JP2017220746A - Call server, call system, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a call from being made to have a wireless terminal whose communication link is disconnected during a conference call participate again in the conference call uselessly.SOLUTION: A call server of the present invention has a wireless terminal participate in a conference call via a communication link established between a base station and the wireless terminal wirelessly connected, and upon detection that the communication link gets disconnected between the wireless terminal and the base station, determines the cause of disconnection, and makes a call to the wireless terminal if the cause is eliminated. When a communication link with the wireless terminal is reestablished by the wireless terminal answering the call, the call server has the wireless terminal participate in the conference call.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a call server, a call system, and a program that provide a conference call service for performing simultaneous calls between a plurality of terminals by operators of the terminals.

  Patent Document 1 discloses a recall function in a private telephone system using a PHS (personal handyphone system). This is because when the connection is disconnected without terminating the on-hook operation, which is a normal operation of the PHS terminal due to a change in the wireless state, the battery of the PHS terminal being exhausted, or an erroneous operation of the PHS terminal during a conference call, This is a function for transmitting a call signal from the main control device to the PHS terminal. It is also shown that the number of recall calls is limited in order to prevent the recall from being repeated permanently when the PHS terminal does not respond to the recall.

JP 2006-324719 A

  However, if the cause of the disconnection continues, the terminal may not be able to answer the call. In such a case, even if the recall is performed, the wireless terminal cannot respond to the recall. Therefore, it can be said that the recall is a useless recall.

  The present invention has been made paying attention to the above circumstances, and its purpose is to make a useless call for re-participating a wireless terminal whose communication link was disconnected during a conference call (hereinafter referred to as a conference call). It is to provide a call server, a call system, and a program that can prevent "calling back").

  In order to achieve the above object, according to a first aspect of the present invention, a communication link established between a base station and a wireless terminal wirelessly connected is allowed to participate in a conference call, and the communication is performed. When it is detected that the link is disconnected between the wireless terminal and the base station, the cause of the disconnection is determined, and when the cause is resolved, a call is made to the wireless terminal. When the wireless terminal reestablishes a communication link with the wireless terminal in response to the call, the wireless terminal is allowed to participate in the conference call.

  According to the second aspect, the cause of the disconnection is determined with the occurrence of congestion in the base station as one of the candidates for the cause of the disconnection.

  In the third aspect, the cause of the disconnection is determined by setting one of the candidates for the cause of disconnection that the wireless terminal is not in an area where wireless communication with the base station is possible.

  According to a fourth aspect, when the wireless terminal participates in a conference call via a communication link established on the first network, and the cause is not resolved within a predetermined period, the second network Through this, information indicating that the communication link has been disconnected is transmitted to the wireless terminal.

  In the fifth aspect, validity / invalidity of the call operation is set, and when it is set to invalid, the call is not made.

  In the sixth aspect, the call is repeated a predetermined number of times until the wireless terminal responds to the call.

  The seventh aspect comprises a wireless terminal wirelessly connected to the base station and a call server, and the wireless terminal is capable of communication using a communication link established with the call server, When the communication link with the wireless terminal is disconnected, the base station includes notification means for notifying the call server that the communication has been disconnected when the communication link with the wireless terminal is disconnected. Conference processing means for causing the wireless terminal to participate in a conference call via a communication link, and detection means for detecting that the communication link is disconnected between the wireless terminal and the base station by notification from the notification means When the detection means detects that the communication link has been disconnected, the determination means for determining the cause of the disconnection, and the cause determined by the determination means are resolved The wireless terminal joins the conference call when a communication link is re-established between the calling means for calling the wireless terminal and the wireless terminal responding to the call and the wireless terminal. And a control means for controlling the conference processing means so as to make it happen.

  According to an eighth aspect, the wireless terminal includes response means for automatically responding to a call made by the call means.

  According to the first aspect and the seventh aspect, it is possible to prevent a useless recall from being performed on a wireless terminal whose communication link is disconnected during a conference call.

  According to the second aspect, by not making a call to a wireless terminal existing in the cell of the base station where congestion occurs, it is possible to prevent a wireless terminal that cannot respond from being recalled. it can. In addition, it is possible to prevent a further load from being applied to the base station in which congestion occurs.

  According to the third aspect, by not calling a wireless terminal that exists outside the service area, it is possible to prevent a wireless terminal that cannot respond from being recalled.

  According to the fourth aspect, even if the communication link remains disconnected, it is possible to notify the operator of the wireless terminal that the communication link is disconnected.

  According to the fifth aspect, the user of the call server can invalidate the recall when the recall is unnecessary.

  According to the sixth aspect, by setting a limit on the number of calls, it is possible to prevent repeated recalls indefinitely.

  According to the eighth aspect, even if the operator of the wireless terminal does not notice the call, the wireless terminal automatically responds to the call from the call server. This eliminates the need for the call server to recall many times.

The figure which shows the whole structure of the telephone system which concerns on 1st Embodiment of this invention. The block diagram which shows the principal part circuit structure of the telephone call system shown in FIG. The sequence diagram which shows the flow of the information in the telephone call system shown in FIG. The flowchart which shows the control processing by CPU of the telephone call server shown in FIG. The flowchart which shows the control processing by CPU of the radio | wireless terminal shown in FIG. The figure which shows the whole structure of the telephone call system which concerns on 3rd Embodiment of this invention. FIG. 7 is a sequence diagram showing a flow of information in the call system shown in FIG. 6. The flowchart which shows the control processing by CPU of the telephone call server shown in FIG.

Several embodiments according to the present invention will be described below with reference to the drawings. In the drawings and the description below, the same elements are denoted by the same reference numerals.
[First Embodiment]
(Constitution)
FIG. 1 is a diagram showing an overall configuration of a call system 1 according to the first embodiment of the present invention. The call system 1 includes a call server 10, a plurality of base stations 20, and a plurality of wireless terminals 30. The call server 10 is connected to the local network NW1. Each base station 20 is connected to the local network NW1 via the gateway G1. Further, each base station 20 can form cells C1, C2,... And perform wireless communication with the wireless terminal 30 in each cell. The on-site network NW1 is typically an intranet constructed on the premises with a company, organization, group, building, facility, or the like as a unit. Further, the gateway G1 enables mutual communication between each base station 20 and the local network NW1 by converting the protocols to each other.

  As the call server 10, an IP telephony server is typically used. The call server 10 controls simultaneous calls by a plurality of wireless terminals 30, that is, so-called conference calls. For example, the call server 10 is configured to control a conference call by using SIP (Session Initiation Protocol) as a protocol for performing call control and RTP (Real-time Transport Protocol) and RTCP (Real-time) as protocols for transmitting and receiving audio. time Transport Control Protocol).

  There are various types of conference calls, such as participatory conference calls and held conference calls. A participatory conference call is one in which a terminal can participate in a conference by calling a special number from the terminal. In the held conference call, a special call instructing the holding of the conference is issued from the terminal, and the conference call is performed by calling the terminals registered as participants all at once. These conference call special numbers are unique numbers determined for each conference call.

FIG. 2 is a block diagram showing the main circuit configuration of each of the call server 10, the base station 20, and the wireless terminal 30.
The call server 10 includes a central processing unit (CPU) 11, a main memory 12, an auxiliary storage device 13, a communication interface 14, and a bus 15.

  The CPU 11 corresponds to a central part of a computer that performs processing and control necessary for the operation of the call server 10. The CPU 11 controls each unit to implement various functions of the call server 10 based on programs such as an operating system and application software stored in the main memory 12.

  The main memory 12 corresponds to the main memory portion of the computer. The main memory 12 stores programs such as the operating system and application software. The main memory 12 stores data that the CPU 11 refers to when performing various processes. Further, the main memory 12 is used as a so-called work area that stores data temporarily used when the CPU 11 performs various processes.

  The auxiliary storage device 13 corresponds to the auxiliary storage portion of the computer. The auxiliary storage device 13 is, for example, an EEPROM (electrically erasable programmable read-only memory), an HDD (hard disc drive), or an SSD (solid state drive). The auxiliary storage device 13 stores data used when the CPU 11 performs various processes or data generated by the processes in the CPU 11. The auxiliary storage device 13 may store a program such as the above operating system or application. The auxiliary storage device 13 stores 0 or 1 as a setting value. When the set value is 0, the CPU 11 performs a control process shown in FIG. 4 described later, and when the set value is 1, the CPU 11 does not perform the control process shown in FIG. The value of 0 or 1 is set in advance by the administrator or operator of the call server 10. In the state where the setting value is not set by the administrator or the operator, a value determined as a default of 1 and 0 is set as the setting value. When the set value is changed, the CPU 11 writes the set value in the auxiliary storage device 13. As described above, when the process of writing the setting value to the auxiliary storage device 13 is performed, the computer having the CPU 11 as the center operates as a setting unit that sets whether the control process illustrated in FIG. 4 is valid or invalid.

  The programs stored in the main memory 12 or the auxiliary storage device 13 include a control program described regarding the control processing shown in FIG. As an example, the call server 10 is transferred to an administrator or owner of the call server 10 with the control program stored in the main memory 12 or the auxiliary storage device 13. However, the call server 10 may be transferred to an administrator or owner in a state where the control program is not stored in the main memory 12 or the auxiliary storage device 13. Then, a control program separately transferred to an administrator or an owner may be written into the main memory 12 or the auxiliary storage device 13 under an operation by the administrator, owner, or service person. The transfer of the control program at this time can be realized by recording on a removable recording medium such as a magnetic disk, a magneto-optical disk, an optical disk, or a semiconductor memory, or by downloading via a network.

  The communication interface 14 is an interface for the call server 10 to communicate via the local network NW1.

  The bus 15 includes an address bus, a data bus, and the like, and transmits signals exchanged in each part of the call server 10.

  The base station 20 includes a control unit 21, a communication unit 22, a wireless communication unit 23, and a disconnection detection unit 24. The control unit 21 controls the communication unit 22, the wireless communication unit 23, and the disconnection detection unit 24. The communication unit 22 performs a process for the base station 20 to communicate with a device connected to the local network NW1 via the gateway G1. The wireless communication unit 23 performs processing in which the base station 20 performs wireless communication with the wireless terminal 30. The disconnection detection unit 24 detects that the communication link established with the wireless terminal 30 wirelessly connected via the wireless communication unit 23 is abnormally disconnected. The abnormal disconnection is a disconnection in which the call server 10 or the wireless terminal 30 does not perform an operation for talking. When the call server 10 or the wireless terminal 30 performs an operation for talking, the call server 10 or the wireless terminal 30 transmits a signal indicating that it wants to finish the conversation. Therefore, the disconnection detection unit 24 can detect that the abnormal disconnection has occurred based on the presence or absence of the signal.

  The wireless terminal 30 can communicate with the call server 10 via the base station 20, the gateway G1, and the local network NW1 by being wirelessly connected to the base station 20. For wireless connection between the base station 20 and the wireless terminal 30, for example, a DECT (Digital Enhanced Cordless Telecommunications) method or a TETRA (Terrestrial Trunked Radio) method is used. Each wireless terminal 30 is assigned an extension number. Further, the radio terminal 30 has a function of performing handover in order to communicate with the base station 20 in a better communication state.

  The wireless terminal 30 includes a CPU 31, a main memory 32, an auxiliary storage device 33, a wireless interface 34 and a bus 35.

  The CPU 31 corresponds to a central part of a computer that performs processing and control necessary for the operation of the wireless terminal 30. The CPU 31 controls each unit to implement various functions of the wireless terminal 30 based on programs such as an operating system and application software stored in the main memory 32.

  The main memory 32 corresponds to the main memory portion of the computer. The main memory 32 stores programs such as the operating system and application software. The main memory 32 stores data that is referred to when the CPU 31 performs various processes. Further, the main memory 32 is used as a so-called work area that stores data temporarily used when the CPU 31 performs various processes.

  The auxiliary storage device 33 corresponds to the auxiliary storage portion of the computer. The auxiliary storage device 33 is, for example, an EEPROM, HDD, or SSD. The auxiliary storage device 33 stores data used when the CPU 31 performs various processes or data generated by the processes in the CPU 31. The auxiliary storage device 33 may store a program such as the above operating system or application.

  The wireless interface 34 is an interface for the wireless terminal 30 to perform wireless communication. The wireless terminal 30 performs wireless communication with the base station 20 through the wireless interface 34.

  The bus 35 includes an address bus, a data bus, and the like, and transmits signals transmitted and received by each unit of the wireless terminal 30.

(Operation)
The operation of the call system 1 according to the first embodiment will be described with reference to FIGS. 3 and 4 assuming that one wireless terminal 30 is abnormally disconnected during a conference call in which a plurality of wireless terminals 30 participate. To do. Note that the content of the processing described below is an example, and various processing that can obtain the same result can be used as appropriate.

The information flow of the call system 1 will be described with reference to FIG. FIG. 3 is a sequence diagram showing a flow of information in the call system 1. Note that FIG. 3 does not cover the information flow in the call system 1, and there may be an information flow (not shown). Further, although only one base station 20 is shown in FIG. 3, there are typically a plurality of base stations 20. 3 shows three wireless terminals 30, the number of wireless terminals 30 included in the call system 1 is not limited to three.
The operation of the call server 10 will be described with reference to FIG. FIG. 4 is a flowchart of control processing by the CPU 11 of the call server 10. The CPU 11 executes this control based on the control program stored in the main memory 12 and the auxiliary storage device 13.

In step S1 of FIG. 3, the call server 10 and the plurality of wireless terminals 30 are performing a conference call. In addition, about the method of starting a conference call, since a well-known method can be used, description is abbreviate | omitted. A communication link is established between the call server 10 and each wireless terminal 30 participating in the conference call via the local network NW1 and the base station 20. While a conference call is being performed, the call server 10 performs conference call processing for transmitting and receiving audio data related to the conference call to and from the wireless terminals 30 using the communication link for each wireless terminal 30. Yes. While the voice data is being transmitted and received between the call server 10 and the wireless terminal 30, the wireless terminal 30 is in a state of participating in a conference call. Therefore, the computer having the CPU 11 as the center operates as conference processing means by performing conference call processing.
If the set value is 1 when starting such a conference call, the CPU 11 also starts the control process shown in FIG. Note that the CPU 11 performs the process in parallel with the conference call process by executing the control process shown in FIG. 4 in a separate thread from the conference call process.

Here, it is assumed that the connection between the base station 20 and one wireless terminal 30 is abnormally disconnected during the conference call. The wireless terminal 30 is referred to as a disconnected terminal. When the abnormal disconnection occurs, the disconnection detection unit 24 of the base station 20 detects the abnormal disconnection.
In step S <b> 2 of FIG. 3, the base station 20 transmits a disconnection request (BYE) to the call server 10 to indicate that an abnormal disconnection has occurred in response to the disconnection detection unit 24 detecting the abnormal disconnection. This disconnection request includes information specifying which wireless terminal 30 is abnormally disconnected. For example, the extension number of the disconnected terminal is used as the information. When this process is performed, the base station 20 operates as a notification unit.

  At this time, in step ST1 of FIG. 4, the CPU 11 waits for the communication interface 14 to receive the disconnection request transmitted from the base station 20 as described above. This disconnection request is transmitted from the base station 20 when a disconnection occurs in the communication link established between the base station 20 and the disconnected terminal. Therefore, in this process, the computer having the CPU 11 as the center operates as a detection means. When the disconnection request is received, the CPU 11 determines Yes in step ST1, and proceeds to step ST2.

  In step ST <b> 2, the CPU 11 acquires information specifying which wireless terminal 30 is abnormally disconnected, which is included in the disconnection request.

  In step ST3, the CPU 11 ends the conference call process for the disconnected terminal being executed in another thread. In addition, as shown in step S3 of FIG. 3, the conference call process for terminals other than the disconnected terminal is continued.

  In step ST4, the CPU 11 checks in which cell of the base station 20 the disconnected terminal exists. For example, the CPU 11 updates management information for managing each position of the wireless terminal 30 as needed by a well-known position management process performed separately. For example, the CPU 11 refers to this management information to check in which cell of the base station 20 the disconnected terminal exists. When no disconnected terminal exists in any cell of the base station 20, it can be seen that the disconnected terminal is not within the area where wireless communication is possible, that is, is outside the service area.

  In step ST5, the CPU 11 confirms whether or not the disconnected terminal exists outside the service area, using the content checked in step ST4. When the disconnected terminal exists outside the service area, the CPU 11 determines Yes in step ST5 and returns to step ST4. Thus, when the disconnected terminal exists outside the service area, the CPU 11 repeats step ST4 and step ST5 until it is confirmed that the disconnected terminal exists in the cell of any one of the base stations 20. When the disconnected terminal does not exist outside the service area and exists in any of the cells of the base station 20, the CPU 11 determines No in step ST5 and proceeds to step ST6.

  In step ST6, the CPU 11 confirms whether or not congestion has occurred in the base station 20 that forms the cell in which the disconnected terminal exists. Whether or not congestion has occurred is confirmed by, for example, inquiring the base station 20 via the local network NW1. If the base station 20 is congested, the CPU 11 determines Yes in step ST6 and returns to step ST4. If there is no congestion in the base station 20, the CPU 11 determines No in step ST6 and proceeds to step ST7. As described above, when it is determined that the disconnected terminal is out of the service area by the processes in steps ST4 and ST5, it is determined that the cause of the abnormal disconnection is that the disconnected terminal has moved out of the service area. Further, when it is found by the processing in step ST6 that the base station is congested, it is determined that the cause of the abnormal disconnection is that the base station is congested. Therefore, when performing the processing of step ST4 to step ST6, the computer having the CPU 11 as the center operates as a determination unit that determines the cause of the disconnection.

  In step ST7, the CPU 11 makes a call to the disconnected terminal to re-establish a communication link with the disconnected terminal. That is, the CPU 11 generates a connection request (INVITE) and instructs the communication interface 14 to transmit this connection request to the disconnected terminal. This connection request is shown as step S4 in FIG. As shown in FIG. 3, the connection request in step S <b> 4 is transmitted to the disconnected terminal via the base station 20. The base station 20 is a base station 20 that forms a cell in which a disconnected terminal exists. When this processing is performed, the computer having the CPU 11 as the center operates as a calling unit that calls the disconnected terminal.

  On the other hand, in step S5 of FIG. 3, the disconnected terminal generates an incoming response (Ringing) in response to receiving the connection request, and transmits this incoming response to the call server 10. The disconnected terminal emits a ringing tone in response to receiving the connection request and notifies the operator of the disconnected terminal of the incoming call. When an operator of a disconnected terminal responds to an incoming call, the disconnected terminal goes off-hook.

  In step S <b> 6, the disconnected terminal generates a success response (OK) in response to being off-hook, and transmits this success response to the call server 10.

  On the other hand, in step ST8 in FIG. 4, the CPU 11 waits for an incoming response to be received by the communication interface 14. If the incoming call response is received, the CPU 11 determines Yes in step ST8 and proceeds to step ST9.

  In step ST <b> 9, the CPU 11 confirms whether a success response has been received by the communication interface 14. If the success response is not received, the CPU 11 determines No in step ST9 and proceeds to step ST10.

  In step ST10, the CPU 11 confirms whether or not the reception wait time for the success response has timed out. Note that the CPU 11 sets a time-out when a predetermined time has elapsed after completing the process of step ST8. In addition, when the process of step ST8 is performed a plurality of times, the CPU 11 sets a time-out that a predetermined time has elapsed since the last step ST8 was completed. If not timed out, the CPU 11 determines Yes in step ST10 and returns to step ST9. Thus, the CPU 11 repeats step ST9 and step ST10 until it receives a success response or times out. If a success response is received in the standby state of steps ST9 and ST10, the CPU 11 determines Yes in step ST9 and proceeds to step ST11.

  In step ST11, the CPU 11 generates a confirmation message (ACK) and instructs the communication interface 14 to transmit this confirmation message to the disconnected terminal. Thereby, the communication link between the call server 10 and the disconnected terminal is re-established. This confirmation message is shown as step S7 in FIG.

  In step ST12 of FIG. 4, the CPU 11 returns the disconnected terminal to the conference call using the communication link established by the process of step ST11. That is, the CPU 11 resumes the conference call process for the disconnected terminal for the conference call process being executed in another thread. As a result, the disconnected terminal enters the conference call again. Therefore, in step ST12, the computer having the CPU 11 as the center operates as a control unit that controls the conference processing unit so that the disconnected terminal participates in the conference call. After the process of step ST12, the CPU 11 returns to step ST1. The state in which the disconnected terminal is participating in the conference call again is shown as step S8 in FIG.

If the CPU 11 times out in the standby state of step ST9 and step ST10 in FIG. 4, the CPU 11 determines Yes in step ST10 and proceeds to step ST13. Here, the CPU 11 counts the number of times of timeout. Note that the flow of information when it is determined Yes in step ST10 is not shown in FIG.
In step ST13, the CPU 11 generates a disconnection request (BYE) and instructs the communication interface 14 to transmit the disconnection request to the disconnection terminal in order to cancel the call to the disconnection terminal. The disconnection request reaches the disconnected terminal via the local area network NW1 and the base station 20. The disconnect terminal stops the ringing tone in response to receiving the disconnect request.

  In step ST14, the CPU 11 confirms whether or not the number of timeouts is N or more. If the number of timeouts is not N or more, the CPU 11 determines No in step ST14, returns to step ST4, and checks in which cell of the base station 20 the disconnected terminal exists. If the CPU 11 determines No in step ST5 and further determines No in step ST6, it makes a call to the disconnected terminal again in step ST7. Note that the value of N is determined in advance by the administrator or operator of the call server 10. Alternatively, the value of N may be determined by the designer of the call server 10. The value of N determines the number of times to repeat the call to the disconnected terminal. If the number of timeouts is N or more, the CPU 11 determines Yes in step ST14 and ends the control process shown in FIG.

(effect)
As described above, when the disconnected terminal exists outside the service area, the call server 10 according to the first embodiment does not call the disconnected terminal again, and does not recall the disconnected terminal in the cell of any base station 20. Wait until you enter and recall. Therefore, it is possible to prevent a terminal that is out of service area from being recalled in vain.

  In addition, the call server 10 according to the first embodiment does not perform recall to the disconnected terminal when the congestion occurs in the base station 20 that forms the cell in which the disconnected terminal exists. Wait until the problem is resolved and recall. Therefore, it is possible to prevent the base station 20 from being recalled to a disconnected terminal that cannot be reconnected or is difficult to reconnect due to congestion.

  Further, when the cause of the abnormal disconnection is resolved, the call server 10 of the first embodiment does not perform any further recall when the recall to the disconnected terminal is repeated a predetermined number of times. In the case where a response is not made from the disconnected terminal even though the call is recalled after the cause of the abnormal disconnection is resolved, there is a high possibility that the response is not performed due to the circumstances of the operator of the disconnected terminal. There is a low possibility that a response will be made even if repeated recalls are performed under such circumstances. In addition, depending on the circumstances of the operator, it may be assumed that the operator does not want to be recalled many times. Therefore, by limiting the number of recalls to a predetermined number, it is possible to prevent useless recalls to the disconnected terminal. In addition, by setting the value of N to be small, the number of times of repeating the recall can be reduced.

[Second Embodiment]
In the second embodiment of the present invention, when a disconnected terminal receives a call from the call server 10, it automatically responds.
(Constitution)
The structure of 2nd Embodiment is the same as that of 1st Embodiment, and is shown in FIG.1 and FIG.2.
However, the auxiliary storage device 33 stores 0 or 1 as the terminal setting value. When the terminal setting value is 0, the CPU 11 performs a control process shown in FIG. 5 described later, and when the terminal setting value is 1, the CPU 11 does not perform the control process shown in FIG. The value of 0 or 1 is set in advance by an operator of the wireless terminal 30 or the like. When the terminal setting value is not set by the operator or the like, 1 or 0 is set as the default value for the terminal setting value.
Further, the program stored in the main memory 32 or the auxiliary storage device 33 includes a control program described with respect to the control process shown in FIG. As an example, the wireless terminal 30 is transferred to the user of the wireless terminal 30 with the control program stored in the main memory 32 or the auxiliary storage device 33. However, the wireless terminal 30 may be transferred to the user in a state where the control program is not stored in the main memory 32 or the auxiliary storage device 33. Then, the control program separately transferred to the user may be written into the main memory 32 or the auxiliary storage device 33 under the operation of the user or service person. The transfer of the control program at this time can be realized by recording on a removable recording medium such as a magnetic disk, a magneto-optical disk, an optical disk, or a semiconductor memory, or by downloading via a network.

(Operation)
The operation of the call system according to the second embodiment will be described with reference to FIGS. The information flow in the call system 1 of the second embodiment is the same as that of FIG. 3 of the first embodiment. The operation of the call server 10 is also the same as that in FIG. 4 of the first embodiment.
In the second embodiment, the wireless terminal 30 performs an operation based on FIG. 5 during a conference call. FIG. 5 is a flowchart of control processing by the CPU 31 of the wireless terminal 30. The CPU 31 executes this control based on the control program stored in the main memory 32 and the auxiliary storage device 33.

  In step ST21, the CPU 31 confirms whether the communication link established with the base station 20 is abnormally disconnected. That is, the CPU 31 disconnects the communication link without performing a normal operation such as when the operator of the wireless terminal 30 performs an operation for ending the call or when an operation for ending the call is performed in the call server 10. Make sure that it is not. If the communication link is not abnormally disconnected, CPU 31 determines No in step ST21 and repeats step ST21. When the communication link is abnormally disconnected, the CPU 31 determines Yes in step ST21 and proceeds to step ST22.

  In step ST22, the CPU 31 confirms whether or not the connection request is received by the wireless interface 34. If the connection request is not received, the CPU 31 determines No in step ST22 and proceeds to step ST23.

  In step ST23, the CPU 31 confirms whether a request other than the connection request is received by the wireless interface 34 or whether an operation is performed by the operator. If no request other than the connection request is received and no operation is performed by the operator, the CPU 31 determines No in step ST23 and returns to step ST22. Thus, the CPU 31 repeats step ST22 and step ST23 until a connection request or other request is received or an operation is performed. In the standby state of step ST22 and step ST23, if a request other than a connection request is received or an operation is performed by the operator, the CPU 31 determines Yes in step ST23 and determines that the request or the operation Perform other processing according to. Then, when a connection request is received in the standby state of steps ST22 and ST23, the CPU 31 determines Yes in step ST22 and proceeds to step ST24.

  In step ST24, the CPU 31 generates an incoming response (Ringing) and instructs the wireless interface 34 to transmit the incoming response to the call server 10. This incoming call response is shown as step S5 in FIG.

  In step ST25 of FIG. 5, the CPU 31 confirms whether or not the connection request received in step ST22 is transmitted from the call server 10. If the connection request is not transmitted from the call server 10, the CPU 31 determines No in step ST24 and performs the same operation as when a normal incoming call is received. If the connection request is transmitted from the call server 10, the CPU 31 determines Yes in step ST25 and proceeds to step ST26.

  In step ST <b> 26, the CPU 31 generates a success response (OK) to respond to the call from the call server 10, and instructs the wireless interface 34 to transmit this success response to the call server 10. This success response is shown as step S6 in FIG. By this processing, the disconnected terminal enters an off-hook state. Therefore, by performing this processing, the computer having the CPU 31 as the center operates as a response means that automatically responds to a call made by the call means.

In step ST27, the CPU 31 waits for the confirmation message (ACK) to be received by the wireless interface 34. This confirmation message is shown in step S7 of FIG. If CPU31 receives the confirmation message, it will determine Yes in step ST27, and will return to step ST21.
In response to receiving the confirmation message, the connection between the disconnected terminal and the call server 10 is re-established. As a result, the disconnected terminal can rejoin the conference call that was participating before the abnormal disconnection.

  Note that the call server 10 recognizes to which conference call connection request the response transmitted from each wireless terminal 30 corresponds. In addition, the disconnected terminal automatically returns a response to the incoming call from the call server 10. Therefore, the call server 10 can cause the disconnected terminal to participate in an arbitrary conference call. Here, since the call server 10 transmits a connection request for re-participating in the conference call that participated before the abnormal disconnection to the disconnected terminal, the disconnected terminal participated before the abnormal disconnection. You can rejoin the conference call.

(effect)
As described above, the wireless terminal 30 of the second embodiment automatically responds when called from the call server 10 when the connection with the base station is abnormally disconnected and becomes a disconnected terminal. Accordingly, the wireless terminal 30 can return to the conference call without the operator's operation. Thereby, even when the operator of the disconnected terminal does not notice that it has been abnormally disconnected, the disconnected terminal can rejoin the conference call.

[Third Embodiment]
In the third embodiment of the present invention, when the cause of abnormal disconnection is not resolved, information indicating disconnection is transmitted to the disconnection terminal using a network different from the local network NW1.
(Constitution)
FIG. 6 is a diagram illustrating an overall configuration of the call system 2 according to the third embodiment. The call system 2 includes a call server 10, a plurality of base stations 20, and a plurality of wireless terminals 30 as in the first embodiment. The configurations of the call server 10, the base station 20, and the wireless terminal 30 are the same as those in the first embodiment, and are the same as those shown in FIG. However, in the call system 2, the local network NW1 is connected to the public network NW2 via the gateway G2. In addition, each wireless terminal 30 can wirelessly communicate with the public network NW2 through the wireless interface 34. Each wireless terminal 30 is assigned a telephone number by the public network NW2. The public network NW2 is a communication network for use by an unspecified number of people, including a public switched telephone network (PSTN) and a public mobile telephone network. Further, the gateway G2 enables mutual communication between the local network NW1 and the public network NW2 by converting the protocols to each other. The local network NW1 is an example of a first network. The public network NW2 is an example of a second network.

  Note that the program stored in the main memory 12 or the auxiliary storage device 13 includes a control program described with reference to a control process shown in FIG. As an example, the call server 10 is transferred to an administrator or owner of the call server 10 with the control program stored in the main memory 12 or the auxiliary storage device 13. However, the call server 10 may be transferred to an administrator or owner in a state where the control program is not stored in the main memory 12 or the auxiliary storage device 13. Then, a control program separately transferred to an administrator or an owner may be written into the main memory 12 or the auxiliary storage device 13 under an operation by the administrator, owner, or service person. The transfer of the control program at this time can be realized by recording on a removable recording medium such as a magnetic disk, a magneto-optical disk, an optical disk, or a semiconductor memory, or by downloading via a network.

(Operation)
The information flow of the call system 2 will be described with reference to FIG. FIG. 7 is a sequence diagram showing a flow of information in the call system 1. Note that FIG. 7 does not cover the information flow in the call system 1, and there may be an information flow (not shown). Moreover, although only one base station 20 is shown in FIG. 7, there are typically a plurality of base stations 20. In FIG. 7, the wireless terminal 30 shows only a disconnected terminal, and a plurality of wireless terminals 30 actually participate in the conference call. Note that although two disconnected terminals are shown in FIG. 7, the same terminals are shown.
The operation of the call server 10 will be described with reference to FIG. FIG. 8 is a flowchart of control processing by the CPU 11 of the call server 10. The CPU 11 executes this control based on the control program stored in the main memory 12 and the auxiliary storage device 13.

Steps S1 and S2 in FIG. 7 are the same as steps S1 and S2 in FIG. Further, step ST1 to step ST9, step ST11, and step ST12 of FIG. 8 are also the same as the processing of FIG.
However, if the CPU 11 determines Yes in step ST5, the process proceeds to step ST31. If the CPU 11 determines Yes in step ST6, the CPU 11 proceeds to step ST31. And CPU11 repeats step ST9, when it determines with No in step ST9.

  In step ST31, the CPU 11 confirms whether or not a timeout has occurred. That is, the CPU 11 determines that a time-out has occurred when a predetermined time elapses after the process of step ST3 is completed. If the time-out has not occurred, the CPU 11 determines No in step ST31 and returns to step ST4. Thus, CPU11 repeats step ST4-step ST6 and step ST31 until it determines with No in step ST6. When the time-out has occurred, the CPU 11 determines Yes in step ST31 and proceeds to step ST32. In step ST31, the CPU 11 may determine that time-out has occurred when step ST4 is repeated a predetermined number of times.

  In step ST32, the CPU 11 makes a call to the disconnected terminal via the public network NW2. That is, the CPU 11 generates a connection request (INVITE) including the telephone number of the disconnected terminal, and instructs the communication interface 14 to transmit this connection request to the gateway G2. This connection request is shown as step S11 in FIG.

  In step S12, the gateway G2 sends a push signal representing the telephone number of the disconnected terminal to the public network NW2 in response to receiving the connection request transmitted from the call server 10.

  In step S13, the public network NW2 transmits a call signal to the disconnected terminal in response to receiving the push signal transmitted from the gateway G2. The disconnected terminal that has received the calling signal emits a ringing tone. In response to this, the operator of the disconnected terminal places the disconnected terminal off-hook when responding to an incoming call.

  In step S14, the disconnected terminal sends a response signal to the public network NW2 in response to being off-hook.

  In step S15, the public network NW2 forms a communication path between the disconnected terminal and the gateway G2 in response to receiving the response signal transmitted from the disconnected terminal. As a result, the disconnected terminal and the gateway G2 are connected via the public network NW2.

  In step S16, the gateway G2 generates a success response (OK) indicating that the connection is permitted in response to the connection between the disconnected terminal and the gateway G2, and transmits this success response to the call server 10. .

  On the other hand, in step ST <b> 33 of FIG. 9, the CPU 11 confirms whether or not a success response has been received by the communication interface 14. If the success response is received, the CPU 11 determines Yes in step ST33 and proceeds to step ST34.

  In step ST34, the CPU 11 generates a confirmation message (ACK) and instructs the communication interface 14 to transmit this confirmation message to the gateway G2. As a result, a communication session between the call server 10 and the gateway G2 is established. With this communication session and the communication path formed as described above via the public network NW2, the call server 10 and the disconnected terminal are in a state where they can talk to each other.

  In step ST <b> 35, the CPU 11 instructs the communication interface 14 to transmit a voice signal representing a voice indicating that the communication link is abnormally disconnected to the disconnected terminal. The voice signal transmitted from the communication interface 14 reaches the disconnected terminal via the local network NW1, the gateway G2, and the public network NW2. This audio signal is shown as step S18 in FIG. When performing the process of step ST35 of FIG. 9, the computer having the CPU 11 as the center operates as a transmission means.

  In step ST36, the CPU 11 generates a disconnection request (BYE) to end the call with the disconnected terminal, and instructs the communication interface 14 to transmit the disconnection request. CPU11 complete | finishes the control processing shown in FIG. 8 after the process of step ST36. This disconnection request is shown as step S19 in FIG.

  On the other hand, in step S20, the gateway transmits a disconnection signal to the public network NW2 in response to receiving the connection request transmitted from the call server 10.

  In step S21, the public network NW2 transmits a call termination signal to the disconnected terminal in response to receiving the disconnected signal. Thereby, the communication path formed via the public network NW2 between the disconnected terminal and the gateway G2 is disconnected.

(effect)
As described above, the call server 10 according to the third embodiment can connect to a disconnected terminal when the disconnected terminal is out of service area or when a base station that can be connected to the disconnected terminal is congested. When it is estimated that there is no such error, the disconnection terminal can be notified of the abnormal disconnection through communication via the public network NW2. Therefore, even when the call server 10 cannot reconnect to the disconnected terminal via the local network NW1, the call server 10 informs the operator of the disconnected terminal that the communication link between the disconnected terminal and the base station has been abnormally disconnected. Can be notified.

  The embodiment described above can be modified as follows.

  In the second embodiment, the CPU 11 confirms whether or not the connection request is from the call server 10 in step ST25. However, the CPU 11 may proceed to step ST26 without performing this process.

  In the third embodiment, the call server 10 transmits information indicating that the call is abnormally disconnected by the audio signal to the disconnected terminal. However, the call server 10 may use SMS (short message service) or the like to transmit information indicating that the abnormal disconnection has occurred based on character information to the disconnected terminal.

  In the third embodiment, the call server 10 transmits information indicating that the call has been abnormally disconnected to the disconnected terminal via the public network NW2. However, when the disconnected terminal is a disconnected terminal that can be connected to the Internet, the call server 10 may transmit information indicating that the abnormal connection has been disconnected via the Internet. As a method of transmitting via the Internet, e-mail or push notification is used, for example. In this case, the Internet is the second network.

  In the embodiment, SIP is used as a protocol for performing call control, but H.264 recommended by ITU-T (International Telecommunication Union Telecommunication Standardization Sector). An aspect using other protocols such as a protocol defined in H.323 may be used. In the embodiment, a digital line is used, but an analog line may be used. In this case, a protocol corresponding to the analog line is used.

  In the embodiment, the DECT method or the TETRA method is used for wireless connection between the base station 20 and the wireless terminal 30, but a method other than the DECT method and the TETRA method such as PHS may be used.

  In addition, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

DESCRIPTION OF SYMBOLS 1, 2 ... Call system, 10 ... Call server, 11, 31 ... CPU, 12, 32 ... Main memory, 13, 33 ... Auxiliary storage device, 14 ... Communication interface, 15, 35 ... Bus, 20 ... Base station, 21 DESCRIPTION OF SYMBOLS ... Control part, 22 ... Communication part, 23 ... Wireless communication part, 24 ... Disconnection detection part, 30 ... Wireless terminal, 34 ... Wireless interface.

Claims (9)

A conference processing means for joining the wireless terminal to a conference call via a communication link established between the base station and the wireless terminal wirelessly connected;
Detecting means for detecting that the communication link is disconnected between the wireless terminal and the base station;
When the detection unit detects that the communication link is disconnected, a determination unit that determines the cause of the disconnection;
When the cause determined by the determining means is resolved, a calling means for calling the wireless terminal;
Control means for controlling the conference processing means to cause the wireless terminal to participate in the conference call when a communication link is re-established with the wireless terminal in response to the call. Call server.   2. The call server according to claim 1, wherein the determination unit determines the cause of the disconnection by using the occurrence of congestion in the base station as one of candidates for the cause of the disconnection.   3. The determination unit according to claim 1, wherein the determination unit determines the cause of disconnection, assuming that the wireless terminal is not in an area where wireless communication with the base station is possible, as one of the candidates for disconnection. 4. Call server. The conference processing means causes the wireless terminal to participate in a conference call via a communication link established on a first network,
If the cause of the disconnection determined by the determination unit is not resolved within a predetermined period, the transmission unit transmits information indicating that the communication link has been disconnected to the wireless terminal via the second network. The call server according to any one of claims 1 to 3, further comprising: Further comprising setting means for setting validity or invalidity of the operation of the calling means,
The call server according to any one of claims 1 to 4, wherein the calling unit does not make a call when the setting unit is set to be invalid.   The call server according to any one of claims 1 to 5, wherein the calling unit repeats a call a predetermined number of times until the wireless terminal responds to the call. A call system comprising a base station, a wireless terminal wirelessly connected to the base station, and a call server,
The wireless terminal is capable of communicating with the call server using a communication link established with the call server,
The base station comprises a notification means for notifying the call server that the communication link is disconnected when a communication link with the wireless terminal is disconnected;
The call server is
Conference processing means for causing the wireless terminal to participate in a conference call via the communication link;
Detecting means for detecting that the communication link is disconnected between the wireless terminal and the base station by notification by the notifying means;
When the detection unit detects that the communication link is disconnected, a determination unit that determines the cause of the disconnection;
When the cause determined by the determining means is resolved, a calling means for calling the wireless terminal;
Control means for controlling the conference processing means to cause the wireless terminal to participate in the conference call when a communication link is re-established with the wireless terminal in response to the call. A call system.   The call system according to claim 7, wherein the wireless terminal includes response means for automatically responding to a call made by the call means.   The program which makes the computer with which the said call server performs the process by the said each means with which the call server of any one of Claims 1 thru | or 6 is provided.