Call processing control device, mobile communication system, method for restricting reception of call connection request, and readable medium

A call processing control device (20), upon receiving a call connection request (32) from a mobile terminal (30), performs connection setup processing. The call processing control device (20) is equipped with: a call type determination unit (21) that determines the call type of the call connection request (32) and classifies, based on the determination result, the call connection request (32) as a request that is to be subjected to acceptance determination or as a request that is not; and an acceptance determination unit (22) that determines whether to or not to accept the call connection request (32) that has been classified as a request to be subjected to the acceptance determination. Thereby, congestion can be suppressed while suppressing influence on high-priority call connection requests.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/JP2014/003523 filed Jul. 2, 2014, claiming priority based on Japanese Patent Application No. 2013-173225, filed Aug. 23, 2013, the contents of all of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a call processing control device, a mobile communication system, a method for restricting reception of call connection request, and a program (readable medium).

BACKGROUND ART

Patent Literature (PTL) 1 discloses a mobile communication system that is capable of achieving an improvement in a utilization rate by doing a promotion that presents a favorable term in terms of price or the like to users when the utilization rate of the network of the mobile communication system is low. In the mobile communication system, by receiving utilization promotion information from a core network, a radio base station informs of the utilization promotion information to terminals under the radio base station.

On the other hand, Patent Literature 2 discloses a mobile packet communication system that makes it possible to restrict an increase in transmission delay and prevent a quality deterioration while improving the utilization efficiency of a radio channel. The packet communication system includes a storage means that stores information on currently set packet calls, a new call judging means that, in receiving a setup request of a packet call transmitted by a mobile station, judges whether or not the packet call is a new call on the basis of the information stored in the storage means, and an acceptance determination means that determines whether or not to accept the setup request of a packet call that is judged as a new call.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In the case of the mobile communication system disclosed in PTL 1, there is a possibility that a plurality of terminals that have received utilization promotion information make a lot of call connection requests simultaneously, causing instantaneous congestion on radio base stations and the core network. Since carrying out congestion prevention for the above case by using a method for restricting reception of setup requests as disclosed in PTL 2 causes the reception of new calls to be restricted regardless of call types of call connection requests, a situation may take place in which both a high-priority call connection request, such as an emergency call, and a call connection request the priority of which is supposed to be low, such as a call connection request transmitted with utilization promotion information as a trigger, are denied acceptance in the same way.

The present invention is made in consideration of the above-described problem, and has an object to provide a call processing control device, a mobile communication system, a method for restricting reception of call connection requests, and a program that are capable of suppressing congestion while suppressing influence on high-priority call connection requests.

Solution to Problem

A call processing control device of the present invention accepts a call connection request(s) from a mobile terminal(s) and performs connection setup processing. The call processing control device comprises a call type determination means for determining a call type(s) of a call connection request(s) and, based on a determination result(s), classifying the call connection request(s) as either a subject(s) for acceptance determination or not a subject(s) for acceptance determination, and an acceptance determination means for determining whether or not to accept a call connection request(s) that is/are classified as a subject(s) for acceptance determination.

A mobile communication system of the present invention comprises

a call processing control device that receives a call connection request(s) from a mobile terminal(s) and performs connection setup processing. The call processing control device comprises a call type determination means for determining a call type(s) of the call connection request(s) and, based on a determination result(s), classifying the call connection request(s) as either a subject(s) for acceptance determination or not a subject(s) for acceptance determination, and an acceptance determination means for determining whether or not to accept a call connection request(s) that is/are classified as a subject(s) for acceptance determination.

A method for restricting reception of a call connection request(s) of the present invention comprises steps of determining a call type(s) of a call connection request(s) from a mobile terminal(s), based on a result(s) of determining a call type(s), classifying the call connection request(s) as either a subject(s) for acceptance determination or not a subject(s) for acceptance determination, and determining whether or not to accept a call connection request(s) that is/are classified as a subject(s) for acceptance determination.

A program of the present invention causes a computer execute the above-described method for restricting reception of a call connection request(s).

Advantageous Effects of Invention

With the present invention, it is possible to provide a call processing control device, a mobile communication system, a method for restricting reception of call connection requests, and a program that are capable of suppressing congestion while suppressing influence on high-priority call connection requests.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a call processing control device, a mobile communication system, a method for restricting reception of call connection requests, and a program according to exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

First Exemplary Embodiment

With reference toFIG. 1, a configuration of a mobile communication system according to a first exemplary embodiment will be described. The mobile communication system is, for example, a mobile telephone network. The mobile communication system includes a call processing control device20and a plurality of terminals30. The terminals30are portable. The call processing control device20includes a call type determination unit21and an acceptance determination unit22. Each terminal30transmits a call connection request32to the call processing control device20. The call processing control device20transmits a connection setup message33or a connection rejection message34to each terminal30.

With reference toFIG. 2, a method for restricting reception of a call connection request(s) according to the first exemplary embodiment will be described. When the call processing control device20receives a call connection request32from a terminal30(step S100), the call type determination unit21determines a call type of the call connection request32(step S101) and classifies, based on the result of the determination, the call connection request32as either a subject for acceptance determination or not a subject for acceptance determination (step S102). In the case of a subject for acceptance determination, the process proceeds to step S103. In the case of not a subject for acceptance determination, the process proceeds to step S106.

The acceptance determination unit22determines whether or not to accept the call connection request32that has been classified as a subject for acceptance determination (step S103). In the case of determining to accept the call connection request32(acceptable in step S104), the process proceeds to step S106. In the case of determining not to accept the call connection request32(unacceptable in step S104), the process proceeds to step S105. In step S105, the call processing control device20performs connection rejection processing for the call connection request32. In the connection rejection processing, the call processing control device20transmits a connection rejection message34to the terminal30. After step S105, the process returns to step S100. In step S106, the call processing control device20performs connection setup processing for the call connection request32. In the connection setup processing, the call processing control device20transmits a connection setup message33to the terminal30. After step S106, the process returns to step S100.

According to the exemplary embodiment, the call type(s) of a call connection request(s)32is/are determined, and, based on the result(s) of the determination of the call type(s), the call connection request(s)32is/are classified as a subject(s) for acceptance determination or not a subject(s) for acceptance determination. Accordingly, it is possible that, for a call connection request(s)32that is/are determined to have a high-priority call type, connection setup processing is performed, and, for a call connection request(s)32that is/are determined to have a low-priority call type, whether to perform connection setup processing or connection rejection processing is determined through acceptance determination. In consequence, it is possible to suppress congestion in a mobile communication system while suppressing influence on a high-priority call connection requests(s)32.

Second Exemplary Embodiment

Next, a mobile communication system according to a second exemplary embodiment will be described. The mobile communication system according to the second exemplary embodiment is a mobile communication system based on LTE (Long Term Evolution). The mobile communication system according to the second exemplary embodiment attempts to raise the utilization rate by carrying out promotion in which a favorable term in terms of price is presented to users when the utilization rate of the network is low.

With reference toFIG. 3, a configuration of the mobile communication system according to the second exemplary embodiment will be described. The mobile communication system according to the second exemplary embodiment includes a plurality of terminals3, each of which is a portable radio device that users use and is referred to as a UE (User Equipment) in LTE, radio base stations2, each of which performs radio communication with terminals3and is referred to as an eNB (Enhanced NodeB) in LTE, and a core network1, which is a higher-level network of the terminals and the radio base stations and is referred to as an MME (Mobility Management Entity) and an SGW (Serving Gateway). Also, interfaces between these nodes include an RRC (Radio Resource Control) interface13based on a radio connection, an X2 interface12between radio base stations2, and an S1 interface11between a radio base station2and the core network1.

The core network1is configured with an MME, which performs network control, and an SGW, which deals with user data, and performs service control, charging control, and connection to the Internet and telephone networks. The core network1is also referred to as a core network device sometimes.FIG. 4is a diagram illustrating a configuration of the core network1inFIG. 3. A resource utilization rate determination unit103of the core network1measures the number of users who are connected to the MME or SGW itself or the amount of user data in processing and compares a resource utilization rate, which is obtained by comparing the measured value with an allowable value of the core network1itself, with a predetermined value. When the resource utilization rate is lower than the predetermined value, a control unit101of the core network1determines that the core network1is in a state in which utilization is promotable.

In this case, the control unit101transmits MME promotion start messages111to the radio base stations2that are connected through the S1 interfaces11, using a communication unit102. The MME promotion start message111is information that informs the radio base stations2under the core network1of the start of utilization promotion in which terminals are encouraged to perform communication.

The radio base station2is a device that performs radio communication with terminals3and has a role to relay user data between the terminals3and the core network1under the control of the core network1, which is at the higher level.FIG. 5is a diagram illustrating a configuration of the radio base station2inFIG. 3. By receiving an MME promotion start message111from the core network1by using a communication unit202, the radio base station2determines that the core network1to which the radio base station2is connected is in the utilization promotion state.

Also, a resource utilization rate determination unit203of the radio base station2compares a resource utilization rate, which is obtained by measuring the number of users connected to the radio base station2, the amount of data in processing, or the amount of information on a transmission path of radio resources, an S1 interface, and an X2 interface and comparing the measured value with an allowable value of the radio base station2itself, with a predetermined value. When the resource utilization rate is lower than the predetermined value, a control unit201of the radio base station2determines that the radio base station is in a state in which utilization is promotable.

In this case, the control unit201transmits an eNB promotion message(s)131to a terminal(s)3that reside(s) in the radio coverage of the radio base station2itself through the RRC interface13by using a radio communication unit205. The eNB promotion message131is information that informs the terminal(s)3under the radio base station2of utilization promotion in which the terminal(s)3is/are encouraged to perform communication. The eNB promotion message131may be regularly notified to the terminal(s)3under the radio base station2simultaneously by using system information.

The radio base station2corresponds to the call processing control device20according to the first exemplary embodiment. The radio base station2includes a timer206, a call type determination unit207, an acceptance determination unit208, and a random number generation unit209. The call type determination unit207and the acceptance determination unit208correspond to the call type determination unit21and the acceptance determination unit22according to the first exemplary embodiment, respectively.

The terminal3is a radio device with which users transmit and receive voice calls and data.FIG. 6is a diagram illustrating a configuration of the terminal3inFIG. 3. Through receiving an eNB promotion message131from a radio base station2by using a radio communication unit302, the terminal3determines that the core network1and the radio base station2are in the utilization promotion state. Then, a control unit301of the terminal3displays a message encouraging a user to perform communication using his/her own terminal on a display unit303and starts communication as a promotion call in response to an operation by the user who has seen the displayed message. Alternatively, the control unit301starts transmission and reception of data as a promotion call automatically instead of by manual calling by the user. The automatic calling is performed by the control unit301in accordance with the result of determination performed by an automatic calling determination unit304of the terminal3.

In the S1 interface11between each radio base station2and the core network1, the MME promotion start message111, which flows from the core network1toward the radio base station2, is incorporated. The MME promotion start message111is a message notifying that the MME is in the utilization promotion state, and may include a core network identification ID, a message validity period, the QOS (Quality Of Service) type and data amount of a call to which utilization promotion is applicable, an MME promotion code (core network determination information), which is a unique value used to determine whether or not to accept a promotion call, or the like. In the S1 interface11, an MME promotion stop message112, which flows from the core network1toward each radio base station2, is also incorporated. The MME promotion stop message112notifies that the MME has transited into a non-utilization promotion state.

In the RRC interface13, the eNB promotion message131, which flows from each radio base station2toward terminals3, is incorporated. The eNB promotion message131is a message that is transmitted regularly when each eNB is in the utilization promotion state. The eNB promotion message131may include an eNB cell identification ID, a message validity period, the QOS type and data amount of a call to which utilization promotion is applicable, an eNB promotion code (radio base station determination information), which is a unique value used to determine whether or not to accept a promotion call, the MME promotion code received from the core network1, or the like.

Further, through the RRC interface13, each terminal3transmits an RRC connection request message132to a radio base station2, and the radio base station2transmits an RRC connection setup message133or an RRC connection rejection message134to the terminal3. The terminals3correspond to the terminals30according to the first exemplary embodiment. The RRC connection request message132, RRC connection setup message133, and RRC connection rejection message134correspond to the call connection request32, connection setup message33, and connection rejection message34according to the first exemplary embodiment, respectively.

FIG. 7is a sequence diagram illustrating an operation example in the mobile communication system illustrated inFIG. 3. InFIG. 7, when the core network1transits into an MME utilization promotion state (step S1), the core network1transmits, on the S1 interface, MME promotion start messages111to the radio base stations2(step S2). Each radio base station2that has received the MME promotion start message111, by transiting into the eNB utilization promotion state (step S3), regularly transmits, on the RRC interface, eNB promotion messages131to terminals3(step S4).

Each terminal3that has received the eNB promotion message131, through a process of making a promotion call (step S5), transmits, on the RRC interface, an RRC connection request message132to the radio base station2(step S6). At this time, the terminal3transmits, to the radio base station2, the eNB promotion code and the MME promotion code received through the eNB promotion message131. The radio base station2that has received the eNB promotion code and the MME promotion code from the terminal3compares the codes with the eNB promotion code and the MME promotion code that the station itself has transmitted to the terminal3through the eNB promotion message131in step S4to determine the call type of the RRC connection request message132(step S7).

When both codes coincide with each other, the radio base station2determines that the RRC connection request message132is a promotion call, and further performs acceptance determination to determine whether or not to accept a connection from the terminal3(step S7). When the radio base station2determines to accept a connection from the terminal3in the acceptance determination, or, the call type resulted from the determination is different from promotion call, the radio base station2performs connection setup processing in step S8. In the connection setup processing, the radio base station2makes a call connection request to the core network1, and transmits an RRC connection setup message133to the terminal3. When the RRC connection request message132is determined as a promotion call, the radio base station2makes a call connection request by including the call connection request together with the MME promotion code received from the terminal3into an Initial UE message or a NAS message on the S1 interface. The core network1that receives the call connection request including the MME promotion code compares the code with the MME promotion code included in the MME promotion start message111transmitted in step S2. When both codes coincide with each other, the core network1determines that the call connection request including the MME promotion code is a promotion call. In charging processing, the core network1applies a special price, such as discount charge and flat-rate charge, to communication based on the call connection request determined to be a promotion call.

When, in the acceptance determination in step S7, it is determined that a connection from the terminal3is not accepted, the radio base station2performs connection rejection processing in step S8. In the connection rejection processing, the radio base station2transmits an RRC connection rejection message134to the terminal3.

Next, an operation of the core network1inFIG. 3will be described with reference toFIGS. 8 to 10.FIG. 8is a state transition diagram of the core network1inFIG. 3. As illustrated inFIG. 8, the core network1has two states: an MME utilization promotion state S15, and an MME non-utilization promotion state S16. The core network1that is in the MME utilization promotion state S15transmits, on the S1 interface, the MME promotion start messages111to the radio base stations2, and, in receiving a call connection request of a promotion call from a radio base station2, confirms correspondence between the MME promotion codes and performs promotion call reception. The core network1that is in the MME non-utilization promotion state S16transmits the MME promotion stop messages112on the S1 interface, rejects a call connection request(s) of a promotion call(s) from the radio base stations2, and cut a promotion call(s) that has/have been connected.

FIG. 9is a determination flowchart for a transition of the core network1inFIG. 3to the MME utilization promotion state S15. When the core network1that is in the MME non-utilization promotion state S16determines that the resource utilization rate of the core network1is lower than a threshold value a (step S17), the core network1performs a state transition to the MME utilization promotion state S15. As used herein, the resource utilization rate is either one of the ratios of a hardware processing load on the MME or SGW, an amount of information on inter-hardware interfaces, the number of connected users, an amount of data, and the like to corresponding allowable amounts.

FIG. 10is a determination flowchart for a transition of the core network1inFIG. 3to the MME non-utilization promotion state S16. When the core network1that is in the MME utilization promotion state S15determines that the resource utilization rate of the core network1is higher than a threshold value b (step S18), the core network1performs a state transition to the MME non-utilization promotion state S16. As used herein, the resource utilization rate is either one of the ratios of a hardware processing load on the MME or SGW, an amount of information on inter-hardware interfaces, the number of connected users, an amount of data, and the like to corresponding allowable amounts.

Next, an operation of the radio base station2inFIG. 3will be described with reference toFIGS. 11 to 13.FIG. 11is a state transition diagram of the radio base station2inFIG. 3. As illustrated inFIG. 11, the radio base station2has two states: an eNB utilization promotion state S21, and an eNB non-utilization promotion state S22. The radio base station2that is in the eNB utilization promotion state S21regularly transmits, on the RRC interface, the eNB promotion messages131to terminals3, and is able to accept an RRC connection request(s)132of a promotion call(s) from a terminal(s)3. The radio base station2that is in the eNB non-utilization promotion state S22stops transmitting the eNB promotion messages131on the RRC interface, rejects an RRC connection request(s)132of a promotion call(s) from the terminal(s)3, and cut a promotion call(s) that has/have been connected.

FIG. 12is a determination flowchart for a transition of the radio base station2inFIG. 3to the eNB utilization promotion state S21. When the radio base station2that is in the eNB non-utilization promotion state S22receives an MME promotion start message111from the core network1(step S23), the process proceeds to step S24. In step S24, when the radio base station2determines that the resource utilization rate of the radio base station2is lower than a threshold value c, the radio base station2performs a state transition to the eNB utilization promotion state S21. As used herein, the resource utilization rate is either one of the ratios of a hardware processing load on the radio base station2, an amount of information on the S1 or X2 interface, radio transmission and reception power, the number of connected users, and an amount of data to corresponding allowable amounts.

FIG. 13is a determination flowchart for a transition of the radio base station2inFIG. 3to the eNB non-utilization promotion state S22. When the radio base station2that is in the eNB utilization promotion state S21receives an MME promotion stop message112from the core network1(step S25), the radio base station2performs a state transition to the eNB non-utilization promotion state S22. Also, when the radio base station2determines that the resource utilization rate of the radio base station2is higher than a threshold value d even if the radio base station2has not received an MME promotion stop message112in step S25(step S26), the radio base station2performs a state transition to the eNB non-utilization promotion state S22. As used herein, the resource utilization rate is either one of the ratios of a hardware processing load on the radio base station2, an amount of information on the S1 or X2 interface, radio transmission and reception power, the number of connected users, and an amount of data to corresponding allowable amounts.

Next, an operation of the terminal3inFIG. 3will be described with reference toFIGS. 14 to 16.FIG. 14is a determination flowchart for a transition of the terminal3inFIG. 3to a terminal utilization promotion state or a terminal non-utilization promotion state. As illustrated inFIG. 14, the terminal3has two states: a terminal utilization promotion state S31, and a terminal non-utilization promotion state S32. When the terminal3that is in either of the states confirms periodical reception of eNB promotion messages131on the RRC interface from the radio base station2(step S33), the terminal3transits into the terminal utilization promotion state S31.

Also, even if the terminal3does not receive an eNB promotion message131, when it is determined that the current time is within a validity period indicated in the last eNB promotion message131received from the radio base station2(step S34), the terminal3continues the terminal utilization promotion state S31, and, when it is determined that the current time is out of the validity period (step S34), the terminal3transits into the terminal non-utilization promotion state S32. The terminal3that is in the terminal non-utilization promotion state S32is unable to make a promotion call.

FIG. 15is a flowchart in which a user makes a promotion call by using the terminal3inFIG. 3, which is in the terminal utilization promotion state S31. The terminal3that has transited into the terminal utilization promotion state S31(step S41) displays a message to promote usage (encouraging communication using the terminal3) on the display unit303(step S42). For example, the displayed message is a message proposing a call condition that is advantageous for the user in terms of price or the like, such as “a discount of 20% off the call charge is currently applied” and “a flat-rate charge is currently applied until midnight”. Displayed content may be created using information included in the eNB promotion message131notified by the radio base station2.

When the user who has seen the displayed message carries out a transmission of voice or data communication (step S43), the terminal3transmits an RRC connection request132including the eNB promotion code and the MME promotion code to the radio base station2(step S44). Subsequently, when connection setup processing is performed (step S8), communication of the promotion call is started.

FIG. 16is a flowchart in which the terminal3inFIG. 3that has transited into the terminal utilization promotion state S31automatically makes a promotion call. The terminal3that is in the terminal non-utilization promotion state S32holds data to be transmitted in a not-illustrated memory and also holds a list of candidate data to be received in the memory (step S51). When the terminal3transits into the terminal utilization promotion state S31(step S52), the terminal3performs automatic calling determination of promotion call (step S53). Conditions in the determination are, based on conditions that have been transmitted from the radio base station2through an eNB promotion message131(a message validity period and an allowable QOS type and amount of data of a call), defined as whether or not data planned to be transmitted and received can be transmitted and received within the message validity period, whether or not transmission and reception of the data planned to be transmitted and received can be performed satisfying the specified QOS, whether or not the amount of data planned to be transmitted and received is within the specified limit, or the like.

When data satisfying the conditions exist in the automatic calling determination of promotion call, the terminal3, to perform transmission to a predetermined transmission destination of the data or to perform reception from a predetermined reception source of the data, transmits an RRC connection request132including the eNB promotion code and the MME promotion code to the radio base station2(step S54). Subsequently, when the connection setup processing is performed (step S8), communication of the promotion call is started.

InFIG. 16, it is conceivable that data that do not need to be transmitted immediately (to be notified at once in real time) as data to be transmitted are transmitted when the terminal3transits into the terminal utilization promotion state S31. Examples of such data include: daily sales information collected by a vending machine including a terminal3; electricity/gas usage information collected by various types of meter including a terminal3; geographic information collected by a vehicle including a terminal3; weather and environmental information collected by a sensor including a terminal3; information on the radio wave environment, positions, and the terminal usage state by the user (traffic volume, service call type, communication quality, communication time, or the like) collected by a terminal3; and emails, game scores/results, pictures, videos, music, documents, software, personal information, bulletin board messages, database, or the like reserved by the user of a terminal3for transmission.

InFIG. 16, it is also conceivable that data that do not need to be received immediately (to be known at once in real time) as candidate data to be received are listed in advance and received when the terminal3transits into the terminal utilization promotion state S31. After the terminal3receives such data, the user can use the data in an off-line manner. Examples of such data include: information on update software, middleware, database, or the like that is applied to a terminal3itself or a computer, a vending machine, machinery, or the like including the terminal3; and emails, game software, pictures, videos, music, documents, books, software, news, bulletin board messages, TV schedules, weather information, map information, product price information, database, RSS feed information (used in news sites, blogs, or podcast distribution), or the like reserved by the user of a terminal3for reception.

Next, an operation of the radio base station2inFIG. 3will be described with reference toFIGS. 17 and 18.FIG. 17is a state transition diagram of the radio base station2inFIG. 3. As illustrated inFIG. 17, the radio base station2has two states: a call-type-based acceptance determination non-execution state S61, and a call-type-based acceptance determination execution state S62. When the transmission of the eNB promotion messages131is started, the radio base station2transits from the call-type-based acceptance determination non-execution state S61to the call-type-based acceptance determination execution state S62. At this time, the timer206starts counting. When the timer206has counted a predetermined time X (sec.), the radio base station2transits from the call-type-based acceptance determination execution state S62to the call-type-based acceptance determination non-execution state S61.

When the radio base station2is in the call-type-based acceptance determination non-execution state S61, the call type determination unit207does not perform processing of determining the call type of an RRC connection request132and, based on the result of the call type determination, classifying the RRC connection request132as either a subject for acceptance determination or not a subject for acceptance determination. The acceptance determination unit208does not perform processing of determining whether or not to accept an RRC connection request132that is classified as a subject for acceptance determination.

When the radio base station2is in the call-type-based acceptance determination execution state S62, the call type determination unit207performs processing of determining the call type of an RRC connection request132and, based on the result of the call type determination, classifying the RRC connection request132as either a subject for acceptance determination or not a subject for acceptance determination. The acceptance determination unit208performs processing of determining whether or not to accept an RRC connection request132that is classified as a subject for acceptance determination.

FIG. 18is a flowchart illustrating a method for restricting reception of a call connection request(s) that the radio base station2that is in the call-type-based acceptance determination execution state S62performs. Steps S71to S74correspond to step S7inFIG. 7. Steps S75to S77correspond to step S8inFIG. 7. When the radio base station2receives an RRC connection request132from a terminal3(step S71), the call type determination unit207determines whether or not the RRC connection request132is a promotion call (step S72), classifies the RRC connection request132that is determined as a promotion call as a subject for acceptance determination (YES in step S72), and classifies RRC connection request132that is not determined as a promotion call as not a subject for acceptance determination (NO in step S72).

When the radio base station2has received an MME promotion start message111, the call type determination unit207determines, as a promotion call, an RRC connection request132transmitted by a terminal3that has received an eNB promotion message131transiting into the terminal utilization promotion state. The MME promotion start message111above is a message that is transmitted from the core network1that has transited into the MME utilization promotion state when the resource utilization rate of the core network1is lower than a predetermined threshold value and used to encourage the terminals3to perform communication. The eNB promotion message131above is a message that is transmitted from a radio base station2that has transited into the eNB utilization promotion state when the resource utilization rate of the radio base station2is lower than a predetermined threshold value and used to encourage terminals3to perform communication.

At this time, the call type determination unit207determines whether or not the RRC connection request132is a promotion call based on the MME promotion code (core network determination information) and the eNB promotion code (radio base station determination information) both of which are included in the RRC connection request132. The call type determination unit207may perform the determination based on only the eNB promotion code (radio base station determination information).

When the RRC connection request132is determined to be a promotion call (YES in step S72), the random number generation unit209generates a random number Y (any number from 1 to 100) (step S73). The acceptance determination unit208determines whether or not the random number Y is larger than a predetermined value N (step S74). When the random number Y is larger than the value N (YES in step S74), the acceptance determination unit208determines not to accept the RRC connection request132, and the radio base station2performs connection rejection processing (step S75). In the connection rejection processing, the control unit201makes the radio communication unit205transmit the RRC connection rejection message134.

When the random number Y is not larger than the value N (NO in step S74), the acceptance determination unit208determines to accept the RRC connection request132, and the radio base station2performs connection setup processing (step S76). In the connection setup processing, the control unit201makes the communication unit202transmit a call connection request to the core network1and the radio communication unit205transmit the RRC connection setup message133. The call connection request above includes the MME promotion code (core network determination information) included in the RRC connection request132.

When the RRC connection request132is not determined to be a promotion call (NO in step S72), the radio base station2performs the connection setup processing (step S77). In the connection setup processing, the control unit201makes the communication unit202transmit a call connection request to the core network1and the radio communication unit205transmit the RRC connection setup message133.

According to the exemplary embodiment, since an RRC connection request132that is determined to be a promotion call is supposed to have a low priority, the RRC connection request132is determined to be accepted and becomes a subject for connection setup processing with a predetermined probability (N %), which is higher than 0% and lower than 100%. On the other hand, an RRC connection request132that is not determined to be a promotion call becomes a subject for the connection setup processing with a probability of 100%.

Furthermore, according to the exemplary embodiment, when the transmission of eNB promotion messages131is started, the call type determination unit207starts processing of determining the call type(s) of an RRC connection request(s)132and, based on the result(s) of the determination, classifying the RRC connection request(s)132as either a subject(s) for acceptance determination or not a subject(s) for acceptance determination, and the acceptance determination unit208starts processing of determining whether or not to accept an RRC connection request(s)132that is/are classified as a subject(s) for acceptance determination. When a predetermined time X has passed since the start of the transmission of eNB promotion messages131, the call type determination unit207stops the processing of determining the call type(s) of an RRC connection request(s)132and, based on the result(s) of the determination, classifying the RRC connection request(s)132as either a subject(s) for acceptance determination or not a subject(s) for acceptance determination, and the acceptance determination unit208stops the processing of determining whether or not to accept an RRC connection request(s)132that is/are classified as a subject(s) for acceptance determination.

Accordingly, with the exemplary embodiment, the acceptance of promotion calls is restricted during only a certain period (a period of X seconds) since the start of the transmission of eNB promotion messages131. Since the acceptance of promotion calls is restricted during only a period for which there is a high probability that a lot of promotion calls take place simultaneously, the acceptance of promotion calls being unnecessarily restricted is prevented.

The values N and X may be set to the radio base stations2in advance, or notified from the core network1to the radio base stations2.

Third Exemplary Embodiment

Next, a mobile communication system according to a third exemplary embodiment will be described. In the mobile communication system according to the third exemplary embodiment, the following points are changed from the mobile communication system according to the second exemplary embodiment. In the following description, descriptions of features that are common with the second exemplary embodiment and features that are obvious from the second exemplary embodiment will be omitted.

With reference toFIG. 19, a configuration of a radio base station2according to the third exemplary embodiment will be described. The radio base station2according to the third exemplary embodiment, as with the radio base station2according to the second exemplary embodiment, includes a control unit201, a communication unit202, a resource utilization rate determination unit203, a radio communication unit205, a timer206, a call type determination unit207, and an acceptance determination unit208. The radio base station2according to the third exemplary embodiment further includes a repetition number counter210and a cumulative call connection request number counter211.

Next, an operation of the radio base station2according to the third exemplary embodiment will be described with reference toFIGS. 20 and 21.FIG. 20is a state transition diagram of the radio base station2. As illustrated inFIG. 20, the radio base station2has two states: a call-type-based acceptance determination non-execution state S61, and a call-type-based acceptance determination execution state S62. When the transmission of eNB promotion messages131is started, the radio base station2transits from the call-type-based acceptance determination non-execution state S61to the call-type-based acceptance determination execution state S62. At this time, the timer206starts counting from an initial value, and the repetition number counter210is reset to 0.

When the timer206has counted a predetermined time A (sec.) and the value of the repetition number counter210is less than a predetermined number of repetitions M, the radio base station2transit is from the call-type-based acceptance determination execution state S62to the call-type-based acceptance determination execution state S62. At this time, the timer206starts counting from the initial value, and the repetition number counter210is incremented. When the timer206has counted the predetermined time A and the value of the repetition number counter210is equal to the predetermined number of repetitions M, the radio base station2transits from the call-type-based acceptance determination execution state S62to the call-type-based acceptance determination non-execution state S61.

FIG. 21is a flowchart illustrating a method for restricting reception of a call connection request(s) that the radio base station2that is in the call-type-based acceptance determination execution state S62performs. Steps S81to S85correspond to step S7inFIG. 7. Steps S86to S88correspond to step S8inFIG. 7. When the radio base station2transits into the call-type-based acceptance determination execution state S62, the cumulative call connection request number counter211is reset to 0 (step S81). When the radio base station2receives an RRC connection request132from a terminal3(step S82), the call type determination unit207determines whether or not the RRC connection request132is a promotion call (step S83), classifies the RRC connection request132that is determined as a promotion call as a subject for acceptance determination (YES in step S83), and classifies the RRC connection request132that is not determined as a promotion call as not a subject for acceptance determination (NO in step S83). Step S83is the same as step S72.

When the RRC connection request132is determined to be a promotion call (YES in step S83), the cumulative call connection request number counter211is incremented (step S84). The acceptance determination unit208determines whether or not the value of the cumulative call connection request number counter211is greater than a prescribed value B (step S85). The prescribed value B is a natural number. When the value of the cumulative call connection request number counter211is greater than the prescribed value B (YES in step S85), the acceptance determination unit208determines not to accept the RRC connection request132, and the radio base station2performs connection rejection processing (step S86). The connection rejection processing in step S86is the same as the connection rejection processing in step S75.

When the value of the cumulative call connection request number counter211is not greater than the prescribed value B (NO in step S85), the acceptance determination unit208determines to accept the RRC connection request132, and the radio base station2performs connection setup processing (step S87). The connection setup processing in step S87is the same as the connection setup processing in step S76. When the RRC connection request132is not determined to be a promotion call (NO in step S83), the radio base station2performs the connection setup processing (step S88). The connection setup processing in step S88is the same as the connection setup processing in step S77.

FIG. 22is a conceptual diagram illustrating the method for restricting reception of a call connection request(s) according to the third exemplary embodiment. The horizontal axis represents elapsed time since the point when the transmission of eNB promotion messages131was started. The vertical axis represents the cumulative number of RRC connection requests132that have been determined to be promotion calls, that is, the value of the cumulative call connection request number counter211.

According to the exemplary embodiment, the acceptance determination unit208repeats, M times, processing of accepting a predetermined number B of RRC connection requests132among the RRC connection requests132that are classified as subjects for acceptance determination in arrival order and not accepting a subsequent RRC connection request(s)132during a period of A second(s). Thus, with the exemplary embodiment, the reception of promotion calls is restricted during only a certain period (a period of M×A second(s)) since the start of the transmission of eNB promotion messages131.

The values A, B, and M may be set to the radio base stations2in advance or notified from the core network1to the radio base stations2.

Fourth Exemplary Embodiment

Next, a mobile communication system according to a fourth exemplary embodiment will be described. The mobile communication system according to the fourth exemplary embodiment is a mobile communication system on which functions of the mobile communication system according to the second or third exemplary embodiment are achieved using a mobile communication system based on WCDMA (Wideband Code Division Multiple Access) (Registered Trademark). In the following description, descriptions of features that are common with the second and third exemplary embodiments and features that are obvious from the second and third exemplary embodiments will be omitted.

With reference toFIG. 23, the mobile communication system according to the fourth exemplary embodiment will be described. The mobile communication system according to the fourth exemplary embodiment include a plurality of terminals503, each of which is a portable radio device that a user uses and is referred to as a UE (User Equipment) in WCDMA, radio base stations502B, each of which performs radio communication with terminals503and is referred to as a NodeB in WCDMA, radio network control stations502A, each of which controls a radio base station502B, and a core network501, which is a higher-level network of these components. There is a case in which the radio network control station502A is referred to as an RNC. Also, these nodes are interconnected through interfaces. The terminal503, the radio network control station502A, and the core network501correspond to the terminal3, the radio base station2, and the core network1, respectively.

The core network501transmits promotion start messages611and promotion stop messages612to the radio network control stations502A. The promotion start message611and the promotion stop message612correspond to the MME promotion start message111and the MME promotion stop message112, respectively.

Each radio network control station502A transmits promotion messages631, connection setup messages633, and connection rejection messages634to terminals503via a radio base station502B. Each terminal503transmits a connection request message632to a radio network control station502A via a radio base station502B. The promotion message631, the connection request message632, the connection setup message633, and the connection rejection message634correspond to the eNB promotion message131, the RRC connection request message132, the RRC connection setup message133, and the RRC connection rejection message134, respectively.

When the resource utilization rate of the core network501is lower than a predetermined threshold value, the core network501transits into a core network utilization promotion state and transmits promotion start messages611for encouraging the terminals503to perform communication to the radio network control stations502A, including core network determination information into the promotion start messages611.

When each radio network control station502A receives a promotion start message611and the resource utilization rate of the radio base station502B under the radio network control station502A is lower than a predetermined threshold value at the time, the radio network control station502A transits into a radio base station utilization promotion state. The radio network control station502A that has transited into the radio base station utilization promotion state transmits promotion messages631for encouraging terminals503to perform communication to the terminals503via the radio base station502B, including the core network determination information and radio base station determination information into the promotion messages631.

When each terminal503receives a promotion message631, the terminal503transits into a terminal utilization promotion state and transmits a connection request message632to a radio network control station502A via a radio base station502B, including the core network determination information and the radio base station determination information into the connection request message632.

The radio network control station502A, based on the core network determination information and the radio base station determination information, both of which are included in the connection request message632, determines the connection request message632to be a promotion call, and classifies the connection request message632as a subject for acceptance determination. When the radio network control station502A determines to accept the connection request message632, the radio network control station502A transmits a connection setup message633to the terminal503via the radio base station502B. When the radio network control station502A determines not to accept the connection request message632, the radio network control station502A transmits a connection rejection message634to the terminal503via the radio base station502B.

It should be noted that the present invention is not limited to the above exemplary embodiments and can be changed appropriately without departing from the spirit and scope of the present invention. For example, both a promotion call(s) and a usual call(s) may be classified as a subject(s) for acceptance determination. Alternatively, an emergency call(s) may be classified as not a subject(s) for acceptance determination, and (an)other type(s) of call(s) may be classified as a subject(s) for acceptance determination. Furthermore, the method for restricting reception of a call connection request(s) may be achieved by a computer executing a program.

In the above-described examples, programs can be stored by using various types of non-transitory computer readable media and supplied to computers. The non-transitory computer readable media include various types of tangible storage media. Examples of the non-transitory computer readable media include a magnetic recording medium (for example, a flexible disk, a magnetic tape, and a hard disk drive), a magneto optical recording medium (for example, a magneto optical disk), a CD-ROM (Read Only Memory), a CD-R (Compact Disk-Recordable), a CD-R/W (Compact Disk-ReWritable), and a semiconductor memory (for example, a mask ROM, a PROM (Programmable ROM), an EPROM (Erasable PROM), a flash ROM, a RAM (Random Access Memory)). The programs may be supplied to the computers through various types of transitory computer readable media. Examples of the transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The transitory computer readable media are capable of supplying the programs to the computers via a wired communication path, such as electric wires, optical fibers, and the like, or a radio communication path.

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2013-173225, filed on Aug. 23, 2013, the disclosure of which is incorporated herein in its entirety by reference

REFERENCE SIGNS LIST

1Core network2Radio base station3Terminal20Call processing control device21Call type determination unit22Acceptance determination unit30Terminal32Call connection request111MME promotion start message131eNB promotion message132RRC connection request message207Call type determination unit208Acceptance determination unit501Core network502A Radio network control station502B Radio base station503Terminal611Promotion start message632Connection request message