JP2009206769A - System and method for controlling call - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure the quality of the communication of a network, without reserving a band. <P>SOLUTION: A system 2 for controlling a call establishes a normal call, on the basis of an INVITE message transmitted from a portable telephone M in an IP backbone network NB, relaying a normal packet on the basis of the priority of a transmission. The system for controlling the call includes a dummy packet transmitting-receiving section 11, establishing a dummy call between two gateway nodes 10 in the network NB and transmitting a dummy packet having a lower priority for transmission than the normal packet transmitted through the normal call established between the system and the portable telephone M through the dummy call. The system for controlling the call, further, includes a measuring section 12 measuring the quality of the communication of the dummy packet and call control sections 14 and 33, refusing the establishment of the call to a new call establishment demand signal, when the quality of the communication is less than a specified level and establishing the call to the new call establishment demand signal, when the quality of the communication is higher than the specified level. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a call control system and a call control method for realizing a quality assurance type network service.

  Conventionally, a method for establishing a call while guaranteeing communication quality of a network is known. For example, in an asynchronous transfer mode (ATM) -based circuit switching service, a call is made when a path (path) is set after checking free resources between adjacent nodes and a path between end points can be set. By establishing the communication quality is guaranteed. Further, in an IP (Internet Protocol) communication network, quality assurance type communication is realized by performing bandwidth reservation by an RSVP (Resource Reservation Protocol) method or a bandwidth broker method.

Patent Document 1 below describes a wireless packet transmission system that employs a bandwidth reservation technique. This wireless packet transmission system sets voice priority for data based on the ratio between the traffic volume and the number of free channels, and calculates a reserved channel capacity allocated to each of data and voice based on the set priority. . The wireless packet transmission system calculates a transmission permission probability based on the reserved channel capacity, and transmits a data packet or a voice packet according to the transmission permission probability.
Japanese Patent Laid-Open No. 11-17607

  However, the bandwidth reservation as described above requires a certain time. Therefore, the waiting time until the bandwidth reservation is completed becomes long, and as a result, transmission delay and fluctuation may occur.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a call control system and a call control method that can guarantee communication quality of a network without performing bandwidth reservation.

  In the call control system of the present invention, in a network that relays transmitted packets based on the transmission priority, a call is established between the calling terminal and the receiving terminal based on a call establishment request signal transmitted from the calling terminal. A call control system for establishing a dummy call between one relay device in a network and another relay device in the network, and via a call established between a calling terminal and a receiving terminal Dummy packet transmission means for transmitting a dummy packet having a lower transmission priority than the regular packet transmitted through the dummy call, and measurement means for measuring the communication quality of the dummy packet transmitted by the dummy packet transmission means If the communication quality measured by the measuring means is below a predetermined level, the call establishment is rejected for the new call establishment request signal, and the communication quality is If it is the level above is characterized in that it comprises a call control means for establishing a call to the new call establishment request signal.

  Further, the call control method of the present invention is a network that relays transmitted packets based on the transmission priority, between the calling terminal and the receiving terminal based on a call establishment request signal transmitted from the calling terminal. A call control method in a call control system for establishing a call, wherein a dummy call is established between one relay device in a network and another relay device in the network, and between a calling terminal and a receiving terminal A dummy packet transmission step of transmitting a dummy packet having a lower transmission priority than a regular packet transmitted through a call established through the dummy call, and the dummy packet transmitted in the dummy packet transmission step. A measurement step for measuring communication quality, and if the communication quality measured in the measurement step is less than a predetermined level, a new call establishment request message is received. And a call control step of establishing a call in response to a new call establishment request signal when the communication quality is higher than the predetermined level. .

  According to such a call control system and call control method, a dummy packet having a lower transmission priority than a regular packet is transmitted via a dummy call placed in the network, and the communication quality of the transmitted dummy packet is Is measured. When the measured communication quality satisfies a predetermined level, a call is established for a new call establishment request signal. In the network, the regular packet is transmitted with priority over the dummy packet, and as a result, the communication quality of the dummy packet deteriorates faster than that of the regular packet. By utilizing this fact and controlling call establishment based on the communication quality of the dummy packet, it becomes possible to establish a call only in an environment in which a certain communication quality is guaranteed without performing bandwidth reservation. . That is, it becomes possible to guarantee the communication quality of the network.

  Also, the call control system of the present invention provides a network between relaying packets to be transmitted based on the transmission priority between the transmitting terminal and the receiving terminal based on a call establishment request signal transmitted from the transmitting terminal. A call control system for establishing a call, comprising: a calling side gateway device connected to a calling side external network where a calling terminal is located; and a called side gateway device connected to a called side external network where a called terminal is located; The originating gateway device establishes a dummy call with the terminating gateway device, and the transmission priority is higher than the regular packet transmitted via the call established between the originating terminal and the terminating terminal. Dummy packet transmission means for transmitting a low dummy packet via the dummy call, and measurement of communication quality of the dummy packet transmitted by the dummy packet transmission means And the communication quality measured by the measurement means is less than a predetermined level, the call establishment is rejected for a new call establishment request signal transmitted from the calling terminal, and the communication quality is And a call control means for establishing a call in response to the new call establishment request signal when the level is equal to or higher than a predetermined level.

  According to such a call control system, a dummy packet having a transmission priority lower than that of a regular packet is transmitted and transmitted via a dummy call placed between the originating gateway device and the terminating gateway device. The communication quality of the dummy packet is measured at the originating gateway device. When the measured communication quality satisfies a predetermined level, a call is established for a new call establishment request signal. In the network, the regular packet is transmitted with priority over the dummy packet, and as a result, the communication quality of the dummy packet deteriorates faster than that of the regular packet. By utilizing this fact and controlling call establishment based on the communication quality of the dummy packet, it becomes possible to establish a call only in an environment in which a certain communication quality is guaranteed without performing bandwidth reservation. . That is, it becomes possible to guarantee the communication quality of the network. Also, in response to a call establishment request signal transmitted from the originating terminal and transmitted via the originating external network, the originating gateway device that first receives the signal determines whether or not call establishment is possible. Whether it is possible or not can be determined early.

  Also, the call control system of the present invention provides a network between relaying packets to be transmitted based on the transmission priority between the transmitting terminal and the receiving terminal based on a call establishment request signal transmitted from the transmitting terminal. A call control system for establishing a call, wherein a calling side gateway device connected to a calling side external network where a calling terminal is located, a called side gateway device connected to a called side external network where a called terminal is located, A call control device capable of communicating with the side gateway device, and the destination side gateway device establishes a dummy call with the originating side gateway device, via a call established between the originating terminal and the terminating terminal. Dummy packet transmission means for transmitting a dummy packet having a lower transmission priority than a regular packet transmitted via the dummy call, and dummy packet transmission means Measuring means for measuring the communication quality of the dummy packet transmitted from the terminal, and a notification indicating whether or not a call can be established via the destination gateway apparatus is transmitted to the call control apparatus based on the communication quality measured by the measuring means. A notification transmission means, wherein the call control device receives a notification transmitted from the notification transmission means, based on the notification received by the notification reception means, identification information of the destination gateway device, and The storage means for associating and storing the availability information indicating whether or not a call can be established via the destination gateway device and the availability information associated with the identification information cannot establish a call via the destination gateway device In response to the new call establishment request signal transmitted from the originating terminal to the terminating terminal, the establishment of the call is rejected, and the availability information indicates the destination gateway device. To indicate that you can establish a call to reason is provided with a call control means for establishing a call to the new call establishment request signal, characterized in that.

  According to such a call control system, a dummy packet having a transmission priority lower than that of a regular packet is transmitted and transmitted via a dummy call placed between the originating gateway device and the terminating gateway device. The communication quality of the dummy packet is measured at the destination gateway device. When the measured communication quality satisfies a predetermined level, a call is established via the destination gateway device in response to a new call establishment request signal. In the network, the regular packet is transmitted with priority over the dummy packet, and as a result, the communication quality of the dummy packet deteriorates faster than that of the regular packet. By utilizing this fact and controlling call establishment based on the communication quality of the dummy packet, it becomes possible to establish a call only in an environment in which a certain communication quality is guaranteed without performing bandwidth reservation. . That is, it becomes possible to guarantee the communication quality of the network.

  According to such a call control system and call control method, a new call is created based on the communication quality of a dummy packet having a lower transmission priority than a regular packet transmitted via a call established between communication terminals. Since it is determined whether or not to establish a call in response to the establishment request signal, the communication quality of the network can be guaranteed without making a bandwidth reservation.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant description is omitted.

  First, the overall configuration of the call control system 2 according to the embodiment will be described with reference to FIG. FIG. 1 is a diagram showing an overall configuration of a communication system 1 including a call control system 2.

  The communication system 1 includes a plurality of mobile phones (communication terminals) M, a plurality of access networks (external networks) NA, and an IP backbone network NB. The communication system 1 employs IMS (IP Multimedia Subsystem) as a communication method. In FIG. 1, only two mobile phones M and access networks NA are shown for simplicity of explanation, but the number of access networks NA and mobile phones M connected to the IP backbone network NB is not limited.

  The access network NA is a wireless network including base stations (not shown) and transmits / receives control signals and data signals to / from the mobile phone M.

  The IP backbone network NB is a wired network that connects the access networks NA, and the call control system 2 is mounted in this network. The IP backbone network NB realizes communication quality (QoS) guarantee by a DiffServ (Differentiated Services) system. The details of DiffServ are defined in RFC2474 and RFC2475.

  The call control system 2 is a system that performs call control according to SIP (Session Initiation Protocol), which is a protocol for performing session management in a network. The call control system 2 includes a plurality of gateway nodes 10, a plurality of routers 20, and a plurality of CSCFs (Call / Session Control Function) 30. In FIG. 1, only two gateway nodes 10 and CSCFs 30 are shown for simplicity of explanation, but the number of these is not limited. Further, the number of routers 20 is not limited. The gateway node 10 and the CSCF 30 have a many-to-many relationship. That is, one gateway node 10 may transmit / receive data to / from a plurality of CSCFs 30, and one CSCF 30 may transmit / receive data to / from a plurality of gateway nodes 10.

  The gateway node 10 is a communication device (relay device) that connects the IP backbone network NB and the access network NA and relays a packet from one network to the other network.

  When the gateway node 10 receives an IP packet (hereinafter simply referred to as “packet”) transmitted from the mobile phone M and transmitted via the access network NA, the gateway node 10 indicates the priority of transmission based on the type of the packet. DSCP (DiffServ Code Point) is determined. Subsequently, the gateway node 10 writes the determined DSCP in a DS (Differentiated Services) field in the packet. Then, the gateway node 10 transfers the packet to another communication device (router 20 or CSCF 30) in the IP backbone network NB based on the destination IP address written in the packet. Further, the gateway node 10 transfers a packet transmitted from another communication device in the IP backbone network NB to a communication device (not shown) in the access network NA.

  The router 20 is a communication device that relays packets transmitted in the IP backbone network NB. When the router 20 receives the packet, it reads out the DSCP from the DS field of the packet, and transmits the packet to another communication device (for example, another router 20 or gateway node 10) based on the read DSCP, that is, the transmission priority. Send to. For example, when the router 20 holds the packet A of DSCP “2” and the packet B of DSCP “1”, the router 20 transmits the packet A having a higher DSCP than the packet B first. Therefore, when the router 20 receives more packets than its own transfer capability, a transmission delay occurs for a packet with a low DSCP (priority), or a packet with a low DSCP is discarded by the router 20. Sometimes.

  As described above, in the IP backbone network NB, the transmitted packet is relayed based on the transmission priority by the cooperation of the gateway node 10 and the router 20.

  The CSCF 30 is also called a SIP server, and is a call control device that executes call session setting (control of incoming / outgoing calls), or accesses an application server (not shown) to activate a predetermined service. Actually, the CSCF 30 is divided into P-CSCF (Proxy-Call / Session Control Function), I-CSCF (Interrogating-Call / Session Control Function), and S-CSCF (Serving-Call / Session Control Function) for each function. In this specification, these are collectively expressed as CSCF30.

  Next, the functional configuration of the gateway node 10 shown in FIG. 1 will be described with reference to FIGS. FIG. 2 is a diagram illustrating a functional configuration of the gateway node 10, and FIG. 3 is a diagram illustrating a hardware configuration of the gateway node 10.

  The gateway node 10 includes a dummy packet transmission / reception unit 11, a measurement unit 12, a determination unit 13, and a call control unit 14 as functional components.

  As illustrated in FIG. 3, the gateway node 10 includes a CPU 101, a main storage unit 102 configured by a ROM and a RAM, an auxiliary storage unit 103 configured by a hard disk, and other communication devices such as a router 20 and a CSCF 30. A communication interface 104 for transmitting and receiving packets to and from the network, an input unit 105 configured with operation keys and the like, and an output unit 106 configured with a monitor, a light emitting diode (LED), and the like. Each function of the gateway node 10 illustrated in FIG. 2 reads predetermined computer software on the CPU 101 or the main storage unit 102, operates the communication interface 104, the input unit 105, and the output unit 106 under the control of the CPU 101. This is realized by reading or writing data to the main storage unit 102 or the auxiliary storage unit 103.

  The dummy packet transmitting / receiving unit 11 establishes a dummy call with another gateway node 10 in the IP backbone network NB, and via a call established between the mobile phones M (hereinafter also referred to as “regular call”). A means for transmitting and receiving a dummy packet having a lower DSCP than a transmitted packet (hereinafter also referred to as a “regular packet”) via the dummy call.

  Specifically, the dummy packet transmission / reception unit 11 establishes a dummy call with the dummy packet transmission / reception unit of the partner gateway. This dummy call is a call used exclusively for measuring the communication quality of the IP backbone network NB, and is always established between the gateway nodes 10.

  When the dummy call transmission / reception unit 11 establishes the dummy call, the dummy packet transmission / reception unit 11 generates a dummy packet to be transmitted to the partner gateway node 10 via the dummy call. Specifically, the dummy packet transmission / reception unit 11 indicates an address (transmission destination address) indicating the transmission destination gateway node 10, a time stamp (absolute time) assumed to be the transmission time, and the transmission source gateway node 10. A dummy packet including an address (source address), a sequence number continuously assigned to each packet, and a DSCP is generated. At this time, the dummy packet transmitting / receiving unit 11 sets a value lower than any DSCP assigned to the regular packet as the DSCP of the dummy packet.

  Subsequently, the dummy packet transmitting / receiving unit 11 transmits the generated dummy packet to the partner gateway via the dummy call. The dummy packet transmitting / receiving unit 11 repeatedly generates a predetermined amount of dummy packets and transmits the generated dummy packets at predetermined time intervals. It should be noted that how much dummy packet the dummy packet transmitting / receiving unit 11 transmits (how much of the bandwidth resource of the IP backbone network NB is reserved as the bandwidth used for the dummy call) can be arbitrarily determined. .

  Further, the dummy packet transmitting / receiving unit 11 receives a dummy packet transmitted from the dummy packet transmitting / receiving unit of the communication partner gateway and transmitted via the router 20.

  The measuring unit 12 is means for measuring the communication quality of the dummy packet transmitted by the dummy packet transmitting / receiving unit of the partner gateway and received by the dummy packet transmitting / receiving unit 11. The measuring unit 12 monitors the reception of the dummy packet by the dummy packet transmitting / receiving unit 11 and measures the reception time when the dummy packet transmitting / receiving unit 11 receives the dummy packet. Subsequently, the measurement unit 12 associates the transmission source address, the sequence number, and the transmission time written in the received dummy packet with the measured reception time, and records it as actual measurement data. The measuring unit 12 stores measured data for a predetermined time in response to the dummy packet transmitting / receiving unit 11 receiving a certain number of dummy packets within a certain time.

  Subsequently, the measurement unit 12 measures the communication quality of the dummy packet based on the accumulated actual measurement data. For example, the measurement unit 12 calculates the average transmission time of the dummy packet transmitted from the specific gateway node 10 based on the transmission time and the reception time written in the actual measurement data accumulated during the unit time. In addition, the measurement unit 12 calculates the packet loss rate of the dummy packet transmitted from the specific gateway node 10 by checking the continuity of the sequence numbers written in the actual measurement data accumulated during the unit time. . The index indicating the communication quality is not limited to the average transmission time and the packet loss rate. For example, the measurement unit 12 may calculate the fluctuation amount (variation in delay time). The measurement unit 12 outputs an index value such as the calculated average transmission time or packet loss rate to the determination unit 13 as a communication quality measurement result.

  The determination unit 13 is a unit that determines whether the communication quality of the dummy packet is equal to or higher than a predetermined level based on the measurement result input from the measurement unit 12. The determination unit 13 stores a threshold value used for this determination in advance. For example, the determination unit 13 transmits a dummy packet transmission time (ideal transmission time) T (seconds), a delay time threshold value D (seconds), and a packet loss rate threshold value R (under a condition in which no transmission delay occurs. %).

The determination method of the communication quality of the dummy packet by the determination unit 13 is not limited. For example, the determination unit 13 may determine the communication quality of the dummy packet based on the transmission delay of the dummy packet. In this case, the determination unit 13 determines that the difference between the average transmission time t _x (seconds) input from the measurement unit 12 and the ideal transmission time T stored in advance, that is, the average delay time (t _x −T) is the threshold value D. It is determined whether or not the above is true. At this time, if t _x −T ≧ D, it means that a transmission delay equal to or greater than the threshold has occurred, and therefore the determination unit 13 determines that the communication quality of the dummy packet is less than a predetermined level. On the other hand, if t _x -T <D, the determination unit 13 determines that the communication quality of the dummy packet is equal to or higher than a predetermined level, assuming that the degree of delay is slight.

  Here, if the communication quality of the dummy packet is equal to or higher than a predetermined level, even if a new regular call is newly established in the future, a problem such as congestion does not occur in the IP backbone network NB. This is a state in which it is guaranteed that there will be no problem in the telephone call or data transmission. On the other hand, if the communication quality of the dummy packet is less than a predetermined level, it is highly likely that problems such as congestion will occur in the IP backbone network NB when another regular call is newly established in the future. Say.

The determination unit 13 may determine the communication quality of the dummy packet based on the degree of the packet loss rate of the dummy packet. In this case, the determination unit 13 compares the packet loss rate r _x (%) input from the measurement unit 12 with a threshold value R stored in advance. At this time, if r _x ≧ R, it means that a packet loss equal to or greater than the threshold has occurred, and therefore the determination unit 13 determines that the communication quality of the dummy packet is less than a predetermined level. On the other hand, if r _x <R, the determination unit 13 determines that the communication quality of the dummy packet is equal to or higher than a predetermined level, assuming that the degree of packet loss is slight.

  Further, the determination unit 13 may determine the communication quality of the dummy packet using both the delay time and the packet loss rate. For example, the communication quality may be determined to be less than a predetermined level when both the delay time based on the measurement result and the packet loss rate are equal to or higher than a threshold value.

  The determination unit 13 determines whether or not the communication quality of the dummy packet has deteriorated or recovered by performing the above determination at a predetermined time interval, and outputs the determination result to the call control unit 14 and the CSCF 30.

  If the communication quality of the dummy packet exceeds the predetermined level for a certain period of time and then becomes lower than that level, the determination unit 13 determines that the communication quality of the dummy packet has deteriorated, generates a bandwidth congestion notification, and calls It outputs to the control part 14 and CSCF30. On the other hand, when the communication quality of the dummy packet is lower than the predetermined level for a certain period of time and then becomes higher than that level, the determination unit 13 determines that the communication quality of the dummy packet has recovered, and sends a recovery notification. Generate and output to the call control unit 14 and the CSCF 30.

  Here, the bandwidth congestion notification is a notification indicating that a new call cannot be established via its own device (gateway node 10). On the other hand, the recovery notification is a notification indicating that a new call can be established via the own device. The determination unit 13 generates and outputs these two types of notifications based on the measured communication quality of the dummy packet.

  When transmitting a bandwidth congestion notification or a recovery notification to the CSCF 30, the determination unit 13 uses the SIP OPTIONS method. Further, the determination unit 13 writes in advance an IP address for identifying the gateway node 10 in the notification transmitted to the CSCF 30. The number of gateway nodes 10 to which the determination unit 13 transmits the bandwidth congestion notification and the recovery notification is one or more.

  When the communication quality of the dummy packet is less than a predetermined level, the call control unit 14 rejects the call establishment in response to the new call establishment request signal, and when the communication quality is equal to or higher than the predetermined level. Is means for establishing a call in response to a new call establishment request signal.

  The call control unit 14 determines whether to execute call establishment based on the bandwidth congestion notification or the recovery notification input from the determination unit 13. When a bandwidth congestion notification is input, the call control unit 14 determines not to execute establishment of a new call. When a recovery notification is input, the call control unit 14 can newly establish a call. And decide. That is, from the time when the bandwidth congestion notification is input to the time when the recovery notification is input, the call control unit 14 is in a restricted state in which the call establishment is rejected, and after the recovery notification is input, the bandwidth congestion notification is input. In the meantime, the call control unit 14 is in a normal state in which call establishment can be executed.

  The call control unit 14 receives a SIP INVITE message (call establishment request signal) from the access network NA. The INVITE message is a signal including the address of the source mobile phone M and the address of the destination mobile phone M. When the call control unit 14 receives an INVITE message from the access network NA when the call control unit 14 is in a restricted state, the call control unit 14 generates a response message “580 precondition failure” indicating that the call cannot be established, and the calling mobile phone M is sent to M and the process is terminated. In contrast, when the INVITE message is received from the access network NA when the call control unit 14 is in the normal state, the call control unit 14 transfers the INVITE message to the CSCF 30 on the caller side.

  Further, the call control unit 14 may receive an INVITE message from the CSCF 30. In this case, the call control unit 14 transfers the INVITE message to the access network NA. This INVITE message is finally transmitted to the destination mobile phone M.

  Next, the functional configuration of the CSCF 30 shown in FIG. 1 will be described with reference to FIG. FIG. 4 is a diagram illustrating a functional configuration of the CSCF 30.

  The CSCF 30 includes a notification receiving unit 31, a gateway state storage unit 32, and a call control unit 33 as functional components. The hardware configuration of the CSCF 30 is the same as that of the gateway node 10 (see FIG. 3), and the gateway node 10 is also described in terms of how each function of the CSCF 30 shown in FIG. 4 is realized on the hardware. It is the same as that.

  The notification receiving unit 31 is means for receiving a bandwidth congestion notification or a recovery notification transmitted from the gateway node 10. The notification receiving unit 31 outputs the received bandwidth congestion notification or recovery notification to the gateway state storage unit 32.

  The gateway state storage unit 32 is a means for storing the identification information of the gateway node 10 and the availability information indicating whether or not a call passing through the gateway node 10 is established based on the bandwidth congestion notification or the recovery notification. .

  When a bandwidth congestion notification is input from the notification receiving unit 31, the gateway state storage unit 32 extracts the IP address (identification information) of the gateway node 10 that is the transmission source from the bandwidth congestion notification, and the extracted IP address, A flag “0” indicating that a call cannot be established via the gateway node 10 is stored and updated (associated). On the other hand, when a recovery notification is input from the notification receiving unit 31, the gateway state storage unit 32 extracts the IP address of the transmission source gateway node 10 from the recovery notification, the extracted IP address, A flag “1” indicating that a call can be established via the gateway node 10 is stored in association (updated).

  Therefore, the flag “0” is availability information indicating that the gateway node 10 is in a restricted state, and the flag “1” is availability information indicating that the gateway node 10 is in a normal state.

  When the communication quality of the dummy packet is less than a predetermined level, the call control unit 33 rejects the call establishment in response to a new call establishment request signal, and the communication quality is equal to or higher than the predetermined level. Is means for establishing a call in response to a new call establishment request signal.

  The call control unit 33 receives the INVITE message (call establishment request signal) transmitted from the mobile phone M that is the transmission source. Where the call control unit 33 receives the INVITE message depends on whether the CSCF 30 plays a role of a caller or a callee. When the CSCF 30 stands on the caller side, the call control unit 33 receives an INVITE message from the gateway node 10 connected to the access network NA on the caller side. On the other hand, when the CSCF 30 stands on the receiving side, the call control unit 33 receives an INVITE message from the CSCF 30 on the calling side.

  When the call control unit 33 receives an INVITE message from the gateway node 10 on the caller side, the call control unit 33 obtains subscriber information corresponding to the address of the destination mobile phone M included in the INVITE message. To do. This subscriber information may be stored in a database (not shown) in the CSCF 30 or may be stored in an external database (not shown) such as an HLR (Home Location Register) or HSS (Home Subscriber Server). There may be. The call control unit 33 specifies the CSCF 30 on the receiving side based on the acquired subscriber information, and transmits an INVITE message to the CSCF 30 on the receiving side.

  On the other hand, when the call control unit 33 receives an INVITE message from the CSCF 30 on the caller side, the call control unit 33 selects the subscriber corresponding to the address of the destination mobile phone M included in the INVITE message. Get information. Subsequently, the call control unit 33 specifies the IP address of the gateway node 10 as the transfer destination based on the acquired subscriber information. Subsequently, the call control unit 33 accesses the gateway state storage unit 32 and acquires a flag corresponding to the specified IP address.

  When the acquired flag is “0”, the call control unit 33 determines that the communication quality of the dummy packet is lower than a predetermined level in the transfer destination gateway node 10 and the gateway node 10 is in a restricted state. To do. Then, the call control unit 33 generates a response message “580 precondition failure” indicating that the call cannot be established, transmits the response message to the CSCF 30 on the transmission side, and ends the processing. The response message is finally transmitted to the mobile phone M that is the transmission source.

  On the other hand, when the acquired flag is “1”, the call control unit 33 indicates that the communication quality of the dummy packet is equal to or higher than a predetermined level in the gateway node 10 of the transfer destination, and the gateway node 10 Judged to be in a state. Then, the call control unit 33 transmits an INVITE message to the gateway node 10 that is the transfer destination. This INVITE message is finally transmitted to the destination mobile phone M.

  Next, processing of the call control system 2 shown in FIG. 1 will be described with reference to FIGS. 5 to 9 and a call control method according to the present embodiment will be described. FIG. 5 is a flowchart showing processing of the gateway node 10. FIG. 6 is a flowchart showing the processing of the CSCF 30. FIG. 7 is a sequence diagram showing a general flow until call establishment. FIG. 8 is a sequence diagram showing call control based on the state of the gateway node 10 on the called side. FIG. 9 is a sequence diagram showing call control based on the state of the gateway node 10 on the calling side.

  First, the processing of the gateway node 10 will be described with reference to FIG. In the gateway node 10, first, the dummy packet transmitting / receiving unit 11 establishes a dummy call with another gateway node 10, and transmits / receives a dummy packet having a lower DSCP (transmission priority) than the regular packet via the dummy call. (Step S11, dummy packet transmission step). Subsequently, the measuring unit 12 measures the communication quality of the dummy packet received by the dummy packet transmitting / receiving unit 11 (step S12, measuring step). For example, the measurement unit 12 performs measurement by calculating the average transmission time and packet loss rate of dummy packets.

  Subsequently, the determination unit 13 determines how the communication quality of the dummy packet has changed in relation to a predetermined level based on the measurement result (step S13). For example, when the delay time of the dummy packet is equal to or greater than a predetermined threshold, the determination unit 13 determines that the communication quality of the dummy packet is less than a predetermined level (deteriorated), and the delay time is the predetermined threshold. If it is less than the threshold, it is determined that the communication quality of the dummy packet has become a predetermined level or higher (recovered).

  When the communication quality of the dummy packet becomes lower than a predetermined level (step S13; deterioration), the determination unit 13 generates a bandwidth congestion notification and transmits it to the CSCF 30 (step S14), and the call control unit 14 is in a restricted state. (Step S15). On the other hand, when the communication quality of the dummy packet exceeds a predetermined level (step S13; recovery), the determination unit 13 generates a recovery notification and transmits it to the CSCF 30 (step S16). 14 changes to a normal state (step S17).

  Next, the processing of the CSCF 30 will be described using FIG. In the CSCF 30, first, the notification receiving unit 31 receives a bandwidth congestion notification or a recovery notification from the gateway node 10 (step S21). When the notification receiving unit 31 receives the bandwidth congestion notification (step S22; bandwidth congestion notification), the gateway state storage unit 32 associates the IP address of the transmission source gateway included in the notification with the flag “0”. Store (update) (step S23). On the other hand, when the notification receiving unit 31 receives the recovery notification (step S22; recovery notification), the gateway state storage unit 32 sets the IP address of the transmission source gateway included in the notification and the flag “1”. Are stored (updated) in association with each other (step S24).

  Next, a call control process executed for an INVITE message (call establishment request signal) transmitted from the mobile phone M will be described with reference to FIGS. 7 to 9, for convenience of explanation, the gateway node and CSCF on the transmission side are respectively referred to as gateway node 10a and CSCF 30a, and the gateway node and CSCF on the reception side are respectively referred to as gateway node 10b and CSCF 30b.

  First, a general flow until a call is established will be described with reference to FIG. When the source mobile phone M transmits an INVITE message to perform the outgoing call process, the INVITE message is transmitted to the gateway node 10a, CSCF 30a, CSCF 30b, and gateway node 10b (step S31), and finally the destination mobile phone. To M.

  If the call is being sent, the response message “100 Trying” is transmitted to the node that is the transmission source of the INVITE message in each node (step S32). When the call is in progress, the response message “180 Ringing” is transmitted from the destination mobile phone M to the source mobile phone M via the IP backbone network NB (step S33). Thereafter, when the user answers the call on the destination mobile phone M, a response message “200 OK” is transmitted from the destination mobile phone M to the source mobile phone M via the IP backbone network NB (step S30). S34). Thereby, a regular call is established between the mobile telephones M (step S35).

  Next, call control based on the state of the gateway node 10b on the receiving side will be described with reference to FIG.

  When the determination unit 13 of the gateway node 10b determines that the communication quality of the dummy packet has become less than a predetermined level (step S41), the determination unit 13 transmits a bandwidth congestion notification to the CSCF 30b (step S42), and the gateway node 10b The call control unit 14 transitions to a restricted state (step S43). In the CSCF 30b, the gateway state storage unit 32 updates the flag corresponding to the gateway node 10b to “0” based on the bandwidth congestion notification (step S44).

  Thereafter, it is assumed that the call control unit 33 of the CSCF 30b receives an INVITE message transmitted from the mobile phone M that is the transmission source and that has passed through the gateway node 10a and the CSCF 30a (step S45). Here, it is assumed that the transfer destination of this INVITE message is the gateway node 10b. The call control unit 33 accesses the gateway state storage unit 32 and reads a flag corresponding to the gateway node 10b. Since the read flag is “0”, the call control unit 33 determines that the gateway node 10b is in a restricted state (step S46, call control step). Subsequently, the call control unit 33 transmits a response message “580 precondition failure” to the CSCF 30a (step S47, call control step), and ends the process. That is, the call control unit 33 rejects the establishment of the call.

  Thereafter, when the determination unit 13 of the gateway node 10b determines that the communication quality of the dummy packet has reached a predetermined level (step S48), the determination unit 13 transmits a recovery notification to the CSCF 30b (step S49), and the gateway node 10b The call control unit 14 changes to the normal state (step S50). Therefore, during the period from step S43 to step S50, the outgoing / incoming calls are restricted in the gateway node 10b. In the CSCF 30b, the gateway state storage unit 32 updates the flag corresponding to the gateway node 10b to “1” based on the recovery notification (step S51).

  Thereafter, it is assumed that the call control unit 33 of the CSCF 30b receives the INVITE message transmitted from the mobile phone M that is the transmission source and passed through the gateway node 10a and the CSCF 30a (step S52). Again, it is assumed that the transfer destination of this INVITE message is the gateway node 10b. The call control unit 33 accesses the gateway state storage unit 32 and reads a flag corresponding to the gateway node 10b. Since the read flag is “1”, the call control unit 33 determines that the gateway node 10b is in the normal state (step S53, call control step). Subsequently, the call control unit 33 transmits an INVITE message to the gateway node 10b (step S54, call control step). Thereafter, processing similar to that shown in FIG. 7 is performed. That is, the call control unit 33 performs processing for establishing a regular call.

  Next, call control based on the state of the originating gateway node 10a will be described with reference to FIG.

  When the determination unit 13 of the gateway node 10a determines that the communication quality of the dummy packet has become less than a predetermined level (step S61), the call control unit 14 of the gateway node 10a transitions to a restricted state (step S62). When the call control unit 14 receives an INVITE message from the mobile phone M in the restricted state (step S63), the call control unit 14 transmits a response message “580 precondition failure” to the mobile phone M (step S64, call Control step), the process ends. That is, the call control unit 14 rejects establishment of the call.

  Thereafter, when the determination unit 13 of the gateway node 10a determines that the communication quality of the dummy packet has reached a predetermined level (step S65), the call control unit 14 of the gateway node 10a transitions to a normal state (step S66). Therefore, during the period from step S62 to step S66, outgoing / incoming calls are restricted in the gateway node 10b.

  When the call control unit 14 receives an INVITE message from the mobile phone M in the normal state (step S67), the call control unit 14 transfers the INVITE message to the CSCF 30a (step S68, call control step). Thereafter, processing similar to that shown in FIG. 7 is performed. That is, the call control unit 14 performs processing for establishing a regular call.

  As described above, according to the present embodiment, as a result of normal packets being transmitted with priority over dummy packets in the IP backbone network NB, the communication quality of the dummy packets decreases earlier than that of the regular packets. By utilizing this fact and controlling the call establishment based on the communication quality of the dummy packet, it is possible to establish a regular call only in an environment where a certain communication quality is guaranteed without performing bandwidth reservation. Become. That is, it becomes possible to guarantee the communication quality of the network.

  Such a communication quality assurance method will be described with reference to FIG. FIG. 10 is a graph showing the relationship between regular call and dummy call traffic and call control processing. In the graph of FIG. 10, the vertical axis indicates the traffic volume, and the horizontal axis indicates time.

The bandwidth resource of the IP backbone network NB is B (bps), the bandwidth consumed by all regular packets transmitted via regular calls is P _A (bps), and the bandwidth consumed by dummy packets transmitted via dummy calls is Let P _B (bps). Further, it is assumed that the amount of dummy packets constantly transmitted from the dummy packet transmitting / receiving unit 11 originally consumes a bandwidth corresponding to P _X (bps). Furthermore, it is assumed that the determination unit 13 determines that the communication quality of the dummy packet is less than a predetermined level when the bandwidth consumed by the dummy packet transmission / reception unit 11 drops to P _Y (bps).

Initially, there is room in the bandwidth of the IP backbone network NB, and normal packets and dummy packets are transmitted without delay. However, gradually beginning increasing the transmission amount of regular packets, the time T _P when IP backbone margin is eliminated in the band of the network NB. Because after time T _P is also growing the transmission of normal packets, the time T _P after are transmitted in preference to normal packet dummy packet. As a result, the dummy call becomes insufficient in bandwidth, and communication quality decreases such as transmission delay and discard of dummy packets.

At time T _Q , it is determined that the communication quality of the dummy packet has become less than a predetermined level, so that establishment of a regular call for a new call establishment request signal is rejected from this point. As a result, the transmission amount of regular packets (bandwidth consumed by regular packets) is maintained at a constant level, and established regular calls can continue to secure necessary bandwidth.

Thereafter, the communication quality of the dummy packet is restored because the transmission of normal packets is decreased at time T _R, as a result, it is possible to establish a new normal call at time T _R later. In the example of FIG. 10, and also eliminates the insufficient band of the dummy call at time T _S.

  In the present embodiment, whether or not a regular call can be established can be determined based on the communication quality of the dummy packet. That is, the communication device in the call control system does not need to store the bandwidth resource of the IP backbone network NB (an amount corresponding to B (bps) in FIG. 10). The present invention can be implemented by determining only what percentage of the bandwidth resource is reserved for the dummy call bandwidth.

  Further, according to the present embodiment, for an INVITE message that is transmitted from the mobile phone M on the transmission side and transmitted through the access network NA on the transmission side, the gateway node 10 on the transmission side that first receives the message. Determines whether or not a call can be established, so that whether or not a call can be established can be determined early.

  Further, according to the present embodiment, when the communication quality of the dummy packet is lower than a predetermined level in the gateway node 10 on the called side, the CSCF 30 on the called side that receives the INVITE message before the gateway node 10 Since it is determined whether or not a call can be established, whether or not a call can be established can be determined early. In addition, since the CSCF 30 on the receiving side stores the states (regulated state or normal state) of the plurality of gateway nodes 10, call establishment control can be centrally executed to a certain degree.

  The present invention has been described in detail based on the embodiments. However, the present invention is not limited to the above embodiment. The present invention can be modified in various ways as described below without departing from the scope of the invention.

  Although the call control system 2 shown in the above embodiment uses the mechanism of IMS and SIP, the form and method of the network to which the present invention is applied are not limited, and various forms and methods are available. Applicable to network.

  In the above embodiment, the mobile phone M is used as a communication terminal, but other types of mobile communication terminals and fixed terminals may be used as communication terminals.

1 is a diagram illustrating an overall configuration of a communication system including a call control system according to an embodiment. It is a figure which shows the function structure of the gateway node shown in FIG. It is a figure which shows the hardware constitutions of the gateway node shown in FIG. It is a figure which shows the function structure of CSCF shown in FIG. It is a flowchart which shows the process of the gateway node shown in FIG. It is a flowchart which shows the process of CSCF shown in FIG. It is a sequence diagram which shows the general flow until call establishment. It is a sequence diagram which shows the call control based on the state of the gateway node of the receiving side. It is a sequence diagram which shows the call control based on the state of the gateway node of a transmission side. It is a graph which shows the relationship between the traffic of a regular call and a dummy call, and a call control process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Communication system, 2 ... Call control system, 10, 10a, 10b ... Gateway node (relay apparatus, gateway apparatus), 11 ... Dummy packet transmission / reception part (dummy packet transmission means), 12 ... Measurement part (measurement means), 13 ... determining unit (notification transmitting unit), 14 ... call control unit (call control unit), 20 ... router, 30, 30a, 30b ... CSCF (call control device), 31 ... notification receiving unit (notification receiving unit), 32 ... Gateway state storage unit (storage unit), 33 ... call control unit (call control unit), M ... mobile phone (communication terminal), NA ... access network (outgoing side external network, destination side external network), NB ... IP backbone network (network)

Claims (4)

A call control system for establishing a call between a calling terminal and a receiving terminal based on a call establishment request signal transmitted from a calling terminal in a network that relays a packet to be transmitted based on a transmission priority. ,
A regular packet that is transmitted via a call established between the originating terminal and the terminating terminal by establishing a dummy call between one relay device in the network and another relay device in the network Dummy packet transmission means for transmitting a dummy packet having a lower transmission priority than the dummy call,
Measuring means for measuring the communication quality of the dummy packet transmitted by the dummy packet transmitting means;
When the communication quality measured by the measuring means is less than a predetermined level, the call establishment is rejected for a new call establishment request signal, and when the communication quality is a predetermined level or more, Call control means for establishing a call in response to a new call establishment request signal;
A call control system comprising: A call control system for establishing a call between a calling terminal and a receiving terminal based on a call establishment request signal transmitted from a calling terminal in a network that relays a packet to be transmitted based on a transmission priority. ,
An originating gateway device connected to the originating external network in which the originating terminal is located;
A destination gateway device connected to the destination external network where the receiving terminal is located;
With
The originating gateway device is
A dummy packet is established between the destination gateway device and a dummy packet having a lower transmission priority than a regular packet transmitted via a call established between the originating terminal and the terminating terminal, Dummy packet transmission means for transmitting via the dummy call;
Measuring means for measuring the communication quality of the dummy packet transmitted by the dummy packet transmitting means;
If the communication quality measured by the measuring means is less than a predetermined level, call establishment is rejected for the new call establishment request signal transmitted from the calling terminal, and the communication quality is a predetermined level. If so, the call control means for establishing a call in response to the new call establishment request signal,
A call control system. A call control system for establishing a call between a calling terminal and a receiving terminal based on a call establishment request signal transmitted from a calling terminal in a network that relays a packet to be transmitted based on a transmission priority. ,
An originating gateway device connected to the originating external network in which the originating terminal is located;
A destination gateway device connected to the destination external network where the receiving terminal is located;
A call control device capable of communicating with the destination gateway device;
With
The destination gateway device is
A dummy call is established between the originating gateway device and a dummy packet having a lower transmission priority than a regular packet transmitted via a call established between the originating terminal and the terminating terminal, Dummy packet transmission means for transmitting via the dummy call;
Measuring means for measuring the communication quality of the dummy packet transmitted by the dummy packet transmitting means;
Based on the communication quality measured by the measurement means, comprising a notification transmission means for transmitting a notification indicating whether or not a call can be established via the destination gateway device to the call control device,
The call control device
Notification receiving means for receiving a notification transmitted from the notification transmitting means;
Based on the notification received by the notification receiving means, storage means for associating and storing identification information of the destination gateway device and availability information indicating whether or not a call can be established via the destination gateway device;
When the availability information associated with the identification information indicates that a call cannot be established via the destination gateway device, a new call establishment request signal transmitted from the calling terminal to the receiving terminal is added. On the other hand, if the call establishment is rejected and the availability information indicates that the call can be established via the destination gateway device, call control means for establishing a call in response to the new call establishment request signal With
A call control system. A call in a call control system for establishing a call between a calling terminal and a receiving terminal based on a call establishment request signal transmitted from the calling terminal in a network that relays transmitted packets based on the transmission priority. A control method,
A regular packet that is transmitted via a call established between the originating terminal and the terminating terminal by establishing a dummy call between one relay device in the network and another relay device in the network A dummy packet transmission step of transmitting a dummy packet having a lower transmission priority than the dummy call via the dummy call;
A measurement step of measuring communication quality of the dummy packet transmitted in the dummy packet transmission step;
When the communication quality measured in the measurement step is less than a predetermined level, call establishment is rejected for a new call establishment request signal, and when the communication quality is equal to or higher than the predetermined level. A call control step for establishing a call in response to a new call establishment request signal;
A call control method comprising:

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