Wireless communication system

Abstract

To provide a wireless communication system that can wirelessly communicate priority data having higher priority without being affected by communication interference.SOLUTION: A wireless communication system 1 includes a wireless communication network through which wireless communication is performed between at least a first device 11 and a second device 12. In the case where wireless communication is performed between other communication apparatuses 15 in the vicinity of the first device 11 and its frequency band interferes with a frequency band of wireless communication performed between the first device 11 and the second device 12, when transmitting priority data with higher priority, the first device duplicates the priority data, generates two or more pieces of packet data independent of each other each including the priority data, and sequentially transmits, to the second device, each piece of generated packet data with time intervals from each other.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a wireless communication system including a wireless communication network that performs wireless communication between communication devices, and particularly to a wireless communication system capable of transmitting and receiving higher-priority priority data without being affected by communication interference.

Background Art

[0002] Compared with a wired communication system, a wireless communication system has advantages such as reduced space for cables and the ability of portable terminals such as smartphones, tablet terminals, and notebook personal computers (notebook PCs) to connect to a communication network without sacrificing their portability. In addition, wireless communication itself has also been speeded up and made cheaper, so the practical application of wireless communication has been further accelerated. Against this background, the standardization of wireless communication is being promoted by the IEEE (Institute of Electrical and Electronics Engineering).

[0003] Among them, the IEEE802.15.4 standard is a standard for performing small, inexpensive, and power-saving wireless communication in a wireless communication network, and communication devices compliant with this standard are used. In a wireless communication network compliant with the IEEE802.15.4 standard, various topologies composed of a CS (Collection station) as a collection control station and one or more nodes are adopted (see, for example, Non-Patent Document 1). In this communication topology, lower-level nodes transmit data to higher-level nodes or CS as needed. Also, various control signals are sent from higher-level nodes or CS to lower-level nodes.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

[0005] In communication topologies including the technology disclosed in Non-Patent Document 1, the same communication method (e.g., frequency channel) is often used within a multi-hop communication network. Therefore, collisions of data transmitted and received between nodes are a concern, potentially leading to communication interference. Furthermore, not limited to the aforementioned communication topologies, communication interference can occur in wireless communication networks compliant with the IEEE 802.15.4 standard when one communication device transmits packet data to another.

[0006] In this situation, the packet data that one communication device actually sends to another device may not only contain higher-priority data, but also contain ordinary data that is not particularly high-priority and whose absence would not have a significant impact. If the priority data is not sent to the other device, the system itself may stop working, or various IT businesses conducted via the wireless communication network may come to an immediate halt. Therefore, even when conducting wireless communication in an environment where communication interference may occur, it is essential that this priority data is always received by the other communication device, and error correction and compensation for data affected by communication interference must be implemented.

[0007] In wireless communication networks conforming to the IEEE 802.15.4 standard, technologies to effectively prevent communication interference have been proposed for some time. However, most of these technologies only performed uniform control (error control coding, robust modulation schemes, etc.) without considering the priority of the data to be transmitted. As a result, in order to ensure that priority data is reliably received by the receiving device without being affected by communication interference, various controls to prevent interference had to be applied to all data, including lower-priority data. Consequently, various redundant processing was applied not only to priority data but also to normal data, leading to the problem of reduced frequency utilization efficiency.

[0008] Therefore, the present invention was devised in view of the above-mentioned problems, and its objective is to provide a wireless communication system that can wirelessly transmit priority data, especially higher priority data, without being affected by communication interference. [Means for solving the problem]

[0009] The present inventors have invented a wireless communication system in which, in order to reliably transmit higher-priority data without being affected by communication interference, when a first device transmits higher-priority data, it generates two or more independent packet data containing the said priority data, and sequentially transmits each of the generated packet data to the second device at time intervals from each other.

[0010] The wireless communication system according to the first invention is a wireless communication system that includes a wireless communication network for wireless communication between at least a first device and a second device, wherein when the first device transmits priority data with a higher priority, it duplicates the priority data, generates two or more independent packet data containing these priority data, and sequentially transmits each of the generated packet data to the second device with a time interval between them.

[0011] The wireless communication system according to the second invention is characterized in that, in the first invention, the first device generates at least one packet data which includes other data and further includes the priority data.

[0012] The wireless communication system according to the third invention is a wireless communication system including a wireless communication network that performs wireless communication between at least a first device and a second device, wherein when the first device transmits priority data with a higher priority, it duplicates the priority data, generates packet data containing each of these priority data, transmits the generated packet data to the second device, and if it does not receive a notification of receipt of the packet data from the second device within a predetermined time, it further generates packet data containing the priority data and transmits the generated packet data to the second device.

[0013] The wireless communication system according to the fourth invention is characterized in that, in the third invention, the first device generates packet data which includes other data and further includes the priority data.

[0014] The fifth wireless communication system is a wireless communication system including a wireless communication network that performs wireless communication between at least three or more devices, and is characterized by comprising a first device that, when data is transmitted from a third device, considers it as priority data and duplicates it, generates two or more independent packet data containing these priority data, and transmits each of the generated packet data sequentially to the second device at time intervals from each other.

[0015] The wireless communication system according to the sixth invention is a wireless communication system including a wireless communication network that performs wireless communication between at least three or more devices, and is characterized in that, when it determines that data transmitted from a third device is priority data, the first device duplicates the priority data, generates two or more independent packet data containing these priority data, and transmits each of the generated packet data to the second device sequentially with time intervals between them. [Effects of the Invention]

[0016] According to the present invention, which has the configuration described above, in a communication network environment where communication interference occurs due to other communication equipment when a first device transmits packet data to a second device, even if one packet data is affected by interference, the other packet data is received by the second device, making it possible to transmit the priority data contained therein to the second device with a higher probability. Furthermore, even if either packet data is affected by the communication environment, error compensation for the data can be achieved through the other packet data.

[0017] Therefore, according to the present invention, priority data can be received more reliably by the other party's communication device without being affected by communication interference, and errors in the data can be compensated for if communication interference occurs. Furthermore, according to the present invention, there is no need to apply various controls to prevent special communication interference to normal data that is not of high priority. As a result, various redundant processing to suppress the effects of communication interference on normal data is no longer required, and it is possible to prevent a decrease in frequency utilization efficiency.

[0018] Furthermore, when transmitting two or more packet data, the first device can generate and transmit packet data that includes both normal data and priority data A. In this case, it is possible to prevent communication interference of priority data without increasing the number of packet data.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic diagram showing an example of a wireless communication system according to the present invention. [Figure 2] It is a diagram showing a specific example of a control support terminal when one node is assigned as a controlled terminal. [Figure 3] It is a diagram showing an example of a time chart of data transmission between nodes. [Figure 4] It is a diagram for explaining the processing operation in a wireless communication system to which the present invention is applied. [Figure 5] It is a diagram showing an example of a time chart when transmitting priority data. [Figure 6] When transmitting two or more packet data, it is a diagram for explaining an example of previously checking the degree of communication interference. [Figure 7] It is a diagram for explaining another embodiment of the wireless communication system according to the present invention. [Figure 8] It is a diagram showing verification results for confirming the effects of a wireless communication system to which the present invention is applied.

Embodiments for Carrying Out the Invention

[0020] Hereinafter, a wireless communication method as a first embodiment of the present invention will be described in detail. FIG. 1 is a schematic diagram showing an example of a wireless communication system 1 of this embodiment. The wireless communication system 1 includes, as wireless communication terminals, nodes 3-1, 3-2, 3-3, 3-4, 3-5 having a collection control station (hereinafter referred to as CS) 2 as a root, and a so-called tree-type topology is adopted. In this wireless communication system 1, lower-level nodes 3 perform upstream data communication toward higher-level nodes 3 and CS 2. Also, in the wireless communication system 1, higher-level nodes 3 and CS 2 perform downstream data communication toward lower-level nodes 3.

[0021] CS2 is the top-level master device and collects data transmitted via uplink data communication from each node 3-1 to 3-5. CS2 also acts as a central control unit for controlling the entire wireless communication system 1, and transmits control system data via downlink data communication to a specific node 3.

[0022] Node 3 is a general term for devices capable of sending and receiving data, including data transmission and relaying, and is, for example, a communication device compliant with the IEEE 802.15.4 standard. Node 3 may be implemented as a sensor that senses predetermined data and transmits it wirelessly, or as a wireless communication-capable terminal device such as a mobile phone, smartphone, tablet, wearable device, or notebook personal computer (PC). Furthermore, Node 3 may include a control system such as an actuator, or it may be configured as a device that controls robots or various vehicles. In such cases, various control operations will be executed based on control data transmitted downstream from CS2 via other Node 3s.

[0023] In this embodiment, we will explain using the example of a wireless communication system 1 shown in Figure 1, where five nodes 3-1, 3-2, 3-3, 3-4, and 3-5 are arranged under CS2, but we are not limited to this. That is, the nodes 3 arranged in the lower links of CS2 may be a tree structure composed of any branching pattern, as long as they allow CS2 to collect data, and may consist of one or more nodes 3.

[0024] In the wireless communication system 1 of this embodiment, for example, CS2 and the controlled terminal, as well as all nodes 3 located along their paths, may be identified as control support terminals. In the example shown in Figure 2, if nodes 3-4 are assigned as controlled terminals, then CS2, node 3-1, and node 3-4 will be identified as control support terminals. In this embodiment, the communication method is common to the wireless communication between these control support terminals and to the wireless communication between other paths, but for example, the communication methods may differ from each other.

[0025] Figure 3 shows an example of a time chart for data communication between nodes 3, where data is transmitted from node 3-5 to CS2 via node 3-2. CS2 and each of nodes 3-2 and 3-5 may be assigned an active period (communication period T1 (unit: time t)) and a sleep period T2 (unit: time t) within a basic interval T (intermittent standby period (unit: time t)). During the communication period T1, wireless communication is possible, while during the sleep period T2, the receiving side enters a sleep state, preventing wireless communication. By intentionally including a sleep period T2 within the basic interval T, power consumption can be reduced, thereby lowering the overall power consumption of the system.

[0026] When transmitting data from node 3-5 to CS2, node 3-2, which is higher up in the network, acts as the master, and node 3-5, which is lower up, acts as the slave. Similarly, between node 3-2 and CS2, CS2, as the higher up node, acts as the master, and node 3-2, which is lower up, acts as the slave. In this master-slave relationship, the higher-level master allocates a communication period T1 within the basic interval T, and the lower-level slave transmits data in accordance with the timing of the communication period T1 allocated by the master.

[0027] Under these rules, as shown in Figure 3, node 3-5 first transmits the data D21 it generated at timing t11, in accordance with the communication period T1 that begins at timing t12 of node 3-2, which is the master. Node 3-2, having received this data D21, transmits the same data D21 in accordance with the communication period T1 that begins at timing t13 of CS2, which is the master. This allows CS2 to receive this data D21 within the communication period T1 that it has set.

[0028] The data transmitted by CS2 and each node 3, which are communication devices compliant with the IEEE 802.15.4 standard, to other nodes 3 includes priority data, which has a higher priority, and normal data, which does not have a significant impact even if it is not actually transmitted or received. Priority data, in this context, refers to data that, if not transmitted to the receiving device, could cause the system itself to stop working or various IT businesses conducted via the wireless communication network to immediately come to a halt. In particular, data sent from CS2 to each node 3 may include priority data that contains, for example, control signals to immediately stop the operation of node 3 in an emergency. In such cases, the present invention performs the processing operations described below to ensure that only priority data is reliably received by the receiving CS2 or node 3 while suppressing the impact of communication interference.

[0029] Figure 4 is a diagram illustrating the processing operation for reliably transmitting only priority data to the other party while suppressing the effects of communication interference in a wireless communication system 1 to which the present invention is applied. Figure 4 shows an example in which packet data containing priority data A and normal data B is transmitted from the first device 11 to the second device 12. The first device 11 may be either CS2 or node 3, and the second device 12 may be a different CS2 or node 3 than the first device 11.

[0030] Here, we assume that wireless communication is being conducted between other communication devices 15 in the vicinity of the first device 11, and that its frequency band interferes with the frequency band of wireless communication being conducted between the first device 11 and the second device 12. When the first device 11, which is in such an interference area, transmits the priority data A it has generated to the second device 2, it generates two or more priority data by duplicating the priority data A. It then generates two or more independent packet data containing the generated priority data. These two or more packet data containing priority data are then transmitted sequentially to the second device 12 with time intervals between them. In the example in Figure 4, two packet data containing priority data A are shown, but it is not limited to this, and three or more packet data containing priority data A may be transmitted.

[0031] Alternatively, the first device 11 may configure at least one of the two or more packet data it generates to include both normal data B and priority data A. The first device 11 then transmits this packet data containing priority data A and normal data B to the second device 12. In the example in Figure 4, two packets are transmitted: one containing only priority data A and another containing priority data A and normal data B. However, the device is not limited to this, and two or more packets containing priority data A and normal data B may be transmitted.

[0032] Figure 5 shows an example of a time chart for transmitting this priority data. When transmitting two or more packets of priority data A, as shown in Figure 5(a), packet data containing only priority data A is generated for each packet and transmitted sequentially from the first device 11. The timing and interval of transmission of this packet data can be anything, and the transmission intervals may differ when transmitting three or more packets of data.

[0033] Figure 5(b) shows an example of transmitting a packet containing only priority data A, as well as a packet containing both priority data A and normal data B. The order in which these packet data are transmitted can be arbitrary, and the transmission timing and intervals for these packet data can be anything. Furthermore, when transmitting three or more packet data, the transmission intervals may differ from one another.

[0034] Even if the packet data length increases by including priority data A in normal data B, the number of packets to be transmitted can be reduced by combining them into a single packet rather than sending them as separate packets. Reducing the number of packets transmitted reduces the possibility of communication collisions.

[0035] Thus, according to the wireless communication system 1 to which the present invention is applied, when transmitting high-priority priority data A from the first device 11 to the second device 12, two or more independent packet data containing the priority data are generated, and each of the generated packet data is transmitted sequentially to the second device 12 with a time interval between them.

[0036] As a result, in a wireless communication system 1 to which the present invention is applied, even if one packet data is affected by interference from other communication equipment 15 when the first device 11 transmits packet data to the second device 12 in the communication network, the other packet data can be received by the second device 12, making it possible to transmit the priority data A contained therein to the second device 12 with a higher probability. Furthermore, even if either packet data is affected by the communication environment, error compensation for the data can be achieved through the other packet data.

[0037] Therefore, with the wireless communication system 1 to which the present invention is applied, priority data A can be received more reliably by the other party's communication device without being affected by communication interference, and error compensation for data that has been affected by communication interference can be achieved. Furthermore, with the wireless communication system 1 to which the present invention is applied, there is no need to apply various controls to prevent special communication interference to normal data B, which is not of high priority. As a result, various redundant processing to suppress the effects of communication interference on normal data B is no longer required, and it is possible to prevent a decrease in frequency utilization efficiency.

[0038] Furthermore, when transmitting two or more packet data, the first device 11 can also generate and transmit packet data that includes both normal data B and priority data A. In this case, communication interference of priority data A can be prevented without increasing the number of packet data.

[0039] The present invention is not limited to the embodiments described above, and when transmitting two or more packet data, the degree of communication interference may be checked in advance. In such cases, as shown in Figure 6, the first device 11 first transmits the first packet data, including priority data A, to the second device 12. If the second device 12 successfully receives this packet data, it sends an acknowledgment (Ack) back to the first device 11. After transmitting the first packet data, the first device 11 waits for the Ack to be received within a predetermined time.

[0040] As a result, as shown in Figure 6(a), if the first device 11 receives an Ack within a predetermined time Tw, it can recognize that priority data A has been successfully received by the second device 12 through the first packet data, and in this case, it does not transmit the second packet data. On the other hand, as shown in Figure 6(b), if the first device 11 does not receive an Ack within a predetermined time, it can recognize that priority data A has not been received by the second device 12 through the first packet data due to communication interference.

[0041] In such cases, the priority data A is included in the second packet data and then retransmitted. This reduces the transmission of unnecessary packet data if the priority data A is received by the second device 12 through the first packet data, and increases the likelihood that the priority data will be accurately received by the second device 12 through the second packet data if the priority data A is not received by the second device 12 through the first packet data.

[0042] In the embodiments described above, the processing operations in the first device 11 and the second device 12, to which CS2 and each node 3, which are communication devices compliant with the IEEE 802.15.4 standard, are applied, were used as examples for explanation. However, the invention is not limited to these. In other words, any communication device that performs wireless communication other than the IEEE 802.15.4 standard may be applied to the first device 11 and the second device 12 described above, and the processing operations may be performed accordingly.

[0043] It should be noted that the wireless communication system 1 to which the present invention is applied is not limited to the embodiments described above. For example, as shown in Figure 7, in addition to the first device 11 and the second device 12 described above, a third device 13 may be included, and the wireless communication system 1 may be realized as a system that performs wireless communication between three or more devices 11, 12, and 13. In such a case, the first device 11 receives data transmitted from the third device 13 and transmits it to the second device 11. That is, the system is such that the first device 11 relays wireless data transmission from the third device 13 to the second device 11.

[0044] In such a case, the first device 11 considers all data transmitted from the third device 13 as priority data A, duplicates it in the same manner as described above, and generates two or more independent packet data sets, each containing priority data A. The first device 11 may then sequentially transmit each of the generated packet data sets to the second device 12 with time intervals between them.

[0045] In addition to the method described above, the first device 11 may also determine whether the data transmitted from the third device 13 is priority data A. The data sent from the third device 13 may include data of low urgency. For this reason, the first device 11 determines each time whether the data sent from the third device 13 is priority data A. This determination of whether or not it is priority data A is done by preparing a template in advance which lists priority data A, and each time data is sent from the third device 13, the first device 11 refers to this template and determines whether or not it is priority data A. If the first device 11 determines that the data sent from the third device 13 is priority data A, it duplicates it and generates two or more independent packet data containing these priority data A packets. Then, each of the generated packet data is sent sequentially to the second device 12 with a time interval between them.

[0046] Similarly, in the example shown in Figure 7, it is certainly possible to check the degree of communication interference in advance when transmitting two or more packets of data, as shown in Figure 6. [Examples]

[0047] To confirm the effects of the wireless communication system 1 to which the present invention is applied, the verification described below was performed. In this verification, under poor communication conditions, packet data including priority data A was transmitted from a communication device representing the first device 11 to a communication device representing the second device 12, and the communication success rate against the frame error rate was investigated as shown in Figure 8. In the example of the present invention, packet data including priority data A is transmitted twice with a time interval between them, whereas in the comparative example, priority data A is transmitted only once, as in the conventional method.

[0048] As a result, it can be seen that the present invention, compared to the comparative example, is able to dramatically increase the communication success rate for each frame error rate. Furthermore, it has been shown that the volume of consecutive calls has also been similarly improved. [Explanation of symbols]

[0049] 1. Wireless communication system 2 devices 3 nodes 11. First device 12. Second device 13. The third device 15. Communication equipment

Claims

1. A wireless communication system including a wireless communication network for performing wireless communication between at least a first device and a second device, When transmitting prioritized data with a higher priority, the first device copies the prioritized data, generates two or more mutually independent packet data each including the prioritized data, and sequentially transmits the generated packet data to the second device with a time interval between them. A wireless communication system comprising:

2. The first device generates at least one packet data including the priority data as well as other data.

2. The wireless communication system according to claim 1, wherein:

3. A wireless communication system including a wireless communication network for performing wireless communication between at least a first device and a second device, The first device is When transmitting prioritized data having a higher priority, the prioritized data is duplicated, packet data including the duplicated prioritized data is generated, and the generated packet data is transmitted to the second device; If a reception confirmation notice of the packet data is not received from the second device within a predetermined time, further packet data including the priority data is generated, and the generated packet data is transmitted to the second device. A wireless communication system comprising:

4. The first device generates the packet data including the priority data as well as other data.

4. The wireless communication system according to claim 3, wherein:

5. In a wireless communication system including a wireless communication network for wireless communication between at least three or more devices, The first device is provided which, when data is transmitted from a third device, regards the data as priority data, copies the data, generates two or more mutually independent packet data each including the priority data, and sequentially transmits the generated packet data to the second device with a time interval between them. A wireless communication system comprising:

6. In a wireless communication system including a wireless communication network for wireless communication between at least three or more devices, The first device is provided which, when it is determined that the data transmitted from the third device is priority data, copies the priority data, generates two or more mutually independent packet data each including the priority data, and sequentially transmits the generated packet data to the second device with a time interval between them. A wireless communication system comprising:

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