JP7260916B2 - Control device, control method and program - Google Patents

Description

The present invention relates to a control device, control method and program.

In recent years, LPWA (Low Power Wide Area) is becoming popular as a wireless communication system using the 920 MHz band. One of the communication standards belonging to LPWA is the IEEE802.11ah standard.

In the 920 MHz band used in the IEEE802.11ah standard, the radio law limits the cumulative time of data transmission within a unit time (hereinafter referred to as "cumulative transmission time") to a regulation value (360 seconds) or less. Therefore, when the cumulative time reaches the regulation value while the communication device is transmitting data, the data transmission is interrupted.

For this reason, Patent Document 1 proposes a wireless communication device that constructs a route in which the cumulative time of data transmission within a unit time does not exceed a predetermined value.

JP 2013-115755 A

For example, in a communication band, such as the 920 MHz band, in which the cumulative transmission time is limited to a regulation value or less for each communication channel, there is a demand for further improvement in technology that enables efficient data transmission.

For example, when wireless communication is being performed between a base station and a plurality of terminals in the communication band, the cumulative transmission time of a specific terminal among the plurality of terminals exceeds the regulation value in the communication channel being used. If it exceeds, it becomes necessary to change the communication channel of the specific terminal (hereinafter referred to as "channel change"). In this case, a problem arises that the base station and other terminals are forced to move unnecessary channels even if the cumulative transmission time of each terminal does not exceed the regulation value in the communication channel in use.

The present invention has been made in view of such problems, and its object is to efficiently transmit data in a communication band in which the cumulative time of data transmission within a unit time is limited for each communication channel. It is to provide a control device, a control method, and a program capable of performing the above.

In order to achieve the above object, a control device according to an aspect of the present invention uses a communication band that includes a plurality of communication channels and in which the cumulative time of data transmission within a unit time is restricted for each communication channel. A control device for controlling a first terminal that wirelessly communicates with a first base station using a first base station, wherein the first terminal transmits data to the first base station through a first communication channel within the unit time. an acquisition unit that acquires a first time that is the cumulative time transmitted to the base station, and if the first time acquired by the acquisition unit is equal to or greater than a threshold, within the unit time for each communication channel a determining unit for determining a roaming destination of the first terminal from among roaming destination candidates based on an accumulated time during which the first terminal has transmitted data to a roaming destination indicating the roaming destination determined by the determining unit and a notification unit that transmits a prior notification to the first terminal.

According to this aspect, when the first time is equal to or greater than the threshold, the determining unit selects roaming destination candidates based on the accumulated time during which the first terminal has transmitted data within the unit time for each communication channel. The roaming destination of the first terminal is determined from among them. The notification unit transmits a roaming destination notification indicating the determined roaming destination to the first terminal. As a result, for example, even if terminals other than the first terminal exist under the control of the first base station, only the first terminal for which the first time is equal to or greater than the threshold can be channel-shifted. This makes it possible to avoid wasteful channel movement of other terminals that do not require channel movement. As a result, data transmission by the first terminal can be efficiently performed.

For example, the roaming destination candidate includes a second base station that performs wireless communication on a second communication channel, and the determination unit determines that the unit If a second time, which is the cumulative time during which the first terminal has transmitted data on the second communication channel within the time, is less than the threshold, the second base station is transmitted to the first terminal. roaming destination.

According to this aspect, the determining unit determines, as the roaming destination of the first terminal, the second base station whose second time is less than the threshold. This makes it possible to appropriately determine the roaming destination of the first terminal.

For example, the roaming destination candidate further includes a third base station that performs wireless communication on a third communication channel, and the determining unit determines that, when the first time is equal to or greater than the threshold, The second time is less than the threshold, and a third time is less than the threshold, which is an accumulated time during which the first terminal transmits data over the third communication channel within the unit time. and, if the second time is shorter than the third time, the second base station, out of the second base station and the third base station that are the roaming destination candidates, It may be configured to be determined as the roaming destination of the first terminal.

According to this aspect, the determination unit determines the second base station with the shortest accumulated time as the roaming destination of the first terminal among the second base station and the third base station that are roaming destination candidates. . Accordingly, even when roaming destination candidates include a plurality of base stations, the roaming destination of the first terminal can be appropriately determined.

For example, if the first time period is equal to or greater than the threshold value and the second time period is equal to or greater than the threshold value, the decision unit determines whether the first communication channel is selected within the unit time. and the weighted average of the cumulative time during which the first base station and the first terminal under the control of the first base station each transmit data, and the second of the first base station and the second base station based on the result of comparison with the weighted average of the cumulative time during which the base station and the second terminal under the control of the second base station have transmitted data, respectively Any one of the base stations is determined as the roaming destination of the first terminal, and the notification unit selects either one of the first base station and the second base station determined as the roaming destination of the first terminal. may be configured to transmit a communication channel change notification instructing to change the communication channel.

According to this aspect, even if the second time is equal to or greater than the threshold, that is, even if there is no roaming destination candidate, the communication channel of either the first base station or the second base station is changed. By doing so, the first terminal can appropriately roam to either the first base station or the second base station that has changed the communication channel.

For example, when the determination unit determines the second base station as the roaming destination of the first terminal, the determination unit determines whether the second base station and the second base station are connected to each other through a fourth communication channel within the unit time. A weighted average of the cumulative time during which each terminal transmits data, and a weighted average of the cumulative time during which the second base station and the second terminal transmit data through a fifth communication channel within the unit time. A change destination of the communication channel of the second base station may be determined to be either the fourth communication channel or the fifth communication channel based on the comparison result.

According to this aspect, it is possible to appropriately determine the change destination of the communication channel of the second base station to either the fourth communication channel or the fifth communication channel.

Further, a control method according to an aspect of the present invention uses a communication band that includes a plurality of communication channels and in which the cumulative time of data transmission within a unit time is limited for each communication channel, a base station and A control method for controlling a terminal that performs wireless communication, comprising: acquiring an accumulated time during which the terminal transmits data to the base station through a specific communication channel within the unit time; determining a roaming destination of the terminal from among roaming destination candidates based on the accumulated time during which the terminal has transmitted data within the unit time for each communication channel when the time is equal to or greater than a threshold; and sending a roaming destination notification to the terminal indicating the roaming destination that has been established.

According to this aspect, when the cumulative time is equal to or greater than the threshold, the roaming destination of the terminal is determined from among the roaming destination candidates based on the cumulative time during which the terminal has transmitted data within the unit time for each communication channel. . Also, a roaming destination notification indicating the determined roaming destination is transmitted to the terminal. As a result, for example, even if there are terminals other than the terminals under the control of the base station, only the terminals whose cumulative time is equal to or greater than the threshold can be channel-shifted, and channel movement is unnecessary. terminals can be avoided from moving channels unnecessarily. As a result, data transmission by the terminal can be efficiently performed.

A program according to an aspect of the present invention is a program for causing a computer to execute the control method described above.

The present invention can be realized not only as an apparatus, but also as a method in which processing means constituting the apparatus are used as steps, as a program for causing a computer to execute the steps, or as a computer-readable program in which the program is recorded. It can also be implemented as a recording medium such as a CD-ROM, or as information, data, or signals indicating the program. These programs, information, data and signals may then be distributed over a communication network such as the Internet.

According to the control device and the like according to one aspect of the present invention, it is possible to efficiently transmit data in a communication band in which the cumulative time of data transmission within a unit time is limited for each communication channel.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the outline|summary of the communication system which concerns on embodiment. It is a block diagram which shows the functional structure of the control apparatus which concerns on embodiment. It is a figure which shows an example of the table which records transmission time. FIG. 4 is a sequence diagram showing the operation of the communication system according to the embodiment when there are roaming destination candidates; FIG. 5 is a diagram for explaining the process of step S105 in the sequence diagram of FIG. 4; FIG. FIG. 4 is a diagram showing an example of a beacon frame transmitted from the control device according to the embodiment to the base station; FIG. 10 is a diagram showing an example of a Vendor Specific Action frame having information indicating a roaming destination notification transmitted from the control device according to the embodiment to the base station; FIG. 5 is a diagram for explaining the process of step S107 in the sequence diagram of FIG. 4; FIG. FIG. 4 is a diagram for explaining the operation of the communication system according to the embodiment when there are no roaming destination candidates; FIG. 4 is a sequence diagram showing the operation of the communication system according to the embodiment when there are no roaming destination candidates; FIG. 10 is a diagram for explaining the process of step S205 in the sequence diagram of FIG. 9; FIG. FIG. 10 is a diagram for explaining the process of step S206 in the sequence diagram of FIG. 9; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the embodiments described below are all comprehensive or specific examples. Numerical values, shapes, materials, components, arrangement positions and connection forms of components, steps, order of steps, and the like shown in the following embodiments are examples and are not intended to limit the present invention. Further, among the constituent elements in the following embodiments, constituent elements not described in independent claims will be described as optional constituent elements.

(Embodiment)
[1-1. Overview of communication system]
First, an overview of a communication system 2 according to an embodiment will be described with reference to FIG. FIG. 1 is a diagram showing an overview of a communication system 2 according to an embodiment.

As shown in FIG. 1, the communication system 2 includes base stations AP1, AP2, AP3, terminals STA1, STA2, STA3, STA4, and a control device 4. FIG.

A base station AP1 and terminals STA3 and STA4 under its control constitute a BSS (Basic Service Set) 1 that performs radio communication on a channel 1 . Channel 1 is a communication channel for wireless communication. Wireless communication between the base station AP1 and the terminals STA3 and STA4 is established by a wireless LAN (Local Area Network) conforming to the IEEE802.11ah standard. That is, the radio communication between the base station AP1 and the terminals STA3 and STA4 is performed in a communication band including a plurality of communication channels, and the accumulated time for transmitting data (communication frames) within a unit time is limited for each communication channel. communication band, for example, the 920 MHz band.

Here, in wireless communication in the 920 MHz band, the cumulative time (hereinafter also referred to as "cumulative transmission time") during which one communication device transmits data in one communication channel within a unit time is less than or equal to the regulation value (360 seconds). is limited to In other words, when the cumulative time of one communication device transmitting data in one communication channel in the most recent one-hour period reaches 360 seconds, the communication device cannot transmit data in that period. become unable. In this case, the communication device can transmit data on other communication channels other than the communication channel whose cumulative transmission time has reached 360 seconds in the most recent one-hour period.

The base station AP1 is an access point in the wireless LAN and relays communication between the terminals STA3 and STA4 and other networks. The base station AP1 performs radio communication with the terminals STA3 and STA4. Also, the base station AP1 performs wired or wireless communication with other networks. Other networks are, for example, local area networks such as offices and factories, or the Internet.

Terminals STA3 and STA4 are stations in the wireless LAN, and perform wireless communication with the base station AP1. The terminals STA3 and STA4 can communicate with other networks or with the base station AP1 using relay by the base station AP1.

A base station AP2 and terminals STA1 and STA2 under its control constitute a BSS2 that performs wireless communication on channel 2. FIG. Channel 2 is a communication channel different from channel 1 for wireless communication. Wireless communication between the base station AP2 and the terminals STA1 and STA2 is established by a wireless LAN complying with the IEEE802.11ah standard, as described above. That is, radio communication between the base station AP2 and the terminals STA1 and STA2 is performed in the above-described 920 MHz band, for example.

The base station AP2 is an access point in the wireless LAN and relays communication between the terminals STA1 and STA2 and other networks. The base station AP2 performs radio communication with the terminals STA1 and STA2. Also, the base station AP2 performs wired or wireless communication with other networks.

Terminals STA1 and STA2 are stations in a wireless LAN, and perform wireless communication with a base station AP2. The terminals STA1 and STA2 can communicate with other networks or communicate with the base station AP2 using the relay by the base station AP2.

A base station AP3 and a terminal (not shown) under its control constitute a BSS3 that performs wireless communication on channel 3. FIG. Channel 3 is a communication channel different from channels 1 and 2 for wireless communication. Wireless communication between the base station AP3 and the terminal is constructed by a wireless LAN conforming to the IEEE802.11ah standard, as described above. That is, wireless communication between the base station AP3 and the terminal is performed, for example, in the 920 MHz band described above.

The base station AP3 is an access point in the wireless LAN and relays communication between the terminal and other networks. The base station AP3 performs wireless communication with terminals. Also, the base station AP3 performs wired or wireless communication with other networks.

Here, in the communication system 2 according to the present embodiment, the base stations AP1, AP2, and AP3 are installed at a certain distance from each other, and at least the adjacent base stations (for example, the base station AP2) , base stations AP1 and AP3) are installed such that their radio coverage areas largely overlap each other. In other words, a certain base station is installed within a range capable of wireless communication with terminals under the control of adjacent base stations. More specifically, the base station AP1 is installed so as to be able to wirelessly communicate with the terminal STA1 under the control of the adjacent base station AP2.

The control device 4 communicates with the base stations AP1, AP2, AP3 via wired LAN cables or wireless communication. The control device 4 controls the terminals STA3 and STA4 that wirelessly communicate with the base station AP1, and controls the terminals STA1 and STA2 that wirelessly communicate with the base station AP2. Here, considering that the controller 4 communicates with and controls each of the base stations AP1, AP2, and AP3, wire communication is more preferable. An example will be described in which the control device 4 according to the present embodiment performs wired communication with the base stations AP1, AP2, and AP3 via wired LAN cables. A functional configuration of the control device 4 will be described later.

[1-2. Functional configuration of control device]
Next, the functional configuration of the control device 4 will be described with reference to FIGS. 2 and 3. FIG. FIG. 2 is a block diagram showing the functional configuration of the control device 4 according to the embodiment. FIG. 3 shows an example of a table 14 for recording transmission times.

As shown in FIG. 2 , the control device 4 includes a communication IF (interface) 6 , an acquisition section 8 , a determination section 10 and a notification section 12 . The acquisition unit 8, the determination unit 10, and the notification unit 12 are realized by, for example, a processor reading out and executing a software program recorded in a memory.

A communication interface 6 is a communication interface that performs wired communication with the base stations AP1, AP2, and AP3.

The acquiring unit 8 acquires the cumulative transmission times of the base stations AP1, AP2, AP3 and the terminals STA1, STA2, STA3, STA4 for each communication channel via the communication IF6. Specifically, the acquisition unit 8 calculates the accumulated time during which each of the base stations AP1, AP2, and AP3 and the terminals STA1, STA2, STA3, and STA4 has transmitted data within a unit time (the most recent hour) for each communication channel. get. The acquiring unit 8 associates the acquired cumulative transmission times of the base stations AP1, AP2, AP3 and the terminals STA1, STA2, STA3, STA4 with the communication channels and stores them in the memory.

For example, the acquisition unit 8 acquires the accumulated transmission time "100 milliseconds" of the base station AP1, the accumulated transmission time "50 milliseconds" of the terminal STA3, and the accumulated transmission time "80 milliseconds" of the terminal STA4 into the communication channel " channel 1" and stored. Further, for example, the acquisition unit 8 acquires the accumulated transmission time of “180 milliseconds” of the base station AP2, the accumulated transmission time of “45 milliseconds” of the terminal STA1, and the accumulated transmission time of “90 milliseconds” of the terminal STA2. It is stored in association with "channel 2". Further, for example, the acquisition unit 8 stores the accumulated transmission time “200 milliseconds” of the base station AP3 in association with the communication channel “channel 3”.

Here, an example of a method of acquiring the accumulated transmission time of the terminal STA1 by the acquiring unit 8 will be described. The acquisition unit 8 acquires the cumulative transmission time of the terminal STA1 on the channel 2, for example, using the table 14 shown in FIG. Table 14 is a data table for dividing one hour, ie, 3600 seconds into time intervals of, for example, 100 milliseconds, and recording the transmission time of terminal STA1 in each time interval. In this case, there are 36000 time intervals. One entry in table 14 corresponds to one time interval. Note that the delimiting time intervals of the time sections in the table 14 may be set in advance at the time of shipment from the factory, or may be appropriately set by the user specifying them at the time of use.

In table 14 each entry has a number 16 and a transmission time 18 . Number 16 is the serial number of each entry. The transmission time 18 is the transmission time of the terminal STA1 in the time interval corresponding to each entry. The transmission time 18 is, for example, the transmission time expressed in milliseconds. The transmission time 18 is the minimum value "0" when no data is transmitted during the time interval corresponding to the entry, and the maximum value when data is transmitted during the entire time interval corresponding to the entry. The value becomes "100".

As an example, the time interval corresponding to the entry whose number 16 is "1" in FIG. In the time interval shown, terminal STA1 has transmitted for 45 milliseconds.

The acquisition unit 8 constantly monitors the transmission of the terminal STA1, and acquires the transmission time of the terminal STA1 for each time interval of 100 milliseconds. Note that the transmission time 18 also includes the time required for data retransmission.

Then, the acquiring unit 8 records the acquired transmission time as the transmission time 18 of the entry of the number 16 corresponding to the time interval while incrementing the number 16 by "1" for each time interval. Immediately after recording the transmission time in the entry whose number 16 is "36000", the transmission time is overwritten and recorded in the entry whose number 16 is "1". In this manner, the table 14 records the transmission time in each time interval within the past hour as a ring buffer. As a result, since the table 14 always records the transmission time in each time interval for the most recent one hour, the acquisition unit 8 calculates the total of the transmission times 18 in the numbers "1" to "36000". , it is possible to acquire the cumulative transmission time of the terminal STA1 in the most recent hour.

Note that the acquisition unit 8, in the same manner as the method of calculating the cumulative transmission time in channel 2 of terminal STA1 using table 14 described above, calculates A cumulative transmission time can be calculated. The cumulative transmission time in each channel in this case is managed using a table generated for each channel.

Returning to FIG. 2, when the cumulative transmission time of a specific terminal out of terminals STA1, STA2, STA3, and STA4 is equal to or greater than a threshold, determining section 10 selects the roaming destination of the specific terminal from among the roaming destination candidates. decide. The threshold may be, for example, 95% of the cumulative transmission time regulation value (360 seconds), that is, 342 seconds. For example, if the specific terminal is the terminal STA1, the roaming destination candidates are the base stations AP1 and AP3 belonging to BSS1 and BSS3, respectively, other than the BSS2 to which the terminal STA1 belongs. A method of determining the roaming destination by the determining unit 10 will be described later.

The notification unit 12 transmits a roaming destination notification indicating the roaming destination determined by the determination unit 10 to the specific terminal via the communication IF 6 .

[1-3. Operation of communication system]
[1-3-1. If roaming destination candidates exist]
Next, the operation of the communication system 2 according to the embodiment when there are roaming destination candidates will be described with reference to FIGS. 1 and 4 to 7. FIG. FIG. 4 is a sequence diagram showing the operation of the communication system 2 according to the embodiment when there are roaming destination candidates. FIG. 5 is a diagram for explaining the process of step S105 in the sequence diagram of FIG. 4 (the process of determining the roaming destination of terminal STA1). FIG. 6A is a diagram showing an example of a beacon frame transmitted from the control device 4 to the base station according to the embodiment. FIG. 6B is a diagram showing an example of a Vendor Specific Action frame having information indicating a roaming destination notification transmitted from the control device 4 to the base station according to the embodiment. FIG. 7 is a diagram for explaining the process of step S107 (the process of executing roaming) in the sequence diagram of FIG.

Based on the configuration of the communication system 2 shown in FIG. 1, the operation of the communication system 2 when the accumulated transmission time of the terminal STA1 (an example of the first terminal) on the channel 2 exceeds the threshold will be described below. For convenience of explanation, FIG. 4 only shows the operations of the control device 4, the base station AP1 (an example of the second base station), the base station AP2 (an example of the first base station), and the terminal STA1. The operations of the base station AP3 (an example of a third base station), terminal STA2 (an example of a second terminal), terminal STA3, and terminal STA4 are omitted from the drawing.

As shown in FIG. 4, first, a wireless communication connection is established between the base station AP2 and the terminal STA1 in the BSS2 (S101). As a result, the base station AP2 and the terminal STA1 are ready for wireless communication via channel 2. FIG. Although not shown, in BSS1, a wireless communication connection is established between the base station AP1 and the terminals STA3 and STA4, and in BSS2, a wireless communication connection is established between the base station AP2 and the terminal STA2. shall be established.

The acquisition unit 8 of the control device 4 acquires each cumulative transmission time of the base stations AP1, AP2, AP3 and the terminals STA1, STA2, STA3, STA4 for each communication channel (S102). The determining unit 10 of the control device 4 determines whether or not each cumulative transmission time acquired by the acquiring unit 8 is equal to or greater than a threshold for each communication channel (S103). If each cumulative transmission time is less than the threshold (NO in S103), the process returns to step S102 described above.

If the accumulated transmission time (example of first time) of terminal STA1 on channel 2 (example of first communication channel) is equal to or greater than the threshold (YES in S103), channel 1 (example of first communication channel) other than channel 2 ( Based on the accumulated transmission time of terminal STA1 in channel 3 (an example of a second communication channel) and channel 3 (an example of a third communication channel), it is determined whether there are roaming destination candidates (that is, whether base stations AP1 and AP2 are roaming). (whether or not it can be a first candidate). If at least one of the cumulative transmission time of terminal STA1 on channel 1 (example of second time) and the cumulative transmission time of terminal STA1 on channel 3 (example of third time) is less than the threshold, control The determining unit 10 of the device 4 determines that there is a roaming destination candidate (S104).

A case will be described below where both the accumulated transmission time of the terminal STA1 on channel 1 and the accumulated transmission time of the terminal STA1 on channel 3 are less than the threshold, that is, the roaming destination candidates are the base stations AP1 and AP3. The determining unit 10 of the control device 4 selects the base station (for example, the base station AP1) belonging to the communication channel with the shortest cumulative transmission time of the terminal STA1 from among the base stations AP1 and AP3 which are roaming destination candidates. It is determined as the first (S105).

Here, an example of a method for determining the roaming destination of the terminal STA1 by the determination unit 10 of the control device 4 will be described with reference to FIG. In the table shown in FIG. 5, based on the cumulative transmission times of the base stations AP1, AP2, AP3 and the terminals STA1, STA2, STA3, STA4 acquired by the acquisition unit 8 using the table 14, each "Actual cumulative transmission time/regulation value of cumulative transmission time" of the base station and each terminal is displayed in percentage. The regulation value for cumulative transmission time is 360 seconds. In addition, hereinafter, a numerical value expressed as a percentage of "actual cumulative transmission time/regulation value of cumulative transmission time" of each base station and each terminal is also referred to as "accumulated transmission time ratio".

For example, at the base station AP1 on channel 1, "40%" is displayed. This indicates that the cumulative transmission time during which the base station AP1 has transmitted data on channel 1 within a unit time is 144 seconds (=360 seconds×40%). Also, for example, for terminal STA1 on channel 2, "95%" is displayed. This indicates that the cumulative transmission time during which terminal STA1 has transmitted data on channel 2 within a unit time is 342 seconds (=360 seconds×95%). Note that "10%" is displayed for the terminal STA1 on channel 1. This means that when the terminal STA1 belongs to the BSS1 within a unit time, the cumulative transmission time during which the terminal STA1 transmits data on channel 1 within the unit time is 36 seconds (=360 seconds × 10%). is shown.

When the cumulative transmission time of the terminal STA1 on channel 2 is equal to or greater than the threshold (342 seconds), the determining unit 10 of the control device 4 selects the roaming destination candidate base stations AP1 and AP3 with the shortest cumulative transmission time. A base station belonging to the communication channel is determined as the roaming destination of the terminal STA1.

In the example shown in FIG. 5, the accumulated transmission time of terminal STA1 on channel 1 is 36 seconds (=360 seconds×10%). Also, the cumulative transmission time of terminal STA1 on channel 3 is 252 seconds (=360 seconds×70%). Therefore, the determination unit 10 of the control device 4 determines the base station AP1 belonging to the channel 1 with the shortest cumulative transmission time of the terminal STA1 as the roaming destination of the terminal STA1 from among the base stations AP1 and AP3 which are roaming destination candidates. do.

Here, for example, in FIG. 5, the cumulative transmission time rate of base station AP3 on channel 3 is lower than the cumulative transmission time rate of base station AP1 on channel 1, and the cumulative transmission time rate of terminal STA1 on channel 1 is channel 3, the base station AP3 may be determined as the roaming destination of the terminal STA1. By doing so, since the cumulative transmission time of each base station is more likely to reach the threshold than the cumulative transmission time of each terminal, a base station with the shortest possible cumulative transmission time is determined as a roaming destination, thereby improving the communication system. 2 can maintain wireless communication between the terminal and the base station for a long time after roaming.

Returning to FIG. 4, the notification unit 12 of the control device 4 transmits a roaming destination notification indicating the roaming destination determined by the determination unit 10 to the terminal STA1 via the base station AP2 via the communication IF 6 (S106). The roaming destination notification includes at least information indicating the MAC (Media Access Control) address of the roaming terminal STA1 and information indicating the MAC address of the roaming destination base station AP1. Furthermore, the roaming destination notification includes information indicating the communication channel (channel 1) in which the roaming destination base station AP1 is operating, thereby shortening the scanning time for roaming.

Here, an example of a method of transmitting a roaming destination notification by the notification unit 12 of the control device 4 will be described with reference to FIGS. 6A and 6B.

In the example shown in FIG. 6A, the notification unit 12 of the control device 4 uses the Vendor-specific IE of the Beacon frame transmitted by the base station at regular time intervals to cause the base station to transmit the roaming destination notification. Specifically, the notification unit 12 of the control device 4 uses the IEEE Std. Add the Vendor Specific element (IEEE Std.802.11-2012 8.4.2.28) shown in FIG. 6A to the end of the Frame Body in 802.11-2012 (8.3.3.2), Information indicating the notification of the roaming destination is embedded in the specific Content and transmitted to the terminal via the base station. Element ID uses 221 indicating that it is a Vendor Specific element. A plurality of Vendor Specific elements may exist in one frame. However, the maximum number of elements is limited only by the maximum length of the frame. This method can be used even when a connection between the base station and the terminal has not been established.

In the example shown in FIG. 6B, the notification unit 12 of the control device 4 uses IEEE Std. It uses the Vendor Specific Action frame defined in 802.11-2012 (8.5.6) to send roaming destination advertisements. Specifically, the notification unit 12 of the control device 4 embeds information indicating the roaming destination notification in the Vendor-Specific Content in the action field format of the Vendor Specific Action frame shown in FIG. 6B, and transmits the information to the terminal via the base station. do. In addition, Category uses 126 or 127. This method can only be used in situations where a connection has been established between the base station and the terminal.

In addition to the transmission method described above, for example, information indicating the roaming destination notification may be included in the payload of the data frame. In this method, it is necessary to install an application for analyzing the roaming destination notification and executing roaming on the terminal side. Also, this method can only be used in situations where a connection has been established between the base station and the terminal.

Returning to FIG. 4, terminal STA1 executes roaming based on the roaming destination notification from control device 4 (S107). As a result, the wireless communication connection is disconnected between the base station AP2 and the terminal STA1 in the BSS2 (S108), and the wireless communication connection is established between the base station AP1 and the terminal STA1 in the BSS1 (S109). As a result, as shown in FIG. 7, terminal STA1 roams to base station AP1 and becomes subordinate to base station AP1 in BSS1. As a result, the base station AP1 and the terminal STA1 are in a state of being able to communicate wirelessly on the channel 1, and the time until the accumulated transmission time of the terminal STA1 reaches the regulation value can be extended.

[1-3-2. If there are no roaming destination candidates]
Next, the operation of the communication system 2 according to the embodiment when there are no roaming destination candidates will be described with reference to FIGS. 8 to 11. FIG. FIG. 8 is a diagram for explaining the operation of the communication system 2 according to the embodiment when there are no roaming destination candidates. FIG. 9 is a sequence diagram showing the operation of the communication system 2 according to the embodiment when there are no roaming destination candidates. FIG. 10 is a diagram for explaining the process of step S205 in the sequence diagram of FIG. FIG. 11 is a diagram for explaining the process of step S206 in the sequence diagram of FIG.

Based on the configuration of the communication system 2 shown in FIG. 8(a), the operation of the communication system 2 when the accumulated transmission time of the terminal STA1 on the channel 2 is equal to or greater than the threshold will be described below. As shown in FIG. 8(a), the communication system 2 does not include the base station AP3 described above. For convenience of explanation, FIG. 9 shows only the operations of the base stations AP1 and AP2 and the terminals STA1, STA3 and STA4, and omits the operations of the base station AP3 and the terminal STA2.

As shown in FIG. 9, first, a wireless communication connection is established between the base station AP2 and the terminal STA1 in the BSS2 (S201). As a result, the base station AP2 and the terminal STA1 are ready for wireless communication on channel 2. FIG. Although not shown, a wireless communication connection is established between the base station AP1 and the terminals STA3 and STA4 in BSS1, and a wireless communication connection is established between the base station AP2 and terminal STA2 in BSS2. shall be established.

The acquisition unit 8 of the control device 4 acquires each cumulative transmission time of the base stations AP1, AP2 and the terminals STA1, STA2, STA3, STA4 for each communication channel (S202). The determining unit 10 of the control device 4 determines whether or not each cumulative transmission time acquired by the acquiring unit 8 is equal to or greater than a threshold for each communication channel (S203). If each accumulated transmission time is less than the threshold (NO in S203), the process returns to step S202 described above.

When the cumulative transmission time of terminal STA1 on channel 2 is equal to or greater than the threshold (YES in S203), the determining unit 10 of control device 4 determines the cumulative transmission time of terminal STA1 on channel 1 other than channel 2. to determine whether or not a roaming destination candidate exists (that is, whether or not the base station AP1 can be a roaming destination candidate). In this example, the determining unit 10 of the control device 4 determines that there are no roaming destination candidates (S204).

Since the terminal STA1 cannot roam in this state, the determination unit 10 of the control device 4 determines the BSS whose communication channel is to be changed from among the BSS1 and BSS2 (S205).

Here, an example of a method of determining a BSS for changing a communication channel by the determination unit 10 of the control device 4 will be described with reference to FIG. In the table shown in FIG. 10, as in FIG. 5, the "actual cumulative transmission time/regulation value of cumulative transmission time" of each base station and each terminal is displayed in percentage for each communication channel. The regulation value for cumulative transmission time is 360 seconds.

In the example shown in FIG. 10, for terminal STA1 on channel 1, "95%" is displayed. This indicates that the cumulative transmission time during which terminal STA1 has transmitted data on channel 1 within a unit time is 342 seconds, reaching the threshold. Also, for example, for terminal STA1 on channel 2, "95%" is displayed. This indicates that the accumulated transmission time during which the terminal STA1 has transmitted data on the channel 2 within the unit time is also 342 seconds and has reached the threshold.

The determining unit 10 of the control device 4 calculates the weighted average of the cumulative transmission time ratios of the base station AP1 and the terminals STA3 and STA4 belonging to the BSS1, and calculates the cumulative transmission time of the base station AP2 and the terminals STA1 and STA2 belonging to the BSS2. A weighted average of the rates is calculated, and the BSS with the largest calculated weighted average is determined as the BSS for changing the communication channel. As described above, the "accumulated transmission time rate" is a numerical value representing the "actual accumulated transmission time/regulation value of accumulated transmission time" of each base station and each terminal as a percentage. Since the "regulation value of time" is a fixed value, the "weighted average of the cumulative transmission time rate" is substantially synonymous with the "weighted average of the cumulative transmission time".

Here, an example of a method for calculating the weighted average of each cumulative transmission time rate will be described. Terminals STA _ij (j=1, 2, . . . , n _STA ) exist under the control of base stations AP _i (i=1 _, 2, . . . , n _AP ). Let the number of stations be n _AP . Let w _i and w _ij be the weights of the base station AP _i and the terminal STA _ij respectively, and let R _i and R _ij be the cumulative transmission time ratios of the base station AP _i and the terminal STA _ij in the most recent hour. A weighted average R _BSSi of each accumulated transmission time ratio of the base station AP and the terminal STA belonging to the BSS is calculated by the following equation (1).

The determination unit 10 of the control device 4 determines the BSS with the largest weighted average R _BSSi calculated as described above as the target BSS for changing the communication channel. In the example shown in FIG. 10, the weighted average of the cumulative transmission time ratios of the base station AP1 and terminals STA3 and STA4 belonging to BSS1 is (80×5+60×1+40×1)/(5+1+1)=71%. On the other hand, the weighted average of the cumulative transmission time ratios of the base station AP2 and terminals STA1 and STA2 belonging to BSS2 is (40×5+95×1+80×1)/(5+1+1)=54%. In calculating this weighted average, each weight of the base stations AP1 and AP2 is set to "5", and each weight of the terminals STA1, STA2, STA3 and STA4 is set to "1". As a result, the determining unit 10 of the control device 4 determines the BSS1 having the largest weighted average as the target BSS for changing the communication channel.

Returning to FIG. 9, the determination unit 10 of the control device 4 determines the change destination of the communication channel of BSS1 (S206). Here, an example of a method of determining the change destination of the communication channel of BSS1 by the determination unit 10 of the control device 4 will be described with reference to FIG. In the table shown in FIG. 11, as in FIG. 5, the "actual cumulative transmission time/regulation value of cumulative transmission time" of each base station and each terminal is displayed in percentage for each communication channel. The regulation value for cumulative transmission time is 360 seconds.

Next, the determining unit 10 of the control device 4 selects channel 3 (an example of a fourth channel) and channel 4 (an example of a fifth channel) as candidates for changing the communication channel of the BSS1. Then, as shown in FIG. 11, the determining unit 10 of the control device 4 determines the cumulative transmission time rates of the base station AP1 and the terminals STA3 and STA4 belonging to the BSS1 for which the communication channel is to be changed in each of the channels 3 and 4. Calculate the weighted average. Specifically, the determining unit 10 of the control device 4 calculates the weighted average of the cumulative transmission time ratios of the base station AP1 and the terminals STA3 and STA4 on the channel 3, and , and the communication channel with the smallest calculated weighted average is determined as the change destination of the communication channel of BSS1. The method of calculating the weighted average is the same as described above, so the explanation thereof is omitted.

In the example shown in FIG. 11, the weighted average of the cumulative transmission time ratios of the base station AP1 and terminals STA3 and STA4 on channel 3 is (5×5+0×1+5×1)/(5+1+1)=4.3%. On the other hand, the weighted average of the cumulative transmission time ratios of the base station AP1 and terminals STA3 and STA4 on channel 4 is (25×5+10×1+0×1)/(5+1+1)=19%. In calculating this weighted average, the weight of the base station AP1 is set to "5", and the weight of each of the terminals STA3 and STA4 is set to "1". The determining unit 10 of the control device 4 determines the channel 3 with the smallest weighted average as the communication channel change destination of the BSS1. As a result, it is possible to appropriately change the communication channel of BSS1, for which the accumulated transmission time of the base station or terminal is highly likely to exceed the threshold value in the near future.

Returning to FIG. 9, the notification unit 12 of the control device 4 transmits a communication channel change notification instructing to change the communication channel to channel 3 to the base station AP1 belonging to the BSS1 whose communication channel is to be changed (S207). ). Note that the communication channel change notification may be a communication frame including at least information indicating the communication channel to be changed.

The base station AP1 receives the communication channel change notification from the control device 4, and transfers the received communication channel change notification to the terminals STA3 and STA4 under the control of the base station AP1. As a result, as shown in FIG. 8(b), the base station AP1 and terminals STA3 and STA4 change the communication channel from channel 1 to channel 3 based on the communication channel change notification.

The decision unit 10 of the control device 4 decides the base station AP1 whose communication channel has been changed as the roaming destination of the terminal STA1. The notification unit 12 of the control device 4 transmits a roaming destination notification indicating the roaming destination determined by the determination unit 10 to the terminal STA1 via the base station AP2 via the communication IF 6 (S211).

Terminal STA1 executes roaming based on the roaming destination notification from control device 4 (S212). As a result, the wireless communication connection is disconnected between the base station AP2 and the terminal STA1 in BSS2 (S213), and the wireless communication connection is established between the base station AP1 and terminal STA1 in BSS1 (S214). As a result, terminal STA1 roams to base station AP1 and becomes subordinate to base station AP1 in BSS1, as shown in FIG. 8(c). As a result, the base station AP1 and the terminal STA1 are ready for wireless communication via channel 3. FIG.

[1-4. effect]
As described above, the determination unit 10 of the control device 4 selects a specific terminal from among the roaming destination candidates when the cumulative transmission time of a specific terminal among the terminals STA1, STA2, STA3, and STA4 is equal to or greater than the threshold. Decide where to roam. The notification unit 12 transmits a roaming destination notification indicating the determined roaming destination to a specific terminal.

As a result, for example, even if there are terminals other than the specific terminal under the control of the base station, only the specific terminal whose cumulative transmission time is equal to or greater than the threshold can be channel-shifted. It is possible to avoid wasteful channel movement by other unnecessary terminals. As a result, it is possible to efficiently transmit data by a specific terminal.

(other modifications, etc.)
Although the control device of the present invention has been described above based on the above embodiment, the present invention is not limited to the above embodiment. The present invention also includes a form obtained by modifying the above-described embodiment conceived by a person skilled in the art, and another form realized by arbitrarily combining the constituent elements of the above-described embodiment.

In the above embodiment, the controller 4 is provided outside the base stations AP1, AP2 and AP3, but the present invention is not limited to this. good too. In this case, each of the base stations AP1, AP2, AP3 functions as a controller.

In the above embodiments, each component may be implemented by dedicated hardware or by executing a software program suitable for each component. Each component may be implemented by a program execution unit such as a CPU or processor reading and executing a software program recorded in a recording medium such as a hard disk or semiconductor memory.

INDUSTRIAL APPLICABILITY The present invention can be applied, for example, to a control device or the like that controls a terminal that performs wireless communication with a base station using a communication band in which the cumulative transmission time is limited for each communication channel.

2 communication system 4 control device 6 communication IF
8 acquisition unit 10 determination unit 12 notification unit 14 table 16 number 18 transmission time AP1, AP2, AP3 base station STA1, STA2, STA3, STA4 terminal

Claims (7)

Controls a first terminal that performs wireless communication with a first base station using a communication band that includes a plurality of communication channels and that limits the cumulative time of data transmission within a unit time for each communication channel. A control device for
an acquisition unit that acquires a first time that is an accumulated time during which the first terminal transmits data to the first base station over a first communication channel within the unit time;
When the first time acquired by the acquisition unit is equal to or greater than a threshold, roaming destination candidates are determined based on the accumulated time during which the first terminal has transmitted data within the unit time for each communication channel. a determination unit that determines a roaming destination of the first terminal from among;
a notification unit configured to transmit, to the first terminal, a roaming destination notification indicating the roaming destination determined by the determination unit. the roaming destination candidate includes a second base station that performs wireless communication on a second communication channel;
The determining unit determines a second time period, which is a cumulative time during which the first terminal transmits data over the second communication channel within the unit time, when the first time period is equal to or greater than the threshold value. is less than the threshold, determining the second base station as the roaming destination of the first terminal. the roaming destination candidate further includes a third base station that performs wireless communication on a third communication channel;
The determining unit determines that, when the first time is equal to or greater than the threshold, the second time is less than the threshold, and the third communication channel is used within the unit time. When a third time that is an accumulated time during which one terminal has transmitted data is less than the threshold and the second time is shorter than the third time, the roaming destination candidate The control device according to claim 2, wherein, of the second base station and the third base station, the second base station is determined as the roaming destination of the first terminal. When the first time period is equal to or greater than the threshold value and the second time period is equal to or greater than the threshold value, the determining unit performs the A weighted average of cumulative times during which data is transmitted by a first base station and the first terminal under the control of the first base station, and the second base station through the second communication channel within the unit time either the first base station or the second base station based on the result of comparison with the weighted average of the accumulated time during which the station and the second terminal under the control of the second base station respectively transmit data determining one as the roaming destination of the first terminal;
The notification unit is configured to change a communication channel by instructing either one of the first base station and the second base station determined as a roaming destination of the first terminal to change a communication channel. 3. The control device of claim 2, which transmits a notification. When the determination unit determines the second base station as a roaming destination of the first terminal, the determination unit determines whether the second base station and the second terminal are connected via a fourth communication channel within the unit time. A weighted average of the cumulative time of data transmission and the weighted average of the cumulative time of data transmission by the second base station and the second terminal through a fifth communication channel within the unit time. 5. The control device according to claim 4, wherein the change destination of the communication channel of the second base station is determined to be either the fourth communication channel or the fifth communication channel based on the above. A control method for controlling a terminal that performs wireless communication with a base station using a communication band that includes a plurality of communication channels and in which the cumulative time of data transmission within a unit time is limited for each communication channel. There is
obtaining a cumulative time during which the terminal transmits data to the base station on a specific communication channel within the unit time;
When the acquired cumulative time is equal to or greater than a threshold, the roaming destination of the terminal is determined from roaming destination candidates based on the cumulative time during which the terminal has transmitted data within the unit time for each communication channel. and
transmitting a roaming destination notification indicating the determined roaming destination to the terminal. A program for causing a computer to execute the control method according to claim 6.

Images