Communication device, control method, and program

Abstract

To provide a mechanism for realizing a DC connection in a manner that makes it easy to maintain a stable connection.SOLUTION: A communication device is disclosed that operates as an MN (Master Node) by Dual Connectivity (DC), and includes frequency selection means for selecting a second frequency band different from the first frequency band as a frequency band to be used between an SN (Secondary Node) and the UE when a first frequency band is used between the MN and UE (User Equipment) that operates as a terminal, and transmission means for transmitting the frequency band selected by the frequency selection means to a candidate SN (Secondary Node) that communicates with the UE.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a communication device, a control method, and a program. [Background technology]

[0002] The Third Generation Partnership Project (3GPP (registered trademark)) has formulated cellular communication standards. The 3GPP cellular communication standards (hereinafter referred to as "3GPP standards") are currently working on standardizing Integrated Access and Backhaul (IAB), which integrates access lines and backhaul lines (see Patent Document 1). In IAB, radio resources used for the access line between a base station (gNB) and a user terminal (UE, User Equipment) are also used for the backhaul line. Using IAB for the backhaul line enables a relay station (IAB node) to relay communication between a base station (IAB donor) and a UE via a radio line, thereby improving the connectivity of the radio access network. For example, IAB mainly uses radio resources in the millimeter wave band, such as the 28 GHz band. The frequency bands used in IAB are 700 MHz to 3.5 GHz for 4G LTE and 3.6 to 4.6 GHz for Sub6. In the millimeter wave band, radio waves from 27 GHz to 29.5 GHz are used. By using IAB, a relay device (IAB node) can relay communications between a base station device (IAB donor) and a terminal device via a wireless line, which allows area coverage to be expanded more cheaply than when using a wired line such as optical fiber.

[0003] Up until Release 17, which marks the standardization phase of 3GPP, specifications have been developed for fixed base stations (IAB nodes that do not move).

[0004] 3GPP is currently in the Release 18 phase. In this phase, active discussions are underway on MBSR, a use case for vehicle-mounted relays, and the specification of architecture and protocols to realize that use case. MBSR is an abbreviation for Mobile BaseStation Relay and is sometimes called mobile IAB. The use of MBSR is expected to provide high-quality communication services within vehicles, as well as improve communication quality in areas with poor signal reception or congested areas.

[0005] 3GPP has also standardized a technology called Dual Connectivity (DC). In DC, a UE simultaneously connects to two base stations called a Master Node (MN) and a Secondary Node (SN). The UE then communicates using component carriers supported by the two base stations, thereby increasing communication speed and connection redundancy. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2019-534625 Summary of the Invention [Problem to be solved by the invention]

[0007] Even when a connection is established using DC, fluctuations in the wireless communication environment due to the movement of terminals (UE, MBSR, IAB node, etc.) can cause connection instability, such as a decrease in communication speed. For example, if a terminal is connected via Sub6 and multiple other terminals enter the coverage area of ​​the same base station and begin communicating, the base station's available bandwidth may become insufficient, causing line congestion and a significant decrease in communication speed. Furthermore, when a terminal connects wirelessly using the millimeter wave frequency band, due to the strong linearity of the millimeter wave's propagation characteristics, communication is easily interrupted when affected by obstructions such as buildings, making it difficult to maintain stable communication due to connection interruptions.

[0008] The present invention has been made in consideration of at least one of the above-described problems, and an object of one aspect of the present invention is to provide a mechanism for realizing a DC connection in a manner that makes it easier to maintain a stable connection. [Means for solving the problem]

[0009] A communication device according to one aspect of the present invention is a communication device that operates as a MN (Master Node) by Dual Connectivity (DC), a frequency selection means for selecting a second frequency band different from the first frequency band as a frequency band to be used between an SN (Secondary Node) and a UE (User Equipment) operating as a terminal when the first frequency band is used between the UE and the SN; and a transmitting means for transmitting the frequency band selected by the frequency selecting means to the candidate SN (Secondary Node) that communicates with the UE. [Effects of the Invention]

[0010] According to one aspect of the present invention, it is possible to provide a mechanism that can realize a DC connection in a manner that makes it easier to maintain a stable connection. [Brief explanation of the drawings]

[0011] [Figure 1]FIG. 1 is a diagram (part 1) showing an example of the configuration of a wireless communication system. [Figure 2] FIG. 1 is a diagram illustrating the hardware configuration of a base station / IAB donor. [Figure 3] FIG. 1 illustrates the software functions of a base station / IAB donor. [Figure 4] This is the DC connection sequence controlled by the base station of the MN. [Figure 5] 10 is a flowchart of a base station / IAB donor of a MN in this embodiment. [Figure 6] FIG. 2 is a diagram (part 2) illustrating an example of the configuration of a wireless communication system. [Figure 7] This is the DC connection sequence controlled by the IAB donor. [Figure 8] BAP message format (for notification of selected frequency band). DETAILED DESCRIPTION OF THE INVENTION

[0012] Each embodiment will be described in detail below with reference to the accompanying drawings. In the following description, the "number ***" in TS*** represents the number of the technical specification in the 3GPP standard.

[0013] <DC operation explanation based on 3GPP specifications> 1 shows an example of the configuration of a wireless communication system according to this embodiment. The system 100 includes multiple UEs 110 to 115, a core network 120, base stations 101 to 102, and a shield 130 such as a building. The base stations 101 and 102 are connected to the core network 120 via wired links 121 and 122 (optical fibers or other wired means). The base stations 101 and 102 are also connected to each other via a wired link 123.

[0014] When the UE 110 establishes a DC connection, it connects to the base station 101, which is the MN, via a wireless MCG link 124, and simultaneously connects to the base station 102, which is the SN, via a wireless SCG link 125. Redundant transmission from different base stations enables broadband and high reliability. MCG is an abbreviation for Master Cell Group, and SCG is an abbreviation for Secondary Cell Group.

[0015] However, for example, when the wireless MCG link 124 and the wireless SCG link 125 both use the millimeter wave frequency band, the radio wave strength may be attenuated by the influence of the shielding object 130, which may further cause radio wave interference or disconnection between the base station and the terminal. Also, when the wireless MCG link 124 and the wireless SCG link 125 both use the Sub6 frequency band, for example, when a large number of UEs 111 to 115 newly connect to the base stations 101 and 102 in the DC and communicate at high speed, the lines may become congested and there may be a shortage of bandwidth.

[0016] <Hardware configuration> FIG. 2 is a hardware functional block diagram of a base station (including an IAB donor) in this embodiment.

[0017] The base station is configured from the hardware of a control unit 201, a storage unit 202, a wireless communication unit 203, and an antenna control unit 204.

[0018] The control unit 201 executes a control program stored in the storage unit 202 to control the entire device.

[0019] The storage unit 202 stores a control program executed by the control unit 201, information on the UE to be connected, connection strength with other base stations (including IAB donors), and other various information. The wireless communication unit 203 is a wireless communication unit for performing cellular network communication such as LTE or 5G that conforms to the 3GPP standard. Note that, although the cellular network communication performed by the wireless communication unit is described here as 5G, it is also applicable to other networks (e.g., 5G Advanced and 6G). That is, the base station (including the IAB donor) described in this embodiment is a gNB (next generation NodeB) in the 5G standard. Note that, when this embodiment is applied to 6G, the base station may be a 6gNB / 6GNB. Furthermore, the base station serving as the MN may be a gNB, and the base station serving as the SN may be a 6gNB. That is, it is also possible to apply this embodiment to DCs of different RATs (Radio Access Technologies), such as 5G and 6G.

[0020] The antenna control unit 204 controls the antenna used for wireless communication performed by the wireless communication unit 203 .

[0021] <Software configuration> FIG. 3 is a diagram showing software functions of a base station (including an IAB donor) in this embodiment.

[0022] The software function block 301 is stored in the storage unit 202 and executed by the control unit 201. The software function block 301 includes a signal transmission unit 302, a signal reception unit 303, a data storage unit 304, a connection control unit 305, a network configuration information management unit 306, a connection candidate station management unit 307, and a signal generation unit 308. The software function block 301 also includes a frequency band selection unit 309 and an SN selection unit 310. The signal transmission unit 302 and the signal reception unit 303 control the wireless communication unit 203 via the control unit 201, and perform cellular network communication such as LTE or 5G that conforms to the 3GPP standard with other base stations (including IAB donors) and the UE.

[0023] Furthermore, the connection control unit 305 controls the antenna control unit 204 via the control unit 201 during wireless communication.

[0024] The data storage unit 304 controls and manages the storage unit 202, which is the entity, and stores and holds the software itself, connection information with other base stations (IAB nodes in the case of an IAB donor), information about UEs, etc. Information between nodes can be collected by broadcast signals and communication packets (hereinafter referred to as BAP control packets) accompanying various control PDUs of the Backhaul Adaptation Protocol (BAP). Information from UEs can be collected, for example, by RRC (Radio Resource Control) messages.

[0025] In the case of an IAB donor, the network configuration information management unit 306 manages configuration information of the IAB network configured including the own station. The network configuration information management unit 306 also manages type information of the UE, IAB node, and MBSR that make a connection request to the own station. The information generated by the network configuration information management unit 306 is used when the connection control unit 305 generates a connection control signal.

[0026] The signal generating unit 308 generates various signals to be wirelessly transmitted. The generated various signals are transmitted by the signal transmitting unit 302.

[0027] When operating as a base station for the MN, the frequency band selection unit 309 selects a frequency band for the UE or IAB node to connect to the base station for the SN.

[0028] The SN selection unit 310 selects a base station that can use the frequency band selected by the frequency band selection unit 309 as an SN base station.

[0029] <First embodiment: DC connection controlled by base station of MN> For the problem described in FIG. 1, a method for solving DC connection based on frequency bands by a base station of a MN will be described.

[0030] Fig. 4 shows a DC connection sequence controlled by the MN base station in this embodiment. Fig. 4 shows the SN addition processing sequence in this embodiment based on the general SN addition processing sequence in the 3GPP standard. This sequence is based on the premise that the UE 110 is connected to the MN base station 101.

[0031] The UE 110 transmits a Measurement Report to the MN base station 101 (S401). The UE 110 includes in the Measurement Report a list summarizing the radio wave qualities of surrounding base stations (neighboring cells) detected by the UE 110, and notifies the MN base station 101 of the list periodically or when a specific condition is triggered. The UE 110 includes in the Measurement Report frequency bands available to the surrounding base stations, and notifies the MN base station 101 of the list periodically or when a specific condition is triggered.

[0032] The MN base station 101, which has received the Measurement Report in S401, evaluates the connection strength of the UE 110, determines the SN selection method, and selects an SN (S402). A specific SN selection method will be described later in the description of the flowchart in FIG.

[0033] The subsequent steps are in accordance with the general SN addition processing sequence in the 3GPP standard.

[0034] The MN base station 101 transmits an SN Addition Request (S403) to the SN candidate base station 102. At this time, S403 transmits a message including parameters of the frequency band selected in S402 to the SN base station selected in S402. Furthermore, the parameters may be, for example, parameters such as S-NODE ADDITION REQUEST in the transmission / reception (Xn) message format between base stations described in TS.38.423 V17.0.6. In this case, the MN base station 101 may transmit a message to the SN candidate base station 102 by setting the selected frequency band in the parameter Index to RAT / Frequency Selection Priority.

[0035] The SN candidate base station 102 that has received the SN Addition Request (S403) transmits an SN Addition Request Acknowledge (S404) to the MN base station 101. The SN candidate base station 102 recognizes that it will use the same frequency band as the frequency band requested by the MN base station 101.

[0036] The MN base station 101 transmits an RRC ConnectionReconfiguration to the UE 110 (S405).

[0037] The UE 110 transmits an RRC ConnectionReconfigurationComplete to the MN base station 101 (S406).

[0038] The MN base station 101 transmits an SN Reconfiguration Complete to the SN base station 102 (S407).

[0039] Finally, a random access procedure is performed between the UE 110 and the SN base station 102 to establish a connection (S408).

[0040] 5 shows a flowchart of the MN base station / IAB donor in this embodiment. The MN base station selects an SN base station 102 that can use a frequency band different from the frequency band used for connecting with the UE. This enables high-reliability and high-speed communication.

[0041] After receiving the Measurement Report (S401), the MN base station 101 analyzes the signal strength of the receiving cell (S501). Here, the data format of the Measurement Report is defined in TS38.331 of the 3GPP specification. The Measurement Report contains MeasResults, which is information about the signal quality of surrounding base stations. MeasResults contains MeasResultListNR, which is a list of information about the signal quality of neighboring cells. MeasResultListNR contains MeasResultNR, information about the signal quality of neighboring cells. These are prepared for each base station detected by the UE. MeasResultNR contains PhysCellID, an ID that identifies the base station (cell), and MeasResult (RSRP, RSRQ, SINR), information about signal quality. RSRP is an abbreviation for Reference Signal Received Power. RSRQ is an abbreviation for Reference Signal Received Quality. SINR is an abbreviation for Signal to Interference plus Noise power Ratio.

[0042] The base station to which the UE can connect is determined based on the radio wave quality of neighboring cells (S502). For example, if the RSRP is above a certain threshold, it is determined that connection is possible. If there is no base station that can be determined to be connectable, DC is not possible and is not performed (S514). Next, the MN base station 101 confirms whether the frequency band used for communication with the UE 110 is millimeter wave or other than millimeter wave (S503).

[0043] If the millimeter wave frequency band is used in S503, i.e., if the MN base station 101 has confirmed that it is connecting to the UE 110 using the millimeter wave frequency band (S504), the process proceeds to S505. The MN base station 101 checks whether there is a base station connectable in the Sub6 frequency band among the connectable base stations based on the Measurement Report (S505). That is, based on the frequency band of the cell of the PhysCellID notified in the Measurement Report (the frequency band used by the connectable base station), it checks whether there is a base station connectable in the Sub6 frequency band (S505). Note that the MN base station 101 can check which cell uses which frequency band by referring to a correspondence list between PhysCellID and frequency band, etc. If there is a base station connectable in the Sub6 frequency band, it checks whether there are multiple base stations (S506). If there is a single base station, it decides to connect to that base station as the SN base station 102 (S508). If there are multiple base stations, it selects the base station with the highest RSRP and decides to connect to it as the SN base station 102 (S507). However, if there is no base station using the Sub6 frequency band among the base stations that can be connected in S505, a base station using the same millimeter wave as the MN base station 101 is selected as the SN base station 102 and a DC connection is performed (proceed to S510, which will be described later).

[0044] If the MN base station 101 confirms that it is connected to the UE 110 using the Sub6 frequency band, the result in S503 is “NO” and the process proceeds to S509. The MN base station 101 checks whether there is a base station connectable to the millimeter-wave frequency band among the connectable base stations based on the frequency band of the cell of the PhysCellID notified in the Measurement Report (S510). If there is a base station connectable to the millimeter-wave frequency band, the process checks whether there are multiple base stations (S511). If there is a single base station, the MN base station 101 determines to connect to that base station as the SN base station 102 (S513). If there are multiple base stations, the MN base station 101 selects the base station with the highest RSRP and determines to establish a DC connection as the SN base station 102 (S512). However, if there is no base station using the millimeter-wave frequency band among the connectable base stations in S510, the MN base station 101 selects the same Sub6 base station as the MN base station 101 and establishes a DC connection (S505). Note that the Sub6 frequency band in the description of FIG. 5 may be interpreted as the 4G LTE frequency band.

[0045] In this way, according to this embodiment, the MN base station 101 can preferentially select a frequency band different from the frequency band used for communication with the UE 110, and transmit information indicating the selected frequency band to the SN candidate base station 102.

[0046] <Second embodiment: Explanation of DC operation in IAB configuration based on 3GPP specifications> FIG. 6 shows a second example of the configuration of a wireless communication system according to this embodiment.

[0047] The system 600 includes multiple UEs 610-615, a core network 620, base stations 601-604 (IAB donor 601, its subordinate IAB nodes 602-603, and MBSR 604) having IAB functionality, and a building or other such shielding structure 630. The IAB donor 601 is connected to the core network 620 via a wired link 621 (optical fiber or other wired means). The IAB donor 601 is also connected to its subordinate IAB nodes 602-603 via wireless backhaul links, forming an IAB topology. In this embodiment, the IAB donor 601 and the IAB nodes 602-603 are 5G base stations (gNBs) equipped with additional functionality to support IAB functionality, as defined in the 3 GPP TS 38.300 v 17.6.0 specification.

[0048] The MBSR 604 is mounted on the vehicle 640 and provides network coverage and capacity expansion. The IAB donor 601 can communicate with onboard UEs such as the remote UE 610 as well as UEs outside the vehicle such as the UE 615. Thus, the IAB donor 601 and the MBSR 604 form a backhaul network or IAB network, or IAB topology, that accommodates the UEs 610 and 615. IAB specifications are defined in several 3GPP standard documents, such as: -TS 38.300 RAN Architecture (V 17.6.0) -TS 38.321 MAC Protocol (V 17.6.0) -TS 38.331 Radio Resource Control (RRC) Protocol (V 17.6.0) -TS 38.340 Backhaul Adaptation Protocol Layer (V 17.5.0) -TS 38.401 RAN Architecture (V 17.6.0) -TS 38.423 Xn Application Protocol (V 17.5.0) -TS 38.473 F 1 Application Protocol (V 17.6.0) In this IAB configuration, when MBSR 604 is DC connected, MBSR 604 connects to IAB node 602, which becomes MN, via wireless MCG link 624. At the same time, by connecting to IAB node 603, which becomes SN, via wireless SCG link 625, broadband can be achieved through simultaneous communications from different IAB nodes (base stations).

[0049] However, for example, if the wireless MCG link 624 and the wireless SCG link 625 both use the millimeter wave frequency band, the following possibility exists: That is, radio wave intensity may be attenuated due to the influence of the shielding object 630, which may result in radio wave interference or disconnection in the wireless SCG link 625 between the IAB node 603 and the MBSR 604. Furthermore, if the wireless MCG link 624 and the wireless SCG link 625 both use the Sub6 frequency band, for example, a large number of UEs 611 to 614 may connect to the IAB nodes 602 and 603 and simultaneously communicate at high speeds, which may result in line congestion.

[0050] Second embodiment: IAB donor controlled DC connection A frequency band-based DC connection solution by IAB donors to the problem described in the wireless communication system of FIG. 6 will now be described.

[0051] Fig. 7 shows a DC connection sequence controlled by the IAB donor 601 in this embodiment. Fig. 7 shows a sequence of redundancy procedures for the intra-CU topology of an IAB node in this embodiment, based on the general SN addition processing sequence in the 3GPP standard (see TS38.401 Chapter 8.2.4). This sequence assumes that the MBSR 604 is connected to the IAB donor 601 via the IAB node 602.

[0052] Downlink (DL) transmission of U-Plane data is as follows: That is, DL data is transmitted from IAB donor 601 to MBSR 604 via IAB node 602 on a backhaul link, and then transmitted from MBSR 604 to UE 610 via Uu, similar to wireless communication between a base station and a UE (S700). Uplink (UL) transmission of U-Plane data is transmitted from UE 610 to MBSR 604 via Uu, and then transmitted from MBSR 604 to IAB donor 601 via IAB node 602 on a backhaul link (S700).

[0053] The MBSR 604 transmits a Measurement Report to the IAB node 602 (S701). The Measurement Report includes the radio wave quality of surrounding base stations (including IAB donors and IAB nodes).

[0054] The IAB node 602, which is the parent node of the first path that received the Measurement Report in S701, performs the following: Sends a UL RRC Message Transfer to transmit the Measurement Report to the IAB donor 601 (S702).

[0055] Upon receiving the Measurement Report, the IAB donor 601 evaluates the connection strength of the MBSR 604, determines a method for selecting a parent node for the second path of the MBSR 604, and selects a parent node for the second path (S703). The specific method for selecting a parent node for the second path is the same as the method in the flowchart of Figure 5, except that the MN base station 101 is replaced with the IAB donor 601.

[0056] The subsequent steps are the same as the general intra-CU topology redundancy procedure sequence in the 3GPP standard.

[0057] The IAB donor 601 transmits a UE Context Setup Request (S704) to the IAB node 603, which is a candidate parent node of the second path. At this time, S704 transmits a message including parameters of the frequency band selected in S703 to the parent node of the second path selected in S703. For example, the existing parameter "RAT-Frequency Priority Information" of S704 may be used, or the parameter may be added to a reserved field and transmitted. Furthermore, the following method may be used as a message transmitting the frequency band selected by the IAB donor 601 to the parent node of the second path. That is, the frequency band desired for connection may be transmitted by adding the parameter "selected frequency band" to the reserved field of the PDUType of the BAP message in FIG. 8. BAP is an abbreviation for Backhaul Adaptation Protocol.

[0058] The IAB node 603, which is a candidate parent node for the second path and has received S704, transmits a UE Context Setup Response to the IAB donor 601 (S705). The IAB node 603 recognizes that it will use the same frequency band as the frequency band requested by the IAB donor 601.

[0059] The IAB donor 601 transmits a DL RRC Message Transfer Response (RRC Reconfiguration) to the IAB node 602, which is the parent node of the first path (S706).

[0060] The IAB node 602, which is the parent node of the first path, transmits an RRC Connection Reconfiguration to the MBSR 604 (S707).

[0061] The MBSR 604 sends an RRC Connection Reconfiguration Complete to the IAB node 602, which is the parent node of the first path (S708).

[0062] The IAB node 602 transmits a UL RRC Message Transfer (RRC Reconfiguration Complete) to the IAB donor 601 (S709).

[0063] Thereafter, a random access procedure is performed between the MBSR 604 and the IAB node 603, which is a parent node candidate for the second path, to establish a connection (S710).

[0064] In addition, in this embodiment, a recording medium storing software program code for implementing the above-described functions may be supplied to a system or device. Then, a computer (CPU, MPU) of the system or device may read and execute the program code stored on the recording medium. In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes this embodiment. The functions can also be implemented by a circuit (e.g., an ASIC or FPGA) that implements one or more functions. ASIC stands for Application Specific Integrated Circuit. FPGA stands for Field Programmable Gate Array. Furthermore, some or all of the various processes described in the above flowcharts can be implemented by a hardware circuit cooperating with a processor such as a CPU or MPU.

[0065] Examples of storage media that can be used to supply the program code include flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, ROMs, and DVDs.

[0066] Furthermore, the above-mentioned functions may be realized not only by the computer executing the read program code, but also by the operating system (OS) running on the computer performing some or all of the actual processing based on the instructions of the program code. OS is an abbreviation for Operating System.

[0067] Furthermore, the program code read from the storage medium is written to a memory provided on a function expansion board inserted into the computer or a function expansion unit connected to the computer. Then, based on the instructions of the program code, a CPU provided on the function expansion board or function expansion unit may perform some or all of the actual processing to realize the above-mentioned functions. Note that the functions of the base station described above can also be provided by the cooperative operation of separate RUs, DUs, and CUs (Radio Units, Distributed Units, and Central Units). In this case, the RUs control the antenna and radio waves, the DUs perform modulation / demodulation and media access control (MAC), and the CUs control the RUs and DUs under their control and act as a bridge to the core network. In this case, control of the MN is mainly performed by the CUs constituting the base station and the IAB CUs constituting the IAB donor. Note that the CUs and IAB CUs can achieve cooperative operation by exchanging control signals with DUs connected to a network such as a fiber network and RUs connected to the DUs. When applying this invention to a DC connection including a 6gNB node supporting 6G, the interface between base stations can be configured to use an Xn2 interface, which specifies communication between 6G base stations, instead of the Xn interface. That is, when the SN is a 6gNB, the MN may communicate messages such as an S-NODE ADDITION REQUEST with the SN using an Xn2 message. Note that the names of the interfaces and messages are merely examples and are not limited to these.

[0068] The first and second embodiments have been described on the assumption that an SN addition process is performed, but the first and second embodiments can also be applied to a case in which an SN change process is performed.

[0069] In addition, the following supplementary notes are disclosed regarding the above-described embodiment.

[0070] [Appendix 1] A communication device that operates as a MN (Master Node) by Dual Connectivity (DC), a frequency selection means for selecting a second frequency band different from the first frequency band as a frequency band to be used between an SN (Secondary Node) and a UE (User Equipment) operating as a terminal when the first frequency band is used between the UE and the SN; a transmitting means for transmitting the frequency band selected by the frequency selecting means to the candidate SN (Secondary Node) that communicates with the UE. [Appendix 2] The communication device according to claim 1, wherein the frequency selection means selects the second frequency band based on a frequency band of a cell reported in a Measurement Report. [Appendix 3] 3. The communication device according to claim 1, wherein the first frequency band and the second frequency band are different ones of millimeter wave, Sub6, and 4G LTE frequency bands, respectively. [Appendix 4] The communication device according to any one of Supplementary Notes 1 to 3, further comprising an SN selection means for selecting a base station having a radio wave strength to which the UE can connect as a candidate for the SN. [Appendix 5] The communication device described in Appendix 4, characterized in that, when there are multiple base stations with radio wave strength to which the UE can connect, the SN selection means selects the base station with the strongest radio wave strength as the SN candidate. [Appendix 6] The communication device according to claim 4 or 5, wherein the frequency selection means and the SN selection means operate when DC is established. [Appendix 7] 7. The communication device according to any one of Supplementary Notes 1 to 6, wherein the transmitting means uses an Xn message. [Appendix 8] A communication device that configures an NR (New Radio) backhaul network, a frequency selection means for selecting a second frequency band different from the first frequency band as a frequency band to be used between a node or relay under the topology of the own station and a parent node connected by an MCG (Master Cell Group) link in an SCG (Secondary Cell Group) link when a first frequency band is used between the node or relay and the parent node by Dual Connectivity (DC); a transmitting means for transmitting the frequency band selected by the frequency selecting means to a parent node of the SCG. [Appendix 9] The communication device according to claim 8, wherein the frequency selection means selects the second frequency band based on a frequency band of a cell reported in a Measurement Report. [Appendix 10] 10. The communication device according to claim 8 or 9, wherein the node or relay is an IAB (Integrated Access and Backhaul) node or an MBSR (Mobile Base Station Relay). [Appendix 11] The communication device according to any one of appendices 8 to 10, wherein the first frequency band and the second frequency band are different ones of millimeter wave, Sub6, and 4G LTE frequency bands, respectively. [Appendix 12] A communication device described in any one of appendices 8 to 11, further comprising a parent node selection means for selecting a base station node with radio wave strength to which the node or relay can connect as a candidate parent node in the SCG. [Appendix 13] The communication device described in Appendix 12, characterized in that, when there are multiple base station nodes with radio wave strength to which the node or relay can connect, the parent node selection means selects the node with the strongest radio wave strength as a candidate parent node in the SCG. [Appendix 14] 14. The communication device according to claim 12, wherein the frequency selection means and the parent node selection means operate when a DC is established. [Appendix 15] The communication device according to any one of Supplementary Note 8 to 14, wherein the transmitting means uses an RRC (Radio Resource Control) message. [Appendix 16] 16. The communication device according to any one of appendices 8 to 15, wherein the transmitting means uses a BAP (Backhaul Adaptation Protocol) message. [Explanation of symbols]

[0071] 100 systems 101 MN base station 102 SN base station 120 Core Network 201 Control Unit 302 Signal transmitting unit (transmitting means) 303 Signal receiving unit 304 Data storage unit 305 Connection control section 306 Network Configuration Information Management Department 307 Connection Candidate Station Management Department 308 Signal Generation Unit 309 Frequency band selection unit (an example of frequency selection means) 310 SN selection unit (SN selection means, an example of parent node selection means)

Claims

1. A communication device that operates as a Master Node (MN) by Dual Connectivity (DC), a frequency selection means for selecting a second frequency band different from the first frequency band as a frequency band to be used between a secondary node (SN) and a user equipment (UE) operating as a terminal when the first frequency band is used between the UE and the user equipment; a transmitting means for transmitting the frequency band selected by the frequency selecting means to the candidate SN (Secondary Node) that communicates with the UE.

2. 2. The communication device according to claim 1, wherein the frequency selection means selects the second frequency band based on a frequency band of a cell reported in a Measurement Report.

3. The communication device according to claim 1 , wherein the first frequency band and the second frequency band are different ones of millimeter wave, Sub6, and 4G LTE frequency bands, respectively.

4. 4. The communication device according to claim 3, further comprising an SN selection means for selecting a base station having a radio wave strength to which the UE can connect as a candidate for the SN.

5. 5. The communication device according to claim 4, wherein, when there are a plurality of base stations with radio wave strength to which the UE can be connected, the SN selection means selects the base station with the strongest radio wave strength as the SN candidate.

6. 5. The communication device according to claim 4, wherein said frequency selection means and said SN selection means operate when DC is established.

7. 7. The communication device according to claim 1, wherein said transmitting means uses an Xn message.

8. A communication device constituting an NR (New Radio) backhaul network, a frequency selection means for selecting, when a first frequency band is used between a node or relay under the topology of the own station and a parent node connected by an MCG (Master Cell Group) link by Dual Connectivity (DC), a second frequency band different from the first frequency band as a frequency band to be used between the node or relay and the parent node in an SCG (Secondary Cell Group) link; a transmitting means for transmitting the frequency band selected by the frequency selecting means to a parent node of the SCG.

9. 9. The communication device according to claim 8, wherein the frequency selection means selects the second frequency band based on a frequency band of a cell reported in a Measurement Report.

10. 9. The communication device according to claim 8, wherein the node or relay is an Integrated Access and Backhaul (IAB) node or a Mobile Base Station Relay (MBSR).

11. The communication device according to claim 8 , wherein the first frequency band and the second frequency band are different ones of millimeter wave, Sub6, and 4G LTE frequency bands, respectively.

12. 9. The communication device according to claim 8, further comprising parent node selection means for selecting a base station node having radio wave strength to which the node or relay can be connected as a candidate for a parent node in the SCG.

13. The communication device according to claim 12, characterized in that, when there are multiple base station nodes with radio wave strength to which the node or relay can be connected, the parent node selection means selects the node with the strongest radio wave strength as a candidate parent node in the SCG.

14. The communication device according to claim 12, wherein the frequency selection means and the parent node selection means operate when a DC is established.

15. 15. The communication device according to claim 8, wherein the transmitting means uses an RRC (Radio Resource Control) message.

16. 15. The communication device according to claim 8, wherein the transmitting means uses a BAP (Backhaul Adaptation Protocol) message.

17. A control method for controlling communication of a communication device operating as a Master Node (MN) by Dual Connectivity (DC), comprising: a frequency selection step of selecting a second frequency band different from the first frequency band as a frequency band to be used between a secondary node (SN) and a user equipment (UE) operating as a terminal when the first frequency band is used between the UE and the SN; a transmission step of transmitting the frequency band selected in the frequency selection step to the SN (Secondary Node) candidate that communicates with the UE.

18. Dual Connectivity (DC) is used to configure a computer of a communication device that controls communication of the communication device that operates as a Master Node (MN). a frequency selection step of selecting a second frequency band different from the first frequency band as a frequency band to be used between a secondary node (SN) and a user equipment (UE) operating as a terminal when the first frequency band is used between the UE and the SN; a transmission step of transmitting the frequency band selected by the frequency selection step to a candidate SN (Secondary Node) that communicates with the UE.

19. A control method for controlling communication of a communication device constituting an NR (New Radio) backhaul network, a frequency selection step of selecting a second frequency band different from the first frequency band as a frequency band to be used between a node or relay under the topology of the own station and a parent node connected by an MCG (Master Cell Group) link through an SCG (Secondary Cell Group) link when a first frequency band is used between the node or relay and the parent node through an MCG (Master Cell Group) link by Dual Connectivity (DC); A control method comprising a transmission step of transmitting the frequency band selected by the frequency selection step to a parent node candidate in the SCG.

20. A computer of a communication device that configures an NR (New Radio) backhaul network, a frequency selection step of selecting a second frequency band different from the first frequency band as a frequency band to be used between a node or relay under the topology of the own station and a parent node connected by an MCG (Master Cell Group) link through an SCG (Secondary Cell Group) link when a first frequency band is used between the node or relay and the parent node through an MCG (Master Cell Group) link by Dual Connectivity (DC); a transmission step of transmitting the frequency band selected by the frequency selection step to a parent node candidate in the SCG.

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