JPH0846643A - Packet service uninterrupted handover method - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a packet service uninterrupted handover method capable of performing handover without loss of data during communication. [Structure] A step of regulating communication during link switching in a packet switch, and a step of taking over a packet waiting for a response to a buffer of the link after switching and holding it, and using a resend function of a packet protocol to prevent data loss And between packet switches or between packet switches,
A packet service non-disruptive handover method comprising steps of setting up and releasing a link by taking over information on a link and a communication state, and exchanging information with a location register for other mobile communication-specific processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packet service uninterrupted handover method in mobile data communication realized by a packet network and a mobile station connected thereto.

[0002]

2. Description of the Related Art First, a packet switching system and a handover in mobile communication which are the premise of the present invention will be described. First, the packet switching system will be described by taking ISDN as an example. FIG. 6 is a diagram showing the structure of an ISDN packet network. The packet terminal 1 is accommodated in the packet switch 3 via the ISDN switch 2 which is a subscriber line. The packet switch 3 is connected via a packet relay network 4 to a packet switch 5 that accommodates a terminal of a communication partner,
Further, it is possible to communicate with the terminal 7 via the ISDN exchange 6. Between the terminal 7 and the packet switch 5,
The communication channel is controlled by the ISDN channel control procedure, and a protocol in which a packet network control procedure is added to ITU-T Recommendation X.25 is used.

FIG. 7 is a diagram showing an example of a communication sequence and a communication phase. The packet communication conforming to X.25 of the above-mentioned ITU-T recommendation has three phases of call setup, data transfer, and call release. In addition, in the case of ISDN packet, in addition to these three phases, ISDN There is a channel setup phase and an ISDN channel release phase. Regarding these, for example, "TTC Standard Volume II" issued by Nippon Telegraph and Telephone Advisory Committee February 1994,
Alternatively, it is possible to refer to the description in the NTT technical reference material “INS Net Service Interface Conditions” issued by NTT January 1993. Hereinafter, a description will be given according to the sequence. If the packet terminal 1 accommodating the ISDN network
In order to perform packet communication, first, a channel for packet communication is set through the ISDN exchange 2 and with the packet exchange 3 by the ISDN channel control protocol. After the setting of the communication channel is completed, the packet terminal 1 transmits a CR packet to the packet switch 3, and the packet switch 3 which receives this CR packet,
The CN packet is transmitted to the destination packet switch 5 that accommodates the partner terminal, and the destination packet switch 5 transmits the CN packet to the destination terminal.

When the call setting is accepted, the CA at the receiving terminal is
The packet is transmitted to the destination packet switch 5, the CC packet is transmitted from the destination packet switch 5 to the source packet switch 3, and the source packet switch 3 transmits the CC packet to the source terminal 1. Is completed. When the call setup phase ends, the data transfer phase is entered,
DT packets can be transferred between terminals. In the circuit switching method typified by general telephones, when the telephone is in a call state, the exchange simply keeps the call path and the contents of the communication are transparent.However, in the packet switching method, the exchange is used even in the data transfer phase. There is a feature of performing error correction, retransmission control, sequence control, flow control, etc., and by this feature, reliability of data transfer is improved. When the connection is released, a call release packet is transmitted and received between the terminals to shift to the call release phase.

Next, the handover will be described. Regarding this, for example, "Radio System Development Center", "Second Generation Cordless Telephone System Standards", issued in March 1993, or Nippon Telegraph and Telephone Advisory Committee (February, 1994) The description in “TTC Standard Volume II” can be referred to. Handover refers to the function of switching channels while maintaining communication status.
Many mobile communication networks provide this function so that communication can be continued even if a terminal in communication moves to another wireless area. Figure 8 shows the second-generation cordless phone system.
The network structure of (PHS) is shown. Mobile mobile phone 1 is R
Wireless base station 2 with wireless interface compliant with CR standard
The radio base station 2 is connected to the ISDN exchange by the TTC standard ISDN interface for mobile telephones. From the ISDN switch onward, it is the same as a normal ISDN network.

The function of the location register is controlled by the high function exchange processing node 7, and the high function exchange processing node 7
Is connected to each ISDN exchange through a common line communication network conforming to the ITU-T Recommendation No. 7 signal system. According to the handover function, for example, even if the mobile mobile phone 1 in a call moves from the cell of the radio base station CS # 1 to the cell of the CS # 2, the call can be continued. FIG. 9 shows an example of a handover sequence. As can be seen from the figure, the handover in the mobile communication based on the circuit switching method physically disconnects the communication from the original line by setting the line in the new wireless area and switching from the original line. Yes, but relatively easy to achieve.

[0007]

As described above, in the packet switching system, the call state is changing even in the data transfer phase, and the terminal side and the network side are conscious of this state for control. In addition, in the frame where the packet appears,
Sequence numbers for transmission and reception are given, and the terminals and the network side constantly monitor for missing frames and abnormal sequences. Further, in the packet network, it is necessary to hold the data packet until the terminal returns a delivery confirmation. Therefore, a method in which a physical line is simply set to a new cell and switched, such as circuit switching, cannot be adopted because it causes protocol mismatch. In order to implement handover in packet-switching-based mobile communication, it is necessary to take over the communication state before moving until the communication is restarted after moving. Inheriting the call status and the like inevitably complicates the handover procedure and lengthens the processing time. This can cause loss of data or disconnection by the no-response timer. In order to avoid this, temporary restriction processing of communication is necessary.

Further, even if a new communication link is set up, the packet from the partner terminal does not correctly reach the mobile terminal through the link. As described above, the protocol in which the packet network control procedure is added to X.25 is used between the packet switches, but the routing information used here needs to be changed. Further, when the handover is carried out over a plurality of packet switches, it is necessary to take over the information between the packet switches, and when it is carried over between the business operators, it is necessary to take over the information between the business operators. The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the above-mentioned problems in the related art and to realize a handover without loss of data during communication. It is to provide an interrupted handover method.

[0009]

The above objects of the present invention are as follows:
The steps of regulating communication during link switching by the packet switch, the steps of taking over the packet waiting for a response to the buffer of the link after switching and holding it, and preventing the loss of data by using the resend function of the packet protocol. It is characterized by having a step of setting up and releasing a link by taking over information of a link and a communication state in a switch or between packet switches, and a step of exchanging information with a location register for other mobile communication specific processing. It is achieved by a packet service uninterrupted handover method. More specifically, when both cells before and after the mobile data terminal moves are connected to the same packet switch, they are connected to different mobile communication base stations, and these mobile communication base stations use different packets. When connected to an exchange, when the movement of the cell crosses the mobile communication networks of different carriers, etc., each has its own additional steps.

[0010]

In the packet service uninterrupted handover method according to the present invention, a step of restricting communication during link switching in the packet switch under various conditions described above,
The step of preventing the loss of data by using the resending function of the packet protocol to take over the packet waiting for a response to the buffer of the link after switching and holding it, and the information on the link and communication status within the packet switch or between packet switches. Steps to take over and set and release the link,
With respect to other processing specific to mobile communication, the step of exchanging information with the location register allows handover to be realized without causing packet protocol mismatch even under a wide range of conditions and without losing packets.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a diagram showing a connection configuration for performing a handover based on a packet service uninterrupted handover method according to an embodiment of the invention described in claim 1. In the configuration shown in this embodiment, the packet terminal 5 and the mobile network 6 are
Subscriber-based packet switch that accommodates a network (shown as "PS" in the figure)
2, a relay network 3 for relaying between stations, and a location register (“L” in the figure) for controlling database processing of mobile communication.
R ”) 4 and a plurality of mobile communication switching stations (“ MS ”in the figure) connected to the packet network 1.
C) 7), a plurality of radio base stations (indicated as “BS” in the figure) under the control of each mobile communication switching center 7, and a location register (“LR” in the figure) that controls database processing of mobile communication. (Shown as ".").

The relay network 3 uses other than packet switching.
For example, a cell relay or the like may be used. The location registers 4 and 9 do not exist as physical nodes and may be logically defined or shared by a plurality of networks. The transmission network between the packet switches 2 and 7 and the location registers (LR) 4 and 9 or the location registers is not limited to a common line signaling network. In the embodiment shown in FIG. 1, the mobile data terminal 10 is a cell of a radio base station (BS) # 1n under the control of a mobile switching center (MSC) # 1 and a packet switch (PS).
While moving while performing data communication with the fixed packet terminal accommodated in # 0, the mobile communication switching center (M
The mobile base station (MSC) # 2, which is connected to the packet switch (PS) # 1 in the same manner as the SC) # 1, belongs to the radio base station (B).
S) It is assumed that it is necessary to switch the radio base station to the cell # 2m. FIG. 2 shows a communication sequence and an outline of processing of main nodes in this case.

In FIG. 2, the handover request signal output from the mobile data terminal 10 that knows that a handover is necessary due to a decrease in signal level is a destination radio base station.
(BS) # 2m, mobile switching center (MSC) # 2,
It is delivered to the packet switch (PS) # 1. Upon receiving this handover request signal, the packet switch (PS) # 1 immediately sends the unreceivable packet to the terminal (fixed packet terminal) of the communication partner. The partner terminal (fixed packet terminal) that receives the unreceivable packet stops the data packet transmission. Next, the mobile data terminal 10 requests the location register (LR) 9 to perform a database update process or the like associated with the handover. Then, if there is no problem, the link with the movement-destination wireless base station (BS) # 2m is set.

At this time, the state at the time of communication with the radio base station (BS) # 1n is taken over as it is to prevent the inconsistency in the protocol from occurring. After that, the call setting acceptance signal is transmitted to the mobile data terminal 10 via the destination wireless base station (BS) # 2m. When the new link can be set up, the link information transfer packet containing the information necessary for link re-setting is used to notify that the destination of the packet has been changed to the packet switch (PS) # 0 that accommodates the terminal of the communication partner. Notice. The packet switch (PS) # 0 changes the contents of the link memory based on the information of the link information transfer packet.
In the packet switch (PS) # 1 which has received the setting completion response from the packet switch (PS) # 0, the destination radio base station (B
S) A response (connection acceptance) signal is sent to # 2m, and a receivable packet is sent to the terminal of the communication partner to restart communication.

If, after the communication is resumed, normal delivery confirmation cannot be performed for the held response-waiting packet due to loss of the packet due to the handover process or the like,
Retransmission control is performed based on the protocol used. Finally, the disconnection signal is transmitted to the movement-destination radio base station (BS) # 1n, the link used before the movement is released, and the handover processing is completed. In the above description, the case where the mobile terminal communicates with one fixed terminal has been described as an example, but communication is possible even if a plurality of logical channels are set. That is, in this case, it can be realized by repeating the restriction process, the takeover process, and the like for the set number of logical channels.

Further, the terminal of the communication partner is not limited to a fixed terminal, but may be a mobile data terminal, and a packet terminal or a non-packet terminal connected to another packet network or telephone network via the gateway exchange. But it's okay. of course,
It goes without saying that it is not necessary to go through the relay network. As for the handover method, the new link method is given as an example here, but the old link method or the like may be used. FIG. 3 is a diagram showing a connection configuration for performing a handover based on a packet service uninterrupted handover method according to an embodiment of the present invention as set forth in claim 2. The operation will be described below, focusing on the difference from the embodiment described above.

In this embodiment, a mobile switching center (MSC) #
1 and the same (MSC) # 2 are different packet switches.
The mobile data terminal 10 is connected to the (PS) # 1 and the (PS) # 2, and the mobile communication terminal switches from the cell of the radio base station (BS) # 1n under the control of the mobile communication switching center (MSC) # 1. Station (MS
C) It is assumed that the mobile station moves to a cell of a radio base station (BS) # 2m under # 2. In FIG. 4, the handover request signal transmitted from the mobile data terminal 10 includes a destination wireless base station (BS) # 2m and a mobile communication switching center (MSC) # 2.
Then, it is delivered to the packet switch (PS) # 2. Packet Switch (PS) # that received this handover request signal
2 requests the location register (LR) 9 for processing such as location registration.

In the location register (LR) 9, the source packet switch (PS) # 1 is determined, and the packet switch (PS) # 1 is handed over to the packet switch (PS) # 2. , Notify with required information. The packet switch (PS) # 1 that has received the notification immediately sends out the unreceivable packet to the terminal of the communication partner, and also sends the packet switch (PS) # 2 to the packet switch (PS) # 2 for the state of communication, billing information, and a packet waiting for response Transfer in a call information transfer packet. The packet switch (PS) # 2 sets a new link based on the information of the call information transfer packet. The following is basically the same as that of FIG. 2 except that the packet switch (PS) # 2 is instructed to release the old link from the packet switch (PS) # 1.

FIG. 5 is a diagram showing a connection configuration for performing handover based on the packet service uninterrupted handover method according to an embodiment of the present invention as set forth in claim 3 or 4. Focusing on the difference from the above-described embodiment, the main points of the operation will be described below. The handover from the radio base station (BS) # 1n to the radio base station (BS) # 2m is shown in FIG. 6, and the handover from the radio base station (BS) # 2m to the radio base station (BS) # 3p is shown in FIG. The idea is the same as in the case, and as for the sequence, basically, FIGS. 2 and 4 can be used, respectively. However, the difference lies in that necessary information, such as subscriber information and billing information, is added between the location registers because the information is spread among the businesses.

According to the handover method shown in each of the above-mentioned embodiments, the user who is performing data communication with the mobile data terminal can change the communication area without unavoidably losing the communication or losing the data. . This means that when both cells before and after the mobile data terminal moves are connected to the same packet switch, they are connected to different mobile communication base stations, and these mobile communication base stations are connected to different packet switches. In this case, when the movement of the cell is across the mobile communication networks of different operators, etc., it is applicable respectively. It is needless to say that each of the above-mentioned embodiments shows an example of the present invention, and the present invention should not be limited to these.

[0021]

As described above in detail, according to the present invention, it is possible to realize a handover without a loss of data during communication and to realize a packet service uninterrupted handover method. Is.

[Brief description of drawings]

FIG. 1 is a diagram showing a connection configuration for performing a handover based on a packet service uninterrupted handover method according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a communication sequence according to the embodiment shown in FIG.

FIG. 3 is a diagram showing a connection configuration for performing a handover based on a packet service uninterrupted handover method according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a communication sequence according to the embodiment shown in FIG.

FIG. 5 is a diagram showing a connection configuration for performing a handover based on a packet service uninterrupted handover method according to a third embodiment of the present invention.

FIG. 6 is a diagram showing a structure of an ISDN packet network.

FIG. 7 is a diagram showing an example of a ISDN packet communication sequence.

FIG. 8 is a diagram showing a network configuration example of a second-generation cordless phone system (PHS).

9 is a diagram showing an example of a conventional handover sequence in the system shown in FIG.

[Explanation of symbols]

 1 Packet Network 2 Subscriber Packet Switch (PS) 3 Relay Network 4 Location Register (LR) 5 Packet Terminal 6 Mobile Network 7 Mobile Communication Switching Center (MSC) 8 Radio Base Station (BS) 9 Location Register (LR) 10 Mobile Data terminal

Claims (4)

[Claims] 1. A mobile data terminal, which is communicating through the packet switching network in a wireless communication unit area (cell) within the mobile communication network connectable to the packet switching network, moves to another adjacent cell. In this case, the mobile switching center having the source cell as a subordinate and the mobile switching center having the destination cell as a subordinate are different, and both mobile switching centers are connected to the same packet switch. (1) When the packet switch receives the handover request signal transmitted from the mobile data terminal, the packet switch sends a layer 3 unreceivable packet to the data terminal that is the communication partner of the mobile data terminal. The first step of transmitting and putting the communication in a restricted state; (2) The packet switch performs database registration (location registration, authentication, subscriber data management, etc.) of the mobile data terminal. (2) requesting the processing unit to update the information associated with the handover and confirming the normality, and receiving the response, and (3) the packet switch holds it based on the protocol regulation. For a response-waiting packet whose delivery to the mobile data terminal is unconfirmed, if delivery confirmation is not obtained after the communication is restarted, the packet is retransmitted according to the specified retransmission procedure, so it corresponds to the communication link used before the handover. A third step of taking over the contents of the retransmission buffer to a retransmission buffer corresponding to a link newly set between the packet switch and the destination cell and holding the same, (4) the mobile data terminal The layer 2 and layer 3 call states in the source cell of the above are continued even in the link newly set up between the packet switch and the destination cell. Order to,
A fourth step of taking over the call information in the packet switch, and (5) the packet data exchange, after performing a new link setting process with the target cell based on the taken over call information, the mobile data terminal. A fifth step of transmitting a call setting acceptance signal to the packet switch, and (6) the packet switch,
A sixth step of notifying the packet switch accommodating the data terminal of the communication partner of new link information by a link information transfer packet, and (7) the packet switch accommodating the data terminal of the communication partner, A seventh step of transmitting a response packet to the link information transfer packet to the packet switch after changing call information for controlling the destination of the packet based on the link information of the link information transfer packet; After receiving the response packet to the link information transfer packet, the packet switch transmits a response signal to the handover request signal transmitted from the mobile data terminal, while the data terminal of the communication partner can receive Layer 3 reception. An eighth step of transmitting a packet to release the restricted state of the communication and restart the communication. And (9) after the communication is resumed, if normal delivery confirmation for the response waiting packet held by the packet switch cannot be confirmed, the packet is retransmitted according to a retransmission procedure defined by the protocol. And (10) a tenth step of releasing the link used by the packet switch before moving, the packet service uninterrupted handover method. 2. A case where a mobile data terminal communicating in a cell in a mobile communication network connectable to a packet switching network moves to another adjacent cell, A packet switching system in which the source communication switching center having the original cell as a subordinate and the destination communication switching center having the destination cell as a subordinate are different, and the source communication switching center and the destination communication switching center are different When the mobile data terminal is connected, (1) a packet switch (destination packet switch) connected to the destination communication switching center receives the handover request signal transmitted from the mobile data terminal as a trigger. The first step of requesting the location register, which performs location registration, authentication, subscriber data management, etc., to update information and confirm normality associated with handover, and (2) the location After the register performs the processing associated with the handover, it determines the packet switch (source packet switch) connected to the source communication switching center based on the location registration information managed by itself, and the source packet A second step of transmitting necessary information and a signal for instructing a handover process to the exchange, and (3) the source packet switch has a layer 3 for a data terminal which is a communication partner of the mobile data terminal. After receiving the unreceivable packet of the above, and putting the communication in the restricted state, a response signal to the signal instructing the handover processing is transmitted to the location register, and the layer 2 with the mobile data terminal in the source cell and A response waiting packet whose layer 3 call status, billing information and delivery to the mobile data terminal have not been confirmed is transferred to the destination packet exchange. The third step of transferring to the destination packet switch by a call information transfer packet to continue in the link newly set up with the destination cell by the switchboard, and (4) the destination packet switch, From the location register,
After receiving a response signal to the processing request associated with the handover, transmitting a response signal to the call information transfer packet received from the source packet switch, and transmitting the response signal to the destination cell based on the call information inherited from the call information transfer packet. A fourth step of transmitting a call setup acceptance signal to the mobile data terminal after performing a new link setup process between the mobile data terminal and the destination packet switch, and (5) the destination packet switch A fifth step is to notify a packet switch accommodating the data terminal of the communication partner of new link information by a link information transfer packet.
And (6) the packet switch that accommodates the data terminal of the communication partner changes the call information that controls the destination of the packet based on the link information of the link information transfer packet, and then the destination packet switch. And a sixth step of transmitting a response packet to the link information transfer packet, and (7) the destination packet switch is transmitted from the mobile data terminal after receiving the response packet to the link information transfer packet. A response signal to the handover request signal is transmitted, while a layer 3 receivable packet is transmitted to the data terminal of the communication partner, and the communication is resumed by releasing the restricted state of the communication. Seventh step, (8)
After the communication is restarted, if normal delivery confirmation for the response waiting packet held by the destination packet switch cannot be confirmed, an eighth step of retransmitting the packet according to a retransmission procedure defined by a protocol, (9) The source packet exchange releases the link used before the movement with the mobile data terminal upon receiving the handover completion notification packet transmitted from the destination packet exchange. And a packet service non-disruptive handover method. 3. A mobile data terminal, which is communicating through a packet switching network in a cell in a mobile communication network connectable to the packet switching network, moves to another adjacent cell. The operator of the mobile communication network that owns the original cell and the operator of the mobile communication network that owns the destination cell are different, and the mobile switching center to which both cells belong is connected to the same packet switch. (1) When the packet switch receives the handover request signal transmitted from the mobile data terminal as a trigger, the packet switch cannot receive the layer 3 unreceivable packet for the data terminal that is a communication partner of the mobile data terminal. And (2) the packet switch performs database registration (location registration, authentication, subscriber data management, etc.) of the mobile data terminal. (2) requesting the update process of information associated with the handover and confirmation of normality, and (3) the location register receiving the request for the process associated with the handover, By communicating with the location register that the network has individually or jointly, it is judged whether the interconnection condition between each operator and the contract condition of the subscriber allow the handover, and the result and the processing accompanying the handover. The third step of notifying the packet switch of the response to the request of (4), and (4) the communication waiting for the response-waiting packet which is not confirmed to be delivered to the mobile data terminal held by the packet switch based on the protocol regulation. If the delivery confirmation is not obtained after resuming of A fourth step of taking over the contents of the retransmission buffer corresponding to the existing communication link to the retransmission buffer corresponding to the link newly set between the packet switch and the destination cell and holding the same.
And (5) in order to continue the call states of Layer 2 and Layer 3 in the source cell of the mobile data terminal even in the link newly set up between the packet switch and the destination cell, The fifth step of taking over the call information at the packet switch, and (6) the mobile data terminal after the packet switch performs a new link setting process with the target cell based on the taken over call information. A sixth step of transmitting a call setting acceptance signal to
(7) A seventh step in which the packet switch notifies the packet switch accommodating the data terminal of the communication partner of new link information by a link information transfer packet, and (8) the data terminal of the communication partner. A packet switch which accommodates the packet information, changes call information for controlling the destination of the packet based on the link information of the link information transfer packet, and then transmits a response packet for the link information transfer packet to the packet switch. And (9) the packet switch transmits a response signal to the handover request signal transmitted from the mobile data terminal after receiving the response packet to the link information transfer packet, while the data of the communication partner is transmitted. A layer 3 receivable packet is sent to the terminal to release the restricted state of the communication. The ninth step of restarting the communication, and (10) if the normal delivery confirmation for the response waiting packet held by the packet switch cannot be performed after the communication is restarted, follow the retransmission procedure specified by the protocol. Tenth step of retransmitting the packet, and (11) information necessary for performing integrated charging processing between the packet switches, between the packet switches and the location registers, or between the location registers. And a packet service non-interruption handover method comprising: (12) a twelfth step of releasing the link used by the packet switch before moving. 4. A mobile data terminal, which is communicating through a packet communication network in a mobile communication network connectable to the packet switching network, moves to another cell adjacent to the mobile data terminal. The operator of the mobile communication network having the original cell as a subordinate and the operator of the mobile communication network having the destination cell as a subordinate are different from each other, and the source communication switching center to which the source cell belongs and the destination When the destination communication switching center to which the cell belongs is connected to a different packet switching center, (1) the packet switching center (destination packet switching center) connected to the destination communication switching center is transmitted from the mobile data terminal. Upon receipt of the handover request signal, the location register that performs location registration, authentication, subscriber data management, etc. of the mobile data terminal is updated with information related to the handover and the normality is confirmed. A first step of Lai, (2)
The location register, which has received the request for the processing associated with the handover, communicates with the location register which each of the mobile communication networks has individually or jointly, so that the interconnection condition between the operators and the contract condition of the subscriber are handed over. The second step of determining whether or not to permit the result and notifying the result to the destination packet switch, and (3) the location register which the location register manages after performing the processing associated with the handover. A packet switch (a source packet switch) connected to the source communication switching center based on registration information, and transmitting necessary information and a signal instructing a handover process to the source packet switch 3), and (4) the source packet switch layer is provided to a data terminal that is a communication partner of the mobile data terminal. And of sending a Not Ready packet,
After setting the communication in the restricted state, a response signal to the signal instructing the handover process is transmitted to the location register, and the call state of the layer 2 and layer 3 with the mobile data terminal in the source cell and the charging information And, the response waiting packet whose delivery to the mobile data terminal is unconfirmed is continued even in the link newly set with the destination cell in the destination packet switch,
A fourth step of transferring to the destination packet switch by a call information transfer packet, and (5) the destination packet switch receives the response signal to the processing request accompanying the handover from the location register, A response signal to the call information transfer packet received from the packet switch is transmitted, and a new link is set up between the mobile data terminal and the destination packet switch in the target cell based on the call information inherited from the call information transfer packet. A fifth step of transmitting a call setting acceptance signal to the mobile data terminal after processing, and (6) the destination packet switch to the packet switch containing the data terminal of the communication partner. A sixth step of notifying new link information by a link information transfer packet,
(7) After the packet switch that accommodates the data terminal of the communication partner changes call information that controls the destination of the packet based on the link information of the link information transfer packet, A seventh step of transmitting a response packet to the link information transfer packet, and (8) the handover request signal transmitted from the mobile data terminal after the destination packet switch receives the response packet to the link information transfer packet. And a response enable packet of layer 3 is transmitted to the data terminal of the communication partner, and the communication is resumed by releasing the restricted state of the communication. Step, and (9) for the response waiting packet held in the destination packet switch after the communication is restarted. If normal delivery confirmation is not possible, a ninth step of retransmitting the packet according to a retransmission procedure specified by the protocol, (10) between the packet switches, between the packet switches and the location register, or A tenth step of communicating information necessary for performing integrated charging processing between the location registers, and (11) the handover source notification packet transmitted from the destination packet switch by the source packet switch. And an eleventh step of releasing the link used before the movement with the mobile data terminal upon reception of the packet service uninterrupted handover method.