Wireless communication systems and wireless communication methods

Abstract

The wireless communication system (10) of the present invention includes a communication unit (21) and a communication device (32). When using a communication channel composed of a plurality of communication time slots, the communication unit (21) and the communication device (32) change the communication channel in each jump cycle and use any one of the plurality of communication time slots to perform time division to implement wireless communication. Before the transport vehicle (20) transfers items to the load port (31), the communication unit (21) determines from the plurality of communication time slots the communication time slot that can transmit a trigger signal to the communication device (32), namely the first communication time slot, and uses the first communication time slot to transmit the trigger signal to the communication device (32). When the trigger signal is received from the communication unit (21), the communication device (32) performs interlocking communication with the communication unit (21) to allow the transport vehicle (20) to transfer items.

Description

Wireless communication systems and wireless communication methods This invention relates to a wireless communication system and a wireless communication method. Previously, wireless communication systems were known to perform wireless communication through time division. For example, Patent Document 1 discloses a wireless communication device that determines a communication slot based on inherent information to perform communication. [Prior Art Documents] [Patent Documents] Patent Document 1: Japanese Patent Application Publication No. 2006-121392 (Problems that the invention aims to solve) However, the wireless communication device in Patent Document 1 uses a communication time slot specified by the controller for wireless communication. Therefore, wireless communication cannot start before the communication time slot is specified by the controller, which may result in a delay in the start of communication. This invention was developed in view of the above-mentioned problems, and its purpose is to provide a wireless communication system, etc., which can be used to quickly initiate synchronous communication. (Technical means to solve the problem) To address the aforementioned problems, one aspect of the present invention provides a wireless communication system comprising: a communication unit mounted on a transport vehicle that moves along a track and transports goods; and a communication device connected to a load port where the goods are transferred by the transport vehicle, and wirelessly communicating with the communication unit; in communication using a communication channel comprised of a plurality of communication time slots, the communication unit and the communication device change the communication channel in each hopping cycle, and perform time-division wireless communication using any one of the plurality of communication time slots. Before the transport vehicle equipped with the aforementioned communication unit transfers the aforementioned items to the aforementioned load port, the aforementioned communication unit determines from the aforementioned plurality of communication time slots which can transmit a trigger signal to the aforementioned communication device, namely the first communication time slot, and uses the aforementioned first communication time slot to transmit the trigger signal to the aforementioned communication device. When the aforementioned trigger signal is received from the aforementioned communication unit, the aforementioned communication device conducts interlock communication with the aforementioned communication unit in relation to the transfer of the aforementioned items by the transport vehicle equipped with the aforementioned communication unit. According to this configuration, the communication unit determines the first communication time slot and uses the first communication time slot to transmit a trigger signal to the communication device. Therefore, it can determine the first communication time slot more quickly, enabling rapid initiation of synchronous communication. Furthermore, in order to determine the first communication slot, the communication unit uses one of the plurality of communication slots, namely the second communication slot, to transmit the trigger signal to the communication device, and upon receiving a response to the trigger signal from the communication device, it determines the second communication slot as the first communication slot. According to this configuration, since the first communication time slot can be determined more quickly by using a trigger signal, wireless communication using the communication time slot can be performed more efficiently. Therefore, it is possible to start synchronous communication more quickly. Furthermore, if a predetermined time has elapsed since the trigger signal was transmitted to the communication device using the second communication slot and no response has been received from the communication device, the communication unit uses one of the plurality of communication slots, a third communication slot different from the second communication slot, to transmit the trigger signal to the communication device. According to this configuration, since the first communication time slot can be determined more quickly by using a third communication time slot that is different from the second communication time slot, wireless communication using the communication time slot can be performed more efficiently. Therefore, it can achieve faster initiation of synchronous communication. Furthermore, the timing of transmitting the trigger signal to the communication device in the second communication time slot and the timing of transmitting the trigger signal to the communication device in the third communication time slot may be different from each other. According to this configuration, since the timing for transmitting the trigger signal in the communication time slot to the communication device can be determined more quickly, wireless communication using the communication time slot can be performed more effectively. Therefore, it can achieve faster initiation of synchronous communication. In addition, if no response related to the interlocking communication is received from the communication device after the interlocking communication is initiated, the communication unit may determine the first communication time slot and use the first communication time slot to transmit the trigger signal to the communication device. According to this configuration, since the first communication time slot can be determined more quickly when the interlocking communication has been disconnected, the trigger signal can be transmitted to the communication device more reliably using the first communication time slot, thus enabling more efficient wireless communication using the communication time slot. Therefore, it can achieve faster initiation of synchronization communication. In addition, the aforementioned trigger signal may also include a transmission start command, which is used to initiate the aforementioned interlocking communication. According to this configuration, since interlocking communication can be started more reliably, it can achieve faster initiation of synchronization communication. Furthermore, in order to solve the above-mentioned problems, one aspect of the present invention provides a wireless communication system comprising: a communication unit; and a communication device, which performs wireless communication with the communication unit; in communication using a communication channel composed of a plurality of communication time slots, the communication unit and the communication device change the communication channel in each switching cycle, and perform time-division wireless communication using any one of the plurality of communication time slots; the communication unit determines from the plurality of communication time slots a communication time slot, namely a first communication time slot, which can transmit a trigger signal to the communication device, and uses the first communication time slot to transmit the trigger signal to the communication device; when the trigger signal is received from the communication unit, the communication device performs pairing processing with the communication unit. According to this configuration, the communication unit determines the first communication time slot and uses the first communication time slot to transmit a trigger signal to the communication device. Therefore, it can determine the first communication time slot more quickly, and can use the first communication time slot to transmit the trigger signal to the communication device more reliably, thus enabling more efficient wireless communication using the communication time slot. Therefore, it can achieve faster initiation of synchronous communication. Furthermore, to address the aforementioned problems, one aspect of the wireless communication method of the present invention is a wireless communication method performed by a wireless communication system, which includes: a communication unit mounted on a transport vehicle that moves on a track and transports items; and a communication device connected to a load port where the items are transferred by the transport vehicle, and which wirelessly communicates with the communication unit; in communication using a communication channel composed of a plurality of communication time slots, the communication unit and the communication device change the communication channel in each switching cycle, and the plurality of communication time slots are used... In any time-division wireless communication, before the transport vehicle equipped with the aforementioned communication unit transfers the aforementioned item to the aforementioned load port, the aforementioned communication unit determines from the aforementioned plurality of communication time slots a communication time slot that can transmit a trigger signal to the aforementioned communication device, namely the first communication time slot, and uses the aforementioned first communication time slot to transmit the trigger signal to the aforementioned communication device. When the aforementioned trigger signal is received from the aforementioned communication unit, the aforementioned communication device conducts interlocking communication with the aforementioned communication unit related to the transfer of the aforementioned item by the transport vehicle equipped with the aforementioned communication unit. Based on this configuration, it can achieve the same function and effect as the aforementioned wireless communication system. Furthermore, this invention can be implemented not only as a device but also as a method. This method can be implemented by setting the processing means constituting the device as steps, or by executing a program that causes a computer to perform these steps, or by using a computer-readable recording medium such as a CD-ROM containing the program, or by using information, data, or signals representing the program. Moreover, these programs, information, data, and signals can also be transmitted via communication networks such as networks. (Effects compared to prior art) According to the present invention, a wireless communication system, etc., can be provided to enable rapid initiation of synchronous communication. The following describes the specific implementation details with reference to the diagrams. The embodiments described below represent preferred embodiments of the present invention. The numerical values, shapes, materials, constituent elements, their arrangement and connection methods, steps, and order of steps described in the following embodiments are merely examples and are not intended to limit the scope of the invention. Furthermore, constituent elements not described in the independent claims in the following embodiments are described as any constituent element constituting a preferred embodiment. Moreover, there are instances where the same element symbols are assigned to the same constituent elements, and their descriptions are omitted. (Implementation) Figure 1 is a schematic diagram showing the implementation of the wireless communication system 10. The wireless communication system 10 performs time-division wireless communication. As shown in Figure 1, the wireless communication system 10 includes a plurality of transport vehicles 20 and a plurality of semiconductor manufacturing devices 30. The transport vehicle 20 moves along a track and transports items. For example, the transport vehicle 20 is an OHT (Overhead Hoist Transfer) or similar device. Furthermore, the items are items such as FOUP (Front Opening Unified Pod). The transport vehicle 20 is equipped with a communication unit 21. The communication unit 21 is mounted on the transport vehicle 20. In communication using a communication channel comprised of a plurality of communication time slots, the communication unit 21 changes the communication channel in each hopping cycle and uses any one of the plurality of communication time slots for time-division wireless communication. Here, a communication time slot refers to a period allocated for communication at the same frequency (channel) being divided into one of a plurality of periods (e.g., 10 divisions). As will be described in detail later, before the transport vehicle 20, equipped with the communication unit 21, transfers items to the load port 31, the communication unit 21 determines from the plurality of communication time slots which can transmit a trigger signal to the communication device 32, i.e., the first communication time slot, and uses the first communication time slot to transmit the trigger signal to the communication device. Semiconductor manufacturing apparatus 30 manufactures semiconductors using items delivered by self-contained transport vehicle 20. Semiconductor manufacturing apparatus 30 has a plurality of load ports (LP) 31 and a plurality of communication devices 32. Load port 31 is one example of a handover port for goods transferred by the self-contained vehicle 20. Communication device 32 is connected to load port 31 and wirelessly communicates with communication unit 21. For example, communication device 32 wirelessly communicates with communication unit 21 via BLE (Bluetooth Low Energy) short-range wireless communication or short-range wireless communication using a separate communication method. In communication using a communication channel composed of multiple communication time slots, communication device 32 changes the communication channel in each switching cycle and uses any one of the multiple communication time slots for time-division wireless communication. As will be described in detail later, when a trigger signal is received from communication unit 21, communication device 32 and communication unit 21 conduct interlock communication related to the transfer of items via the transport vehicle 20 equipped with communication unit 21. Interlock communication is communication in accordance with SEMI (Semiconductor Equipment and Materials International) specifications E84. For example, interlock communication is used to authorize the transfer of items via the transport vehicle 20 equipped with communication unit 21. During the interlocking communication between the communication unit 21 and the communication device 32, it is permissible to transfer items from the transport vehicle 20 to the load port 31. The interlocking communication period specifically refers to the period during which the items transported by the transport vehicle 20 are transferred to the load port 31, and consists of three stages (procedures): before transfer, during transfer, and after transfer. For example, when the transport vehicle 20 is located at position 1, position 2, position 3 and position 4 respectively, the communication unit 21 of each of the transport vehicles 20 transmits a trigger signal to the communication device 32 connected to the load port 31 of the exchanged items. At this time, the communication unit 21 of each of the transport vehicles 20 determines from a plurality of communication time slots which can transmit the trigger signal, namely the first communication time slot, and uses the first communication time slot to transmit the trigger signal. Details will be explained later. For example, the communication unit 21 of each of the transport vehicles 20 searches from a plurality of communication time slots for a communication time slot not used by the communication units 21 of other transport vehicles 20, determines that communication time slot as the first communication time slot, and uses the first communication time slot to transmit the trigger signal. In this way, the communication units 21 of each of the transport vehicles 20 can transmit trigger signals to the communication device 32 more quickly and reliably. Therefore, it can efficiently perform wireless communication using the communication slot and efficiently transfer items. The wireless communication system 10 will now be described in detail. Figure 2 is a block diagram showing the functional configuration of the wireless communication system 10 in Figure 1. As shown in Figure 2, the communication unit 21 includes a transmission unit 22, a receiving unit 23, a decision unit 24, and a memory unit 25. For example, the communication unit 21 is implemented using a processor and communication circuits, etc. Furthermore, the memory unit 25 is implemented using memory, etc. The transmission unit 22 changes the communication channel in each hopping cycle and uses any one of the plurality of communication time slots to perform time-division wireless communication. The transmission unit 22 transmits a trigger signal to the communication device 32. The trigger signal may be, for example, a signal used to initiate interlocking communication (for achieving synchronization) (specifically, it may include a transmission start command to initiate interlocking communication). Furthermore, the transmission unit 22 transmits instructions related to interlocking communication (which may also include trigger signals). The transmission unit 22 uses the first communication time slot to transmit the trigger signal to the communication device 32. For example, in order to determine the first communication time slot, the transmission unit 22 uses one of the plurality of communication time slots, namely the second communication time slot, to transmit a trigger signal to the communication device 32. For example, the second communication time slot is the closest communication time slot among the plurality of communication time slots. For example, if a predetermined time elapses after transmitting a trigger signal to the communication device 32 using the second communication time slot without receiving a response from the communication device 32, the transmitting unit 22 will use one of the plurality of communication time slots, specifically a third communication time slot different from the second communication time slot, to transmit the trigger signal to the communication device 32. For example, the predetermined time is the time from the start of transmitting the trigger signal to the communication device 32 using the second communication time slot until the end of the second communication time slot. Furthermore, whether a response to the trigger signal is received from the communication device 32 is determined by whether the receiving unit 23 receives a response to the trigger signal from the communication device 32. For example, the timing of transmitting the trigger signal to the communication device 32 in the second communication time slot is different from the timing of transmitting the trigger signal to the communication device 32 in the third communication time slot. For example, when considering the case of each of the three divisions of the plurality of communication time slots, the receiving unit 22 transmits the trigger signal in the first period of the three periods divided in the second communication time slot, and transmits the trigger signal in the second period of the three periods divided in the third communication time slot. For example, the third communication slot is the next communication slot in a plurality of communication slots after the second communication slot. For example, before receiving a response to the trigger signal from the communication device 32, the transmission unit 22 transmits the trigger signal to the communication device 32 using each of the multiple communication time slots. The receiving unit 23 receives responses from the communication device 32. For example, the receiving unit 23 receives responses to trigger signals from the communication device 32. Furthermore, the receiving unit 23 receives responses related to interlocking communication from the transmitting unit 34 of the communication device 32. For example, responses related to interlocking communication are responses to interlocking communication-related instructions (requests) transmitted by the transmitting unit 22 to the communication device 32. For example, the communication packet related to this response includes responses to interlocking communication-related instructions (requests) transmitted by the transmitting unit 22 to the communication device 32 (ACK responses transmitted from the communication device 32 in interlocking communication) and IO (Input Output) data. Before the transfer vehicle 20 equipped with the communication unit 21 exchanges items with the load port 31, the decision unit 24 determines from a plurality of communication time slots which can transmit a trigger signal to the communication device 32, namely the first communication time slot. For example, the first communication time slot is a communication time slot that is not used by other transfer vehicles 20 among the plurality of transfer vehicles 20. For example, the decision unit 24 uses a trigger signal to determine the first communication time slot. Specifically, as described above, in order to determine the first communication time slot, the transmission unit 22 transmits a trigger signal to the communication device 32 using one of the plurality of communication time slots, namely the second communication time slot. When a response to the trigger signal is received from the communication device 32, the decision unit 24 determines the second communication time slot as the first communication time slot. Furthermore, as described above, if a predetermined time elapses after transmitting a trigger signal to the communication device 32 using the second communication time slot without receiving a response from the communication device 32, the transmission unit 22 uses one of the plurality of communication time slots, a third communication time slot different from the second communication time slot, to transmit the trigger signal to the communication device 32. When a response to the trigger signal is received from the communication device 32, the determination unit 24 determines the third communication time slot as the first communication time slot. Furthermore, as described above, before receiving a response to the trigger signal from the communication device 32, the transmission unit 22 repeatedly transmits the trigger signal to the communication device 32 using each of the plurality of communication time slots. The determination unit 24 determines the communication time slot used for transmitting the trigger signal that has received a response from the communication device 32 as the first communication time slot. For example, if no response related to interlocking communication is received from the communication device 32 after interlocking communication has started, the decision unit 24 determines the first communication time slot. For example, whether a response related to interlocking communication has been received from the communication device 32 is determined by whether the receiving unit 23 receives a response related to interlocking communication from the communication device 32. For example, the determination is made based on whether a response is received to an instruction (request) related to interlocking communication transmitted by the transmission unit 22 to the communication device 32. Whenever an instruction (request) related to interlocking communication transmitted by the transmission unit 22 to the communication device 32 is transmitted, the determination unit 24 determines whether a response has been received. If no response is received, it is determined that the interlocking communication has been disconnected, and the first communication time slot is determined again as described above. The transmission unit 22 uses the first communication time slot to transmit a trigger signal to the communication device 32 again. The memory unit 25 stores various types of information. For example, the memory unit 25 stores a jump table representing frequency jump patterns. In addition, the memory unit 25 stores programs executed by the communication unit 21 (processor). Figure 3 is an example of a skip table representing the memory of the transport vehicle 20 of the wireless communication system 10 in Figure 1. As shown in Figures 3(a) to (c), for example, the memory unit 25 stores 3 skip lists. The communication unit 21 first uses the skip list shown in Figure 3(a). It allocates one skip channel to the transport vehicle 20 from a plurality of skip channel groups. The communication unit 21 sequentially uses the three communication channels determined by the allocated skip channel groups. Each of the three communication channels consists of a plurality of communication time slots. The communication unit 21 changes the communication channel in each skip cycle and uses any one of the plurality of communication time slots for time-division wireless communication. When using the skip list shown in Figure 3(a), if wireless communication with the communication device 32 is not possible, the communication unit 21 uses the skip list shown in Figure 3(b). When using the skip list shown in Figure 3(b), if wireless communication with the communication device 32 is not possible, the communication unit 21 uses the skip list shown in Figure 3(c). Thus, the communication unit 21 can appropriately change the skip list it uses. Furthermore, the memory unit 25 can store one skip list instead of multiple skip lists. In this case, the communication unit 21 does not change the skip list it uses. For example, the communication unit 21 may not change the communication channel in each hopping cycle before receiving a response to the trigger signal (before synchronizing with the communication device 32), or it may use the same communication channel for three consecutive cycles, and change the communication channel after using it for three consecutive cycles, and use the changed communication channel for three consecutive cycles. Referring back to Figure 2, the communication device 32 includes a receiving unit 33, a transmitting unit 34, a processing unit 35, and a memory unit 36. For example, the communication device 32 is implemented using a processor and communication circuits. Furthermore, the memory unit 36 ​​is implemented using memory or the like. The receiving unit 33 receives a trigger signal from the communication unit 21. For example, the receiving unit 33 receives a command (request) related to interlocking communication from the communication unit 21. When the receiving unit 33 receives a trigger signal, the transmitting unit 34 transmits a response to the trigger signal to the communication unit 21. The transmitting unit 34 uses the communication time slot used for transmitting the trigger signal to transmit the response to the trigger signal to the communication unit 21. For example, after interlocking communication begins, the transmission unit 34 transmits a response related to the interlocking communication to the communication unit 21. For instance, whenever the receiving unit 33 receives an instruction (request) related to interlocking communication transmitted by the transmission unit 22 to the communication device 32, the transmission unit 34 transmits a response to that instruction to the communication unit 21. The transmission unit 34 uses the communication time slot used for transmitting the instruction (request) to transmit the response to the instruction to the communication unit 21. The processing unit 35 performs various processing tasks. When the communication unit 21 receives a trigger signal, the processing unit 35 conducts interlocking communication with the communication unit 21 via the transport vehicle 20 equipped with the communication unit 21 for the transfer of items. The memory unit 36 ​​stores various types of information. For example, the memory unit 36 ​​stores a jump table representing frequency jump patterns. In addition, the memory unit 36 ​​stores programs executed by the communication device 32 (processor). Figure 4 is an example of a skip table stored in the semiconductor manufacturing apparatus 30 of the wireless communication system 10 in Figure 1. As shown in Figure 4, for example, memory unit 36 ​​has one skip list. The communication device 32 uses the skip list shown in FIG. 4. One skip channel is allocated to the semiconductor manufacturing apparatus 30 from a plurality of skip channel groups. The communication device 32 sequentially uses the three communication channels determined by the allocated skip group. Each of the three communication channels is composed of a plurality of communication time slots. The communication device 32 changes the communication channel in each skip cycle and uses any one of the plurality of communication time slots for time-division wireless communication. Furthermore, the memory unit 36 ​​can also store a plurality of skip lists. In this case, the communication device 32 can also change the skip list used. Figure 5 is a flowchart illustrating an example of the operation of the communication unit 21 in the wireless communication method performed by the wireless communication system 10 of Figure 1. Referring to Figure 5, the process from the transmission of the trigger signal by the communication unit 21 in the first communication time slot to the end of the interlocking communication between the transport vehicle 20 and the communication device 32 will be described sequentially. As shown in Figure 5, the communication unit 21 determines the first communication time slot and uses the first communication time slot to transmit the trigger signal (step S1). For example, the communication unit 21 determines the first communication time slot as described above. For example, when the communication unit 21 uses the second communication time slot to transmit the trigger signal and receives a response to the trigger signal, it determines the second communication time slot as the new first communication time slot. In this case, since the trigger signal is being transmitted using the new first communication time slot, the communication unit 21 can also choose not to use the new first communication time slot to transmit the trigger signal after determining the new first communication time slot, and since it is in a state where interlocking communication can begin (a state of synchronization before communication is achieved between the transport vehicle 20 and the communication device 32), interlocking communication can continue to be performed. The communication unit 21 initiates interlocking communication with the communication device 32 (step S2). During the interlocking communication, items are transferred from the transport vehicle 20 to the load port 31. After interlocking communication is initiated, the communication unit 21 determines whether a response related to the interlocking communication has been received (step S3). For example, as described above, the communication unit 21 uses the first communication time slot to transmit instructions related to the interlocking communication to the communication device 32, and determines whether a response to the instruction has been received from the communication device 32. When no response related to interlocking communication is received (No in step S3), the communication unit 21 determines the first communication time slot again and uses the first communication time slot to transmit the trigger signal again (step S1). Thus, when no response related to interlocking communication is received, the communication unit 21 determines that the interlocking communication has been disconnected, and in order to restart the interlocking communication, it determines the first communication time slot again, transmits the trigger signal again, and attempts to restart the interlocking communication. Specifically, the communication unit 21 retransmits the same data that was transmitted when the communication was disconnected. When a response related to interlocking communication is received (Yes in step S3), the communication unit 21 determines whether the interlocking communication has ended (step S4). If the interlocking communication has not ended (No in step S4), the communication unit 21 determines again whether a response related to the interlocking communication has been received (step S3). When the interlocking communication ends (Yes in step S4), the communication unit 21 terminates the process. When the transfer of items from the transport vehicle 20 to the load port 31 has ended, the interlocking communication ends. Figure 6 is a flowchart illustrating an example of the operation of the communication device 32 in the wireless communication method performed by the wireless communication system 10 of Figure 1. Referring to Figure 6, the process from the moment the communication device 32 receives the trigger signal in the first communication time slot to the end of the interlocking communication between the transport vehicle 20 and the communication device 32 will be described sequentially. As shown in Figure 6, the communication device 32 determines whether a trigger signal has been received (step S11). If no trigger signal is received (No in step S11), the communication device 32 determines again whether a trigger signal has been received (step S11). When a trigger signal is received (Yes in step S11), the communication device 32 transmits a response to the trigger signal to the communication unit 21 (step S12) and begins interlocking communication (step S13). During the interlocking communication, the transport vehicle 20 delivers items to the load port 31. After initiating interlocking communication, the communication device 32 transmits a response related to the interlocking communication (step S14). For example, as described above, when a request related to interlocking communication is received, the communication device 32 transmits a response to the request to the communication unit 21. The communication device 32 determines whether a trigger signal has been received (step S15). When a trigger signal is received (Yes in step S15), the communication device 32 transmits a response to the trigger signal (step S12) and restarts interlocking communication (step S13). Thus, when a trigger signal is received after interlocking communication has started, the communication device 32 determines that the interlocking communication has been broken and restarts interlocking communication. When no trigger signal is received (No in step S15), the communication device 32 determines whether the interlocking communication has ended (step S16). When the interlocking communication has not ended (No in step S16), the communication device 32 transmits a response related to the interlocking communication again (step S14). When the interlocking communication has ended (Yes in step S16), the communication device 32 terminates the process. When the transfer of items from the transport vehicle 20 to the load port 31 has ended, the communication device 32 terminates the interlocking communication. Figures 7 and 8 are schematic diagrams illustrating an example of a wireless communication method performed by the wireless communication system 10 of Figure 1. Figure 7 shows the interaction between the communication unit 21 of the first transport vehicle 20 and the communication device 32 of the semiconductor manufacturing apparatus 30 in the wireless communication system 10. Figure 8 shows the interaction between the communication unit 21 of the second transport vehicle 20 and the communication device 32 of the semiconductor manufacturing apparatus 30 in the wireless communication system 10. Furthermore, in Figures 7(b) and 8(b), symbol I indicates the case where the communication unit 21 of the first transport vehicle 20 is in use, and II indicates the case where the communication unit 21 of the second transport vehicle 20 is in use. As shown in Figure 7(a), firstly, the communication unit 21 of the first transport vehicle 20 sequentially uses the communication slots (slot numbers 1-10) in a plurality of communication slots in the communication channel 1 (CH1) and repeatedly transmits trigger signals to the communication device 32 until a response is received from the communication device 32. Since a response has been received to the trigger signal transmitted using the 10th communication slot in communication channel 1, communication unit 21 designates the 10th communication slot as the 1st communication slot. Here, because communication unit 21 completed the transmission of the trigger signal using the 10th communication slot (the 1st communication slot), it can stop transmitting the trigger signal using the 1st communication slot after designating the 10th communication slot as the 1st communication slot. That is, since it is in a state where interlocking communication can begin, interlocking communication can continue to be executed. Since the communication device 32 receives the trigger signal, it transmits a response to the trigger signal to the communication unit 21, performs pairing processing with the communication unit 21, and begins interlocking communication with the communication unit 21. Here, the communication unit 21 and the communication device 32 perform wireless communication by changing the communication channel in each switching cycle, with the first communication time slot becoming the first communication time slot. Furthermore, the change of the communication channel in each switching cycle, as shown in the jump table with reference to Figures 3 and 4, is executed by the communication unit 21 and the communication device 32. Whenever the communication channel is changed, the communication unit 21 uses the first communication slot (first communication slot) in the changed communication channel to transmit instructions related to interlocking communication to the communication device 32. Whenever the communication channel is changed, the communication device 32 uses the first communication slot (first communication slot) in the changed communication channel to transmit a response to the instructions related to interlocking communication to the communication unit 21. As shown in Figure 7(b), the communication device 32 uses the first communication slot (I in Figure 7(b)) in each communication channel to wirelessly communicate with the communication unit 21 of the first transport vehicle 20. As shown in Figure 8(a), firstly, the communication unit 21 of the second transport vehicle 20 sequentially uses the communication slots (slot numbers 1-10) in the plurality of communication slots in the communication channel 1 (CH1) and transmits a trigger signal to the communication device 32 until a response is received from the communication device 32. Since a response has been received to the trigger signal transmitted using the 5th communication slot in communication channel 1, communication unit 21 designates the 5th communication slot as the 1st communication slot. Here, because communication unit 21 completed the transmission of the trigger signal using the 5th communication slot (the 1st communication slot), it can stop using the 1st communication slot to transmit the trigger signal after designating the 5th communication slot as the 1st communication slot. Because the communication device 32 receives the trigger signal, it transmits a response to the trigger signal to the communication unit 21, performs pairing processing with the communication unit 21, and begins interlocking communication with the communication unit 21. Here, the communication unit 21 uses the first communication time slot as the first communication time slot, changing the communication channel in each switching cycle and performing wireless communication. Furthermore, the communication device 32 uses the first communication time slot as the second communication time slot, changing the communication channel in each switching cycle and performing wireless communication. Moreover, in the communication channel used by the communication device 32, the first communication time slot is the first communication time slot used between it and the communication unit 21 of the first transport vehicle 20. As shown in Figure 8(b), the communication device 32 uses the first communication slot in each communication channel to wirelessly communicate with the communication unit 21 of the first transport vehicle 20, and uses the second communication slot in each communication channel to wirelessly communicate with the communication unit 21 of the second transport vehicle 20. The wireless communication system 10 of this embodiment includes: a communication unit 21 mounted on a transport vehicle 20, which moves on a track and transports items; and a communication device 32 connected to a load port 31 where items are transferred between the transport vehicle 20 and the communication unit 21, and which wirelessly communicates with the communication unit 21. In communication using a communication channel composed of a plurality of communication time slots, the communication unit 21 and the communication device 32 change the communication channel in each switching cycle, and use any one of the plurality of communication time slots for time division. In this wireless communication method, before the transport vehicle 20 equipped with the communication unit 21 transfers items to the load port 31, the communication unit 21 determines from a plurality of communication time slots which can transmit a trigger signal to the communication device 32, namely the first communication time slot, and uses the first communication time slot to transmit the trigger signal to the communication device 32. When the communication unit 21 receives the trigger signal, the communication device 32 conducts interlocking communication with the communication unit 21 related to the transfer of items by the transport vehicle 20 equipped with the communication unit 21. According to this configuration, the communication unit 21 determines the first communication time slot and uses the first communication time slot to transmit a trigger signal to the communication device 32. Therefore, it can determine the first communication time slot more quickly and achieve rapid initiation of synchronous communication. In addition, in order to determine the first communication time slot, the communication unit 21 uses one of the plurality of communication time slots, namely the second communication time slot, to transmit a trigger signal to the communication device 32, and when the communication device 32 receives a response to the trigger signal, the second communication time slot is determined as the first communication time slot. Based on this configuration, since the first communication time slot can be determined more quickly by using a trigger signal, wireless communication using the communication time slot can be performed more efficiently. Therefore, it can achieve faster initiation of synchronous communication. Furthermore, if a predetermined time has elapsed since the second communication slot was used to transmit a trigger signal to the communication device 32 and no response has been received from the communication device 32 for the trigger signal, the communication unit 21 will use one of the plurality of communication slots, which is a third communication slot different from the second communication slot, to transmit the trigger signal to the communication device 32. According to this configuration, by using a third communication time slot that is different from the second communication time slot, the first communication time slot can be determined more quickly, thus enabling more efficient wireless communication using the communication time slot. Therefore, it can achieve faster initiation of synchronous communication. Furthermore, the timing of transmitting the trigger signal to the communication device 32 in the second communication time slot is different from the timing of transmitting the trigger signal to the communication device 32 in the third communication time slot. According to this configuration, since the timing for transmitting the trigger signal in the communication time slot to the communication device 32 can be determined more quickly, wireless communication using the communication time slot can be performed more effectively. Therefore, it can achieve faster initiation of synchronous communication. Furthermore, if no response related to the interlocking communication is received from the communication device 32 after the interlocking communication is initiated, the communication unit 21 determines the first communication time slot and uses the first communication time slot to transmit a trigger signal to the communication device 32. According to this configuration, since the first communication time slot can be determined more quickly when the interlocking communication has been disconnected, and the trigger signal can be transmitted to the communication device 32 more reliably using the first communication time slot, wireless communication using the communication time slot can be performed more efficiently. Therefore, it can achieve faster initiation of synchronization communication. In addition, the trigger signal contains a transmission start command to initiate interlocking communication. According to this configuration, since interlocking communication can be started more reliably, it can achieve faster initiation of synchronization communication. Furthermore, the wireless communication method of this embodiment is a wireless communication method performed by a wireless communication system 10; the wireless communication system 10 includes: a communication unit 21 mounted on a transport vehicle 20, which moves on a track and transports items; and a communication device 32 connected to a load port 31 where items are transferred from the transport vehicle 20, and which wirelessly communicates with the communication unit 21; in communication using a communication channel composed of a plurality of communication time slots, the communication unit 21 and the communication device 32 change the communication channel in each switching cycle, and use any one of the plurality of communication time slots during operation. Wireless communication using a segmented method; before the transport vehicle 20 equipped with the communication unit 21 transfers items to the load port 31, the communication unit 21 determines from a plurality of communication time slots which can transmit a trigger signal to the communication device 32, namely the first communication time slot, and uses the first communication time slot to transmit the trigger signal to the communication device 32 (step S1). When the trigger signal is received from the communication unit 21, the communication device 32 conducts interlocking communication with the communication unit 21 related to the transfer of items (step S13). The items are transferred by the transport vehicle 20 equipped with the communication unit 21. According to this configuration, it can achieve the same function as the wireless communication system 10 described above. (Other embodiments, etc.) In the above embodiments, although it has been described that the communication unit 21 is mounted on the transport vehicle 20, the communication device 32 is connected to the load port 31, and before the transport vehicle 20 transfers items to the load port 31, the communication unit 21 uses the first communication slot to transmit a trigger signal to the communication device 32, and the communication device 32 performs interlocked communication with the communication unit 21, the present invention is not limited thereto. For example, the communication unit 21 may also be mounted on a mobile terminal, etc., and the communication device 32 may also be mounted on a mobile terminal, etc. In this case, for example, the communication unit 21 determines from a plurality of communication slots which can transmit a trigger signal to the communication device 32, namely the first communication slot, and uses the first communication slot to transmit the trigger signal to the communication device 32. Furthermore, when the communication unit 21 receives a trigger signal, the communication device 32 performs pairing processing with the communication unit 21. The wireless communication system of this embodiment includes: a communication unit 21; and a communication device 32, which wirelessly communicates with the communication unit 21. In communication using a communication channel composed of a plurality of communication time slots, the communication unit 21 and the communication device 32 change the communication channel in each switching cycle and use any one of the plurality of communication time slots to perform time-division wireless communication. The communication unit 21 determines from the plurality of communication time slots which can transmit a trigger signal to the communication device 32, namely the first communication time slot, and uses the first communication time slot to transmit the trigger signal to the communication device 32. When the communication unit 21 receives the trigger signal, the communication device 32 performs pairing processing with the communication unit 21. According to this configuration, the communication unit 21 determines the first communication time slot and uses the first communication time slot to transmit a trigger signal to the communication device 32. Therefore, it can determine the first communication time slot more quickly, and can use the first communication time slot to transmit the trigger signal to the communication device 32 more reliably, thus enabling more efficient wireless communication using the communication time slot. Therefore, it can achieve faster initiation of synchronous communication. Furthermore, although the above embodiment has described the case where the communication unit 21 uses a trigger signal to determine the first communication time slot, the present invention is not limited thereto. For example, the communication unit 21 may also obtain information from other communication units 21 indicating the predetermined or currently used communication time slots used by those other communication units 21, and determine the communication time slot other than that communication time slot among a plurality of communication time slots as the first communication time slot. While the wireless communication system and method of the present invention have been described above according to the embodiments, the present invention is not limited to these embodiments. Any modifications implemented in these embodiments, or combinations of constituent elements from different embodiments, that are conceived by those skilled in the art, are also included within the scope of the present invention, provided they do not depart from the spirit of the invention. (Additional Explanation) Based on the above description of the embodiments, the following technology is disclosed. (Technology 1) A wireless communication system comprising: a communication unit mounted on a transport vehicle that moves on a track and transports items; and a communication device connected to a load port where the items are transferred by the transport vehicle and wirelessly communicating with the communication unit; in communication using a communication channel consisting of a plurality of communication time slots, the communication unit and the communication device change the communication channel in each switching cycle and perform time-division wireless communication using any one of the plurality of communication time slots; before the transport vehicle equipped with the communication unit transfers the items to the load port, the communication unit determines a communication time slot from the plurality of communication time slots that can transmit a trigger signal to the communication device, i.e., a first communication time slot, and transmits the trigger signal to the communication device using the first communication time slot; when the trigger signal is received from the communication unit, the communication device performs interlocking communication with the communication unit related to the transfer of the items by the transport vehicle equipped with the communication unit. (Technology 2) In the wireless communication system described in Technology 1, in order to determine the first communication slot, the communication unit transmits the trigger signal to the communication device using one of the plurality of communication slots, namely the second communication slot, and when a response to the trigger signal is received from the communication device, the second communication slot is determined as the first communication slot. (Technology 3) In the wireless communication system described in Technology 2, when a predetermined time has elapsed since the trigger signal was transmitted to the communication device using the second communication slot and no response to the trigger signal has been received from the communication device, the communication unit uses one of the plurality of communication slots, a third communication slot that is different from the second communication slot, to transmit the trigger signal to the communication device. (Technology 4) In the wireless communication system described in Technology 3, the timing of transmitting the trigger signal to the communication device in the second communication time slot is different from the timing of transmitting the trigger signal to the communication device in the third communication time slot. (Technology 5) In the wireless communication system described in any one of Technologies 1 to 4, when no response related to the interlocking communication is received from the communication device after the interlocking communication is started, the communication unit determines the first communication time slot and uses the first communication time slot to transmit the trigger signal to the communication device. (Technology 6) A wireless communication system as described in any one of Technologies 1 to 5, wherein the trigger signal includes a transmission start command for initiating the interlocking communication. (Technology 7) A wireless communication system comprising: a communication unit; and a communication device that performs wireless communication with the communication unit; in communication using a communication channel composed of a plurality of communication time slots, the communication unit and the communication device change the communication channel in each switching cycle, and perform time-division wireless communication using any one of the plurality of communication time slots; the communication unit determines a communication time slot, i.e., a first communication time slot, from the plurality of communication time slots, to transmit a trigger signal to the communication device, and transmits the trigger signal to the communication device using the first communication time slot; when the trigger signal is received from the communication unit, the communication device performs pairing processing with the communication unit. (Technology 8) A wireless communication method, which is a wireless communication method performed by a wireless communication system, the wireless communication system comprising: a communication unit mounted on a transport vehicle that moves on a track and transports an item; and a communication device connected to a load port where the item is transferred by the transport vehicle, and wirelessly communicating with the communication unit; in communication using a communication channel composed of a plurality of communication time slots, the communication unit and the communication device change the communication channel in each switching cycle, and use any one of the plurality of communication time slots for time-division wireless communication; before the transport vehicle equipped with the communication unit transfers the item to the load port, the communication unit determines from the plurality of communication time slots a communication time slot, namely a first communication time slot, to transmit a trigger signal to the communication device, and uses the first communication time slot to transmit the trigger signal to the communication device. When the aforementioned trigger signal is received from the aforementioned communication unit, the aforementioned communication device establishes interlocking communication with the aforementioned communication unit in connection with the handover of the aforementioned items via the aforementioned transport vehicle equipped with the aforementioned communication unit. (Industrial Applicability) This invention can be applied to wireless communication systems that use communication time slots for wireless communication, etc. 10: Wireless Communication System; 20: Transport Vehicle; 21: Communication Unit; 22: Transmitter Unit; 23: Receiver Unit; 24: Decision Unit; 25: Memory Unit; 30: Semiconductor Manufacturing Equipment; 31: Load Port (LP); 32: Communication Device; 33: Receiver Unit; 34: Transmitter Unit; 35: Processing Unit; 36: Memory Unit Figure 1 is a schematic diagram showing an implementation of a wireless communication system. Figure 2 is a block diagram showing the functional configuration of the wireless communication system of Figure 1. Figures 3(a) to (c) are tables showing an example of the skip list stored by the transport vehicle in the wireless communication system of Figure 1. Figure 4 is a table showing an example of the skip list stored by the semiconductor manufacturing apparatus in the wireless communication system of Figure 1. Figure 5 is a flowchart showing an example of the operation of the communication unit in the wireless communication method performed by the wireless communication system of Figure 1. Figure 6 is a flowchart showing an example of the operation of the communication device in the wireless communication method performed by the wireless communication system of Figure 1. Figures 7(a) and (b) are schematic diagrams illustrating an example of the wireless communication method performed by the wireless communication system of Figure 1. Figures 8(a) and (b) are schematic diagrams illustrating an example of the wireless communication method performed by the wireless communication system of Figure 1. 10: Wireless Communication System 20: Moving truck 21: Ministry of Communications 22: Teleportation Department 23: Receiving Department 24: Decision-Making Department 25: Memory Department 30: Semiconductor manufacturing equipment 32: Communication device 33: Receiving Department 34: Teleportation Department 35: Processing Department 36: Memory Department

Claims

1. A wireless communication system comprising: a communication unit mounted on a transport vehicle that moves on a track and transports items; and a communication device connected to a load port where the items are transferred by the transport vehicle and wirelessly communicating with the communication unit; in communication using a communication channel consisting of a plurality of communication time slots, the communication unit and the communication device change the communication channel in each jump cycle and perform time-division wireless communication using any one of the plurality of communication time slots; before the transport vehicle equipped with the communication unit transfers the items to the load port, the communication unit determines a communication time slot from the plurality of communication time slots that can transmit a trigger signal to the communication device, i.e., a first communication time slot, and transmits the trigger signal to the communication device using the first communication time slot; when the trigger signal is received from the communication unit, the communication device performs interlocking communication with the communication unit related to the transfer of the items by the transport vehicle equipped with the communication unit.

2. The wireless communication system as described in claim 1, wherein, In order to determine the first communication slot, the communication unit uses one of the plurality of communication slots, namely the second communication slot, to transmit the trigger signal to the communication device, and when a response to the trigger signal is received from the communication device, the second communication slot is determined to be the first communication slot.

3. The wireless communication system as described in claim 2, wherein, When a predetermined time has elapsed since the trigger signal was transmitted to the communication device using the second communication slot, and no response has been received from the communication device for the trigger signal, the communication unit uses one of the plurality of communication slots, a third communication slot different from the second communication slot, to transmit the trigger signal to the communication device.

4. The wireless communication system as described in claim 3, wherein, The timing of transmitting the trigger signal to the communication device in the second communication time slot is different from the timing of transmitting the trigger signal to the communication device in the third communication time slot.

5. A wireless communication system as described in any of claims 1 to 4, wherein, If no response related to the interlocking communication is received from the communication device after the interlocking communication is initiated, the communication unit determines the first communication time slot and uses the first communication time slot to transmit the trigger signal to the communication device.

6. The wireless communication system as described in claim 1, wherein, The aforementioned trigger signal contains a transmission start command to initiate the aforementioned interlocking communication.

7. A wireless communication method, which is a wireless communication method performed by a wireless communication system, the wireless communication system comprising: a communication unit mounted on a transport vehicle that moves on a track and transports an item; and a communication device connected to a load port where the item is transferred by the transport vehicle, and wirelessly communicating with the communication unit; in communication using a communication channel composed of a plurality of communication time slots, the communication unit and the communication device change the communication channel in each jump cycle, and use any one of the plurality of communication time slots for time-division wireless communication; before the transport vehicle equipped with the communication unit transfers the item to the load port, the communication unit determines from the plurality of communication time slots a communication time slot, i.e., a first communication time slot, to transmit a trigger signal to the communication device, and uses the first communication time slot to transmit the trigger signal to the communication device. When the aforementioned trigger signal is received from the aforementioned communication unit, the aforementioned communication device conducts interlocking communication with the aforementioned communication unit in connection with the handover of the aforementioned items via the aforementioned transport vehicle equipped with the aforementioned communication unit.

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