Control device, control method, and program

Abstract

This control apparatus is in a wireless communication system provided with a plurality of base stations which autonomously perform sleep control for each carrier. The control apparatus is provided with: an estimation unit for estimating, for the respective carriers, whether or not the carriers are in a sleep state on the basis of a traffic load estimated for the respective carriers; and a calculation unit for calculating a tilt control solution, which is a tilt for each control target carrier, such that power consumption in the plurality of base stations are reduced on the basis of the estimation results of the estimation unit.

Description

Technical Field

[0001] The present invention relates to a technique for controlling a plurality of base stations in a wireless communication system.

Background Art

[0002] A base station in a wireless communication system (which may also be called a mobile communication system) generally includes a plurality of antennas and covers an area using a certain frequency band (carrier) for each antenna. Generally, each area is covered by a plurality of carriers, and thereby a large amount of traffic can be accommodated.

[0003] In recent years, efforts to suppress energy consumption have been made in various fields. In a wireless communication system, for the purpose of power saving of base stations, a sleep control technique has been studied to reduce the power consumption by putting some base stations into carrier outage (sleep) in time zones / areas with low traffic demand (Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the prior art disclosed in Non-Patent Document 1 has the drawback of having a low power consumption reduction effect.

[0006] This invention has been made in view of the above points, and aims to provide a technology for achieving a high power consumption reduction effect in power saving of base stations. [Means for solving the problem]

[0007] According to the disclosed technology, a control device in a wireless communication system comprising multiple base stations that autonomously perform sleep control for each carrier, An estimation unit that estimates whether each carrier is in a sleep state or not based on the traffic load estimated for each carrier, A calculation unit calculates a tilt control solution, which is the tilt for each controlled carrier, based on the estimation results from the estimation unit, so as to reduce the power consumption at the multiple base stations. A control device is provided that includes the following. [Effects of the Invention]

[0008] According to the disclosed technology, a technology is provided that enables significant power consumption reduction in base stations. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram showing the system configuration in an embodiment of the present invention. [Figure 2] This is a diagram illustrating the configuration of a base station control unit. [Figure 3] This is a flowchart illustrating the operation of the base station control device in Example 1. [Figure 4] This is a flowchart illustrating the operation of the base station control device in Example 3. [Figure 5] This figure shows an example of the device's hardware configuration. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the present invention (this embodiment) 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 embodiments described below.

[0011] This section describes the "antennas and carriers" used by the base station in this embodiment. The base station consists of multiple antennas, each responsible for communication coverage in a specific direction. The antennas consist of multiple carriers, and each carrier in a given antenna is responsible for communication coverage in a specific frequency band in the same direction. At this time, a tilt (downward angle) is set for each carrier, and different angles result in different coverage areas.

[0012] Furthermore, in this embodiment, it is assumed that carriers are classified into two types: "carriers for comprehensively covering each area" (coverage carriers) and "carriers prepared in addition to coverage carriers for areas with high traffic demand" (capacity carriers). However, the technology according to the present invention is also applicable even when carriers are not classified into these two types.

[0013] The reference names corresponding to the reference numbers ([2], etc.) referenced in the following explanation are listed together at the end of the specification. Reference [1] is the aforementioned Non-Patent Document 1.

[0014] In the following, we will first explain the challenges related to power saving and the technology of this embodiment, and then we will explain the technology of this embodiment in detail. In the following explanation, the contents disclosed in the references are publicly known, but explanations other than those disclosed in the references (such as the challenges related to the contents disclosed in the references) are not publicly known.

[0015] (Regarding power saving) As described above, in a wireless communication system, for the purpose of power saving in a base station, a sleep control technique has been studied (Non-Patent Document 1) in which carriers are put into outage (sleep) in some base stations in time zones / areas with low traffic demand to reduce power consumption.

[0016] Sleep control is generally performed autonomously for each base station according to the traffic load or the like (Reference [2]). In the technique disclosed in Reference [2], a threshold value is set for the traffic load, and when the traffic load falls below the threshold value, sleep is implemented. The threshold value for determining whether to perform this sleep is called a sleep threshold value.

[0017] The range of carriers to be put into sleep can be, in descending order of magnitude, sleep for the entire base station including all carriers, sleep for each carrier, sleep for each resource block (RB), etc. Note that an RB is what divides a carrier on the frequency axis and the time axis, and for communication, it is allocated to a terminal in units of 2 RBs. Compared with tilt control, sleep control enables control at short time intervals, and switching within 1 second for each control is being considered.

[0018] When the traffic load of a base station increases, there is a risk that the communication quality of the connected terminals deteriorates. On the other hand, in a situation where the traffic load of each base station is evenly distributed, there is a possibility that the traffic load of no base station falls below the sleep threshold value and sleep is not executed. In such a situation, it is difficult to reduce the power consumption of the base station.

[0019] On the other hand, an approach can be considered in which the tilt of the antenna of a base station is controlled for the purpose of reducing power consumption to change the coverage area of each carrier. By changing the coverage area, the number of terminals accommodated by each carrier, that is, the traffic load, can be changed. By appropriately adjusting the traffic load, the traffic load of some carriers can be reduced and put into sleep within a range where the traffic load of all carriers does not exceed the capacity of the carriers.

[0020] Tilt control can be changed by the central controller in units of several minutes to several hours. On the other hand, for sleep control, in order to realize sleep control in a short time as described above, autonomous decentralized control for each base station is preferred rather than batch control by the central controller.

[0021] (Regarding the problem) Next, the prior art and its problems will be described in detail.

[0022] (1) Prior art and its problem 1 In the technology disclosed in Reference [1], by changing parameters such as the tilt and transmission power of the base station, while putting some base stations into sleep, the deterioration of the communication quality of the terminals near the base stations is suppressed. This method assumes that the central controller controls the sleep and tilt control of the base stations in a batch.

[0023] Therefore, compared with the case where the base station performs sleep control autonomously, the reflection of the control is slow, and fine-grained control cannot be performed. As a result, compared with autonomous sleep control, the control frequency is low, and there is a possibility that the opportunity for sleep is missed, resulting in an increase in power consumption.

[0024] (2) Prior art and its problem 2 Also, in the technology disclosed in Reference [1], the roles of each carrier such as the coverage carrier and the capacity carrier are not distinguished, and the tilt and transmission power of all carriers are changed. Therefore, depending on the estimation error of the communication quality and the accuracy of the control solution, there may be an area (coverage hole) that is not covered by any carrier in some areas.

[0025] (3) Prior art and its problem 3 Also, in the technology disclosed in Reference [1], after the base station to be shut down is determined by some method, the parameters for improving the communication quality of the terminal are calculated. However, the communication quality of the terminal depends greatly on the base station to be shut down. Therefore, depending on the selection method of the base station to be shut down, it may not be possible to ensure the communication quality.

[0026] (Summary of the technology related to the embodiment) The base station control device 100, described later, solves the problems 1 to 3 mentioned above. First, let's explain the overview of the base station control device 100.

[0027] In the wireless communication system controlled by the base station control device 100, it is assumed that each carrier at each base station autonomously shuts down its transmission in accordance with the traffic load. In this embodiment, as an example, it is assumed that each carrier goes to sleep based on the sleep model disclosed in reference [2].

[0028] In the model in reference [2], for example, if the number of users accommodated by the base station falls below a pre-calculated sleep threshold, the base station enters a sleep state, and returns to an operational state when it exceeds that threshold again.

[0029] In this embodiment, the traffic load value is used as the sleep threshold. In this embodiment, for example, when the traffic load of a carrier falls below the sleep threshold, that carrier enters a sleep state (transmission stopped), and when the traffic load rises above the sleep threshold, that carrier enters an operational state. Note that the sleep model using the sleep threshold is just one example.

[0030] The base station control device 100 receives information as input, which will be explained later in the input reception unit 110, and transmits a combination of tilts for all carriers to be controlled (called the tilt control solution) as output. This changes the tilt for each carrier to be controlled.

[0031] In this embodiment, to prevent coverage holes from occurring due to tilt changes, the tilt of carriers other than redundant carriers is not controlled. In other words, only the tilt of redundant carriers is controlled. The method for selecting redundant carriers will be described later.

[0032] However, for traffic load and other factors, calculations are performed for all carriers, including those other than redundant carriers, and control is performed based on these calculations.

[0033] In calculating the tilt control solution, the objective function described later is used to find a solution that maximizes the reduction in base station power consumption while guaranteeing communication quality in each area.

[0034] (Technical features (key points) related to the embodiment) The key features (points) of the technology according to this embodiment are as follows. Note that the points described below are the key points of the technology in this embodiment, and it is not necessary for the invention to include all of them.

[0035] <Point 1> To accommodate situations where tilt control and sleep control operate independently, tilt control is performed based on sleep state estimation using a sleep model.

[0036] <Point 2> To cover all areas, the minimum necessary carriers are selected in advance, and tilt control is applied to the remaining carriers (redundant carriers). All carriers other than the coverage carrier may be selected as redundant carriers.

[0037] <Point 3> In the objective function used for optimizing tilt control, in addition to the "power reduction effect for each carrier," a penalty term is used that includes "the number of carriers whose traffic load exceeds a threshold (quality degradation threshold) that determines whether the traffic load affects the degradation of communication quality."

[0038] (Effects of the technology according to the embodiment) The technology according to this embodiment, having the points described above, produces the following effects.

[0039] <Effect 1> Point 1 enables autonomous sleep control at the base station level, achieving fine-grained sleep control and effectively reducing power consumption. This solves Problem 1.

[0040] <Effect 2> Point 2 ensures coverage of all areas and guarantees that no coverage holes occur regardless of the tilt control results. This solves problem 2.

[0041] <Effect 3> Points 2 and 3 enable control to be implemented so that the traffic load on all carriers does not become excessive. This allows for reduced power consumption while guaranteeing the communication quality of terminals. This solves problem 3.

[0042] (Overall system configuration) Figure 1 shows an example of the overall configuration of the wireless communication system in this embodiment. As shown in Figure 1, the system according to this embodiment has a configuration in which a plurality of base stations 10 and a base station control device 100 are connected to a network 200. The network 200 is, for example, a network including a mobile core network. Communication terminals exist under each base station, and each communication terminal communicates with the base station wirelessly. Each base station autonomously performs carrier-specific sleep control based on a sleep threshold.

[0043] The configuration and operation of the base station control device 100 according to this embodiment will be described in detail below.

[0044] (Example of the configuration of the base station control device 100) Figure 2 shows a configuration diagram of the base station control device 100 in this embodiment. As shown in Figure 2, the base station control device 100 includes an input receiving unit 110, a data processing unit 120, and a base station control unit 130.

[0045] Furthermore, as shown in Figure 2, the data processing unit 120 includes a traffic demand calculation unit 121, a redundant carrier selection unit 122, a tilt calculation unit 123, a coverage area estimation unit 124, a traffic load estimation unit 125, a sleep state estimation unit 126, and a power reduction effect estimation unit 127. The base station control unit 130 includes a receiving unit 131 and a transmitting unit 132.

[0046] The base station control device 100 may be a single physical device or a system consisting of multiple physical devices. For example, the "input receiving unit 110 + data processing unit 120" may consist of one device, and the base station control unit 130 may consist of one device. The "input receiving unit 110 + data processing unit 120" or the "data processing unit 120" may also be referred to as the control device.

[0047] Furthermore, the "redundant carrier selection unit 122 + tilt calculation unit 123" may be referred to as the "calculation unit." Also, the "coverage area estimation unit 124 + traffic load estimation unit 125 + sleep state estimation unit 126 + power reduction effect estimation unit 127" may be referred to as the "estimation unit." The functions of each unit are as follows.

[0048] <Base station control unit 130> The receiving unit 131 and transmitting unit 132 of the base station control unit 130 are each capable of communicating with the base station. The receiving unit 131 receives information from the base station, and the transmitting unit 132 transmits information to the base station.

[0049] <Input reception unit 110> The input receiving unit 110 receives "information about the base station / carrier" and "observed values ​​of traffic demand" from the base station control unit 130.

[0050] "Information about base stations / carriers" includes, for example, the following:

[0051] • The location (latitude, longitude), height (m), and azimuth (°) of all antennas installed at the base station. • Beam width (°) of each carrier's beam in the vertical and horizontal directions. • The currently set tilt (°) for each carrier and the set of configurable tilts. • Sleep / operation status of each carrier • Power consumption per hour for each carrier, and power consumption (kWh) during sleep mode. "Observed traffic demand data" includes information such as the following:

[0052] • Traffic volume (bps) for each area at different times of the day • Number of active users (people) per time period in each area Here, the area is defined as the area covered by a single carrier or as a 100m x 100m section. The time unit is defined as one hour.

[0053] <Traffic Demand Calculation Unit 121> The traffic demand calculation unit 121 calculates the current estimated value and future forecast value of traffic demand for each carrier based on observed values ​​of traffic demand (traffic volume, number of active users) from the past to the present, which are periodically obtained from the input reception unit 110.

[0054] The traffic demand calculation unit 121 estimates / forecasts traffic demand in the above calculation, taking into account that the observed values ​​contain observation errors.

[0055] The method for calculating the estimated values ​​is not limited to a specific method, but for example, exponential moving averages and state-space models (Kalman filter models) can be used. Similarly, the method for calculating the predicted values ​​is not limited to a specific method, but for example, prediction methods using SARIMA (reference [4]) and prediction methods using LSTM (reference [5]) can be used.

[0056] <Redundant carrier selection unit 122> The redundant carrier selection unit 122 selects a redundant carrier based on information obtained from the input reception unit 110 and the coverage area estimation unit 124.

[0057] Specifically, the redundant carrier selection unit 122 transmits carrier downtime / operational information and tilt information currently set for the operational carrier to the coverage area estimation unit 124, and obtains coverage area information for each carrier from the coverage area estimation unit 124. From the obtained information, the redundant carrier selection unit 122 selects as redundant carriers carriers that will not create coverage holes even if their coverage areas are excluded.

[0058] The redundant carrier selection unit 122 may, for example, select redundant carriers by following the procedures S100 and S200.

[0059] S100: Prioritize capacity carriers and select redundant carriers one by one, starting with those with smaller coverage areas.

[0060] The S200:S100 selection process is repeated until "a coverage hole occurs due to the exclusion of the redundant carrier's coverage area."

[0061] By limiting the tilt control to only the redundant carriers selected by the redundant carrier selection unit 122, it is possible to prevent the occurrence of coverage holes even if an inappropriate tilt control solution is selected.

[0062] <Overview of the Tilt Calculation Unit 123> The tilt calculation unit 123 first calculates an initial solution for the tilt control of redundant carriers based on information obtained from the input reception unit 110 and the redundant carrier selection unit 122. Then, the tilt calculation unit 123 calculates feedback for this tilt control solution based on information obtained from the traffic load estimation unit 125 and the power reduction effect estimation unit 127. Based on this feedback, the tilt calculation unit 123 updates the tilt control solution.

[0063] <Algorithm of Tilt Calculation Unit 123> The tilt calculation unit 123 can use, for example, an algorithm based on the algorithm disclosed in reference [6] as the algorithm used for tilt calculation. However, using the algorithm disclosed in reference [6] is merely one example, and other tilt calculation algorithms may be used. Furthermore, even when using the algorithm based on reference [6], the objective function used in this embodiment is different from the objective function disclosed in reference [6].

[0064] The tilt calculation unit 123 finds a tilt control solution that optimizes a pre-set objective function for the redundant carriers under control. Specifically, it first randomly generates an initial solution as the tilt control solution. Then, it searches for the optimal solution by updating the solution using feedback of the objective function value.

[0065] <Objective function of tilt calculation unit 123> Next, we will explain how the objective function value is calculated in the tilt calculation algorithm executed by the tilt calculation unit 123.

[0066] The tilt calculation unit 123 transmits the tilt control solution to the coverage area estimation unit 124, and via the coverage area estimation unit 124, it obtains values ​​for the traffic load and power reduction effect for each carrier (including carriers other than redundant carriers) from the traffic load estimation unit 125 and the power reduction effect estimation unit 127, respectively. Using these values, the objective function value is defined as follows.

[0067] Specifically, for example, the objective function value is defined as "[number of carriers estimated to be in sleep state] - a × [number of carriers where the traffic load exceeds the threshold]," where a is a predetermined coefficient.

[0068] In the example above, the traffic load estimation unit 125 obtains the traffic load for each carrier, and the power reduction effect estimation unit 127 obtains the "number of carriers estimated to be in sleep state".

[0069] When using the above objective function value, the tilt calculation unit 123 finds a tilt control solution that maximizes the objective function value. Furthermore, regarding coefficient a, in the system according to this embodiment, a large value is set for a in order to guarantee communication quality, so that the number of carriers where the traffic load exceeds the threshold is reduced.

[0070] By setting the objective function as described above, it is possible to design the objective function as explained in "Point 3" above.

[0071] Furthermore, by using information from the power reduction effect estimation unit 127 to calculate the objective function value, tilt control can be performed without using actual sleep control information. This makes it possible to "handle situations where tilt control and sleep control operate independently," as explained in "Point 1" above.

[0072] The tilt calculation unit 123 uses the objective function value calculated as described above as feedback to update the tilt control solution to approach the optimal solution. After the control solution converges or a sufficient number of updates have been performed, the tilt calculation unit 123 transmits the optimal control solution obtained so far to the base station control unit 130, which then changes the tilt of each carrier.

[0073] <Coverage area estimation unit 124> The coverage area estimation unit 124 estimates the coverage area of ​​each carrier based on the carrier's shutdown / operation information and the tilt set for the operational carrier. The coverage area estimation unit 124 assumes that a shutdown carrier does not affect the coverage area of ​​other carriers and estimates only the coverage area of ​​the operational carrier.

[0074] Any existing method may be used for estimating the coverage area. For example, the geometric coverage area estimation method disclosed in reference [6] or the high-precision estimation method that takes propagation loss and radio interference into account disclosed in reference [3] can be used.

[0075] The coverage area estimation unit 124 can change which estimation method to use depending on the requirements for computation time and estimation accuracy. For example, if sufficient computation time can be secured, the estimation method disclosed in reference [3] is used to estimate the coverage area; otherwise, the estimation method disclosed in reference [6] is used.

[0076] Furthermore, when using the geometric coverage area estimation method disclosed in reference [6], the coverage area may be defined as "an area where sufficient received signal strength (RSRP) can be obtained" from the standpoint of radio wave quality.

[0077] Furthermore, when using the highly accurate estimation method that takes into account propagation loss and radio interference disclosed in reference [3], the coverage area may be defined as "an area where sufficient throughput can be ensured" from the standpoint of communication quality.

[0078] <Traffic load estimation unit 125> The traffic load estimation unit 125 calculates the amount of traffic each carrier can accommodate and the number of active users based on the coverage area of ​​each carrier obtained from the coverage area estimation unit 124 and the traffic demand for each area obtained from the traffic demand calculation unit 121.

[0079] The traffic load estimation unit 125 then estimates the traffic load for each carrier based on these values, the amount of traffic each carrier can accommodate, and the number of active users.

[0080] Furthermore, traffic load estimation may be performed using either the traffic volume or the number of active users, or it may be performed using both the traffic volume and the number of active users.

[0081] For example, when using the sleep model disclosed in reference [2] in the sleep state estimation unit 126, it is preferable to use the number of active users to calculate the traffic load. Also, the traffic load used in the tilt calculation unit 123 may be different from the traffic load used in the sleep state estimation unit 126.

[0082] The traffic load estimation unit 125 calculates the following values ​​as the traffic load: for example, (1) or (2).

[0083] (1) [Amount of traffic to be accommodated] / [Amount of traffic that can be accommodated] (2) [Number of active users to accommodate] / [Number of active users that can be accommodated] Alternatively, in addition to the values ​​mentioned above, the RB utilization rate may be estimated and used as the traffic load.

[0084] Furthermore, if the traffic demand provided to the traffic load estimation unit 125 is time-series data that changes over time, the traffic load estimation unit 125 will estimate the time-series traffic load.

[0085] <Sleep state estimation unit 126> The sleep state estimation unit 126 estimates whether each carrier will be in a sleep or operational state when the tilt control solution is applied, based on the estimated traffic load obtained from the traffic load estimation unit 125.

[0086] As described above, in the wireless communication system according to this embodiment, each carrier autonomously goes to sleep based on a sleep model. This sleep model is, for example, the sleep threshold-based sleep model disclosed in reference [2].

[0087] The sleep state estimation unit 126 uses this sleep model, for example, to estimate the sleep / operational state of each carrier. Furthermore, if the estimated traffic load is time-series data, the sleep state estimation unit 126 also estimates the sleep state as a time series, including the ON / OFF transition.

[0088] The sleep state estimation unit 126 estimates the sleep state of each carrier, and the tilt calculation unit 123 performs tilt calculations based on the estimation results, enabling tilt control without using actual sleep control information. This makes it possible to "handle situations where tilt control and sleep control operate independently," as explained in "Point 1" above.

[0089] <Power reduction effect estimation unit 127> The power reduction effect estimation unit 127 estimates the power reduction effect due to sleep based on the estimated sleep status of each carrier obtained from the sleep state estimation unit 126 and the information on the power consumption of each carrier obtained from the input reception unit 110. The index calculated by the power reduction effect estimation unit 127 can be any index that represents the power reduction effect, but for example, one or more of the values ​​(1) to (3) below can be used.

[0090] (1) Estimated number of carriers in sleep state (2) Duration of sleep state (if the sleep state is a time-series data that changes over time) (3) Amount of power saved by sleep mode Note that the duration of the sleep state in (2) above is, for example, the sum of the sleep state durations for all carriers.

[0091] Furthermore, regarding (3) above, if the sleep state is time-series data, it can be calculated from the power consumption per hour and the duration of the sleep state. For example, "power consumption per hour × duration of sleep state" can be calculated for each carrier, and the sum of these for all carriers can be used as "power saved by sleep."

[0092] The power reduction effect value calculated by the power reduction effect estimation unit 127 is a value that indicates the performance of the tilt control solution obtained by the tilt calculation unit 123. The tilt calculation unit 123 receives this value as feedback and updates the tilt control solution based on this feedback to find a solution that is closer to the optimal solution.

[0093] Below, examples of the operation of the base station control device 100 having the above configuration will be described as Examples 1 to 3.

[0094] (Example 1: Base station control based on current traffic demand) First, Example 1 will be described. In Example 1, the tilt calculation unit 123 calculates the optimal tilt control solution according to the current traffic demand which is observed periodically, and instructs the base station control unit 130 to perform control based on the calculation result. In Example 1, the control period is set to several minutes to about one hour, and periodic online control is performed. The operation flow of the base station control device 100 will be described below according to the procedure in the flowchart of Figure 3.

[0095] In S1, the input reception unit 110 periodically acquires information from the base station control unit 130.

[0096] In S2, the traffic demand calculation unit 121 estimates the current traffic demand from the information acquired in S1. In S3, the redundant carrier selection unit 122 selects redundant carriers based on the information acquired in S1. In S4, the tilt calculation unit 123 calculates an initial solution for the tilt control solution of the redundant carriers based on the traffic demand and the current sleep state of each carrier.

[0097] In S5, the coverage area estimation unit 126 estimates the coverage area of ​​each carrier, taking into account the tilt control solution obtained in S4 or S9.

[0098] In S6, the traffic load estimation unit 125 estimates the traffic load of each carrier based on the estimated coverage area. In S7, the sleep state estimation unit 126 estimates the sleep state of each carrier based on the traffic load. Furthermore, in S8, the power reduction effect estimation unit 127 estimates the power reduction effect based on the estimated sleep state.

[0099] In S9, the tilt calculation unit 123 updates the tilt control solution based on the traffic load information obtained from the traffic load estimation unit 125 and the power reduction effect obtained from the power reduction effect estimation unit 127 (e.g., the number of carriers estimated to be in sleep mode).

[0100] In S10, the tilt calculation unit 123 terminates the calculation when the calculated tilt control solution converges or is updated a sufficient number of times, and in S11, transmits the calculation result (optimal control solution) to the base station control unit 130. If the calculation is not terminated, the process proceeds to S5.

[0101] (Example 2: Base station control based on traffic demand forecasting) Next, we will describe Example 2. In Example 2, future forecast values ​​of traffic demand are used to pre-prepare tilt control patterns for each carrier for each time period. Then, when the current time falls within the corresponding time period, the base station control unit 130 is instructed to perform control. In other words, control is instructed using a tilt control solution corresponding to the time period to which the current time belongs. In Example 2, the control cycle is set to several hours, and offline control is performed at each cycle.

[0102] Unlike Example 1, Example 2 ensures sufficient computation time in the coverage area estimation unit 124, enabling highly accurate control that takes into account radio interference and other factors.

[0103] The operation flow in Example 2 is basically the same as in Example 1 (Figure 3), but there are some differences. Here, we will mainly explain the differences from Example 1 (Figure 3).

[0104] In Example 2, in S2, the traffic demand calculation unit 121 calculates predicted values ​​for the traffic demand of each carrier for each time period based on the traffic demand observed periodically.

[0105] The tilt calculation unit 123 uses the demand for each time period to calculate the tilt control solution for each time period using the same procedure (S3 to S10) as in Example 1, and stores this control information.

[0106] The tilt calculation unit 123 then transmits the held control information to the base station control unit 130 according to the time period to which the current time belongs, and instructs the control (S11).

[0107] (Example 3: Base station control combining Examples 1 and 2) Next, Example 3 will be described. In Example 3, offline control based on traffic demand forecasting is performed as in Example 2, but in the event of sudden traffic demand fluctuations or base station failures, online control similar to that in Example 1 is used to address them. This makes it possible to achieve both high-precision control that takes into account radio interference during normal operation and the ability to deal with sudden demand fluctuations. The operation flow in Example 3 will be explained with reference to the flowchart in Figure 4.

[0108] In S21, the input reception unit 110 acquires observation information at intervals of several minutes, which is shorter than the control cycle of several hours in Example 2. In S22, the traffic demand calculation unit 121 estimates the current traffic demand of each carrier based on this traffic demand. In S23, the traffic load estimation unit 125 estimates the traffic load of each carrier based on the estimated traffic demand.

[0109] In S24, the data processing unit 120 determines whether there are any carriers whose traffic load, estimated by the traffic load estimation unit 125, exceeds a threshold, and proceeds to S25 if there are. In S25, the tilt calculation unit 123 calculates new control content using the same procedure as in Embodiment 1, notifies the base station control unit 130 of the calculation result, and instructs the control to proceed.

[0110] If no carriers have a traffic load estimated by the traffic load estimation unit 125 that exceeds the threshold, in S26, the tilt calculation unit 123 notifies the base station control unit 130 of the control content for each time period using the same processing procedure as in Embodiment 2, and instructs the control to be performed. While performing the same processing procedure as in Embodiment 2, S21 to S24 are repeatedly executed, and if there are carriers whose traffic load exceeds the threshold, control based on Embodiment 1 is executed as needed.

[0111] (Example hardware configuration) The base station control device (or control device) in this embodiment can be implemented, for example, by having a computer execute a program that describes the processing content described in this embodiment. This "computer" may be a physical machine or a virtual machine on the cloud. When a virtual machine is used, the "hardware" described here is virtual hardware.

[0112] The above program can be recorded on a computer-readable storage medium (such as portable memory), saved, and distributed. It can also be provided via a network, such as the internet or email.

[0113] Figure 5 shows an example of the hardware configuration of the computer described above. The computer in Figure 5 has 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., all of which are interconnected by a bus BS.

[0114] The program that enables processing on the computer is provided, for example, on a recording medium 1001 such as a CD-ROM or memory card. When the recording medium 1001 containing 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 program does not necessarily have to be installed from the recording medium 1001; it may also be downloaded from another computer via a network. The auxiliary storage device 1002 stores the installed program as well as necessary files and data.

[0115] The memory device 1003 reads and stores a program from the auxiliary storage device 1002 when a program startup command is received. The CPU 1004 implements the functions related to the wireless base station control device 100 (control 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. The display device 1006 displays a GUI (Graphical User Interface) etc., generated by a program. The input device 1007 consists of a keyboard and mouse, buttons, or a touch panel etc., and is used to input various operation commands. The output device 1008 outputs the calculation results.

[0116] (Note) This specification includes control devices, control methods, and programs as described in at least the following sections. (Additional note 1) A control device in a wireless communication system comprising multiple base stations that autonomously perform sleep control for each carrier, An estimation unit that estimates whether each carrier is in a sleep state or not based on the traffic load estimated for each carrier, A calculation unit calculates a tilt control solution, which is the tilt for each controlled carrier, based on the estimation results from the estimation unit, so as to reduce the power consumption at the multiple base stations. A control device equipped with the following features. (Additional note 2) The estimation unit estimates the coverage area of ​​each operating carrier, The calculation unit selects a redundant carrier as the carrier to be controlled, which is a carrier that does not create coverage holes even when the coverage area is excluded. The control device described in Appendix 1. (Additional note 3) The calculation unit calculates the tilt control solution in such a way that it maximizes an objective function value that, in addition to a value indicating the power reduction effect, has a penalty term indicating quality degradation. The control device described in Appendix 1 or 2. (Additional note 4) The value indicating the aforementioned quality degradation is the number of carriers whose traffic load exceeds a threshold. The control device described in Appendix 3. (Additional note 5) The calculation unit pre-calculates tilt control solutions for each time period based on the estimation results for each time period by the estimation unit, and instructs the control unit to perform control using the tilt control solution corresponding to the time period to which the current time belongs. A control device as described in any one of the appendices 1 through 4. (Additional note 6) A control method performed by a control device in a wireless communication system comprising multiple base stations that autonomously perform sleep control for each carrier, An estimation step to estimate whether each carrier is in a sleep state or not, based on the traffic load estimated for each carrier, A calculation step to calculate a tilt control solution, which is the tilt for each carrier to be controlled, based on the estimation results from the estimation step, so as to reduce the power consumption at the multiple base stations. A control method comprising the following features. (Additional note 7) A program for causing a computer to function as a component of the control device described in any one of the appendices 1 through 5.

[0117] Although this embodiment has been described above, the present invention is not limited to this specific embodiment, and various modifications and changes are possible within the scope of the gist of the invention as described in the claims.

[0118] (References) [1] Y. Gao, Y. Li, H. Yu, X. Wang and S. Gao, "Energy joint optimization of electric antenna tiltand efficient transmit power in 3GPP LTE-Advanced: A system level result," 2013 IEEE 9th International Colloquium on Signal Processing and its Applications, 2013, pp. 135-139, doi:10.1109 / CSPA.2013.6530029. [2] JH Noh, B. Lee and SJ Oh, "User-Number Threshold-Based Base Station On / Off Control forMaximizing Coverage Probability," in IEEE Transactions on Vehicular Technology, vol. 71, no. 3, pp.3214-3228, March 2022, doi: 10.1109 / TVT.2022.3141592. [3] N. Dandanov, H. Al-Shatri, A. Klein, and V. Poulkov, "Dynamic Self-Optimization of the AntennaTilt for Best Trade-off Between Coverage and Capacity in Mobile Networks," Wirel. Pers. Commun.,vol. 92, no. 1, pp. 251-278, 2017. [4] Luo, X., Niu, L. & Zhang, S. An Algorithm for Traffic Flow Prediction Based on Improved SARIMAand GA. KSCE J Civ Eng 22, 2018, pp. 4107-4115. [5] HD Trinh, L. Giupponi and P. Dini, "Mobile Traffic Prediction from Raw Data Using LSTMNetworks," 2018 IEEE 29th Annual International Symposium on Personal, Indoor and Mobile RadioCommunications (PIMRC), 2018, pp. 1827-1832, doi: 10.1109 / PIMRC.2018.8581000. [6] Masanao Iwamoto, Akihito Suzuki, Masahiro Kobayashi, "Antenna Tilt Control Method by Particle Swarm Optimization for Early Recovery of Damaged Areas," IEICE Technical Report, vol. 121, no. 324, IN2021-24, pp. 1-6, January 2022. [Explanation of Symbols]

[0119] 100 Base station control devices 110 Input reception section 120 Data Processing Unit 121 Traffic Demand Calculation Department 122 Redundancy Carrier Selection Section 123 Tilt Calculation Unit 124 Coverage Area Estimation Unit 125 Traffic Load Estimation Unit 126 Sleep state estimation unit 127 Power Reduction Effect Estimation Unit 130 Base Station Control Unit 131 Receiving Unit 132 Transmitter 1000 drive unit 1001 Recording media 1002 Auxiliary storage device 1003 Memory device 1004 CPU 1005 Interface device 1006 Display device 1007 Input device 1008 Output device

Claims

1. A control device in a wireless communication system comprising multiple base stations that autonomously perform sleep control for each carrier, An estimation unit that estimates whether each carrier is in a sleep state or not based on the traffic load estimated for each carrier, A calculation unit calculates a tilt control solution, which is the tilt for each controlled carrier, based on the estimation results from the estimation unit, so as to reduce the power consumption at the multiple base stations. A control device equipped with the following features.

2. The estimation unit estimates the coverage area of ​​each operating carrier, The calculation unit selects a redundant carrier as the carrier to be controlled, which is a carrier that does not create coverage holes even when the coverage area is excluded. The control device according to claim 1.

3. The calculation unit calculates the tilt control solution in such a way that it maximizes an objective function value that, in addition to a value indicating the power reduction effect, has a penalty term indicating quality degradation. The control device according to claim 1.

4. The value indicating the aforementioned quality degradation is the number of carriers whose traffic load exceeds a threshold. The control device according to claim 3.

5. The calculation unit pre-calculates tilt control solutions for each time period based on the estimation results for each time period by the estimation unit, and instructs the control unit to perform control using the tilt control solution corresponding to the time period to which the current time belongs. The control device according to any one of claims 1 to 4.

6. A control method performed by a control device in a wireless communication system comprising multiple base stations that autonomously perform sleep control for each carrier, An estimation step to estimate whether each carrier is in a sleep state or not, based on the traffic load estimated for each carrier, A calculation step to calculate a tilt control solution, which is the tilt for each carrier to be controlled, based on the estimation results from the estimation step, so as to reduce the power consumption at the multiple base stations. A control method comprising the following features.

7. A program for causing a computer to function as a component of the control device described in any one of claims 1 to 4.

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