Communication apparatus, communication method, and communication system

Abstract

To provide a communication device, a communication method, and a communication system capable of suppressing a roaming failure.SOLUTION: In a communication system, a communication device includes a determination unit for determining a communication device of a roaming destination by referring to a storage unit for holding a list about roaming destination candidates, and an execution unit for executing roaming to the communication device when detecting a control channel transmitted by the communication device. The determination unit determines a communication device of a roaming destination when a reception level of a control channel transmitted by a connected communication device becomes equal to or less than a threshold. In addition, a control channel transmitted by a communication device other than the connected communication device is scanned, and the list of the storage unit is generated and updated.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present disclosure relates to a communication device, a communication method, and a communication system. [Background technology]

[0002] One wireless communication system is the DECT (Digital Enhanced Cordless Telecommunications) system. In the DECT system, for example, roaming is performed to prevent degradation of communication quality. Patent Document 1 discloses a communication system that can reduce power consumption and prevent deterioration of response when roaming, which switches a master station corresponding to a slave station. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-159585 Summary of the Invention [Problem to be solved by the invention]

[0004] The receiver periodically scans the control channels of transmitters that are potential roaming destinations. However, in the DECT system, transmitters may switch (change) their control channels due to interference, and the receiver may fail to roam.

[0005] For example, a receiver periodically scans the control channels of transmitters that can be candidates for roaming destinations. The receiver determines roaming for a transmitter (control channel) based on the results of the most recent scan. However, if the transmitter switches its control channel to another control channel due to jamming or other reasons after the receiver's most recent scan, the control channel after the transmitter's switch will differ from the control channel in the receiver's most recent scan result. In this case, the receiver will fail to roam.

[0006] Non-limiting embodiments of the present disclosure contribute to providing a communication device, a communication method, and a communication system that can reduce roaming failures. [Means for solving the problem]

[0007] A communication device according to one embodiment of the present disclosure includes a determination unit that refers to a memory unit that holds a list of candidate roaming destinations and determines a communication device to roam to, and an execution unit that, when it detects a control channel transmitted by the communication device, executes roaming to the communication device.

[0008] A communication method according to one embodiment of the present disclosure refers to a memory unit that stores a list of candidate roaming destinations, determines a communication device to roam to, and, if a control channel transmitted by the communication device is detected, performs roaming to the communication device.

[0009] A communication system according to one embodiment of the present disclosure includes a plurality of first communication devices that switch control channels depending on the surrounding environment, a second communication device having a determination unit that refers to a memory unit that holds a list of candidate roaming destinations and determines a communication device to roam to from among the plurality of first communication devices, and an execution unit that, when it detects a control channel transmitted by the communication device, executes roaming to the communication device.

[0010] These comprehensive or specific aspects may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. [Effects of the Invention]

[0011] According to an embodiment of the present disclosure, roaming failures can be reduced.

[0012] Further advantages and benefits of an embodiment of the present disclosure will become apparent from the specification and drawings. Such advantages and / or benefits may be provided by some of the embodiments and features described in the specification and drawings, respectively, but not necessarily all of them may be provided to obtain one or more identical features. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 illustrates a communication system to which a communication device according to the present disclosure is applied. [Figure 2] Block diagram of the central unit and transmitter [Figure 3] Block diagram of the radio section of the transmitter [Figure 4] Block diagram of the receiver and base unit [Figure 5] Block diagram of the radio section of the receiver [Figure 6] FIG. 2 shows a time chart of the communication system shown in FIG. 1. [Figure 7A] Diagram explaining roaming [Figure 7B] Diagram explaining roaming [Figure 7C] Diagram explaining roaming [Figure 8] Flowchart showing the control channel switching operation of the transmitter [Figure 9] Flowchart showing the control channel switching operation of the transmitter [Figure 10] Flowchart showing the operation in S13 of FIG. 9 [Figure 11] Flowchart showing receiver scanning operation [Figure 12] Flowchart showing receiver roaming operation DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings as appropriate. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or redundant explanation of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art.

[0015] The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0016] <System configuration> Fig. 1 is a diagram showing a communication system to which a communication device according to the present disclosure is applied. As shown in Fig. 1, the communication system includes a central unit 1, transmitters 2a to 2c, receivers 3a to 3d, and a doorbell 4. Fig. 1 shows an apartment building A1 in which the communication system is installed.

[0017] The central unit 1 is connected to the transmitters 2a to 2c by wire or wirelessly. In the following, it is assumed that the central unit 1 is connected to the transmitters 2a to 2c by wire. The central unit 1 is installed in, for example, a control room of an apartment building A1.

[0018] The transmitters 2a to 2c communicate wirelessly with the receivers 3a to 3d based on the DECT system. The transmitters 2a to 2c are installed, for example, on an outer wall in a passageway of the apartment building A1.

[0019] The receivers 3a to 3d are, for example, intercom slave units. The receivers 3a to 3d are installed, for example, near the entrances of the respective houses. The receivers 3a to 3d are connected to an intercom master unit (not shown) installed in each house.

[0020] The call bell 4 is connected to the central unit 1. The call bell 4 is installed, for example, in the lobby of the apartment building A1.

[0021] The doorbell 4 communicates with an intercom master unit installed inside a door via the central unit 1, transmitters 2a to 2c, and receivers 3a to 3d. For example, when a room number is pressed, the doorbell 4 communicates with the intercom master unit installed inside the door of the pressed room number via the central unit 1, transmitters 2a to 2c, and receivers 3a to 3d.

[0022] The application of the communication system according to the present disclosure is not limited to the intercom system in the apartment building A1, but may also be applied to a telephone system using the DECT standard.

[0023] The numbers of the central unit 1, transmitters 2a to 2c, and receivers 3a to 3d are not limited to the example shown in Fig. 1. Furthermore, the transmitters 2a to 2c may have a receiving function, and the receivers 3a to 3d may have a transmitting function.

[0024] The central unit 1 may be called a master. The transmitters 2a to 2c may be called slaves. The transmitters 2a to 2c and the receivers 3a to 3d may be called communication devices.

[0025] In the following, when there is no need to distinguish between the transmitters 2a to 2c, they may be referred to as transmitters 2. When there is no need to distinguish between the receivers 3a to 3d, they may be referred to as receivers 3. The intercom master unit may be referred to as a master unit.

[0026] <Block configuration> 1. Block configuration of central unit 1 and transmitter 2 FIG. 2 is a block diagram of the central unit 1 and the transmitter 2. As shown in FIG. 2, the central unit 1 has a control unit 11a and a wired unit 12a. The control unit 11a controls the entire central unit 1. The control unit 11a also controls the transmitter 2. The wired unit 12a communicates with the transmitter 2 via a wire. The control unit 11a may be configured by a processor such as a CPU (Central Processing Unit), for example.

[0027] Transmitter 2a has wired unit 21a and wireless unit 22a. Transmitter 2b has wired unit 21b and wireless unit 22b. Transmitter 2c has wired unit 21c and wireless unit 22c. Hereinafter, when there is no need to distinguish between wired units 21a to 21c, they may be referred to as wired unit 21. When there is no need to distinguish between wireless units 22a to 22c, they may be referred to as wireless unit 22.

[0028] The wired unit 21 communicates with the central unit 1 via a wired connection. The wired unit 21 communicates with the wireless unit 22 via, for example, a USB (Universal Serial Bus).

[0029] The radio unit 22 of one transmitter 2 communicates wirelessly with multiple receivers 3. For example, the radio unit 22a of the transmitter 2a communicates wirelessly with up to 45 receivers 3.

[0030] 2. Block configuration of the radio section 22 of the transmitter 2 Fig. 3 is a block diagram of the wireless unit 22 of the transmitter 2. As shown in Fig. 3, the wireless unit 22 has a USB communication unit 61, an application control unit 62, a channel information management unit 63, a scan channel reception control unit 64, a control channel transmission control unit 65, a wireless reception unit 66, and a wireless transmission unit 67.

[0031] The USB communication unit 61 communicates with the wired unit 21 (see FIG. 2) via USB. The application control unit 62 controls the entire wireless unit 22. The application control unit 62 may be configured by a processor such as a CPU, for example.

[0032] The channel information management unit 63 manages, in a storage unit, information on the control channels transmitted from other transmitters 2 to the receiver 3. The control channel information managed by the channel information management unit 63 includes, for example, information on the slot and frequency of the control channel. The control channel may also be referred to as a control signal or control information.

[0033] The scan channel reception control unit 64 scans for jamming radio waves (interfering radio waves) for the control channel in use. For example, the scan channel reception control unit 64 stops transmission of the control channel and receives a radio signal at the frequency of the control channel whose transmission has been stopped. The scan channel reception control unit 64 scans the reception strength, such as the RSSI (Received Signal Strength Indicator), of the received radio signal. "Scan" may be interpreted as "monitor" or "detect."

[0034] The control channel transmission control unit 65 switches the control channel to be transmitted to the receiver 3 based on the scan result of the scan channel reception control unit 64. The control channel transmission control unit 65 also switches the control channel based on the channel information (information on the control channels used by other transmitters 2) managed by the channel information management unit 63. "Switch" may be read as "control."

[0035] The wireless receiving unit 66 receives a wireless signal. The wireless transmitting unit 67 transmits a wireless signal.

[0036] 3. Block configuration of receiver 3 and master unit 5 4 is a block diagram of the receiver 3 and the base unit 5. The base unit 5 is an intercom base unit installed in each unit of the apartment building A1.

[0037] The receiver 3 has a wireless unit 31a and a wired unit 31b. The wireless unit 31a wirelessly communicates with one of the multiple transmitters 2a to 2c. The wireless unit 31a performs roaming based on the reception strength, such as RSSI, of the control channel transmitted from the transmitter 2. Roaming may also be interpreted as handover or handoff. The wired unit 31b communicates with the base unit 5 installed indoors via a wired connection.

[0038] The master unit 5 has a control unit 51a and a wired unit 51b. The control unit 51a controls the entire master unit 5. The control unit 51a also controls the receiver 3 via the wired unit 51b. The wired unit 51b communicates with the receiver 3 via a wire.

[0039] 4. Block configuration of the radio unit 31a of the receiver 3 Fig. 5 is a block diagram of the wireless unit 31a of the receiver 3. As shown in Fig. 5, the wireless unit 31a has a USB communication unit 71, an application control unit 72, a channel information management unit 73, a control channel reception control unit 74, a scan channel reception control unit 75, a control channel transmission control unit 76, a wireless receiving unit 77, and a wireless transmitting unit 78.

[0040] The USB communication unit 71 communicates with the wired unit 31b via USB. The application control unit 72 controls the entire wireless unit 31a. The application control unit 72 may be configured by a processor such as a CPU, for example.

[0041] The channel information management unit 73 manages, in the storage unit, information on control channels other than the control channel being received. For example, when the radio unit 31a is receiving the control channel of the transmitter 2a (when the receiver 3 is connected to the transmitter 2a), the channel information management unit 73 manages, in the storage unit, information (device list) on the control channels transmitted by the transmitters 2b and 2c.

[0042] The control channel reception control unit 74 controls the reception of the control channel. For example, the control channel reception control unit 74 has a determination unit and an execution unit (not shown). The determination unit, for example, refers to a storage unit that stores a device list and determines the transmitter 2 to roam to. When the execution unit detects the control channel transmitted by the determined transmitter 2, it executes roaming to the determined transmitter 2. Roaming is executed, for example, when the communication quality of the control channel in the connected transmitter 2 deteriorates due to an object being placed in the hallway of the apartment building A1. The control channel reception control unit 74 may be configured by a processor such as a CPU.

[0043] The scan channel reception control unit 75 scans the control channels. For example, the scan channel reception control unit 75 changes the slot and frequency of the control channel to be received, and scans the control channels transmitted from each transmitter 2.

[0044] The control channel transmission control unit 76 controls the control channel to be transmitted to the transmitter 2. The radio receiving unit 77 receives radio signals. The radio transmitting unit 78 transmits radio signals.

[0045] <Timing chart> Fig. 6 is a diagram showing a time chart of the communication system shown in Fig. 1. As shown by the "frame" and "slot" in Fig. 6, one frame is made up of multiple slots 0, 1, 2, 3, 4, ... The number of slots in one frame is, for example, 12 or 24.

[0046] The numbers in square boxes shown to the right of "transmitters 2a to 2c" in Fig. 6 indicate the frequencies (identifiers) of the control channels transmitted by the transmitters 2a to 2c. The transmitters 2a to 2c can use, for example, eight frequencies 0 to 7.

[0047] Transmitters 2a to 2c can transmit control channels in predetermined slots and frequencies. In the example of FIG. 6, transmitter 2a transmits a control channel in slot 0 and frequency 2. Transmitter 2b transmits a control channel in slot 3 and frequency 0. Transmitter 2c transmits a control channel in slot 2 and frequency 1 in frames f to f+3, and in slot 4 and frequency 6 in frames f+8 to f+10.

[0048] Transmitters 2a to 2c periodically scan for jamming signals on the control channels they are using (transmitting). In the example of Fig. 6, transmitter 2c stops transmission of the control channel in slot 2 and frequency 1 in frame f+7 and scans for jamming signals. Transmitter 2c detects jamming signals on the control channel for which transmission has been stopped, and switches control channel transmission to slot 4 and frequency 6 from frame f+8 onwards.

[0049] The numbers in square boxes shown to the right of "Receiver 3" in Fig. 6 indicate the control channels received by the receiver 3. In the example of Fig. 6, the receiver 3 receives the control channel at slot 0 and frequency 2 (receives the control channel transmitted by the transmitter 2a). In other words, the receiver 3 is connected to the transmitter 2a.

[0050] The S in a square box shown to the right of "Receiver 3" in Fig. 6 indicates that receiver 3 is performing a scan operation. In the example of Fig. 6, receiver 3 performs a scan operation in slots other than slot 0.

[0051] The numbers shown to the right of "reception and scanning frequencies" in FIG. 6 indicate the reception frequencies and scanning frequencies of the receiver 3.

[0052] In resources other than the slots and frequencies for receiving the control channel, the receiver 3 scans the reception levels of the control channels of transmitters other than the currently connected transmitter 2a. For example, as shown to the right of "Reception and Scan Frequency" in Fig. 6, in slots other than slot 0 for receiving the control channel, the receiver 3 scans the reception levels of the control channels of transmitters 2b and 2c other than the currently connected transmitter 2a by repeating the frequency 0, 1, 2, 3, ... 7, 0, 1, 2, 3, ... 7, 0, 1, 2, ... in frame units.

[0053] The control channel scan result may indicate roaming destination candidates for the receiver 3. The control channel scan result may be considered as information on roaming destination candidates.

[0054] <Roaming> Figures 7A, 7B, and 7C are diagrams explaining roaming. The central unit 1 is not shown in Figures 7A, 7B, and 7C. The device list L1 shown in Figures 7A, 7B, and 7C shows the results of scanning the control channel of the receiver 3. In other words, the device list L1 shown in Figures 7A, 7B, and 7C shows roaming destination candidates for the receiver 3. The device IDs "x," "y," and "z" in the device list L1 indicate the device IDs of the transmitters 2a to 2c.

[0055] As shown in FIG. 7A, the receiver 3 is wirelessly connected to the transmitter 2a. As shown in FIG. 7B, the quality (reception level) of the wireless communication from the transmitter 2a at the receiver 3 decreases. In this case, the receiver 3 roams to the transmitter with the best reception level among the transmitters 2a to 2c included in the device list L1. For example, as shown in FIG. 7C, the receiver 3 roams to the transmitter 2b. Note that the receiver 3 acquires (updates) the device list L1 even after roaming.

[0056] <Considerations> The receiver periodically scans for transmitters (control channels) that can be roaming destination candidates. For example, as shown by "S" in Figure 6, the receiver 3 scans for transmitters 2b and 2c as roaming destination candidates and obtains a device list.

[0057] However, in the DECT system, the transmitter may switch (change) the control channel due to jamming radio waves or the like, and the receiver may fail to roam.

[0058] For example, as shown in frame f+8 in Figure 6, transmitter 2c switches the frequency of its control channel from frequency 1 to frequency 6 due to jamming or other reasons. The frequency of transmitter 2c included in the device list of receiver 3 is updated in the receiver 3's next scan operation for frequency 6 (frame f+14).

[0059] Here, the receiver 3 decides to roam from transmitter 2a to transmitter 2c because the reception level of the control channel of transmitter 2a drops between frames f+8 and f+13. In this case, the receiver 3 fails to roam to transmitter 2c because the latest control channel frequency 6 of transmitter 2c is not reflected in the device list.

[0060] Therefore, the receiver 3 of the present disclosure determines the transmitter 2 to which it is to roam, and when it detects the control channel of the determined transmitter 2, it performs roaming to the determined transmitter 2.

[0061] <Transmitter 2 operation> 1. Control channel switching (1) The transmitter 2 switches the control channel depending on the surrounding environment, such as jamming radio waves. For example, the transmitter 2 switches the control channel depending on jamming radio waves (radio interference) from another DECT communication system, such as a DECT telephone installed inside the apartment building A1.

[0062] 8 is a flowchart showing the control channel switching operation of the transmitter 2. The transmitter 2, for example, periodically executes the process of the flowchart shown in FIG.

[0063] The transmitter 2 stops transmitting the control channel and receives a radio signal at the frequency of the stopped control channel (S1).

[0064] The transmitter 2 determines whether the reception level of the radio signal received in S1 is equal to or greater than a threshold value (S2).

[0065] When the transmitter 2 determines that the reception level of the wireless signal received in S1 is equal to or higher than the threshold (YES in S2), it switches the control channel (S3). That is, the transmitter 2 determines that jamming radio waves are occurring in the control channel being transmitted, and switches the control channel. Then, the transmitter 2 ends the processing of the flowchart in FIG. 8.

[0066] When the transmitter 2 determines in S1 that the reception level of the received wireless signal is not equal to or greater than the threshold (NO in S2), the transmitter 2 ends the processing of the flowchart in FIG.

[0067] 2. Control channel switching (2) When the transmitter 2 switches the control channel, it notifies switching information related to the switched control channel to the other transmitters 2. For example, when the transmitter 2a shown in Fig. 2 switches the control channel based on the processing of the flowchart in Fig. 8, it notifies information on the slot and frequency of the control channel after the switching to the other transmitters 2b and 2c.

[0068] Another transmitter 2b, which has received the notification of the switching information, switches (changes) the control channel of transmitter 2b if the control channel to which transmitter 2a has switched overlaps (is the same as) the control channel of transmitter 2b. Similarly, another transmitter 2c, which has received the notification of the switching information, switches the control channel of transmitter 2c if the control channel to which transmitter 2a has switched overlaps with the control channel of transmitter 2c. This suppresses overlapping (interference) of the control channels of transmitters 2.

[0069] Fig. 9 is a flowchart showing the control channel switching operation of transmitter 2b. Below, transmitter 2a executes the process of the flowchart in Fig. 8 to switch the control channel. Transmitter 2c also executes the same operation as transmitter 2b (the flowchart in Fig. 9), but the description thereof will be omitted.

[0070] The transmitter 2b receives the control channel switching information from the transmitter 2a (S11).

[0071] The transmitter 2b determines whether the control channel of the transmitter 2b is the same as the control channel in the switching information received in S11 (S12). That is, the transmitter 2b determines whether the control channel of the transmitter 2b is the same as the control channel of the transmitter 2a that switched the control channel.

[0072] If the transmitter 2b determines that the control channel of the transmitter 2b is not the same as the control channel of the transmitter 2a that has switched the control channel (NO in S12), the process of this flowchart ends.

[0073] On the other hand, if the transmitter 2b determines that the control channel of the transmitter 2b is the same as the control channel of the transmitter 2a that has switched the control channel (YES in S12), the transmitter 2b switches the control channel of the transmitter 2b (S13). The process of S13 will be described in detail in the flowchart of FIG.

[0074] The transmitter 2b notifies the transmitters 2a and 2c of the control channel switching information switched in S13 (S14), and then the transmitter 2b ends the processing of the flowchart in FIG.

[0075] The transmitters 2a and 2c that have received the notification of the switching information in S14 execute the process of the flowchart in Fig. 9. That is, the transmitter 2 executes the process of the flowchart in Fig. 9 not only in response to the surrounding environment such as jamming radio waves, but also when another transmitter 2 switches the control channel to avoid interference on the control channel.

[0076] Furthermore, when the transmitter 2 is powered on, it may determine the control channel based on an initial setting or randomly. The transmitter 2 may notify other transmitters 2 of the determined control channel. A transmitter that receives notification of control channel determination information may execute the flowchart of Fig. 9. In this case, the "switching information" in S11 and S12 in Fig. 9 is replaced with "determination information."

[0077] The transmitter 2 shares control channel information by notifying control channel switching information and decision information. For example, the transmitter 2a shown in FIG. 2 has information on the control channels (slots and frequencies) used by the transmitters 2b and 2c. The transmitter 2b has information on the control channels used by the transmitters 2a and 2c. The transmitter 2c has information on the control channels used by the transmitters 2a and 2b.

[0078] Fig. 10 is a flowchart showing the operation in S13 of Fig. 9. The transmitter 2b selects a slot (S21). For example, the transmitter 2b selects one slot in order starting from slot 0.

[0079] The transmitter 2b determines whether the slot selected in S21 is the same as the slot of the control channel of the transmitters 2a and 2b (S22).

[0080] If the slot selected in S21 is the same as the slot of the control channel of the transmitters 2a and 2b (YES in S22), the transmitter 2b determines whether there is a next slot to select (S23).

[0081] If the transmitter 2b determines that there is a next slot to select (YES in S23), the process proceeds to S21 and the transmitter 2b selects the next slot.

[0082] If the transmitter 2b determines in S22 that the slot selected in S21 is not the same as the slot of the control channel of the transmitters 2a and 2b (NO in S22), the transmitter 2b selects a frequency (S24). For example, the transmitter 2b selects a frequency one by one starting from frequency 0.

[0083] The transmitter 2b determines whether the reception level of the radio signal in the slot selected in S21 and at the frequency selected in S24 is equal to or lower than a threshold (S25). That is, the transmitter 2b determines whether the interference level in the slot selected in S21 and at the frequency selected in S24 is equal to or lower than a threshold.

[0084] If the level of the radio signal in the slot selected in S21 and at the frequency selected in S24 is not equal to or less than the threshold (NO in S25), the transmitter 2b determines whether there is a next frequency to select (S26). If there is a next frequency to select, the transmitter 2b proceeds to S24 and selects the next frequency.

[0085] If the level of the radio signal in the slot selected in S21 and the frequency selected in S24 is below the threshold (YES in S25), the transmitter 2b retains the control channel in the slot selected in S21 and the frequency selected in S24 as a candidate control channel for switching (S27).

[0086] If the transmitter 2b determines in S26 that there is no next frequency to select (NO in S26), the process proceeds to S23, where it determines whether there is a next slot to select.

[0087] If it is determined in S23 that there is no next slot to select (NO in S23), the transmitter 2b determines the switching candidate channel held in S27 as the switching control channel (S28). Then, the transmitter 2b ends the processing of this flowchart.

[0088] That is, the transmitter 2b searches for a slot and frequency where the interference level is below the threshold and is the lowest while changing the slot and frequency, and then determines the searched slot and frequency as the slot and frequency of the control channel.

[0089] <Receiver 3 operation> 1. Scan 11 is a flowchart showing the scanning operation of the receiver 3. The receiver 3 scans the reception level in slots other than the reception slot of the control channel (S31). For example, the receiver 3 scans the reception level in the "S" slot shown in FIG. 6 and at the reception and scan frequencies shown in FIG. 6.

[0090] The receiver 3 determines whether the reception level of the slot scanned in S31 is the reception level (reception level of the control channel) of the transmitter 2 in the communication system (the communication system shown in FIG. 1 to which the receiver 3 belongs) (S32). For example, the receiver 3 determines whether the reception level is the reception level of the transmitter 2 in the communication system based on the device ID of the transmitter 2 included in the control channel.

[0091] If the receiver 3 determines that the reception level of the slot scanned in S31 is the reception level of the transmitter 2 within the communication system (YES in S32), it stores the channel information of the scanned reception level in the device list (see Figure 7) (S33).

[0092] Then, the receiver 3 changes the frequency to be scanned (S34) and returns to the process at S31. When the receiver 3 determines that the reception level of the slot scanned in S31 is not the reception level of the transmitter 2 in the communication system (NO in S32), the receiver 3 returns to the process in S31.

[0093] That is, the receiver 3 scans the control channels transmitted by transmitters 2 other than the currently connected transmitter 2 while changing the slot and frequency. Then, the receiver 3 generates and updates a device list. The receiver 3 stores the generated and updated device list in a storage unit.

[0094] 2. Roaming 12 is a flowchart showing the roaming operation of the receiver 3. The receiver 3 periodically executes the process of the flowchart in FIG.

[0095] The receiver 3 determines whether or not the reception level of the control channel transmitted from the currently connected transmitter 2 is equal to or lower than a threshold (S41). That is, the receiver 3 determines whether or not to perform roaming.

[0096] If the reception level of the control channel transmitted from the currently connected transmitter 2 is not equal to or lower than the threshold (NO in S41), the receiver 3 ends the processing of this flowchart.

[0097] If the reception level of the control channel transmitted from the currently connected transmitter 2 is equal to or lower than the threshold (YES in S41), the receiver 3 determines whether or not the control channel information of the transmitter 2 is present in the device list (see FIG. 7) (S42). That is, the receiver 3 determines whether or not the device list contains any roaming destination candidates.

[0098] If the control channel information of the transmitter 2 is not present in the device list (NO in S42), the receiver 3 ends the processing of this flowchart.

[0099] On the other hand, if the control channel information of the transmitter 2 is present in the device list (YES in S42), the receiver 3 determines (selects) the control channel information (slot and frequency) with the highest reception level in the device list (S43). That is, the receiver 3 determines the transmitter 2 with (transmitting) the control channel with the highest reception level among the transmitters 2 in the device list as the transmitter 2 to roam to.

[0100] The receiver 3 determines whether or not the control channel of the control channel information determined in S43 is detected (S44). That is, the receiver 3 determines whether or not the control channel of the transmitter 2 determined as the roaming destination is detected.

[0101] If the receiver 3 detects a control channel in S44 (YES in S44), it roams to the transmitter 2 transmitting the detected control channel (S45). Then, the receiver 3 ends the processing of this flowchart.

[0102] On the other hand, if the receiver 3 does not detect a control channel in S44 (NO in S44), it deletes the control channel information of the transmitter 2 that transmits the undetected control channel from the device list (S46).Then, the receiver 3 proceeds to S41 and determines a transmitter 2 that can be the next roaming destination based on the device list.

[0103] Note that the case where the control channel is not detected in S44 (NO in S44) is, for example, when the transmitter 2 changes the control channel due to jamming radio waves or the like after the receiver 3 updates the device list to the latest version.

[0104] <Summary of the embodiment> As described above, the receiver 3 refers to the storage unit that stores the device list related to roaming destination candidates, and determines the transmitter 2 to roam to. When the receiver 3 detects the control channel transmitted by the determined transmitter 2, it roams to the determined transmitter 2.

[0105] As a result, even if the transmitter 2 switches the control channel depending on the surrounding environment and the information on the control channel after switching is not reflected in the device list, the receiver 3 will roam to the determined transmitter 2 when it detects the control channel of the transmitter 2 determined as the roaming destination, thereby reducing roaming failures.

[0106] Furthermore, if the receiver 3 does not detect the control channel of the transmitter 2 determined as the roaming destination, it deletes information about the transmitter 2 determined as the roaming destination from the device list, and determines the roaming destination transmitter 2 by referring to the device list from which the information has been deleted. This allows the receiver 3 to prevent roaming failures.

[0107] Although the embodiments have been described above with reference to the drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims. It is understood that such modifications or alterations also fall within the technical scope of the present disclosure. Furthermore, the components in the embodiments may be combined in any manner without departing from the spirit of the present disclosure.

[0108] In the above-described embodiments, the notation "... part" used for each component may be replaced with other notations such as "... circuitry," "... assembly," "... device," "... unit," or "... module."

[0109] The present disclosure can be realized by software, hardware, or software linked to hardware. Each functional block used in the description of the above embodiments may be partially or entirely realized as an LSI, which is an integrated circuit, and each process described in the above embodiments may be partially or entirely controlled by a single LSI or a combination of LSIs. The LSI may be composed of individual chips, or may be composed of a single chip that includes some or all of the functional blocks. The LSI may have data input and output. Depending on the degree of integration, the LSI may be called an IC, system LSI, super LSI, or ultra LSI.

[0110] The integrated circuit method is not limited to LSI, but may be realized by a dedicated circuit, a general-purpose processor, or a dedicated processor. Also, a field programmable gate array (FPGA) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connections and settings of circuit cells within the LSI, may be used. The present disclosure may be realized as digital processing or analog processing.

[0111] Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology or other derivative technologies, it is natural that such technology may be used to integrate functional blocks. The application of biotechnology, etc. is also a possibility.

[0112] The present disclosure may be implemented in any type of apparatus, device, or system (collectively referred to as a communications apparatus) that has a communications function. The communications apparatus may include a wireless transceiver and processing / control circuitry. The wireless transceiver may include a receiver and a transmitter, or both functions. The wireless transceiver (transmitter and receiver) may include a radio frequency (RF) module and one or more antennas. The RF module may include an amplifier, an RF modulator / demodulator, or the like. Non-limiting examples of communication devices include telephones (e.g., cell phones, smartphones), tablets, personal computers (PCs) (e.g., laptops, desktops, notebooks), cameras (e.g., digital still / video cameras), digital players (e.g., digital audio / video players), wearable devices (e.g., wearable cameras, smartwatches, tracking devices), game consoles, digital book readers, telehealth / telemedicine devices, communication-enabled vehicles or mobile transportation (e.g., cars, airplanes, ships), and combinations of the above devices.

[0113] Communications equipment is not limited to portable or mobile equipment, but also includes non-portable or fixed equipment, devices, and systems of any kind, such as smart home devices (such as appliances, lighting equipment, smart meters or metering devices, control panels, etc.), vending machines, and any other "things" that may exist on an IoT (Internet of Things) network.

[0114] A communications apparatus also includes devices such as controllers and sensors connected or coupled to a communications device that performs the communications functions described in this disclosure, such as controllers and sensors that generate control and data signals used by the communications device to perform the communications functions of the communications apparatus.

[0115] The communication apparatus also includes infrastructure facilities, such as base stations, access points, and any other apparatus, device, or system that communicates with or controls the various apparatuses listed above, but are not limited to these. [Industrial Applicability]

[0116] The present disclosure is useful for intercom systems installed in apartment buildings. [Explanation of symbols]

[0117] 1 central machine 2,2a~2c transmitter 3,3a~3d receiver 4 Doorbell 5 Base unit A1 Apartment complex

Claims

1. a determining unit that determines a communication device as a roaming destination by referring to a storage unit that stores a list of roaming destination candidates; an execution unit that executes roaming to the communication device when a control channel transmitted by the communication device is detected; A communication device having:

2. the execution unit deletes information about the communication device from the list when the execution unit does not detect a control channel transmitted by the communication device. The communication device according to claim 1 .

3. the determination unit determines a roaming destination communication device by referring to the list from which the information about the communication device has been deleted. The communication device according to claim 2 .

4. the determination unit determines the communication device as the roaming destination when a reception level of a control channel transmitted by the currently connected communication device becomes equal to or lower than a threshold. The communication device according to claim 1 .

5. a generating unit that scans control channels transmitted by communication devices other than the currently connected communication device, and generates and updates the list; The communication device according to claim 1 .

6. Refer to a storage unit that stores a list of roaming destination candidates, and determine a communication device as a roaming destination; When the control channel transmitted by the communication device is detected, the communication device performs roaming to the communication device. Communication method.

7. a plurality of first communication devices that switch control channels in accordance with a surrounding environment; a second communication device having a determination unit that refers to a storage unit that stores a list of roaming destination candidates and determines a roaming destination communication device from among the plurality of first communication devices, and an execution unit that executes roaming to the communication device when a control channel transmitted by the communication device is detected; A communication system having:

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