Scheduling control device, scheduling control system, scheduling control method, and program

Abstract

A scheduling control device for calculating a weight for scheduling on terminals in a wireless system having a plurality of base stations, wherein: the scheduling control device comprises an information acquisition unit for acquiring information pertaining to the connection state between each of the plurality of base stations and a terminal, a weight calculation unit for calculating, for each base station in the plurality of base stations, a weight that indicates the ratio of distribution, among terminals, of a communication volume between a base station and one or a plurality of terminals connected to the base station, and a control unit for notifying the base station regarding the weight; and the weight calculation unit calculates the weight by repeating a process for updating the weight such that an error between expected wireless communication quality obtained when the weight is assigned to each terminal and the required wireless communication quality of each terminal is reduced.

Description

Technical Field

[0001] The present invention relates to a scheduling method in wireless communication.

Background Art

[0002] In a conventional wireless system, a plurality of terminals are connected to a base station, and the base station determines which terminal to communicate with for each time slot. This decision-making process is called scheduling. This may also be called user scheduling. In scheduling, for example, a method such as proportional fairness is used (Non-Patent Document 1).

[0003] In proportional fairness, wireless resources are allocated to a terminal whose expected instantaneous throughput when the wireless resources are allocated is greater than the average throughput until then.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, the number of areas where a plurality of different types of base stations are installed has been increasing. In an area where a plurality of different types of base stations are installed, a situation is assumed in which the connection destination base station and the wireless method (communication method) of each terminal are different.

[0006] On the other hand, the scheduling according to the prior art has been performed in a base station according to the radio communication quality, priority, etc. Therefore, in the prior art, there is a problem that it is impossible to appropriately perform scheduling in a situation where a plurality of different types of base stations are installed and the connection destination base stations and radio systems of each terminal are different from each other.

[0007] The present invention has been made in view of the above points, and an object thereof is to provide a technique for appropriately performing scheduling in a radio system that provides services to users by a plurality of base stations.

Means for Solving the Problems

[0008] According to the disclosed technique, there is provided a scheduling control device that calculates a weight for scheduling for a terminal in a radio system having a plurality of base stations, an information acquisition unit that acquires information on the connection state between each base station and the terminal in the plurality of base stations, a weight calculation unit that calculates, for each base station in the plurality of base stations, a weight indicating the distribution ratio of the traffic between the base station and one or more terminals connected to the base station among the terminals, and a control unit that notifies the base station of the weight, wherein the weight calculation unit calculates the weight by repeating a process of updating the weight so that the error between the expected radio communication quality obtained when the weight is given to each terminal and the required radio communication quality of each terminal is reduced. A scheduling control device is provided.

Effects of the Invention

[0009] According to the disclosed technique, a technique for appropriately performing scheduling in a radio system that provides services to users by a plurality of base stations is provided.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

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Figure 6

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention (hereinafter referred to as "the present embodiments") will be described with reference to the drawings. The embodiments described below are merely examples, and the embodiments to which the present invention is applied are not limited to the following embodiments.

[0012] (Overview of the Embodiment) Fig. 1 shows a configuration example of a wireless system (which may also be called a wireless communication system) assumed in the present embodiment. However, Fig. 1 shows a situation (a prior art situation) where the scheduling control device 100 described later using the technology of the present invention is not used.

[0013] As shown in Fig. 1, this wireless system includes base stations 10A-1, 10A-2, and 10B. Terminals are connected to each base station as shown in the figure. The wireless systems of base stations 10A and 10B are different.

[0014] As an example, base station 10A is a wireless LAN base station (access point), and base station 10B is a base station of a cellular network such as 5G. The terminal can be connected to either base station 10A or base station 10B.

[0015] In a wireless system as shown in FIG. 1, the base station to be connected and the connection method may differ between terminals. Also, scheduling is performed individually at each base station. Therefore, in the prior art, it is not possible to appropriately perform scheduling that can provide the wireless communication quality (e.g., throughput) required by each terminal.

[0016] A configuration example of the wireless system in the present embodiment for solving the above problems is shown in FIG. 2. As shown in FIG. 2, this wireless system includes base stations 10A-1, 10A-2, and 10B. Terminals are connected to each base station as shown. Further, a scheduling control device 100 connected to each base station via a network is provided. In the example of FIG. 2, a plurality of base stations 10A and 10B with different radio systems are shown, but the technology of the present invention is also applicable to a wireless system having a plurality of base stations with the same radio system.

[0017] The scheduling control device 100 calculates a weight for each terminal so that each terminal satisfies the wireless communication quality required by each terminal accommodated in the wireless system having a plurality of base stations, and notifies the calculated weight to each base station. Each base station performs scheduling for each terminal according to the weight calculated by the scheduling control device 100. In the following description, throughput is used as a specific example of the wireless communication quality at the terminal.

[0018] The "weight" for a certain terminal is the ratio of the communication amount allocated to the terminal to the total communication amount that can be allocated at the base station (the base station connected to the terminal) per unit time. In other words, the "weight" indicates the distribution ratio of the communication amount between the base station and one or a plurality of terminals connected to the base station among the terminals.

[0019] "Traffic volume" may be a transmission rate, a line capacity, a traffic amount, a number of packets, a resource amount, a number of symbols, a number of slots, or other amounts. Further, the communication for which traffic volume is allocated may be uplink communication, downlink communication, or both uplink communication and downlink communication.

[0020] Let the "weight" for a certain terminal in a certain base station be w, and let the transmission rate for all terminals connected to the base station be r. Then, the expected throughput s between the base station and the terminal in the terminal is calculated as s = r × w. When the terminal is connected to a plurality of base stations, the sum of r × w for each base station is the expected throughput s.

[0021] (Device Configuration) FIG. 3 shows a configuration diagram of a scheduling control device 100 according to the present embodiment. As shown in FIG. 3, the scheduling control device 100 includes an information acquisition unit 110, a weight calculation unit 120, a control unit 130, and a data storage unit 140.

[0022] The information acquisition unit 110 acquires information such as the connection state between the base station and the terminal from, for example, a control device in a radio system or from each base station. The weight calculation unit 120 calculates a weight. The control unit 130 notifies each base station of the weight information calculated by the weight calculation unit 120.

[0023] The data storage unit 140 stores information necessary for the weight calculation by the weight calculation unit 120. The information necessary for the weight calculation is, for example, the transmission rate of each base station, the required throughput of each terminal, and the like.

[0024] (Operation of Scheduling Control Device 100) Subsequently, an operation example of the scheduling control device 100 will be described according to the procedure of the flowchart shown in FIG. 4.

[0025] <S101: Information acquisition> The information acquisition unit 110 acquires information on base stations and terminals in an area to which the technology according to the present embodiment is applied. For example, the information acquisition unit 110 acquires the connection state between the base station and the terminal (which base station is connected to which terminal) from a control device of the radio system or the like, and acquires the transmission rate (line capacity) of the base station and the required throughput of the terminal from the data storage unit 140.

[0026] <S102: Weight calculation process> In S102, the weight calculation unit 110 performs a weight calculation process. Here, the weight calculation process will be described using the example shown in FIG. 5.

[0027] In the example of FIG. 5, there are base station #1, base station #2, and terminals #1 to #N as weight calculation targets. Note that FIG. 5 may be regarded as a neural network model having base station nodes and terminal nodes, and the nodes are connected by links having weights. The weights become the parameters of the neural network. The weight calculation unit 110 can construct a neural network model based on the information acquired by the information acquisition unit 110.

[0028] In the example of FIG. 5, the terminals connected to base station #1 are terminals #1 and #2, and the terminals connected to base station #2 are terminals #2, #3,..., #N (terminal #N - 1 is not connected).

[0029] Each base station has a transmission rate (line capacity) for terminals (all terminals that can be connected). Here, let the transmission rate of base station #1 be R1 and the transmission rate of base station #2 be R2.

[0030] Using the weights shown in FIG. 5, the expected throughput TH1 (transmission rate that can be achieved by the terminal) of terminal #1 is TH1 = w 11 ×R1, and the expected throughput TH2 of terminal #2 is TH2 = w 12 ×R1 + w 22It becomes ×R2. The throughput for other terminals can be calculated in the same way.

[0031] Here, the sum of the weights for the same base station is 1. That is, w 11 + w 12 = 1, and w 22 + w 23 +.... w 2N = 1. Assume that the initial values of the weights between each base station and each terminal connected to the base station are given in advance.

[0032] For example, if the required throughput (necessary throughput) of terminal #1 is Y1 and Y1 (required throughput) > TH1 (expected throughput), the weight calculation unit 110 updates the weight so as to increase the weight for terminal #1 (that is, w 11 ). That is, the weight calculation unit 110 updates the weight so as to increase the weight for a terminal whose expected throughput is less than the required throughput.

[0033] Here, since the sum of the weights for the same base station is 1, with the update of the weight, other weights are also updated. For example, in base station #1 to which terminal #1 is connected, since w 11 + w 12 = 1, if w 11 is increased, w 12 will decrease.

[0034] By repeating the processes of weight update and expected throughput calculation as described above, the weights are determined so that the expected throughput satisfies the required throughput as much as possible at each terminal.

[0035] More specifically, the weight calculation unit 120 can update the weight according to the following update formula.

[0036] g(W) = (y - w i ·x) 2 ∂g(W) / ∂w i = 2(y - w i ·x) wi = w i + ρ · (∂g(W) / ∂w i ) In the above formula, x represents the transmission rate of the base station. w i represents the weight for terminal #i. Both x and w i are vectors. y is the required throughput of terminal #i.

[0037] w i · x represents the expected throughput of terminal #i. For example, in the situation of FIG. 5, if terminal #i is terminal #2, then w i · x = w 12 × R1 + w 22 × R2.

[0038] For g(w) (the squared value of the difference between the required throughput and the expected throughput), the change amount with respect to w i (∂g(w) / ∂w i ) (= slope) is obtained, and using this slope, w i is updated in the third formula so that g(w) becomes smaller (= the achieved throughput approaches the required throughput). ρ is a predetermined coefficient. This method is a method of the gradient method (which may also be called the gradient descent method).

[0039] Also, similar to the parameter update of the neural network (e.g., the error backpropagation method), w for each terminal can be calculated so as to minimize the following mean squared error (which may also be called "variance"). In the following formula, Σ is the sum over terminals, and N is the number of terminals. i The weight calculation process (the repeated process of weight update and expected throughput calculation) in S102 is repeated until the above mean squared error becomes less than or equal to a predetermined threshold within a predetermined number of repetitions. If, as a result of repeating the predetermined number of times, the mean squared error does not become less than or equal to the predetermined threshold, the process of S102 is terminated there.

[0040] (1 / N)Σ i (y - w i · x) 2 The weight calculation process (the repeated process of weight update and expected throughput calculation) in S102 is repeated until the above mean squared error becomes less than or equal to a predetermined threshold within a predetermined number of repetitions. If, as a result of repeating the predetermined number of times, the mean squared error does not become less than or equal to the predetermined threshold, the process of S102 is terminated there.

[0041] <S103, S104, S105: Weight Output, Required Thruput Update> Next, S103, S104, and S105 in the flow of FIG. 4 will be described.

[0042] In S103, the weight calculation unit 110 determines whether the mean squared error is less than or equal to a threshold value.

[0043] If the determination result of S103 is Yes (mean squared error ≤ threshold value), then in S104, the weight calculation unit 110 passes the weights for all terminals to the control unit 130, and the control unit 130 notifies the weights to each base station. The control unit 130 may notify only the weights related to that base station to the base station. For example, in the example of FIG. 5, for base station #1, w 11 and w 12 are notified.

[0044] Each base station that has received the weights performs scheduling according to the weights. As an example, a communication operation that distributes resources in time division will be described. For example, in the connection state of FIG. 5, the base station #1 that has received w 11 and w 12 communicates with terminal #1 for "w 11 × unit time" and communicates with terminal #2 for "w 12 × unit time".

[0045] If the determination result of S103 is No (mean squared error > threshold value), the process proceeds to S105, and the weight calculation unit 110 updates the required throughput and performs the weight calculation process of S102 using the updated required throughput.

[0046] Since the required throughput is the throughput required by the terminal, basically, if the initially set value can be used as it is, it may be used.

[0047] However, even if the weight update process is repeated, the mean squared error may not fall below the threshold value. In such a case, the required throughput is updated, and the weight update process is performed using the updated required throughput so that the mean squared error falls below the threshold value. By using the weights and the required throughput such that the mean squared error falls below the threshold value, it can be expected that communication that most efficiently uses the radio resources of the radio system can be performed.

[0048] Note that, regarding the required throughput, it is also possible not to set the value corresponding to each terminal first. That is, the initial value of the required throughput may be set to an appropriate value determined in advance.

[0049] The method for updating the required throughput is not limited to a specific method. For example, the following update formula can be used.

[0050] f(W)=(y - w i ·x) 2 ∂f(W) / ∂y = 2(y - w i ·x) y = y + α·(∂f(W) / ∂y) As shown in the above formula, the required throughput y is changed at the rate of change of ∂f(W) / ∂y. α is a coefficient determined in advance. This method is a method of the gradient method (which may also be called the gradient descent method). The larger f(W) (mean squared error) is, the larger |∂f(w) / ∂y| becomes, so y can be changed significantly.

[0051] (Hardware configuration example) The scheduling control device 100, the base station, and the terminal can all be realized, for example, by causing a computer to execute a program. This computer may be a physical computer or a virtual machine on the cloud. The scheduling control device 100, the base station, and the terminal are collectively referred to as devices.

[0052] That is, the apparatus can be realized by executing a program corresponding to the processing performed by the apparatus using hardware resources such as a CPU and a memory built in the computer. The above program can be recorded on a computer-readable recording medium (such as a portable memory), saved, or distributed. Further, it is also possible to provide the above program through a network such as the Internet or e-mail.

[0053] FIG. 6 is a diagram showing an example of the hardware configuration of the computer. The computer in FIG. 6 includes a drive device 1000, an auxiliary storage device 1002, a memory device 1003, a CPU 1004, an interface device 1005, a display device 1006, an input device 1007, an output device 1008, etc., which are mutually connected by a bus BS.

[0054] The program for realizing the processing on the computer is provided, for example, by a recording medium 1001 such as a CD-ROM or a memory card. When the recording medium 1001 storing the program is set in the drive device 1000, the program is installed from the recording medium 1001 to the auxiliary storage device 1002 via the drive device 1000. However, the installation of the program does not necessarily have to be performed from the recording medium 1001, and it may be downloaded from another computer via a network. The auxiliary storage device 1002 stores the installed program and also stores necessary files, data, etc.

[0055] When there is an instruction to start a program, the memory device 1003 reads and stores the program from the auxiliary storage device 1002. The CPU 1004 realizes the functions related to the device according to the program stored in the memory device 1003. The interface device 1005 is used as an interface for connecting to a network or the like. The display device 1006 displays a GUI (Graphical User Interface) or the like according to the program. The input device 1007 is composed of a keyboard, a mouse, buttons, a touch panel, or the like, and is used to input various operation instructions. The output device 1008 outputs the calculation result.

[0056] (Effects of the Embodiment) With the technology according to the present embodiment described above, in a situation where the connection destination base stations and the wireless communication qualities of each terminal are different, it is possible to perform scheduling to provide the wireless communication quality (such as throughput) required by the terminal.

[0057] (Supplementary Note) Regarding the above embodiment, the following supplementary clauses are further disclosed. (Supplementary Clause 1) A scheduling control device that calculates weights for scheduling for terminals in a wireless system having a plurality of base stations, a memory, at least one processor connected to the memory, including, the processor acquires information on the connection state between each base station and the terminal in the plurality of base stations, for each base station in the plurality of base stations, calculates a weight indicating the distribution ratio of the traffic between the base station and one or more terminals connected to the base station among the terminals, notifies the base station of the weight, the weight is calculated by repeating a process of updating the weight so that the error between the expected wireless communication quality obtained when the weight is given to each terminal and the required wireless communication quality of each terminal is reduced. Scheduling control device. (Additional item 2) The processor calculates the weight so that the mean square error between the required wireless communication quality and the expected wireless communication quality is equal to or less than a threshold value. The scheduling control device according to additional item 1. (Additional item 3) When the mean square error does not become equal to or less than the threshold value by repeated processing a specified number of times, the processor updates the required wireless communication quality and calculates the weight using the updated required wireless communication quality. The scheduling control device according to additional item 2. (Additional item 4) A scheduling control system including the scheduling control device according to any one of additional items 1 to 3 and the plurality of base stations, Each base station among the plurality of base stations executes scheduling for each connected terminal using the weight received from the scheduling control device. Scheduling control system. (Additional item 5) A scheduling control method executed by a computer that calculates a weight for scheduling for a terminal in a wireless system having a plurality of base stations, An information acquisition step of acquiring information on the connection state between each base station among the plurality of base stations and the terminal, For each base station among the plurality of base stations, a weight calculation step of calculating a weight indicating the distribution ratio of the traffic between the base station and one or more terminals connected to the base station among the terminals, A step of notifying the weight to the base station, and In the weight calculation step, the weight is calculated by repeating a process of updating the weight so that the error between the expected wireless communication quality obtained when the weight is given to each terminal and the required wireless communication quality of each terminal becomes small. Scheduling control method. (Additional item 6) A non-transitory storage medium storing a program executable by a computer to execute a weight calculation process for calculating a weight for scheduling a terminal in a wireless system having a plurality of base stations, wherein the weight calculation process acquires information on the connection state between each base station among the plurality of base stations and the terminal, for each base station among the plurality of base stations, calculates a weight indicating the distribution ratio of the traffic between the base station and one or more terminals connected to the base station among the terminals, notifies the base station of the weight, and calculates the weight by repeating a process of updating the weight so that an error between the expected wireless communication quality obtained when the weight is given to each terminal and the required wireless communication quality of each terminal is reduced. Non-transitory storage medium.

[0058] As described above, the present embodiment has been described, but the present invention is not limited to such a specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Signs

[0059] 10A, 10B Base stations 100 Scheduling control device 110 Information acquisition unit 120 Weight calculation unit 130 Control unit 140 Data storage unit 1000 Drive device 1001 Recording medium 1002 Auxiliary storage device 1003 Memory device 1004 CPU 1005 Interface device 1006 Display device 1007 Input device 1008 Output device

Claims

1. A scheduling control device for calculating weights for scheduling a terminal in a wireless system having a plurality of base stations, comprising: an information acquisition unit that acquires information on the connection state between each base station and the terminal among the plurality of base stations; a weight calculation unit that calculates, for each base station among the plurality of base stations, a weight indicating a distribution ratio of traffic between terminals between the base station and one or more terminals connected to the base station; a control unit that notifies the base station of the weight, wherein the weight calculation unit calculates the weight by repeating a process of updating the weight so that an error between an expected wireless communication quality obtained when the weight is given to each terminal and a required wireless communication quality of each terminal is reduced. A scheduling control device.

2. The weight calculation unit calculates the weight so that a mean squared error between the required wireless communication quality and the expected wireless communication quality is equal to or less than a threshold value. The scheduling control device according to claim 1.

3. When the mean squared error does not become equal to or less than the threshold value by a specified number of repetitions of the process, the weight calculation unit updates the required wireless communication quality and calculates the weight using the updated required wireless communication quality. The scheduling control device according to claim 2.

4. A scheduling control system comprising the scheduling control device according to any one of claims 1 to 3 and the plurality of base stations, wherein each base station among the plurality of base stations executes scheduling for each connected terminal using the weight received from the scheduling control device. A scheduling control system.

5. A scheduling control method executed by a computer for calculating weights for scheduling a terminal in a wireless system having a plurality of base stations, comprising: an information acquisition step of acquiring information on the connection state between each base station and the terminal among the plurality of base stations; a weight calculation step of calculating, for each base station among the plurality of base stations, a weight indicating a distribution ratio of traffic between terminals between the base station and one or more terminals connected to the base station; a step of notifying the base station of the weight. In the weight calculation step, the weight is calculated by repeating a process of updating the weight so that an error between an expected wireless communication quality obtained when the weight is given to each terminal and a required wireless communication quality of each terminal is reduced. A scheduling control method.

6. A program for causing a computer to function as each part of the scheduling control device according to any one of claims 1 to 3.

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