JP2008219745A - Radio communication system, radio communication server, radio communication client terminal and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently detect that a client terminal is out of an area in a radio communication system. <P>SOLUTION: In the radio communication system, a server and a client terminal are connected via a radio communication network. The server 10 is provided with a presence information receiving part 31 for receiving presence information from the client terminal 40, a health check information transmitting part 32 for transmitting health check information to the client terminal, together with the information of the transmission cycle; a health check information response receiving part 33 for receiving a response to the health check information; and an out-of-area detection part for detecting that the client terminal, whose response to the health check information is not received is positioned outside the area, where communication is enabled. The client terminal 40 is provided with an out-of-area detecting part 48 for detecting that the terminal is positioned outside the communication area, when it does not receive the health check information during prescribed standby time set, based on the transmission cycle of the health check information. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wireless communication system, a wireless communication server, a wireless communication client terminal, and a wireless communication method.

  In general, in a system consisting of a SIP (Session Initiation Protocol) server / client having a presence function compliant with RFC3261 and RFC3265, a SIP client terminal periodically generates a subscription with a time limit with the SIP server, Notify presence status such as online, offline, busy. When there is a SIP client terminal whose subscription expiration date has expired in the absence of a subscription update request, the SIP server discards the expired subscription and the SIP client terminal is offline to another SIP client terminal. It has a function of notifying that the status has been reached.

  Conventionally, in a SIP server / client system having a presence function, when the SIP client terminal is a wireless mobile terminal that communicates via a wireless network, a health check is performed from the SIP server side to the SIP client terminal in a short cycle, and a response is received. If it is not, it is determined that the terminal is out of the wireless network area, and the event subscription is canceled and an offline notification is made to detect at an early stage that the SIP client terminal is out of the wireless network area. It was broken.

  However, in the above conventional technique, if the SIP client terminal is determined to be out of service area by the SIP server while the SIP client terminal is moving out of the wireless network area, the subscription is discarded. The SIP client terminal that has returned to the service area cannot notify the presence status. For this reason, the SIP client terminal that has returned to the area needs to generate a subscription again, and the SIP client terminal configures the subscription every time it returns to the area or confirms whether the subscription is valid and subscribes. It was necessary to regenerate the application.

  In addition, when a SIP client terminal goes out of the wireless network area for a very short time and then returns to the area immediately, the SIP client terminal itself is less likely to be determined to be out of service area by the SIP server. Since there is no means for knowing whether or not the terminal has been detected out of range, it is necessary to always confirm and regenerate the subscription. In many cases, the validity check and regeneration of the subscription are useless communication, and there is a drawback that the communication resource is consumed inefficiently.

  In addition, the SIP client terminal itself needs to monitor its own network interface card status or wireless strength in a very short period in order to know that its own terminal has gone out of the network and returned to the outside of the network. There were also drawbacks.

  Therefore, the present invention has been made in view of the above problems, and a new and improved wireless communication system, wireless communication server, wireless communication client terminal, and wireless communication method capable of efficiently detecting out-of-service of a client terminal Is to provide.

  In order to solve the above problems, according to an aspect of the present invention, there is provided a wireless communication system in which a server and a client terminal are connected via a wireless communication network, wherein the server represents a state of the client terminal. A presence information receiving unit that receives presence information from the client terminal, and health check information for confirming whether or not the client terminal is within a communication range, together with information on a transmission cycle of the health check information, the client terminal A health check information transmission unit that transmits to the health check information, a health check information response reception unit that receives a response to the health check information, and the client terminal that has not received a response to the health check information is located out of service area An out-of-service detection unit for detecting When the client terminal does not receive the health check information between a presence information transmitting unit that transmits the presence information to the server and a predetermined waiting time set based on a transmission cycle of the health check information. There is provided a wireless communication system including an out-of-service detection unit that detects being located outside the communication service area.

  According to the above configuration, the server receives presence information indicating the state of the client terminal from the client terminal, and the health check information for confirming whether or not the client terminal is in the communication range is the health check information. It transmits to the said client terminal with the information of a transmission period. Then, it is detected that the client terminal that has not received a response to the health check information is located out of service area where communication is not possible. Further, when the health check information is not received during a predetermined standby time set based on the health check information transmission cycle, the client terminal detects that the client terminal is out of the communication range. Since the health check information is sent from the server side with the health check information transmission period and the health check reception is monitored on the client terminal side, the client terminal knows whether its own terminal is detected out of range by the server. Therefore, it is possible to reduce the amount of wasted communication when returning to the service area.

  The server may further include a presence information transmission unit that transmits the presence information received from a specific client terminal to another client terminal. According to this configuration, the client terminal can acquire presence information of other client terminals via the server.

  The server may further include a period changing unit that changes a transmission period of the health check information in accordance with a traffic congestion state in the server or a usage form of the client terminal. According to such a configuration, it is possible to optimally change the transmission cycle of the health check information only by changing the value specified on the server side in accordance with conditions such as strictness of out-of-service detection. Further, the waiting time of the client terminal can be easily changed by designation on the server side.

  Further, when the server detects that the client terminal is located out of service area where communication is not possible, the server cancels registration of communication with the client terminal, and the client terminal cannot communicate with the service area detection unit. After it is detected that it is located outside the service area, communication registration with the server may be performed again. According to this configuration, in the server, when it is detected that the client terminal is located out of service area where communication is not possible, the registration of communication with the client terminal can be discarded and the client can be made offline. In addition, since the client terminal performs registration of communication with the server again after it is detected that the client terminal is located outside the communication range by the out-of-service detection unit, it is possible to return to communication after detecting out-of-service.

  In order to solve the above problem, according to another aspect of the present invention, a server connected to a client terminal via a wireless communication network, the presence information indicating the state of the client terminal is transmitted to the client terminal. Health check information for transmitting to the client terminal, together with information on a transmission period of the health check information, a presence information receiving unit that receives from the health check information for confirming whether the client terminal is within communication range A transmission unit, a health check information response reception unit that receives a response to the health check information, an out-of-range detection unit that detects that the client terminal that has not received a response to the health check information exists outside the communication range, The amount of traffic congestion in the server or the client Depending on the usage of the cement terminal, wherein a cycle changing unit for changing the transmission period of the health check information, the wireless communication server comprises a provided.

  According to the above configuration, presence information indicating the state of the client terminal is received from the client terminal, and the health check information for confirming whether or not the client terminal is in the communication range is information on the transmission cycle of the health check information. And transmitted to the client terminal. The client terminal that has not received a response to the health check information is detected as being outside the communication range. Then, the transmission cycle of the health check information is changed according to the traffic congestion state of the server or the usage mode of the client terminal. According to such a configuration, it is possible to change the transmission cycle of the health check information only by changing the value specified on the server side, and the health check information can be changed according to the congestion state of the traffic or the usage form of the client terminal. Can be optimally changed.

  In addition, a presence information transmission unit that transmits the presence information received from a specific client terminal to another client terminal may be further provided. According to this configuration, according to such a configuration, the client terminal can acquire presence information of other client terminals via the server.

  In order to solve the above problem, according to another aspect of the present invention, a client terminal connected to a server via a wireless communication network, wherein the client terminal sends a status of the terminal to the server. A health information for confirming whether or not the client terminal is within a communicable area, together with information on a transmission cycle of the health check information, is received from the server. When the health check information is not received between the health check information receiving unit and a predetermined waiting time set based on the transmission period of the health check information, it is detected that the mobile terminal is out of service area where communication is not possible. An out-of-service detection unit is provided.

  According to the above configuration, presence information indicating the state of the own terminal is transmitted to the server, and the health check information for confirming whether the client terminal is within a communicable range is information on the transmission cycle of the health check information. And received from the server. Then, when the health check information is not received during a predetermined waiting time set based on the transmission cycle of the health check information, it is detected that the mobile phone is out of service area where communication is not possible. Therefore, by monitoring whether the health check is received on the client terminal side, it becomes possible for the client terminal to know whether its own terminal is detected out of range by the server, and it is possible to suppress useless traffic when returning to the range. It becomes possible.

  Further, after detecting that the out-of-service detection unit is located outside the in-service area where communication is not possible, registration of communication with the server may be performed again. According to such a configuration, after it is detected that the mobile phone is located outside the communication area, the communication with the server is registered again, so that it is possible to return to the communication after the out-of-service detection.

  Further, the health check information receiving unit may receive the transmission cycle changed according to a traffic congestion state in the server or a usage form of the client terminal. According to such a configuration, it is possible to change the transmission cycle of the health check information only by changing the value specified on the server side, and the health check can be performed according to the traffic congestion state or the usage form of the client terminal. It is possible to optimally change the information transmission cycle. Further, the waiting time of the client terminal can be easily changed by designation on the server side.

  In order to solve the above problem, according to another aspect of the present invention, there is provided a wireless communication method in a system in which a server and a client terminal are connected via a wireless communication network, the state of the client terminal being changed. Transmitting the presence information representing from the client terminal to the server, and health check information for confirming whether or not the client terminal is in a communication range, together with information on a transmission cycle of the health check information. Transmitting to the client terminal, the client terminal transmitting a response to the health check information to the server, and the server communicating with the client terminal that has not received a response to the health check information. Steps to determine that you are outside the service area When the client terminal does not receive the health check information during a predetermined waiting time set based on the transmission period of the health check information, the client terminal detects that the terminal is out of the communication range. A wireless communication method comprising the steps of:

  According to the above configuration, the presence information indicating the state of the client terminal is transmitted from the client terminal to the server, and the health check information for confirming whether the client terminal is in the communication range is transmitted along with the information of the transmission cycle. Sent from the server to the client terminal. A response to the health check information is transmitted from the client terminal to the server, and the client terminal that has not received a response to the health check information at the server is determined to be located outside the communication range. Further, when the client terminal does not receive the health check information during a predetermined standby time set based on the transmission period of the health check information, it is detected that the own terminal is out of the communication range. Therefore, in order to send the health check information from the server side with the transmission period of the health check information, and monitor the presence or absence of the health check reception on the client terminal side, whether the client terminal is detected out of range to the server It becomes possible to know the amount of wasted communication when returning to the service area.

  According to the present invention, it is possible to provide a new and improved wireless communication system, wireless communication server, wireless communication client terminal, and wireless communication method capable of efficiently detecting out-of-service of a client terminal.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

(First embodiment)
FIG. 1 is a schematic diagram showing a configuration of a wireless communication system according to an embodiment of the present invention. The present invention includes a SIP server 10, a wireless access point 12, and a SIP client terminal 40. The SIP client terminal 40 communicates with the SIP server 10 via the wireless access point 12 when in a range where radio waves from the wireless access point 12 can reach. Then, the SIP client terminals 40 mutually notify their own presence status via the SIP server 10.

  In FIG. 1, an area A centering on the wireless access point 12 indicates a range where radio waves from the wireless access point 12 reach the SIP client terminal 40, and the area A is an area within which communication is possible. The outside of the area A is a range where radio waves from the wireless access point 12 do not reach and is out of service area where communication is impossible. When the SIP client terminal 40 exists in the area A, the SIP server 10 and the SIP client terminal 40 can communicate with each other via the wireless access point 12.

  FIG. 2 is a schematic diagram showing the configuration of the SIP client terminal 40. 2A shows the appearance of the SIP client terminal 40, and FIG. 2B shows the functional blocks of the SIP client terminal 40. As shown in FIG. As shown in FIG. 2, the SIP client terminal 40 includes a display screen 42, on which the owner name, current position, and presence status of other SIP client terminals 40 are displayed.

  The presence status is various statuses of other SIP client terminals 40 such as online, offline, talking, and taking in. In the example of FIG. 2, a predetermined symbol (○, ×, etc.) is displayed on the left side of the owner name. The presence status is displayed.

  FIG. 3 is a schematic diagram showing the configuration of the SIP server 10. As shown in FIG. 3, the SIP server 10 includes a registrar server 20 that manages registration (REGISTER) information of the SIP client terminal 40 and a presence server 30 that manages presence information of the SIP client terminal 40. And the presence server 30 are configured to exchange information with each other.

  As shown in FIG. 3, the registrar server 20 and the presence server 30 that constitute the SIP server 10 include functional blocks each constituted by a computer and software (program) that operates on the computer. The registrar server 20 includes a registration information reception / management unit 22 that receives and manages registration information from the SIP client terminal 40. The presence server 30 also includes a presence information receiving unit 31 that receives presence information from the SIP client terminal 40, a health check information transmitting unit 32 that transmits health check information, which will be described later, to the SIP client terminal 40 together with its transmission cycle, and health check information. A health check information response receiving unit 33 that receives a response to the SIP client terminal 40, an out-of-service detection unit 34 that detects that the SIP client terminal 40 that has not received a response to the health check information is located out of service area, Presence information transmission unit 35 that transmits the presence information received from SIP client terminal 40 to other SIP client terminals 40, the traffic volume in SIP server 10 or the usage mode of SIP client terminal 40. Te has a function block, such as cycle changing unit 36 for changing the period of transmitting the health check information.

  Each functional block of the SIP client terminal 40 is constituted by a computer and software operating on the computer. As shown in FIG. 2A, the SIP client terminal 40 includes a presence information transmission unit 44 that transmits presence information to the SIP server 10, and health during a predetermined waiting time including a start-up period or a transmission period of health check information. When the check information is not received, the out-of-service detection unit 46 that detects that the communication device is out of service and the out-of-service detection unit 46 detects that the communication with the SIP server 10 is detected. Each function block includes a communication registration unit 48 for registering communication between them and a display control unit 50 for displaying presence information on the display screen 42.

  FIG. 4 is a sequence diagram showing an operation in which the SIP client terminal 40 notifies the presence status to other SIP client terminals 40 via the SIP server 10. In the communication sequence using SIP in FIG. 4, the processing other than the processing of F3 and F4 is in accordance with RFC3261 and RFC3265.

  In FIG. 4, the SIP client terminal 40A transmits a registration (REGISTER) request to the SIP server 10 at the time of activation (F1). The registrar server 20 that has received the registrar request returns a normal response to the SIP client terminal 40 (F2).

  Upon receiving the registration request of the SIP client terminal 40A, the presence server 30 transmits two types of requests to the SIP client terminal 40A.

  The first request is F3 and F4 which are the first health check requests to the SIP client terminal 40A, and details will be described later.

  The second request is a subscription generation for notifying the presence status of the SIP client terminal 40A to the other SIP client terminals 40B, 13C, 13D, and a subscription (SUBSCRIBE) request (F5) transmitted from the presence server 30. After receiving the normal response (F6), the SIP client terminal 40A notifies the presence server 30 of a status notification (NOTIFY) indicating that its presence status is “online” (F7). A response (F8) is received.

  The presence server 30 that has received the presence status notification from the SIP client terminal 40A distributes the presence status of the SIP client terminal 40A to the other SIP client terminals 40B to 13D by a notification (NOTIFY) request (F9) (F9). .

  The SIP client terminal 40A transmits a subscription (SUBSCRIBE) request (F10) to the presence server 30 in order to display the presence status of the other SIP client terminals 40B to 13D on the display screen 42 of its own terminal. F11) and presence status notifications (NOTIFY) of the SIP client terminals 40B to 13D to be displayed are received. The presence server 30 receives a normal response from the SIP client terminal 40A (F13).

  Next, a mechanism for detecting that the SIP client terminal 40A is out of the service area when the SIP client terminal 40A has moved out of service area will be described with reference to the sequence diagram of FIG. The presence server 30 periodically transmits health check information using an option request to the SIP client terminal 40A registered (REGISTER), and performs health check (F21, F23, F25). In this option request, the health check cycle in the presence server 30 is added as a SIP-specific extension header, thereby informing the SIP client terminal 40 that is the health check target of the next health check transmission timing.

  The SIP client terminal 40A that has received the health check information stores the transmission cycle (health check cycle) of the health check information given to the option request, and returns a normal response (F22, F24). FIG. 8 shows an example of the option request and normal response SIP message header used here.

  When a normal response is returned from the SIP client terminal 40A, the presence server 30 determines that the terminal is within a communicable range. When there is no response from the SIP client terminal 40A to the health check, the presence server 30 repeats the retransmission of the request according to the RFC 3261 SIP retransmission mechanism (F26, F27). If there is still no response to the retransmitted option request, the presence server 30 determines that the terminal is out of serviceable area, discards the sub-plication with the SIP client terminal 40A, and receives another SIP client. The fact that the SIP client terminal 40A is in the “offline” state is distributed to the terminals 40B to 13D using a presence state notification (NOTIFY) request (F28). The other SIP client terminals 40B to 13D display on the display screen 42 that the SIP client terminal 40A is in the “offline” state. The presence server 30 does not perform a health check on the SIP client terminal 40 that is offline.

  FIG. 6 is a sequence diagram illustrating a case where the SIP client terminal 40 returns to a communicable area from a noncommunicable area. The SPI client terminal 40A that has received the health check (F31) by the option request from the presence server 30 sets the value of the SIP retransmission timeout timer (Timer F) (usually 32 seconds) in the health check cycle given to the option (OPTIONS) request. ) Is added, and a health check reception timer from the presence server 30 is started.

  The health check reception timer is reset when the SIP client terminal 40A receives a health check from the presence server 30, and starts counting by the timer anew using the received health check cycle.

  Since the time check by the health check reception timer cannot be started unless the SIP client terminal 40 receives the first health check request from the presence server 30, the presence server 30, as shown in F 3 in FIG. Immediately after the SIP client terminal 40A registers (REGISTER), the first health check is performed.

  When the SIP client terminal 40A that has started counting time by the health check reception timer does not receive the next health check information from the presence server 30 within a predetermined waiting time (F35), the SIP terminal is determined to be out of service by the presence server 30. Then, it is determined that the subscription is discarded, and the registration (REGISTER) sequence is performed again to regenerate the subscription (F37 to F45).

  On the other hand, when the next health check information is received from the presence server 30 within a predetermined waiting time, the SIP client terminal 40A can determine that the subscription has not been discarded, so it is necessary to perform the registration (REGISTER) sequence again. Absent. Therefore, it is possible to suppress a useless communication amount.

  As described above, according to the first embodiment, since the health check period is given and the health check information is transmitted from the SIP server 10 side and the presence or absence of the health check reception is monitored on the SIP client terminal 40 side, The client terminal 40 can know whether or not the own terminal has been detected out of service by the SIP server 10, and can suppress a useless amount of communication when returning from the service area.

  In addition, since the SIP client terminal 40 only monitors whether or not a health check is received and does not need to know exactly whether the terminal is out of service area or service area, the SIP client terminal 40 has extremely high network interface card status or wireless strength. It is possible to eliminate the need for monitoring in a short cycle.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the second embodiment, the health check cycle is variable in the first embodiment. As described above, on the SIP client terminal 40 side, the waiting time by the health check reception timer is set based on the health check period designated by the SIP server 10, so the value specified by this timer is arbitrarily set by the SIP server 10 side. Can be specified.

  As a result, the value specified on the SIP server 10 side can be changed according to conditions such as the system scale, the load on the SIP server 10 and the strictness of out-of-service detection without changing the software and setting values on the SIP client terminal 40 side. Only by doing this, the timer value of the SIP client terminal 40 can be easily changed.

  FIG. 7 shows a sequence example when the timer value is changed according to the load condition of the SIP server 10 in the present embodiment. When the traffic volume of the SIP server 10 exceeds the congestion detection threshold, the SIP server 10 extends the health check cycle from normal until the congestion state is settled. As a result, it is possible to reduce the amount of health check communication, and to exit the congestion state at an early stage.

  In the second embodiment, an example in which congestion control is performed by dynamically changing the health check cycle on the SIP server 10 side has been described, but the change of the health check cycle can be applied to other cases.

  For example, when the usage form of the mobile terminal corresponding to the SIP client terminal 40 is used while moving mainly like a smartphone, the mobile terminal moves between the area where the SIP client terminal 40 can communicate and the area outside the area where the communication is impossible. It is assumed that On the other hand, when the SIP client terminal 40 is used at one place without moving like a notebook personal computer or the like, the possibility of going out of service becomes low. When such a plurality of usage forms coexist, a priority is set for the SIP client terminal 40 that detects out of service, a short health check cycle is set for the SIP client terminal 40 with a high priority, and a terminal with a low priority It is possible to improve communication efficiency by setting a long health check cycle.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

It is a schematic diagram which shows the structure of the radio | wireless communications system which concerns on one Embodiment of this invention. It is a schematic diagram which shows the structure of a SIP client terminal. It is a schematic diagram which shows the structure of a SIP server. It is a sequence diagram which shows the operation | movement which a SIP client terminal notifies presence status to another SIP client terminal via a SIP server. It is a sequence diagram which shows the mechanism which detects that it is out of service area when a SIP client terminal moves out of service area where communication is impossible. It is a sequence diagram which shows the case where the SIP client terminal returns from the out-of-service area where communication is possible to the within-communication area. In the 2nd Embodiment of this invention, it is a sequence diagram which shows the case where a timer value is changed with the load conditions of a SIP server. It is a schematic diagram which shows the example of the SIP message header of an option request | requirement and a normal response.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 SIP server 40 SIP client terminal 22 Registration information reception / management part 31 Presence information reception part 32 Health check information transmission part 33 Health check information response reception part 34 Out-of-range detection part 35 Presence information transmission part 36 Period change part 44 Presence information transmission part 46 Out-of-service detection unit 48 Communication registration unit

Claims (10)

A wireless communication system in which a server and a client terminal are connected via a wireless communication network,
Said server;
A presence information receiving unit that receives presence information representing the state of the client terminal from the client terminal;
A health check information transmission unit that transmits health check information for confirming whether or not the client terminal is in a communication area together with information on a transmission cycle of the health check information to the client terminal;
A health check information response receiving unit that receives a response to the health check information;
An out-of-range detection unit that detects that the client terminal that has not received a response to the health check information is located outside the out-of-service area,
The client terminal;
A presence information transmission unit for transmitting the presence information to the server;
An out-of-service detection unit that detects being out of communication range when the health check information is not received during a predetermined waiting time set based on a transmission period of the health check information;
A wireless communication system comprising:   The wireless communication system according to claim 1, wherein the server further includes a presence information transmission unit that transmits the presence information received from the specific client terminal to another client terminal.   3. The server according to claim 1, further comprising a period changing unit that changes a transmission period of the health check information according to a congestion state of a traffic amount in the server or a usage form of the client terminal. The wireless communication system according to 1. When the server detects that the client terminal is located out of service area where communication is impossible, the server cancels registration of communication with the client terminal,
The registration of communication with the server is performed again after the client terminal is detected by the out-of-service detection unit to be located outside the out-of-service communication area. 5. The wireless communication system according to 1. A server connected to a client terminal via a wireless communication network,
A presence information receiving unit that receives presence information representing the state of the client terminal from the client terminal;
A health check information transmission unit that transmits health check information for confirming whether or not the client terminal is in a communication area together with information on a transmission cycle of the health check information to the client terminal;
A health check information response receiving unit that receives a response to the health check information;
An out-of-range detection unit that detects that the client terminal that has not received a response to the health check information is outside the communication range;
A period changing unit that changes a transmission period of the health check information in accordance with a traffic congestion state in the server or a usage form of the client terminal;
A wireless communication server comprising:   The wireless communication server according to claim 5, further comprising a presence information transmission unit that transmits the presence information received from a specific client terminal to another client terminal. A client terminal connected to a server via a wireless communication network;
The client terminal;
A presence information transmission unit for transmitting presence information indicating the state of the terminal to the server;
A health check information receiving unit that receives health check information for confirming whether or not the client terminal is within a communicable area from the server together with information on a transmission cycle of the health check information;
An out-of-service detection unit that detects that the communication terminal is out of service when communication is not possible when the health check information is not received during a predetermined waiting time set based on the transmission period of the health check information;
A wireless communication client terminal comprising:   8. The wireless communication client terminal according to claim 7, wherein communication with the server is performed again after it is detected by the out-of-service detection unit that the mobile phone is located out of service area where communication is not possible. 9.   The wireless communication according to claim 7 or 8, wherein the health check information receiving unit receives the transmission period changed according to a traffic congestion state in the server or a usage form of the client terminal. Communication client terminal. A wireless communication method in a system in which a server and a client terminal are connected via a wireless communication network,
Transmitting presence information representing the state of the client terminal from the client terminal to the server;
Transmitting health check information for confirming whether or not the client terminal is in a communication range from the server to the client terminal together with information on a transmission cycle of the health check information;
The client terminal sending a response to the health check information to the server;
The server determines that the client terminal that has not received a response to the health check information is located outside the communication range;
Detecting that the client terminal is out of communication range when the client terminal does not receive the health check information during a predetermined waiting time set based on a transmission cycle of the health check information. When;
A wireless communication method comprising:

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