controller (RIC) and a non-real-time (NRT) RIC. For example, the RIC may be a server intensively deployed at one physical place. In addition, the RIC may be a logical node for collecting information on a cell site transmitted and received by a UE and the O-DU, the O-CU-CP or the O-CU-UP. The O-DU and the RIC, the O-CU-CP and the RIC, and the O-CU-UP and the RIC may be connected via Ethernet. For doing so, an interface standard for communications between the O-DU and the RIC, between the O-CU-CP and the RIC, and between the O-CU-UP and the RIC are required, and message formats such as E2-DU, E2-CU-CP, E2-CU-UP requires defining procedures between the O-DU, the O-CU-CP, the O-CU-UP and the RIC. In particular, differentiated service support is required for users in a virtualized network, and it is necessary to define functions of messages of E2-DU, E2-CU-CP and E2-CU-UP to support a service for wide cell coverage, by concentrating a call processing message/function generating in the O-RAN on the RIC. 
     Specifically, the RIC may generate and transmit an E2 subscription message to the O-DU, the O-CU-CP, or the O-CU-UP and thus set an event occurrence condition. The O-DU, the O-CU-CP, or the O-CU-UP may determine that the set condition is satisfied, load a 3GPP call processing message corresponding to the satisfied condition in a container to the RIC, classify into a user identifier, a cell identifier, a network slice identifier and so on, and then transmit through an E2 indication/report. 
     Call processing message information collected in the O-RAN based on the user identifier may be identified that the RIC is for a specific user/specific cell/specific network slice per I/F. The collected information may be transmitted from at least one of the (O-)CU-CP, the (O-)CU-UP, and the (O-)DU. The RIC may identify based on the user identifier that information collected from different entities is related to one specific user/specific cell/specific network slice, provide a specialized service for the specific user/specific cell/specific network slice with respect to a plurality of cells/network slices based on the collected information, and determine a key performance indicator (KPI) of the service provided to each user. 
     Since a general call processing service is restricted to a base station basis, the number of supportable cells is limited. In addition, since the collected information is limited to a specific base station, efficient monitoring on radio resources for the whole was not possible. According to various embodiments of the disclosure, the RIC may collect call processing messages (e.g., E1, F1, X2, XN, RRC, etc.) per I/F or respectively generated by the O-RU, the O-DU, the O-CU-CP or the O-CU-UP, and thus efficiently provide resource optimization and a user specific service or a user requested service with respect to the specific user/specific cell/specific network slices for wide cells. For example, the RIC may configure an additional carrier by efficiently dividing the network slice or by serving a specific terminal through carrier aggregation for the resource optimization, or configure an additional cell for performing dual access to serve a specific terminal through dual connectivity (DC). In addition, the RIC may configure a specific terminal to avoid connection with a specific cell and to connect with a specific cell in inter-cell movement. In addition, the RIC may efficiently perform the resource optimization through machine learning through analysis based on the collected information. In addition, the resource optimization of the disclosure is not limited to the described content. Also, according to the disclosure, it is possible not only to collect information per terminal but also to collect and analyze information per bearer. 
     The collected information of the specific user may be used at a collection server, the RIC or the NRT-RIC but may be also provided to an operations support system (OSS) or/and a business support system (BSS) to provide the specialized service to the user. 
       FIG. 1  illustrates an example of a 4 th  generation (4G) long term evolution (LTE) core system according to an embodiment of the disclosure. 
     Referring to  FIG. 1 , the LTE core system includes a base station  110 , a terminal  120 , a serving gateway (S-GW)  130 , a packet data network gateway (P-GW)  140 , a mobility management entity (MME).  150 , a home subscriber server (HSS)  160 , and a policy and charging rule function (PCRF)  170 . 
     The base station  110  is a network infrastructure for providing radio access to the terminal  120 . For example, the base station  110  is a device which performs scheduling by collecting status information such as a buffer status, an available transmission power, and a channel status of the terminal  120 . The base station  110  has coverage defined as a specific geographic region based on a signal transmission distance. The base station  110  is connected to the MME  150  via an S1-MME interface. Besides the base station, the base station  110  may be referred to as an ‘access point (AP)’, an ‘eNodeB (eNB)’, a ‘wireless point’, and a ‘transmission/reception point (TRP)’ or other term having the equivalent technical meaning. 
     The terminal  120  is a device used by the user, and performs communication with the base station  110  over a radio channel. In some cases, the terminal  120  may be operated without user&#39;s involvement. That is, the terminal  120  may be a device which performs machine type communication (MTC), and may not be carried by the user. The terminal  120  may be referred to as a user equipment or ‘UE’, a ‘mobile station’, a ‘subscriber station’, a ‘customer-premises equipment (CPE)’, a ‘remote terminal’, a ‘wireless terminal’, or a ‘user device’, or other term having the equivalent technical meaning. 
     The S-GW  130  provides a data bearer, and generates or controls the data bearer under control of the MME  150 . For example, the S-GW  130  processes a packet arriving from the base station  110  or a packet to be forwarded to the base station  110 . In addition, the S-GW  130  may perform an anchoring role in handover of the terminal  120  between base stations. The P-GW  140  may function as a connection point to an external network (e.g., an internet network). In addition, the P-GW  140  allocates an internet protocol (IP) address to the terminal  120 , and serves as an anchor for the S-GW  130 . In addition, the P-GW  140  may apply quality of service (QoS) policy of the terminal  120 , and manage account data. 
     The MME  150  manages mobility of the terminal  120 . In addition, the MME  150  may perform authentication, bearer management, and the like on the terminal  120 . That is, the MME  150  is responsible for mobility management and various control functions of the terminal. The MME  150  may interwork with a serving general packet radio service (GPRS) support node (SGSN)  155 . 
     The HSS  160  stores key information and a subscriber profile for the authentication of the terminal  120 . The key information and the subscriber profile are transmitted from the HSS  160  to the MME  150  if the terminal  120  accesses the network. 
     The PCRF  170  defines a policy and a charging rule. The stored information is forwarded from the PCRF  170  to the P-GW  140 , and the P-GW  140  may control the terminal  120  (e.g., QoS management, charging, etc.) based on the information provided from the PCRF  170 . 
     Carrier aggregation (hereafter, ‘CA’) technology is a technology which combines a plurality of component carriers, and transmits and receives at one terminal a signal using the plurality of the component carriers at the same time and thus increases frequency use efficiency in terms of the terminal or the base station. Specifically, according to the CA technology, the terminal and the base station may transmit and receive signals using a broadband using the plurality of the component carriers in the uplink (UL) and the downlink (DL), wherein the component carriers are located in different frequency bands respectively. Hereafter, the UL indicates a communication link through which the terminal transmits a signal to the base station, and the DL indicates a communication link through which the base station transmits a signal to the terminal. At this time, the numbers of uplink component carriers and downlink component carriers may be different. 
     Dual connectivity or multi connectivity is a technology for increasing the frequency use efficiency in terms of the terminal or the base station, in which one terminal is connected to a plurality of different base stations and transmits and receives signals simultaneously using carriers within the plurality of the base stations positioned in different frequency bands. The terminal may be connected to a first base station (e.g., a base station which provides services using the LTE technology or the 4G mobile communication technology) and a second base station (e.g., a base station which provides services using the NR technology or 5G mobile communication technology) at the same time to transmit and receive traffic. In this case, frequency resources used by each base station may be positioned in different bands. As such, the operation scheme based on the dual connectivity scheme of the LTE and the NR may be referred to as 5G non-standalone (NSA). 
       FIG. 2A  illustrates an example of a 5G NSA system according to an embodiment of the disclosure. 
     Referring to  FIG. 2A , the 5G NSA system includes an NR RAN  210   a , an LTE RAN  210   b , a terminal  220 , and an evolved packet core network (EPC)  250 . The NR RAN  210   a  and the LTE RAN  210   b  are connected to the EPC  250 , and the terminal  220  may be served by any one or both of the NR RAN  210   a  and the LTE RAN  210   b  at the same time. The NR RAN  210   a  includes at least one NR base station, and the LTE RAN  210   b  includes at least one LTE base station. Herein, the NR base station may be referred to as a ‘5G node’, a ‘gNB’ or other term having the equivalent technical meaning. In addition, the NR base station may have a structure divided into a CU and a DU, and the CU may also have a structure divided into a CU-CP unit and a CU-UP unit. 
     In the structure shown in  FIG. 2A , the terminal  220  may perform radio resource control (RRC) access through the first base station (e.g., a base station belonging to the LTE RAN  210   b ), and may be served with functions (e.g., connection management, mobility management, etc.) provided in the control plane. In addition, the terminal  220  may receive additional radio resources for transmitting and receiving data via a second base station (e.g., a base station belonging to the NR RAN  210   a ). This dual connectivity technology using the LTE and the NR may be referred to as evolved universal terrestrial radio access (E-UTRA)-NR (EN)-dual connectivity (DC). Similarly, the dual connectivity technology in which the first base station uses the NR technology and the second base station uses the LTE technology is referred to as NR-E-UTRA (NE)-DC. In addition, various embodiments may be applied to the multi connectivity and the CA technology of various types. In addition, various embodiments may be applicable even if a first system using a first communication technology and a second system using a second communication technology are implemented in one device or if the first base station and the second base station are located at the same geographic location. 
       FIG. 2B  shows an architecture example for the O-RAN according to an embodiment of the disclosure. For the sake of E2-SM-KPI monitoring (KPIMON) of an E2 service model, an O-RAN non-stand alone in the multi-connectivity operation using the E-UTRA and the NR radio access technology is considered, whereas the E2 node may be assumed to be in an O-RAN stand alone mode. 
     Referring to  FIG. 2B , in deployment of the O-RAN non-stand alone mode, the eNB is connected with the EPC via an S1-C/S1-U interface, and is connected with the O-CU-CP via an X2 interface. The O-CU-CP for the deployment of the O-RAN stand alone mode may be connected with a 5G core (5GC) through an N2/N3 interface. 
       FIG. 3  illustrates a protocol stack of an E2 application protocol message in a radio access network according to an embodiment of the disclosure. 
     Referring to  FIG. 3 , a control plane includes a transport network layer and a radio network layer. The transport network layer includes a physical layer  310 , a data link layer  320 , an IP  330 , and a stream control transmission protocol (SCTP)  340 . 
     The radio network layer includes an E2AP  350 . The E2AP  350  is used to deliver a subscription message, an indication message, a control message, a service update message, and a service query message, and is transmitted in a higher layer of the SCTP  340  and the IP  330 . 
       FIG. 4  illustrates an example of a connection between a base station and an RIC in a radio access network according to an embodiment of the disclosure. 
     Referring to  FIG. 4 , an RIC  440  is connected to an O-CU-CP  420 , an O-CU-UP  410 , and an O-DU  430 . The RIC  440  is a device for controlling a RAN node (or a device for performing a RAN function, for example, the O-CU-CP  420 , the O-CU-UP  410 , and the O-DU  430 ). The RIC  440  may be defined as a device for customizing RAN functionality for a new service or regional resource optimization. The RIC  440  may provide functions such as network intelligence (e.g., policy enforcement, handover optimization), resource assurance (e.g., radio-link management, advanced self-organized-network (SON)), resource control (e.g., load balancing, slicing policy). The RIC  440  may communicate with the O-CU-CP  420 , the O-CU-UP  410 , and the O-DU  430 . The RIC  440  may be connected to each node via E2-CP, E2-UP, and E2-DU interfaces. In addition, the interface between the O-CU-CP and the DU and between the O-CU-UP and the DU may be referred to as an F1 interface. In the following description, the DU and the O-DU, the CU-CP and the O-CU-CP, and the CU-UP and the O-CU-UP may be used interchangeably. 
     While  FIG. 4  illustrates one RIC  440 , a plurality of RICs may exist, according to various embodiments. The plurality of the RICs may be implemented with a plurality of hardware located at the same physical location or may be implemented through virtualization using single hardware. 
       FIG. 5  illustrates a configuration of a device according to an embodiment of the disclosure. The structure illustrated in  FIG. 5  may be understood as a configuration of a device having at least one function of the RIC, the O-CU-CP, the O-CU-UP, and the O-DU of  FIG. 5 . A term such as ‘ . . . unit’ or ‘ . . . er’ used hereafter indicates a unit for processing at least one function or operation, and may be implemented using hardware, software, or a combination of hardware and software. 
     Referring to  FIG. 5 , a core network device includes a communication unit  510 , a storage unit  520 , and a control unit  530 . 
     The communication unit  510  provides an interface for performing communication with other devices in the network. That is, the communication unit  510  converts a bit string transmitted from the core network device to another device into a physical signal, and converts a physical signal received from another device into a bit string. That is, the communication unit  510  may transmit and receive signals. Accordingly, the communication unit  510  may be referred to as a modem, a transmitter, a receiver, or a transceiver. In this case, the communication unit  510  enables the core network device to communicate with other devices or systems via a backhaul connection (e.g., wired backhaul or wireless backhaul) or over the network. 
     The storage unit  520  stores data such as a basic program, an application program, and setting information for the operations of the core network device. The storage unit  520  may include a volatile memory, a nonvolatile memory, or a combination of a volatile memory and a nonvolatile memory. The storage unit  520  provides the stored data according to a request of the control unit  530 . 
     The control unit  530  controls general operations of the core network device. For example, the control unit  530  transmits and receives signals through the communication unit  510 . In addition, the control unit  530  records and reads data in and from the storage unit  520 . For doing so, the control unit  530  may include at least one processor. According to various embodiments, the control unit  530  may control the device to carry out operations according to various embodiments explained in the disclosure. 
       FIG. 6  illustrates logical functions related to E2 messages of an E2 node and an RIC in a radio access network according to an embodiment of the disclosure. 
     Referring to  FIG. 6 , an RIC  640  and an E2 node  610  may transmit or receive an E2 message with each other. For example, the E2 node  610  may be an O-CU-CP, an O-CU-UP, an O-DU, or a base station. A communication interface of the E2 node may be determined according to the type of the E2 node  610 . For example, the E2 node  610  may communicate with another E2 node  616  through the E1 interface or the F1 interface. Alternatively, for example, the E2 node  610  may communicate with the E2 node  616  through an X2 interface or an XN interface. Alternatively, for example, the E2 node  610  may perform communication through an S1 interface or a next generation application protocol (NGAP) interface (i.e., an interface between a next generation (NG) RAN node and an AMF). 
     The E2 node  610  may include an E2 node function  612 . The E2 node function  612  is a function corresponding to a specific xApp (application S/W)  646  installed in the RIC  640 . For example, in the KPI monitor, KPI monitor collection S/W may be installed in the RIC  640 , and the E2 node  610  may include the E2 node function  612  which generates KPI parameters, and then forwards an E2 message including the KPI parameters to an E2 termination  642  positioned at the RIC  640 . The E2 node  610  may include the E2 node function  612  which generates KPI parameters and relays an E2 message including the KPI parameters to the E2 termination  642  positioned at the RIC  640 . The E2 termination  642  positioned in the RIC  640 , which is a termination of the RIC  640  for the E2 message, may perform a function of interpreting E2 report/insert messages relayed by the E2 node  610  and relaying them to the xApp  646 . The E2 node  610  may include a radio resource management (RRM)  614 . The E2 node  610  may manage resources provided to the radio network for the terminal. 
     The E2 termination  642  positioned in the RIC  640 , which is the termination of the RIC  640  for the E2 message, may perform a function of interpreting the E2 message forwarded by the E2 node  610  and then relaying it to the xApp  646 . A database (DB)  644  positioned in the RIC  640  may be used for the E2 termination  642  or the xApp  646 . The E2 node  610  shown in  FIG. 6  is a termination of at least one interface, and may be understood as a termination of messages relayed to a terminal, a neighbor base station, and a core network. 
       FIG. 7A  illustrates an example of a signaling procedure between an E2 node and an RIC according to an embodiment of the disclosure. Specifically,  FIG. 7A  illustrates a setup procedure and an RIC subscription message relay procedure of E2 I/F between the E2 node and the RIC. The E2 node  610  is illustrated as the E2 node, and the RIC  640  is illustrated as the RIC. 
     Referring to  FIG. 7A , the E2 node  610  may transmit an E2 setup request message to the RIC  640  in operation  701 . An E2 node function ( 612 ) positioned in the E2 node  610  finds the RIC using an RIC IP address which is set to operations, administration and management (OAM) and transmits the E2 SET UP REQUEST message. The E2 SET UP REQUEST message includes RAN function definition which defines the function of the RAN supported by the E2 node, E2 node ID information, and so on. A RAN function definition value is a value set to the OAM and the RIC may receive information of the set value with the OAM and determine which call processing function the E2 node supports with the RAN function definition value. 
     In operation  703 , the RIC may receive an E2 setup response message from the E2 node. If accepting the E2 SETUP REQUEST message transmitted by the E2 node, the RIC may transmit the E2 SETUP RESPONSE message. 
     In operation  705 , the RIC may transmit a subscription request message to the E2 node. A specific xApp positioned in the RIC requests the RIC E2 termination function to subscribe (or unsubscribe) for a specific RAN function definition function supported by E2. Herein, the subscription request message of operation  705  may be included in the E2 SETUP RESPONSE message of operation  703  and transmitted together, according to an embodiment. For example, the RAN function may include functions of X2AP, F1AP, E1AP, S1AP, and NGAP interfaces, or an internal RAN function for controlling UEs or cells. 
     In operation  707 , the E2 node may transmit a subscription request response to the RIC. The E2 node function of the E2 node decodes the subscription request message, successfully sets the event condition requested by the RIC to the E2 node function and then relays the subscription response to the RIC that the event trigger condition is successfully set. 
     In operation  709 , the E2 node may transmit an E2 RIC indication message to the RIC. If a specific event condition occurs, the E2 node relays the E2 RIC indication message to the RIC. 
     In operation  711 , the E2 node may transmit an E2 service update message to the RIC. If a change occurs in an E2 NODE function capability information element (E2 NodeCapa), the E2 node transmits the changed E2 NodeCapa in the E2 SERVICE UPDATE to the RIC. 
     Referring to  FIG. 7A , the SET UP procedure, the RIC subscription procedure, the RIC indication procedure, and the update message transmission procedure are sequentially described, but various embodiments of the disclosure are not limited to the above-described order and procedures. That is, in some embodiments, the E2 node and the RIC may independently perform the E2 setup procedure of operations  701  through  703 . In some embodiments, the E2 node and the RIC may independently perform the subscription procedure of operations  705  through  707 . Meanwhile, according to another embodiment, the E2 setup response message may include the subscription request message, as described above. In some embodiments, the E2 node and the RIC may independently perform the RIC indication procedure of operation  709 . Further, in some embodiments, the E2 node and the RIC may independently perform the RIC indication procedure of operation  709 . In addition, the E2 node and the RIC may perform at least some of the above-described procedures together or separately. 
       FIG. 7B  illustrates an example of the subscription procedure between the E2 node and the RIC. The E2 node  610  is illustrated as the E2 node, and RIC  640  is illustrated as the RIC according to an embodiment of the disclosure. 
     Referring to  FIG. 7B , in operation  751 , the RIC may request subscription from the E2 termination. For example, the E2 Relay xApp positioned in the RIC may request the subscription for the initial UE message in the NGAP I/F for the E2 Relay message function from the RIC E2 termination function. 
     In operation  753 , the RIC may transmit an RIC subscription request to the E2 node. For example, the RIC E2 termination function generates an initial UE message relay message for the NGAP I/F requested in operation  751  as an E2 subscription request message and relays it to the E2 node. 
     In operation  755 , the E2 node may transmit an RIC subscription response to the RIC. Specifically, the E2 node function of the E2 node receiving the E2 subscription request message may decode the message, successfully set the event condition for transmitting to the RIC in a container including the RIC indication message per UE, per cell or per network slice if the initial UE message occurs in the NGAP I/F, and then relay the subscription response to the RIC that the event trigger condition is successfully set. 
     In operation  757 , the E2 node may transmit an RIC indication to the RIC. If an Initial UE message occurs in the NGAP I/F by the UE, the E2 node may relay the E2 RIC Indication message including the NGAP Initial UE message in the container to the RIC. 
     Some contents described in  FIG. 7A  may be applied to  FIG. 7B  in the same or similar manner. 
       FIG. 8  illustrates IEs of an E2 indication message according to an embodiment of the disclosure. The first IE is Message Type, and Message Type has a unique value for each E2 message. Details of the Message Type are shown in  FIG. 9 . 
     The second IE designates a specific xApp with RIC REQUEST ID. Message details are shown in  FIG. 10 . 
     The third IE is E2 NODE FUNCTION ID. The E2 NODE FUNCTION ID may divide the range value for each E2 node and thus designate a specific E2 NODE FUNCTION to a specific E2 node. Message details are shown in  FIG. 11 . 
     The fourth IE is RIC INDICATION TYPE (or may be expressed as E2 INDICATION TYPE). The RIC INDICATION TYPE designates whether the INDICATION occurrence in the E2 node is REPORT of a specific process or an addition to a message of an existing process. Details of the indication type are shown in  FIG. 12 . 
     The fifth IE allows the E2 message relay container (or may be expressed as RELAY CONTAINER) defined in the disclosure to transmit any type of the message designated in the subscription message in the form of an Octet string. 
     Referring to  FIG. 8 , all are shown to be included as mandatory, but embodiments of the disclosure are not limited thereto. According to another embodiment, at least one of the illustrated IEs functions as optional, and for example, the corresponding IE may be omitted in the RIC indication message. 
       FIG. 9  is details of Message Type IE according to an embodiment of the disclosure. The procedure code value which is the first IE, is an integer value with the range of 0˜255, and a specific MESSAGE TYPE (PROCEDURE CODE) is set. 
     Referring to  FIG. 9 , the procedure code value 0 may be set to subscription, the procedure code value 1 may be set to E2 SETUP configuration, and the procedure code value 2 may be set to the indication request message value from 0 to 255, that is, 256 message value configurations in total. For example, the O-RAN defines Table 1 below. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
             
            
               
                   
                 id-e2Subscription 
                 ProcedureCode ::= 0 
               
               
                   
                 id-e2Setup 
                 ProcedureCode ::= 1 
               
               
                   
                 id-e2Indication 
                 ProcedureCode ::= 2 
               
               
                   
                 id-e2Control 
                 ProcedureCode ::= 3 
               
               
                   
                 id-e2Serviceupdate 
                 ProcedureCode ::= 4 
               
               
                   
                 id-e2Servicequery 
                 ProcedureCode ::= 5 
               
               
                   
                   
               
            
           
         
       
     
     Type of message which is the second IE in Message Type indicates the Message type, and may define initiating, successful, unsuccessful messages. 
       FIG. 10  is an RIC REQUEST ID value according to an embodiment of the disclosure. The RIC Request ID value is an integer value in the range of 0˜65535, and may set a value unique to a specific xApp. 
       FIG. 11  is an E2 NODE FUNCTION ID value according to an embodiment of the disclosure. The E2 NODE FUNCTION ID value is an integer value in the range of 0˜4095, and may be set by dividing the range value per E2 node. 
     
       
         
           
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
             
            
               
                   
                 O-CU-CP (1~512) 
               
               
                   
                 O-CU-UP (513~1024) 
               
               
                   
                 O-DU (1025~1536) 
               
               
                   
                 O-RAN eNB (1537~2048) 
               
               
                   
                   
               
            
           
         
       
     
     The value after  2048  is the reserved value and may be set if an additional E2 node is added. 
       FIG. 12  is E2 INDICATION TYPE value according to an embodiment of the disclosure. The E2 INDICATION TYPE value is a string value in the range of ‘Insert’ and ‘Report’, and may be defined as a service value of the indication message for a specific function of a specific E2 NODE FUNCTION of the E2 node. For example, the I/F-based message relay function may be defined as a REPORT message. 
     Various embodiments of the disclosure may set the event condition in the call processing function (per I/F, per call processing function) of the O-RU, the O-DU, the O-CU-CP or the O-CU-UP with the E2 SUBSCRIPTION message, relay it to the RIC by including the 3GPP message in the container for a specific call processing function or every call processing function generated for each I/F, and thus efficiently provide the call processing request service of the RIC. 
     The methods according to the embodiments described in the claims or the specification of the disclosure may be implemented in software, hardware, or a combination of hardware and software. 
     As for the software, a computer-readable storage medium storing one or more programs (software modules) may be provided. One or more programs stored in the computer-readable storage medium may be configured for execution by one or more processors of an electronic device. One or more programs may include instructions for controlling an electronic device to execute the methods according to the embodiments described in the claims or the specification of the disclosure. 
     Such a program (software module, software) may be stored to a random access memory, a non-volatile memory including a flash memory, a read only memory (ROM), an electrically erasable programmable ROM (EEPROM), a magnetic disc storage device, a compact disc (CD)-ROM, digital versatile discs (DVDs) or other optical storage devices, and a magnetic cassette. Alternatively, it may be stored to a memory combining part or all of those recording media. A plurality of memories may be included. 
     Also, the program may be stored in an attachable storage device accessible via a communication network such as internet, intranet, local area network (LAN), wide LAN (WLAN), or storage area network (SAN), or a communication network by combining these networks. Such a storage device may access a device which executes an embodiment of the disclosure through an external port. In addition, a separate storage device on the communication network may access the device which executes an embodiment of the disclosure. 
     In the specific embodiments of the disclosure, the components included in the disclosure are expressed in a singular or plural form. However, the singular or plural expression is appropriately selected according to a proposed situation for the convenience of explanation, the disclosure is not limited to a single component or a plurality of components, the components expressed in the plural form may be configured as a single component, and the components expressed in the singular form may be configured as a plurality of components. 
     While the disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents.