Communication devices, communication systems, communication methods, and programs

Abstract

To provide communication devices and the like that enable efficient wireless communication. [Solution] The access point 30 is a communication device that wirelessly communicates with multiple other communication devices, which are multiple trolleys 40. The access point 30 includes a communication unit 32 that transmits first command information to one of the multiple trolleys 40, which is trolley 40a, to operate trolley 40a, and receives first response information transmitted from trolley 40a that has received the first command information and that relates to the operation based on the first command information. Between transmitting the first command information and receiving the first response information, the communication unit 32 transmits command information to the other trolleys 40b and 40c among the multiple trolleys 40, which are trolleys 40a, to operate their respective trolleys.

Description

Technical Field

[0001] The present disclosure relates to a communication device and the like.

Background Art

[0002] Conventionally, a communication device or the like that performs wireless communication with a plurality of other communication devices has been known. As an example of a communication device or the like, Patent Document 1 discloses a host device that transmits a command for requesting return of data to one or more terminal devices.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a certain host device exchanges command data / response data with a plurality of terminal devices, conventionally, command data is transmitted to one terminal device, response data from the terminal device is received, and then, one by one in order, command data is transmitted to other terminal devices and response data is received.

[0005] However, since it takes time to create response data in the terminal device, it often takes a long time from when the host device transmits command data until it receives response data, and there may be a situation of waiting for the transmission of command data to the next terminal device.

[0006] Therefore, even when wireless communication can be executed with low latency, a waiting time occurs while the previous terminal device creates response data, and there is a problem that wireless communication cannot be efficiently performed.

[0007] This invention was made to solve the above-mentioned problems and aims to provide a communication device, etc., that can perform wireless communication efficiently. [Means for solving the problem]

[0008] To solve the above problems, a communication device according to one aspect of the present invention is a communication device that performs wireless communication with a plurality of other communication devices, and includes a communication unit that transmits first command information to a first communication device which is one of the plurality of other communication devices for the operation of the first communication device, and receives first response information transmitted from the first communication device which received the first command information and relating to an operation based on the first command information, wherein the communication unit transmits command information to operate at least one other communication device other than the first communication device among the plurality of other communication devices between the time it transmits the first command information and the time it receives the first response information.

[0009] According to this, since the second command information is sent to one or more second communication devices between the transmission of the first command information and the reception of the first response information, the time between receiving the first response information and receiving one or more second response information can be suppressed, and wireless communication can be performed efficiently. The number of devices other than the first communication device to which the second command information is sent between the transmission of the first command information and the reception of the first response information depends on the time required for the first communication device, which received the first command information, to create the first response information.

[0010] In this context, both host and terminal devices are generally referred to as communication devices.

[0011] Furthermore, the communication unit transmits, in a first command slot which is a time slot for transmitting the first command information to the first communication device, first timing information indicating a first timing at which the first communication device transmits the first response information along with the first command information; and in a second command slot which is a time slot for transmitting the second command information to at least second communication devices other than the first communication device among the plurality of other communication devices, second timing information indicating a second timing at which the second communication device that receives the second command information transmits the second response information along with the second command information, wherein the first timing may be determined based on the length of time required for the first communication device to create the first response information, and the second timing may be determined based on the length of time required for the second communication device that receives the second command information to create the second response information.

[0012] According to this, it is possible to suppress the time until the first timing from becoming unnecessarily long, and also to suppress the time until the second timing from becoming unnecessarily long, so that the time until the second response information is received can be further suppressed, and wireless communication can be made even more efficient.

[0013] Furthermore, the communication unit transmits, in a first command slot which is a time slot for transmitting the first command information to the first communication device, first timing information indicating a first timing at which the first communication device transmits the first response information along with the first command information; and in a second command slot which is a time slot for transmitting the second command information to at least second communication devices other than the first communication device among the plurality of other communication devices, second timing information indicating a second timing at which the second communication device that receives the second command information transmits the second response information along with the second command information; the first timing and the second timing may be determined based on the longer of the time required for the first communication device to create the first response information and the time required for the other communication devices to create the response information.

[0014] According to this, it is possible to suppress the time until the first timing from becoming unnecessarily long, and also to suppress the time until the second timing from becoming unnecessarily long, so that the time until the second response information is received can be further suppressed, and wireless communication can be made even more efficient.

[0015] Furthermore, if the first communication device receives the first command information in the first command slot, it transmits first reception information to the communication unit indicating that the first command information has been received; if at least the second communication device receives the second command information in the second command slot, it transmits second reception information to the communication unit indicating that the second command information has been received; if the communication unit transmits the first command information to the first communication device in the first command slot but does not receive the first reception information from the first communication device, it transmits the first command information to the first communication device again in the first command slot; if it receives the first reception information from the first communication device, it transmits first modification information for changing the first timing to the first communication device; if at least the second command device transmits the second command information in the second command slot to the second communication device but does not receive the second reception information from the second communication device, it transmits the second command information to the second communication device again in the second command slot; if it receives the second reception information from the second communication device, it transmits the first modification information to the first communication device and transmits second modification information for changing the second timing to the second communication device.

[0016] According to this, if the first received information is not received from the first communication device, the first command information can be resent to the first communication device in the first command slot. If the first received information is received from the first communication device, the first change information can be sent to the first communication device, and the first timing can be appropriately changed, thus enabling more efficient wireless communication. Furthermore, if the second received information is not received from the second communication device, the second command information can be resent to the second communication device in the second command slot. If the second received information is received from the second communication device, the first change information can be sent to the first communication device, and the second change information can be sent to the second communication device to which the second timing information was sent, thereby enabling more efficient wireless communication.

[0017] Further, each of the plurality of other communication devices may be a cart for transporting an article.

[0018] According to this, wireless communication can be efficiently performed between the communication device and the plurality of carts.

[0019] Further, the communication device may be an access point.

[0020] According to this, wireless communication can be efficiently performed between the access point and the plurality of other communication devices.

[0021] Further, in order to solve the above problems, a communication system according to an aspect of the present invention includes the above communication device and the plurality of other communication devices.

[0022] According to this, the same operational effects as those of the above communication device are achieved.

[0023] Further, in order to solve the above problems, a communication method according to an aspect of the present invention is a communication method for performing wireless communication with a plurality of other communication devices, and transmits first command information for operating the first communication device to a first communication device which is one of the plurality of other communication devices, receives first response information regarding an operation based on the first command information, which is transmitted from the first communication device that has received the first command information, and transmits command information for operating at least one other communication device other than the first communication device among the plurality of other communication devices, from when the first command information is transmitted until the first response information is received.

[0024] According to this, the same operational effects as those of the above communication device are achieved.

[0025] Further, in order to solve the above problems, a program according to an aspect of the present invention is a program for causing a computer to execute the above communication method.

[0026] According to this, the same operational effects as those of the above communication method are achieved.

[0027] Note that the above-mentioned second command information, second response information, second timing information, and second change information are general terms for the respective information used for communication with a plurality of other communication devices other than the first communication device. Similarly, the second command slot is a general term for the respective slots used for communication with a plurality of other communication devices other than the first communication device. In the following embodiments, two other communication devices (carts) are taken as examples, and different codes are assigned to these terms for each device for explanation.

Effects of the Invention

[0028] According to the present invention, a communication device or the like can perform wireless communication efficiently.

Brief Description of the Drawings

[0029] [Figure 1] FIG. 1 is a block diagram showing a functional configuration of a communication system according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram showing an example of a communication frame. [Figure 3] FIG. 3 is a schematic diagram showing an example of a time slot used in wireless communication in the communication system of FIG. 1. [Figure 4] FIG. 4 is a sequence diagram showing a first operation example of the communication system of FIG. 1. [Figure 5] FIG. 5 is a first sequence diagram showing a second operation example of the communication system of FIG. 1. [Figure 6] FIG. 6 is a second sequence diagram showing a second operation example of the communication system of FIG. 1. [Figure 7] FIG. 7 is a third sequence diagram showing a second operation example of the communication system of FIG. 1. [Figure 8] FIG. 8 is a fourth sequence diagram showing a second operation example of the communication system of FIG. 1. [Figure 9] FIG. 9 is a fifth sequence diagram showing a second operation example of the communication system of FIG. 1. [Figure 10] FIG. 10 is a sixth sequence diagram showing a second operation example of the communication system of FIG. 1. [Figure 11] Figure 11 is the seventh sequence diagram showing a second example of the operation of the communication system in Figure 1. [Modes for carrying out the invention]

[0030] The embodiments will be described in detail below with reference to the drawings.

[0031] The embodiments described below are all preferred examples of the present invention. The numerical values, shapes, materials, components, arrangement positions and connection configurations of the components, steps, and the order of steps shown in the following embodiments are examples only and are not intended to limit the present invention.

[0032] Furthermore, among the components in the following embodiments, those components not described in an independent claim are described as any component constituting a more preferred form. Note that identical components may be denoted by the same reference numeral and their descriptions may be omitted.

[0033] (Embodiment) Figure 1 is a block diagram showing the functional configuration of a communication system 10 according to an embodiment. The functional configuration of the communication system 10 will be described with reference to Figure 1.

[0034] As shown in Figure 1, the communication system 10 comprises a higher-level server 20, an access point 30, and multiple trolleys 40, and is a system that performs wireless communication between the higher-level server 20, the access point 30, and the multiple trolleys 40. The multiple trolleys 40 are an example of multiple other communication devices, and the access point 30 is an example of a communication device that performs wireless communication with multiple other communication devices. In the following, a trolley 40 that is an example of a first communication device, which is one of the multiple other communication devices, may be described as trolley 40a, and a trolley 40 that is an example of one or more second communication devices, which are one or more other communication devices other than the first communication device, may be described as trolleys 40b, 40c.

[0035] In this embodiment, the example described is when the number of communication devices other than the first communication device is 2, but it is not limited to this case.

[0036] The upper-level server 20 includes a control unit 21, a communication unit 22, and a storage unit 23. For example, the control unit 21 may be composed of a processor, and the communication unit 22 may be composed of a wired communication circuit such as a wired LAN (Local Area Network) or serial communication. The communication unit 22 may also be composed of a wireless communication circuit such as an antenna and a wireless module. The storage unit 23 is composed of memory, etc.

[0037] The control unit 21 creates command information for operating the trolleys 40. Specifically, in a system with three trolleys (also referred to as trolleys 40a, 40b, and 40c), the control unit 21 creates first command information for operating trolley 40a, second command information for operating trolley 40b, and third command information for operating trolley 40c. For example, the first command information may be information for moving trolley 40a to a predetermined location, the second command information sent to trolley 40b may be information for moving trolley 40b to a predetermined location, and the third command information sent to trolley 40c may be information for moving trolley 40c to a predetermined location. Another example is that the first command information may be query information for confirming the status or position of trolley 40a, the second command information sent to trolley 40b may be query information for confirming the status or position of trolley 40b, and the third command information sent to trolley 40c may be query information for confirming the status or position of trolley 40c. In this embodiment, the command information transmitted to one or more communication devices other than the first communication device is described separately as second command information and third command information when there are two trolleys, but is also collectively referred to as second command information.

[0038] The communication unit 22 transmits command information (first command information, second command information, etc.) for operating the trolley 40 to the communication unit 32 of the access point 30, which will be described later. The communication unit 22 also receives response information (first response information, second response, and third response information, etc.) from the communication unit 32. In this embodiment, the response information received from one or more other communication devices other than the first communication device will be described separately as second response information and third response information when there are two trolleys, but will also be collectively referred to as second response information.

[0039] The memory unit 23 stores information for creating command information (such as first command information and second command information), and response information (such as first response information and second response information), etc.

[0040] The access point 30 includes a control unit 31, a communication unit 32, and a storage unit 33. For example, the control unit 31 is composed of a processor or the like, and the communication unit 32 may be composed of a wired communication circuit such as a wired LAN or serial communication for communication with the communication unit 22. The communication unit 22 may also be composed of a wireless communication circuit such as an antenna and a wireless module for communication with the communication unit 42. The storage unit 33 is composed of a memory or the like.

[0041] The control unit 31 creates timing information indicating the timing at which each trolley 40 should transmit response information to the access point 30. Specifically, the control unit 31 creates first timing information indicating the first timing at which trolley 40a transmits first response information, second timing information indicating the second timing at which trolley 40b transmits second response information, and third timing information indicating the third timing at which trolley 40c transmits third response information. In this embodiment, the timing information to be transmitted to one or more other communication devices other than the first communication device is described separately as second timing information and third timing information when there are two trolleys, but is also collectively referred to as second timing information.

[0042] The first response information is information about the operation based on the first command information, the second response information transmitted by the trolley 40b is information about the operation based on the second command information transmitted to the trolley 40b, and the third response information transmitted by the trolley 40c is information about the operation based on the third command information transmitted to the trolley 40c. For example, the first response information is information indicating the position of the trolley 40a that moved based on the first command information, the second response information transmitted by the trolley 40b is information indicating the position of the trolley 40b that moved based on the second command information, and the third response information transmitted by the trolley 40c is information indicating the position of the trolley 40c that moved based on the third command information.

[0043] For example, the control unit 31 determines the first timing based on the length of time La required for the trolley 40a to create the first response information. For example, the control unit 31 calculates the time by adding the length of the first command slot, which is a time slot for transmitting the first command information, and the length of time La required for the trolley 40a to create the first response information, and determines the timing after this time has elapsed from the time the trolley 40a receives the first command information as the first timing. Specifically, if the length of the first command slot is 500 μs and the length of time La required for the trolley 40a to create the first response information is 1000 μs, the control unit 31 determines the timing 1500 μs after the time the trolley 40a receives the first command information as the first timing.

[0044] Similarly, for example, the control unit 31 determines the second timing for the trolley 40b based on the length of time Lb required for the trolley 40b to create the second response information. For example, the control unit 31 calculates the time by adding the length of the second command slot, which is a time slot for transmitting the second command information to the trolley 40b, and the length of time Lb required for the trolley 40b to create the second response information, and determines the timing after this time has elapsed from the time the trolley 40b receives the second command information as the second timing. Specifically, if the length of the second command slot is 500 μs and the length of time Lb required for the trolley 40b to create the second response information is 1000 μs, the control unit 31 determines the timing 1500 μs after the time the trolley 40b receives the second command information as the second timing.

[0045] Similarly, for example, the control unit 31 determines the third timing for the trolley 40c based on the length of time Lc required for the trolley 40c to create the third response information. For example, the control unit 31 calculates the time by adding the length of the third command slot, which is a time slot for transmitting the third command information to the trolley 40c, and the length of time Lc required for the trolley 40c to create the second response information, and determines the timing after this time has elapsed from the time the trolley 40c receives the third command information as the third timing. Specifically, if the length of the second command slot is 500 μs and the length of time Lc required for the trolley 40c to create the third response information is 1000 μs, the control unit 31 determines the timing 1500 μs after the time the trolley 40c receives the second command information as the second timing.

[0046] For example, the control unit 31 determines the initial setting of the command slot length to be a length that allows command information to be retransmitted. That is, the control unit 31 determines the length of the first command slot to be a length that allows the first command information to be retransmitted, and the length of the second command slot to be a length that allows the second command information to be retransmitted. Specifically, if it takes 250 μs to transmit the first command information once, the control unit 31 determines the length of the first command slot to be 500 μs, etc. Similarly, if it takes 250 μs to transmit the second command information once, the control unit 31 determines the length of the second command slot to be 500 μs, etc. Note that the control unit 31 does not have to set the command slot length to be a length that allows command information to be retransmitted, and may set it to be a length that allows command information to be transmitted only once. Also, since the length of time required to transmit command information varies depending on the data size of the command information and the data transmission rate, etc., the control unit 31 may calculate the length of time required to transmit command information based on these and determine the length of the command slot. Similarly, the length of time required for the trolley 40 to transmit response information also varies depending on the data size and data transmission rate of the response information, so the length of the response slot may be determined based on this.

[0047] The memory unit 33 stores the length of time La required for the trolley 40a to create the first response information, the length of time Lb required for the trolley 40b to create the second response information, and the length of time Lc required for the trolley 40c to create the third response information.

[0048] The communication unit 32 transmits command information to each of the multiple trolleys 40 to operate the trolley 40 and receives response information from each of the multiple trolleys 40. In this embodiment, the communication unit 32 transmits first command information to trolley 40a and receives first response information transmitted from trolley 40a, which has received the first command information. Between transmitting the first command information and receiving the first response information, the communication unit 32 transmits second command information and third command information to each of the two trolleys 40b and 40c to operate the trolley. That is, the communication unit 32 transmits the first command information to trolley 40a, then the second command information to trolley 40b, and then the third command information to trolley 40c. After that, the communication unit 32 receives first response information from trolley 40a, second response information from trolley 40b, and third response information from trolley 40c.

[0049] For example, the communication unit 32 transmits first timing information along with first command information to the trolley 40a in the first command slot, transmits second timing information along with second command information in the second command slot for transmitting second command information to the trolley 40b, and transmits third timing information along with third command information in the third command slot for transmitting third command information to the trolley 40c.

[0050] Furthermore, for example, when first command information is transmitted to the trolley 40a in the first command slot, if the trolley 40a successfully receives the first command information, the trolley 40a transmits first reception information (ACK, etc.) indicating that it has successfully received the first command information. The communication unit 32 can receive the first reception information from the trolley 40a. If the communication unit 32 is unable to receive the first reception information from the trolley 40a due to communication loss or the like, it retransmits the first command information to the trolley 40a in the first command slot. On the other hand, when the communication unit 32 transmits first command information to the trolley 40a in the first command slot and receives the first reception information from the trolley 40a, it transmits first change information to the trolley 40a to change the first timing (details will be described later).

[0051] Furthermore, if the communication unit 32 transmits the second command information to the trolley 40b in the second command slot for transmitting the second command information to the trolley 40b, and does not receive second reception information from the trolley 40b indicating that the trolley 40b has received the second command information, the communication unit 32 retransmits the second command information to the trolley 40b in the same second command slot. On the other hand, if the communication unit 32 transmits the second command information to the trolley 40b in the second command slot for transmitting the second command information to the trolley 40b, and receives second reception information from the trolley 40b, it transmits the first change information to the trolley 40a and also transmits second change information to the trolley 40b to change the second timing. As described above, in this embodiment, the third timing information is transmitted to the trolley 40c after the trolley 40b, so the third timing information has not yet been transmitted to the trolley 40c. Therefore, the communication unit 32 transmits the second change information only to the bogie 40b of the bogies 40b and 40c to which the second timing information has been transmitted.

[0052] Furthermore, if the communication unit 32 transmits the third command information to the trolley 40c in the third command slot for transmitting the third command information to the trolley 40c, and does not receive third reception information from the trolley 40c indicating that the trolley 40c has received the third command information, it retransmits the third command information to the trolley 40c in the second command slot. On the other hand, if the communication unit 32 transmits the third command information to the trolley 40c in the third command slot for transmitting the third command information to the trolley 40c, and receives third reception information from the trolley 40c, it transmits the first change information to the trolley 40a, the second change information to the trolley 40b, and the third change information to the 40c. As described above, in this embodiment, the third timing information is transmitted to the trolley 40c after the trolley 40b. The second change information and the third change information are collectively referred to as the second change information.

[0053] The memory unit 33 stores information such as command information (first command information and second command information, etc.), timing information (first timing information and second timing information, etc.), response information (first response information and second response information, etc.), and time slot information (first time slot and second time slot, etc.).

[0054] Each of the multiple trolleys 40 is a trolley for transporting goods. Each of the multiple trolleys 40 has a control unit 41, a communication unit 42, and a storage unit 43. For example, the control unit 41 is composed of a processor, the communication unit 42 is composed of a wireless communication circuit such as an antenna and a wireless module, and the storage unit 43 is composed of a memory, etc.

[0055] The control unit 41 controls the trolleys 40 based on command information. Specifically, the control unit 41 of trolley 40a controls trolley 40a based on first command information. The control unit 41 of trolley 40b controls trolley 40b based on second command information. The control unit 41 of trolley 40c controls trolley 40c based on third command information.

[0056] Furthermore, the control unit 41 creates response information. Specifically, the control unit 41 of trolley 40a creates first response information. The control unit 41 of trolley 40b creates second response information. The control unit 41 of trolley 40c creates third response information.

[0057] When the communication unit 42 receives command information in a command slot, it transmits received information to the communication unit 32 indicating that it has received the command information. Specifically, when the communication unit 42 of the trolley 40a receives first command information in the first command slot, it transmits first received information to the communication unit 32. Similarly, when the communication unit 42 of the trolley 40b receives second command information in the second command slot, it transmits second received information to the communication unit 32. Furthermore, when the communication unit 42 of the trolley 40c receives third command information in the third command slot, it transmits third received information to the communication unit 32. For example, the first received information, second received information, and third received information may be ACKs, etc.

[0058] The memory unit 43 stores command information and response information, etc. Specifically, the memory unit 43 of trolley 40a stores first command information and first response information, etc. The memory unit 43 of trolley 40b stores second command information and second response information, etc. The memory unit 43 of trolley 40c stores third command information and third response information, etc.

[0059] Figure 2 is a schematic diagram showing an example of a communication frame. An example of a communication frame will be explained with reference to Figure 2.

[0060] The communication frames used when transmitting command information (such as the first command information and the second command information) and when transmitting response information (such as the first response information and the second response information) are the communication frames shown in Figure 2(a). The carrier sense to CW time will be explained in detail later.

[0061] Furthermore, the communication frame used when transmitting change information (first change information, second change information, etc.) is the one shown in Figure 2(b). The carrier sense to CW time will be explained in detail later.

[0062] Figure 3 is a schematic diagram showing an example of a time slot used in wireless communication in the communication system 10 shown in Figure 1. Referring to Figure 3, an example of a time slot used in wireless communication in the communication system 10 will be explained.

[0063] As shown in Figure 3, a second command slot for transmitting second command information to the trolley 40b and a third command slot for transmitting third command information to the trolley 40c are provided between the first command slot and the first response slot. The first command slot, second command slot, third command slot, and first response slot are provided consecutively in this order.

[0064] Following the first response slot, there is a second response slot for the trolley 40b to transmit second response information, and a third response slot for the trolley 40c to transmit third response information.

[0065] Figure 4 is a sequence diagram showing a first example of operation of the communication system 10 in Figure 1. The first example of operation of the communication system 10 will be explained with reference to Figure 4.

[0066] As shown in Figure 4, the communication unit 32 of the access point 30 transmits the first command information received from the upper server 20 to the trolley 40a in the first command slot (step S1). Here, the communication unit 32 transmits first timing information along with the first command information, and the first timing indicated by the first timing information is 1500 μs after the start of the first command slot of the trolley 40a (the time when the transmission of the first command information begins).

[0067] When the communication unit 42 of the trolley 40a receives the first command information, it transmits an ACK in the first command slot (step S2). When the trolley 40a receives the first command information, it starts operations based on the first command information and starts creating the first response information.

[0068] When the communication unit 32 of the access point 30 receives an ACK from the trolley 40a, it transmits the second command information for the trolley 40b, received from the upper-level server 20, to the trolley 40b in the second command slot (step S3). Here, the communication unit 32 transmits second timing information along with the second command information. The second timing indicated by the second timing information is 1500 μs after the start of the command slot of the trolley 40b (the time when the transmission of the second command information begins).

[0069] In the example shown in Figure 4, the communication unit 32 of the access point 30 resends the second command information to the trolley 40b in the second command slot because it did not receive an ACK from the trolley 40b (step S4). Here, the communication unit 32 resends the second timing information along with the second command information. The second timing indicated by the resent second timing information is changed to a timing 1250 μs later from the start of the command slot that the trolley 40b resends (the point at which it starts transmitting the second command information).

[0070] When the communication unit 42 of the trolley 40b receives the second command information, it sends an ACK in the second command slot (step S5). When the trolley 40b receives the second command information, it starts operations based on the second command information and starts creating the second response information.

[0071] When the communication unit 32 of the access point 30 receives an ACK from the trolley 40b, it transmits the third command information for the trolley 40c, received from the upper server 20, to the trolley 40c in the third command slot (step S6). Here, the communication unit 32 transmits the third timing information along with the third command information. The third timing indicated by the third timing information is 1500 μs after the start of the third command slot of the trolley 40c (the time when the transmission of the third command information begins).

[0072] When the communication unit 42 of the trolley 40c receives the second command information, it sends an ACK in the third command slot (step S7). When the trolley 40c receives the third command information, it starts operations based on the third command information and starts creating the third response information.

[0073] The communication unit 42 of the trolley 40a transmits first response information at a first timing in the first response slot (step S8). Here, the communication unit 42 starts a timer from the timing of the start of reception of the communication frame containing the first command information transmitted in step S1, and transmits the first response information at a first timing 1500 μs later.

[0074] When the communication unit 32 of the access point 30 receives first response information from the trolley 40a, it sends an ACK to the trolley 40a in the first response slot (step S9).

[0075] The communication unit 42 of the trolley 40b transmits the second response information at a second timing in the second response slot (step S10). Here, the communication unit 42 transmits the second response information at a second timing 1250 μs after the start timing of receiving the communication frame containing the second command information retransmitted in step S4.

[0076] When the communication unit 32 of the access point 30 receives the second response information from the trolley 40b, it sends an ACK to the trolley 40b in the second response slot (step S11).

[0077] The communication unit 42 of the trolley 40c transmits the third response information at the third timing in the third response slot (step S12). Here, the communication unit 42 transmits the third response information at the second timing, 1500 μs after the start timing of receiving the communication frame containing the third command information transmitted in step S6.

[0078] Incidentally, regarding the transmission of the first response information, second response information, and third response information, it is also possible to set the timing at which the information is transmitted from the access point 30 is always calculated by subtracting the communication time between the PLCP preamble and PLCP header (57.3 μs: see Figure 2), which is always a fixed time. This makes it possible to transmit the response information with more accurate timing, which is preferable.

[0079] For example, in the case of trolleys 40a and 40c, which receive data from access point 30 with a timing time of 1500 μs as illustrated above, the first response information or the third response information may be transmitted 1442.7 μs after the time when the PLCP header has been fully received. In the case of trolley 40b, which has a timing time of 1250 μs, the second response information may be transmitted 1192.7 μs after the time when the PLCP header has been fully received.

[0080] Furthermore, after receiving the PLCP header, the response information may not be sent after the first, second, or third timing as modified above, but rather after the "carrier sense ~ CW time" specified in the command information has finished. In that case, the timing of sending the response information should be set to the time obtained by subtracting the total time of the communication time of the PLCP preamble and PLCP header plus the "carrier sense ~ CW time", which would allow for even more accurate timing of sending the response information and would be even preferable.

[0081] The "Carrier Sense ~ CW Time" mentioned above represents the time taken for carrier sensing when sending the first command information, and the CW time spent waiting for random commands before resending the command information. Since time elapses between the start of the command slot and the actual transmission, sending the response information at the time when the PLCP header has been fully received, minus the "Carrier Sense ~ CW Time," will result in more accurate timing.

[0082] When the communication unit 32 of the access point 30 receives third response information from the trolley 40c, it sends an ACK to the trolley 40c in the third response slot (step S13).

[0083] The communication unit 32 of the access point 30 transmits the first response information, the second response information, and the third response information to the upper server 20 as appropriate.

[0084] As shown in the sequence in Figure 4, while the communication unit 32 of the access point 30 waits for a response to the command sent to the trolley 40a, it sends a command to the next trolley 40b or 40c. As a result, the overall response between the upper-level server and the trolleys can be made more efficient and faster.

[0085] Figures 5 to 11 are the first to seventh sequence diagrams showing a second operational example of the communication system 10 in Figure 1. The second operational example of the communication system 10 will be explained with reference to Figures 5 to 11.

[0086] As shown in Figure 5, the communication unit 32 of the access point 30 transmits the first command information received from the upper server 20 to the trolley 40a in the first command slot (step S21). Here, the communication unit 32 transmits the first timing information along with the first command information, and the first timing indicated by the first timing information is 1500 μs after the start of the first command slot of the trolley 40a (the time when the transmission of the first command information begins).

[0087] As shown in Figure 6, when the communication unit 42 of the trolley 40a receives the first command information, it sends an ACK in the first command slot (step S22). When the trolley 40a receives the first command information, it starts operations based on the first command information and starts creating the first response information.

[0088] In the second operational example, when the communication unit 32 of the access point 30 receives an ACK from the trolley 40a, it shortens the first command slot from 500 μs to 250 μs because the command retransmission time can be omitted, and transmits the first change information in a 125 μs time slot adjacent to the first command slot (step S23). Here, the first change information is information that changes the first timing to a timing 1125 μs after the timing at which the first change information is first received.

[0089] Furthermore, if the communication unit 42 of the trolley 40a determines that it has received the first change information when it has finished receiving the portion from the beginning of the communication frame up to the PLCP header, then the information to change the timing will be 1067.7 μs later, which is 1125 μs minus 57.3 μs. This will result in accurate timing.

[0090] Thus, if the length of the first command slot is set to a length that allows for the retransmission of the first command information, and the first command information is not retransmitted, the communication unit 32 shortens the first command slot.

[0091] When the communication unit 42 of the trolley 40a receives the first change information, it transmits an ACK in the time slot (step S24).

[0092] As shown in Figure 7, when the communication unit 32 of the access point 30 receives an ACK from the trolley 40a, it transmits the second command information received from the upper server 20 to the trolley 40b in the second command slot (step S25). In step S23, the first command slot was shortened to 250 μs and a slot of 125 μs for transmitting the first change information was added, so the second command slot changed from 500-1000 μs to 375-875 μs. Here, the communication unit 32 transmits the second timing information along with the second command information, and the second timing indicated by the second timing information is 1500 μs after the timing when the second command information was received.

[0093] As shown in Figure 8, when the communication unit 42 of the trolley 40b receives the second command information, it sends an ACK in the second command slot (step S26). When the trolley 40b receives the second command information, it starts operation based on the second command information and starts creating the second response information.

[0094] When the communication unit 32 of access point 30 receives an ACK from the trolley 40b, it shortens the second command slot from 500 μs to 250 μs, since it can also omit the retransmission time, and transmits the first change information in a 125 μs time slot adjacent to the second command slot (step S27). Here, the first change information is information that changes the first timing from 1125 μs after the start of the first command slot (the time when the transmission of the first command information begins) to 750 μs after the start of the first command slot (the time when the transmission of the first command information begins). In this way, when the length of the second command slot is set to a length that allows the second command information to be retransmitted, the communication unit 32 shortens the second command slot if the second command information is not retransmitted.

[0095] When the communication unit 42 of the trolley 40a receives the first change information, it transmits an ACK in the time slot (step S28).

[0096] When the communication unit 32 of the access point 30 receives an ACK from the trolley 40a in a 125μs time slot, it then transmits a second change information to the trolley 40b in the next 125μs time slot following that time slot (step S29). Here, the second change information is information that changes the second timing from 1500μs after the timing at which the second change information was transmitted to 875μs after that timing.

[0097] When the communication unit 42 of the trolley 40b receives the second change information, it transmits an ACK in the time slot (step S30).

[0098] As shown in Figure 9, when the communication unit 32 of the access point 30 receives an ACK from the cart 40b, it transmits the third command information for the cart 40c received from the upper server 20 to the cart 40c in the third command slot (step S31). Here, the communication unit 32 transmits the third timing information along with the third command information, and the third timing indicated by the third timing information is 1250 μs after the start of the third command slot (the time when the transmission of the third command information begins).

[0099] As shown in Figure 10, when the communication unit 42 of the trolley 40c receives the third command information, it transmits an ACK in the third command slot (step S32). The third command slot has changed from the initial 1000-1500 μs to 875-1375 μs due to the shortening of the first and second command slots. When the trolley 40c receives the third command information, it starts operation based on the third command information and starts creating the third response information.

[0100] When the communication unit 32 of the access point 30 receives an ACK from the trolley 40c, it shortens the second command slot from 500 μs to 250 μs, since the retransmission time can be omitted, and transmits the first change information in a 125 μs time slot adjacent to the third command slot (step S33). Here, the first change information is information that changes the first timing from 750 μs after the timing of transmitting the first change information to 375 μs after the timing of transmitting the first change information. In this way, when the length of the third command slot is set to allow for the retransmission of the third command information, the communication unit 32 shortens the third command slot if the third command information is not retransmitted.

[0101] When the communication unit 42 of the trolley 40a receives the first change information, it transmits an ACK in the time slot (step S34).

[0102] When the communication unit 32 of the access point 30 receives an ACK from the trolley 40a in a 125μs time slot, it transmits a second change information to the trolley 40b in a 125μs time slot that is consecutive to the said time slot (step S35). Here, the second change information is information that changes the second timing from 875wμs after the timing at which the second change information was transmitted to 500μs later.

[0103] When the communication unit 42 of the trolley 40b receives the second change information, it transmits an ACK in the relevant time slot (step S36).

[0104] When the communication unit 32 of the access point 30 receives an ACK from the trolley 40b in a 125μs time slot, it transmits the third change information to the trolley 40c in a 125μs time slot consecutive to that time slot (step S37). Here, the third change information is information that changes the third timing from 1250μs after the timing when the third change information is transmitted to 750μs later. In this case, the trolley 40c starts creating response information from the time it receives the command information in step S31, and has enough time to create the response information in 1250μs, which is the 500μs that has elapsed until it receives the third change information in step S37 (from steps S32 to S36) plus the 750μs included in the third change information. On the other hand, from the time when the trolley 40c returns ACK information to the access point 30 in step S38 until the trolley 40c transmits response information, the access point 30 can receive response information from trolleys 40a and 40b in steps S39 to S41.

[0105] When the communication unit 42 of the trolley 40c receives the third change information, it transmits an ACK in the relevant time slot (step S38).

[0106] As shown in Figure 11, the communication unit 42 of the trolley 40a transmits the first response information at a first timing in the first response slot (step S39). Here, the communication unit 42 transmits the first response information at a first timing 375 μs after the start timing of receiving the communication frame containing the first change information in step S33.

[0107] Furthermore, if the communication unit 42 of the trolley 40a determines that it has received the first change information when it has finished receiving the portion of the communication frame from the beginning to the PLCP header, then the first response information is transmitted at the first timing 317.7 μs later, which is 375 μs minus 57.3 μs.

[0108] When the communication unit 32 of the access point 30 receives the first response information, it transmits an ACK in the first response slot (step S40).

[0109] The communication unit 42 of the trolley 40b transmits the second response information at a second timing in the second response slot (step S41). Here, the communication unit 42 transmits the second response information at a second timing 500 μs after the start timing of receiving the communication frame containing the second change information in step S35.

[0110] Furthermore, if the communication unit 42 of the trolley 40b determines that it has received the second change information when it has finished receiving the portion of the communication frame from the beginning to the PLCP header, then it will transmit the second response information at the second timing, which is 442.7 μs later (500 μs minus 57.3 μs).

[0111] When the communication unit 32 of the access point 30 receives the second response information, it transmits an ACK in the second response slot (step S42).

[0112] The communication unit 42 of the trolley 40c transmits the third response information at the third timing in the third response slot (step S43). Here, the communication unit 42 transmits the third response information at the third timing, 750 μs after the start timing of receiving the communication frame containing the third change information in step S37.

[0113] Furthermore, if the communication unit 42 of the trolley 40c determines that it has received the third change information when it has finished receiving the portion of the communication frame from the beginning to the PLCP header, then it will transmit the third response information at the second timing, which is 692.7 μs later (750 μs minus 57.3 μs).

[0114] When the communication unit 32 of the access point 30 receives the third response information, it transmits an ACK in the third response slot (step S44).

[0115] The communication unit 32 of the access point 30 transmits the first response information, the second response information, and the third response information to the upper server 20 as appropriate.

[0116] The second operational example of the communication system 10 has been described above. In the second operational example, while initially a time range including retransmission time was set for each command slot, once the initial transmission is successful and ACK information is obtained from each cart, the retransmission time is omitted, and the timing for sending response information to each cart is changed accordingly. This makes it possible to further reduce the time required for command-response compared to the first operational example.

[0117] Furthermore, as described in the second example, the time at which each cart transmits response information is not determined by the timing information sent from the access point, but rather by subtracting the communication time of the PLCP preamble and PLCP header (57.3 μs) from that timing information, as described in the first example. This allows for a more accurate transmission time for each cart. Also, as described in the first example, it is also acceptable to subtract the carrier sense time from this time.

[0118] The access point 30 according to this embodiment is a communication device that performs wireless communication with a plurality of other communication devices, which are a plurality of trolleys 40. It includes a communication unit 32 that transmits first command information to a trolley 40a, which is one of the plurality of trolleys 40, to operate the trolley 40a, and receives first response information transmitted from the trolley 40a that received the first command information and relating to the operation based on the first command information. Between transmitting the first command information and receiving the first response information, the communication unit 32 transmits command information to operate at least one of the plurality of trolleys 40 other than trolley 40a, which are the trolleys 40b.

[0119] According to this, since the second command information is sent to the trolley 40b between the transmission of the first command information and the reception of the first response information, it is possible to suppress the time between receiving the first response information and receiving one or more second response information, thereby enabling efficient wireless communication.

[0120] Furthermore, in a first command slot, which is a time slot for transmitting first command information to the trolley 40a, the communication unit 32 transmits first timing information indicating a first timing at which the trolley 40a transmits first response information along with the first command information. In a second command slot, which is a time slot for transmitting second command information to at least the trolleys 40b other than trolley 40a among the multiple trolleys 40, the communication unit 32 transmits second timing information indicating a second timing at which the trolley 40b that receives the second command information transmits second response information along with the second command information. The first timing is determined based on the length of time required for the trolley 40a to create the first response information, and the second timing is determined based on the length of time required for the trolley 40b that receives the second command information to create the second response information.

[0121] According to this, it is possible to suppress the time until the first timing from becoming unnecessarily long, and also to suppress the time until the second timing from becoming unnecessarily long, so that the time until the second response information is received can be further suppressed, and wireless communication can be made even more efficient.

[0122] The communication unit 32 transmits, in a first command slot which is a time slot for transmitting first command information to the trolley 40a, first timing information indicating the first timing at which the trolley 40a transmits first response information along with the first command information, and in a second command slot which is a time slot for transmitting second command information to at least the trolleys 40b other than trolley 40a among the multiple trolleys 40, second timing information indicating the second timing at which the trolley 40b that received the second command information transmits second response information along with the second command information. The first timing and the second timing are determined based on the longer of the time required for the trolley 40a to create the first response information and the time required for the trolley 40b to create the response information.

[0123] According to this, it is possible to suppress the time until the first timing from becoming unnecessarily long, and also to suppress the time until the second timing from becoming unnecessarily long, so that the time until the second response information is received can be further suppressed, and wireless communication can be made even more efficient.

[0124] When the trolley 40a receives first command information in the first command slot, it transmits first reception information to the communication unit 32 indicating that it has received the first command information. When at least the trolley 40b receives second command information in the second command slot, it transmits second reception information to the communication unit 32 indicating that it has received the second command information. When the communication unit 32 transmits first command information to the trolley 40a in the first command slot, but does not receive first reception information from the trolley 40a, it transmits first command information to the trolley 40a in the first command slot. If the command information is resent and the first received information is received from the trolley 40a, the first change information for changing the first timing is sent to the trolley 40a. If the second command information is sent in the second command slot for at least the trolley 40b, and the second received information is not received from the trolley 40b, the second command information is resent to the trolley 40b in the second command slot. If the second received information is received from the trolley 40b, the first change information is sent to the trolley 40a, and the second change information for changing the second timing is sent to the trolley 40b.

[0125] According to this, if the first received information is not received from the trolley 40a, the first command information can be resent to the trolley 40a in the first command slot. If the first received information is received from the trolley 40a, the first change information can be sent to the trolley 40a, and the first timing can be appropriately changed, thus enabling more efficient wireless communication. Furthermore, if the second received information is not received from the trolley 40b, the second command information can be resent to the trolley 40b in the second command slot. If the second received information is received from the trolley 40b, the first change information can be sent to the trolley 40a, and the second change information can be sent to the trolley 40b from which the second timing information was sent, thereby enabling more efficient wireless communication.

[0126] Furthermore, each of the multiple other communication devices is a trolley 40 for transporting goods.

[0127] According to this, wireless communication can be efficiently performed between the access point 30 and multiple trolleys 40.

[0128] The communication device is access point 30.

[0129] According to this, wireless communication can be efficiently performed between the access point 30 and multiple trolleys 40.

[0130] Furthermore, in order to solve the above problems, a communication system 10 according to one aspect of the present invention comprises the above-mentioned access point 30 and a plurality of trolleys 40.

[0131] According to this, it will produce the same effects as the access point 30 described above.

[0132] Furthermore, in order to solve the above problems, a communication method according to one aspect of the present invention is a communication method using an access point 30, which is a communication device that wirelessly communicates with a plurality of other communication devices, which are a plurality of trolleys 40, wherein the access point 30 transmits first command information to one of the plurality of trolleys 40, which is a trolley 40a, to operate the trolley 40a (step S1), receives first response information transmitted from the trolley 40a that received the first command information and relating to the operation based on the first command information (step S8), and transmits command information to operate at least one of the plurality of trolleys 40a other than trolley 40b between the time the first command information is transmitted and the time the first response information is received (step S3).

[0133] According to this, it will produce the same effects as the access point 30 described above.

[0134] Furthermore, in order to solve the above problems, a program according to one aspect of the present invention is a program that causes a computer to execute the above-described communication method.

[0135] According to this, it produces the same effects as the communication method described above.

[0136] (Other embodiments) In the embodiments described above, the case where the communication device is an access point 30 was explained, but it is not limited to this. For example, the communication device may be a server or the like.

[0137] Furthermore, although the above-described embodiment described a case where multiple other communication devices are multiple trolleys 40, the invention is not limited to this. For example, each of the multiple other communication devices may be a stationary communication device or the like.

[0138] Furthermore, in the embodiment described above, the case in which the communication unit 32 transmits second command information and third command information to each of the two trolleys 40b and 40c to operate them, between transmitting first command information to trolley 40a and receiving first response information from trolley 40a, was described, but the invention is not limited to this. The communication device may transmit second command information to only the second communication device to operate the second communication device between transmitting the first command information and receiving the first response information, or it may transmit command information to each of the three or more communication devices other than the first communication device to operate the respective communication devices. For example, the number of command information communication devices to send from the time the first command information is sent until the first response information is received may be determined based on the time required to send the first command information, the time required to send the second command information, the time required to send the third command information, ..., the time required to send the Nth command information, the time required to create the first response information, the time required to create the second response information, the time required to create the third response information, ..., the time required to create the Nth response information, etc.

[0139] Furthermore, the present invention can be implemented not only as an apparatus or system, but also as a method in which the processing means constituting the apparatus or system are steps, as a program that causes a computer to execute those steps, as a non-temporary recording medium such as a computer-readable CD-ROM on which the program is recorded, or as information, data, or signals that represent the program. These programs, information, data, and signals may be distributed via a communication network such as the Internet.

[0140] Although the communication device and the like of the present invention have been described above based on embodiments, the present invention is not limited to these embodiments. Within the scope of the present invention, various modifications that a person skilled in the art could conceive of are applied to these embodiments, as well as forms constructed by combining components from different embodiments, are also included without departing from the spirit of the present invention. [Industrial applicability]

[0141] The present invention can be used as a communication device, etc., for wireless communication with multiple other communication devices. [Explanation of symbols]

[0142] 10 Communication Systems 20 Top Servers 21,31,41 Control Unit 22,32,42 Communications Department 23,33,43 Storage section 30 access points 40, 40a, 40b, 40c Trolley

Claims

1. A communication device that performs wireless communication with multiple other communication devices, The system includes a communication unit that transmits first command information to a first communication device, which is one of the plurality of other communication devices, for the purpose of operating the first communication device, and receives first response information transmitted from the first communication device that received the first command information and relating to an operation based on the first command information. The communication unit transmits command information to operate at least one of the multiple other communication devices other than the first communication device between the time it transmits the first command information and the time it receives the first response information. Communication device.

2. The communication unit transmits, in a first command slot which is a time slot for transmitting the first command information to the first communication device, first timing information indicating a first timing at which the first communication device transmits the first response information along with the first command information, and in a second command slot which is a time slot for transmitting the second command information to at least a second communication device other than the first communication device among the plurality of other communication devices, second timing information indicating a second timing at which the second communication device that receives the second command information transmits the second response information along with the second command information. The first timing is determined based on the length of time required for the first communication device to create the first response information. The second timing is determined based on the length of time required for the second communication device, which has received the second command information, to create the second response information. The communication device according to claim 1.

3. The communication unit transmits, in a first command slot which is a time slot for transmitting the first command information to the first communication device, first timing information indicating a first timing at which the first communication device transmits the first response information along with the first command information, and in a second command slot which is a time slot for transmitting the second command information to at least a second communication device other than the first communication device among the plurality of other communication devices, second timing information indicating a second timing at which the second communication device that receives the second command information transmits the second response information along with the second command information. The first timing and the second timing are determined by comparing the length of time required for the first communication device to create the first response information with the length of time required for communication devices other than the first communication device to create the response information, and based on the longest time. The communication device according to claim 1.

4. When the first communication device receives the first command information in the first command slot, it transmits first reception information to the communication unit indicating that the first command information has been received. When at least the second communication device receives the second command information in the second command slot, it transmits second reception information to the communication unit indicating that the second command information has been received. The aforementioned communications unit is When the first command information is transmitted to the first communication device in the first command slot, and the first received information is not received from the first communication device, the first command information is transmitted again to the first communication device in the first command slot. When the first received information is received from the first communication device, the first change information for changing the first timing is transmitted to the first communication device. When the second command information is transmitted to the second communication device in the second command slot, and the second reception information is not received from the second communication device, the second command information is transmitted again to the second communication device in the second command slot. When the second reception information is received from the second communication device, the first change information is transmitted to the first communication device, and the second change information for changing the second timing is transmitted to the second communication device. The communication device according to claim 2.

5. Each of the aforementioned multiple other communication devices is a cart for transporting goods. A communication device according to any one of claims 1 to 4.

6. The aforementioned communication device is an access point. A communication device according to any one of claims 1 to 4.

7. A communication device according to any one of claims 1 to 4, The device comprises the aforementioned plurality of other communication devices, Communication system.

8. A communication method for wireless communication with multiple other communication devices, A first command information for operating the first communication device is transmitted to the first communication device, which is one of the plurality of other communication devices. The first communication device that received the first command information has transmitted first response information relating to an operation based on the first command information, Between the transmission of the first command information and the reception of the first response information, command information is transmitted to operate at least one of the multiple other communication devices other than the first communication device. Communication method.

9. A program that causes a computer to execute the communication method described in claim 8.

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