Mobile communication network

Abstract

According to the present invention, a mobile communication network that communicates with a plurality of wireless devices belonging to the same group comprises a plurality of base stations and is configured to maintain a connection for the group between each of a plurality of first base stations among the plurality of base stations and a network node connected to an external network. Each of the plurality of first base stations stores the context of the group and an identifier of the context.

Description

Mobile communication network

[0001] The present disclosure relates to mobile communication networks.

[0002] In order to improve the accommodation efficiency of wireless devices (WDs) for machine type communication (MTC), Non-Patent Document 1 discloses a configuration in which such WDs are grouped and the same international mobile subscriber identity (IMSI) is assigned to multiple WDs in the same group. In the following description, WDs for MTC are also simply referred to as "WDs."

[0003] M. Ito, et. al. , "Reducing state information by sharing IMSI for cellular IoT devices", IEEE IoT J. ,2016

[0004] Figure 1 is an explanatory diagram outlining the configuration disclosed in Non-Patent Document 1. WD#1 to WD#4 belong to the same group and therefore have the same IMSI. In Figure 1, WD#1 and WD#2 are in a cell served by base station (BS)#1, and WD#3 and WD#4 are in a cell served by BS#2. BS#1 and BS#2 are connected to a core network.

[0005] For example, when data to be transmitted to WD#1 occurs, WD#1 transmits an RRC connection setup request message including a service request message to BS#1. BS#1 then transmits the service request message included in the RRC connection setup request message to the Access and Mobility Management Function (AMF) of the core network. This triggers the establishment of a protocol data unit (PDU) session between WD#1 and the User Plane Function (UPF). Note that, to establish the PDU session, control messages are transmitted and received between the AMF, the Session Management Function (SMF), and the UPF. After the PDU session is established, WD#1 transmits data via the PDU session. After the data transmission is completed, WD#1 transitions to an idle state.

[0006] Since WD#1 to WD#4 share the same IMSI, WD#2 to WD#4 cannot communicate when WD#1 is in communication. However, since the communication frequency and communication period of the MTC WDs are short, the probability of communication collision is low.

[0007] However, in the configuration of Non-Patent Document 1, when data to be transmitted to the WD occurs, as described above, it is necessary to establish a PDU session by transmitting and receiving control messages between the BS, AMF, SMF, and UPF, which increases the time from when data to be transmitted occurs to when the data is actually transmitted.

[0008] According to one aspect of the present disclosure, a mobile communication network that communicates with multiple wireless devices belonging to the same group includes multiple base stations and is configured to maintain a connection for the group between each of multiple first base stations among the multiple base stations and a network node connected to an external network, and each of the multiple first base stations stores a context for the group and an identifier of the context.

[0009] According to the present disclosure, it is possible to prevent a long time from elapsed between when data to be transmitted to wireless devices belonging to the same group is generated and when the data is transmitted.

[0010] Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which the same or similar elements are designated by the same reference numerals.

[0011] 1 is an explanatory diagram of the background art; a configuration diagram of a mobile communication network according to an embodiment; an explanatory diagram of information stored in a WD and a BS; a sequence diagram when data to be transmitted to a WD occurs; a configuration diagram for setting up an N3 tunnel between a BS and a UPF; and a sequence diagram for setting up an N3 tunnel between a BS and a UPF.

[0012] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more of the features described in the embodiments may be arbitrarily combined. Furthermore, the same reference numerals are used for the same or similar components, and redundant explanations will be omitted.

[0013] FIG. 2 is an explanatory diagram of a mobile communication network according to this embodiment. In FIG. 2, WDs A1, A2, A3, and A4 belong to the same group A and have the same IMSI A. Also, in FIG. 2, WDs B1 and B2 belong to the same group B and have the same IMSI B. According to FIG. 2, WDs A1, A2, and B1 are located in a cell provided by BS 1, while WDs A3, A4, and B2 are located in a cell provided by BS 2. WDs A1 to A4 and B1 and B2 may be wireless devices such as machine-type communication (MTC) or Internet of Things (IoT) devices. The groups are determined based on the operators providing services using each WD, the service content, etc. For example, group #A is a group of wireless devices that are attached to an electric meter and report electricity usage, and group #B is a group of wireless devices that are attached to a gas meter and report gas usage. The groups can be further classified by area, such as the Kanto region, the Kinki region, etc.

[0014] In this embodiment, each WD belonging to a group is configured to transition between a connected state (RRC_CONNCTED) and an inactive state (RRC_INACTIVE), but not to transition to an idle state (RRC_IDLE). In Fig. 2, WDs #A1 to #A4 belonging to group #A and WDs #B1 and #B2 belonging to group #B are all in the inactive state.

[0015] In response to the WDs belonging to a group not transitioning to the idle state, the mobile communication network also establishes and maintains an N3 tunnel for each group between the UPF and each BS. The N3 tunnel is a "connection" established in a PDU session between the UPF and each BS, which connects to a data network (DN). The UPF is a user plane network node, and the DN is an external network, such as the Internet, as seen from the mobile communication network. According to FIG. 2 , the N3 tunnel #A1 is used for a PDU session for WDs #A1 and #A2 of group #A camped in a cell that is an area served by BS #1, and the N3 tunnel #B1 is used for a PDU session for WD #B1 of group #B camped in a cell served by BS #1. Similarly, the N3 tunnel #A2 is used for a PDU session for WDs #A3 and #A4 of group #A camped in a cell served by BS #2, and the N3 tunnel #B2 is used for a PDU session for WD #B2 of group #B camped in a cell served by BS #2.

[0016] In Fig. 2, BS#1 and BS#2 establish an N3 tunnel with the same UPF, but the UPF that establishes the N3 tunnel may be different for each BS. That is, the UPF that establishes N3 tunnel #A1 with BS#1 may be different from the UPF that establishes N3 tunnel #A2 with BS#2. Furthermore, the UPF that sets up the N3 tunnel may be different for each group. For example, the UPF that establishes N3 tunnel #A1 with BS#1 may be different from the UPF that establishes N3 tunnel #B1 with BS#1.

[0017] When a WD transitions from a connected state to an inactive state, the BS (last BS) that was connected to the WD notifies the WD of an inactive-radio network temporary identifier (I-RNTI) and a message authentication code-integrity (MAC-I) and stores the user equipment (UE) context of the WD. The WD in the inactive state stores the I-RNTI and MAC-I.

[0018] The I-RNTI is a combination of the WD's identifier and the identifier of the last BS. The MAC-I is an authentication code generated based on the UE context of the WD maintained in the last BS. When the WD transitions from an inactive state to a connected state, it sends an RRC resumption request including the MAC-I and I-RNTI to the BS. The BS that receives this RRC resumption request determines the last BS based on the I-RNTI and obtains the UE context of the WD from the last BS. The BS then authenticates the WD based on the obtained UE context and the MAC-I received from the WD.

[0019] In this embodiment, UE contexts for multiple WDs belonging to the same group and I-RNTIs for identifying the UE contexts are determined in advance. Furthermore, a MAC-I for the group is obtained based on the UE contexts determined for the group. For example, as shown in FIG. 3 , for group #A, context #A is generated as the UE context, I-RNTI#A is assigned as the I-RNTI for identifying context #A, and MAC-I#A is generated based on context #A. Similarly, for group #B, context #B is generated as the UE context, I-RNTI#B is assigned as the I-RNTI for identifying context #B, and MAC-I#B is generated based on context #B.

[0020] Then, WDs #A1 to #A4 belonging to group #A store MAC-I #A and I-RNTI #A in advance, and WDs #B1 and #B2 belonging to group #B store MAC-I #B and I-RNTI #B in advance.

[0021] Furthermore, BSs #1 and #2 that provide services to the cells (areas) where WDs #A1 to #A4 belonging to group #A are located store context #A of group #A in association with I-RNTI #A, which is the identifier of context #A. Similarly, BSs #1 and #2 that provide services to the cells (areas) where WDs #B1 and #B2 belonging to group #B are located store context #B for WDs of group #B in association with I-RNTI #B, which is the identifier of context #B.

[0022] In summary, the mobile communication network always maintains an N3 tunnel for a group that connects a BS in whose cell a WD belonging to the group is located and a UPF, and the BS in whose cell a WD belonging to the group is located stores the UE context of the group in association with the I-RNTI of the group. Also, the WD belonging to the group stores the I-RNTI and MAC-I of the group.

[0023] In this embodiment, the UE context and I-RNTI of a group are stored in a BS in whose cell a WD belonging to the group is located, and an N3 tunnel is established. However, for example, in consideration of the addition or movement of WDs belonging to the group, the UE context and I-RNTI of the group can also be stored in a BS in whose cell a WD belonging to the group is not located, and an N3 tunnel can be established. In other words, the BSs that establish an N3 tunnel for a group and store the UE context and I-RNTI of the group include at least BSs that provide services to cells in which WDs belonging to the group are located, but can also include BSs in whose cells a WD is not located. The BSs that establish an N3 tunnel for a group and store the UE context and I-RNTI of the group can be determined based on the service area (e.g., metering) provided by the WDs of the group.

[0024] As described above, the I-RNTI is originally generated based on the identifier of the WD and the identifier of the final BS. However, in this embodiment, the I-RNTI can be generated independently of the identifiers of the WD and the BS. In other words, the BS treats the I-RNTI received from a WD belonging to a group as if the UE context is stored in the BS, and does not perform processing such as determining the final BS based on the received I-RNTI. The I-RNTI of the group is determined so as not to overlap with a normal I-RNTI generated based on the identifier of the WD and the identifier of the final BS. Furthermore, the I-RNTI of the group can be configured so that the BS can determine from its value that it is the I-RNTI of the group, rather than an I-RNTI generated based on the identifier of the WD and the identifier of the final BS.

[0025] 4 is a sequence diagram when data to be transmitted occurs in WD#A1 of FIG. 2. In S1, WD#A1 transmits an RRC connection setup request message to BS#1. The RRC connection setup request message includes I-RNTI#A and MAC-I#A stored in WD#A1, and the data to be transmitted. In response to the RRC connection setup request message, BS#1 determines context#A, which is the UE context of WD#A1, based on I-RNTI#A in S2, and authenticates WD#A1 based on context#A and MAC-I#A. Here, it is assumed that the authentication is successful. In this case, BS#1 transmits the data to be transmitted to the UPF using N3 tunnel#A1 in S3, and also transmits an RRC resume message to WD#A1 in S4.

[0026] The sequence in Fig. 4 is basically the same as the sequence for transitioning from an inactive state to a connected state specified in 3GPP, except that in S2, BS#1 determines the UE context stored in itself, without determining the last BS based on I-RNTI#A.

[0027] As is clear from the sequence of Fig. 4, in this embodiment, when the WD transmits data, it is not necessary to transmit and receive control signaling involving the BS, AMF, SMF, and UPF. Therefore, it is possible to prevent a long time from when data to be transmitted to the WD is generated until the data is transmitted.

[0028] As described above, in this embodiment, an N3 tunnel for a group is set up in advance in a BS in an area where a service is provided, and a UE context and I-RNTI for the group are stored. For this reason, in this embodiment, a control node is provided in the core network of the mobile communication network, as shown in Fig. 5. The control node stores the I-RNTI and UE context of the group, and inputs information identifying the BS for setting up the N3 tunnel.

[0029] Fig. 6 is a sequence diagram of a process for setting up an N3 tunnel between a BS and a UPF and storing the I-RNTI and UE context of the group in the BS. Note that Fig. 6 shows the process for one BS. The control node performs the process of Fig. 6 for each BS for which an N3 tunnel is set up.

[0030] In S10, the control node sends a configuration request message to the BS. The configuration request message includes the UE context and I-RNTI to be stored in the BS. In response to receiving the configuration request message, the BS sends a request to establish a PDU session to the AMF in S11. As a result, the AMF, SMF, and UPF send and receive control signaling to establish the N3 tunnel. The BS also stores the UE context and I-RNTI. When the configuration of the N3 tunnel section is completed, the BS sends an RRC reconfiguration message to the control node in S12. In response to the RRC reconfiguration message, the control node sends an RRC reconfiguration complete message to the BS in S12. The processes of S11 to S13 are basically the same as the process of establishing a PDU session for a WD. The difference is that the control node acting as the WD sends the UE context and I-RNTI to be stored in the BS to the BS.

[0031] Then, in S14, the BS transmits an RRC release message including information indicating the suspension to the control node. The process of S14 is also similar to the process performed by the BS to transition the WD from a connected state to an inactive state. The difference is that the I-RNTI and MAC-I do not need to be notified to the UE in the RRC release message.

[0032] The purpose of the sequence in Fig. 6 is to set up an N3 tunnel between the BS and the UPF and store the I-RNTI and UE context of the group in the BS. Therefore, the processes in S12 to S14 in Fig. 6 can be omitted.

[0033] Note that the I-RNTI and MAC-I of the group are stored in advance in each WD belonging to the group, and this can be done in any manner at any timing before the WD is used for a service, for example, before shipping the WD, or immediately before using the WD for a service, etc. For example, the MAC-I of the group can also be stored in the control node, and the control node can transmit the MAC-I and I-RNTI of the group to each WD of the group configured to be able to communicate with the control node.

[0034] The invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the gist of the invention.

[0035] This application claims priority based on Japanese Patent Application No. 2023-125627, filed August 1, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A mobile communications network for communicating with a plurality of wireless devices belonging to the same group, comprising a plurality of base stations, configured to maintain a connection for the group between each of a plurality of first base stations among the plurality of base stations and a network node connected to an external network, each of the plurality of first base stations storing a context of the group and an identifier of the context.

2. The mobile communications network according to claim 1, wherein the plurality of wireless devices are configured to be in an inactive state when not communicating and to transition to a connected state when communicating.

3. The mobile communications network of claim 2, wherein the plurality of wireless devices are configured not to transition to an idle state.

4. The mobile communication network according to any one of claims 1 to 3, wherein the plurality of wireless devices are devices performing machine-type communication or Internet of Things (IoT) devices.

5. A mobile communications network according to any one of claims 1 to 4, wherein the network node is a node implementing a User Plane Function (UPF).

6. A mobile communication network according to any one of claims 1 to 5, wherein the connection is an N3 tunnel.

7. A mobile communications network according to any one of claims 1 to 6, wherein the plurality of first base stations includes at least one of the plurality of base stations that serves an area in which the plurality of wireless devices are located.

8. A mobile communication network as claimed in any one of claims 1 to 7, wherein each of the plurality of wireless devices has the identifier of the context of the group and an authentication code generated based on the context of the group, and the plurality of first base stations are configured, upon receiving transmission data, the identifier and the authentication code from a first wireless device among the plurality of wireless devices, to determine the context of the group to which the first wireless device belongs based on the identifier, to authenticate the first wireless device based on the determined context and the authentication code, and, if authentication is successful, to transmit the transmission data to the connection.

9. A mobile communications network according to any one of claims 1 to 8, further comprising a control node configured to inform each of the first base stations of the context of the group and the identifier of that context, so as to establish the connection between each of the first base stations and the network node.

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