JP2004056336A - VoIP SYSTEM - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a VoIP (voice over internet protocol) system capable of performing a seamless hand-over with less voice interruption and a small delay even when the system adopts a mobile terminal. <P>SOLUTION: When the Internet protocol mobile is installed to the terminal 1a and a base station 6a and the mobile terminal 1a transmits data to the base station 6a, the base station 6a extracts a packet on the basis of a channel, a slot and a code assigned to itself from an interface 7a, transmits to a network 5 , and starts a speech when call connection control is finished. The interface 7a, a gateway 2a, and a gatekeeper 3 or the like perform each control. When a hand-over takes place during a speech by the mobile terminal 1a, a speech opposite party transfers data to the mobile terminal 1a to the base station 6a connected to the mobile terminal 1a and its adjacent base station by means of multicast / broadcast and wirelessly transmits data leading to the mobile terminal 1a only to the base station to which the position of the mobile terminal 1a is registered. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a VoIP (Voice Over Internet Protocol) system in which a terminal device makes a voice call via the Internet. More specifically, the present invention relates to a case where a terminal device is a mobile terminal, and The present invention relates to a VoIP system in a case where wireless communication is performed by effectively performing handover.
[0002]
[Prior art]
The VoIP system is a system for making a voice call via a network without using a dedicated voice line using an existing analog line. In this case, if the network can transmit IP packets, even if it is a digital leased line network, a frame relay network, an IP-based virtual network (IP-VPN), a wide area network (WAN: Wide Area Network), and a LAN (LAN) Local Area Network), or a mixture of these communication networks. Further, the VoIP system can economically realize a long-distance call and can construct an integrated network of voice communication and data communication because of the characteristics of packet communication.
[0003]
FIG. 4 is a configuration diagram of a conventional VoIP system when a fixed terminal is applied as a terminal device. A plurality of fixed terminals 11a, 11b to 11n fixedly installed in an office or the like are connected to a network 15. For example, when a desired telephone number is dialed from the fixed terminal 11a, the telephone number dialed by the gateway 12a connected to the fixed terminal 11a to the gatekeeper 13 via the routers 14a and 14c connected to the network 15 Inquire about the IP address corresponding to. Then, when the gateway 12a obtains an IP address from the gatekeeper 13 and performs a calling procedure in a predetermined sequence, the fixed terminal 11a can start a call with the dialed communication partner terminal device. As described above, in the current embodiment of the VoIP system, the terminal device is generally a fixed terminal.
[0004]
A VoIP system that assumes a mobile terminal in addition to a fixed terminal as a terminal device is disclosed in, for example, JP-A-2001-119740 and JP-A-2002-44740. The former discloses a technique in which when a mobile terminal performs handover, voice communication is transferred without delay by duplicating and transmitting communication data to base stations before and after the transfer. The latter discloses a technology capable of constructing a VoIP system without providing an IP address to a mobile terminal by providing an architecture in which a gateway can process VoIP Internet protocol traffic.
[0005]
FIG. 5 is a configuration diagram of a conventional VoIP system when a mobile terminal is applied as a terminal device. Wireless communication is performed between each of the mobile terminals 1a to 1n and each of the base stations 8a, 8b to 8n or equipment corresponding thereto. The interface devices 7a ', 7b' to 7n 'connected to the respective base stations 8a, 8b to 8n take an interface with the network 5. The equipment such as the gateways 2a and 2b, the routers 4a, 4b and 4c, and the gatekeeper 3 are the same as those of the VoIP system of FIG. That is, with the configuration as shown in FIG. 5, even when the terminal device is a mobile terminal, a VoIP system can be constructed similarly to a fixed terminal.
[0006]
[Problems to be solved by the invention]
However, when the terminal device of the VoIP system is a mobile terminal as shown in FIG. 5, in addition to a regular handover procedure in wireless communication, a handover in a network, that is, a predetermined It is necessary to repeat the procedure for making and receiving calls in sequence. As a result, interruption of audio or audio delay at the time of handover occurs, and seamless handover cannot be performed.
[0007]
According to the technique disclosed in Japanese Patent Application Laid-Open No. 2001-119740, when a handover occurs, the handover is performed by duplexing and transmitting communication data to the base station before and after the transition. Sometimes, it is necessary to inform the other party of the call to the destination base station and its own identification number, and it takes time to transfer packets for performing handover processing and to interpret and control the packets. The performance equivalent to the wireless communication handover cannot be obtained.
[0008]
In addition, since the mobile terminal and the base station do not have the Internet protocol, it is necessary to manage the identification number, telephone number, and IP address of the mobile terminal, so that the conversion table of the gatekeeper 3 becomes large. However, there is a problem that transmission delay occurs between the base station and the interface device, and between the interface device and the network due to the intermediary of the interface device between the base station and the network, and a problem occurs in performing handover. is there. That is, in the conventional VoIP system, when the terminal device is a mobile terminal, there is still a problem of voice interruption and delay in handover. Further, since the mobile terminal and the base station do not implement the Internet protocol, system problems such as the need to manage the identification number, telephone number, and IP address of the mobile terminal have not been solved.
[0009]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to realize a seamless handover with little interruption and delay of voice even when a mobile terminal is incorporated in a VoIP system. An object of the present invention is to provide a VoIP system that can easily manage numbers and IP addresses.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention provides a VoIP system for making a voice call on the Internet, which has a contact point between a mobile terminal having an Internet protocol and a mobile terminal having its own IP address, an Internet protocol being mounted, and a network. In addition to transmitting and receiving data constituted by IP packets to and from the network, a mobile communication connection with the mobile terminal can be performed, and the IP packet is inserted into a predetermined data area. Or a base station that can be extracted.
[0011]
In the embodiment, in a VoIP system for making a voice call on the Internet, a mobile terminal having an Internet protocol and own IP address, a base station having an Internet protocol and having a contact point with a network, and a base station , A frequency division multiple access (FDMA: Frequency Division Multiple Access), a time division multiple access (TDMA: Time Division Multiple Access), or a code division multiple access (CDMA: Code Division Multiple Access). Establish a connection, insert or extract an IP packet in the data area of any of the assigned channels, slots, or codes, and An interface device for transmitting and receiving data composed of IP packets between the gateways, a gateway for controlling signaling of incoming and outgoing calls, a router connected to the gateway for routing IP packets, and a conversion table for telephone numbers and IP addresses. And a network infrastructure in which any one of digital leased line networks, frame relay networks, IP-VPNs, WANs, LANs, or a mixture thereof are connected.
[0012]
In the VoIP system of the present invention, the mobile terminal and the base station implement the Internet protocol, and the mobile terminal has an IP address. As a result, it is not necessary to manage the identification number of the mobile terminal in association with the telephone number and the IP address, and only the conversion table between the telephone number and the IP address is required, so that the gatekeeper having the conversion table is extremely simplified.
[0013]
Further, the VoIP system of the present invention, when a handover occurs to a mobile terminal, transmits data to the mobile terminal to a base station to which the mobile terminal is connected and a base station adjacent thereto, or all base stations. The transmission is performed by multicast or broadcast, and data to the mobile terminal is wirelessly transmitted only to the base station where the location of the mobile terminal is registered.
[0014]
In this configuration, since the Internet protocol is implemented in the base station, when a handover request is issued to a mobile terminal, the information of the handover request is transmitted to the other party who is talking with the mobile terminal. The call partner, after receiving the handover request information, until the processing related to the handover ends, the base station connected to the mobile terminal to be handed over and its neighboring base stations, or all base stations, The data to the mobile terminal to be handed over is transferred by multicast or broadcast, and the mobile terminal to be handed over wirelessly transmits data only to the base station whose location is registered. During the transfer by multicast or broadcast, the change information of the transfer destination base station or the like of the mobile terminal is transferred at the same time as the communication information, and the transfer of the multicast or broadcast is terminated when the transfer preparation is completely completed. As a result, when a handover of the mobile terminal occurs, the time during which the relevant call is reconnected and the voice is interrupted can be almost eliminated.
[0015]
Further, in the VoIP system of the present invention, the base station includes a plurality of base stations, the plurality of base stations periodically receive a synchronization signal from a higher-level device or a master base station, and the data of each base station is synchronized. It is characterized by being synchronized by a signal.
[0016]
That is, when the mobile terminal performs a handover, the base station before the handover and the base station after the handover are synchronized because the base station before the handover and the base station after the handover continuously transmit downlink data to the mobile terminal. Is preferably removed. Therefore, the VoIP system of the present invention synchronizes from the higher-order base station or the master base station to all the slave base stations, so that synchronization can be performed in a short time at the time of handover. Therefore, the same performance as that of the normal mobile communication handover can be obtained without interruption of voice at the time of the handover, and no trouble occurs even when the mobile terminal is incorporated in the VoIP system. As means for synchronizing between base stations, higher-level equipment (for example, a base station controller) of the base station or a base station serving as a master periodically transmits a synchronization signal to each base station and serves as a slave. It is common that the base station follows it.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a VoIP system according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram of a VoIP system according to the present invention. The VoIP system according to the present invention includes a mobile terminal 1a to 1n having an Internet protocol and an IP address in advance, a plurality of base stations 6a and 6b to 6n having an Internet protocol and a contact point with a network 5, and signaling. 2a and 2b for controlling the network, routers 4a, 4b and 4c for routing packets, a gatekeeper 3 having a telephone number / IP address conversion table, a digital private line network for connecting wired sections, a frame relay network, It has an infrastructure of a network 5 such as an IP-VPN, a WAN, and a LAN.
[0018]
Further, each of the base stations 6a, 6b to 6n includes interface devices 7a, 7b to 7n that serve as interfaces with the network 5. The interface devices 7a, 7b to 7n perform mobile communication connection by any of frequency division multiple access (FDMA), time division multiple access (TDMA), or code division multiple access (CDMA), and , A slot, or a code, to insert or extract an IP packet, and transmit / receive data constituted by the IP packet to / from the network. FIG. 1 shows a state in which the mobile terminal 1a performs handover from the base station 6a to the base station 6b.
[0019]
Hereinafter, the operation of the VoIP system for one communication system will be described. The mobile terminal 1a and the base station 6a are connected by mobile communication by radio, and packetized data is transmitted from the mobile terminal 1a on which the Internet protocol is implemented to the base station 6a. Similarly, the base station 6a on which the Internet protocol is mounted extracts an IP packet from any data area of the channel, slot, or code assigned to itself from the interface device 7a of the base station 6a, and transmits the IP packet to the network 5. . In the downlink communication from the base station 6a to the mobile terminal 1a, the reverse process is performed.
[0020]
When starting a call, first, the mobile terminal 1 dials the telephone number of the other party. The mobile terminal 1 exchanges packets for connecting a call based on a signaling protocol. At this time, it is necessary to know the IP address of the other party, and this is performed by inquiring of the gatekeeper 3 connected to the network 5.
[0021]
The most frequently used VoIP signaling protocol is H.264, which is a standard related to a control protocol recommended by ITU-T (International Telecommunication Union). 323. FIG. 323 is an example of the outgoing call flow in H.323. H. H.323 is basically applied to a packet network and extended to multimedia based on an existing telephone network protocol. H. Unlike H.323, there is an outgoing call in SIP based on the same text-based Internet protocol as HTTP. FIG. 3 is an example of an outgoing call flow in SIP.
[0022]
In the VoIP signaling protocol, the above H.264 protocol is used. It is common to use either the outgoing call flow in H.323 (FIG. 2) or the outgoing call flow in SIP. As shown in FIG. 3, when SIP is used for the signaling protocol, the gateways 2a and 2b are called proxy servers, and the gatekeeper 3 is called a location server. The routers 4a, 4b, and 4c determine the route of the packet, and the gateways 2a and 2b may be mounted on the routers 4a and 4b, respectively.
[0023]
H. shown in FIG. The flow of the outgoing call flow in H.323 will be described by applying to the VoIP system of FIG. When the mobile terminal 1a starts a call, first, the mobile terminal 1a dials the telephone number of the other party. Then, the mobile terminal 1a exchanges a packet for connecting a call based on a signaling protocol. At this time, the mobile terminal 1a needs to know the IP address of the other party, and this is performed by inquiring of the gatekeeper 3 connected to the network 5.
[0024]
That is, the mobile terminal 1a transmits an ARQ (Admission Request: permission request) to the gatekeeper 3 when dialing the telephone number of the other party to make a call (step S1). Then, the gatekeeper 3 performs a connection authorization application, converts the telephone number into an IP address, and transmits an ACF (Admission Confirmation: acknowledgment) to the originating mobile terminal 1a (step S2). Then, the mobile terminal 1a performs SETUP (Call Setup: call setup) with respect to the mobile terminal of the other party (step S3).
[0025]
As a result, the partner mobile terminal transmits an ARQ (Admission Request: permission request) to the gatekeeper 3 (step S4), receives an ACF (Admission Confirmation: acknowledgment) from the gatekeeper 3, and issues a connection authorization application. Perform (Step S5). Further, the destination mobile terminal transmits ALERT (Alertong: call) to the originating mobile terminal 1a (step S6), and transmits CONNECT (Call Connect: response) (step S7). When the control for connecting the call is completed in this way, a call is started between the mobile terminal 1a of the caller and the mobile terminal of the other party (step S8). In the figure, thick arrows indicate the flow of RAS (Reliability Availability Service) messages, and thin arrows indicate the flow of call signaling messages.
[0026]
When the control for connecting the call is completed as in the outgoing call flow shown in FIG. 2, a call is started, but a handover may occur in the mobile terminal 1a during the call. For example, as shown in FIG. 1, when the mobile terminal 1a moves while communicating with the base station 6a, handover to the base station 6b is performed. When the electric field strength from the currently connected base station 6a falls below a prescribed threshold value and the electric field strength from another base station 6b exceeds the prescribed threshold value, the mobile terminal 1a receives a handover request from the mobile terminal 1a. Done.
[0027]
Then, the mobile terminal of the call partner needs to know that the handover has occurred and change the destination. At this time, if the re-call control as shown in the outgoing call flow of FIG. 2 is performed in order to perform the handover instantaneously, the interruption of the voice and the voice delay become severe. Therefore, after receiving the information of the handover request, the communication partner's terminal apparatus transmits the handover request to the base station 6a connected to the mobile terminal 1a performing the handover and the adjacent base station until the processing related to the handover ends. The mobile terminal 1a transfers data to the mobile terminal 1a by multicast or broadcast, and wirelessly transmits data to the mobile terminal 1a only to base stations (for example, 6a and 6b) where the mobile terminal 1a is registered.
[0028]
Thereby, the mobile terminal 1a can execute a seamless handover with little interruption of audio and little audio delay. When this VoIP system is applied to a closed small network such as a LAN, there is no problem even if data is transferred to all base stations if a sufficient band is prepared. Therefore, the control of the VoIP system is facilitated by transferring the data to all the base stations. Also, the other party communicating with the mobile terminal does not necessarily need to be the mobile terminal, and one of them is a fixed terminal, or the fixed terminal and the fixed terminal talk by the VoIP system as in the conventional technology as shown in FIG. You can also. Further, since the base station is provided with the interface device, it is possible to communicate with an external telephone network. Further, since the VoIP system performs packet communication using voice as data, data communication is possible simultaneously with voice communication.
[0029]
Next, an outgoing call flow when SIP is used for the signaling protocol shown in FIG. 3 will be described by applying to the VoIP system of FIG. When the mobile terminal 1a starts a call, the mobile terminal 1a transmits INVITE (message participation request) to the proxy server (gateway 2a) (step S11). Then, an inquiry about the message participation request of the mobile terminal 1a is made between the proxy server (gateway 2a) and the location server (gatekeeper 3) (step S12). Further, RING (calling) is performed from the proxy server (gateway 2a) to the mobile terminal of the other party (step S13), and SETUP (Call Setup: call setup) is performed from the mobile terminal 1a to the location server (gatekeeper 3). Is performed (step S14).
[0030]
Further, the mobile terminal of the other party performs Ringing (ringing) to the proxy server (gateway 2a) at a frequency of 180 Hz (step S15), and Ringing (ringing) from the proxy server (gateway 2a) to the mobile terminal 1a of the transmission source. Is performed (step S16). At the same time, the mobile terminal of the other party transmits a response signal at a frequency of 2000 KHz to the proxy server (gateway 2a) (step S17), and further transmits a response signal from the proxy server (gateway 2a) to the mobile terminal 1a of the transmission source. Is transmitted (step S18). Then, ACK (Acknowledge: acknowledgment) is transmitted from the mobile terminal 1a to the proxy server (gateway 2a) (step S19), and ACK (Acknowledg: affirmative) is transmitted from the proxy server (gateway 2a) to the communication partner mobile terminal. Response) is transmitted (step S20). As a result, a call is made between the originating mobile terminal 1a and the communication partner mobile terminal (step S21).
[0031]
In this way, when control for connecting a call is performed according to the outgoing call flow by SIP in FIG. 3, a call is started, but handover may occur to the mobile terminal 1a during the call. . At this time, after receiving the information of the handover request, the mobile terminal of the other party communicates with the base station 6a connected to the mobile terminal 1a performing the handover and the adjacent base station until the processing related to the handover is completed. Then, the data to the mobile terminal 1a is transferred by multicast or broadcast, and the data to the mobile terminal 1a is wirelessly transmitted only to the base station (for example, 6a, 6b) where the mobile terminal 1a is registered. Thereby, the mobile terminal 1a can execute a seamless handover with little interruption of audio and little audio delay.
[0032]
That is, according to the VoIP system incorporating the mobile terminal according to the embodiment, the base station is provided with the interface device to implement the Internet protocol, and the mobile terminal is also implemented with the Internet protocol to have an IP address. Further, when a handover occurs in the mobile terminal, the mobile terminal of the other party multicasts data to the mobile terminal to the base station to which the mobile terminal is connected and its adjacent base station, or to all base stations. Or transfer by broadcast. Then, the mobile terminal wirelessly transmits data to the mobile terminal only to the base station whose location is registered. Therefore, the mobile terminal can smoothly perform the handover without causing any interruption or delay in the sound. Further, in order to synchronize between base stations before and after handover, a synchronization signal is periodically transmitted from a master base station to a number of slave base stations. In this way, by synchronizing between the base stations, handover can be smoothly performed without interruption of voice.
[0033]
The embodiment described above is an example for describing the present invention, and the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the invention. In the above embodiment, the case where the handover is performed by the communication between the mobile terminals has been described. However, it goes without saying that the VoIP system of the present invention can be applied to the handover when the communication is performed from the mobile terminal to the fixed terminal.
[0034]
【The invention's effect】
As described above, according to the VoIP system of the present invention, even if a mobile terminal is incorporated in the VoIP system, a seamless handover with less interruption of audio and less audio delay can be performed. Further, since there is no need to manage the identification number, telephone number, and IP address of the mobile terminal, the conversion table for telephone numbers and IP addresses may be small, and their management is simplified.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a VoIP system according to the present invention.
FIG. 323 is an example of the outgoing call flow in H.323.
FIG. 3 is an example of an outgoing call flow in SIP.
FIG. 4 is a configuration diagram of a conventional VoIP system when a fixed terminal is applied as a terminal device.
FIG. 5 is a configuration diagram of a conventional VoIP system when a mobile terminal is applied as a terminal device.
[Explanation of symbols]
1a-1n mobile terminal, 2a, 2b, 12a, 12b gateway, 3,13 gatekeeper, 4a, 4b, 4c, 14a, 14b, 14c router, 5,15 network, 6a, 6b-6n, 8a, 8b-8n base Station, 7a, 7b to 7n, 7a ', 7b' to 7n 'Interface device, 11a, 11b to 11n Fixed terminal.

Claims (3)

In a VoIP system for making voice calls over the Internet,
A mobile terminal that has an Internet protocol and has its own IP address;
An Internet protocol is implemented, and it is possible to transmit and receive data constituted by IP packets to and from the network with a contact point with a network, and to perform a mobile communication connection with the mobile terminal. And a base station capable of inserting or extracting the IP packet in a predetermined data area. The VoIP system according to claim 1,
When a handover occurs in the mobile terminal, the base station to which the mobile terminal is connected and its adjacent base stations, or to all base stations, to transfer data to the mobile terminal by multicast or broadcast A VoIP system wherein the mobile terminal wirelessly transmits data to the mobile terminal only to a base station whose location is registered. In the VoIP system according to claim 1 or claim 2,
The base station includes a plurality of base stations, the plurality of base stations periodically receive a synchronization signal from a higher-level device or a base station serving as a master, and data of each base station is synchronized by the synchronization signal. A VoIP system.

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