Patent Publication Number: US-2021168588-A1

Title: User equipment, network device, and radio communication method

Description:
TECHNICAL FIELD 
     The present invention relates to a user equipment that operates as any one of a plurality of categories according to capability, a network device, and a radio communication method. 
     BACKGROUND ART 
     The 3rd Generation Partnership Project (3GPP) specifies Long Term Evolution (LTE) and specifies LTE-Advanced (hereinafter referred to as LTE including LTE-Advanced) for the purpose of speeding up LTE. In addition, in the 3GPP, specifications for a successor system of LTE, called 5G New Radio (NR), are also being studied. 
     In LTE Release-13 or later, categories (UE categories) for inexpensive terminals (user equipments) such as Internet of Things (IoT) modules are defined. Specifically, the categories M1 and M2 (hereinafter referred to as Cat.M) are specified. These categories are also referred to as LTE-M or enhanced Machine Type Communication (eMTC). 
     Since a user equipment that operates as Cat.M has restricted capability (communication speed, etc.) as compared to a user equipment (smartphone, etc.) that operates as a normal category (Cat. 4-6, etc.), there is a need to differentiate in terms of price. However, in a conventional LTE Release (Release-14) specification, a core network cannot determine whether a user equipment is operating as Cat.M (restricted category). 
     Thus, it has been proposed that a radio base station (eNB) determines a category of a user equipment based on a cell type in which the user equipment resides when attaching to a core network (see Non Patent Document 1). The eNB notifies the core network (specifically, Mobility Management Entity (MME)) that the user equipment is operating as Cat.M. 
     CITATION LIST 
     Non Patent Literature 
     
         
         Non Patent Literature 1: “Identification of LTE-M (eMTC) traffic”, S2-182412, 3GPP TSG-SA2 Meeting #126, 3GPP, February 2018 
       
    
     SUMMARY OF INVENTION 
     However, the above-described method of notifying the category (Cat.M) to the core network by the eNB has the following problems. Specifically, if the user equipment has capabilities of both Cat.M and the normal category, the user equipment can switch the categories after attaching to the core network. 
     Therefore, if such category switching occurs, there is a problem that the above-described notification method cannot cope with. 
     Therefore, the present invention has been made in view of such a circumstance, and an object of the present invention is to provide: a user equipment that can reliably notify a category of an operating UE to a core network or the like even if having capability of a plurality of UE categories including Cat.M; a network device; and a radio communication method. 
     According to one aspect of the present invention, a user equipment (UE  200 ) operating as any one of a plurality of categories according to capability includes: an attach processing unit (attach processing unit  220 ) that performs attaching to a core network; an operation control unit (operation control unit  230 ) that causes the user equipment to operate as a restricted category (Cat.M, LTE-M, or eMTC) whose capability is restricted as compared to a normal category; and a category notification unit (category notification unit  240 ) that notifies the core network of a category in which the user equipment is operating at the time of the attaching or after the attaching. 
     According to one aspect of the present invention, a network device (for example, MME  300 ) constituting a core network includes: a category reception unit (category reception unit  301 ) that receives, from a user equipment (UE  200 ) operating as any one of a plurality of categories according to capability, a category in which the user equipment is operating; and a category transfer unit (category transfer unit  305 ) that transfers the category received by the category reception unit to another network device (S-GW  310 ) or a charging system. 
     According to one aspect of the present invention, a radio communication method, which is performed by a user equipment operating as any one of a plurality of categories according to capability, includes: a step of causing the user equipment to operate as a restricted category whose capability is restricted as compared to a normal category; and a step of causing the user equipment to notify a core network of a category in which the user equipment is operating at the time of attaching to the core network or after the attaching. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an overall schematic configuration diagram of a radio communication system  10 . 
         FIG. 2  is a functional block configuration diagram of a UE  200 . 
         FIG. 3  is a functional block configuration diagram of an MME  300  and an S-GW  310 . 
         FIG. 4  is a functional block configuration diagram of a P-GW  320 . 
         FIG. 5  is a diagram illustrating a sequence of notifying a core network of a category in which the UE  200  is operating. 
         FIG. 6  is a diagram illustrating a schematic configuration example of a NAS message that the UE  200  transmits toward the core network. 
         FIG. 7  is a diagram illustrating a schematic configuration example of a message that the P-GW  320  transmits toward an OCS/OFCS  400 . 
         FIG. 8  is a diagram illustrating an example of a hardware configuration of the UE  200 , the MME  300 , the S-GW  310 , and the P-GW  320 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments will be described with reference to the drawings. It should be noted that the same functions or configurations are denoted by the same or similar reference numerals, and a description thereof will be omitted as appropriate. 
     (1) Overall Schematic Configuration of Radio Communication System 
       FIG. 1  is an overall schematic configuration diagram of a radio communication system  10  according to the present embodiment. The radio communication system  10  is a radio communication system in accordance with Long Term Evolution (LTE) and includes a radio access network  20  and a user equipment  200  (hereinafter, UE  200 ). 
     The radio access network  20  is an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) defined in the 3GPP and includes a radio base station  100  (hereinafter, eNB  100 ). 
     It should be noted that the radio communication system  10  is not necessarily limited to LTE (E-UTRAN). For example, the radio access network  20  may be a radio access network including a radio base station that performs radio communication with the UE  200  (user equipment) defined as 5G. 
     The eNB  100  and the UE  200  perform radio communication in accordance with the specification of LTE. In particular, in the present embodiment, the UE  200  operates as a category (UE category) for an inexpensive terminal (user equipment) such as an Internet of Things (IoT) module. 
     Specifically, the UE  200  can operate as categories M1 and M2 (hereinafter, Cat.M). It should be noted that Cat.M is also referred to as LTE-M or eMTC (hereinafter, LTE-M or eMTC is also used as appropriate). 
     In addition, in the present embodiment, the UE  200  can also operate as a normal UE category (normal category), and specifically, Cat. 4-6 or the like. That is, the UE  200  can operate as any one of a plurality of categories according to the capability of the user equipment including radio capability (communication speed, etc.). 
     The eNB  100  can form a plurality of cells according to the UE category. In the present embodiment, the eNB  100  forms a cell C 1  for the normal category (Cat. 4-6, etc.) and a cell C 2  for Cat.M1. 
     A Mobility Management Entity  300  (hereinafter, MME  300 ) is connected to the radio access network  20 . The MME  300  accommodates the eNB  100  and provides mobility control of the UE  200  and the like. 
     The Serving Gateway  310  (hereinafter, S-GW  310 ) is connected to the MME  300 . In addition, a Packet Data Network Gateway  320  (hereinafter, P-GW  320 ) is connected to the S-GW  310 . The MME  300 , the S-GW  310 , and the P-GW  320  constitute the core network. 
     The S-GW  310  performs transfer of a user data packet to the UE  200  and the like. The P-GW  320  is provided at a point of connection with a Packet Data Network (PDN) that is an external network, and performs assignment of an IP address for the UE  200 , transfer of a packet to the S-GW  310 , and the like. 
     An Online Charging System/Offline Charging System  400  (hereinafter, OCS/OFCS  400 ) perform charging processing associated with provision of communication services for the UE  200 . The OCS/OFCS  400  acquires a communication state of the UE  200  and performs charging processing according to service contents. In the present embodiment, the OCS/OFCS  400  constitutes a charging system. 
     (2) Functional Block Configuration of Radio Communication System 
     Next, the functional block configuration of the radio communication system  10  will be described. Specifically, the functional block configurations of the UE  200 , the MME  300 , the S-GW  310 , and the P-GW  320  will be described. Hereinafter, only portions related to the features of the present embodiment will be described. Therefore, it is obvious that the device includes other functional blocks that are not directly related to the features of the present embodiment. 
     (2.1) UE  200   
       FIG. 2  is a functional block configuration diagram of the UE  200 . As illustrated in  FIG. 2 , the UE  200  includes a radio communication unit  210 , an attach processing unit  220 , an operation control unit  230 , and a category notification unit  240 . 
     The radio communication unit  210  performs radio communication in accordance with an LTE scheme. Specifically, the radio communication unit  210  transmits and receives radio signals with the eNB  100  in accordance with the LTE scheme. 
     The attach processing unit  220  performs attaching to the core network. Specifically, the attach processing unit  220  performs attach processing to the core network by transmitting an attach request to the MME  300 . In addition, the attach processing unit  220  receives, from the core network, an attach accept indicating that the attach request has been accepted. 
     The attach request and the attach accept are a type of a Non-Access Stratum (NAS) message and are defined in 3GPP TS24.301. 
     The operation control unit  230  controls the operation of the UE  200 . In particular, in the present embodiment, the operation control unit  230  controls which UE category the UE  200  operates as. 
     Specifically, the operation control unit  230  can cause the UE  200  to operate as Cat.M1 (restricted category) whose capability is restricted as compared to the normal category (Cat. 4-6, etc.). It is obvious that the operation control unit  230  can also cause the UE  200  to operate in any UE category of Cat. 4-6. 
     The operation control unit  230  can switch the category of the UE  200  between the normal category and the restricted category. However, the UE  200  may be a user equipment dedicated to Cat.M, without corresponding to the normal category. 
     The category notification unit  240  notifies the core network of the category of the UE  200 . Specifically, the category notification unit  240  notifies the core network of the category in which the UE  200  is operating. 
     As described above, the UE  200  can operate as any one of a plurality of categories (normal category or restricted category). The category notification unit  240  notifies the core network of the UE category in which the UE  200  is currently operating, based on the control result obtained by the operation control unit  230 . 
     When attaching to the core network by the attach processing unit  220 , the category notification unit  240  can notify the core network of the category in which the UE  200  is operating. In addition, after attaching, the category notification unit  240  can also notify the core network of the category in which the UE  200  is operating. 
     Specifically, when the category of the UE  200  is switched by the operation control unit  230 , the category notification unit  240  can notify the core network of the category in which the UE  200  is operating. 
     Alternatively, when the UE  200  resides in a cell for Cat.M1 (cell C 2 ), the category notification unit  240  may notify the core network of the category in which the UE  200  is operating, that is, Cat.M1. 
     The category notification unit  240  uses the NAS message to notify the MME  300  of the UE category in which the UE  200  is operating. The attach request can be used when attaching to the core network. After attaching, service request (see chapter 8.2.25 of TS24.301), tracking area update complete (see chapter 8.2.27 of TS 24.301), and the like can be used according to a category switching timing of the UE  200  by the operation control unit  230 . Alternatively, a new NAS message that notifies the UE category in which the UE  200  is operating may be used. 
       FIG. 6  illustrates a schematic configuration example of a NAS message that the UE  200  transmits toward the core network. 
     As illustrated in  FIG. 6 , a message M 1 , which is a NAS message, includes a UE identifier (for example, EPS mobile identity) that can uniquely identify the UE  200 , and information (Cat.M1) about the category in which the UE  200  is operating. It is obvious that, in practice, the message M 1  includes much more elements (see, for example, chapter 8.2.4 of 3GPP TS24.301 in the case of attach request). 
     (2.2) MME  300  and S-GW  310   
       FIG. 3  is a functional block configuration diagram of the MME  300  and the S-GW  310 . That is, the MME  300  and the S-GW  310  have the same functional block configuration with respect to the characteristic parts in the present embodiment. Hereinafter, the MME  300  will be described as an example. 
     As illustrated in  FIG. 3 , the MME  300  includes a category reception unit  301 , a session communication unit  303 , a category transfer unit  305 , and a priority processing unit  307 . 
     The category reception unit  301  receives, from the UE  200 , a category in which the UE  200  is operating. Specifically, the category reception unit  301  acquires category information (see  FIG. 6 ) included in the NAS message transmitted from the UE  200 . 
     The session communication unit  303  establishes a Non-Access Stratum (NAS) session necessary for communication with the UE  200 , and performs communication via the corresponding session. In addition, the session communication unit  303  establishes a GPRS Tunneling Protocol (GTP) session necessary for communication with the S-GW  310 , and performs communication via the corresponding session. 
     The category transfer unit  305  transfers the category of the UE  200  received by the category reception unit  301  to the S-GW  310  (another network device). Specifically, the category transfer unit  305  transfers the category of the UE  200  to the S-GW  310  via the GTP session established by the session communication unit  303 . 
     The configuration of the message transferred to the S-GW  310  by the category transfer unit  305  is substantially the same as the NAS message (message M 1 ) illustrated in FIG.  6 . 
     The priority processing unit  307  performs priority processing for the UE  200 . For example, if the category in which the UE  200  is operating is Cat.M1, the priority processing unit  307  can perform packet transfer for the UE  200  with higher priority than the user equipment of the normal category. 
     Alternatively, if the category in which the UE  200  is operating is Cat.M 1 , the priority processing unit  307  can perform packet transfer for the UE  200  with lower priority than the user equipment of the normal category. 
     It should be noted that, in the case of the S-GW  310 , the session communication unit  303  establishes a GTP session with the MME  300  and the P-GW  320 , and the category transfer unit  305  transfers the category of the UE  200  to the P-GW  320 . 
     (2.3) P-GW  320   
       FIG. 4  is a functional block configuration diagram of the P-GW  320 . As illustrated in  FIG. 4 , the P-GW  320  includes a category reception unit  321 , a session communication unit  323 , a priority processing unit  325 , and a detailed information transmission unit  327 . 
     The category reception unit  321  receives, from the S-GW  310 , the category in which the UE  200  is operating. Specifically, the category reception unit  321  acquires category information included in a message via the GTP session transmitted from the S-GW  310 . 
     The session communication unit  323  establishes a GTP session with the S-GW  310 . In addition, the session communication unit  323  establishes a GTP session necessary for communication with the OCS/OFCS  400 . It should be noted that the session communication unit  323  may establish a File Transfer Protocol (FTP) session with the OCS/OFCS  400 . 
     The priority processing unit  325  performs priority processing for the UE  200 . The priority processing unit  325  provides the same function as the priority processing unit  307  of the MME  300  (S-GW  310 ). 
     The detailed information transmission unit  327  transmits detailed information to the OCS/OFCS  400 . The detailed information indicates usage details of communication service by the UE  200  (communication service type (including a type of Cat.M or the normal category), communication time, packet amount, etc.). 
       FIG. 7  illustrates a schematic configuration example of a message that the P-GW  320  transmits toward the OCS/OFCS  400 . 
     As illustrated in  FIG. 7 , a message M 2 , which is transmitted via the GTP session (or the FTP session), includes a UE identifier (for example, EPS mobile identity) that can uniquely identify the UE  200 , detailed information, and information (Cat.M1) about the category in which the UE  200  is operating. 
     The OCS/OFCS  400  that receives the message M 2  uses information about the category to perform charging processing according to a usage situation of the communication service by the UE  200 . 
     (3) Operation of Radio Communication System 
     Next, the operation of the radio communication system  10  will be described. Specifically, the operation of notifying the core network of the category in which UE  200  is operating will be described. 
       FIG. 5  illustrates a sequence of notifying the core network of the category in which the UE  200  is operating. As illustrated in  FIG. 5 , the eNB  100  and the UE  200  exchange radio information about a cell in which the UE  200  resides (S 10 ). 
     Here, it is assumed that the UE  200  resides in a Cat.M1 cell (cell C 2 ). The eNB  100  and the UE  200  secure a radio resource according to Cat.M1 and perform establishment of a radio bearer between the eNB  100  and the UE  200 , and the like. Thereby, radio communication between the eNB  100  and the UE  200  is enabled. 
     The UE  200  configures the category (UE category) of the UE  200  to Cat.M1 in association with the residence in the Cat.M1 cell (cell C 2 ) (S 20 ). It should be noted that, in  FIG. 5 , “LTE-M” is used for the purpose of including restricted categories (Cat.M2, etc.) other than Cat.M1. 
     The UE  200  transmits the NAS message (see  FIG. 6 ) to the MME  300  (S 30 ). As described above, when attaching to the core network, the UE  200  transmits the attach request to the MME  300 . The attach request includes information (LTE-M) about the category in which the UE  200  is operating. 
     In addition, the UE  200  may transmit the NAS message to the MME  300  after attaching to the core network. As described above, examples of the NAS message include service request and tracking area update complete according to the category switching timing of the UE  200 . 
     The MME  300  transfers, to the S-GW  310 , the category (LTE-M) included in the NAS message received from the UE  200  (S 40 ). Specifically, the MME  300  transfers the message including the category to the S-GW  310  via the GTP session. 
     In addition, the MME  300  may perform priority processing with respect to the UE  200  based on the received category. As described above, the priority processing includes increasing or decreasing the priority of the packet transfer for the UE  200 . 
     Similarly, the S-GW  310  transfers, to the P-GW  320 , the category (LTE-M) included in the message received from the MME  300  (S 50 ). Specifically, the S-GW  310  transfers the message including the category to the P-GW  320  via the GTP session. In addition, the S-GW  310  may also perform the priority processing with respect to the UE  200  based on the received category. 
     The P-GW  320  transmits the detailed information about the UE  200  to the OCS/OFCS  400  (S 60 ). Specifically, the P-GW  320  adds, to the detailed information, the category (LTE-M) included in the message transferred from the S-GW  310 . 
     The P-GW  320  transmits a message (see  FIG. 7 ) including the category and the detail information to the OCS/OFCS  400 . In addition, the P-GW  320  may also perform the priority processing with respect to the UE  200  based on the received category. 
     The OCS/OFCS  400  uses information about the category to perform charging processing according to a usage situation of the communication service by the UE  200 . That is, since the OCS/OFCS  400  can recognize in which category the UE  200  is operating in substantially real time, a specific charging plan for the category (LTE-M) can be applied. 
     (4) Operation and Effect 
     According to the above-described embodiment, the following effects can be obtained. Specifically, the UE  200  notifies the core network of the category (LTE-M) in which the UE  200  is operating. In particular, the UE  200  can notify the core network of the category in which the UE  200  is operating at the time not only even when attaching to the core network but also even after attaching. 
     Thus, even when the category of the UE  200  is switched after attaching to the core network, the category in which UE  200  is operating after the switching can be reliably notified to the core network. 
     Such an event may occur when the UE  200  can operate in any one of a plurality of categories, but even in such a case, the UE  200  can reliably notify the core network of the operating category. 
     In addition, the MME  300 , the S-GW  310 , and the P-GW  320  constituting the core network can sequentially transfer information indicating the category and notify the OCS/OFCS  400  of the category. 
     That is, according to the radio communication system  10 , even if the UE  200  has capabilities of a plurality of UE categories including Cat.M (LTE-M, eMTC, etc.), the UE  200  can reliably notify the core network of the operating UE category. In addition, the core network can reliably notify the OCS/OFCS  400  of the UE category. 
     Furthermore, the OCS/OFCS  400  can apply a charging policy or the like according to the category based on the information about the category. Thereby, it is possible to differentiate charging policies for the user equipment operating as the normal category and the user equipment operating as Cat.M (LTE-M, eMTC, etc.). 
     In the present embodiment, when the category of the UE  200  is switched, the UE  200  can notify the core network of the category in which the UE  200  is operating. Therefore, the core network and the OCS/OFCS  400  can recognize in which category the UE  200  is operating in substantially real time. Thereby, it is possible to differentiate fine services and charging policies based on the category in which the UE  200  is currently operating. 
     In the present embodiment, when the UE  200  resides in the Cat.M1 cell (cell C 2 ), the category (Cat.M1) in which the previous UE  200  is operating can be notified to the core network. Therefore, when the UE  200  attaches to the core network or even when the category is switched after attaching, the category in which the UE  200  is operating can be detected by a common scheme. Thereby, the implementation of the UE  200  can be simplified. 
     In the present embodiment, the UE  200  uses the NAS message to notify the core network of the UE category in which the UE  200  is operating. Therefore, while using an existing NAS message, the category in which the UE  200  is operating can be notified to the core network. Thereby, the implementation of the UE  200  can be simplified. 
     (5) Other Embodiments 
     Although the contents of the present invention have been described along with the embodiment, the present invention is not limited to these descriptions, and it will be obvious to those skilled in the art that various modifications and improvements can be made thereto. 
     In the above-described embodiment, the UE  200  transmits, to the MME  300 , the NAS message including the category in which the UE  200  is operating, and the MME  300 , the S-GW  310 , and the P-GW  320  sequentially transfer the category. However, the UE  200  may directly transmit a message including the category to the S-GW  310  or the P-GW  320 , instead of the MME  300 , according to the type of the message. 
     In the above-described embodiment, the P-GW  320  establishes the GTP or FTP session with the OCS/OFCS  400 , but the session established between the P-GW  320  and the OCS/OFCS  400  is not limited to the GTP or the FTP. That is, sessions other than the GTP or the FTP may be used as long as the message M 2  (see  FIG. 7 ) including the UE identifier, the detailed information, and the category information can be transmitted. 
     In the above-described embodiment, Cat.M (LTE-M, eMTC, etc.) has been described as an example, but if it is a category for IoT that is different from the normal category (Cat. 4-6, etc.), the present invention is not limited to these categories. For example, there may be a category for Narrow Band (NB)-IoT. 
     Furthermore, the block configuration diagrams used for explaining the above-described embodiment ( FIGS. 2 to 4 ) illustrate the functional blocks. Those functional blocks (structural components) can be realized by a desired combination of hardware and/or software. Means for realizing each functional block is not particularly limited. That is, each functional block may be realized by one device combined physically and/or logically. Alternatively, two or more devices separated physically and/or logically may be directly and/or indirectly connected (for example, wired, or wireless) to each other, and each functional block may be realized by these plural devices. 
     Furthermore, the UE  200 , the MME  300 , the S-GW  310 , and the P-GW  320  (device) described above may function as a computer that performs the processing of the present invention.  FIG. 8  is a diagram illustrating an example of a hardware configuration of the device. As illustrated in  FIG. 8 , the device can be configured as a computer device including a processor  1001 , a memory  1002 , a storage  1003 , a communication device  1004 , an input device  1005 , an output device  1006 , a bus  1007 , and the like. 
     The functional blocks of the device (see  FIGS. 2 to 4 ) can be realized by any of hardware elements of the computer device or a desired combination of the hardware elements. 
     The processor  1001 , for example, operates an operating system to control the entire computer. The processor  1001  can be configured with a central processing unit (CPU) including an interface with a peripheral device, a control device, a computing device, a register, and the like. 
     The memory  1002  is a computer readable recording medium and is configured, for example, with at least one of Read Only Memory (ROM), Erasable Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), Random Access Memory (RAM), and the like. The memory  1002  can be called register, cache, main memory (main storage device), and the like. The memory  1002  can store a program (program code), a software module, and the like that can perform the above-described method according to the embodiment. 
     The storage  1003  is a computer readable recording medium. Examples of the storage  1003  include at least one of an optical disk such as Compact Disc ROM (CD-ROM), a hard disk drive, a flexible disk, a magneto-optical disk (for example, a compact disk, a digital versatile disk, Blu-ray (Registered Trademark) disk), a smart card, a flash memory (for example, a card, a stick, a key drive), a floppy (Registered Trademark) disk, a magnetic strip, and the like. The storage  1003  can be called an auxiliary storage device. The recording medium can be, for example, a database including the memory  1002  and/or the storage  1003 , a server, or other appropriate medium. 
     The communication device  1004  is hardware (transmission/reception device) capable of performing communication between computers via a wired and/or wireless network. The communication device  1004  is also called, for example, a network device, a network controller, a network card, a communication module, and the like. 
     The input device  1005  is an input device (for example, a keyboard, a mouse, a microphone, a switch, a button, a sensor, and the like) that accepts input from the outside. The output device  1006  is an output device (for example, a display, a speaker, an LED lamp, and the like) that outputs data to the outside. Note that, the input device  1005  and the output device  1006  may be integrated (for example, a touch screen). 
     In addition, the respective devices, such as the processor  1001  and the memory  1002 , are connected to each other with the bus  1007  for communicating information thereamong. The bus  1007  can be constituted by a single bus or can be constituted by separate buses between the devices. 
     In addition, the notification of information is not limited to that explained in the above embodiment, and may be performed by other methods. For example, the notification of information may be performed by physical layer signaling (for example, Downlink Control Information (DCI), Uplink Control Information (UCI), higher layer signaling (for example, RRC signaling, Medium Access Control (MAC) signaling, broadcast information (Master Information Block (MIB), System Information Block (SIB)), other signals, or a combination of these. The RRC signaling may be called RRC message, for example, or can be RRC Connection Setup message, RRC Connection Reconfiguration message, or the like. 
     The input/output information can be stored in a specific location (for example, a memory) or can be managed in a management table. The information to be input/output can be overwritten, updated, or added. The information can be deleted after outputting. The inputted information can be transmitted to another device. 
     As long as there is no inconsistency, the order of sequences, flowcharts, and the like of the above-described embodiment may be exchanged. 
     In the above-described embodiment, specific operations that are performed by the MME  300 , the S-GW  310 , and the P-GW  320  can be performed by another network nod (device). Furthermore, the function of the MME  300 , the S-GW  310 , or the P-GW  320  can be provided by a combination of a plurality of other network nodes. 
     It should be noted that the terms described in the present specification and/or terms necessary for understanding the present specification may be replaced by terms having the same or similar meanings. For example, if there is a corresponding description, a channel and/or a symbol may be a signal. Also, a signal may be a message. In addition, the terms “system” and “network” can be used interchangeably. 
     Furthermore, the parameter and the like can be represented by an absolute value, can be represented by a relative value from a predetermined value, or can be represented by corresponding other information. For example, the radio resource can be instructed by an index. 
     The eNB  100  (base station) can accommodate one or more (for example, three) cells (also called sectors). In a configuration in which the base station accommodates a plurality of cells, the entire coverage area of the base station can be divided into a plurality of smaller areas. In each such a smaller area, communication service can be provided by a base station subsystem (for example, a small base station for indoor use (Remote Radio Head: RRH)). 
     The term “cell” or “sector” refers to a part or all of the coverage area of a base station and/or a base station subsystem that performs communication service in this coverage. 
     Furthermore, the terms “base station”, “eNB”, “cell”, and “sector” can be used interchangeably in the present specification. The base station can also be referred to with the terms such as a fixed station, a NodeB, an eNodeB (eNB), a gNodeB (gNB), an access point, a femtocell, or a small cell. 
     The UE  200  may be called by those skilled in the art as a subscriber station, a mobile unit, a subscriber unit, a radio unit, a remote unit, a mobile device, a radio device, a radio communication device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a radio terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or with some other suitable term. 
     As used in the present specification, the phrase “based on” does not mean “based only on” unless explicitly stated otherwise. In other words, the phrase “based on” means both “based only on” and “based at least on”. 
     In addition, the terms “including”, “comprising”, and variants thereof are intended to be inclusive in a manner similar to the term “comprising”. Furthermore, the term “or” used in the present specification or the claims is intended not to be an exclusive OR. 
     Any reference to an element using a designation such as “first”, “second”, and the like used in the present specification generally does not limit the amount or order of those elements. Such designations can be used in the present specification as a convenient way to distinguish between two or more elements. Thus, the reference to the first and second elements does not imply that only two elements can be adopted, or that the first element must precede the second element in some or the other manner. 
     Throughout the present specification, for example, during translation, if articles such as “a”, “an”, and “the” in English are added, these articles are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     As described above, the embodiments of the present invention have been described, but it should not be understood that the description and drawings constituting a part of this disclosure limit this invention. From this disclosure, various alternative embodiments, examples, and operational technologies will become apparent to those skilled in the art. 
     REFERENCE SIGNS LIST 
       10  radio communication system 
       20  radio access network 
       100  eNB 
       200  UE 
       210  radio communication unit 
       220  attach processing unit 
       230  operation control unit 
       240  category notification unit 
       300  MME 
       301  category reception unit 
       303  session communication unit 
       305  category transfer unit 
       307  priority processing unit 
       310  S-GW 
       320  P-GW 
       321  category reception unit 
       323  session communication unit 
       325  priority processing unit 
       327  detailed information transmission unit 
       400  OCS/OFCS 
       1001  processor 
       1002  memory 
       1003  storage 
       1004  communication device 
       1005  input device 
       1006  output device 
       1007  bus