Description Title of Invention: WIRELESS COMMUNICATION APPARATUS, WIRELESS COMMUNICATION DEVICE, WIRELESS COMMUNICATION METHOD, AND WIRELESS COMMUNICATION PROGRAM Technical Field [0001] The present invention relates to wireless communication.
The present invention relates, for example, to wireless communication in an industrial network. Background Art
[0002] As described in Non-Patent Literature 1 below, in a network called a field network included in the industrial network, one master device and a plurality of slave devices are connected.
For example, the master device is a controller and the slave devices are various I/O (Input/Output) devices or measuring devices.
Then, between the master device and the plurality of slave devices, cyclic communication is performed at predetermined time intervals.
[0003] Meanwhile, in order to reduce a cost of laying wired networks, wirelessization of networks is required.
It is inconvenient in terms of usability, if wirelessization of networks is made using a special apparatus or a frequency that requires a license.
Thus, it is possible to reduce a procurement cost or development cost of hardware by implementing wirelessization of networks according to existing wireless LAN standards (Non-Patent Literature 2).
[0004] In the industrial network, constant periodicity is required. Also, the master device is required to connect with the plurality of slave devices.

Therefore, schedule management for preventing collision in wireless sections is required.
With respect to the wireless LAN standards, a HCCA (Hybrid Coordination Function Controlled Channel Access) method is described in the IEEE 802.lie standard (Non-Patent Literature 3).
In the HCCA method, an access point centrally controls data transmission between a plurality of wireless LAN terminals, thereby realizing QoS (Quality of Service) among the plurality of wireless LAN terminals sharing the same channel.
For wirelessization of the industrial network, it is conceivable to adopt the HCCA method and to sequentially poll devices existing in the industrial network by wireless communication. Citation List Non-Patent Literature
[0005] Non-Patent Literature 1: Introduction to industrial Ethernet (registered trademark), CQ publisher, May 2009
Non-Patent Literature 2: IEEE Std 802.11™-2012 "Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications"
Non-Patent Literature 3: IEEE Std 802.11e™-2005 "Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications Amendment 8: Medium Access Control (MAC) Quality of Service Enhancements" Summary of Invention Technical Problem
[0006] In the industrial network, it is required to continuously communicate a small amount of real time data (cyclic data transmission in the CC-Link IE field network or a real time channel in the PROFINET) between the master device and the slave devices in

a fixed period.
Furthermore, in the industrial network, when there is non-real time data (transient transmission in the CC-Link IE field network or a non-real time channel in the PROFINET), the non-real time data is communicated between the master device and the slave devices if there is a margin in the period.
[0007] In the industrial network with wired communication which causes almost no error, it is possible to predict an allocation time of the real time data and an allocation time of the non-real time data in advance.
In addition, it is possible to decide in advance which slave device among the plurality of slave devices communicates non-real time data with the master device at which timing.
[0008] However, when the industrial network is wirelessized, there are following problems.
(1) Frequent communication error occurs, so it becomes necessary to modify the schedule for transmitting and receiving the real time data each time a communication error occurs. Then, it is necessary to notify each slave device of the schedule modification from the master device.
(2) Once the schedule is modified, a large amount of communication occurs from the master device to each slave device to inquire about the amount of data of real time data held by each slave device. For this reason, the communication efficiency decreases (when the number of slave devices increases to 16 or 32, the decrease in communication efficiency becomes more conspicuous).
These problems cause problems such as prolonging the period for communication between the master device and the slave devices or wasting frequency resources.

[0009] The present invention aims mainly to solve these problems. The present
invention aims to realize high reliability and high communication efficiency in wireless
communication where a communication error is likely to occur.
Solution to Problem
[0010] A wireless communication apparatus according to the present invention may
include:
a wireless scheduling unit to set a first data period for transmission of first data in a wireless communication period for performing wireless communication with a wireless communication device which transmits the first data and second data whose priority is lower than that of the first data, cause the wireless communication device to transmit the first data in the first data period, set remaining time of the wireless communication period to a second data period for transmission of the second data if the wireless communication period remains at a time when the transmission of the first data by the wireless communication device is completed, and cause the wireless communication device to transmit the second data in the second data period; and
a wireless reception unit to receive the first data in the first data period and receive the second data in the second data period. Advantageous Effects of Invention
[0011] In the present invention, a first data period for transmission of first data is set in a wireless communication period. Then, remaining time of the wireless communication period is set to a second data period for transmission of second data, if the wireless communication period remains at a time when the transmission of the first data is completed.
Therefore, according to the present invention, it is possible to definitely complete the transmission of the first data within the wireless communication period

and realize high reliability and high communication efficiency in wireless
communication.
Brief Description of Drawings
[0012] Fig. 1 is a diagram illustrating an example of an industrial network by wireless communication according to a first embodiment and an example of a conventional industrial network by wired communication.
Fig. 2 is a diagram illustrating examples of communication links between a wireless master apparatus and wireless slave apparatuses.
Fig. 3 is a diagram illustrating an example of communication sequence in the industrial network according to the first embodiment.
Fig. 4 is a diagram illustrating functional configuration examples of the wireless master apparatus and the wireless slave apparatus according to the first embodiment.
Fig. 5 is a diagram illustrating an example of communication sequence in a real time data period according to the first embodiment.
Fig. 6 is a diagram illustrating an example of communication sequence in a non-real time data period according to the first embodiment.
Fig. 7 is a flowchart diagram illustrating an example of operation of the wireless master apparatus according to the first embodiment.
Fig. 8 is a flowchart diagram illustrating an example of operation of the wireless master apparatus according to the first embodiment.
Fig. 9 is a flowchart diagram illustrating an example of operation of the wireless slave apparatus according to the first embodiment.
Fig. 10 is a diagram illustrating functional configuration examples of a wireless master apparatus and a wireless slave apparatus according to a second

embodiment.
Fig. 11 is a diagram illustrating a format of 802.11 Ack frame.
Fig. 12 is a diagram illustrating a format of 802.11 PPDU frame.
Fig. 13 is a diagram illustrating a method for notifying of the number of pieces of data held by the wireless slave apparatus in a Duration field according to the second embodiment.
Fig. 14 is a diagram illustrating a method for notifying of the number of pieces of data held by the wireless slave apparatus in a SERVICE field according to the second embodiment.
Fig. 15 is a diagram illustrating examples of hardware configuration of the wireless master apparatuses and wireless slave apparatuses according to the first embodiment and the second embodiment. Description of Embodiments [0013] First Embodiment
The present and following embodiments describe a configuration where real time data is continuously transmitted and received via wireless communication in a fixed period between a master device and slave devices in an industrial network, and where non-real time data is transmitted and received if there is a margin in the period.
In the present and following embodiments, the period for transmitting and receiving data between the master device and the slave devices is fixed.
Then, a real time data period is set at the beginning of the period and a non-real time data period is set after the real time data period.
Fluctuation due to a communication error is absorbed by extending or shortening a length of the real time data period.
When there is remaining time in the period after the real time data period is

completed, the remaining time is set to the non-real time data period.
Thereby, in the present and following embodiments, it is possible to obtain punctuality and effectiveness in communication resources. [0014] * * *Description of configuration* * *
Fig. 1 illustrates an example of system a configuration of conventional industrial network by wired communication and an example of system configuration of an industrial network by wireless communication according to the present embodiment.
In the industrial network by wired communication, wired communication is done with a master device Nl, a slave device (l)N101,a slave device (2) N102, a slave device (3) N103, and a slave device (m) N104.
When it is unnecessary to distinguish the slave device (1) Nl01, the slave device (2) N102, the slave device (3) N103, and the slave device (m) N104 from each other, each slave device is collectively referred to as a slave device N100. [0015] In the industrial network by wireless communication, a wireless master apparatus N201 is connected to a master device Nl.
The wireless master apparatus N201 is also referred to as a wireless master.
The master device Nl is, for example, a controller of the industrial network.
Further, a wireless slave apparatus (1) N301 is connected to a slave device (1) N101. A wireless slave apparatus (2) N302 is connected to a slave device (2) N102. A wireless slave apparatus (3) N303 is connected to a slave device (3) N103. A wireless slave apparatus (m) N304 is connected to a slave device (m) N104.
When it is unnecessary to distinguish the wireless slave apparatus (1) N301, the wireless slave apparatus (2) N302, the wireless slave apparatus (3) N303, and the wireless slave apparatus (m) N304 from each other, each wireless slave apparatus is collectively referred to as a wireless slave apparatus N300.

Further, the wireless slave apparatus N300 is also referred to as a wireless slave.
The slave devices N100 are, for example, various 10 devices, measuring instruments and so on in the industrial network.
The master device Nl and the slave device N100 perform communication via the wireless master apparatus N201 and the wireless slave apparatus N300 and can perform the same data exchange as in the case of wired communication.
In Fig. 1, a connection topology of the industrial network by wired communication is a line type (daisy chain type), and a connection topology of the industrial network by wireless communication is a one-to-N star type. However, this difference is not a substantial difference.
The connection topology of the industrial network by wired communication may be a star type, bus type, or ring type.
Also, the connection topology of the industrial network by wireless communication may be different from that illustrated in Fig. 1.
[0016] Note that the wireless master apparatus N201 corresponds to an example of a wireless communication apparatus and the wireless slave apparatus N300 corresponds to an example of a wireless communication device.
Each of an operation procedure performed by the wireless master apparatus N201 and an operation procedure performed by the wireless slave apparatus N300 correspond to an example of a wireless communication method and a wireless communication program.
[0017] Next, with reference to Fig. 2, communication between the master device Nl and the slave device N100 via the wireless master apparatus N201 and the wireless slave apparatus N300 will be described.

Fig. 2 illustrates an example of three pairs of slave device N100 and wireless slave apparatus N300.
[0018] The master device Nl and the wireless master apparatus N201 are wired connected.
Likewise, the slave device N100 and the wireless slave apparatus N300 are wired connected.
That is, the master device Nl and the wireless master apparatus N201 are connected by a wired communication link LI.
Also, the slave device (1) N101 and the wireless slave apparatus (1) N301 are connected by a wired communication link L31.
Further, the slave device (2) N102 and the wireless slave apparatus (2) N302 are connected by a wired communication link L32.
Furthermore, the slave device (3) N103 and the wireless slave apparatus (3) N303 are connected by a wired communication link L33.
Further, the wireless master apparatus N201 and the wireless slave apparatus N300 are wirelessly connected.
That is, the wireless master apparatus N201 and the wireless slave apparatus
(1) N301 are connected via a wireless communication link L21.
Further, the wireless master apparatus N201 and the wireless slave apparatus
(2) N302 are connected via a wireless communication link L22.
The wireless master apparatus N201 and the wireless slave apparatus (3) N303 are connected via a wireless communication link L23.
Since the wired communication links LI and L31 to L33 exist independently, different communication can be made between the master device Nl and the wireless master apparatus N201, and between the slave device N100 and the wireless slave

apparatus N300 at the same time.
On the other hand, between the wireless master apparatus N201 and the wireless slave apparatus N300, only one communication is possible at the same time.
In addition, the wireless master apparatus N201 grasps communication status of the wireless communication links L21 to L23. However, the wireless slave apparatus N300 cannot grasp the communication status of the wireless communication links L21 to L23.
When it is unnecessary to distinguish the wireless communication links L21 to L23 from each other, the wireless communication links L21 to L23 are collectively referred to as a wireless communication link L20.
Also, when it is unnecessary to distinguish the wired communication links L31 to L33 from each other, the wired communication links L31 to L33 are collectively referred to as a wired communication link L30.
[0019] Fig. 4 illustrates functional configuration examples of the wireless master apparatus N201 and the wireless slave apparatus N300 according to the present embodiment.
[0020] As illustrated in Fig. 4, the wireless master apparatus N201 is configured with a wired communication unit 11, a priority-based queue management unit 12, a wireless communication unit 13, and a storage unit 17. The wireless communication unit 13 is configured with a wireless transmission unit 14, a wireless reception unit 15, and a wireless scheduling unit 16.
[0021] As illustrated in Fig. 15, the wireless master apparatus N201 includes hardware such as a processor 901, a storage device 902, a wired communication interface 903, and a wireless communication interface 904.
The storage unit 17 is realized by the storage device 902.

Programs implementing functions of the wired communication unit 11, the priority-based queue management unit 12, the wireless transmission unit 14, the wireless reception unit 15, and the wireless scheduling unit 16 are stored in the storage device 902.
Then, the processor 901 executes these programs and performs operations of the wired communication unit 11, the priority-based queue management unit 12, the wireless transmission unit 14, the wireless reception unit 15, and the wireless scheduling unit 16 which will be described later.
Fig. 15 schematically illustrates a state in which the processor 901 executes the programs implementing the functions of the wired communication unit 11, the priority-based queue management unit 12, the wireless transmission unit 14, the wireless reception unit 15, and the wireless scheduling unit 16.
The wired communication interface 903 performs wired communication with the master device Nl.
The wireless communication interface 904 performs wireless communication with the wireless slave apparatus N300.
[0022] The wireless slave apparatus N300 is configured with a wired communication unit 21, a priority-based queue management unit 22, a wireless communication unit 23, and a storage unit 27. The wireless communication unit 23 is configured with a wireless transmission unit 24 and a wireless reception unit 25.
[0023] As illustrated in Fig. 15, the wireless slave apparatus N300 includes hardware such as a processor 905, a storage device 906, a wired communication interface 907, and a wireless communication interface 908.
The storage unit 27 is realized by the storage device 906.
The storage device 906 stores programs implementing functions of the wired

communication unit 21, the priority-based queue management unit 22, the wireless transmission unit 24, and the wireless reception unit 25.
Then, the processor 905 executes these programs and performs operations of the wired communication unit 21, the priority-based queue management unit 22, the wireless transmission unit 24, and the wireless reception unit 25, which will be described later.
Fig. 15 schematically illustrates a state in which the processor 905 executes the programs implementing the functions of the wired communication unit 21, the priority-based queue management unit 22, the wireless transmission unit 24, and the wireless reception unit 25.
The wired communication interface 907 performs wired communication with the slave device N100.
The wireless communication interface 908 performs wireless communication with the wireless master apparatus N201. [0024] ***Description of operation***
In the wireless master apparatus N201, the wired communication unit 11 receives data to be transmitted to the slave device N100, via the wired communication link LI from the master device Nl, using the wired communication interface 903.
In addition, the wired communication unit 11 transmits the data transmitted from the slave device N100, to the master device Nl via the wired communication link LI, using the wired communication interface 903.
The data transmitted and received by the wired communication unit 11 has priority.
In the present embodiment, an example will be described in which the wired communication unit 11 transmits and receives real time data and non-real time data.

In the present embodiment, the priority of real time data is high, and the priority of non-real time data is lower than the priority of real time data.
The real time data corresponds to an example of first data, and the non-real time data corresponds to an example of second data.
[0025] The priority-based queue management unit 12 manages queues provided for each priority.
The queues by priority are provided in the storage unit 17 which is a storage area of data.
That is, the storage unit 17 stores the real time data and the non-real time data by priority.
When the real time data is received, the priority-based queue management unit 12 stores the received real time data in a high priority queue. When the non-real time data is received, the priority-based queue management unit 12 stores the received non-real time data in a low priority queue.
The priority-based queue management unit 12 reads the real time data from the high priority queue and reads the non-real time data from the low priority queue. [0026] The wireless communication unit 13 performs wireless communication with the wireless slave apparatus N300.
The wireless communication unit 13 is configured with the wireless transmission unit 14, the wireless reception unit 15, and the wireless scheduling unit 16. [0027] The wireless transmission unit 14 transmits the data received by the wired communication unit 11 to the wireless slave apparatus N300 via the wireless communication link L20, using the wireless communication interface 904.
The wireless reception unit 15 receives the data transmitted from the wireless slave apparatus N300 via the wireless communication link L20, using the wireless

communication interface 904.
The wireless scheduling unit 16 generates a data transmission schedule to the wireless slave apparatus N300.
More specifically, the wireless scheduling unit 16 sets the real time data period (a first data period) for transmitting the real time data (the first data) within a communication period (a wireless communication period) for performing wireless communication with the wireless slave apparatuses N300 being wireless communication devices.
Then, the wireless scheduling unit 16 makes the wireless slave apparatuses N300 to transmit the real time data intensively in the real time data period.
When the communication period remains at a time when the transmission of the real time data by the wireless slave apparatuses N300 is completed, the wireless scheduling unit 16 sets remaining time of the communication period as the non-real time data period (a second data period) for transmitting the non-real time data (the second data).
Then, the wireless scheduling unit 16 makes the wireless slave apparatuses N300 to transmit the non-real time data intensively in the non-real time data period. [0028] Information on the number and arrangement of network devices necessary for scheduling by the wireless scheduling unit 16 can be obtained by manually setting at a time of initial setting or by automatically learning through analyzing control frames flowing over the network.
[0029] Since the priority-based queue management unit 12 is used at a time of transmitting data from the high speed wired communication link LI to the low speed wireless communication link L20, it may be inside the wireless communication unit 13. [0030] In the wireless slave apparatus (1) N301, the wired communication unit 21

receives from the slave device N100 via the wired communication link L30, the data to be transmitted to the master device Nl, using the wired communication interface 907.
In addition, the wired communication unit 21 transmits the data transmitted from the master device Nl to the slave device N100 via the wired communication link L30, using the wired communication interface 907.
[0031] The priority-based queue management unit 22 manages queues provided for each priority.
The queues by priority are provided in the storage unit 27 which is a storage area of data.
That is, the storage unit 27 stores the real time data and the non-real time data by priority.
When the real time data is received, the priority-based queue management unit 22 stores the received real time data in a high priority queue. When the non-real time data is received, the priority-based queue management unit 22 stores the received non-real time data in a low priority queue.
The priority-based queue management unit 22 reads the real time data from the high priority queue and reads the non-real time data from the low priority queue. [0032] The wireless communication unit 23 performs wireless communication with the wireless slave apparatus N300.
The wireless communication unit 23 is configured with the wireless transmission unit 24 and the wireless reception unit 25.
[0033] The wireless transmission unit 24 transmits the data received by the wired communication unit 21 to the wireless master apparatus N201 via the wireless communication link L20, using the wireless communication interface 908.
Also, the wireless transmission unit 24 transmits to the wireless master

apparatus N201, notification data for notifying of the number of pieces of data by priority, the data being stored in the storage unit 27.
The wireless reception unit 25 receives the data transmitted from the wireless master apparatus N201, via the wireless communication link L20, using the wireless communication interface 908.
[0034] Since the priority-based queue management unit 22 is used at a time of transmitting data from the high speed wired communication link L30 to the low speed wireless communication link L20, the priority-based queue management unit 22 may be inside the wireless communication unit 23.
[0035] As illustrated in Fig. 4, in the present embodiment, the communication period for sending and receiving data between the master device Nl and the slave devices N100 is fixed.
In the present embodiment, the wireless scheduling unit 16 of the wireless master apparatus N201 sets the real time data period for transmission of the real time data within the communication period.
Then, during the real time data period, the wireless scheduling unit 16 instructs each wireless slave apparatus N300 in an arbitrary order to transmit the real time data and causes each wireless slave apparatus N300 to transmit the real time data.
When the communication period remains at a time when the transmission of the real time data by the plurality of wireless slave apparatuses N300 is completed, the wireless scheduling unit 16 sets remaining time of the communication period as the non-real time data period (the second data period) for transmitting the non-real time data (the second data).
Then, during the non-real time data period, the wireless scheduling unit 16 instructs each wireless slave apparatus N300 in an arbitrary order to transmit the

non-real time data and causes each wireless slave apparatus N300 to transmit the non-real time data.
Further, the wireless scheduling unit 16 causes the transmission of the non-real time data to stop at a time when the remaining time of the communication period is less than a threshold value, even if there exists a wireless slave apparatus N300 that has not transmitted the non-real time data.
Since the communication period repeatedly arrives, the wireless scheduling unit 16 repeats an operation of setting the real time data period and the non-real time data period for each communication period.
[0036] Next, an example of operation in the real time data period and an example of operation in the non-real time data period will be explained in detail with reference to Figs. 5 and 6.
Fig. 5 illustrates an example of communication sequence in the real time data period, and Fig. 6 illustrates an example of communication sequence in the real time data period.
[0037] As illustrated in Fig. 5, the real time data period starts with broadcast notification (frame notification from the master device Nl at a starting point of the period) to the wireless slave apparatuses N300 from the wireless master apparatus N201.
In each wireless slave apparatus N300, as a response to the broadcast notification from the wireless master apparatus N201, the wireless transmission unit 24 transmits notification data notifying of the number of pieces of real time data and the number of pieces of non-real time data held by the storage unit 27, to the wireless master apparatus N201.
The wireless transmission unit 24 may transmit the notification data notifying

of only the number of pieces of real time data.
In addition, when the number of pieces of real time data is predetermined in a system setting (for example, the number of pieces of real time data transmitted in one communication period is always one), the wireless transmission unit 24 transmits notification data notifying of the value predetermined in the system setting, even if storage unit 27 does not hold the real time data.
A method of realizing the notification data will be described in the second embodiment.
[0038] In the wireless master apparatus N201, the wireless scheduling unit 16 performs polling in an arbitrary order, using the wireless transmission unit 14.
When a communication error occurs, the wireless transmission unit 14 executes a retransmission procedure, and the wireless reception unit 15 receives the real time data from each wireless slave apparatus N300.
At a time when reception of the real time data from all the wireless slave apparatuses N300 is completed, the wireless scheduling unit 16 calculates a schedule according to the number of pieces of non-real time data held by the wireless master apparatus N201 and each wireless slave apparatus (1) N301, based on the remaining time of the communication period.
[0039] Next, an operation example in the non-real time data period will be described with reference to Fig. 6.
In an example of Fig. 6, the wireless transmission unit 14 of the wireless master apparatus N201 transmits the non-real time data held by the wireless master apparatus N201 to the wireless slave apparatus (1) N301, and the wireless reception unit 15 receives Ack data.
Thereafter, the wireless scheduling unit 16 polls each wireless slave apparatus

N300 in an arbitrary order, and the wireless reception unit 25 receives the non-real time data from each wireless slave apparatus N300.
Immediately before the end of the communication period, the wireless scheduling unit 16 stops new communication when the remaining time becomes less than the threshold value.
The threshold value is determined in consideration of the time required for retransmission control at a time when a communication error occurs.
In the example of Fig. 6, the non-real time data has not yet been received from the wireless slave apparatus (2) N302, however, the remaining time has become less than the threshold value, therefore, the wireless scheduling unit 16 stops further polling to the wireless slave apparatus (2) N302.
[0040] A polling order for each wireless slave apparatus N300 by the wireless scheduling unit 16 is determined so as to ensure fairness between the wireless slave apparatuses N300.
Although the example in which the non-real time data is unicasted is described here, the non-real time data may be broadcasted or multicasted. [0041] Next, an example of operation of the wireless master apparatus N201 according to the present embodiment will be described with reference to the flowcharts of Figs. 7 and 8.
[0042] When the communication period starts, the wireless transmission unit 14 transmits the real time data to each wireless slave apparatus N300 (SI01).
More specifically, the priority-based queue management unit 12 reads the real time data from the storage unit 17 and outputs the read real time data to the wireless transmission unit 14.
The wireless transmission unit 14 then transmits the real time data from the

wireless communication link L20 to each wireless slave apparatus N300 via the wireless communication interface 904.
[0043] Next, the wireless reception unit 15 receives from each wireless slave apparatus N300, the Ack data on the real time data transmitted in S101 (SI02).
In this Ack data, the number of pieces of real time data and the number of pieces of non-real time data held by each wireless slave apparatus N300 are notified.
For the wireless slave apparatus N300 from which the Ack data could not have been received, the wireless transmission unit 14 retransmits the real time data. [0044] Next, the wireless scheduling unit 16 determines the polling order of real time data and the polling order of non-real time data (SI 03).
Any method is acceptable for determining the polling order by the wireless scheduling unit 16.
For example, the wireless scheduling unit 16 may determine the polling order according to a predetermined order between the wireless slave apparatuses N300.
Alternatively, the wireless scheduling unit 16 may determine the polling order of real time data according to the number of pieces of real time data notified by the Ack data. Further, the wireless scheduling unit 16 may determine the polling order of non-real time data according to the number of pieces of non-real time data notified by the Ack data.
[0045] Next, the wireless transmission unit 14 polls the wireless slave apparatuses N300 according to the polling order determined in SI03 (S104). [0046] Next, the wireless reception unit 15 receives the real time data from the wireless slave apparatus N300 which has been polled in S104 (S105).
In a case where the real time data has not been received from the wireless slave apparatus N300, the wireless transmission unit 14 polls again.

[0047] Next, the wireless scheduling unit 16 determines whether or not the real time data has been received from all the wireless slave apparatuses N300 (SI06).
If the real time data has been received from all the wireless slave apparatuses N300 (YES in S106), the process proceeds to S107.
On the other hand, if there is a wireless slave apparatus N300 from which the real time data has not been received (NO in SI06), the processes from SI04 onward are repeated.
[0048] In SI07, the wireless transmission unit 14 transmits non-real time data to any of the wireless slave apparatuses N300.
More specifically, the priority-based queue management unit 12 reads non-real time data from the storage unit 17, and outputs the read non-real time data to the wireless transmission unit 14.
The wireless transmission unit 14 then transmits the non-real time data from the wireless communication link L20 to the wireless slave apparatus N300 via the wireless communication interface 904.
[0049] Next, the wireless reception unit 15 receives the Ack data from the wireless slave apparatus N300 being a transmission destination of the non-real time data (SI 08).
If the Ack data has not been received, the wireless transmission unit 14 retransmits the non-real time data.
[0050] Next, the wireless transmission unit 14 polls the wireless slave apparatuses N300 according to the polling order determined in SI03 (SI09). [0051] Next, the wireless reception unit 15 receives the non-real time data from the wireless slave apparatus N300 which has been polled in SI09 (SI 10).
If the non-real time data has not been received from the wireless slave apparatus N300, the wireless transmission unit 14 polls again.

[0052] Next, the wireless scheduling unit 16 determines whether the remaining time of the communication period is sufficient, that is, whether or not the remaining time is equal to or more than the threshold value (Sill).
If the remaining time is equal to or more than the threshold value (YES in Sill), the process of SI04 is repeated.
On the other hand, if the remaining time is less than the threshold value (NO in Sill), the wireless scheduling unit 16 stops transmission of non-real time data ( SI 12) and waits for the next communication period to start, even if there exists a wireless slave apparatus N300 that has not transmitted the non-real time data.
Even if the non-real time data has been received from all wireless slave apparatuses N300, the wireless scheduling unit 16 similarly waits for the next communication period to start.
[0053] Next, an example of operation of the wireless slave apparatus N300 according to the present embodiment will be described with reference to Fig. 9. [0054] In the wireless slave apparatus N300, the wireless reception unit 25 receives the real time data transmitted from the wireless master apparatus N201 (S201).
More specifically, the wireless reception unit 25 receives the real time data transmitted from the wireless master apparatus N201 from the wireless communication link L20 via the wireless communication interface 908, and the wireless reception unit 25 outputs the received real time data to the priority-based queue management unit 22. [0055] Next, the wireless transmission unit 24 transmits Ack data (S202).
More specifically, the priority-based queue management unit 22 counts the number of pieces of real time data and the number of pieces of non-real time data stored in the storage unit 27. Then, the priority-based queue management unit 22 outputs to the wireless transmission unit 24, the notification data notifying of the number of pieces

of real time data and the number of pieces of non-real time data.
Further, the wireless transmission unit 24 generates Ack data including the notification data output from the priority-based queue management unit 22. Then, the wireless transmission unit 24 transmits the generated Ack data from the wireless communication link L20 to the wireless master apparatus N201 via the wireless communication interface 908.
[0056] Next, when the wireless reception unit 25 receives a polling notification about the real time data from the wireless master apparatus N201 (YES in S204), the wireless transmission unit 24 transmits the real time data to the wireless master apparatus N201 (S205).
More specifically, the wireless reception unit 25 outputs the polling notification received from the wireless master apparatus N201 to the priority-based queue management unit 22.
The priority-based queue management unit 22 acquires the polling notification received from the wireless master apparatus N201 and reads the real time data from the storage unit 27.
Furthermore, the priority-based queue management unit 22 outputs the read real time data to the wireless transmission unit 24.
The wireless transmission unit 24 transmits the real time data from the wireless communication link L20 to the wireless master apparatus N201 via the wireless communication interface 908.
[0057] In a case where the non-real time data is transmitted from the wireless master apparatus N201, the wireless reception unit 25 receives the non-real time data transmitted from the wireless master apparatus N201 (S206).
Note that the wireless reception unit 25 may not receive the non-real time data

transmitted from the wireless master apparatus N201 in some cases.
In the example of Fig. 6, the wireless slave apparatus (1) N301 receives the non-real time data transmitted from the wireless master apparatus N201. However, the wireless slave apparatus (2) N302 and the wireless slave apparatus (3) N303 do not receive the non-real time data from the wireless master apparatus N201.
When receiving the non-real time data transmitted from the wireless master apparatus N201, the wireless transmission unit 24 transmits Ack data to the wireless master apparatus N201.
[0058] Next, when the wireless reception unit 25 receives a polling notification about the non-real time data from the wireless master apparatus N201 (YES in S207), the wireless transmission unit 24 transmits the non-real time data to the wireless master apparatus N201 (S208).
More specifically, the wireless reception unit 25 outputs the polling notification received from the wireless master apparatus N201 to the priority-based queue management unit 22.
The priority-based queue management unit 22 acquires the polling notification received from the wireless master apparatus N201 and reads the non-real time data from the storage unit 27.
Furthermore, the priority-based queue management unit 22 outputs the read 1 non-real time data to the wireless transmission unit 24.
The wireless transmission unit 24 transmits the non-real time data from the wireless communication link L20 to the wireless master apparatus N201 via the wireless communication interface 908. [0059] ***Effects of embodiment***
According to the present embodiment, by setting the real time data period

before the non-real time data period, it is possible to reliably transmit and receive the real time data even if a communication error occurs. Also, according to the present embodiment, when there is a margin in the period, transmission and reception of non-real time data can be performed.
Therefore, it is possible to realize high reliability and high communication efficiency even in wireless communication where a communication error is likely to occur, and it is possible to effectively utilize frequency resources. [0060] Second Embodiment
The present embodiment describes a specific method by which the wireless slave apparatus N300 notifies the wireless master apparatus N201 of the number of pieces of real time data and the number of pieces of non-real time data held by the wireless slave apparatus N300.
[0061] In the present embodiment, the wireless transmission unit 24 of the wireless slave apparatus N300 is provided with a priority-based queue notification processing unit 26.
The priority-based queue notification processing unit 26 performs a process of notifying of the number of pieces of real time data and the number of pieces of non-real time data stored in the storage unit 27.
More specifically, the priority-based queue notification processing unit 26 performs a process of notifying of the number of pieces of real time data and the number of pieces of non-real time data counted by the priority-based queue management unit 22, in the Ack data which is transmitted in S203 of Fig.9. [0062] The priority-based queue notification processing unit 26 notifies the wireless master apparatus N201 of the number of pieces of real time data and the number of pieces of non-real time data held by the wireless slave apparatus N300, conforming to

802.11 (Non-Patent Literature 2) and not providing a new communication procedure and frame.
Hereinafter, two types of notification methods by the priority-based queue notification processing unit 26 will be described.
[0063] The first method is to use a Duration field in an Ack frame handled in a MAC layer (Fig. 11).
The second method is to use a SERVICE field in a PPDU frame handled in a PHY layer (Fig. 12).
[0064] In the first method, the priority-based queue notification processing unit 26 uses the Duration field to notify of the number of pieces of data, as illustrated in Fig. 13.
16 bits of the Duration field is a field indicating a future communication time, in a normal wireless LAN. For example, by setting the value of the 12th bit to 1, an access point of the wireless LAN can recognize that a calling terminal uses 4096 p,s to 8191 jis.
As illustrated in Fig. 13, the priority-based queue notification processing unit 26 can notify of the number of pieces of data in the queues corresponding to four priorities, using the 0th bit to the llth bit (bO to Ml).
In the present embodiment, since two data types of real time data and non-real time data are provided, as illustrated in Fig. 13, it is considered that the number of i pieces of real time data is notified of using b9 to bl 1 and the number of pieces of non-real time data is notified of using bO to b2.
[0065] In the second method, the priority-based queue notification processing unit 26
notifies of the number of pieces of data, using 16 bits of the SERVICE field which is an
unused (Reserved) area.
' Even with the second method, as illustrated in Fig. 14, as with the first

method, the priority-based queue notification processing unit 26 can notify of the number of pieces of data in the queues corresponding to four priorities, using bO tobll.
In the present embodiment, since two data types of real time data and non-real time data are provided. Therefore, as illustrated in Fig. 14, it is considered that the number of pieces of real time data is notified of using b9 to bll and the number of pieces of non-real time data is notified of using bO to b2.
[0066] In the examples of Figs. 13 and 14, since 3 bits are used, the number of pieces of real time data and the number of pieces of non-real time data to be notified of are each in the range of 0 to 7.
Since the maximum number of pieces that can be notified to the wireless master apparatus N201 is seven pieces, if more than or equal to seven pieces of real time data or non-real time data are held in the storage unit 27, it is not possible to notify of the actual number of pieces. However, an impact on scheduling is considered to be minor.
The number of pieces of data held in the storage unit 27 may be notified of using the number of bits which is3 bits or more.
Moreover, in Figs. 13 and 14, the reason for supporting four priorities is to support classified QoS.
16 bits of the Duration field and 16 bits of the SERVICE field may correspond to priorities other than four priorities.
In the industrial network, in principle, the use of wireless communication is limited within a factory, therefore, even if 802.11 frames for wireless LAN are used in a usage style illustrated in Fig. 13 or Fig. 14, they cause no confusion with a use in the wireless LAN. [0067] *** Appendix ***

The first embodiment and the second embodiment describe examples supporting priorities of two levels as the real time data and the non-real time data. However, priorities of three or more levels may be supported.
In this case, if the communication period remains at a time when the transmission of the second data being data with second priority by the plurality of wireless slave apparatus N300 is completed and a wireless slave apparatus N300 out of the plurality of wireless slave apparatus N300 holds third data whose priority is lower than that of the second data, the wireless scheduling unit 16 sets remaining time of the communication period to a third data period for transmission of the third data.
Then, the wireless scheduling unit 16 causes the wireless slave apparatus N300 holding the third data to transmit the third data in the third data period.
The wireless scheduling unit 16 performs the same process for fourth and subsequent data.
[0068] The first embodiment and the second embodiment describe examples in which the wireless master apparatus N201 is connected to one master device Nl, and the wireless slave apparatus N300 is connected to the slave device N100 on a one-to-one basis.
Depending on a configuration of the industrial network, the wireless master apparatus N201 may be connected to a plurality of master devices Nl belonging to different industrial networks.
Also, the wireless slave apparatus N300 may be connected to a plurality of industrial slave devices N100 belonging to different industrial networks. [0069] The first embodiment and the second embodiment describe examples adapted for the industrial network. The configurations and procedures described in the first embodiment and the second embodiment may also be applied to networks other than the

industrial network, as long as the networks are such that a master device and a slave device transmit and receive data by wireless communication. [0070] ***Description of hardware configuration***
Finally, supplementary explanation of the hardware configuration of the wireless master apparatus N201 and the wireless slave apparatus N300 will be made.
The wireless master apparatus N201 and the wireless slave apparatus N300 are computers.
The processors 901 and 905 illustrated in Fig. 15 are ICs (Integrated Circuits) which perform processing.
The processors 901 and 905 are CPUs (Central Processing Units), DSPs (Digital Signal Processors), or the like.
The storage devices 902 and 906 illustrated in Fig. 15 are RAMs (Random Access Memories), ROMs (Read Only Memories), flash memories, HDDs (Hard Disk Drives), or the like.
The wired communication interfaces 903 and 907 and the wireless communication interfaces 904 and 908 illustrated in Fig. 15 include a receiver for receiving data and a transmitter for transmitting data.
The wired communication interfaces 903 and 907 and the wireless communication interfaces 904 and 908 are, for example, communication chips or NICs (Network Interface Cards).
[0071] An OS (Operating System) is also stored in each of the storage devices 902 and 906.
At least a part of the OS is executed by each of the processors 901 and 905.
The processor 901 executes at least a part of the OS, and executes a program realizing functions of the wired communication unit 11, the priority-based queue

management unit 12, the wireless transmission unit 14, the wireless reception unit 15, and the wireless scheduling unit 16, which are functional elements of the wireless master apparatus N201.
Also, the processor 905 executes at least a part of the OS, and executes a program realizing functions of the wired communication unit 21, the priority-based queue management unit 22, the wireless transmission unit 24, and the wireless reception unit 25 (and the priority-based queue notification processing Unit 26), which are functional elements of the wireless slave apparatus N300.
Further, the program realizing the functions of the wireless master apparatus N201 and the program realizing the functions of the wireless slave apparatus N300 may be stored in a portable storage medium such as a magnetic disk, a flexible disk, an optical disk, a compact disk, a Blu-ray (registered trademark) disk, or a DVD. [0072] Further, the "units" being the functions of the wireless master apparatus N201 and the functions of the wireless slave apparatus N300 may be read as "processing circuitry", "circuits", "steps", "procedures", or "processes".
The "processing circuitry" or the "circuits" are each a concept including not only the processors 901 and 905, but also other types of processing circuits such as a logic IC, a GA (Gate Array), an ASIC (Application Specific Integrated Circuit), or a FPGA (Field-Programmable Gate Array). Reference Signs List
[0073] Nl: master device, N100: slave device, N101: slave device (1), N102: slave device (2), N103: slave device (3), N104: slave device (m), N201: wireless master apparatus, N300: wireless slave apparatus, N301: wireless slave apparatus (1), N302: wireless slave apparatus (2), N303: wireless slave apparatus (3), N304: wireless slave apparatus (m), 11: wired communication unit, 12: priority-based queue management

unit, 13: wireless communication unit, 14: wireless transmission unit, 15: wireless reception unit, 16: wireless scheduling unit, 17: storage unit, 21: wired communication unit, 22: priority-based queue management unit, 23: wireless communication unit, 24: wireless transmission unit, 25: wireless reception unit, 26: priority-based queue notification processing unit, 27: storage unit

Claims
[Claim 1] A wireless communication apparatus comprising:
a wireless scheduling unit to set a first data period for transmission of first data in a wireless communication period for performing wireless communication with a wireless communication device which transmits the first data and second data whose priority is lower than that of the first data, cause the wireless communication device to transmit the first data in the first data period, set remaining time of the wireless communication period to a second data period for transmission of the second data if the wireless communication period remains at a time when the transmission of the first data by the wireless communication device is completed, and cause the wireless communication device to transmit the second data in the second data period; and
a wireless reception unit to receive the first data in the first data period and receive the second data in the second data period.
[Claim 2] The wireless communication apparatus according to claim 1, wherein
the wireless scheduling unit sets a first data period for transmission of first data in a wireless communication period for performing wireless communication with a plurality of wireless communication devices each of which transmits the first data and second data whose priority is lower than that of the first data, causes the plurality of wireless communication devices to transmit the first data in the first data period, sets remaining time of the wireless communication period to a second data period for transmission of the second data if the wireless communication period remains at a time when the transmission of the first data by the plurality of wireless communication devices is completed, and causes a wireless communication device which is at least a part of the plurality of wireless communication devices to transmit the second data in

the second data period.
[Claim 3] The wireless communication apparatus according to claim 2, wherein
the wireless scheduling unit instructs, during the first data period, each of the wireless communication devices in an arbitrary order to transmit the first data to causes each of the wireless communication devices to transmit the first data, and instructs, during the second data period, each of the wireless communication devices in an arbitrary order to transmit the second data to cause each of the wireless communication devices to transmit the second data.
[Claim 4] The wireless communication apparatus according to claim 3, wherein
the wireless scheduling unit causes the transmission of the second data to stop at a time when the remaining time of the wireless communication period is less than a threshold value, even if there exists a wireless communication device that has not transmitted the second data.
[Claim 5] The wireless communication apparatus according to claim 1, wherein the wireless communication period repeatedly arrives, and wherein the wireless scheduling unit sets the first data period and the second data
period in each wireless communication period.
[Claim 6] The wireless communication apparatus according to claim 2, wherein
in a case where the wireless communication period remains at a time when the transmission of the second data by the plurality of wireless communication devices is completed and a wireless communication device out of the plurality of wireless

communication devices holds third data whose priority is lower than that of the second data,
the wireless scheduling unit sets remaining time of the wireless communication period to a third data period for transmission of the third data, and i causes the wireless communication device holding the third data to transmit the third data in the third data period.
[Claim 7] A wireless communication device comprising:
a storage unit to store by priority, data to which a priority is set, and which is ) to be transmitted to a wireless communication apparatus; and
a wireless transmission unit to transmit to the wireless communication apparatus, notification data for notifying by priority of the number of pieces of data stored in the storage unit.
i [Claim 8] The wireless communication device according to claim 7, comprises
a wireless reception unit to receive data from the wireless communication apparatus, wherein
the wireless transmission unit transmits to the wireless communication apparatus, notification data for notifying that the data transmitted from the wireless ) communication apparatus has been received by the wireless reception unit and notifying by priority of the number of pieces of data stored in the storage unit.
[Claim 9] A wireless communication method comprising:
by a wireless communication apparatus being a computer, setting a first data 5 period for transmission of first data in a wireless communication period for performing

wireless communication with a wireless communication device which transmits the first data and second data whose priority is lower than that of the first data, causing the wireless communication device to transmit the first data in the first data period, and receiving the first data in the first data period; and
by the wireless communication apparatus, setting remaining time of the wireless communication period to a second data period for transmission of the second data if the wireless communication period remains at a time when the transmission of the first data by the wireless communication device is completed, causing the wireless communication device to transmit the second data in the second data period, and receiving the second data in the second data period.
[Claim 10] A wireless communication method comprising:
by a wireless communication device being a computer, storing by priority, data to which a priority is set, and which is to be transmitted to a wireless communication apparatus in a storage area; and
by the wireless communication device, transmitting to the wireless communication apparatus, notification data for notifying by priority of the number of pieces of data stored in the storage area.
[Claim 11] A wireless communication program to cause a wireless communication apparatus being a computer, to execute:
a wireless scheduling process of setting a first data period for transmission of first data in a wireless communication period for performing wireless communication with a wireless communication device which transmits the first data and second data whose priority is lower than that of the first data, causing the wireless communication

device to transmit the first data in the first data period, setting remaining time of the wireless communication period to a second data period for transmission of the second data if the wireless communication period remains at a time when the transmission of the first data by the wireless communication device is completed, and causing the wireless communication device to transmit the second data in the second data period; and
a wireless reception process of receiving the first data in the first data period and receiving the second data in the second data period.
[Claim 12] A wireless communication program to cause a wireless communication device being a computer, to execute:
a data storage process to store by priority, data to which a priority is set, and which is to be transmitted to a wireless communication apparatus in a storage area; and
a wireless communication process to transmit to the wireless communication apparatus, notification data for notifying by priority of the number of pieces of data stored in the storage area.