Radio communication device, radio communication system, and radio communication method

Abstract

This radio communication device comprises: a plurality of radio communication units for communicating with different radio communication devices; and a communication control unit for controlling at least one radio communication unit among the plurality of radio communication units so as to cause said at least one radio communication unit to search for a radio communication device that is other than the radio communication device connected to said at least one radio communication unit, and that satisfies a prescribed condition in which quality information about a radio communication line connected to said at least one radio communication unit indicates that the communication quality is good.　

Description

Wireless communication device, wireless communication system, and wireless communication method

[0001] The present invention relates to a wireless communication device, a wireless communication system, and a wireless communication method.

[0002] Wireless communication using high frequency bands such as millimeter waves can ensure a wider bandwidth than wireless communication using microwaves. IEEE 802.11ad is an example of a wireless communication method using high frequency bands. Wireless communication using high frequency bands has advantages such as high linearity of wireless signals in propagation paths and less interference with other wireless communication. Therefore, studies are underway to popularize wireless communication using high frequency bands (see, for example, Non-Patent Document 1).

[0003] The distance attenuation of a radio signal in a propagation path increases with the frequency of the radio signal. Radio signals in wireless communications using the 60 GHz band, such as IEEE 802.11ad, are easily absorbed by oxygen in the propagation path. For this reason, in wireless communications using high frequency bands such as millimeter waves, a wireless communication device typically forms a directional beam (beamforming) toward a wireless communication device with which it is communicating, and transmits the signal. It is also common for wireless communication devices to form a directional beam and receive the signal (see, for example, Non-Patent Document 2).

[0004] International Publication No. 2022 / 024241

[0005] Takinami et al., "Standardization Trends and Elemental Technologies of Millimeter-Wave Wireless LAN Systems," IEICE Communications Society Magazine, Fall 2016, No. 38, pp. 100-106. IEEE, "Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 3: Enhancements for Very High Throughput in the 60 GHz Band" (IEEE Std 802.11ad-2012), December 28, 2012.

[0006] In wireless communication systems using high frequency bands, communication is performed using directional beams, which poses a problem of rapid degradation of wireless transmission characteristics due to mismatches in the orientation of the antennas of the wireless communication devices communicating and the presence of obstructions on the communication path. Fig. 6 is a diagram showing an example of a wireless communication system in which a base station device 1 installed on the ground communicates with a terminal device 2 installed on a robot cart R. In the situation shown in Fig. 6, the antennas of the base station device 1 and the terminal device 2 are directly facing each other, so wireless communication with high communication quality can be expected.

[0007] On the other hand, as shown in Figure 7, it is assumed that as the robot cart R moves, the antennas of the base station device 1-1 and the terminal device 2 will no longer face each other. For example, under the conditions shown in Figure 7, it is difficult for the antennas of the opposing wireless communication device to be directly visible from the antennas of the base station device 1-1 and the terminal device 2. Under such conditions, if there is a reflecting object W such as a wall shown in Figure 7, communication may be possible through the reflected path shown by the dotted line, but communication is not possible if there is no reflecting object W.

[0008] Furthermore, depending on the material of the reflector W, radio waves may be absorbed, resulting in a deterioration in communication quality compared to when the antenna is directly facing the object. Thus, in high frequency bands, the combination of antenna orientations of wireless communication devices can significantly degrade communication characteristics, resulting in unstable communication.

[0009] Incidentally, under conditions where a large number of base station devices are installed, it is conceivable that another base station device 1-2 may be present in the direction of the antenna of the terminal device 2 as the robot cart R moves, as shown in Fig. 7, or that another base station device 1-3 may be present near the base station device 1-1 to which the terminal device 2 was initially connected, as shown in Fig. 8. The terminal device 2 may be equipped with a scanning function that, while connected to a specific base station device (for example, base station device 1-1), scans the surrounding environment to search for other base station devices 1 with good quality.

[0010] However, because a typical terminal device 2 has only one wireless communication unit, it has the following two problems. The first problem is that communication may be interrupted during a scanning operation. In other words, because the wireless communication unit of the terminal device 2 is used to scan the surrounding environment, communication with the currently connected base station device 1 may be temporarily lost. The second problem is that even if another base station device 1 with better quality is found, when connecting to that base station device, the connection with the original base station device 1 must be temporarily disconnected and then the new base station device must be connected. In this way, when a typical terminal device 2 switches its connection to another base station device 1 with better quality, communication may be interrupted between the base station device 1 and its upper network.

[0011] 9, by providing the terminal device 2 with multiple wireless communication units, it is possible to provide redundancy for the wireless communication links, and when the quality of one wireless communication link deteriorates, it is possible to cope with a deterioration in wireless communication quality by performing communication using the remaining wireless communication link. Furthermore, as shown in Patent Document 1, it is possible to improve the stability of wireless communication by controlling so that multiple wireless communication units are not connected to the same base station device.

[0012] However, even if the terminal device 2 is equipped with multiple wireless communication units, if the wireless communication quality of both of the multiple wireless communication units simultaneously deteriorates, for example, when the robot cart R rotates as shown in Fig. 9, unless the multiple wireless communication units are appropriately controlled, such as by using the quality deterioration as a trigger to search for another base station device 1 with better quality, there is a possibility that communication with the base station device 1 or its upper network will be temporarily interrupted. As a result, there is a problem in that the quality of the wireless communication link deteriorates.

[0013] In view of the above circumstances, an object of the present invention is to provide a technique capable of suppressing degradation in the quality of a wireless communication link when a wireless communication device includes a plurality of wireless communication units.

[0014] One aspect of the present invention is a wireless communication device comprising: a plurality of wireless communication units that communicate with different wireless communication devices; and a communication control unit that controls at least one of the plurality of wireless communication units to search for a wireless communication device other than the wireless communication device to which the at least one wireless communication unit is connected, where quality information of the wireless communication line between the at least one wireless communication unit and the at least one wireless communication unit satisfies predetermined conditions indicating good communication quality.

[0015] One aspect of the present invention is a wireless communication system comprising a first wireless communication device and a plurality of second wireless communication devices that communicate with the first wireless communication device, wherein the first wireless communication device comprises a plurality of wireless communication units that communicate with the plurality of second wireless communication devices, and a communication control unit that controls at least one of the plurality of wireless communication units to search for a wireless communication device other than the second wireless communication device to which the at least one wireless communication unit is connected, where quality information of the wireless communication line between the at least one wireless communication unit satisfies predetermined conditions indicating good communication quality, and the plurality of second wireless communication devices comprise one or more wireless communication units that communicate with the first wireless communication device.

[0016] One aspect of the present invention is a wireless communication method that controls at least one of multiple wireless communication units that communicate with different wireless communication devices, and searches for a wireless communication device other than the wireless communication device to which the at least one wireless communication unit is connected, where quality information of the wireless communication line between the at least one wireless communication unit and the at least one wireless communication unit satisfies predetermined conditions indicating good communication quality.

[0017] According to the present invention, it is possible to suppress degradation in the quality of a wireless communication link when a wireless communication device is equipped with a plurality of wireless communication units.

[0018] 1 is a diagram illustrating an example of the configuration of a wireless communication device in a first embodiment. FIG. 2 is a flowchart illustrating the processing flow of a wireless communication device in a first modified example of the first embodiment. FIG. 3 is a flowchart illustrating the processing flow of a wireless communication device in a second embodiment. FIG. 4 is a flowchart illustrating the processing flow of a wireless communication device in a second modified example of the second embodiment. FIG. 5 is a diagram illustrating an example of a wireless communication system in which a base station device installed on the ground and a terminal device installed on a robot cart communicate with each other. FIG. 6 is a diagram illustrating an example of a wireless communication system in which a base station device installed on the ground and a terminal device installed on a robot cart communicate with each other. FIG. 7 is a diagram illustrating an example of a wireless communication system in which a base station device installed on the ground and a terminal device installed on a robot cart communicate with each other. FIG. 8 is a diagram illustrating an example of a wireless communication system in which a base station device installed on the ground and a terminal device installed on a robot cart communicate with each other.

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] (First embodiment) Fig. 1 is a diagram showing an example of the configuration of a wireless communication device 10 in a first embodiment. The wireless communication device 10 includes multiple wireless communication units and performs wireless communication with multiple other wireless communication devices. As an example, the wireless communication device 10 is described as a terminal station device, and the multiple other wireless communication devices are base station devices. The wireless communication device 10 and the multiple other wireless communication devices are provided in a wireless communication system. The multiple other wireless communication devices include one or more wireless communication units and perform wireless communication with the wireless communication device 10.

[0021] It should be noted that the wireless communication device 10 may be a base station device, and the multiple other wireless communication devices may be terminal station devices. When the wireless communication device 10 is a base station device, the configuration of the base station device is the same as that of the wireless communication device 10. The wireless communication device 10 is one aspect of a first wireless communication device, and the multiple other wireless communication devices are one aspect of a multiple second wireless communication devices.

[0022] The wireless communication device 10 includes a data processing unit 11, multiple wireless communication units 12-1 and 12-2, a quality information collecting unit 13, a communication control unit 14, and multiple antennas 15-1 and 15-2. Note that while Fig. 1 shows a configuration in which the wireless communication device 10 includes two wireless communication units 12 and two antennas 15, the wireless communication device 10 may also be configured to include three or more wireless communication units 12 and three or more antennas 15. In the following description, the multiple wireless communication units 12-1 and 12-2 will be referred to as wireless communication units 12 unless otherwise specified, and the multiple antennas 15-1 and 15-2 will be referred to as antennas 15 unless otherwise specified.

[0023] The data processing unit 11 inputs and outputs data to and from a higher-level device or another base station that is located above the wireless communication device 10. For example, the data processing unit 11 transmits a signal received from another wireless communication device to the higher-level device or another base station. For example, the data processing unit 11 receives a signal addressed to another wireless communication device from the higher-level device or another base station.

[0024] Each wireless communication unit 12 communicates with a different wireless communication device. In accordance with instructions from the communication control unit 14, the wireless communication unit 12 controls the amplitude or phase of the antenna 15 to form directional beams in different directions. Note that the number of directional beams formed by the wireless communication device 10 is not particularly limited. A directional beam is a beam that has directivity in a specific direction. In accordance with instructions from the communication control unit 14, the wireless communication unit 12 switches the directional beam and transmits a signal. The wireless communication unit 12 receives a signal (e.g., a response) transmitted from the wireless communication device 20 via the antenna 15.

[0025] Furthermore, the wireless communication unit 12 searches for other wireless communication devices located around the wireless communication device 10 by scanning surrounding radio waves under the control of the communication control unit 14. Hereinafter, the process of searching for other wireless communication devices performed by the wireless communication unit 12 will be referred to as a scanning operation.

[0026] The quality information collecting unit 13 collects quality information of wireless communication links connected to each wireless communication unit 12. The quality information is information related to wireless communication quality, and may be, for example, a received signal strength indication (RSSI) of a reference signal transmitted from another wireless communication device obtained when the wireless communication device 10 selects a directional beam, a signal-to-noise ratio (SNR) obtained by estimating received signal power and noise, information for identifying which directional beam was actually used in communication, such as the ID of the directional beam, or information on transmission distance obtained by a distance estimation function (e.g., estimation of transmission distance based on RTT: Round-Trip Time), or a combination thereof.

[0027] Furthermore, the quality information collecting unit 13 also collects quality information of other wireless communication devices located around the wireless communication device 10 and information required for connecting to and communicating with other wireless communication devices (hereinafter referred to as "connection information") as search results of the scanning operation by the wireless communication unit 12. For example, the quality information collecting unit 13 collects, as quality information, the received signal strength of signals transmitted from other wireless communication devices located around the wireless communication device 10. The connection information includes, for example, identifiers of other wireless communication devices, specifically, BSSIDs (Basic Service Set Identifiers) in the case of wireless local area networks (LANs) and cell IDs in the case of 5G.

[0028] The communication control unit 14 controls each wireless communication unit 12. The communication control unit 14 selects a wireless communication unit 12 to be used for communication from among the plurality of wireless communication units 12, for example, based on quality information of each wireless communication unit 12 collected by the quality information collection unit 13. The communication control unit 14 selects, from among the plurality of wireless communication units 12, for example, the wireless communication unit 12 having the best wireless communication quality indicated by the quality information as the wireless communication unit 12 to be used for communication.

[0029] Furthermore, the communication control unit 14 controls at least one wireless communication unit 12 other than the selected wireless communication unit 12 to search for another wireless communication device (hereinafter referred to as a "new connection destination device") that is a wireless communication device other than the wireless communication device to which the at least one wireless communication unit 12 other than the selected wireless communication unit 12 connects, and for which quality information of the wireless communication line between the at least one wireless communication unit 12 other than the selected wireless communication unit 12 satisfies predetermined conditions indicating good communication quality.

[0030] The predetermined condition may be, for example, if the quality information is received signal strength, that the received signal strength is equal to or greater than a threshold value. Alternatively, if the quality information is received signal strength, that the signal-to-noise power ratio is equal to or greater than a threshold value. Alternatively, if the quality information is received signal strength, that the received signal strength of the new connection destination device may be higher than the received signal strength of a wireless communication device connected to at least one wireless communication unit 12 other than the selected wireless communication unit 12. Alternatively, if the quality information is signal-to-noise power ratio, that the signal-to-noise power ratio of the new connection destination device may be higher than the signal-to-noise power ratio of a wireless communication device connected to at least one wireless communication unit 12 other than the selected wireless communication unit 12. In the following description, an example will be described in which the predetermined condition is that the received signal strength of the new connection destination device is higher than the received signal strength of a wireless communication device connected to at least one wireless communication unit 12 other than the selected wireless communication unit 12.

[0031] As described above, the communication control unit 14 causes at least one wireless communication unit 12 other than the selected wireless communication unit 12 to perform a scanning operation. As a result, the communication control unit 14 determines whether a new destination device exists. If a new destination device exists, the communication control unit 14 controls at least one wireless communication unit 12 other than the selected wireless communication unit 12 to connect to the new destination device. For example, the communication control unit 14 disconnects the wireless communication link of the wireless communication unit 12 that has searched for the new destination device by the scanning operation, and instructs the wireless communication unit 12 whose wireless communication link has been disconnected to connect to the new destination device.

[0032] The antenna 15 is provided in association with the wireless communication unit 12. The antenna 15 forms directional beams in different directions under the control of the wireless communication unit 12. The antenna 15 transmits signals by emitting radio waves using the formed directional beams. The antenna 15 receives radio waves transmitted from other wireless communication devices using the formed directional beams.

[0033] 2 is a flowchart showing the flow of processing in the wireless communication device 10 according to the first embodiment. In the explanation of FIG. 2, the other wireless communication devices to which the wireless communication units 12-1 and 12-2 of the wireless communication device 10 connect are described as wireless communication devices 20-1 and 20-2.

[0034] The communication control unit 14 acquires quality information of the wireless communication links of the wireless communication units 12-1 and 12-2 via the quality information collection unit 13 (step S101). For example, the communication control unit 14 acquires quality information of the wireless communication link between the wireless communication unit 12-1 and the wireless communication device 20-1, and acquires quality information of the wireless communication link between the wireless communication unit 12-2 and the other wireless communication device 20-2.

[0035] The communication control unit 14 determines whether acquisition of quality information has been completed for each wireless communication unit 12 (step S102). For example, the communication control unit 14 determines that acquisition of quality information has been completed when quality information has been acquired for all wireless communication units 12 connected to different wireless communication devices 20. For example, the communication control unit 14 determines that acquisition of quality information has not been completed when quality information has not been acquired for all wireless communication units 12 connected to different wireless communication devices 20.

[0036] If the communication control unit 14 determines that acquisition of quality information has not been completed for each wireless communication unit 12 (step S102—NO), the process returns to step S101. If the communication control unit 14 determines that acquisition of quality information has been completed for each wireless communication unit 12 (step S102—YES), the communication control unit 14 identifies the wireless communication unit 12 communicating via the wireless communication link with the highest communication quality based on the acquired quality information. Here, as an example, it is assumed that wireless communication unit 12-1 is the wireless communication unit 12 communicating via the wireless communication link with the highest communication quality.

[0037] The communication control unit 14 marks the identified wireless communication unit 12 (e.g., wireless communication unit 12-1) for use in communication (step S103). In this way, the communication control unit 14 selects the identified wireless communication unit 12 (e.g., wireless communication unit 12-1) as the wireless communication unit 12 to be used for communication. Thereafter, the communication control unit 14 determines whether the number N (N is an integer equal to or greater than 0) of wireless communication units 12 connected to each wireless communication device 20 is greater than 1 (step S104). If the communication control unit 14 determines that the number N of wireless communication units 12 connected to each wireless communication device 20 is less than 1 (step S104—NO), the process returns to step S101.

[0038] On the other hand, if the communication control unit 14 determines that the number N of wireless communication units 12 connected to each wireless communication device 20 is greater than 1 (step S104—YES), the wireless communication device 10 initializes the constant i (step S105). Thereafter, the communication control unit 14 adds “1” to the constant i to set a new constant i (step S106). Next, the communication control unit 14 determines whether the i-th wireless communication unit 12-i connected to the wireless communication device 20 is marked for use in communication (step S107).

[0039] When i=1, the communication control unit 14 determines whether the first wireless communication unit 12-1 connected to the wireless communication device 20 (e.g., wireless communication device 20-1) is marked for use in communication. As described above, if the wireless communication unit 12-1 is marked for use in communication, the communication control unit 14 determines that the first wireless communication unit 12-1 connected to the wireless communication device 20 (e.g., wireless communication device 20-1) is marked for use in communication. If the wireless communication unit 12-2 is marked for use in communication, the communication control unit 14 determines that the first wireless communication unit 12-1 connected to the wireless communication device 20 (e.g., wireless communication device 20-1) is not marked for use in communication.

[0040] If the communication control unit 14 determines that the i-th wireless communication unit 12-i connected to the wireless communication device 20 is marked for use in communication (step S107-YES), the communication control unit 14 determines whether the constant i is the same as the number N of wireless communication units 12 connected to each wireless communication device 20 (step S108).

[0041] If the communication control unit 14 determines that the constant i is equal to the number N of wireless communication units 12 connected to each wireless communication device 20 (YES in step S108), the process returns to step S101. Note that if the communication control unit 14 determines that the constant i is equal to the number N of wireless communication units 12 connected to each wireless communication device 20, the wireless communication device 10 may end the process shown in FIG. 2 once and execute the process of step S101 after a predetermined time has elapsed.

[0042] On the other hand, if the communication control unit 14 determines that the constant i is not the same as the number N of wireless communication units 12 connected to each wireless communication device 20 (step S108—NO), the process returns to step S106. That is, if the communication control unit 14 determines that the constant i is not the same as the number N of wireless communication units 12 connected to each wireless communication device 20, the communication control unit 14 adds “1” to the constant i to create a new constant i. In this manner, the communication control unit 14 determines whether all wireless communication units 12 connected to the wireless communication device 20 are marked as being used for communication. Furthermore, the communication control unit 14 causes the wireless communication units 12 that are not marked as being used for communication, out of all wireless communication units 12 connected to the wireless communication device 20, to perform a scanning operation, as described below.

[0043] In the process of step S107, if the communication control unit 14 determines that the i-th wireless communication unit 12-i connected to the wireless communication device 20 is not marked for communication (step S107—NO), the communication control unit 14 causes the i-th wireless communication unit 12-i to search to find whether a new connection destination device exists (step S109). At this time, the communication control unit 14 causes the i-th wireless communication unit 12-i to perform a scanning operation. The i-th wireless communication unit 12-i performs the scanning operation in accordance with instructions from the communication control unit 14. Through this process, if other wireless communication devices 20 exist in the vicinity of the i-th wireless communication unit 12-i, the wireless communication device 10 can obtain quality information and connection information from each of the wireless communication devices 20 in the vicinity. On the other hand, if no other wireless communication devices 20 exist in the vicinity of the i-th wireless communication unit 12-i, the wireless communication device 10 cannot obtain quality information and connection information.

[0044] When another wireless communication device 20 is found as a result of the scanning operation of the i-th wireless communication unit 12-i, the quality information collecting unit 13 collects quality information and connection information for each of the other wireless communication devices 20 found. The quality information collecting unit 13 outputs the collected quality information and connection information for each of the other wireless communication devices 20 to the communication control unit 14. The communication control unit 14 determines whether or not a new connection destination device exists based on the quality information for each of the other wireless communication devices 20 output from the quality information collecting unit 13 (step S110). That is, the communication control unit 14 determines whether or not another wireless communication device 20 exists whose quality information satisfies a predetermined condition based on the quality information for each of the other wireless communication devices 20.

[0045] When the quality information is the received signal strength, the communication control unit 14 compares the received signal strength of the wireless communication device 20 to which the i-th wireless communication unit 12-i is connected with the received signal strength of other wireless communication devices 20 found by the scanning operation. When multiple other wireless communication devices 20 are found by the scanning operation, the communication control unit 14 compares the received signal strength of the wireless communication device 20 to which the i-th wireless communication unit 12-i is connected with the received signal strength of each of the other wireless communication devices 20. When the received signal strength of the other wireless communication device 20 is higher than the received signal strength of the wireless communication device 20 to which the i-th wireless communication unit 12-i is connected, the communication control unit 14 determines that there is another wireless communication device 20 that satisfies a predetermined condition.

[0046] Here, the communication control unit 14 determines that a new connection destination device exists if there is another wireless communication device 20 whose quality information satisfies a predetermined condition based on the quality information of each other wireless communication device 20. Note that the other wireless communication devices 20 whose quality information satisfies the predetermined condition do not include the wireless communication device 20 to which the i-th wireless communication unit 12-i is currently connected. On the other hand, the communication control unit 14 determines that a new connection destination device does not exist if there is no other wireless communication device 20 whose quality information satisfies the predetermined condition based on the quality information of each other wireless communication device 20.

[0047] If the communication control unit 14 determines that a new connection destination device does not exist (step S110—NO), the communication control unit 14 executes the process of step S108. On the other hand, if the communication control unit 14 determines that a new connection destination device exists (step S110—YES), the communication control unit 14 controls the i-th wireless communication unit 12-i connected to the wireless communication device 20 to disconnect the connection with the wireless communication device 20 with which it is currently communicating. For example, if the i-th wireless communication unit 12-i connected to the wireless communication device 20 is wireless communication unit 12-2, the communication control unit 14 controls the wireless communication unit 12-2 to disconnect the connection with the wireless communication device 20 (e.g., wireless communication device 20-2) with which it is currently communicating.

[0048] Thereafter, the communication control unit 14 instructs the i-th wireless communication unit 12-i to connect to the new connection destination device (step S111). Here, if there are multiple other wireless communication devices 20 whose quality information satisfies a predetermined condition, the communication control unit 14 may select the wireless communication device 20 with the highest received signal strength as the new connection destination device. In this case, the communication control unit 14 outputs connection information corresponding to the wireless communication device 20 with the highest received signal strength to the i-th wireless communication unit 12-i. As a result, the i-th wireless communication unit 12-i forms a wireless communication link with the new connection destination device using the connection information output from the communication control unit 14, and connects to enable communication. Note that if there are multiple new connection destination devices, the communication control unit 14 may select the other wireless communication device 20 with the highest quality as the new connection destination device. Then, the process of step S108 is executed.

[0049] The wireless communication device 10 configured as described above includes a plurality of wireless communication units 12 that communicate with other wireless communication devices, and a communication control unit 14 that controls at least one of the plurality of wireless communication units 12 to search for a wireless communication device other than the wireless communication device to which at least one wireless communication unit 12 is connected, where quality information of the wireless communication line between at least one wireless communication unit 12 and the at least one wireless communication unit 12 satisfies predetermined conditions indicating good communication quality.

[0050] Specifically, the communication control unit 14 of the wireless communication device 10 causes the wireless communication units 12 that are not marked for communication to perform a scanning operation to search for other wireless communication devices with good communication quality. This allows some wireless communication units 12 to immediately start an operation to detect other wireless communication devices with good quality while maintaining connections with other wireless communication devices. Therefore, it is possible to quickly detect new other wireless communication devices and switch the connection to other wireless communication devices with good quality without interrupting communication. Therefore, even when the wireless communication device 10 has multiple wireless communication units 12, it is possible to suppress degradation of the quality of the wireless communication link.

[0051] The communication control unit 14 controls at least one wireless communication unit 12 that is not marked for use in communication among the multiple wireless communication units 12 to search for a wireless communication device that satisfies a predetermined condition. This makes it possible to start an operation to search for other wireless communication devices with good quality while maintaining communication by the wireless communication unit 12 that is communicating with another wireless communication device via a wireless communication link with the highest communication quality. This makes it possible to communicate while maintaining good communication quality.

[0052] (Variation of the First Embodiment) Frequent scanning of the surrounding environment and switching of the wireless communication device in response to the scanning result may potentially cause the wireless communication unit 12 included in the wireless communication device 10 to become unable to communicate with all of the opposing wireless communication devices and their upper-level networks, for example, if the quality of the wireless communication link in the wireless communication unit 12 used for communication temporarily drops. Therefore, it may be possible to control the wireless communication device 10 to connect to an opposing wireless communication device with good quality obtained by scanning the surrounding environment only if the quality information of the opposing wireless communication device satisfies certain conditions.

[0053] 3 is a flowchart showing the flow of processing by the wireless communication device 10 in Modification 1 of the first embodiment. In the explanation of FIG. 3, the other wireless communication devices to which the wireless communication units 12-1 and 12-2 of the wireless communication device 10 connect will be explained as wireless communication devices 20-1 and 20-2. In FIG. 3, the same processes as those in FIG. 2 are assigned the same reference numerals as those in FIG. 2, and explanations thereof will be omitted.

[0054] In the process of step S110, if the communication control unit 14 determines that a new destination device exists (step S110-YES), the communication control unit 14 determines, based on the quality information obtained from the new destination device, whether or not the quality of the new destination device satisfies a condition indicating that the quality of the new destination device is better than that of the currently connected wireless communication device (step S151). For example, when the received signal strength is used as the quality information, the condition is that both of the following formulas (1) and (2) are satisfied.

[0055]

[0056]

[0057] RSSI in Equation (1) and Equation (2) Ｓ＿ｎｏｗ represents the received signal strength obtained between a wireless communication unit 12 other than the wireless communication unit 12 marked for use in communication and a wireless communication device to which the wireless communication unit 12 is currently connected, α in equation (1) represents a threshold, and RSSI in equation (2) Ｓ＿ｎｅｗ represents the received signal strength obtained with the new destination device, and β in equation (2) represents a threshold value. Note that the threshold values ​​α and β are values ​​given by setting.

[0058] The conditions shown in equations (1) and (2) mean that the connection of the wireless communication unit 12 that is not being used for communication will be switched in the hope of improving quality only when the quality of the wireless communication unit 12 with the currently connected wireless communication device is lower than a certain level and the quality of the new connection destination device is higher than a certain level than that of the currently connected wireless communication device.

[0059] If the communication control unit 14 determines that the condition indicating that the quality of the new connection destination device is better than that of the currently connected wireless communication device is not met (step S151—NO), the processing of step S108 is executed. On the other hand, if the communication control unit 14 determines that the condition indicating that the quality of the new connection destination device is better than that of the currently connected wireless communication device is met (step S151—YES), the communication control unit 14 controls the i-th wireless communication unit 12-i connected to the wireless communication device 20 to disconnect the connection with the wireless communication device 20 with which it is currently communicating. For example, if the i-th wireless communication unit 12-i connected to the wireless communication device 20 is the wireless communication unit 12-2, the communication control unit 14 controls the wireless communication unit 12-2 to disconnect the connection with the wireless communication device 20 (e.g., the wireless communication device 20-2) with which it is currently communicating.

[0060] Thereafter, the communication control unit 14 instructs the i-th wireless communication unit 12-i to connect to the new destination device (step S152). This configuration makes it possible to switch the connection with the opposite wireless communication device only when necessary, without having to do so frequently.

[0061] Second Embodiment In the first embodiment, a configuration was described in which a scanning operation is performed on wireless communication units other than the wireless communication unit used for communication (a wireless communication unit marked for use in communication). This is to detect other wireless communication devices for each wireless communication unit and attempt to improve communication quality. However, this scanning operation may temporarily interrupt communication in the wireless communication unit performing the scanning operation. Therefore, if the quality of the communication link in the wireless communication unit used for communication temporarily deteriorates, all wireless communication units included in the wireless communication device may become unable to communicate. Therefore, in the second embodiment, a configuration is described in which the execution of a scanning operation of wireless communication units other than the wireless communication unit used for communication is controlled based on quality information of the wireless communication unit used for communication. For example, a scanning operation of wireless communication units other than the wireless communication unit used for communication is performed only when the communication quality of the wireless communication unit used for communication deteriorates.

[0062] In the second embodiment, the configuration of the wireless communication device 10 is the same as that of the first embodiment, except for the processing performed by the wireless communication device 10. The following description will focus on the differences.

[0063] The communication control unit 14 controls each wireless communication unit 12. The communication control unit 14 selects a wireless communication unit 12 to be used for communication from among the plurality of wireless communication units 12, for example, based on quality information of each wireless communication unit 12 collected by the quality information collection unit 13. The communication control unit 14 selects, from among the plurality of wireless communication units 12, for example, the wireless communication unit 12 having the best wireless communication quality indicated by the quality information as the wireless communication unit 12 to be used for communication.

[0064] Furthermore, when the quality information of the selected wireless communication unit 12 does not satisfy the quality condition, the communication control unit 14 causes at least one wireless communication unit 12 other than the selected wireless communication unit 12 to search for a new destination device. The quality condition is a condition related to wireless communication quality, such as good communication quality. More specifically, when the quality information is the received signal strength of a reference signal, the quality condition may be that the received signal strength of the reference signal is equal to or greater than a threshold, or when the quality information is the signal-to-noise power ratio, the quality condition may be that the signal-to-noise power ratio is equal to or greater than a threshold.

[0065] When a new destination device is present, the communication control unit 14 controls at least one wireless communication unit 12 other than the selected wireless communication unit 12 to connect to the new destination device. For example, the communication control unit 14 disconnects the wireless communication link of the wireless communication unit 12 that has searched for the new destination device by a scanning operation, and instructs the wireless communication unit 12 that has disconnected the wireless communication link to connect to the new destination device.

[0066] As described above, in the second embodiment, when the quality information of the selected wireless communication unit 12 does not satisfy the quality conditions, i.e., when the communication quality is poor, the communication control unit 14 causes at least one wireless communication unit 12 other than the selected wireless communication unit 12 to search for whether a new connection destination device exists.

[0067] 4 is a flowchart showing the flow of processing in the wireless communication device 10 in the second embodiment. In the explanation of FIG. 4, the other wireless communication devices to which the wireless communication units 12-1 and 12-2 of the wireless communication device 10 connect will be explained as wireless communication devices 20-1 and 20-2. In FIG. 4, the same processes as those in FIG. 2 are assigned the same reference numerals as those in FIG. 2, and explanations thereof will be omitted.

[0068] When the processes from step S101 to step S103 are completed, the communication control unit 14 determines whether the quality information of the wireless communication unit 12 marked to be used for communication in the process of step S103 satisfies the quality conditions (step S201). If the communication control unit 14 determines that the quality information of the wireless communication unit 12 marked to be used for communication satisfies the quality conditions (step S201-YES), the process returns to step S101. The determination that the quality information of the wireless communication unit 12 marked to be used for communication satisfies the quality conditions means that the communication quality of the wireless communication unit 12 marked to be used for communication is in a good state.

[0069] On the other hand, if the communication control unit 14 determines that the quality information of the wireless communication unit 12 marked to be used for communication does not satisfy the quality conditions (step S201-NO), the processing from step S104 onwards is executed. The fact that it is determined that the quality information of the wireless communication unit 12 marked to be used for communication does not satisfy the quality conditions means that the communication quality of the wireless communication unit 12 marked to be used for communication is bad (a state in which the communication quality is degraded).

[0070] According to the wireless communication device 10 of the second embodiment configured as described above, only when the communication quality of the wireless communication unit 12 used for communication has deteriorated, a scanning operation can be performed on the wireless communication units 12 other than the wireless communication unit 12 used for communication. This makes it possible to immediately start an operation to detect other wireless communication devices with better communication quality while maintaining a connection with the other wireless communication devices. Therefore, it is possible to quickly detect new other wireless communication devices and maintain the quality of the wireless communication link. Therefore, even when the wireless communication device 10 includes multiple wireless communication units 12, it is possible to suppress deterioration in the quality of the wireless communication link.

[0071] (Variation 1 of the Second Embodiment) In the above-described embodiment, a configuration has been described in which, when the communication quality of a wireless communication unit 12 marked to be used for communication falls below a certain level (when the quality information does not satisfy the quality condition), that is, when there is a risk that the communication quality of both of the multiple wireless communication units 12 (the wireless communication units 12 marked to be used for communication and the wireless communication units 12 not used for communication) will decrease, the wireless communication units 12 not used for communication are caused to scan the surrounding environment. However, when the communication quality of the wireless communication unit 12 marked to be used for communication is above a certain level, that is, when it is expected that the communication will remain stable for a while, it is also possible to cause the wireless communication unit 12 not used for communication to scan the surrounding environment and detect in advance other wireless communication devices with good communication quality.

[0072] Therefore, when the communication control unit 14 determines in the processing of step S201 that the quality information of the wireless communication unit 12 marked for use in communication satisfies the quality condition (step S201—YES) and when it is expected that the stable communication state will continue for a while, it may perform a scanning operation on the wireless communication units 12 other than the wireless communication unit 12 marked for use in communication. In this configuration, the communication control unit 14 performs a scanning operation on the wireless communication units 12 other than the wireless communication unit 12 marked for use in communication to detect a new connection destination device. The communication control unit 14 retains, for a certain period of time, information on the new connection destination device detected for each wireless communication unit 12 other than the wireless communication unit 12 marked for use in communication. Then, when the quality information of the wireless communication unit 12 marked for use in communication no longer satisfies the quality condition, the communication control unit 14 may use the retained information to instruct each wireless communication unit 12 other than the wireless communication unit 12 marked for use in communication to connect to the new connection destination device without issuing an instruction to perform a scanning operation. The communication control unit 14 may discard information about a new connection destination device for which a certain period of time has elapsed since the time the information was held, and may execute the scanning operation again.

[0073] (Variation 2 of the Second Embodiment) Frequent scanning of the surrounding environment and switching of the wireless communication device in response to the scanning result may potentially cause the wireless communication unit 12 included in the wireless communication device 10 to be unable to communicate with all of the opposing wireless communication devices and their upper-level networks, for example, if the quality of the wireless communication link in the wireless communication unit 12 used for communication temporarily drops. Therefore, it may be possible to control the wireless communication device 10 to connect to an opposing wireless communication device with good quality obtained by scanning the surrounding environment only if the quality information of the opposing wireless communication device satisfies certain conditions.

[0074] 5 is a flowchart showing the flow of processing by the wireless communication device 10 in Modification 2 of the second embodiment. In the explanation of Fig. 5, the other wireless communication devices to which the wireless communication units 12-1 and 12-2 of the wireless communication device 10 connect will be explained as wireless communication devices 20-1 and 20-2. In Fig. 5, the same processes as those in Fig. 4 are assigned the same reference numerals as those in Fig. 4, and explanations thereof will be omitted.

[0075] In the process of step S110, if the communication control unit 14 determines that a new destination device exists (step S110-YES), the communication control unit 14 determines, based on the quality information obtained from the new destination device, whether or not the quality of the new destination device satisfies a condition indicating that the quality of the new destination device is better than that of the currently connected wireless communication device (step S251). For example, if the received signal strength is used as the quality information, the condition is that both of the above-mentioned formulas (1) and (2) are satisfied.

[0076] If the communication control unit 14 determines that the condition indicating that the quality of the new connection destination device is better than that of the currently connected wireless communication device is not met (step S251—NO), the processing of step S108 is executed. On the other hand, if the communication control unit 14 determines that the condition indicating that the quality of the new connection destination device is better than that of the currently connected wireless communication device is met (step S251—YES), the communication control unit 14 controls the i-th wireless communication unit 12-i connected to the wireless communication device 20 to disconnect the connection with the wireless communication device 20 with which it is currently communicating. For example, if the i-th wireless communication unit 12-i connected to the wireless communication device 20 is the wireless communication unit 12-2, the communication control unit 14 controls the wireless communication unit 12-2 to disconnect the connection with the wireless communication device 20 (e.g., the wireless communication device 20-2) with which it is currently communicating.

[0077] Thereafter, the communication control unit 14 instructs the i-th wireless communication unit 12-i to connect to the new destination device (step S252). This configuration makes it possible to switch the connection with the opposite wireless communication device only when necessary, without having to do so frequently.

[0078] (Modification 1 common to the first and second embodiments) In each embodiment, a configuration has been shown in which a scanning operation is not performed on a wireless communication unit 12 marked to be used for communication. However, in order to make it easier to detect other wireless communication devices that are expected to have good wireless communication quality, a scanning operation may also be performed on a wireless communication unit 12 marked to be used for communication. In such a configuration, communication is performed with the opposing wireless communication device using the wireless communication unit 12 with the next best quality to the wireless communication unit 12 marked to be used for communication. Furthermore, in such a configuration, when configured as Modification 1 of the first embodiment or Modification 2 of the second embodiment, the RSSI in the above-mentioned formulas (1) and (2) is Ｓ＿ｎｏｗ is the received signal strength obtained between the wireless communication unit 12 marked for use in communication and the opposing wireless communication device to which the wireless communication unit 12 is currently connected. In this case, the connection with the opposing wireless communication device is switched depending on the quality information of the wireless communication unit 12 currently used for communication.

[0079] (Modification 2 common to the first and second embodiments) Each embodiment can be applied to any wireless communication system. That is, the present invention can be applied to any wireless communication system that uses directional beams, whether it is an autonomous distributed wireless communication system such as IEEE 802.11ad or a centralized control wireless communication system such as 5G (5th Generation) NR (New Radio).

[0080] (Modification 3 common to the first and second embodiments) In each embodiment, a configuration has been described in which the terminal device is provided with the communication control unit 14 and causes each wireless communication unit 12 to perform a scanning operation, but the communication control unit 14 may be arranged on the base station device side or in an upper network to perform control. A configuration in which the base station device is provided with multiple wireless communication units 12 and causes each wireless communication unit 12 to perform a scanning operation is also included in the present invention.

[0081] (Variant 4 common to the first and second embodiments) The multiple wireless communication units 12 provided in the wireless communication device 10 in each embodiment may conform to the same wireless communication standard, or each may correspond to a different wireless communication standard.

[0082] (Variant 5 common to the first and second embodiments) In each embodiment, a base station device installed on the ground and a terminal device equipped with multiple wireless communication units 12 installed on a robot cart have been described as examples, but the present invention is not limited to application to such a scenario, and can be applied to any wireless communication device such as a wireless communication device equipped with multiple wireless communication units 12 installed on a vehicle, or a smartphone.

[0083] (Variation 6 common to the first and second embodiments) Even if each wireless communication unit 12 disconnects a wireless communication link with another wireless communication device, it may be unable to connect to a new wireless communication device and may reconnect to the original wireless communication device. In this case, since it may be impossible to find another wireless communication device with good quality, the wireless communication unit 12 may be controlled not to connect to the wireless communication device that was connected to the previous wireless communication device for a certain period of time. In each embodiment, the acquisition of quality information and the control of disconnecting the communication link are performed by a loop asynchronous with the communication link connection process. However, the loop may be triggered by the communication link connection process. The quality information may be acquired periodically. That is, a timer may be provided in any of the loops shown in FIGS. 2 to 5, and the quality information may be acquired at regular intervals. It is expected that the quality information will fluctuate over time. Therefore, multiple pieces of quality information may be collected for each wireless communication unit 12, and the average value may be used as the quality information.

[0084] Some or all of the functional units of the wireless communication device 10 in the above-described embodiment are realized as software by one or more processors, such as a CPU (Central Processing Unit), executing a program stored in a storage device having a non-volatile storage medium (non-transitory storage medium) and memory. The program may be recorded on a computer-readable non-transitory storage medium. Examples of computer-readable non-transitory storage media include portable media such as flexible disks, magneto-optical disks, ROMs (Read Only Memory), and CD-ROMs (Compact Disc-ROMs), and storage devices such as hard disks built into computer systems.

[0085] Some or all of the functional units of the wireless communication device 10 may be realized using hardware including electronic circuits (electronic circuits or circuitry) using, for example, an LSI (Large Scale Integrated circuit), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array).

[0086] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention.

[0087] The present invention can be applied to a wireless communication device that performs wireless communication with one or more other wireless communication devices.

[0088] REFERENCE SIGNS LIST 10... wireless communication device, 11... data processing unit, 12, 12-1, 12-2... wireless communication unit, 13... quality information collection unit, 14... communication control unit, 15, 15-1, 15-2... antenna

Claims

1. A wireless communication device comprising: a plurality of wireless communication units that communicate with different wireless communication devices; and a communication control unit that controls at least one of the plurality of wireless communication units to search for a wireless communication device other than the wireless communication device to which the at least one wireless communication unit is connected, the quality information of the wireless communication line between the at least one wireless communication unit and the wireless communication device satisfying a predetermined condition indicating good communication quality.

2. The wireless communication device according to claim 1, wherein the communication control unit selects a wireless communication unit to be used for communication from among the plurality of wireless communication units based on the quality information of the wireless communication line of each of the plurality of wireless communication units, and controls the at least one wireless communication unit other than the selected wireless communication unit to search for a wireless communication device that satisfies the predetermined condition.

3. The wireless communication device according to claim 2, wherein the communication control unit searches for a wireless communication device that satisfies the predetermined condition when the quality information of the wireless communication line of the wireless communication unit to be used for communication does not satisfy a quality condition indicating good communication quality.

4. The wireless communication device according to claim 1, wherein the communication control unit selects the at least one wireless communication unit to be used for communication from among the plurality of wireless communication units based on the quality information of the wireless communication line of each of the plurality of wireless communication units, and controls the selected at least one wireless communication unit to search for a wireless communication device that satisfies the predetermined condition.

5. The wireless communication device according to any one of claims 1 to 4, wherein when there is a wireless communication device that satisfies the predetermined condition, the communication control unit instructs the at least one wireless communication unit to connect to the wireless communication device that satisfies the predetermined condition.

6. The wireless communication device according to claim 5, wherein the communication control unit instructs the at least one wireless communication unit to connect to the wireless communication device that satisfies the predetermined condition when the communication quality of the wireless communication device that satisfies the predetermined condition is better than that of the currently connected wireless communication device based on the quality information obtained from the wireless communication device that satisfies the predetermined condition and satisfies a condition indicating this.

7. A wireless communication system comprising a first wireless communication device and a plurality of second wireless communication devices that communicate with the first wireless communication device, wherein the first wireless communication device includes: a plurality of wireless communication units that communicate with the plurality of second wireless communication devices; and a communication control unit that controls at least one of the plurality of wireless communication units to search for a wireless communication device other than the second wireless communication device to which the at least one wireless communication unit is connected and for which quality information of a wireless communication line between the at least one wireless communication unit and the wireless communication device satisfies a predetermined condition indicating good communication quality. The plurality of second wireless communication devices include one or more wireless communication units that communicate with the first wireless communication device.

8. A wireless communication method of controlling at least one of a plurality of wireless communication units that communicate with different wireless communication devices to search for a wireless communication device other than the wireless communication device to which the at least one wireless communication unit is connected and for which quality information of a wireless communication line between the at least one wireless communication unit and the wireless communication device satisfies a predetermined condition indicating good communication quality.

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