WO2021210137A1 - Wireless communication system, network control device, network control method, and program - Google Patents

Abstract

This wireless communication system includes a network control device, and a plurality of access points. The access points perform wireless communication with a terminal station by means of a directional beam. The access points estimate the direction of the terminal station on the basis of information relating to the beam, and estimate the distance to the terminal station on the basis of the round-trip transmission time to and from the terminal station. The network control device determines the necessity for handover on the basis of information relating to the position of the terminal station, estimated using the direction and distance information estimated by the access points, and information relating to the position of the access points. If it is determined that handover is necessary, the network control device notifies the terminal station of information to be used to connect to the next connection destination access point, by way of the access point to which the terminal station is currently connected.

Description

Wireless communication system, network control device, network control method and program

The present invention relates to a wireless communication system, a network control device, a network control method and a program.

In recent years, millimeter-wave band wireless communication technology capable of high-speed communication has attracted attention. Examples of this technology include wireless LAN (IEEE 802.11ad, 802.11ay) / wireless PAN (IEEE 802.15.3e) that employs a millimeter wave band, and a fifth-generation mobile communication system. International standards have been established.

The frequency of the microwave band is 6 GHz (gigahertz) or less, and the frequency of the millimeter wave band is several tens of GHz or more. Compared to the microwave band, the millimeter wave band is characterized by a large attenuation of radio waves in free space propagation. In order to compensate for such propagation attenuation, a radio communication system using the above standardized technology incorporates a technique for improving radio quality by beamforming. Beamforming is the formation of a directional beam using a plurality of antenna elements.

In a general wireless communication system, a wireless area is often configured in a plane by installing a large number of access points (hereinafter referred to as AP). Handover control is performed to maintain wireless communication between the AP and the mobile terminal station (hereinafter referred to as STA). The handover control transfers the STA from the connected AP to another AP based on the monitoring result by a predetermined radio quality monitoring method (for example, whether the received power is below a certain level) performed by the AP (or STA). It is a technology to reconnect. FIG. 13 is a diagram showing an example of handover control.

The problems associated with the handover control shown in FIG. 13 are described below. In FIG. 13, the STA is connected to AP # 1. Arrow A91 is a path moving away from AP # 1 toward AP # 2. As the STA moves along the path of arrow A91, the radio quality (for example, received power) between the connected AP # 1 observed in the STA and its own station deteriorates. On the other hand, the radio quality between AP # 2 and its own station observed in STA will increase. In the example of FIG. 13, it is desirable that the handover control is started when the STA is near the desired boundary line A92 of the handover control. However, the STA generally maintains a wireless connection with AP # 1 to which the station is connected until the observed radio quality drops to a certain level. If the STA continues to connect to AP # 1 whose wireless quality is deteriorated even though it has passed the desired boundary line A92, the handover control to AP # 2 is not started, and the wireless communication throughput deteriorates. There is (first problem).

Also, when the radio quality with AP # 1 observed in STA falls below a certain level, the connection with AP # 1 is disconnected. Due to this disconnection, the STA cannot send and receive data wirelessly. Therefore, the STA searches for the presence or absence of nearby APs in order to transmit and receive data wirelessly again. However, since the STA does not know the APs existing around its own station, it usually searches for all radio channel candidates. The search is to search for the optimum AP (for example, the beacon with the maximum received power in the STA) from the APs found in the reception after receiving for a certain period of time in each wireless channel while the STA switches the wireless channel. It is an operation such as selecting the transmitted AP). In this way, it takes a certain amount of time for the STA to search for the optimum AP from all the candidates for the wireless channel. While the search is being executed, the STA has a problem that it cannot send and receive data wirelessly (second problem).

As a technique for solving the first problem in handover control, there are the following conventional techniques for starting handover control at an appropriate timing. The appropriate timing corresponds to the time when the STA passes the desired boundary line A92 of the handover control in FIG.

FIG. 14 is a diagram showing an outline of the first prior art. The difference between FIG. 14 and FIG. 13 is the radio quality (for example, reception) between AP # 1 and the STA connected to AP # 1 by a higher-level network controller (hereinafter referred to as NWC). The point is to keep monitoring (power, etc.). AP # 1 transmits a radio quality report with the STA to the NWC (step S9101). If the NWC determines that the radio quality with the STA in AP # 1 is below a certain level, it presumes that the STA has crossed the desired boundary line A92 between AP # 1 and AP # 2. Based on this estimation, the NWC transmits a disconnection instruction between AP # 1 and STA (step S9102). The NWC causes the STA to disconnect from AP # 1 by the connection disconnection instruction transmitted via AP # 1, and then reconnects to AP # 2.

Since the above method uses the radio quality observation result for the determination of handover control, an error in position estimation is likely to occur due to fading due to the movement of the STA and thermal noise of the receiver. This causes a problem that the accuracy of the timing for starting the handover control deteriorates. Further, since the NWC does not know the position of the STA from the radio quality between AP # 1 and the STA, the AP to which the STA is reconnected and the radio channel of the AP are unknown. Therefore, the search for a certain period of time is still required until the STA is reconnected. Therefore, the problem that it takes time to retransmit data wirelessly (second problem) cannot be solved.

The second conventional technique is a method in which the NWC acquires position measurement information related to the STA and determines the necessity of handover control according to the position of the STA. As the position measurement information, for example, GPS (Global Positioning System) or GNSS (Global Navigation Satellite System) information is used. When the NWC determines that the STA has crossed the desired boundary line A92 shown in FIG. 13, for example, based on the position measurement information, a method of initiating the handover control for the STA can be considered. However, this method is limited to the environment in which the position measurement information of the STA can be obtained. There is a problem that the handover control method based on the position measurement information cannot be implemented when the position is indoors where positioning is not possible, or when it is selected for the convenience of the user not to transmit the position measurement information to the NWC.

The third prior art is a method of handover control that solves the above-mentioned problems of the first and second conventional methods and utilizes the direction information of the directional beam in the millimeter wave band (see, for example, Patent Document 1). .. FIG. 15 is a diagram showing a configuration example of a wireless communication system according to the third prior art. The two APs shown in FIG. 15 are referred to as AP # 1 and AP # 2.

The AP can form a directional beam by the wireless communication unit. AP # 1 and AP # 2, respectively, transmit information on the beam directions of the directional beams B91 and B92 to the STA (not shown in FIG. 15) transmitted and received wirelessly to the NWC via the NWC interface unit. The NWC knows the sectors C91 and C92 of AP # 1 and AP # 2, respectively, in advance. Further, the NWC grasps in advance the information that the APs are adjacent to each other, for example, the directional beam B91 in the sector C91 of AP # 1 and the directional beam B92 in the sector C92 of AP # 2 are adjacent to each other. be able to.

FIG. 16 is a flow diagram showing an outline of an example of a handover control procedure in NWC. The handover control procedure in the NWC will be described with reference to FIGS. 15 and 16. The NWC handover control unit acquires beam direction information regarding the STA from the AP (step S9201). Whether or not the target STA (hereinafter referred to as the target STA) for determining the necessity of starting the handover control exists at either end of the sector of the AP (preset beam direction) in the handover control unit. (Step S9202). If the handover control unit determines YES in step S9202, the handover control unit monitors the radio quality between the target STA and the AP, and determines whether or not the radio quality is equal to or less than a predetermined threshold value (step S9203). If the handover control unit determines YES in step S9203, the handover control unit selects an AP to be the next connection destination of the target STA (step S9204). The handover control unit notifies the selected AP of the next connection destination of the change in the beam direction in order to accommodate the moving target STA (step S9205). By such a procedure of determining and instructing the handover control by the NWC, the STA does not need to search for APs existing in the vicinity by a plurality of wireless channels. Therefore, it is possible to reduce the time required for handover control.

FIG. 17 is a diagram showing an example of desired handover control according to the third prior art. In FIG. 17, the three APs are described as AP # 1, AP # 2, and AP # 3. The STA is connected to AP # 1. AP # 1 notifies the NWC of beam direction information regarding STA (step S9301). The movement path of the STA is in the direction of arrow A93. The STA is moving away from sector C91 of AP # 1 and trying to enter sector C93 of AP # 3. In the third prior art NWC, the directional beam B91 of AP # 1 is one of the directional beams at both ends in the sector C91 of AP # 1, and the directional beam B93 of AP # 3 is the sector of AP # 3. It can be grasped in advance that it is one of the directional beams at both ends in C93. Therefore, the NWC detects the change in the orientation of the STA shown in FIG. 17, and notifies the STA of the identifier of AP # 3 and the information of the radio channel by the handover instruction in the procedure shown in FIG. 16 (step S9302). The STA processes the reconnection using the AP identifier and the radio channel notified by the NWC. Therefore, the third prior art can reduce the time required to control the handover of the STA as compared with the first prior art. Further, unlike the second conventional technique, the third conventional technique does not require acquisition of position measurement information by an external system.

Japanese Patent No. 6530720

In the third prior art, when the STA moves toward the same beam direction that is neither of both ends of the sector of the AP, the beam direction information to the STA acquired by the handover control unit of the NWC does not change. Therefore, the NWC cannot determine the start of handover control. FIG. 18 is a diagram showing this problem event.

In FIG. 18, the STA connected to AP # 1 is moving away from sector C91 of AP # 1 by the movement path in the direction of arrow A94 and is about to enter sector C92 of AP # 2. In this movement path, the beam direction to the STA does not change. The directional beam B94 of AP # 1 is neither of the directional beams at both ends in the sector C91, and the directional beam B95 of AP # 2 is neither of the directional beams at both ends of the sector C92. Therefore, it is considered that the third prior art NWC cannot determine an appropriate timing to start the handover control by using the beam direction information to the STA. The NWC shown in FIG. 18 has no choice but to determine the timing to start the handover control based on the radio quality such as the received power, as in the first conventional technique. That is, in the third conventional technique, the beam direction information cannot be utilized, and the basis of the handover control determination of the NWC is the same as that of the first conventional technique, so that there remains a problem that the accuracy of the handover control determination is lowered.

In view of the above circumstances, an object of the present invention is to provide a wireless communication system, a network control device, a network control method and a program capable of starting a handover at an appropriate timing and reducing the time required for the handover. There is.

One aspect of the present invention is a wireless communication system having a network control device and a plurality of access points, wherein the access points include a wireless communication unit that wirelessly communicates with a terminal station by a beam having directional beam, and the wireless communication unit. The terminal is based on a direction estimation unit that estimates the direction to the terminal station based on the beam information used by the communication unit and a round-trip transmission time in wireless communication between the wireless communication unit and the terminal station. The network control device includes a distance estimation unit that estimates the distance to the station, and the network control device acquires the information of the direction estimated by the direction estimation unit and the information of the distance estimated by the distance estimation unit. The key to handover of the terminal station based on the information on the position of the terminal station estimated using the information on the direction and the information on the distance acquired by the acquisition unit and the information on the position of the access point. It is used for connection with the access point of the next connection destination via the determination unit for determining whether or not and the access point to which the terminal station is connected when the determination unit determines that handover is necessary. It is a wireless communication system including a notification unit for notifying the terminal station of information.

One aspect of the present invention is information on the direction to the terminal station estimated based on the information of the beam used for wireless communication with the terminal station by the access point that wirelessly communicates with the terminal station by the directional beam. And an acquisition unit that acquires information on the distance to the terminal station estimated based on the round-trip transmission time of the access point in wireless communication with the terminal station, information in the direction acquired by the acquisition unit, and A determination unit that determines the necessity of handover of the terminal station based on the information on the position of the terminal station estimated using the information on the distance and the information on the position of the access point, and the determination unit that determines the necessity of handover. When it is determined that is necessary, a notification unit that notifies the terminal station of information used for connection with the access point of the next connection destination via the access point to which the terminal station is connected. It is a network control device provided.

One aspect of the present invention is a network control method executed by a wireless communication system having a network control device and a plurality of access points, wherein the access points wirelessly communicate with a terminal station by a directional beam. A direction estimation step that estimates the direction to the terminal station based on the information of the beam used in the communication unit, and a round-trip transmission time of the access point in wireless communication between the wireless communication unit and the terminal station. The distance estimation step for estimating the distance to the terminal station based on the above, and the network control device acquires the information on the direction estimated in the direction estimation step and the information on the distance estimated in the distance estimation step. The acquisition step to be performed, the position information of the terminal station estimated by the network control device using the information of the direction and the information of the distance acquired in the acquisition step, and the information of the position of the access point. A determination step for determining the necessity of handover of the terminal station based on the above, and a determination step in which the network control device determines that handover is necessary in the determination step, via the access point to which the terminal station is connected. This is a network control method including a notification step for notifying the terminal station of information used for connection with the access point of the next connection destination.

One aspect of the present invention is a program for causing a computer to function as the above-mentioned network control device.

According to the present invention, it is possible to start the handover at an appropriate timing and reduce the time required for the handover.

It is a figure which shows the structural example of the wireless communication system by 1st Embodiment of this invention. It is a functional block diagram which shows the structural example of AP by the same embodiment. It is a functional block diagram which shows the structural example of NWC by the same embodiment. It is a functional block diagram which shows the detailed configuration example of the handover control determination part by this embodiment. It is a flow chart which shows the operation of the wireless communication system by this embodiment. It is a figure which shows the configuration example of the wireless communication system by 3rd Embodiment. It is a functional block diagram which shows the structural example of AP by the same embodiment. It is a figure which shows the configuration example of the wireless communication system by 4th Embodiment. It is a functional block diagram which shows the structural example of AP by the same embodiment. It is a function block diagram which shows the detailed configuration example of the handover control function part by this embodiment. It is a functional block diagram which shows the detailed configuration example of the handover control determination part by this embodiment. It is a device block diagram which shows the hardware configuration example of NWC by 1st to 4th Embodiment. It is a figure which shows the conventional handover control. It is a figure which shows the outline of the 1st prior art. It is a figure which shows the configuration example of the wireless communication system by the 3rd prior art. It is a flow chart which shows the outline of the handover control procedure in NWC by the prior art. It is a figure which shows the example of the desired handover control by the prior art. It is a figure which shows the case where the NWC by the prior art cannot determine the start of the handover control.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, in a wireless communication system capable of forming a directional beam and transmitting a wideband signal, the handover control of the access point (AP) to which the STA is connected is appropriate as the position of the terminal station (STA) moves. It starts at an appropriate timing and reduces the time required to search for the reconnection destination AP due to handover control.

In the wireless communication system of this embodiment, high frequency band radio is used for communication between AP and STA. The AP detects information on the direction of the STA from its own AP by a directional beam, which is a beam having a narrow directivity. In addition, the AP detects information on the distance of the STA from its own AP by transmitting a wideband signal. The AP notifies the upper network control device (NWC) of the information on the direction and distance of the STA from the own AP. The NWC grasps the positional relationship between the STA, the AP to which the STA is connected, and the adjacent AP by using the STA position information obtained from the STA direction and distance information notified from the AP. The adjacent AP is an AP adjacent to the AP to which the STA is connected, and can be the next connection destination of the STA. Based on the grasped positional relationship, the NWC starts handover control at an appropriate timing for the STA, and is a wireless channel used for wireless communication between the AP selected as the next connection destination and the AP of the next connection destination. Instruct information such as.

When the NWC determines that it is necessary to start the handover control in the STA, the NWC notifies the AP identifier and the radio channel information of the next connection destination AP via the AP to which the STA is connected by the above instruction. The AP identifier is information that uniquely identifies the AP. By notifying this information, the NWC causes the STA to search for the connection destination AP using the notified AP identifier and wireless channel. The NWC may determine the start of handover control by further using the speed and the angular velocity obtained by differentiating the distance and direction information of the STA.

According to the above, the NWC uses the position information of the STA obtained by wireless communication in the high frequency band without depending on an external system such as GPS, and has a positional relationship with the connected AP of the moving STA and the adjacent AP (in any case). It is possible to recognize (whether the AP is close to each other) and cause the STA to start the handover control at an appropriate timing. Specifically, the position information of the STA is obtained from the beam direction information used by the connected AP for wireless transmission / reception with the STA and the estimated distance information between the connected AP and the STA. Further, in the implementation of the handover control, the NWC provides the STA with information such as the AP identifier and the radio channel identifier of the adjacent AP to be reconnected. As a result, the time required for handover control can be reduced. A detailed embodiment will be described below.

[First Embodiment]
(Explanation of the overall configuration of the wireless communication system)
FIG. 1 is a diagram showing a configuration example of the wireless communication system 1 of the first embodiment. The wireless communication system 1 has an AP10 and an NWC20. The wireless communication system 1 has a plurality of AP10s, but FIG. 1 shows two AP10s. The two AP10s are described as AP10-1 and AP10-2, respectively. Further, the sector C of AP10-i (i = 1, 2) is referred to as a sector Ci. The sector Ci is a range in which wireless communication is possible by the antenna element of AP10-i. The AP10-i may have a plurality of sectors in different directions. Each AP10 is connected to the NWC20.

In FIG. 1, the STA (terminal station) 30 is located in an area where the sector C1 of AP10-1 and the sector C2 of AP10-2 overlap. The STA 30 is connected to the AP10-1 by the directional beam B1 and is in a state of being able to communicate with the AP10-1. At the same time, the STA 30 moves in the direction of arrow A1. The arrow A1 is a path that leaves the AP10-1 without changing its direction. That is, the STA 30 moves away from AP10-1 toward AP10-2. The radio quality of the STA 30 decreases as the distance from AP10-1 increases. Therefore, there is a need for handover control in the STA 30. The ideal reconnection destination for the STA 30 is the directional beam B2 of the AP10-2. In this case, since the beam direction does not change, in the third prior art, the handover determination is performed based on the radio quality (received power, etc.).

When the AP10 is communicating wirelessly with the STA30, the AP10 estimates the direction of the STA30 as seen from the own AP based on the antenna directional beam used for the wireless communication, as in the third conventional technique. Further, the AP10 wirelessly communicating with the STA 30 can estimate the distance from the own AP to the STA 30 by utilizing a wide band signal, unlike the third conventional technique. The AP10 generates STA position information indicating the estimated position of the STA 30, and notifies the NWC 20 of the generated STA position information. The STA position information is represented by the beam direction of the AP10 and the estimated distance from the AP10 to the STA30. The beam direction of AP10 represents the direction of STA30 as seen from the own AP. The AP10-i notifies the NWC20 of the information on the beam direction of the AP10-i and the information on the estimated distance from the AP10-i to the STA30, and the NWC20 uses the notified information to notify the AP10-i. The STA position information of the STA 30 as seen from the above may be generated. In the case of FIG. 1, AP10-1 communicating with STA30 notifies NWC20 of STA position information (step S11).

Based on the STA position information, the NWC 20 determines whether or not it is necessary to start the handover control for reconnecting the STA 30 to an adjacent AP different from the AP10 of the current connection destination. In FIG. 1, the adjacent AP is AP10-2. When the NWC 20 determines that it is necessary to start the handover control of the STA 30, it transmits a reconnection instruction instructing the reconnection destination to the AP10-2 to the STA30 via the AP10-1 (step S12). The reconnection instruction includes information necessary for the STA 30 to wirelessly connect to the AP10-2. Specifically, these pieces of information are the AP identifier of AP10-2 and the identifier of the radio channel. AP10-1 wirelessly notifies STA30 of the reconnection instruction received from NWC20. When the STA 30 receives the reconnection instruction, the STA 30 cancels the wireless connection with the AP10-1.

When the STA 30 cancels the wireless connection with the AP10-1, the STA 30 starts the procedure for reconnecting to the AP10-2 by using the AP identifier instructed by the NWC20 and the identifier of the wireless channel by the reconnection instruction. The STA 30 can attempt to reconnect with the AP 10-2 by transmitting a control signal for searching a peripheral AP such as a beacon using the instructed radio channel. Alternatively, the STA 30 may search only the indicated radio channel. The STA 30 responds to AP10-2 by transmitting a radio frame requesting a wireless connection when receiving a control signal such as a beacon from AP10-2 of the designated AP identifier by the designated radio channel. It is also possible to try to reconnect.

Note that, in FIG. 1, only the minimum number of AP10s and STA30s required for the explanation of the first embodiment are displayed. The same operation can be performed even when more AP10s or STA30s are present.

(Explanation of configuration of AP10)
FIG. 2 is a functional block diagram showing a configuration example of the AP10 of the first embodiment. In FIG. 2, only the functional blocks related to the present embodiment are extracted and shown. The AP 10 includes an antenna 11, a wireless communication unit 12, a direction estimation unit 13, a distance estimation unit 14, and an NWC interface unit 15.

Antenna 11 transmits and receives wireless signals. The wireless communication unit 12 wirelessly communicates with the STA 30 (not shown in FIG. 2) by a directional beam B having a narrow directivity. The AP10 can change the direction of the directional beam B formed by the antenna 11 within a certain range. As an example, this fixed range is the range of sector C. In the figure, the directional beams B in each direction are described as directional beams B-1 to Bn. The directional beams B-1 and Bn are both ends of sector C. The wireless communication unit 12 can output transmission / reception time information indicating the time transmitted / received wirelessly to the STA 30 to the direction estimation unit 13 and the distance estimation unit 14.

The direction estimation unit 13 acquires transmission / reception time information from the wireless communication unit 12 and records it together with the beam direction information. The beam direction information indicates the beam direction of the directional beam B used in the wireless communication unit 12. The direction estimation unit 13 adds transmission / reception time information indicating the time when the beam direction information is obtained to the beam direction information, and outputs the beam direction information to the NWC interface unit 15.

The distance estimation unit 14 estimates the distance to the STA 30 using the transmission / reception time information acquired from the wireless communication unit 12. The distance estimation unit 14 outputs estimated distance information indicating the estimated distance to the NWC interface unit 15.

Time Of Arrival (ToA) is an example of the distance estimation method performed by the distance estimation unit 14. For example, if there is already some reciprocating radio signal sequence between the AP10 and the STA 30, the AP10 measures the reciprocating time. Specifically, the distance estimation unit 14 sets the time when the wireless communication unit 12 of the AP 10 transmits some radio signal to the STA 30 to T ₀ , and the time when the wireless communication unit 12 receives the response signal to the radio signal from the STA 30. Record as _1. Further, it is assumed that the response time from when the STA 30 receives the radio signal from the AP 10 to when the response signal is transmitted is defined as _{T Response. In this case, the distance d AP, STA} between AP10 and STA30 is determined by the recorded time T ₀ and time T ₁ , the specified response time T _Response, and the speed of light c (= 3 × 108 (m / s)). , Can be estimated by equation (1).

In the present embodiment, if the transmission / reception time of AP10 (or STA30) can be obtained from the wireless communication information that can be acquired by the wireless communication unit 12 by another method, the information is not limited to the above method. The distances d _{AP and STA} may be estimated based on.

By the above method, AP10 does not need to use a dedicated external system for measuring the distance from STA30. After estimating the distance between the AP 10 and the STA 30, the distance estimation unit 14 records the estimated distance information indicating the estimated distance and outputs the estimated distance information to the NWC interface unit 15. The distance estimation unit 14 may add the transmission / reception time information used for estimation to the estimated distance information.

The NWC interface unit 15 adds the STA identifier of the STA 30 and the AP identifier of its own device to the estimated distance information calculated using the information obtained by wireless communication with the STA 30 and the STA position information in which the beam direction information is set. In addition, the NWC20 is notified. The STA identifier is information that uniquely identifies the STA 30. The NWC 20 records the STA position information of each STA 30 notified from the AP 10. Alternatively, the NWC interface unit 15 may notify the NWC 20 by adding the STA identifier of the STA 30 and the AP identifier of its own device to the estimated distance information and the beam direction information. The NWC 20 records the estimated distance information of each STA 30 notified from the AP 10 and the beam direction information in association with each other as STA position information. Further, when the NWC interface unit 15 receives the reconnection instruction to the STA 30 based on the determination result that the handover control is started from the NWC 20, the NWC interface unit 15 outputs the reconnection instruction to the wireless communication unit 12. The wireless communication unit 12 wirelessly transmits a reconnection instruction to the STA 30.

(Explanation of the configuration of NWC20)
FIG. 3 is a functional block diagram showing a configuration example of the NWC 20 of the first embodiment. In FIG. 3, only the functional blocks related to the present embodiment are extracted and shown. The NWC 20 determines whether or not the handover control of the STA 30 needs to be started. The NWC 20 includes an AP interface unit 21, a handover control determination unit 23, and a storage unit 22.

The AP interface unit 21 communicates with a plurality of AP10s under the control of the NWC 20. The AP interface unit 21 stores the STA position information of each STA 30 collected from each AP 10. Alternatively, the AP interface unit 21 records the estimated distance information of each STA 30 collected from each AP 10 and the beam direction information in association with each other as STA position information. The AP interface unit 21 notifies the handover control determination unit 23 of the recorded STA position information.

The storage unit 22 stores information about the candidate AP10 that is the handover destination of the STA 30. Specifically, the storage unit 22 stores the AP position information of each AP and the AP information in advance. The AP position information indicates the position of AP10. The AP position information may be a record of the position of each AP10 at the time of stationing design in a coordinate system fixed on a map prepared in advance. Alternatively, the storage unit 22 may acquire the position information of the AP10 measured by the GPS provided in each AP10 and store it as the AP position information. If the storage unit 22 can store the information indicating the position of each AP10, the storage unit 22 may acquire the information by any method. The storage unit 22 notifies the handover control determination unit 23 of the positional relationship information indicating the positional relationship of the plurality of AP10s based on the positional information of each AP10. The positional relationship information is, for example, information including the positional information of each of the plurality of AP10s including the AP10 to which the STA 30 is connected. The AP information indicates the AP identifier, radio frequency and radio channel of each AP10. The AP information further indicates information on the connection area of each AP10. The connection area is represented by, for example, the combined range of one or more sectors C of AP10.

The handover control determination unit 23 makes a handover control determination of the STA 30. Details of the handover control determination unit 23 will be described later with reference to FIG.

(Explanation of Detailed Configuration of Handover Control Judgment Unit 23)
FIG. 4 is a functional block diagram showing a detailed configuration example of the handover control determination unit 23 included in the NWC 20 of the first embodiment. The handover control determination unit 23 includes a STA position information acquisition unit 231, an AP information acquisition unit 232, a determination unit 233, and a reconnection instruction unit 234.

The STA position information acquisition unit 231 acquires the STA position information from the AP interface unit 21, and inputs the acquired STA position information to the determination unit 233. The AP information acquisition unit 232 acquires information on the AP 10 that can be the reconnection destination of the handover control in the vicinity of the target STA 30 (hereinafter referred to as the target STA) for determining whether or not the handover control needs to be started. The AP10 that can be the reconnection destination is an AP10 (hereinafter referred to as an adjacent AP) adjacent to the AP10 to which the target STA is currently connected (hereinafter referred to as a connected AP). For example, the AP next to the target STA is connected to the NWC20, and among the AP10s different from the connected AP, the AP10 at a position within a predetermined distance from the position of the connected AP or the AP10 at a position closer to the connected AP is in order. A predetermined number of selected AP10s. The position of the AP 10 is obtained from the positional relationship information notified from the storage unit 22. The AP information acquisition unit 232 acquires the position information of the connected AP and the AP position information and the AP information of the adjacent AP and inputs them to the determination unit 233. Positional relationship information may be used as the position information of the connected AP and the AP position information of the adjacent AP.

The determination unit 233 makes a handover control determination based on the STA position information input from the STA position information acquisition unit 231 and the information input from the AP information acquisition unit 232. The reconnection instruction unit 234 acquires the determination result by the determination unit 233 and the information necessary for the STA 30 to search for the reconnection destination AP10, and outputs the information to the AP interface unit 21.

The determination unit 233 makes a handover control determination when the target STA moves away from the connected AP. In the handover control determination, whether or not the determination unit 233 causes the target STA to start handover control based on the positional relationship between the target STA and the adjacent AP indicated by the STA position information of the target STA and the AP position information of the adjacent AP. , When starting, the AP10 to be the next connection destination is determined. In addition, there are the following examples as a method of determining whether or not to start the handover control. One is a method in which a distance threshold value is set in advance for each AP10 shown in FIG. 1, and when the distance between the target STA and the connected AP exceeds the distance threshold value, it is determined that the handover control is started. Another example is a method in which the information of the connection area of each AP 10 is stored in the storage unit 22 in advance, and when the target STA crosses the boundary of the connection area, it is determined that the handover control is started. It is conceivable to design this connection area in consideration of the communication distance, the movable range of the directional beam, the direction, and the like. Further, as a method of determining using the distance threshold value, it is conceivable to change the distance threshold value for each direction, considering that the antenna gains of the directional beams B-1 to Bn of each AP10 are different for each direction. ..

Further, there is the following example as a method of selecting the AP10 of the next connection destination of the target STA when the determination unit 233 determines that the handover control is started. One is a method of selecting the closest AP10 by comparing the linear distances between two points between the target STA and the adjacent APs. The position of the target STA can be obtained by adding the position of the STA 30 as seen from the AP 10 indicated by the STA position information of the target STA to the position of the connected AP. Further, there is a method of selecting the AP10 in which the position of the target STA is in the connection area in consideration of each of the above connection areas. Further, when the position of the target STA enters the connection area of a plurality of AP10s, a method of selecting the AP10 closest to the target STA can be considered.

When the determination unit 233 determines the above determination result, that is, the start of the handover control, the fact of the start, the AP identifier of the next connection destination AP10, the radio channel identifier used by the AP10, and the like, etc. The information is output to the reconnection instruction unit 234. The reconnection instruction unit 234 outputs the determination result to the AP interface unit 21 including the determination result.

FIG. 5 is a flow chart showing the operation of the wireless communication system 1. The direction estimation unit 13 of the AP 10 includes transmission / reception time information indicating the time when the signal is transmitted or received in the information indicating the beam direction when the wireless communication unit 12 wirelessly transmits or receives the signal to and from the STA 30. Is added and output to the NWC interface unit 15 (step S101). The distance estimation unit 14 estimates the distance to the STA 30 using the transmission / reception time information acquired from the wireless communication unit 12 (step S102). The distance estimation unit 14 outputs estimated distance information indicating the estimated distance to the NWC interface unit 15. The NWC interface unit 15 adds the STA identifier of the STA 30 and the AP identifier of the own device to the STA position information in which the estimated distance information and the beam direction information are set, and notifies the NWC 20 (step S103).

Each AP10 performs the processes of steps S101 to S103 for each of the connected STA30s, for example, at predetermined cycles. The AP10 may perform the process of step S101 and the process of step S102 in parallel, or may perform the process of step S101 after the process of step S102.

The AP interface unit 21 of the NWC 20 receives the STA position information of each STA 30 from each AP 10 (step S201). The AP interface unit 21 notifies the handover control determination unit 23 of the STA position information of each received STA 30. The STA position information acquisition unit 231 of the handover control determination unit 23 inputs the STA position information acquired from the AP interface unit 21 to the determination unit 233.

The AP information acquisition unit 232 identifies the target STA and the connected AP based on the STA identifier and the AP identifier set in the STA position information. The AP information acquisition unit 232 selects an adjacent AP of the connected AP with reference to the positional relationship information acquired from the storage unit 22 (step S202). The AP information acquisition unit 232 reads the AP information of the adjacent AP from the storage unit 22. The AP information acquisition unit 232 reads the position information of the connected AP and the AP position information and the AP information of the adjacent AP from the storage unit 22 and inputs them to the determination unit 233.

The determination unit 233 determines whether the target STA is moving away from the connected AP by using the time-series STA position information of the target STA (step S203). When the determination unit 233 determines that the target STA is moving away from the connected AP (step S203: YES), the determination unit 233 uses the position information of the connected AP and the AP position information and AP information of the adjacent AP. Then, it is determined whether or not to start the handover control of the target STA (step S204). For example, the determination unit 233 determines that the handover control is started when the distance between the target STA and the connected AP exceeds the distance threshold value or when the target STA crosses the boundary of the connection area.

When the determination unit 233 determines that the handover control of the target STA is started (step S204: YES), the determination unit 233 uses the position information of the connected AP and the AP position information and AP information of the adjacent AP from among the adjacent APs. The next connection destination AP10 is selected (step S205). For example, the determination unit 233 may select the AP10 at the position closest to the position of the target STA from the adjacent APs, or may select the AP10 having a connection area including the position of the target STA.

The determination unit 233 includes information indicating the target STA, information indicating the connecting AP, the AP identifier of the next connection destination AP10, the radio frequency and the radio channel identifier used for connecting to the next connection destination AP10, and the like. The information is output to the reconnection instruction unit 234. The reconnection instruction unit 234 sends a reconnection instruction in which the destination information indicating the target STA and the AP identifier, radio frequency, and radio channel identifier of the next connection destination AP10 are set via the AP interface unit 21 to the connecting AP. (Step S206). The reconnection instruction unit 234 may further notify the AP10 of the next connection destination to instruct the position of the target STA to change the beam direction.

When the determination unit 233 determines that the target STA has not moved away from the connected AP (step S203: NO), or determines that the handover control of the target STA is not started (step S204:). NO), the process ends.

The NWC interface unit 15 of the connected AP receives the reconnection instruction transmitted from the NWC 20 in step S260, and outputs the received reconnection instruction to the wireless communication unit 12. The wireless communication unit 12 wirelessly transmits a reconnection instruction from the antenna 11. When the target STA receives the reconnection instruction, it disconnects from the connecting AP and reconnects with the next connection destination AP10 using the information set in the reconnection instruction.

[Second Embodiment]
In the first embodiment, the NWC uses the position information at a certain moment of the STA to determine whether or not the handover control needs to be started for the moving STA. However, when the STA frequently changes the moving direction, the NWC may frequently cause the STA to perform handover control by the method shown in the first embodiment. Due to frequent handover control instructions, there may be a problem that the overhead increases and the throughput deteriorates, or a problem that the control sequence is repeated for a certain period of time and wireless connection becomes impossible. In view of such a problem, the second embodiment prevents the NWC from causing the STA to perform frequent handover control.

The configuration of the wireless communication system of this embodiment is the same as that of the first embodiment shown in FIG. However, the NWC 20 of the second embodiment determines the necessity of starting the handover control based on the information regarding the movement obtained from the STA position information of the moving STA 30 shown in FIG. The information regarding the movement of the STA 30 is motion information such as a velocity vector estimated by differentiating the STA position information or an angular velocity vector. The NWC 20 determines whether or not the handover control needs to be started in consideration of the estimated moving speed vector or the angular velocity vector. Hereinafter, the differences between the second embodiment and the first embodiment will be mainly described.

The NWC 20 acquires STA position information at different times a plurality of times (twice or more). The determination unit 233 of the NWC20 is estimated distance _dAP the STA location information at a certain time _{t 0 indicates, STA} and the estimated distance d _'AP indicated the following STA location information of the time _{t 1} at time _{t 0, STA} and, Using the time difference Δt = t _{1 −} t ₀ , the estimated speed vector v of the target STA is calculated by the following equation (2).

The determination unit 233 of the NWC20, the direction information theta _AP indicating STA location information at a certain time _{t 0 is, STA,} the time _{t 0} of the next time _{t 1} in the direction information theta _'AP indicated by the STA location _{information, STA,} and , The estimated angular velocity ω of the target STA is calculated by the following equation (3) using the time difference Δt = t _{1 −} t _0.

As described above, the determination unit 233 of the NWC 20 estimates the velocity vector or the angular velocity vector of the target STA based on the STA position information at different times, and uses the estimated velocity vector or the angular velocity vector to control the handover of the target STA. Determine if it is necessary to start. When the determination unit 233 determines that the target STA moves away from the connected AP based on the STA position information, the positional relationship between the target STA and the neighboring AP, and the estimated velocity vector v or the estimated angular velocity vector ω of the target STA. Based on the above, it is determined whether or not the target STA is to start the handover control. As an example, the determination unit 233 determines that the handover control has started based on the STA position information of the target STA as in the first embodiment, and then further changes the positive / negative symbol of the estimated speed vector v within a predetermined period, or , When it is determined that the positive / negative symbol change of the estimated angular velocity ω within a predetermined period is not more than a predetermined number of times, it is determined that the target STA starts the handover control.

The determination unit 233 may determine that the handover control starts when both the positive / negative symbol change of the estimated velocity vector v and the positive / negative symbol change of the estimated angular velocity ω are less than or equal to a predetermined number of times, and the positive / negative symbol of the estimated velocity vector v. When either the change or the change of the positive or negative symbol of the estimated angular velocity ω is less than or equal to a predetermined number of times, it may be determined that the handover control is started.

Also, the predetermined period and the predetermined number of times are arbitrary set values. These set values may be set in advance in the determination unit 233. Alternatively, the determination unit 233 or manually may change these set values according to the position, speed, angular velocity of the target STA and the radio quality before and after the handover control. Any setting method can be used for setting a predetermined period and a predetermined number of times. Further, the predetermined number of times of the estimated velocity vector v and the predetermined number of times of the estimated angular velocity ω may be common or different.

The operation of the NWC 20 after the determination unit 233 determines the necessity of starting the handover control based on the estimated velocity vector v and the estimated angular velocity ω as described above is the same as that of the first embodiment.

The NWC 20 of the second embodiment can determine the start of handover control by the macroscopic movement of the STA 30 using one or both of the estimated velocity vector v and the estimated angular velocity ω. Therefore, when the STA 30 frequently changes the moving direction, it is possible to avoid excessive handover control. For example, when the STA 30 moves back and forth between the boundary zones of a plurality of AP10s, in the first embodiment, the handover control is frequently performed, and the throughput may be deteriorated or the wireless connection itself may not be possible. be. In the second embodiment, it is possible to avoid frequent handover control for the STA 30 performing such a movement and maintain the connected AP10 to maintain the radio quality.

[Third Embodiment]
In the first and second embodiments, the position of the AP was fixed. In this embodiment, the position of the AP moves.

FIG. 6 is a diagram showing a configuration example of the wireless communication system 1a according to the third embodiment. The wireless communication system 1a has an AP10a and an NWC20a. The wireless communication system 1a has a plurality of AP10a, but FIG. 6 shows two AP10a. The two AP10a are described as AP10a-1 and AP10a-2, respectively. AP10a-1 does not move and AP10a-2 can move. AP10a-2 is mounted on, for example, a drone, a mobile base station vehicle, or the like. As the non-moving AP10a, the AP10 of the first embodiment may be used.

In the first and second embodiments described above, the NWC uses the position information or motion information of the target STA to determine whether or not to start handover control for the target STA. In the first and second embodiments, it is necessary to record in advance the station design position of the AP in the coordinate system in the storage unit of the NWC in order to determine the necessity of starting the handover control. However, as shown in FIG. 6, a movable AP10a is also connected under the NWC20a. In the case of the NWC of the first and second embodiments, if the position of the AP changes with time, the information stored in the storage unit cannot respond to the change, and appropriate handover control is performed for the target STA. It may not be possible to specify the reconnection destination of. Therefore, in the third embodiment, in view of such a problem, each AP10a is provided with a function of acquiring its own position information and notifying the NWC20a of the acquired position information.

FIG. 7 is a functional block diagram showing a configuration example of AP10a according to the third embodiment. The difference between the configuration of the AP10a shown in FIG. 7 and the configuration of the AP10 of the first embodiment shown in FIG. 2 is that the AP10a further includes the AP position information notification unit 16. The AP position information notification unit 16 acquires AP position information indicating the position of the AP10a itself periodically or irregularly, and notifies the NWC20a of the acquired AP position information via the NWC interface unit 15. As an example of the method of acquiring the AP position information in the AP position information notification unit 16, a positioning method using, for example, GPS can be used.

The configuration of the NWC 20a is the same as that of the NWC 20 of the first embodiment shown in FIG. However, the storage unit 22 of the NWC 20a is different in that the AP position information is updated by storing the AP position information notified from the AP 10a.

According to the third embodiment, the NWC 20a performs appropriate handover control for the STA based on the latest position information of the AP10a by grasping the position information of each AP10a that changes with time. It becomes possible.

[Fourth Embodiment]
In the first to third embodiments described above, the NWC uses the position information or the motion information of the target STA to determine whether or not the handover control of the target STA needs to be started. However, when the handover control is mounted only on a single device, that is, the NWC, there is a problem that the handover control cannot be normally performed due to a failure of the device, an increase in the processing load, or the like. In order to solve such a problem, in the present embodiment, any AP is provided with a function related to the collection of the position information of the STA possessed by the NWC and the handover control determination. Then, the AP performs handover control for each STA as an alternative to the NWC. In the following description, such an AP will be referred to as a master controller. This embodiment will be described focusing on the differences from the above-described embodiments.

FIG. 8 is a diagram showing a configuration example of the wireless communication system 1b according to the fourth embodiment. The wireless communication system 1b has an AP10b and an NWC20. The wireless communication system 1b has a plurality of AP10b units, but FIG. 8 shows two AP10b units. The plurality of AP10b and NWC20 are connected to the network 40. The two AP10b units are described as AP10b-1 and AP10b-2, respectively. The wireless communication system 1b may further have the AP10 of the first or second embodiment, and may further have the AP10a of the third embodiment. Further, the wireless communication system 1b may have one AP10b and one or more AP10s or AP10a. In FIG. 8, it is assumed that the NWC 20 is disconnected from the network 40 due to some kind of failure. In this case, one of the plurality of AP10b stations becomes the master control device.

In FIG. 8, the AP10b-2 selected as the master control device collects the position information of the STA 30 under the AP10b-1 and determines the handover control. Since these functions of AP10b-2 are equivalent to those of NWC20 and 20a in the first to third embodiments, detailed description thereof will be omitted here. In the example shown in FIG. 8, AP10b-2 is selected as the master control device, but any one station may be selected as the master control device among the AP10bs connected to each other by any method. .. For example, each AP10b may autonomously determine which AP10b serves as the master control device based on predetermined predetermined conditions, and a monitoring system (not shown) that monitors and controls the wireless communication system 1b. May instruct AP10b to become the master control device according to the input of the maintainer. Then, from the once selected master control device, its role or function can be transferred to another interconnected AP10b by any method.

FIG. 9 is a functional block diagram of a configuration example of AP10b according to the fourth embodiment. The difference between the configuration of AP10b shown in FIG. 9 and the configuration of AP10 of the first embodiment shown in FIG. 2 is that AP10b includes an inter-AP interface unit 17 instead of the NWC interface unit 15 and handover control. The point is that the functional unit 18 is further provided. The AP-to-AP interface unit 17 transmits / receives data to / from another AP10b. The above differences may be applied to AP10a of the third embodiment shown in FIG. 7.

FIG. 10 is a block diagram showing a detailed configuration of the handover control function unit 18 of the AP10b. The handover control function unit 18 includes a storage unit 181 and a handover control determination unit 182. The handover control function unit 18 has the same function as the handover control determination unit 23 of the NWCs 20 and 20a of the first to third embodiments. That is, the storage unit 181 and the handover control determination unit 182 have the same functions as the storage unit 22 and the handover control determination unit 23, respectively.

FIG. 11 is a block diagram showing a detailed configuration of the handover control determination unit 182. The handover control determination unit 182 includes an STA position information acquisition unit 1821, an AP information acquisition unit 1822, a determination unit 1823, and a reconnection instruction unit 1824. The STA position information acquisition unit 1821, AP information acquisition unit 1822, determination unit 1823, and reconnection instruction unit 1824 are the STA position information acquisition unit 231 and AP included in the handover control determination unit 23 of the first embodiment shown in FIG. 4, respectively. It has the same functions as the information acquisition unit 232, the determination unit 233, and the reconnection instruction unit 234. According to the configuration examples shown in FIGS. 10 and 11, the master control device realizes the same function as the NWC.

The handover control function unit 18 is connected to another AP10b via the inter-AP interface unit 17. The AP-to-AP interface unit 17 inputs the STA position information transmitted by another AP10b. Further, the inter-AP interface unit 17 outputs an instruction for starting the handover control to the STA 30 to another AP 10b to which the STA 30 is connected.

With the above configuration, in step S101 of FIG. 5, the direction estimation unit 13 of AP10b outputs information indicating the beam direction to the inter-AP interface unit 17, and in step S102 of FIG. 5, the distance estimation unit 14 outputs the estimated distance information. Is output to the inter-AP interface unit 17. In step S103 of FIG. 5, the AP-to-AP interface unit 17 of the AP10b notifies the master control device of the STA position information. When AP10b is a master control device, the process of step S103 in FIG. 5 is not performed.

The master control device performs the processes of steps S201 to S206 of FIG. However, in step S201, the inter-AP interface unit 17 of the master control device notifies the handover control function unit 18 of the STA position information of each STA 30 received from the other AP 10b and the STA position information generated by the own device. .. Further, in step S206, the reconnection instruction unit 1824 transmits a reconnection instruction to the connecting AP via the inter-AP interface unit 17. The inter-AP interface unit 17 outputs a reconnection instruction to the wireless communication unit 12 when the connected AP is a master control device.

In the fourth embodiment, since the handover control determination of the STA 30 can be determined by the function of the AP10b serving as the master control device, appropriate handover control can be performed even when a failure of the NWC 20 or the like occurs.

The functions of NWC20 and 20a in the above-described embodiment may be realized by a computer. In that case, the program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read by the computer system and executed. The term "computer system" as used herein includes hardware such as an OS and peripheral devices. Further, the "computer-readable recording medium" refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, or a CD-ROM, or a storage device such as a hard disk built in a computer system. Further, a "computer-readable recording medium" is a communication line for transmitting a program via a network such as the Internet or a communication line such as a telephone line, and dynamically holds the program for a short period of time. It may also include a program that holds a program for a certain period of time, such as a volatile memory inside a computer system that serves as a server or a client in that case. Further, the above-mentioned program may be a program for realizing a part of the above-mentioned functions, and may be a program for realizing the above-mentioned functions in combination with a program already recorded in the computer system.

A hardware configuration example of NWC20 will be described. FIG. 12 is a device configuration diagram showing a hardware configuration example of the NWC 20. The NWC 20 includes a processor 71, a storage unit 72, a communication interface 73, and a user interface 74. The NWC 20a has the same configuration.

The processor 71 is a central processing unit that performs calculations and controls. The processor 71 is, for example, a CPU. The processor 71 reads a program from the storage unit 72 and executes it. The storage unit 72 further has a work area for the processor 71 to execute various programs and the like. The communication interface 73 is connected so as to be able to communicate with another device. The user interface 74 is an input device such as a button, a keyboard, and a pointing device, and a display device such as a lamp and a display. An artificial operation is input by the user interface 74.

The function of the handover control determination unit 23 is realized by the processor 71 reading a program from the storage unit 72 and executing it. All or part of these functions may be realized by using hardware such as ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), and FPGA (Field Programmable Gate Array). The AP interface unit 21 is realized by the communication interface 73. Note that some of these functions may be realized by the processor 71 reading a program from the storage unit 72 and executing the program.

According to the above-described embodiment, the wireless communication system has a network control device and a plurality of access points. The access point includes a wireless communication unit, a direction estimation unit, and a distance estimation unit. The wireless communication unit wirelessly communicates with the terminal station by means of a directional beam. The direction estimation unit estimates the direction to the terminal station as seen from itself based on the beam information used by the wireless communication unit. The distance estimation unit estimates the distance to the terminal station based on the round-trip transmission time in the wireless communication between the wireless communication unit and the terminal station. The network control device includes an acquisition unit, a determination unit, and a notification unit. The acquisition unit, the direction information estimated by the direction estimation unit, and the distance information estimated by the distance estimation unit are acquired. The acquisition unit is, for example, the STA position information acquisition unit 231. The determination unit determines the necessity of handover of the terminal station based on the information on the position of the terminal station estimated using the information on the direction and the information on the distance acquired by the acquisition unit and the information on the position of the access point. do. When the determination unit determines that a handover is necessary, the notification unit notifies the terminal station of information used for connection with the next connection destination access point via the access point to which the terminal station is connected. For example, the notification unit is a reconnection instruction unit 234.

The determination unit is based on the estimated terminal station position information, the terminal station movement information estimated using the estimated terminal station position information, and the access point position information. The necessity of handover of the station may be determined. The information regarding movement is, for example, motion information such as the movement speed and angular velocity of the terminal station. Further, the access point may further include a position information notification unit that acquires information on its own position and notifies the network control device of the acquired information on its own position. Further, at least a part of the plurality of access points may further include an acquisition unit, a determination unit, and a notification unit.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and includes designs and the like within a range that does not deviate from the gist of the present invention.

1, ... wireless communication system, 1a ... wireless communication system, 1b ... wireless communication system, 11 ... antenna, 12 ... wireless communication unit, 13 ... direction estimation unit, 14 ... distance estimation unit, 15 ... NWC interface unit, 16 ... AP Position information notification unit, 17 ... AP-to-AP interface unit, 18 ... Handover control function unit, 21 ... AP interface unit, 22 ... Storage unit, 23 ... Handover control determination unit, 40 ... Network, 71 ... Processor, 72 ... Storage unit, 73 ... Communication interface, 74 ... User interface, 181 ... Storage unit, 182 ... Handover control determination unit, 231 ... STA position information acquisition unit, 232 ... AP information acquisition unit, 233 ... Judgment unit, 234 ... Reconnection instruction unit, 1821 ... STA position information acquisition unit, 1822 ... AP information acquisition unit, 1823 ... judgment unit, 1824 ... reconnection instruction unit

Claims (7)

1. A wireless communication system having a network control device and a plurality of access points.
   The access point is
   A wireless communication unit that wirelessly communicates with a terminal station using a directional beam,
   A direction estimation unit that estimates the direction to the terminal station based on the beam information used by the wireless communication unit, and a direction estimation unit.
   It is provided with a distance estimation unit that estimates the distance to the terminal station based on the round-trip transmission time in wireless communication between the wireless communication unit and the terminal station.
   The network control device is
   An acquisition unit that acquires information on the direction estimated by the direction estimation unit and information on the distance estimated by the distance estimation unit.
   Based on the information on the position of the terminal station estimated by using the information on the direction and the information on the distance acquired by the acquisition unit and the information on the position of the access point, the necessity of handover of the terminal station is determined. Judgment unit and
   When the determination unit determines that a handover is necessary, the terminal station is notified of information used for connection with the access point of the next connection destination via the access point to which the terminal station is connected. Equipped with a notification unit,
   Wireless communication system.
2. The determination unit includes information on the estimated position of the terminal station, information on the movement of the terminal station estimated using the estimated information on the position of the terminal station, and information on the position of the access point. Determines the necessity of handover of the terminal station based on
   The wireless communication system according to claim 1.
3. The access point is
   It further includes a position information notification unit that acquires information on its own position and notifies the acquired information on the position to the network control device.
   The wireless communication system according to claim 1 or 2.
4. At least some of the access points mentioned above
   The acquisition unit, the determination unit, and the notification unit are further provided.
   The wireless communication system according to any one of claims 1 to 3.
5. Information on the direction to the terminal station estimated based on the information of the beam used for wireless communication with the terminal station by the access point that wirelessly communicates with the terminal station by the directional beam, and the access point is said to be said. An acquisition unit that acquires information on the distance to the terminal station estimated based on the round-trip transmission time in wireless communication with the terminal station.
   Based on the information on the position of the terminal station estimated by using the information on the direction and the information on the distance acquired by the acquisition unit and the information on the position of the access point, the necessity of handover of the terminal station is determined. Judgment unit and
   When the determination unit determines that a handover is necessary, the terminal station is notified of information used for connection with the access point of the next connection destination via the access point to which the terminal station is connected. Notification section and
   A network control device.
6. A network control method executed by a wireless communication system having a network control device and a plurality of access points.
   A direction estimation step in which the access point estimates the direction to the terminal station based on the information of the beam used in the wireless communication unit that wirelessly communicates with the terminal station by the beam having directivity.
   A distance estimation step in which the access point estimates the distance to the terminal station based on the round-trip transmission time in wireless communication between the wireless communication unit and the terminal station.
   An acquisition step in which the network control device acquires information on the direction estimated in the direction estimation step and information on the distance estimated in the distance estimation step.
   The terminal based on the information on the position of the terminal station estimated by the network control device using the information on the direction and the information on the distance acquired in the acquisition step and the information on the position of the access point. Judgment step to determine the necessity of handover of the station and
   When the network control device determines that a handover is necessary in the determination step, the information used for connecting to the access point of the next connection destination via the access point to which the terminal station is connected is input. The notification step to notify the terminal station and
   Network control method having.
7. Computer,
   The program for functioning as the network control device according to claim 5.

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