JP5020470B2 - Wireless communication terminal device and program thereof - Google Patents

Description

  The present invention relates to a wireless communication terminal apparatus, and more particularly to a technology for improving data communication speed when switching communication methods.

  As a wireless communication terminal that can operate simultaneously in a plurality of wireless modes and switches between two or more communication systems to communicate with a base station, a CDMA2000 1x (hereinafter referred to as “1x”) type mobile phone network, CDMA 2. Description of the Related Art There has been known a communication that switches between 1xEV-DO (1x Evolution Data Only; hereinafter referred to as “EV-DO”) type high-speed data communication network.

  The maximum throughput in the downlink (from the base station to the terminal) in the 1x system is 144 Kbps, and the maximum throughput in the EV-DO system is 2.4 Mbps. In the 1x / EV-DO hybrid system, the data communication can be continued by switching from the EV-DO method to the 1x method (hand-down), but hand-down during high-speed EV-DO data communication is possible. If this happens, a large packet loss will occur. This is because when the network communication path is switched at the time of hand-down, the terminal moves from the area of the base station that relays the packet, and the destination of the data transmitted before switching is lost. In addition, congestion is caused by switching from a high-speed transmission path to a low-speed transmission path.

  FIG. 13 is a sequence diagram of a conventional hand-down process.

  A wireless communication terminal (AT) communicates with an EV-DO wireless base station (AN) by the EV-DO method. At this time, if the communication quality between the wireless communication terminal (AT) and the wireless base station (AN) deteriorates, the wireless communication terminal (AT) transmits a DRC NULL Cover signal and stops transmitting data from the base station. Let Thereafter, the wireless communication terminal (AT) transmits a Connection Close signal, and stops communication with the EV-DO wireless base station (AN) by the EV-DO method.

Thereafter, the wireless communication terminal (AT) establishes a connection with the 1x wireless base station (BS). Thereafter, the radio communication terminal (AT) establishes a PPP session with the radio base station (BS). Then, the wireless communication terminal (AT) starts 1x communication with the 1x wireless base station (BS).
3GPP2 C.S0024 Ver4.0 "CDMA2000 High Rate Packet Data Air Interface Specification"

  However, in the conventional process of handing down from a system having a high maximum throughput to a system having a lower maximum throughput than the system, in order to prevent packet loss and congestion due to a difference in transfer speed, a buffer for each node on the transmission path is used. A lot of memory had to be provided, which was wasteful.

  In addition, even if hand-down is performed, unnecessary data continues to flow in the system before the hand-down, resulting in a problem that the system efficiency is very poor.

  Furthermore, if congestion occurs when data transfer using TCP is performed, the window size cwnd is set to one segment as an initial state, and transmission starts with one packet. As described above, there is a problem that it takes time to increase the transfer speed because the slow start that increases the number of transmitted packets one packet at a time and the high-speed retransfer that sets the window size cwnd to half work.

  The present invention temporarily stops received data by changing the TCP window size of downlink data and notifying from the terminal at the time of handdown. It is another object of the present invention to prevent lost packets, congestion, and unnecessary data transmission by returning the TCP window size to the original after the hand-down is completed.

When the wireless communication terminal of the first invention performs data communication via a wireless unit capable of data communication via a plurality of wireless communication systems and one system among the plurality of wireless communication systems, When switching from the system to a system with a lower maximum throughput than the system, the server can continuously transmit data before the wireless communication terminal stops transmitting data from the base station of the system performing the data communication. And a control unit that transmits a signal for reducing the amount of data.

In a second aspect based on the first aspect, the control unit temporarily stores data transmitted from the transmission side in order to reduce the amount of data that can be transmitted continuously by the server. It is characterized in that the value indicating is changed and transmitted.

According to a third invention, in the second invention, a value indicating a capacity for temporarily storing data sent from the server is changed to zero.

According to a fourth invention, in the second invention, when the switching of the system is completed, the value indicating the capacity for temporarily storing the data sent from the server is changed to the maximum value. Features.

In a fifth aspect based on the second aspect, the control unit actually transmits when changing the value indicating the capacity for temporarily storing the data transmitted from the server and transmitting the changed value. A value indicating a capacity for temporarily storing data transmitted from the server to be stored is stored, and when the system switching is completed, the data transmitted from the server is temporarily stored. A value indicating a capacity to be stored is changed to the stored value.

According to a sixth aspect of the invention, there is provided a program for performing data communication via one system among the plurality of wireless communication systems to an information terminal to which a plurality of wireless communication terminals capable of data communication via a wireless communication system can be connected. when you are, when switching from the system to a low system of maximum throughput than the system, before the transmission of data from the base station system is performing the data communication is the wireless communication terminal is stopped, the server sends The control for transmitting a signal for reducing the amount of data that can be continuously transmitted is executed.

In a seventh aspect based on the sixth aspect, the value further indicates a capacity for temporarily storing data transmitted from the transmission side in order to reduce the amount of data that can be transmitted continuously by the server. The control is executed such that the transmission is changed.

In an eighth aspect based on the seventh aspect, the value indicating the capacity for temporarily storing data sent from the server is changed to zero.

In a ninth aspect based on the seventh aspect, the value indicating the capacity for temporarily storing the data sent from the server is changed to the maximum value when the switching of the system is completed. .

According to a tenth aspect, in the seventh aspect, when a value indicating a capacity for temporarily storing data transmitted from the server is changed and transmitted, the server to be actually transmitted A value indicating a capacity for temporarily storing transmitted data, and a capacity for temporarily storing data transmitted from the server when the system switching is completed. Is changed to the stored value.

  According to the present invention, packet loss and congestion associated with hand-down are unlikely to occur, and the data transmission rate can be quickly recovered. In addition, unnecessary data can be prevented from being transmitted.

  Further, since congestion does not easily occur, the capacity of the buffer memory provided in each node can be reduced. Therefore, a system with little waste can be designed.

  Further, since the system may be designed based on the maximum throughput value of each session, the system design becomes easy.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram illustrating a connection state of a wireless communication system according to an embodiment of this invention.

  The server 1 is connected to a home agent (HA) 3 via a network 2. The home agent 3 is connected to a CDMA EV-DO wireless base station (AN) 6A via a PDSN (Packet Data Service Node) 4A and a PCF (Packet Control Function) 5A. The radio base station 6 </ b> A communicates with a radio communication terminal (AT) 7 that exists in the area (within the communication range from the radio tower).

  The home agent 3 is connected to a 1x wireless base station (BS) 6B via a PDSN (Packet Data Service Node) 4B and a PCF (Packet Control Function) 5B. The radio base station 6B communicates with a radio communication terminal (AT) 7 that exists in the communication area (within the communication range from the radio tower).

  In FIG. 1, the flow of data from the server 1 to the radio base station 6A during communication using the EV-DO method is indicated by a solid line, and the data flow from the server 1 to the radio base station 6B during communication using the 1x method is indicated by a broken line. Show.

  Since this wireless communication terminal (AT) 7 is a 1X / EV-DO hybrid terminal, the CDMA EV-DO system, which is a system with a maximum downlink throughput of 2.4 Mbps, and the CDMA2000 1x system, which is a system with a maximum downlink throughput of 144 Kbps, Packet communication can be performed using both communication methods. In addition, when the wireless communication terminal 7 is communicating by the EV-DO method, if the wireless communication terminal 7 moves out of the EV-DO range, the hand-down in which the packet communication path is switched from EV-DO to 1x within the 1x range. Is done.

  FIG. 2 is a block diagram illustrating a configuration of the wireless communication terminal 7 according to the embodiment of this invention.

  The wireless communication terminal (cellular phone terminal) 7 of the present embodiment is a wireless communication terminal that communicates while moving by performing handoff between the base station 6 by switching between the 1x system and the EV-DO system.

  The antenna 10 is connected to the radio processing unit 11, receives radio waves from the radio base station 6, and transmits radio waves to the radio base station 6. The wireless processing unit 11 includes a 1x wireless unit and an EV-DO wireless unit.

  The 1x radio unit generates a 1x high-frequency signal to be transmitted from the antenna 10 and an information processing unit that amplifies and converts a frequency of the 1x high-frequency signal received by the antenna 10 as a baseband signal. 12 is configured by a receiving unit that outputs the signal. The EV-DO radio unit generates a EV-DO type high-frequency signal transmitted from the antenna 10, and amplifies and converts the frequency of the high-frequency signal received by the antenna 10 using the EV-DO method. The reception unit outputs the baseband signal to the information processing unit 12.

  The information processing unit 12 includes a baseband unit and a radio control unit. The baseband unit demodulates the baseband signal. In addition, the signal is modulated to generate a baseband signal.

  The wireless control unit controls communication between the two systems of the 1x system and the EV-DO system by executing the program stored in the storage device 13. Specifically, switching between the 1x system and the EV-DO system is controlled. In particular, during standby, the two communication systems are selectively switched at predetermined time intervals to wait for incoming calls in both communication systems. Further, it controls the frequency transmitted and received by the wireless processing unit 11, the transmission / reception timing, and the output of the transmitted radio wave.

  The storage device 13 stores information, a control program, and various data necessary for the operation of the wireless communication terminal 6.

  The input unit 14 receives input of characters and numbers and an operation instruction to the wireless communication terminal 7.

  The display unit 15 is controlled by the information processing unit 12 and illuminates the liquid crystal display panel that displays character information, image information, the operating state (radio wave intensity, remaining battery level, time) of the wireless communication terminal 7, and the like Configured with a backlight.

  The receiving unit 16 converts the signal demodulated by the information processing unit 12 and outputs an acoustic signal.

  The transmitter 17 converts the input acoustic signal into an electrical signal.

  FIG. 3 is a configuration diagram of a TCP header according to the embodiment of this invention.

  TCP window size information is included in a predetermined portion of the TCP header of the acknowledgment (ACK) transmitted from the reception side (wireless communication terminal 7) to the transmission side (server 1). The window size (reception window size) is a value indicating a capacity (buffer) for temporarily storing data transmitted from the transmission side, and specifically, a reception buffer for TCP on the reception side. The transmitting side node that has received the ACK packet including the information of the TCP window size = 0 cannot transmit a new TCP packet. That is, the TCP window size represents the amount of data that can be continuously transmitted from the transmission side.

  The flag area of the TCP header includes a bit indicating the attribute of the TCP packet. For example, when the ACK flag is ON, it indicates that this packet is a reception confirmation. When the RST flag is ON, this packet indicates a forced disconnection of the connection. When the FIN flag is ON, this packet indicates the normal end of the connection.

  FIG. 4 is a sequence diagram of flow control based on the TCP window size according to the embodiment of this invention.

  When data (data amount = 1460 bytes) is transmitted from the transmission side, the reception side returns an acknowledgment (ACK) including the TCP window size (the free capacity of the reception buffer). When the reception packet can be processed immediately on the reception side, the maximum value (1460 × 22 = 32120 bytes) of the reception buffer on the reception side is returned as an acknowledgment.

  If data transmission continues from the transmission side for a while, there may be no available space in the reception buffer on the reception side for some reason. At this time, the receiving side returns an acknowledgment including information on TCP window size = 0. The transmission side that has received the confirmation response including the information of TCP window size = 0 stops the data transmission.

  When processing of the packet received on the reception side proceeds and a free space is generated in the reception buffer, the reception side transmits the free space in the reception buffer as a TCP window size. Then, the transmission side resumes data transmission.

  FIG. 5 is a sequence diagram of hand-down processing according to the embodiment of this invention.

  In the present embodiment, an example of handing down from a system having a high downlink maximum throughput (EV-DO system) to a system having a lower maximum throughput than that system (1x system) is shown.

  The wireless communication terminal (AT) 7 communicates with the EV-DO wireless base station (AN) 6A by the EV-DO method. At this time, when the communication quality between the wireless communication terminal (AT) and the wireless base station (AN) deteriorates, the wireless communication terminal (AT) includes information on TCP window size = 0 with respect to the server (CP) 1. Send an acknowledgment. Thereafter, the wireless communication terminal (AT) transmits a DRC NULL Cover signal, and stops transmission of data from the base station. Thereafter, the wireless communication terminal (AT) transmits a Connection Close signal, and stops communication with the EV-DO wireless base station (AN) by the EV-DO method.

  Thereafter, the wireless communication terminal (AT) establishes a connection with the 1x wireless base station (BS). Thereafter, the radio communication terminal (AT) establishes a session with the radio base station (BS) by PPP (Point to Point Protocol).

  Thereafter, the wireless communication terminal (AT) transmits a confirmation response including information of TCP window size = initial value (empty capacity when the reception buffer is empty) to the server (CP) 1. Note that the window size transmitted at this time is not the initial value, but the reception buffer free space immediately before transmitting the confirmation response including the information of TCP window size = 0, or the reception buffer free space when the session is established by PPP. May be sent. However, since the data is read from the buffer even during the hand-down process, it is usually sufficient to transmit the initial value at the end of the hand-down.

  Then, the wireless communication terminal (AT) 7 starts 1x communication with the 1x wireless base station (BS) 6B.

  As described above, in the hand-down process, immediately before the transmission of DRC NULL Cover, a TCP packet including information of TCP window size = 0 is transmitted to change the TCP window size. Then, immediately after the user PPP is established, the TCP window size is returned to the initial value. Therefore, data transmission from the server can be stopped immediately at the time of handdown, and congestion associated with handdown is unlikely to occur. Further, it is possible to prevent unnecessary data from flowing to the EV-DO system. In addition, since it is not necessary to increase the data rate from the minimum value after the hand-down process is completed, the data transmission speed can be quickly recovered.

  FIG. 6 is a functional block diagram of the wireless communication terminal according to the embodiment of this invention. Each function shown in FIG. 6 is realized by software.

  In the wireless communication terminal according to the embodiment of the present invention, a TCP window controller is added to realize the functions described above.

  At the time of socket communication, application software 100 such as a browser transmits data to the TCP window controller 140 via the TCP stack 110, the IP stack 120, and the PPP stack 130. Further, at the time of dial-up communication, the subsequent terminal connected in serial (for example, USB connection) transmits data from the serial IO 180 to the TCP window controller 140 via the PPP stack 130.

  Accordingly, all data passes through the TCP window controller 140 provided between the PPP stack 130 and the RLP stack 150.

  Note that the RLP stack 150 is a logical interface in the radio section, and performs congestion control and sequence control. The LAC stack 160 is a physical interface in the wireless section.

  Switches 141 and 142 are provided on the data transmission path of the TCP window controller 140, and the PPP stack 130 and the RLP stack 150 are directly connected in a state other than hand-down. Therefore, the transmission / reception data passes through the TCP window controller 140 as it is.

  When the H / D determination unit 149 detects the start of the hand-down sequence, the switches 141 and 142 switch the data transmission path. That is, the switch 141 sends the data from the RLP stack 150 to the TCP ACK processing unit 143. Further, the switch 142 sends data from the PPP stack 130 to the PPP reception processing unit 144.

  When in the snooping state, the TCP ACK processing unit 143 keeps discarding a TCP packet having a discontinuous ACK number to the upper layer so as not to be detected.

  The PPP reception processing unit 144 changes the window size so that no more packets are sent from the base station. In this embodiment, the packet is rewritten to a packet with the window size set to zero.

  The PPP reconfiguration unit 145 reframes the rewritten TCP packet to the PPP stack 130.

  The timer processing unit 146 is used as a timer for retransmitting the TCP packet whose window size has been restored in the Recovery state.

  The TCP / IP processing unit 147 analyzes the header information of the IP packet and the TCP packet.

  The packet storage buffer 148 temporarily stores received packets.

  FIG. 7 is a transition diagram of the operation state of the TCP window controller 140 according to the embodiment of this invention.

  The TCP window controller 140 has three states of Idle, Snooping, and Recovery.

  The Idle state is a state in which no hand-down has occurred, and transitions from the Recovery state by receiving an Ack for the initialized TCP window size packet. In the idle state, the PPP reception process and the TCP ACK process by the TCP window controller 140 are stopped. Specifically, in the idle state, the PPP stack 130 and the RLP stack 150 are directly connected, and the TCP window controller 140 does not affect the transmission packet.

  The Snooping state transitions from the Idol state due to the occurrence of handdown. In the Snooping state, the PPP window controller 140 performs PPP reception processing and TCP ACK processing. Specifically, in the snooping state, all PPP data transmitted from the PPP stack 130 in the state immediately after the occurrence of handdown is sent to the PPP reception processing unit 144. In this snooping state, the TCP window size of all TCP transmission packets is rewritten to “0” and transmitted.

  In the snooping state, all data from the RLP stack 150 is sent to the TCP ACK processing unit 143, and most of the packets are queued to the PPP stack 130 as they are. Discarded so that there is no.

  The Recovery state transitions from the Snooping state due to the establishment of the user PPP at 1x. In the Recovery state, the PPP reception process and the TCP ACK process by the TCP Window Controller 140 continue, but the TCP window size is returned to the initial value (see FIG. 9). Specifically, in the Recovery state, 1x handdown is completed, user PPP is also established, and the TCP window size is restored to continue transmission. Even in this Recovery state, all the PPP data from the PPP stack 130 is sent to the PPP reception processing unit 144 until an ACK is returned for the restored TCP window size packet. Data from the RLP stack 150 is also sent to the TCP ACK processing unit 143. TCP ACK processing is performed every time a packet is received.

  FIG. 8 is a flowchart of PPP reception processing by the TCP window controller 140 according to the embodiment of this invention.

  The TCP window controller 140 receives data transmitted from the wireless communication terminal 7 from the PPP stack 130 and transmits it to the RLP stack 150. The TCP window controller 140 sends all packets received from the PPP stack 130 to the PPP reception processing unit 144 except in the idle state.

  First, the H / D determination unit 149 determines the operating state of the wireless communication terminal 7 (S101).

  As a result, if it is in the idle state, the switch 142 is switched to the through side, and the transmission data is queued in the RLP stack 150 (S108). On the other hand, if it is not in the idle state (if it is in the snooping state or the recovery state), the switch 142 is switched, the transmission data is taken out from the PPP stack 130, sent to the PPP reception processing unit 144, and stored in the packet storage buffer 148. (S102).

  Next, the packet type is determined with reference to the IP header (S103). As a result, if the packet is not a TCP packet, the process proceeds to step S108, and the packet stored in the packet storage buffer 148 is queued in the RLP stack 150.

  On the other hand, if the packet is a TCP packet, the TCP flag is determined (S104). As a result, if the RST flag is ON or the FIN flag is ON, the connection is disconnected and the process proceeds to step S108, and the packet stored in the packet storage buffer 148 is queued to the RLP stack 150.

  On the other hand, if both the RST flag and the FIN flag are OFF, the operating state of the wireless communication terminal 7 is determined (S105).

  As a result, if it is in the Recovery state, unnecessary packets stored in the packet storage buffer 148 are discarded (S109).

  On the other hand, if it is in the snooping state, the window size is rewritten to “0” (S106), the checksum is recalculated to reconstruct the PPP packet (S107), and the reconstructed packet is queued in the RLP stack 150. (S108).

  FIG. 9 is a flowchart of TCP window reset processing by the TCP window controller 140 according to the embodiment of this invention.

  The TCP window reset process is executed immediately after transition from the Snooping state to the Recovery state, and sets the TCP window size to an initial value (maximum size).

  First, the operating state of the wireless communication terminal 7 is determined (S111).

  As a result, if it is not in the Recovery state, there is no need to change the TCP window size, so this processing is terminated.

  On the other hand, if it is in the Recovery state, the packet stored in the packet storage buffer 148 is taken out (S112).

  The TCP window size is rewritten to the initial value (16 kilobytes) (S113), the checksum is recalculated to reconstruct the PPP packet (S114), and the packet is queued in the RLP stack 150 (S115).

  Thereafter, a retransmission timer is started based on the RTT (Round Trip Time) of the monitored TCP packet (S116).

  FIG. 10 is a flowchart of retransmission timer timeout processing by the TCP window controller 140 according to the embodiment of this invention.

  When the timeout occurs, the TCP window reset is executed again (S121).

  FIG. 11 is an explanatory diagram of the RTT according to the embodiment of this invention.

  RTT (Round Trip Time) is the time from when a packet is transmitted from the transmitting side to when the corresponding packet (for example, ACK packet) is received from the receiving side, and is information held in the TCP stack 110. is there.

  FIG. 12 is a flowchart of TCP ACK processing by the TCP window controller 140 according to the embodiment of this invention.

  The TCP window controller 140 receives the data received by the wireless communication terminal 7 from the RLP stack 150 and transmits it to the PPP stack 130. The TCP window controller 140 sends all packets received from the PPP stack 130 to the TCP ACK processing unit 143 except in the idle state.

  First, the H / D determination unit 149 determines the operating state of the wireless communication terminal 7 (S131).

  As a result, if it is in the idle state, the switch 141 is switched to the through side and the received data is queued in the PPP stack 130 (S138). On the other hand, if it is not in the idle state (if it is in the snooping state or the recovery state), the switch 141 is switched to take out the IP packet in the PPP frame from which the transmission data is taken out from the RLP stack 150 and send it to the TCP ACK processing unit 143. send. Then, it continues to wait for an acknowledgment (TCP ACK) for the TCP packet transmitted with the window size as the initial value (S132).

  Next, the packet type is determined with reference to the IP header (S133). As a result, if the packet is not a TCP packet, the process proceeds to step S138, and the read packet is queued in the PPP stack 130.

  On the other hand, if the packet is a TCP packet, the TCP flag is determined (S134). As a result, if the RST flag is ON, the FIN flag is ON, or ACK is OFF, the process proceeds to step S138, and the read packet is queued in the PPP stack 130.

  The RST flag indicates a unilateral disconnection of the TCP connection, and the FIN flag indicates the end of the TCP connection. Since it is not necessary to maintain the connection, the general TCP reset and disconnection sequence is executed by directly passing through the upper layer.

  In addition, since the ACK flag is normally ON, data with the ACK flag OFF is an illegal packet.

  On the other hand, if the RST flag is OFF, the FIN flag is OFF, or the ACK flag is ON, the operating state of the wireless communication terminal 7 is determined (S135).

  As a result, if it is determined that it is in the snooping state, the process proceeds to step S140, and the read packet is discarded.

  On the TCP transmission side, when transmitting a packet, a sequence number and an ACK number are set. When the TCP reception side receives the packet, it puts “sequence number + data size” as an ACK number and returns it to the transmission side. The TCP transmission side also knows the ACK number, and if the ACK number is skipped like “sequence number + data size + α”, it is determined that the packet has been lost. It is determined that the packet has been lost at the layer, and high-speed retransmission and retransmission, which are TCP flow controls, occur. To avoid this, the packet is discarded.

  On the other hand, if it is in the Recovery state, it is determined whether or not the packet is an ACK packet for the TCP packet transmitted with the initial TCP window size (S136). When this ACK packet is received, the retransmission timer is stopped (S137), and the state transitions to the Idle state (S139). Thereafter, the switch 141 is switched to the through side, and the RLP stack 150 and the PPP stack 130 are directly connected.

  The present invention is not limited to the above-described embodiments, and can be applied to, for example, a wireless communication terminal that waits at the same time without selectively switching between the EV-DO system and the 1x system.

  Further, the present invention is not limited to two systems (communication methods), and can be applied to a wireless communication terminal that can use two or more systems.

  Further, the present invention can also be applied as a function of an information terminal that performs seamless communication in which a plurality of wireless communication devices having different systems (communication schemes) are connected and communication can be seamlessly continued while appropriately switching between systems.

It is a block diagram which shows the connection state of the radio | wireless communications system of embodiment of this invention. It is a block diagram which shows the structure of the radio | wireless communication terminal 7 of embodiment of this invention. It is a block diagram of the TCP header of embodiment of this invention. It is a sequence diagram of flow control by the TCP window size of the embodiment of the present invention. It is a sequence diagram of the hand-down process of the embodiment of the present invention. It is a functional block diagram of the radio | wireless communication terminal of embodiment of this invention. It is a transition diagram of the operation state of TCP Window Controller 140 of an embodiment of the invention. It is a flowchart of the PPP reception process by TCP Window Controller 140 of an embodiment of the invention. It is a flowchart of the TCP window reset process by TCP Window Controller 140 of an embodiment of the invention. It is a flowchart of the retransmission timer timeout processing by the TCP Window Controller 140 according to the embodiment of this invention. It is explanatory drawing of RTT of embodiment of this invention. It is a flowchart of the TCP ACK process by TCP Window Controller 140 of an embodiment of the invention. It is a sequence diagram of the conventional hand-down process.

Explanation of symbols

1 Server 2 Network 3 Home Agent (HA)
4A, 4B PDSN (Packet Data Service Node)
5A, 5B PCF (Packet Control Function)
6A Radio base station (AN)
6B Wireless base station (BS)
7 Wireless communication terminal (AT)
130 PPP stack 140 TCP Window Controller
141, 142 Switch 143 TCP ACK processing unit 144 PPP reception processing unit 145 PPP reconfiguration unit 146 Timer processing unit 147 TCP / IP processing unit 148 Packet storage buffer 149 H / D determination unit 150 RLP stack

Claims (10)

A wireless unit capable of data communication via a plurality of wireless communication systems;
When performing data communication via one system among the plurality of wireless communication systems, when switching from the system to a system having a lower maximum throughput than the system, a base station of the system performing the data communication Before the wireless communication terminal stops the transmission of data from the control unit that transmits a signal that reduces the amount of data that can be transmitted continuously by the server;
A wireless communication terminal.   The control unit changes a value indicating a capacity for temporarily storing data transmitted from the transmission side in order to reduce the amount of continuously transmittable data transmitted by the server, and transmits the data. The wireless communication terminal according to claim 1.   The wireless communication terminal according to claim 2, wherein the control unit changes a value indicating a capacity for temporarily storing data sent from the server to zero.   3. The control unit according to claim 2, wherein when the switching of the system is completed, the control unit changes a value indicating a capacity for temporarily storing data transmitted from the server to a maximum value. The wireless communication terminal described.   When the control unit changes the value indicating the capacity for temporarily storing the data sent from the server and sends the data, the control unit temporarily sends the data sent from the server to be actually sent. A value indicating a capacity to be stored is stored, and a value indicating a capacity to temporarily store data transmitted from the server when the switching of the system is completed is set to the stored value. The wireless communication terminal according to claim 2, wherein the wireless communication terminal is changed. To an information terminal capable of connecting a plurality of wireless communication terminals capable of data communication via a wireless communication system,
When performing data communication via one system among the plurality of wireless communication systems, when switching from the system to a system having a lower maximum throughput than the system, a base station of the system performing the data communication A program for executing a control for transmitting a signal for reducing the amount of data that can be transmitted continuously and transmitted by the server before the wireless communication terminal stops transmitting data from the terminal .   Further, in order to reduce the amount of data that can be transmitted continuously by the server, control is executed such that the value indicating the capacity for temporarily storing the data transmitted from the transmission side is changed and transmitted. The program according to claim 6.   Furthermore, the program of Claim 7 which changes the value which shows the capacity | capacitance which memorize | stores the data sent from the said server temporarily to zero.   The program according to claim 7, further comprising: changing a value indicating a capacity for temporarily storing data transmitted from the server to a maximum value when the switching of the system is completed.   Furthermore, when changing the value indicating the capacity for temporarily storing the data sent from the server and transmitting the data, the data sent from the server to be actually transmitted is temporarily stored. A value indicating a capacity to be stored is stored, and a value indicating a capacity to temporarily store data sent from the server is changed to the stored value when the switching of the system is completed. Item 8. The program according to item 7.

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