JP2002368778A - Communication terminal and method for reconnecting communication terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for reconnecting a communication terminal by which data can be immediately transmitted/received when the connection of the communication terminal is temporarily interrupted by a hand-over and the connection is recovered thereafter by reducing the amount of TCP(Transmission Control Protocol) processing requiring a very long processing time to the utmost. SOLUTION: In the method for reconnecting the communication terminal which can perform data communication by the TCP/IP connection, the line connection and a PPP(Point-To-Point Protocol) connection are disconnected when the communication is temporarily interrupted. An IP address used at present is stored, and the TCP connection is maintained. When the communication system recovers from the interruption, the line connection and the PPP connection are connected, an IP address obtained by the PPP connection after communication system recovers from the interruption is compared with the IP address before the communication is temporarily interrupted, and the TCP connection used before the communication is temporarily interrupted is used again when both IP addresses are discriminated identical to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reconnection method when a communication terminal is temporarily disconnected, and a communication terminal using such a reconnection method. More specifically, when reconnection is performed after a temporary disconnection, after the line connection and the PPP connection are connected, the P
When the IP address obtained by the PP protocol processing is the same as the IP address immediately before the temporary disconnection, the previous TCP connection is used to reconnect the communication terminal that does not establish a new TCP connection, and the like. The present invention relates to a communication terminal using a simple reconnection method.

[0002]

2. Description of the Related Art The present invention relates to a reconnection method when a communication terminal is temporarily disconnected. As an example, a handover of the communication terminal will be described below as an example.

FIG. 4 is a diagram for explaining handover of a communication terminal (here, a portable telephone). In FIG. 4, when the communication terminal 22 moves from the cell 20 to the cell 23 through the boundary between the cells while the base station 21 in the cell 20 is communicating with the communication terminal 22, the communication terminal 22
Is disconnected from the base station 21 and is newly reconnected to the base station 24.

FIG. 5 is a diagram showing disconnection and reconnection processing of a communication terminal when the communication terminal moves between cells. In FIG. 5, it is assumed that the base station 21 and the communication terminal 22 are in communication at first. As the communication terminal 22 approaches the cell boundary, the electric field strength received from the base station 21 decreases. When the communication terminal 22 enters this state, the base station 21
Since the base station 24 having a higher electric field strength than the electric field strength is searched for, the base station 24 is acquired thereafter. Next, when the communication terminal 22 moves to the cell 23, the electric field intensity from the base station 21 further decreases, and the communication with the base station 21 is cut off. Next, reconnection processing with the base station 24 is performed, the communication terminal 22 is connected to the base station 24, and communication with the base station 24 is resumed.

FIG. 6 is a diagram showing a configuration of a conventional communication system for disconnecting a communication terminal from a server. In FIG. 6, the communication system includes a communication terminal 1, an exchange 2,
It comprises an authentication server 3, a gateway 4, a communication network 5, and a server 6.

Next, the operation of this communication system will be described using an example in which the communication application 11 (for example, mail software) in the communication terminal 1 downloads mail from the server 6 in this communication system.
When the communication application 11 is started, the line connection protocol 14 establishes a line connection with the exchange 2, and thereafter, the PPP protocol 13 acquires an IP address from the authentication server 3, and then, based on the IP address,
TCP / IP protocol 12 communicates with server 6 via TCP.
Build a connection and then the communication application 11
Transmits and receives data to and from the server 6.

[0007] When the communication terminal 1 and the server 6 are connected as described above, for example, it is assumed that the communication terminal 1 is temporarily disconnected from the call. At this time, in the communication system, since the line connection protocol 14 is disconnected,
The upper layer PPP connection and TCP connection are all disconnected.

At this time, when the temporary disconnection of the communication terminal 1 is recovered, the communication terminal 1
4 and the PPP protocol 13 and TC
The P / IP protocol 12 needed to reconnect the PPP connection and the TCP connection, respectively.

FIG. 7 is a flowchart showing connection, disconnection, and reconnection between the communication terminal 1 and the server 6 in the conventional communication system. The connection, disconnection, and reconnection of the communication terminal 1 and the server 6 will be described in more detail with reference to FIG. In FIG. 7, when the communication terminal 1 issues a line connection request from the communication application 11 in step S21, the line connection protocol 14 establishes a line connection with the exchange 2 in step S22, and the PPP protocol 13 An IP address is obtained from the server 3. In step S23, based on the IP address, the TCP / IP protocol 12 establishes a TCP connection with the server 6 via the exchange 2, the authentication server 3, the gateway 4, and the communication network 5, and in step S2
In 4, the communication application 11 sends and receives data to and from the server 6.

Next, it is assumed that a temporary disconnection of communication has occurred in step S25. In this case, step S26
In, the line and the PPP connection are disconnected,
In step S27, the TCP connection is disconnected. The TCP disconnection processing time takes about 1.5 seconds as described later.

Next, in step S28, when the recovery from the temporary disconnection is confirmed, in step S29, the line connection protocol 14 makes a line connection and the PPP protocol 13
Performs a PPP connection with the authentication server 3, and the TCP / IP protocol 12 reestablishes a TCP connection with the server 6 in step S30. In step S31, the communication application 11 transmits and receives data to and from the server 6.

FIG. 8 is a diagram showing control signals when a TCP connection is established and disconnected in a communication system. FIG. 8 (a) shows that the communication terminal 1
It is a figure which shows the control signal at the time of establishing a P connection. FIG. 8 (b) shows that the communication terminal 1
It is a figure which shows the control signal when disconnecting a CP connection. This is called a three-way handshake.

In FIG. 8A, the TCP of the communication terminal 1
The / IP protocol 12 transmits a SYN signal to the server 6 when making a connection with the server 6, and the server 6
The signal is transmitted to the TCP / IP protocol 12 of the communication terminal 1. On the other hand, the TCP / IP protocol 12 transmits an ACK signal to the server 6, and the TCP connection connection processing ends. TC in the TCP / IP protocol 12
The P connection connection process takes about 500 ms to about 1 second.

On the other hand, in FIG. 8B, the TCP / IP protocol 12 of the communication terminal 1 transmits a FIN signal to the server 6 when disconnecting the TCP connection with the server 6, and the server 6 transmits an ACK signal. TCP / of communication terminal 1
Sent to IP protocol 12. Further, the server 6
Sends the FIN signal to the TCP / IP protocol 12 of the communication terminal 1.
, And the TCP / IP protocol 12 transmits an ACK signal to the server 6, and the TCP connection disconnection process ends. The TCP cell disconnection process in the TCP / IP protocol takes about 1.5 to 2 seconds.

[0015]

As described above, in the conventional communication system, there is a problem that the total processing time of the disconnection processing and the connection processing of the TCP connection takes a long time of about 2 to 3 seconds. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to minimize TCP processing requiring an extremely long processing time as described above.
In the PPP protocol processing after the temporary disconnection, if the IP address acquired by the communication terminal 1 from the authentication server 3 is the same as the IP address acquired from the authentication server 3 before the temporary disconnection, the TCP connection disconnection processing And a method of reconnecting a communication terminal so as not to perform reconnection processing of a TCP connection.

[0017]

In order to achieve the above object, the present invention relates to a method for reconnecting a communication terminal capable of performing data communication by TCP / IP connection, the method comprising the steps of: PPP to disconnect the connection
A disconnection step, an IP address storage step for storing the currently used IP address, and a TCP holding step for holding a TCP connection, and a PPP for reconnecting the PPP connection when communication is restored
A reconnection step, a comparison step of comparing whether an IP address obtained in the PPP reconnection step is the same as the IP address stored in the IP address storage step, and a step of comparing the PPP connection in the comparison step. A comparing step of comparing whether the IP address obtained in the step is the same as the IP address stored in the IP address storing step,
If it is determined that they are the same, a TCP reusing step of reusing the TCP connection held in the TCP holding step is provided.

Further, the present invention further comprises the step of, if it is determined in the comparing step that the IP address obtained in the PPP reconnecting step is not the same as the IP address stored in the IP address storing step, , T held in the TCP holding step
A TCP disconnection step of disconnecting the CP connection and a TCP reestablishment step of establishing a TCP connection again based on the IP address obtained in the PPP reconnection step.

[0019]

FIG. 1 is a diagram showing a configuration of a communication system in which a communication terminal and a server according to an embodiment of the present invention are connected. The system configuration shown in FIG. 1 is the same as that of FIG. 6 except that the connection between the communication application 11 and the TCP / IP protocol 12 is disconnected, as compared with FIG. A detailed description of the configuration of No. 1 is omitted.

FIG. 2 is a flowchart showing connection, disconnection, and reconnection between the communication terminal 1 and the server 6 in the communication system according to the embodiment of the present invention. In FIG.
When the communication terminal 1 generates a line connection request from the communication application 11 in step S1, the communication terminal 1 executes step S1.
In 2, the line connection protocol 14 establishes a line connection with the exchange 2, and the PPP protocol 13 acquires an IP address from the authentication server 3. In step S3, the TCP / IP protocol 12 establishes a TCP connection with the server 6 via the exchange 2, the authentication server 3, the gateway 4, and the communication network 5 based on the IP address. The communication application 11 transmits and receives data to and from the server 6.

Next, assuming that a temporary disconnection of communication has occurred in step S5, the line and the PPP connection are disconnected in step S6. In step S7, the TCP cell is held. In FIG. 2, step S in the conventional flowchart shown in FIG.
There is no disconnection of the TCP connection corresponding to No. 27, and at this point, the TCP cell is held. For this reason, about 1.
5 seconds are not required.

Next, when the recovery from the temporary disconnection is confirmed in step S8, the communication terminal 1 establishes a line connection in step S9, and the PPP protocol 13 establishes a connection with the authentication server 3 in step S9. Make a PPP connection. In step S10, the communication terminal 1 confirms that the IP address acquired from the authentication server 3 by the PPP connection is
It is determined whether the IP address is the same as the IP address acquired in step S2. If the IP address is the same, data is transmitted to and received from the server 6 in step S13 without reconnecting the TCP connection. On the other hand, if the IP address is not the same as the address obtained in step S2 in step S10, the previous TCP connection is disconnected in step S11, and the TCP cell is reconnected in step S12. Send and receive data to and from

Thus, the PP after the temporary disconnection is recovered
When the IP address obtained from the authentication server 3 by the P connection is the same as the IP address obtained in step S2, the previously connected TCP connection is used without disconnecting and reconnecting the TCP connection. As a result, the reconnection time can be shortened by about 2 to 3 seconds as a whole.

FIG. 3 is a diagram showing a configuration of a communication terminal for performing reconnection according to the present invention. In FIG. 3, digital voice data received from a communication destination is transmitted to a communication circuit 34. The communication circuit 34 demodulates and decodes the audio data transmitted from the antenna 33 and sends it to the A / D / D / A converter 37. The A / D / D / A converter 37 The received digital voice data is converted into analog data and sent to the speaker 36. The speaker 36 is
Outputs audio data audibly. These operations are C
It is executed according to the instruction of PU46.

On the other hand, the audio data input from the microphone 35 is converted into digital data by the A / D / D / A converter 37 and sent to the communication circuit 34. The communication circuit 34 encodes the digital audio data transmitted from the microphone 35, modulates the digital audio data into a corresponding frequency, and transmits the modulated data to the communication destination via the antenna 33.

Next, the configuration of each part of the communication terminal will be described. The RAM 38 stores data such as telephone directory data and mail. Further, an IP address obtained when reconnecting during data communication is temporarily stored. Also, RO
The M39 stores an execution program for operating the CPU 46, a program according to a communication method (for TDMA, time slot control, etc.), and various execution programs such as handoff.

The operation unit 40 has ten keys for inputting a telephone number, a mail address, a text, etc., a transmission key, an end key, and the like.
Notify U46. The display control unit 41 includes a driver or the like necessary to display various data, and converts the data into a form that can be displayed on the display unit 42. Display section 42
Is composed of, for example, an LCD and displays various data.

The IP address comparison circuit 43 compares the IP address stored in the IP address storage unit 44 with the acquired IP address to determine whether the IP address is the same, and notifies the CPU 46 of the result. This will be described later in detail.
The IP address storage unit 44 stores the IP address obtained from the authentication server 3 by the PPP protocol 13 shown in FIG. The CPU 46 controls the entire configuration described above.

Next, a case where mail is transmitted using the above-described communication terminal will be described. Of course, data communication like the Internet is possible as well. First,
A mail document is created by the operation unit 40. The created mail is temporarily stored in the RAM 38. After that, when a transmission key (not shown) of the operation unit 40 is operated,
The CPU 46 controls the communication circuit 3 based on the program stored in the ROM 39 according to the flowchart of FIG.
4 is controlled. That is, the communication circuit 34 connects the mail server to the telephone line based on the line connection protocol 14. At this time, the communication circuit 34 is provided with a circuit for measuring the received electric field strength, and the communication terminal 1 is connected to the base station having the highest received electric field strength level by the line connection protocol 14.

Thereafter, the communication circuit 34 similarly establishes a PPP connection with the authentication server 3 according to the protocol of the upper layer, and acquires an IP address for communicating with the mail server 6. This IP address is
The data is sent to the IP address storage unit 44 via the data line 32 and stored there. Using this IP address,
The TCP / IP protocol 12 establishes a TCP connection with the mail server 6 and transmits mail data (text) stored in the RAM 38.

Here, when the received electric field strength level decreases, the communication terminal 1 is temporarily disconnected (here, for example,
(Handoff) operation. The handoff operation program is stored in the ROM 39, and the handoff is performed according to this program. That is, the communication terminal 1 disconnects the telephone line and the PPP connection with the base station that has been connected up to now. At this time, the CPU 46 instructs the communication circuit 34 to hold the TCP connection and instruct the telephone circuit connection and the PPP connection to be established again. The communication circuit 34
In accordance with the instruction from the PU 46, the telephone line connection and the PPP connection are attempted again while holding the TCP connection.

The line connection protocol 14 connects a line with the exchange 2, and then the PPP protocol 13 establishes a PPP connection with the authentication server 3 and acquires a new IP address again. When the new IP address is obtained, the CPU 46 sends the new IP address to the IP address comparison circuit 43. On the other hand, CPU4
6 reads out the IP address used before the handoff stored in the IP address storage unit and sends it to the IP address comparison circuit 43. IP address comparison circuit 43
Compares the two transmitted IP addresses to check whether they are the same, and notifies the CPU 46 of the result. If the result sent from the comparison circuit 43 is the same, the CPU 46 uses the previous IP address stored in the IP address storage unit 44 and re-uses the held TCP connection. The communication circuit 34 and the IP address storage unit 44 are controlled to execute data communication. On the other hand, if the two IP addresses are not the same, the CPU 46 stores the new IP address temporarily stored in the RAM 38 in the IP address storage unit 4.
The CPU 38 controls the RAM 38 and the IP address storage unit 44 so as to overwrite the IP address of the RAM 38. In this case, the TCP connection held for the communication circuit 34 is disconnected, and the
Instructs to establish a P connection.

In the present specification, the present invention relates to a method for reconnecting when a communication terminal is temporarily disconnected, not only in the case of hand-off of a wireless cellular phone, but also in the case of using a wired line. It can be applied to the existing TCP / IP connection. For example, when the Internet is performed on a personal computer (PC) at home, the connection may be momentarily interrupted depending on the state of the line.

[0034]

As described above, according to the present invention,
When the communication terminal 1 is temporarily disconnected, the TCP connection is suspended, and when the line is recovered after a short time, only the line connection and the PPP connection are connected, and the TCP connection is not reconnected. Things. This eliminates the need to disconnect and connect the TCP connection, which requires a long time, so that the communication terminal 1 can receive data as soon as the line is restored.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a communication system in which a communication terminal and a server according to an embodiment of the present invention are connected.

FIG. 2 is a flowchart showing connection, disconnection, and reconnection of a communication terminal and a server in the communication system according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration of a communication terminal that performs reconnection according to the present invention.

FIG. 4 is a diagram illustrating handover of a communication terminal.

FIG. 5 is a diagram illustrating disconnection and reconnection processing of a communication terminal when the communication terminal moves between cells.

FIG. 6 is a diagram illustrating a configuration of a conventional communication system that disconnects a connection between a communication terminal and a server.

FIG. 7 is a flowchart showing connection, disconnection, and reconnection of a communication terminal and a server in a conventional communication system.

FIG. 8 is a diagram illustrating control signals when a TCP connection is connected and disconnected in a communication system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Communication terminal 2 ... Exchanger 3 ... Authentication server 4 ... Gateway 5 ... Communication network 6 ... Server 11 ... Communication application 12 ... TCP / IP protocol 13 ...・ PPP protocol 14 ・ ・ ・ Line connection protocol 34 ・ ・ ・ Communication circuit 38 ・ ・ ・ RAM 39 ・ ・ ・ ROM 43 ・ ・ ・ IP address comparison circuit 44 ・ ・ ・ IP address storage unit

Claims (4)

[Claims] 1. A method for reconnecting a communication terminal capable of performing data communication through a TCP / IP connection, wherein the PPP connection is disconnected when the communication is temporarily disconnected.
A disconnection step, an IP address storage step for storing the currently used IP address, and a TCP holding step for holding a TCP connection, and a PPP for reconnecting the PPP connection when communication is restored
A reconnection step, a comparison step of comparing whether an IP address obtained in the PPP reconnection step is the same as the IP address stored in the IP address storage step, and a step of comparing the PPP connection in the comparison step. A comparing step of comparing whether the IP address obtained in the step is the same as the IP address stored in the IP address storing step,
A TCP reuse step of reusing the TCP connection held in the TCP holding step when it is determined that they are the same, a communication terminal reconnection method. 2. In the comparing step, the PPP
If it is determined that the IP address obtained in the reconnecting step is not the same as the IP address stored in the IP address storing step, the TCP further disconnects the TCP connection held in the TCP holding step. A disconnection step and a re-execution of T based on the IP address obtained by the PPP reconnection step
2. The method according to claim 1, further comprising a TCP reestablishment step of establishing a CP connection. 3. A communication terminal capable of data communication through a TCP / IP connection, a PPP disconnection means for disconnecting the PPP connection when the communication is temporarily disconnected,
An IP address storage unit for storing an IP address currently used, a TCP holding unit for holding a TCP connection, and a PPP reconnecting unit for reconnecting the PPP connection when the disconnection of the communication is restored; PPP
The IP address obtained by the reconnection means is
Comparing means for comparing whether or not the IP address is the same as the IP address stored by the address storing means; and in the comparing means, the IP address obtained by the PPP reconnecting means is stored in the IP address stored by the IP address storing means.
It has a comparing means for comparing whether or not it is the same as the P address, and a TCP reusing means for reusing the TCP connection held by the TCP holding means when it is determined that the P address is the same. Communication terminal. 4. If the comparing means determines that the IP address obtained by the PPP reconnecting means is not the same as the IP address stored by the IP address storing means, the TCP further comprises TC for disconnecting the TCP connection held by the holding means
4. The communication terminal according to claim 3, further comprising: P disconnection means; and TCP reconstructing means for reconstructing a TCP connection based on the IP address obtained by said PPP reconnecting means.