JP7698793B2 - Base station and communication control method - Google Patents

Description

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

Recently, 5th generation mobile communication systems that can be used by various entities according to regional or individual needs have been attracting attention. Such mobile communication systems are sometimes called local 5G (5th Generation), for example.

Local 5G allows various entities, such as local companies and local governments, to build their own spot networks within their own buildings or on their premises, separate from the nationwide 5G systems provided by mobile carriers. For this reason, local 5G is expected to be used to meet a variety of needs closely tied to local communities.

In the field of mobile communications, for example, there is the following technology. That is, there is a base station device that monitors the situation related to communication with terminals, and if a change in the situation is detected, sets priorities for each terminal, and if the total communication bandwidth required for communication with each terminal exceeds the available communication bandwidth, temporarily restricts communication with terminals in descending order of priority (for example, Patent Document 1 below).

Re-table 2008/126260 publication

A base station according to a first aspect is a base station that performs wireless communication with a first user device. The base station has a first wireless unit that performs wireless communication with the first user device and a second wireless unit. The base station also has a first distributed unit connected to the first wireless unit and a second distributed unit connected to the second wireless unit. Furthermore, the base station has 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 wireless unit to the second wireless unit based on a first transmission period for transmitting the first video data received from the first user device to the core network.

The communication control method according to the second aspect is a communication control method in a base station. The base station has a first wireless unit and a second wireless unit that perform wireless communication with a first user device. The base station also has a first distributed unit connected to the first wireless unit and a second distributed unit connected to the second wireless unit. The base station further has 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 wireless unit to the second wireless unit based on a first transmission period for transmitting the first video data received from the first user device to the core network.

FIG. 1 is a diagram illustrating an example of the configuration of a mobile communication system according to the first embodiment. FIG. 2A is a diagram showing an example of the configuration of a CU according to the first embodiment, and FIG. 2B is a diagram showing an example of the configuration of a DU according to the first embodiment. FIG. 3 is a diagram illustrating an example of the configuration of an RU according to the first embodiment. FIG. 4 is a diagram illustrating an example of an operation according to the first embodiment. FIG. 5 is a diagram showing an example of the operation of the DU selection process according to the first embodiment. FIG. 6 is a diagram illustrating an example of an overlapping period according to the first embodiment. FIG. 7 is a diagram illustrating an example of a handover operation according to the first embodiment. FIG. 8 is a diagram illustrating an example of an operation according to the first embodiment.

One aspect of the present disclosure aims to reduce delays in the transmission of video data.

[First embodiment]
Local 5G may be used to support remote work in factories, etc. For example, a camera is installed on each terminal, and an administrator checks whether work is being performed properly based on the video data transmitted from each terminal. In such a use case, video data with a resolution of "4K" or higher is transmitted from each terminal, and a higher throughput is required in the uplink direction than in the downlink direction.

With video data of 4K or higher, the data exists in bursts for each video frame, and a video frame can contain many times the data of the average throughput. This can be particularly noticeable during the start-up period of a video frame. When this type of video data is transmitted simultaneously from multiple terminals, it momentarily places a heavy load on 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 transmission delays.

For example, in the above-mentioned Patent Document 1, if a terminal transmitting "4K" video data has a low priority and communication is temporarily restricted, the terminal must wait until the restriction is lifted before transmitting the video data to the core network, resulting in a transmission delay.

Therefore, in the first embodiment, the aim is to suppress delays in transmitting video data at base stations.

Hereinafter, an embodiment 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.

[Example of a mobile communication system configuration]
FIG. 1 is a diagram illustrating an example of the configuration of a mobile communication system 10 according to the first embodiment.

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

UE100 is a mobile wireless communication device that performs wireless communication with gNB200. UE100 may be any device that performs wireless communication with gNB200. For example, UE100 is a mobile phone terminal, a tablet terminal, a notebook PC, a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle, or an aircraft or a device provided in an aircraft. In the example of FIG. 1, an example of one UE100 is shown, but there may be multiple UE100.

gNB200 is a wireless communication device that performs wireless communication with UE100. gNB200 performs wireless communication with UE100 that has established a connection with its own cell. gNB200 performs wireless communication with UE100 to provide various services to UE100. gNB200 is also a communication device that performs wired communication with CN300. gNB200 is an example of a base station. gNB200 functions as a base station in a 5G system. gNB200 may be an en-gNB that can be connected to a base station in a 4G system (i.e., an eNB (evolved Node B)). gNB200 may also be a base station for a 6G system or later.

In addition, in a 5G system, the network between UE100 and gNB200 may be called NG-RAN (Next Generation-Radio Access Network) or RAN.

CN300 is a network between gNB200 and functional units (or functional entities) within CN300. Functional units within CN300 include SMF (Session Management Function), AMF (Access and Mobility Management Function), and UPF (User Plane Function). The SMF within CN300 and the like establish or update PDU sessions. In addition, the functional units within CN300 can transmit user data to UE100 via gNB200, or transmit user data transmitted from UE100 to other networks.

(Example of gNB configuration)
Next, an example configuration of gNB200 will be described.

As shown in FIG. 1, gNB 200 has CU (Central Unit) 250, multiple DUs (Distributed Units) 212, 222, 232, and multiple RUs (Radio Units) 211, 221, 231. gNB 200 allows a configuration in which multiple DUs 212, 222, 232 are connected to one CU 250. With such a configuration, for example, it is possible to separate the functions of CU 250 and DUs 212, 222, 232, and prevent processing delays. Note that while the example of FIG. 1 shows an example of three DUs 212, 222, 232, there may be two or four or more DUs.

CU250 may be referred to as, for example, an aggregation unit or a control unit. CU250 is connected to each DU212, 222, 232 and controls each DU212, 222, 232. CU250 can select one of the multiple DU212, 222, 232 and communicate with UE100. CU250 is connected to CN300 and transmits and receives user data, etc., between CN300.

Each DU 212, 222, 232 may be referred to as a distributed unit, for example. DU #1 (212) is connected to CU 250 and also to RU #1 (211). DU #2 (222) is connected to CU 250 and also to RU #2 (221). DU #3 (232) is connected to CU 250 and also to RU #3 (231). Each DU 212, 222, 232 has a scheduler and performs scheduling processing such as allocating radio resources to UE 100.

Each of RUs 211, 221, and 231 may be referred to as a wireless unit, for example. RU #1 (211) is controlled by DU #1 (212) and is capable of wireless communication with UE 100. RU #2 (221) is controlled by DU #2 (222) and is capable of wireless communication with UE 100. RU #3 (231) is controlled by DU #3 (232) and is capable of wireless communication with UE 100.

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

(Examples of CU, DU, and RU configurations)
Next, configuration examples of CU250, DU#1 (212), and RU#1 (211) of gNB200 will be described. For DU212, 222, and 232, DU#1 (212) will be described as a representative, but the other DU222 and 232 have the same configuration as DU#1 (212). For RU211, 221, and 231, RU#1 (211) will be described as a representative, but the other RU221 and 231 have the same configuration as RU#1 (211).

Figure 2 (A) is a diagram showing an example configuration of CU250 relating to the first embodiment.

As shown in FIG. 2(A), CU 250 has an interface unit 251 and a control unit 252.

Under the control of the control unit 252, the interface unit 251 transmits and receives messages to and from the CN 300, and transmits and receives messages to and from any of the multiple DUs 212, 222, 232. For example, the interface unit 251 transmits and receives messages of the NG interface to the CN 300, and transmits and receives messages of the F1 interface to and from each DU 212, 222, 232.

The control unit 252 performs various controls in the CU 250. 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 processing by the processor. The processor executes the programs stored in the memory to perform various processes. Note that in each of the embodiments described below, each process or operation in the CU 250 of the gNB 200 may be performed by the control unit 252.

Figure 2 (B) is a diagram showing an example configuration of DU #1 (212) in the first embodiment.

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

Under the control of the control unit 2121, the interface unit 2120 transmits and receives messages between the CU 250 and the RU #1 (211). For example, the interface unit 2120 transmits and receives messages of the F1 interface between the CU 250 and the RU #1 (211), and transmits and receives messages of the O-RAN (Open Radio Access Network) fronthaul specification between the CU 250 and the RU #1 (211).

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 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 described below, each process or operation in DU 212, 222, 232 of gNB 200 may be performed by the control unit 2121.

Figure 3 is a diagram showing an example configuration of RU #1 (211) in the first embodiment.

The interface unit 2110 transmits and receives messages to and from DU#1 (212), and transmits and receives data, etc. to and from the wireless processing unit 2111. That is, the interface unit 2110 extracts data or control signals, etc. from messages received from DU#1 (212), and outputs the extracted data or control signals, etc. to the wireless processing unit 2111. In addition, the interface unit 2110 generates a message in a specified format (e.g., O-RAN fronthaul) that includes the data or control signals, etc. output from the wireless processing unit 2111, and outputs the message to DU#1 (212).

The wireless processing unit 2111 converts (up-converts) the data or control signal output from the interface unit 2110 into a wireless signal in the wireless band, and outputs the wireless signal to the antenna 2112. The wireless processing unit 2111 also converts (down-converts) the wireless signal output from the antenna 2112 into data or a wireless signal in the baseband band, and outputs the data or wireless signal to the interface unit 2110.

The antenna 2112 transmits the radio signal output from the radio processing unit 2111 to the UE 100. The antenna 2112 also receives the radio signal transmitted from the UE 100 and outputs the received radio signal to the radio processing unit 2111.

(QoS Flow)
Here, the QoS flow according to the first embodiment will be described.

In a 5G system, it is possible to provide QoS (Quality of Service) services on an IP flow basis to UE 100. The QoS flow is established when a PDU (Protocol Data Unit) session is established (PDU Session Establishment) or updated (PDU Session Modification). The QoS flow may be pre-configured.

QoS flow is the finest granularity in distinguishing QoS in a PDU session. QoS flow is established between UE100 and UPF of CN300 under the control of SMF of CN300. QoS service makes it possible to provide UE100 with a service with a specified quality.

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

The QoS profile includes 5QI (5G QoS Identifier), QoS flow bit rate guarantee (GFBR: Guaranteed Flow Bit Rate), and QoS flow maximum bit rate (MFBR: Maximum Flow Bit Rate). 5QI is used to identify each QoS and represents the characteristics of the QoS. SMF transmits the QoS profile and QFI to gNB200. gNB200 establishes a data radio bearer (DRB) together with the PDU session and maps one PDU session to one DRB. gNB200 maps the QoS flow to the DRB based on the QoS profile and QFI.

The QoS rules include a 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. The information includes destination and source IP addresses, destination and source MAC addresses, etc. The SMF transmits the QoS rules, etc. to UE 100. UE 100 uses the QoS rules to link UL traffic to a QoS flow.

The PDR contains information for classifying packets (i.e., PDU packets) arriving at the UPF. The PDR contains information for mapping user plane traffic to QoS flows. The SMF sends the PDR etc. to the UPF. The UPF uses this information to classify user plane traffic, enforce bandwidth, mark etc.

In the NAS layer of UE100 and UPF, UL packets and DL packets (i.e., IP flows) are linked to QoS flows. In addition, in the AS layer (i.e., SDAP (Service Data Adaption Protocol) layer) of UE100 and gNB200, QoS flows are linked to DRBs. With this two-stage mapping, the mobile communication system 10 can map packets to appropriate QoS flows and appropriate DRBs, thereby ensuring service quality.

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

In the first embodiment, CU250 (e.g., a control unit) switches the connection destination of UE100 from RU#1 (211) (e.g., a first wireless unit) to RU#2 (221) (e.g., a second wireless unit) based on a transmission period (e.g., a first transmission period) required for transmitting video data (e.g., first video data) received from UE100 (e.g., a first user equipment) to a core network.

For example, when UE100 and another UE are performing wireless communication with RU#1 (211), if the video data transmission period in UE100 overlaps with the video data transmission period in the other UE, UE100 is moved from RU#1 (211) to RU#2 (221).

As a result, for example, DU #2 (222) (e.g., second distributed unit) that processes video data transmitted from UE 100 and DU #1 (212) (e.g., first distributed unit) that processes video data transmitted from other UEs are different DUs, making it possible to suppress transmission delays of video data in gNB 200. In addition, since the transmission load of video data is not concentrated on DU #1 (212) but is distributed to DU #1 (212) and DU #2 (222), the transmission load can be distributed.

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

In the above case (1), UE100 transmits parameters to CN300 at the time of PDU Session Establishment or PDU Session Modification. The parameters are information indicating (real-time) streaming, average throughput, interval between video frames of video data, and start timing of video frames. Here, the average throughput may be based on the amount of video data transmitted in a certain period of time previously measured by UE100. The interval between video frames represents the interval between a certain 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. UE100 may transmit an RRC message including these parameters to CU250. CU250 calculates the transmission period required for gNB200 to transmit the video data received from UE100 to CN300 based on these parameters. The transmission period includes the transmission period required to transmit one video frame.

In the above case (2), CU250 monitors the video data transmitted from UE100 and measures the timing at which the video data increases by more than the data threshold and the period of the 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 period. In the above case (2), the timing and period represent the start timing and transmission period of the transmission period, that is, the transmission period itself. Note that the above case (2) is not performed at the time of PDU Session Establishment or PDU Session Modification, but is performed at the timing when CU250 detects that the video data increases by more than the data threshold.

Below, we will explain the operation examples in two cases separately.

(1) Case in which parameters are transmitted from UE 100 Next, an example of operation in a case in which parameters are transmitted from UE 100 will be described.

Figure 4 is a diagram showing an example of operation in this case according to the first embodiment. Note that before the example of operation shown in Figure 4 is started, UE100 is wirelessly connected to RU#1 (211) of RAN#1 (210) and is performing wireless communication.

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

Steps S11 to S14 represent an example of a procedure for establishing a PDU session for transmitting video via streaming.

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

In step S12, CN300 transmits an N2PDU session request to CU250. The N2PDU session request includes a PDU session ID. The N2PDU session request also includes a PDU session establishment accept that allows the establishment of the requested PDU session. The N2PDU session request also includes N2 SM information, etc. The N2 SM information includes a QoS profile and a QFI. By receiving the N2PDU session request, CU250 can determine that a QoS flow has been established based on the N2 SM information. Furthermore, CN 300 may include the four parameters in N2 SM information and transmit it to CU 250. CN 300 may include the four parameters in an N2 PDU session request or a PDU session establishment permission and transmit it to CU 250. This allows CU 250 to obtain the four parameters transmitted from UE 100 via CN 300.

In step S13, UE100 and CU250 execute AN-specific resource setup via RAN#1 (210). Specifically, CU250 transmits a PDU session ID, a PDU session establishment acceptance, and the like to UE100 via RAN#1 (210).

In step S14, CU 250 transmits an N2 PDU session response to CN 300. The N2 PDU session response includes a PDU session ID, N2 SM information, etc.

As a result, a PDU session including a QoS flow is established between UE100 and the UPF.

In step S15, CU250 performs DU selection processing.

Figure 5 is a flowchart illustrating an example of a DU selection process for one embodiment.

As shown in FIG. 5, in step S150, the control unit 252 of the CU 250 starts processing.

In step S151, the control unit 252 calculates the transmission period required to transmit one video frame. At the time of step S151 or before step S151, the control unit 252 is assumed to have received four parameters (information indicating (real-time) streaming, average throughput, interval between video frames of the video data, and start timing of the video frames) from the UE 100.

For example, the control unit 252 calculates the transmission period using these parameters as follows. That is, the control unit 252 starts calculating the transmission period based on information indicating streaming. The control unit 252 sets the start timing of the video frame as the start timing of the transmission period. Then, the control unit 252 assumes that the average throughput is the amount of video data for one video frame and calculates the period required for the CU 250 to transmit this amount of video data to the CN 300. The start timing of the video frame becomes the start timing of the video frame transmission period, and the time required to transmit this amount of video data represents the length of the transmission period.

In step S152, the control unit 252 determines whether the transmission period overlaps with another transmission period. In step S152, if the transmission period overlaps with another transmission period (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 another transmission period (N in step S152), the process proceeds to step S155.

Here, "another transmission period" refers to a transmission period (e.g., a second transmission period) of video data (e.g., second video data) transmitted from another UE (e.g., a second user device) that is performing wireless communication in the same cell as the cell in which UE100 performs wireless communication. Also, "another transmission period" refers to a transmission period of video data transmitted from another UE that is performing wireless communication with the same RU as RU #1 (211) with which UE100 is performing wireless communication. In step S152, the control unit 252 determines whether or not there is an overlapping period (e.g., a first overlapping period) between the transmission period (e.g., a first transmission period) of the video data transmitted from UE100 and the other transmission period (e.g., a second transmission period) transmitted from the other UE.

Figure 6 is a diagram showing an example of an overlapping period in the first embodiment.

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 a video frame transmitted from another UE. The transmission period of video frame #1 starts at "12:00:00" and lasts for 30 seconds until "12:00:30". The transmission period of video frame #2 (i.e., "another transmission period") starts at "12:00:10" and lasts for 40 seconds until "12:00:40". Therefore, there is an overlap period (e.g., a first overlap period) of 20 seconds from "12:00:10" to "12:00:30". In the first embodiment, the existence of such an overlap period is said to cause a transmission delay in CU250.

In addition, step S152 can be considered as, for example, determining whether or not to hand over UE 100 to another cell (or another RU). If there is no overlapping period, there is no need to hand over UE 100.

Note that even if an overlapping period exists, if it is less than the threshold, there may be cases where no transmission delay occurs in the cell (or RU). Therefore, CU250 may determine whether the overlapping period is equal to or greater than the threshold, and if it is equal to or greater than the threshold (Y in step S152), proceed to step S153, and if it is not (N in step S152), proceed to step S155.

Returning to FIG. 5, in step S153, the control unit 252 determines whether there is another transmission period in which the overlapping period (e.g., the second overlapping period) is less than or equal to the period threshold.

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

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

For example, assume that a transmission delay occurs in video frame #1 in FIG. 6. By placing video frame #1 after video frame #3, the start timing of video frame #1 can be set to "12:00:18", which can be made earlier than the start timing being set to "12:00:40" after video frame #2. Therefore, the transmission delay of video frame #1 can be suppressed.

In step S153, it can be considered that CU250 determines whether or not a transmission delay will occur in another cell (or another RU) even if UE100 is handed over to the other cell (or another RU). This is because if the "other transmission period" is shorter than the period threshold, it is possible to suppress the transmission delay even if UE100 is handed over to another cell (or another RU).

Here, the period threshold may be a threshold that allows a transmission delay to be tolerated in a cell (or RU). The period threshold may also be a threshold determined by the capacity of a cell (or RU) to process video data within a specified period. The period threshold may be a different threshold for each cell or RU.

As described above, the destination of UE100 can be another cell or another RU. In the case of another cell, when UE100 is performing wireless communication in a cell (e.g., the first cell) accommodated in RU#1 (211), the control unit 252 switches the connection destination of UE100 from the cell to another cell (e.g., the second cell) accommodated in RU#1 (211) based on the transmission period.

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 another transmission period with a short overlapping period (N in step S153), the process proceeds to step S155.

In addition, if there is no overlapping period, i.e., if 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, step S153 is also determined to be "Y". This is because if there is no overlapping period, it is possible to suppress transmission delays even if UE100 is handed over to another cell (or another RU).

In step S154, the control unit 252 hands over the UE 100 to another cell or another RU. In the above example, the control unit 252 hands over the UE 100 to another cell (or RU #2 (221)) under the control of RU #1 (211).

In step S155, the control unit 252 terminates the series of processes.

Figure 7 is a diagram showing an example of handover operation according to the first embodiment. Figure 7 shows an example of switching the connection destination of UE100 from RU#1 (211) (or RAN#1 (210)) to RU#2 (221) (RAN#2 (220)) by intra-CU handover.

In step S16, CU250 sends a UE context setup request (UE CONTEXT SETUP REQUEST) to RAN#2 (220).

In step S17, RAN #2 (220) sends a UE context setup response (UE CONTEXT SETUP RESPONSE) to CU 250.

In step S18, CU250 sends a UE context update request (UE CONTEXT MODIFICATION REQUEST) including RRC reestablishment (RRCReconfiguration) to RAN#1 (210).

In step S19, RAN #1 (210) sends RRC re-establishment to UE 100.

In step S20, UE100 performs a random access procedure with RAN#2 (220) to which it will connect.

In step S21, UE100 sends RRC reestablishment completion (RRCReconfigurationComplete) to RAN#2 (220).

In step S22, CU250 sends a UE context release command (UE CONTEXT RELEASE COMMAND) to RAN#1 (210).

In step S23, RAN #1 (210) deletes the UE context of UE 100 and then sends a UE context release completion (UE CONTEXT RELEASE COMPLETE) to CU 250.

In addition, if switching cells rather than switching RUs, the same implementation as in Figure 7 can be achieved by changing "RAN #2" in Figure 7 to "another cell to which UE 100 will connect."

7 shows an example of handover in which UE100 switches the connection destination while remaining in the RRC connected state, but the first embodiment is not limited to this. For example, it can also be implemented in the case of redirection in which UE100 transitions to the RRC idle state once and then performs RRC connection with the switching destination.

(2) Case where gNB200 detects periodically increasing video data Next, we will explain an example of operation in the case where gNB200 detects periodically increasing video data.

Figure 8 is a diagram showing an example of operation in this case according to the first embodiment. Note that before the operation shown in Figure 8 is started, UE100 is wirelessly connected to RU#1 (211) of RAN#1 (210) and is performing wireless communication with RU#1 (211).

In step S30, UE100 executes an application program related to streaming.

In step S31, CU250 starts monitoring the amount of data in the UL direction. CU250 may monitor the amount of data for each source (or destination) based on the source (or destination) of the received packet.

Steps S32 to S35 show an example of a procedure for establishing a PDU session. 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 (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).

In step S35, CU250 identifies the increase timing and period. For example, CU250 measures the timing at which the video data transmitted from UE100 increases by more than a data threshold within a certain period of time, and the period of that timing. The period of that timing represents the interval at which that timing is repeated. Then, CU250 calculates the transmission period required to transmit the video data received from UE100 to CN300 based on the increase timing and period.

As mentioned above, the increase timing is the start timing of the transmission period. Also, the period represents the length of the transmission period. The increase timing and period represent the transmission period.

In step S36, the CU 250 performs a DU selection process. Since the transmission period has been calculated, the DU selection process can be performed according to FIG. 5, as in (1) above. The control unit 252 of the CU 250 performs the DU selection process by executing steps S152 to S155.

Thereafter, if CU250 decides 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.

Note that, in both the above-mentioned operation examples (1) and (2), the connection switching of the RU is explained, but 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 RU simultaneously switches the connection of the DU. Therefore, handover to another RU has the same meaning as handover to another DU.

[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 in a computer-readable medium. Using a computer-readable medium, it is possible to install the program in a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient 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 CU 250 and the control unit 2121 of the DU #1 (212). The control unit 252 of the CU 250 and the control unit 2121 of the DU #1 (212) may realize the functions described in the above-described embodiment by reading and executing the program from the recording medium. Therefore, the control unit 252 and the control unit 2121 may be a processor or controller such as a CPU (Central Processing Unit) or a DSP (Digital Signal Processor).

As used in this disclosure, the terms "based on" and "depending on" do not mean "based only on" or "depending only on", unless otherwise specified. The term "based on" means both "based only on" and "based at least in part on". Similarly, the term "depending on" means both "based only on" and "depending at least in part on". In addition, the terms "include", "comprise", and variations thereof do not mean including only the items listed, but may include only the items listed, or may include additional items in addition to the items listed. In addition, the term "or" as used in this disclosure is not intended to be an exclusive or. Furthermore, any reference to elements using designations such as "first", "second", etc., as used in this disclosure is not intended to generally limit the quantity or order of those elements. These designations may be used herein as a convenient way to distinguish between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some manner. In this disclosure, where articles are added by translation, such as, for example, a, an, and the in English, these articles are intended to include the plural unless the context clearly indicates otherwise.

Although the embodiments have been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design changes, etc. are possible without departing from the scope of the invention. In addition, it is also possible to combine the various embodiments, operation examples, or processes as long as they are not inconsistent.

This application claims priority to Japanese Patent Application No. 2022-054673 (filed March 29, 2022), the entire contents of which are incorporated herein by reference.

(Additional Note)
The following additional features relate to the above-described embodiment.

(1)
a first wireless unit configured to wirelessly communicate with a first user device;
A second wireless unit;
a first distributed unit connected to the first wireless unit;
a second distributed unit connected to the second wireless unit;
a control unit that controls the first distribution unit and the second distribution unit,
the control unit switches a connection destination of the first user device from the first wireless unit to the second wireless unit based on a first transmission period required for transmitting the first video data received from the first user device to a core network.
Base station.

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

(3)
the first user device transmits, to the control unit, information indicating streaming, an average throughput, an interval between video frames of the first video data, and a start timing of the video frames;
the control unit calculates the first transmission period based on the information indicating streaming, the average throughput, the interval between the video frames, and the start timing of the video frames.
A base station according to (1) or (2) above.

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

(5)
the control unit, when a first overlapping period exists between a second transmission period for transmitting second video data transmitted from a second user device wirelessly communicating with the second wireless unit and the first transmission period, switches a connection destination of the first user device to the second wireless unit.
A base station according to any one of (1) to (4) above.

(6)
the control unit, 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 wirelessly communicates with the first wireless unit and the first transmission period is equal to or less than a period threshold, switches a connection destination of the first user device to the second wireless unit.
A base station according to any one of (1) to (5) above.

(7)
a first wireless unit connected to the first distributed unit wirelessly communicating with a first user equipment;
A control unit controls the first distribution unit and a second distribution unit connected to the second distribution unit;
The controlling includes switching a connection destination of the first user device from the first wireless unit to the second wireless unit based on a first transmission period required for transmitting first video data received from the first user device to a core network.

10: Mobile communication systems
100: UE
200: Base station (gNB)
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: C.U.
252: control unit
300:CN
2121: control unit

Claims (7)

a first wireless unit configured to wirelessly communicate with a first user device;
A second wireless unit;
a first distributed unit connected to the first wireless unit;
a second distributed unit connected to the second wireless unit;
a control unit that controls the first distribution unit and the second distribution unit,
the control unit switches a connection destination of the first user device from the first wireless unit to the second wireless unit based on a first transmission period required for transmitting the first video data received from the first user device to a core network.
Base station. the control unit, when the first user equipment is performing the wireless communication in a first cell accommodated in the first radio unit, switches a connection destination of the first user equipment from the first cell to a second cell accommodated in the first radio unit based on the first transmission period, instead of moving to the second radio unit.
The base station according to claim 1. the first user device transmits, to the control unit, information indicating streaming, an average throughput, an interval between video frames of the first video data, and a start timing of the video frames;
the control unit calculates the first transmission period based on the information indicating streaming, the average throughput, the interval between the video frames, and the start timing of the video frames.
The base station according to claim 1. the control unit measures, based on the first video data, a timing at which the first video data increases by equal to or more than a data threshold within a certain period and a period of the timing, and calculates the first transmission period based on the timing and the period.
The base station according to claim 1. the control unit, when a first overlapping period exists between a second transmission period for transmitting second video data transmitted from a second user device wirelessly communicating with the second wireless unit and the first transmission period, switches a connection destination of the first user device to the second wireless unit.
The base station according to claim 1. the control unit, 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 wirelessly communicates with the first wireless unit and the first transmission period is equal to or less than a period threshold, switches a connection destination of the first user device to the second wireless unit.
The base station according to claim 5. a first wireless unit connected to the first distributed unit wirelessly communicating with a first user equipment;
A control unit controls the first distributed unit and a second distributed unit connected to the second wireless unit;
The controlling includes switching a connection destination of the first user device from the first wireless unit to the second wireless unit based on a first transmission period required for transmitting first video data received from the first user device to a core network.

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