Base station, and communication control method

Abstract

A base station according to one embodiment performs wireless communication with a first user device. This base station 200 includes a first wireless unit RU#1 that performs wireless communication with a first user device, and a second wireless unit RU#2. The base station also includes a first distributed unit DU#1 connected to the first wireless unit RU#1, and a second distributed unit DU#2 connected to the second wireless unit RU#2. The base station furthermore includes a control part for controlling the first distributed unit DU#1 and the second distributed unit DU#2. The control part switches the destination for connection of the first user device from the first wireless unit RU#1 to the second wireless unit RU#2 on the basis of a first transmission period that is required for transmission to a core network of first video data received from the first user device.

Description

Technical Field

[0001] The present disclosure relates to a base station and a communication control method.

Background Art

[0002] Recently, a fifth-generation mobile communication system that can be used by various entities according to regional needs or individual needs has been attracting attention. Such a mobile communication system may be referred to as, for example, local 5G (5th Generation).

[0003] In local 5G, separate from the 5G system for the whole country by mobile communication carriers, various entities such as regional companies and local governments can independently build a network spot by spot within buildings or sites. Therefore, local 5G is expected to be used for various needs closely related to regions and the like.

[0004] In the field related to such mobile communication, for example, there are the following technologies. That is, when monitoring the situation related to communication with a terminal and detecting a situation change, a priority is set for each terminal, and when the total communication bandwidth required for communication with each terminal exceeds the available communication bandwidth, there is a base station device that temporarily restricts communication with terminals in ascending order of priority (for example, Patent Document 1 below).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] The base station according to the first aspect is a base station that performs wireless communication with a first user device. The base station includes a first radio unit that performs wireless communication with the first user device, and a second radio unit. The base station also includes a first distributed unit connected to the first radio unit, and a second distributed unit connected to the second radio unit. Further, the base station includes a control unit that controls the first distributed unit and the second distributed unit. The control unit switches the connection destination of the first user device from the first radio unit to the second radio unit based on a first transmission period required for transmitting first video data received from the first user device to a core network.

[0007] The communication control method according to the second aspect is a communication control method in a base station. The base station includes a first radio unit that performs wireless communication with a first user device, and a second radio unit. The base station also includes a first distributed unit connected to the first radio unit, and a second distributed unit connected to the second radio unit. Further, the base station includes a control unit that controls the first distributed unit and the second distributed unit. The communication control method includes a step in which the control unit switches the connection destination of the first user device from the first radio unit to the second radio unit based on a first transmission period required for transmitting first video data received from the first user device to a core network.

Brief Description of the Drawings

[0008]

Figure 1

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[0009] One aspect of the present disclosure aims to suppress the transmission delay of video data.

[0010] [First Embodiment] Local 5G may be used to support remote work in factories and the like. For example, cameras are provided on each terminal, and an administrator checks whether the work is being carried out normally based on the video data transmitted from each terminal. In such a use case, video data having a resolution of "4K" or higher is transmitted from each terminal, and a high throughput is required in the uplink direction rather than in the downlink direction.

[0011] In video data of "4K" or higher, the data exists burstily for each video frame, and there may be data several times the average throughput within the video frame. In particular, this may be prominent during the rising period of a certain video frame. When such video data is transmitted simultaneously from a plurality of terminals, a large load is instantaneously applied to the base station. In this case, it takes time for the base station to transmit the received video data to the core network, resulting in a transmission delay.

[0012] For example, in Patent Document 1 described above, when the priority of a terminal transmitting "4K" video data is low, if the communication is temporarily restricted, it is necessary to wait until the restriction is released to transmit the video data to the core network, resulting in a transmission delay.

[0013] Therefore, in the first embodiment, the base station aims to suppress the transmission delay of video data.

[0014] Hereinafter, embodiments will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0015] [Configuration Example of Mobile Communication System] FIG. 1 is a diagram showing a configuration example of a mobile communication system 10 according to the first embodiment.

[0016] As shown in FIG. 1, the mobile communication system 10 includes a UE (User Equipment) 100, a gNB (next generation Node B) 200, and a CN (Core Network) 300.

[0017] The UE 100 is a movable wireless communication device that performs wireless communication with the gNB 200. The UE 100 may be any device as long as it can perform wireless communication with the gNB 200. For example, the UE 100 may be a mobile phone terminal, a tablet terminal, a notebook PC, a sensor or a device provided in the sensor, a vehicle or a device provided in the vehicle, or an aircraft or a device provided in the aircraft. In the example of FIG. 1, an example of one UE 100 is shown, but there may be a plurality of them.

[0018] The gNB 200 is a wireless communication device that performs wireless communication with the UE 100. The gNB 200 performs wireless communication with the UE 100 that has established a connection with its own cell. The gNB 200 performs wireless communication with the UE 100 and provides various services to the UE 100. Also, the gNB 200 is also a communication device that performs wired communication with the CN 300. The gNB 200 is an example of a base station. The gNB 200 functions as a base station in a 5G system. The gNB 200 may be an en-gNB that can be connected to a base station (i.e., an eNB (evolved Node B)) in a 4G system. Also, the gNB 200 may be a base station after the 6G system.

[0019] Note that the network between the UE 100 and the gNB 200 may be referred to as the NG-RAN (Next Generation - Radio Access Network) or RAN in a 5G system.

[0020] The CN 300 is the network between the gNB 200 and the functional units (or functional entities) within the CN 300. The functional units within the CN 300 include the SMF (Session Management Function), the AMF (Access and Mobility Management Function), and the UPF (User Plane Function), etc. The establishment or update of the PDU session is performed by the SMF, etc. within the CN 300. Also, the functional units within the CN 300 can transmit user data to the UE 100 via the gNB 200, or transmit the user data sent from the UE 100 to other networks.

[0021] (Configuration example of gNB) Next, a configuration example of the gNB 200 will be described.

[0022] As shown in FIG. 1, the gNB 200 includes a CU (Central Unit) 250, a plurality of DUs (Distributed Units) 212, 222, 232, and a plurality of RUs (Radio Units) 211, 221, 231. In the gNB 200, a configuration in which a plurality of DUs 212, 222, 232 are connected to one CU 250 is allowed. With such a configuration, for example, functions can be separated between the CU 250 and the DUs 212, 222, 232, and processing delays, etc. can be prevented. In the example of FIG. 1, an example of three DUs 212, 222, 232 is shown, but the number of DUs may be two or four or more.

[0023] The CU250 may be referred to as an aggregation unit or a control unit, for example. The CU250 is connected to each of the DU212, 222, 232 to control each of the DU212, 222, 232. Also, the CU250 can select any one of the plurality of DU212, 222, 232 and communicate with the UE100. The CU250 is connected to the CN300 and exchanges user data and the like with the CN300.

[0024] Each of the DU212, 222, 232 may be referred to as a distributed unit, for example. DU#1 (212) is connected to the CU250 and also connected to RU#1 (211). Also, DU#2 (222) is connected to the CU250 and also connected to RU#2 (221). Further, DU#3 (232) is connected to the CU250 and also connected to RU#3 (231). Each of the DU212, 222, 232 has a scheduler respectively and performs scheduling processing such as allocating radio resources to the UE100.

[0025] Each of the RU211, 221, 231 may be referred to as a radio unit, for example. RU#1 (211) is controlled by DU#1 (212) and can perform wireless communication with the UE100. Also, RU#2 (221) is controlled by DU#2 (222) and can perform wireless communication with the UE100. Further, RU#3 (231) is controlled by DU#3 (232) and can perform wireless communication with the UE100.

[0026] As shown in FIG. 1, RAN#1 (210) includes DU#1 (212) and RU#1 (211). Also, RAN#2 (220) includes DU#2 (222) and RU#2 (221). Further, RAN#3 (230) includes DU#3 (232) and RU#3 (231).

[0027] (Configuration Examples of CU, DU, and RU) Next, the configuration examples of the CU250, DU#1(212), and RU#1(211) of the gNB200 will be described. Regarding the DUs 212, 222, and 232, DU#1(212) will be described as a representative, but the other DUs 222 and 232 have the same configuration as DU#1(212). Also, regarding the RUs 211, 221, and 231, RU#1(211) will be described as a representative, but the other RUs 221 and 231 have the same configuration as RU#1(211).

[0028] Figure 2(A) is a diagram showing a configuration example of the CU250 according to the first embodiment.

[0029] As shown in Figure 2(A), the CU250 has an interface unit 251 and a control unit 252.

[0030] The interface unit 251 transmits and receives messages and the like to and from the CN300 under the control of the control unit 252, and also transmits and receives messages to and from any one of the plurality of DUs 212, 222, 232. For example, the interface unit 251 transmits and receives NG interface messages to and from the CN300, and transmits and receives F1 interface messages to and from each of the DUs 212, 222, 232.

[0031] The control unit 252 performs various controls in the CU250. The control unit 252 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used for the processor's processing. The processor executes the programs stored in the memory to perform various processes. In each of the embodiments shown below, each process or each operation in the CU250 of the gNB200 may be performed by the control unit 252.

[0032] Figure 2(B) is a diagram showing a configuration example of DU#1(212) according to the first embodiment.

[0033] As shown in FIG. 2(B), DU#1(212) has an interface unit 2120 and a control unit 2121.

[0034] The interface unit 2120 transmits and receives messages and the like to and from CU250 under the control of the control unit 2121, and transmits and receives messages to and from RU#1(211). For example, the interface unit 2120 transmits and receives F1 interface messages to and from CU250, and transmits and receives O-RAN (Open Radio Access Network) fronthaul specification messages to and from RU#1(211).

[0035] The control unit 2121 performs various controls in DU#1(212). The control unit 2121 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used for the processing by the processor. The processor executes the programs stored in the memory to perform various processes. As shown in FIG. 2(B), the control unit 2121 may have a scheduler 213. In each of the embodiments shown below, each process or each operation in DU212, 222, 232 of gNB200 may be performed by the control unit 2121.

[0036] FIG. 3 is a diagram showing a configuration example of RU#1(211) according to the first embodiment.

[0037] The interface unit 2110 transmits and receives messages to and from DU#1(212), and transmits and receives data and the like to and from the radio processing unit 2111. That is, the interface unit 2110 extracts data, control signals, etc. from the messages received from DU#1(212), and outputs the extracted data, control signals, etc. to the radio processing unit 2111. Further, the interface unit 2110 generates a message in a predetermined format (e.g., O-RAN fronthaul) including these for the data, control signals, etc. output from the radio processing unit 2111, and outputs the message to DU#1(212).

[0038] The radio processing unit 2111 converts (up-converts) data or control signals output from the interface unit 2110 into radio signals in the radio band, and outputs the radio signals to the antenna 2112. Further, the radio processing unit 2111 converts (down-converts) the radio signals output from the antenna 2112 into data or radio signals in the baseband band, and outputs the data or radio signals to the interface unit 2110.

[0039] The antenna 2112 transmits the radio signals output from the radio processing unit 2111 to the UE 100. Further, the antenna 2112 receives the radio signals transmitted from the UE 100, and outputs the received radio signals to the radio processing unit 2111.

[0040] (QoS flow) Here, the QoS flow according to the first embodiment will be described.

[0041] In the 5G system, it is possible to provide a QoS (Quality of Service) service in units of IP flows to the UE 100. The QoS flow is established at the time of establishment (PDU Session Establishment) or update (PDU Session Modification) of the PDU (Protocol Data Unit) session. The QoS flow may be pre-configured.

[0042] The QoS flow is the finest granularity for distinguishing QoS in the PDU session. The QoS flow is established between the UE 100 and the UPF of the CN 300 under the control of the SMF of the CN 300. With the QoS service, it becomes possible to provide a service with a predetermined quality to the UE 100.

[0043] The SMF assigns a QFI (QoS Flow ID) to a new QoS flow. The QFI is an identifier used to identify each QoS flow. Then, the SMF generates a QoS profile, QoS rules, and a PDR (Packet Detection Rule) as information for configuring the QoS flow.

[0044] The QoS profile includes a 5QI (5G QoS Identifier), a guaranteed flow bit rate (GFBR) for the QoS flow, and a maximum flow bit rate (MFBR) for the QoS flow, etc. The 5QI is used to identify each QoS and represents the characteristics of the QoS. The SMF sends the QoS profile and the QFI to the gNB200. At the gNB200, a data radio bearer (DRB) is established together with the PDU session, and one PDU session is mapped to one DRB. At the gNB200, based on the QoS profile and the QFI, the mapping between the QoS flow and the DRB is performed.

[0045] The QoS rules include the QFI, a packet filter set, etc. The packet filter set includes one or more packet filters, and the packet filter includes information for mapping an IP flow to a QoS flow. Such information includes the source and destination IP addresses, the source and destination MAC addresses, etc. The SMF sends the QoS rules, etc. to the UE100. The UE100 uses the QoS rules to associate the UL traffic with the QoS flow.

[0046] The PDR includes information for classifying the packets (i.e., PDU packets) arriving at the UPF. The PDR includes information for mapping the user plane traffic to the QoS flow. The SMF sends the PDR, etc. to the UPF. The UPF performs classification of the user plane traffic, bandwidth enforcement, marking, etc. based on this information.

[0047] In the NAS layer between the UE100 and the UPF, UL packets and DL packets (i.e., IP flows) are associated with QoS flows. Also, in the AS layer (i.e., the SDAP (Service Data Adaption Protocol) layer) between the UE100 and the gNB200, QoS flows are associated with DRBs. Through such two-stage mapping, in the mobile communication system 10, packets can be mapped to appropriate QoS flows and appropriate DRBs, ensuring service quality.

[0048] (Operation example according to the first embodiment) Next, an operation example according to the first embodiment will be described.

[0049] In the first embodiment, the CU250 (for example, the control unit) switches the connection destination of the UE100 from the RU#1(211) (for example, the first radio unit) to the RU#2(221) (for example, the second radio unit) based on the transmission period (for example, the first transmission period) for transmitting the video data (for example, the first video data) received from the UE100 (for example, the first user device) to the core network.

[0050] For example, when the UE100 and another UE are performing wireless communication with the RU#1(211) and the transmission periods of the video data in the UE100 and the transmission periods of the video data in the other UE overlap, the UE100 is moved from the RU#1(211) to the RU#2(221).

[0051] As a result, for example, since the DU#2(222) (for example, the second distributed unit) that processes the video data transmitted from the UE100 and the DU#1(212) (for example, the first distributed unit) that processes the video data transmitted from another UE are different DUs, it is possible to suppress the transmission delay of the video data in the gNB200. Also, since the transmission load of the video data is dispersed to the DU#1(212) and the DU#2(222) without concentrating on the DU#1(212), the transmission load can be dispersed.

[0052] In the first embodiment, there are the following two cases. (1) A case where the transmission period is calculated using the parameters transmitted from the UE 100, and the UE 100 is handed over based on the transmission period. (2) A case where no parameters are transmitted from the UE 100, and the gNB 200 itself calculates the transmission period based on the UL video data that increases periodically, and the UE 100 is handed over based on the transmission period.

[0053] In the case of (1) above, when the UE 100 establishes a PDU session (PDU Session Establishment) or modifies a PDU session (PDU Session Modification), it transmits parameters to the CN 300. The parameters are information indicating that it is (real-time) streaming, the average throughput, the interval between video frames of the video data, and the start timing of the video frame. Here, the average throughput may be based on the amount of video data transmitted in a certain period measured in the UE 100 in the past. The interval between video frames represents the interval between one video frame and the next video frame. The start timing of the video frame may be represented by the SFN (System Frame Number), slot, or time at which the video frame starts. The UE 100 may transmit an RRC message including these parameters to the CU 250. In the CU 250, based on these parameters, the transmission period required for the gNB 200 to transmit the video data received from the UE 100 to the CN 300 is calculated. The transmission period also includes the transmission period required to transmit one video frame.

[0054] In the case of (2) above, CU250 monitors the video data transmitted from UE100 and measures the timing at which the video data increases by more than the data threshold value and the period of that timing. Then, gNB200 calculates the transmission period required for gNB200 to transmit the video data received from UE100 to CN300 based on the timing and the period. In the case of (2) above, the timing and the period represent the start timing of the transmission period and the transmission period itself, that is, they represent the transmission period itself. Note that the case of (2) above is not performed at the time of PDU session establishment (PDU Session Establishment) or PDU session update (PDU Session Modification), but is performed at the timing when CU250 detects that the video data has increased by more than the data threshold value.

[0055] Hereinafter, operation examples in two cases will be separately described.

[0056] (1) Case where parameters are transmitted from UE100 Next, an operation example in the case where parameters are transmitted from UE100 will be described.

[0057] FIG. 4 is a diagram showing an operation example in this case according to the first embodiment. Before the operation example shown in FIG. 4 is started, it is assumed that UE100 is wirelessly connected to RU#1(211) of RAN#1(210) and performing wireless communication.

[0058] In step S10, UE100 executes an application program related to streaming.

[0059] Steps S11 to S14 represent an example of the procedure for establishing a PDU session for video transmission by streaming.

[0060] That is, in step S11, UE 100 transmits a PDU session establishment request to CN 300 via RAN#1 (210) and CU 250. Note that UE 100 may include the above-mentioned four parameters (information indicating that it is (real-time) streaming, average throughput, the interval between video frames of video data, and the start timing of video frames) in the PDU session establishment request and transmit it.

[0061] In step S12, CN 300 transmits an N2 PDU session request to CU 250. The N2 PDU session request includes a PDU session ID. Further, the N2 PDU session request includes a PDU session establishment accept that permits the establishment of the requested PDU session. Furthermore, the N2 PDU session request includes N2 SM information, etc. The N2 SM information includes a QoS profile and a QFI. By receiving the N2 PDU session request, CU 250 can recognize that a QoS flow has been established based on the N2 SM information. Also, CN 300 may include the four parameters in the N2 SM information and transmit it to CU 250. CN 300 may include the four parameters in the N2 PDU session request or the PDU session establishment accept and transmit it to CU 250. Thereby, CU 250 can obtain the four parameters transmitted from UE 100 via CN 300.

[0062] In step S13, UE100 and CU250 execute an AN-specific resource setup via RAN#1(210). Specifically, CU250 transmits a PDU session ID, a PDU Session Establishment Accept, etc. to UE100 via RAN#1(210).

[0063] In step S14, CU250 transmits an N2 PDU Session Response to CN300. The N2 PDU Session Response includes a PDU session ID, N2 SM information, etc.

[0064] As described above, a PDU session including QoS flows is established between UE100 and UPF.

[0065] In step S15, CU250 performs DU selection processing.

[0066] FIG. 5 is a flowchart showing an example of DU selection processing according to an embodiment.

[0067] As shown in FIG. 5, in step S150, the control unit 252 of CU250 starts the processing.

[0068] In step S151, the control unit 252 calculates a transmission period required for transmitting one video frame. At the time of step S151, or before step S151, it is assumed that the control unit 252 has received four parameters from UE100: information indicating that it is (real-time) streaming, an average throughput, an interval between video frames of video data, and a start timing of a video frame.

[0069] For example, the control unit 252 calculates the transmission period as follows using these parameters. That is, the control unit 252 starts calculating the transmission period based on the information indicating that it is streaming. The control unit 252 sets the start timing of the video frame as the start timing of the transmission period. Then, assuming that the average throughput is the amount of video data for one video frame, the control unit 252 calculates the period required for the CU250 to transmit the video data amount to the CN300. The start timing of the video frame becomes the start timing of the video frame transmission period, and the time required to transmit the video data amount represents the length of the transmission period.

[0070] In step S152, the control unit 252 determines whether the transmission period overlaps with other transmission periods. In step S152, if the transmission period overlaps with other transmission periods (Y in step S152), the process proceeds to step S153. On the other hand, in step S152, if the transmission period does not overlap with other transmission periods (N in step S152), the process proceeds to step S155.

[0071] Here, the "other transmission period" refers to the transmission period (for example, the second transmission period) of video data (for example, the second video data) transmitted from another UE (for example, the second user device) that is performing wireless communication in the same cell as the cell where the UE100 performs wireless communication. Also, the "other transmission period" refers to the transmission period of video data transmitted from another UE that is performing wireless communication with the same RU as the RU#1 (211) where the UE100 is performing wireless communication. In step S152, the control unit 252 determines whether there is an overlapping period (for example, the first overlapping period) between the video data and the transmission period (for example, the first transmission period) transmitted from the UE100 and the other transmission period (for example, the second transmission period) transmitted from another UE.

[0072] FIG. 6 is a diagram showing an example of the overlapping period according to the first embodiment.

[0073] As shown in FIG. 6, video frame #1 is a video frame of video data transmitted from UE100. Video frame #2 is a video frame of video data transmitted from another UE. The transmission period of video frame #1 starts at "12:00:00" and is a 30-second period until "12:00:30". Also, the transmission period of video frame #2 (i.e., "another transmission period") starts at "12:00:10" and is a 40-second period until "12:00:40". Therefore, there is a 20-second overlapping period from "12:00:10" to "12:00:30" (for example, the first overlapping period). In the first embodiment, it is assumed that the existence of such an overlapping period causes a transmission delay in CU250.

[0074] Also, in step S152, it can also be considered that, for example, it is determined whether to hand over UE100 to another cell (or another RU). This is because if there is no overlapping period, there is no need to hand over UE100.

[0075] Note that even if there is an overlapping period, if it is less than the threshold value, there may be no transmission delay in the cell (or RU). Therefore, CU250 determines whether the overlapping period is equal to or greater than the threshold value. If it is equal to or greater than the threshold value (Y in step S152), it proceeds to step S153. Otherwise (N in step S152), it may proceed to step S155.

[0076] Returning to FIG. 5, in step S153, control unit 252 determines whether there is another transmission period in which the overlapping period (for example, the second overlapping period) is equal to or less than the period threshold value.

[0077] Here, the "different transmission period" refers to the transmission period of video data transmitted from another UE (for example, the third user device) that is performing wireless communication in a cell different from the cell (for example, the first cell) in which UE100 performs wireless communication, and this different cell is under RU#1 (211) (for example, the second cell). Also, the "different transmission period" refers to the transmission period of video data transmitted from another UE (for example, the third user device) that is performing wireless communication with RU#2 (221) different from RU#1 (211) with which UE100 performs wireless communication. The former targets another UE that is performing wireless communication in a different cell under RU#1 (211) where UE100 performs wireless communication. The latter targets another UE that is performing wireless communication with an RU different from RU#1 (211) with which UE100 performs wireless communication. Hereinafter, such another UE may be referred to as a "different UE". Also, hereinafter, the cell that is performing wireless communication with the "different UE" may be referred to as a "different cell", and the RU that is performing wireless communication with the "different UE" may be referred to as a "different RU", respectively.

[0078] As shown in FIG. 6, the transmission period of video frame #3 is illustrated as the "different transmission period". The "different transmission period" represents an example of a transmission period with a start timing of "12:00:15" and a period of "3 seconds". And the overlapping period (for example, the second overlapping period) between the transmission period of video frame #1 (for example, the first transmission period) transmitted from UE100 and the transmission period of video frame #3 (for example, the third video data) transmitted from the different UE (for example, the third transmission period) is "3 seconds". The control unit 252 compares the overlapping period with the period threshold. That is, the control unit 252 determines whether the overlapping period between the video frame transmitted from UE100 and the video frame transmitted from the different UE is less than or equal to the period threshold. Here, it is assumed that the period threshold is "5 seconds". In this case, the overlapping period is shorter than the period threshold.

[0079] For example, in FIG. 6, assume that a transmission delay occurs in video frame #1. By setting video frame #1 to be after video frame #3, the start timing of video frame #1 can be set to "12:00:18". Therefore, compared with the case where the start timing is set to "12:00:40" after video frame #2, the start timing can be advanced. Accordingly, the transmission delay of video frame #1 can be suppressed.

[0080] In step S153, it can be considered that the CU250 determines whether a transmission delay occurs in the other cell (or the other RU) even when causing the UE100 to hand over to another cell (or another RU). This is because if it is "another transmission period" shorter than the period threshold, it is possible to suppress the transmission delay even when the UE100 is handed over to another cell (or another RU).

[0081] Here, the period threshold may be a threshold that allows a transmission delay in the cell (or RU). Also, the period threshold may be a threshold determined by the capacity to process video data within a predetermined period in the cell (or RU). The period threshold may be different for each cell or RU.

[0082] Note that as described above, as the destination of the UE100, there are another cell and another RU. In the case of another cell, when the UE100 is performing wireless communication in the cell (for example, the first cell) accommodated in the RU#1 (211), the control unit 252 switches the connection destination of the UE100 from this cell to another cell (for example, the second cell) accommodated in the RU#1 (211) based on the transmission period.

[0083] Returning to FIG. 5, in step S153, if there is another transmission period with a short overlapping period (Y in step S153), the process proceeds to step S154. On the other hand, if there is no other transmission period with a short overlapping period (N in step S153), the process proceeds to step S155.

[0084] Note that even when there is no overlapping period, that is, when there is no overlapping period between the transmission period of the video frame transmitted from UE100 and the transmission period of the video frame transmitted from another UE, it is also determined as "Y" in step S153. This is because if there is no overlapping period, it is possible to suppress the transmission delay even if UE100 is handed over to another cell (or another RU).

[0085] In step S154, the control unit 252 hands over UE100 to another cell or another RU. In the example described above, the control unit 252 hands over UE100 to another cell (or RU#2(221)) under RU#1(211).

[0086] In step S155, the control unit 252 ends a series of processes.

[0087] FIG. 7 is a diagram showing an operation example of handover according to the first embodiment. FIG. 7 shows an example in which the connection destination of UE100 is switched from RU#1(211) (or RAN#1(210)) to RU#2(221) (RAN#2(220)) by handover within the CU.

[0088] In step S16, the CU250 transmits a UE context setup request (UE CONTEXT SETUP REQUEST) to RAN#2(220).

[0089] In step S17, RAN#2(220) transmits a UE context setup response (UE CONTEXT SETUP RESPONSE) to CU250.

[0090] In step S18, the CU250 transmits a UE context modification request (UE CONTEXT MODIFICATION REQUEST) including RRC reconfiguration (RRCReconfiguration) to RAN#1(210).

[0091] In step S19, RAN#1(210) transmits RRC re - establishment to UE100.

[0092] In step S20, UE100 executes a Random Access Procedure for the target RAN#2(220).

[0093] In step S21, UE100 transmits RRCReconfigurationComplete to RAN#2(220).

[0094] In step S22, CU250 transmits a UE CONTEXT RELEASE COMMAND to RAN#1(210).

[0095] In step S23, after deleting the UE context of UE100, RAN#1(210) transmits UE CONTEXT RELEASE COMPLETE to CU250.

[0096] Note that when switching cells instead of RUs, if "RAN#2" in FIG. 7 is changed to "another cell that becomes the connection destination of UE100", it can be implemented in the same way as FIG. 7.

[0097] In the example shown in FIG. 7, an example of handover where UE100 switches the connection destination while remaining in the RRC connected state is shown, but the first embodiment is not limited to this. For example, it is also possible in the case of Redirection where UE100 once migrates to the RRC idle state and then establishes an RRC connection with the switching destination.

[0098] (2) Case where gNB200 detects video data that increases periodically Next, an operation example of the case where gNB200 detects video data that increases periodically will be described.

[0099] FIG. 8 is a diagram showing an operation example in the case according to the first embodiment. Before the operation shown in FIG. 8 is started, it is assumed that the UE 100 is wirelessly connected to the RU #1 (211) of the RAN #1 (210) and is performing wireless communication with the RU #1 (211).

[0100] In step S30, the UE 100 executes an application program related to streaming.

[0101] In step S31, the CU 250 starts monitoring the data amount in the UL direction. The CU 250 may monitor the data amount for each transmission source (or destination) based on the transmission source (or destination) of the received packet.

[0102] Steps S32 to S35 represent an example of the PDU session establishment procedure. Steps S32 to S35 are the same as steps S11 to S14 in FIG. 4. However, in steps S32 and S33, four parameters (information indicating that it is (real-time) streaming, average throughput, interval between video frames of video data, and start timing of video frames) are not transmitted. Note that steps S30 and S31 may be performed after the PDU session is established (steps S32 to S35).

[0103] In step S35, the CU 250 specifies the increase timing and the period. For example, the CU 250 measures the timing at which the video data transmitted from the UE 100 increases by more than the data threshold within a certain period, and the period of the timing. The period of the timing represents the interval when the timing is repeated. Then, the CU 250 calculates the transmission period required for transmitting the video data received from the UE 100 to the CN 300 based on the increase timing and the period.

[0104] As described above, the increase timing is the start timing of the transmission period. Also, the period represents the length of the transmission period. The transmission period is represented by the increase timing and the period.

[0105] In step S36, CU250 performs DU selection processing. Since the transmission period has been calculated, the DU selection processing can be implemented with reference to FIG. 5 in the same manner as in the above (1). The control unit 252 of CU250 performs DU selection processing by executing steps S152 to S155.

[0106] Thereafter, when CU250 determines to perform a handover to the UE (step S154 in FIG. 5), it performs a handover to UE100 according to the operation example shown in FIG. 7 and switches the connection destination of UE100 to another cell or another RU.

[0107] Although the operation examples of (1) and (2) described above explain the RU connection switching, since RU#1 (211) is connected to DU#1 (212) and RU#2 (221) is connected to DU#2 (222), the connection switching of the DU will be performed simultaneously with the connection switching of the RU. Therefore, a handover to another RU has the same meaning as a handover to another DU.

[0108] [Other Embodiments] A program for causing a computer to execute each process according to the above-described embodiment may be provided. The program may be recorded on a computer-readable medium. By using the computer-readable medium, it is possible to install the program on the computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. Such a recording medium may be included in the control unit 252 of the CU250 and the control unit 2121 of the DU#1(212). The control unit 252 of the CU250 and the control unit 2121 of the DU#1(212) may realize the functions described in the above-described embodiment by reading out and executing the program from the recording medium. Therefore, the control unit 252 and the control unit 2121 may be a processor or a controller such as a CPU (Central Processing Unit) or a DSP (Digital Signal Processor).

[0109] As used in this disclosure, the terms "based on" and "depending on" do not mean "only based on" or "only depending on" unless otherwise specified. The term "based on" means both "only based on" and "at least partially based on". Similarly, the term "depending on" means both "only depending on" and "at least partially depending on". Also, the terms "include", "comprise", and their variants do not mean to include only the listed items, but may include only the listed items or may further include additional items in addition to the listed items. Further, the term "or" as used in this disclosure is not intended to be exclusive. Additionally, any reference to an element using designations such as "first", "second", etc. used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used in this specification as a convenient way to distinguish between two or more elements. Thus, a reference to a first and a second element does not mean that only two elements can be employed there or that the first element must precede the second element in any form. In this disclosure, for example, when articles are added by translation such as a, an, and the in English, these articles shall be construed to include plural ones unless the context clearly indicates otherwise.

[0110] As described above in detail with reference to the drawings, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the gist. Also, within a non - conflicting range, it is possible to combine each embodiment, each operation example, or each process.

[0111] This application claims the priority of Japanese Patent Application No. 2022 - 054673 (filed on March 29, 2022), and all of its contents are incorporated into this application specification.

[0112] (Appendix) Append the features related to the above embodiments.

[0113] (1) A first radio unit that performs wireless communication with a first user device, A second radio unit, A first distributed unit connected to the first radio unit, A second distributed unit connected to the second radio unit, A control unit that controls the first distributed unit and the second distributed unit, Based on a first transmission period for transmitting first video data received from the first user device to a core network, the control unit switches the connection destination of the first user device from the first radio unit to the second radio unit. Base station.

[0114] (2) When the first user device is performing the wireless communication in a first cell accommodated in the first radio unit, instead of moving the connection destination of the first user device to the second radio unit, based on the first transmission period, the control unit switches from the first cell to a second cell accommodated in the first radio unit. The base station according to (1) above.

[0115] (3) The first user device transmits information indicating that it is streaming, an average throughput, an interval between video frames of the first video data, and a start timing of the video frame to the control unit. Based on the information indicating that it is streaming, the average throughput, the interval of the video frames, and the start timing of the video frames, the control unit calculates the first transmission period. The base station according to (1) or (2) above.

[0116] (4) The control unit measures the timing at which the first video data increases by a data threshold or more within a certain period and the period of the timing based on the first video data, and calculates the first transmission period based on the timing and the period. The base station according to any one of (1) to (3) above.

[0117] (5) When there is a first overlapping period between the second transmission period for transmitting the second video data transmitted from the second user device that is performing wireless communication with the control unit and the second wireless unit and the first transmission period, the control unit switches the connection destination of the first user device to the second wireless unit. The base station according to any one of (1) to (4) above.

[0118] (6) When there is the first overlapping period, and when a second overlapping period between the third transmission period of the third video data transmitted from the third user device that performs wireless communication with the first wireless unit and the first transmission period is equal to or less than a period threshold, the control unit switches the connection destination of the first user device to the second wireless unit. The base station according to any one of (1) to (5) above.

[0119] (7) The first radio unit connected to the first distributed unit performs wireless communication with the first user device. The control unit has controlling the first distributed unit and the second distributed unit connected to the second distributed unit. The controlling includes switching the connection destination of the first user device from the first radio unit to the second radio unit based on the first transmission period for transmitting the first video data received from the first user device to the core network. Communication control method.

Explanation of Signs

[0120] 10: Mobile communication system 100: UE 200: gNB (Base Station) 210: RAN#1 211: RU#1 212: DU#1 220: RAN#2 221: RU#2 222: DU#2 230: RAN#3 231: RU#3 232: DU#3 250: CU 252: Control Unit 300: CN 2121: Control Unit

Claims

1. A first radio unit that performs wireless communication with a first user device, a second radio unit, a first distributed unit connected to the first radio unit, a second distributed unit connected to the second radio unit, and a control unit that controls the first distributed unit and the second distributed unit, wherein the control unit switches the connection destination of the first user device from the first radio unit to the second radio unit based on a first transmission period for transmitting first video data received from the first user device to a core network. Base station.

2. When the first user device is performing the wireless communication in a first cell accommodated in the first radio unit, the control unit switches the connection destination of the first user device from the first cell to a second cell accommodated in the first radio unit based on the first transmission period instead of moving the connection destination to the second radio unit. The base station according to Claim 1.

3. The first user device transmits information indicating that it is streaming, an average throughput, an interval between video frames of the first video data, and a start timing of the video frame to the control unit. The control unit calculates the first transmission period based on the information indicating that it is streaming, the average throughput, the interval of the video frames, and the start timing of the video frames. The base station according to Claim 1.

4. The control unit measures a timing at which the first video data increases by more than a data threshold within a certain period and a period of the timing based on the first video data, and calculates the first transmission period based on the timing and the period. The base station according to Claim 1.

5. When there is a first overlapping period between a second transmission period for transmitting second video data transmitted from a second user device that is performing wireless communication with the second radio unit and the first transmission period, the control unit switches the connection destination of the first user device to the second radio unit. The base station according to Claim 1.

6. When the first overlapping period exists and a second overlapping period between a third transmission period of third video data transmitted from a third user device that is performing wireless communication with the first radio unit and the first transmission period is equal to or less than a period threshold, the control unit switches the connection destination of the first user device to the second radio unit. The base station according to claim 5.

7. A first radio unit connected to the first distributed unit performs wireless communication with a first user device, A control unit controls the first distributed unit and a second distributed unit connected to a second radio unit, The controlling includes switching a connection destination of the first user device from the first radio unit to the second radio unit based on a first transmission period for transmitting first video data received from the first user device to a core network. Communication control method.

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