JP2002077300A - Window control method, receiver, data transfer method, repeat control method and repeater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sustain high communication efficiency, even in a communication environment of narrow band or high delays or narrow-band high delays, e.g. a wireless communication environment, in data transfer where a service node SN (transmitter) transmits data to a mobile terminal MS (receiver) using a window. SOLUTION: A service node SN employs the smaller of an advertisement window size informed from a mobile terminal MS or a congestion window size, depending on the transmission conditions of transmission data as the size of transmission window and transmits a TCP segment to the mobile terminal MS via a base station BS using the transmission window. At receiving of the TCP segment, the mobile terminal MS acquires the intensity of the radio wave of a radio link, determines an advertisement window size (e.g., 0), based on the intensity of radio wave and replies with an ACK (acknowledgement) which is designated with this advertisement window size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transfer method in which a transmitting device transmits data to a receiving device using a window, a window control method and a receiving device for controlling the window, and a method for transmitting data between a transmitting device and a receiving device. And a relay control method in the relay device.

[0002]

2. Description of the Related Art Conventionally, TCP / IP has been used as an industry standard communication protocol in a computer network.
(Transmission Control Protocol / Internet Protoco
l) is widespread. This TCP / IP has a two-layer configuration in which TCP, which is a communication protocol of a transport layer, is mounted on top of IP, which is a communication protocol of a network layer.

[0003] TCP establishes a connection identified by a combination of a socket (IP address and port number) of a transmitting end node and a socket of a receiving end node, and provides a full-duplex / bidirectional communication to a user of an upper application layer. Provide stream services. The data transfer unit in the connection is a segment, and the configuration is as shown in FIG.

[0004] In the TCP header field of FIG.
“Sequence number” is information indicating the octet position of the own segment in the transmission data stream. Also,
The “acknowledgement number” is information indicating the octet position of the data to be received next in the transmission data stream (the octet next to the received highest-order octet).
Used with the K flag. In addition, a “window”
Is information for specifying the window size (size of the transmission / reception buffer) at the time of segment transfer. The “code bit” is information indicating the type of the own segment, and the own segment is handled as a type corresponding to the flag set to ON. Note that the URG flag is an emergency segment, the ACK flag is a confirmation segment (hereinafter, an ACK segment), the PSH flag is a transfer forced segment, and the RST flag.
The flag corresponds to a reset segment, the SYN flag corresponds to a synchronous segment, and the FIN flag corresponds to a transfer end segment. Note that all flags are turned off in a normal data segment.

[0005] As described above, a segment includes a "window", and TCP performs data transfer based on the window size. That is, in TCP, flow control using a window of variable size is performed. In this flow control, the variable-size window is used in a sliding window system.

In the sliding window method, data in the window is continuously transmitted without an acknowledgment (ACK segment) from the receiving end node. The window slides. For example, in the example shown in FIG. 2, five data segments "1" to "5" in the window are transmitted in order, and A
When the CK segment is returned, the window W slides, and the subsequent “6” and “7” data segments come into the window W.

The transmitting end node adopts the smaller of the advertisement window size and the congestion window size as the final window size, and transmits a segment using the transmission window of this size. The advertisement window is a window set in the receiving end node based on the buffer capacity and data processing capacity of the receiving end node, and its size is notified from the receiving end node to the transmitting end node.

[0008] The congestion window is a window set at the transmitting end node to avoid congestion, and its size is calculated according to the reception status of the acknowledgment for the transmitted data segment. In a typical algorithm for calculating the congestion window size, the congestion window size is started from one segment, and the round trip time (from when the transmitting end node transmits the data segment to when the acknowledgment is normally received from the receiving end node). The time is multiplied by 2 for each time elapsed until an acknowledgment for the segment is received, and 0.5 when no acknowledgment can be received within the timeout period after transmission (when retransmission is performed). However, when the congestion window size is equal to or larger than the set threshold value, the increase amount of the congestion window for each round trip time is 1
It becomes the segment. The threshold value is a value indicating the start point of the congestion avoidance processing, and gradually increases while the acknowledgment is normally received from the receiving end node, and the acknowledgment cannot be received within the timeout period after transmission. Will be lowered if As described above, a method of setting the initial value of the congestion window size to a small value and gradually increasing the size from that value is called “slow start”, and is one of the important factors of congestion avoidance in TCP.

In recent years, LAN (Local Area Net)
work) and access to service nodes on the Internet, the communication path is becoming wireless, and TCP / I
Various mobile terminals corresponding to P have been developed and commercialized. Here, TC from service node SN to mobile terminal M
A procedure for transferring a P segment (a TCP data segment) and a functional configuration required at that time will be described with reference to FIG.

As shown in FIG. 3, a mobile terminal M includes a transport protocol processing unit M1 for processing a transport layer communication protocol, a network protocol processing unit M2 for processing a network layer communication protocol, A wireless data link processing unit M3 for processing a communication protocol of a wireless data link layer is provided. In response to these, the service node SN includes a transport protocol processing unit SN1, a network protocol processing unit SN2, and a wireless A data link processing unit SN3.

[0011] Also, the mobile node M
Indispensable functional element for transfer of TCP segment to
The transport protocol processing unit M1 includes a TCP segment reception processing unit M11, an advertisement window size determination unit M
12 and an ACK transmission processing unit M13. The transport protocol processing unit SN1 is provided with a TCP segment transmission processing unit SN11, an ACK segment reception processing unit SN12, and a window update unit SN13. Also,
The network protocol processors M2 and SN2 are provided with IP protocol processors M21 and SN21, respectively, and the wireless data link processors M3 and SN3 are provided with wireless link data processors M31 and SN31, respectively.
These functional elements realize the processing related to the transfer of the TCP segment from the service node SN to the mobile terminal M in each layer.

In the service node SN, when the TCP segment is transferred from the TCP segment transmission processing unit SN11 of the transport protocol processing unit SN1 to the lower network protocol processing unit SN2, the IP protocol processing unit SN21 uses the IP using the TCP segment. When a packet is generated and the IP packet is passed to the lower wireless data link processing unit SN3, a frame using the IP packet is generated in the wireless link data processing unit SN31, and the frame is transmitted to the physical layer (not shown). It is transferred to the network after processing.

On the other hand, in the mobile terminal M, the wireless link data processing unit M3 of the wireless data link processing unit SN3
1 receives a frame addressed to its own terminal from the network through the processing of the physical layer, restores an IP packet from the frame and passes it to the upper network protocol processing unit M2, and the IP protocol processing unit M21 uses the IP packet. Thus, the TCP segment is restored.

Further, the TCP segment is passed to the transport protocol processing unit M1 and received by the TCP segment reception processing unit M11. Further, the transport protocol processing unit M1 stores the received segment (here, the TCP segment received by the TCP segment reception processing unit M11) in a shared buffer (not shown) with the upper application layer, and stores the received segment in the upper application layer. The processing for use and the processing for calculating the advertisement window size by the advertisement window size determination unit M12 are performed. In the ACK transmission processing unit M13, an ACK segment corresponding to the reception segment is created and passed to the lower network protocol processing unit M2. At this time, the advertisement window size calculated by the advertisement window size determination unit M12 is specified in the window field of the ACK segment. Thereafter, the process is performed in the reverse order to the above, and the ACK segment is passed to the transport protocol processing unit M1 of the service node SN and received by the ACK segment reception processing unit SN12.

The transport protocol processing unit M
1, the ACK is transmitted by the window update unit SN13.
A TCP that holds an advertisement window size of the mobile terminal M specified in the segment and that can be transferred without acknowledgment based on the minimum value of the advertisement window size and the congestion window size calculated for the mobile terminal M
The segment (ie, transmission window size) is determined. The TCP segment determined here is transferred to the mobile terminal M according to the above-described transfer procedure.

Next, the flow of a TCP communication control process performed by the mobile terminal M will be described with reference to FIG. As shown in this figure, when a power supply (not shown) of the mobile terminal M is turned on (or when a communication process for realizing communication in accordance with TCP / IP is started), the mobile terminal M performs TCP communication. An event wait state is set for control (step S
A1). In this situation, the O
When the PEN command is passed (step SA2), the mobile terminal M performs negotiation by a three-way handshake with a communication partner (here, the service node SN) specified by the OPEN command to establish a connection (step SA3). Return to event waiting.

When the CLOSE command is passed from the upper application layer in the event waiting (step SA4), if there is a connection specified by the CLOSE command, a TCP communication termination process for releasing the connection is performed (step SA4). SA5, S
A6), and return to event waiting. Conversely, if the connection specified by the CLOSE command does not exist, the mobile terminal M returns to the event wait without doing anything (step SA5).

In the event waiting process, when an event other than the above occurs, the mobile terminal M performs a process according to the event. For example, when a TCP segment is transferred from a communication partner, a TCP advertisement window control process shown in FIG. 5 is performed. This TCP advertisement window control processing is performed by the transport protocol processing unit M1 described above.
(Steps SB1 to SB3), and after this series of processing, the mobile terminal M returns to the event waiting state.

Further, in addition to the functional configuration shown in FIG. 3, the mobile terminal M has a functional configuration for performing communication control of the wireless data link shown in FIG. FIG. 6 shows the mobile terminal M
And a wireless data link communication control of a wireless data link processing unit BS1 provided in a base station (not shown) for communicating with the mobile terminal M. Such a functional configuration is shown.

As shown in FIG. 1, a radio data link processing unit BS1 of a base station includes a beacon frame processing unit BS11 for transmitting a beacon frame including a base station ID to a mobile terminal M, and a mobile terminal M. A synchronization processing unit BS12 for performing a synchronization process is provided. The wireless data link processing unit M3 of the mobile terminal M includes a beacon frame processing unit M32 corresponding to the beacon frame processing unit BS11.
And a synchronization processing unit M35 corresponding to the synchronization processing unit BS12
And a base station list update processing unit M33 having a base station list L storing information on neighboring base stations, and an optimal BS processing unit M34 for selecting an optimal base station based on the base station list L.

In the wireless data link processing unit M3 having the above configuration, when the beacon frame processing unit M32 receives the beacon frame transmitted from the base station, the base station list update processing unit M33 sets the base station set in the beacon frame. The base station list L is changed using information such as the station ID and the radio wave intensity. This change processing includes addition, change, and deletion of information. In the optimum base station processing unit M34, the optimum base station is selected based on the base station list L, and the synchronization processing unit M35 performs a synchronization process on the selected optimum base station.

[0022]

In a wireless communication environment, the strength of radio waves from a base station changes due to various factors such as movement of mobile terminals, fading, and radio interference. Therefore, when transferring a TCP segment from a service node to a mobile terminal according to TCP / IP,
Segments are easily lost compared to a wired network environment such as Ethernet (registered trademark).

As described above, when the TCP segment from the service node to the mobile terminal disappears, an acknowledgment time-out occurs in the service node, the time-out TCP segment is retransmitted, and the congestion window size and the threshold value are reduced. Become.
Therefore, it can be said that the congestion window size and the threshold value are small in a mobile terminal supporting TCP / IP, and there is a high possibility that the throughput temporarily decreases.

Further, since slow start is adopted in TCP, once the congestion window size and the threshold value become small, it takes some time until the communication throughput is recovered. Of course, the communication throughput in the wireless communication environment also recovers in accordance with the recovery of the radio wave intensity, but the wireless communication environment usually has a narrower band and a higher delay than the wired communication environment, so it has become smaller. It takes a long time for the congestion window size and the threshold value to recover.

As described above, the conventional window control method in the TCP-based communication has a problem that the communication efficiency is reduced in a narrow band or high delay communication environment. This problem is particularly remarkable when a mobile terminal that is based on a wireless communication environment is used.

The present invention has been made in view of the above circumstances, and in a data transfer in which a transmitting apparatus transmits data to a receiving apparatus using a window, a narrow band, a high delay, or a narrow band such as a wireless communication environment is used. It is an object of the present invention to provide a data transfer method, a window control method, a receiving device, a relay control method, and a relay device that can maintain high communication efficiency even in a communication environment with a high band delay.

[0027]

According to a first aspect of the present invention, there is provided a window control method, wherein a size of a window varies according to a transmission data delivery confirmation state within a notified upper limit size. In a window control method in a receiving device that receives data of a transport layer transmitted from a transmitting device that controls data transmission using a window, a communication quality of a link in a layer lower than the transport layer is obtained. An upper limit size is determined based on communication quality, and the upper limit size is notified to the transmitting device.

In order to solve the above-mentioned problem, a window control method according to a second aspect of the present invention is to provide a window control method for setting a window having a size which varies within a range of a notified upper limit size according to a transmission data delivery confirmation status. In a window control method in a receiving device that receives data of a transport layer transmitted from a transmitting device that controls transmission of data using a communication device, a communication quality of a link of a layer lower than the transport layer satisfies a predetermined criterion. When the transport layer data transmitted from the transmission device is received during a non-period, the upper limit size having the minimum value is notified to the transmission device.

Further, in the window control method according to claim 2, the transmission apparatus detects a start of a period in which the communication quality satisfies a predetermined criterion, and after the detection, sets an upper limit size larger than the minimum value to the transmission apparatus. May be notified (claim 3).

In order to solve the above-mentioned problem, a window control method according to a fourth aspect uses a window whose size varies according to a transmission data delivery confirmation status within a range of a notified upper limit size. In a window control method in a receiving device that receives data of a transport layer transmitted from a transmitting device that controls data transmission, communication quality related to a link of a layer lower than the transport layer does not satisfy a preset criterion. In the period, when data of the transport layer transmitted from the transmitting device is received, a storing step of storing the data, and detecting an end of a period in which the communication quality does not satisfy a predetermined standard, A confirmation response for transmitting the information indicating the delivery of the data stored in the storing step after the detection to the transmitting device. It is characterized by a step.

Further, in the window control method according to claim 4, the communication quality may be periodically acquired to detect the end of the period (claim 5).

Further, in the window control method according to any one of claims 1 to 5, the receiving device may be a mobile radio terminal, the link may be a radio link, and the communication quality may be radio field intensity. ).

In order to solve the above-mentioned problem, a receiving apparatus according to claim 7 uses a window whose size fluctuates according to a transmission data delivery confirmation state within a range of a received upper limit size. In a receiving apparatus that receives data of the transport layer transmitted from a transmitting apparatus that controls transmission of data and returns acknowledgment data corresponding to the data, obtains communication quality related to a link of a layer lower than the transport layer. A communication quality obtaining unit, an upper limit size determining unit that determines the upper limit size based on the communication quality obtained by the communication quality obtaining unit, and an upper limit size determined by the upper limit size determining unit included in the delivery confirmation data. And an acknowledgment transmitting unit for transmitting to the transmitting device.

[0034] The receiving apparatus according to claim 7, further comprising a criterion determining unit for determining whether or not the communication quality acquired by the communication quality acquiring unit satisfies a preset criterion; The determining unit may further determine a predetermined minimum value as an upper limit size when the communication quality acquired by the communication quality acquiring unit determines that the communication quality does not satisfy a preset standard by the standard determining unit. (Claim 8).

Further, in the receiving apparatus according to claim 8, the acquisition trigger control unit that controls the communication quality acquisition unit to periodically acquire the communication quality, and the acquisition trigger control unit based on the determination result by the reference determination unit. A recovery detection unit that detects a start of a period in which communication quality satisfies a preset criterion, wherein the upper limit size determination unit further detects the start of the period by the recovery detection unit from the minimum value. A larger value may be determined as the upper limit size (claim 9).

[0036] In order to solve the above-mentioned problem, a receiving apparatus according to claim 10 uses a window whose size fluctuates according to a transmission data delivery confirmation status within a range of a received upper limit size. In a receiving apparatus that receives data of the transport layer transmitted from a transmitting apparatus that controls transmission of data and returns acknowledgment data corresponding to the data, obtains communication quality related to a link of a layer lower than the transport layer. Deterioration that determines whether or not the communication quality is within a period in which the communication quality does not satisfy the preset criterion based on the communication quality acquired by the communication quality acquiring unit and the preset standard. A period determination unit, and transport layer data transmitted from the transmission device during a period determined by the deterioration period determination unit to be within the period. A storage acknowledgment processing unit that stores the data when received, and based on the communication quality acquired by the communication quality acquiring unit and a preset criterion, the communication quality satisfies a preset criterion. A recovery detection unit that detects the start of a period, wherein the storage acknowledgment processing unit further includes a transmission acknowledgment corresponding to data stored in the storage unit when the start of the period is detected by the recovery detection unit. Data is transmitted to the transmitting device.

[0037] Further, in the receiving apparatus according to the tenth aspect, an acquisition trigger control unit that controls the communication quality acquiring unit to periodically acquire the communication quality may be provided (claim 11).

The receiving apparatus according to any one of claims 7 to 11, further comprising a wireless communication unit that receives the data of the transport layer transmitted from the transmitting apparatus via a wireless communication network. A wireless link may be used, and the communication quality may be radio field intensity in the wireless link.

[0039] In the receiving apparatus according to the twelfth aspect, a radio field intensity storage unit storing information indicating the radio field intensity of the radio link, and constantly monitors the radio field intensity of the radio link, and according to the monitoring result, A radio field intensity monitoring unit that sequentially updates the information stored in the storage unit, wherein the communication quality acquisition unit acquires the radio field intensity of the link by reading the information from the radio field intensity storage unit. (Claim 13).

According to another aspect of the present invention, there is provided a data transfer method for transporting data from a transmitting apparatus to a receiving apparatus using a window whose size varies according to a transmission data delivery confirmation status. In a data transfer method for transmitting data of a layer, a receiving-side communication quality obtaining step of obtaining a receiving-side communication quality in a layer lower than a transport layer, and a communication quality obtained in the communication quality obtaining step are taken into consideration. And a size determining step of determining the size.

In order to solve the above-mentioned problem, a relay control method according to claim 15 uses a window whose size varies according to a transmission data delivery confirmation status within a range of a received upper limit size. A transmission device that controls data transmission, and receives the transport layer data transmitted from the transmission device, and sets an upper limit size based on the communication quality for a link of a layer lower than the transport layer to the data of the transport layer. In the relay control method in the relay device that transfers data to and from the receiving device that returns the data included in the acknowledgment data, the value of the upper limit size in the acknowledgment data transmitted from the receiving device to the transmitting device is If smaller, the transfer of the acknowledgment data to the transmitting device is delayed and the data from the transmitting device to the receiving device is temporarily deleted. And acknowledgment data is characterized by transferring the temporarily saved data when transmitted from the receiving device to said transmitting device to said receiving device comprising a large size limit in this situation.

The relay control method according to claim 15, wherein the receiving device is a mobile radio terminal, the link is a radio link, the communication quality is radio field intensity, and the receiving device is under the control of another relay device. In this case, the temporarily saved data may be transferred to the other relay device, and the data transferred from the other relay device may be received and transferred to the receiving device. .

In the relay control method according to claim 15 or 16, when the upper limit size of the acknowledgment data transmitted from the receiving device to the transmitting device is small, the acknowledgment data is transmitted to the transmitting device. May be delayed by a certain time (claim 17).

In the relay control method according to the present invention, when the receiving device moves to another relay device, the temporarily saved data is transferred to the other relay device and the transfer is delayed. The transmitted unacknowledged acknowledgment data may be transferred to the transmitting device (claim 18).

In order to solve the above-mentioned problem, the relay device according to the nineteenth aspect uses a window whose size varies according to the transmission confirmation status of transmission data within the range of the received upper limit size. A transmission device that controls the transmission of the data, and receives the data of the transport layer transmitted from the transmission device, and sets the upper limit size based on the communication quality of the link of the layer lower than the transport layer to the data of the transport layer. A relay device for transferring data to and from the receiving device that returns the data including the acknowledgment data; a temporary storage unit for temporarily storing the data; and acknowledgment data transmitted from the receiving device to the transmitting device. An upper limit size extracting unit that extracts an upper limit size from the upper limit size extracting unit; When the inspection unit determines that the upper limit size is small, the delay processing unit that delays the delivery confirmation data including the upper limit size and transfers the data to the transmission device, and the inspection unit determines that the upper limit size is small. In the case, a save processing unit that starts a save process for storing data from the transmitting device to the receiving device in the temporary storage unit, and an upper limit size is large by the inspection unit in an environment where the save process is performed. When it is determined that the evacuation process is started, the data stored in the temporary storage unit is transferred to the receiving device from the start of the evacuation process, and a recovery processing unit that terminates the evacuation process is provided. I have.

Also, in the relay device according to the nineteenth aspect, there is provided a mobile corresponding receiving unit for receiving data transferred from another relay device and transferring the data to the receiving device, wherein the receiving device is a mobile radio terminal, The link is a wireless link, the communication quality is radio wave intensity, the recovery processing unit,
If the receiving device moves to another relay device under the environment where the saving process is being performed, the data stored in the temporary storage unit from the start of the saving process is transferred to the other relay device. (Claim 20).

21. The relay device according to claim 19, wherein the delay processing unit, when the inspection unit determines that the upper limit size is small, transmits the delivery confirmation data including the upper limit size for a predetermined time. The data may be transferred to the transmission device after a delay.
1).

In the relay device according to the twentieth aspect, when the receiving device moves to a position under another relay device in an environment where the evacuation process is being performed, From the start of the evacuation process, the data stored in the temporary storage unit is transferred to the other relay device, and the untransferred acknowledgment data whose transfer has been delayed is transferred to the transmitting device. Good (claim 22).

[0049]

Embodiments of the present invention will be described below with reference to the drawings. In each figure, TC
Elements having the same function related to the transfer of the P segment are denoted by the same reference numerals, and redundant description will be avoided.

<First Embodiment> (1) System Configuration According to First Embodiment FIG. 7 is a conceptual diagram showing a configuration example of a mobile communication system using a mobile terminal MS according to a first embodiment of the present invention. The mobile terminal MS shown in FIG.
A communication function for performing communication according to
S performs wireless data link layer communication with S,
The TCP segment is transferred from the service node SN via the network NW and the base station BS. The network NW is a network compatible with TCP / IP, such as a mobile packet communication network, a LAN, and the Internet. Although not shown, a plurality of base stations BS are connected (or accommodated) to the network NW, and the mobile terminal MS selects an optimum base station BS from the plurality of base stations BS, and selects this base station BS. Via the TCP segment.

(2) Hardware Configuration of Mobile Terminal MS FIG. 8 is a block diagram showing a hardware configuration of the mobile terminal MS. In FIG. 8, reference numeral 1 denotes a radio unit for performing radio communication with the base station BS; The control unit controls the wireless unit 1 and exchanges data with the wireless unit 1. The control unit 2 is a CPU (Central Processing Unit) that performs various controls and calculations.
nit) 21, an update-impossible storage unit 22 that non-updateably stores various programs and parameters (for example, thresholds) read by the CPU 21, an updatable storage unit 23 used as a work area of the CPU 21, and control by the CPU 21. And a timer 24 for generating an interrupt signal at a time interval set by the CPU 21. Various functions described later are realized by the CPU 21 executing various programs stored in at least one of the non-updatable storage unit 22 and the updatable storage unit 23.

(3) Function of Mobile Terminal MS (3-1) Overview Basically, when the mobile terminal MS receives a transfer of a TCP segment from the service node SN via the base station BS and the network NW, the base station MS If the signal strength corresponding to the BS falls below a preset threshold, the received T
The CP segment (received segment) is stored, and an ACK segment with the advertisement window size set to 0 is transmitted to the server node SN. An ACK segment of the advertisement window size is transmitted to the server node SN. In the embodiment of the present invention, “storage” of a reception segment means a process of copying a reception segment stored in a reception buffer (or a shared buffer) and storing the duplicate in a predetermined storage area. That is, the received segment is used by the upper application layer, and when the radio field intensity at the time of the reception is equal to or less than a preset threshold, the duplicate data is stored in a predetermined storage area.

That is, the mobile terminal MS suspends the transmission of the TCP segment from the service node SN and resumes the transmission after the radio wave intensity recovers because there is a possibility of packet loss if the radio wave intensity is too weak. By that
The service node SN operates to suppress transmission of a TCP segment in which a timeout is likely to occur. In addition, the mobile terminal MS retransmits the ACK segment that may not have been transmitted normally due to the weak radio field strength after the radio field strength has been restored, and thereby the service node S
The number of timeout occurrences in N is reduced.

(3-2) Specific Functions Next, specific functions of the mobile terminal MS will be described with reference to FIG. FIG. 9 is a block diagram showing a functional configuration related to TCP advertisement window control in the mobile terminal MS,
As shown in this figure, the mobile terminal MS performs transport protocol processing M
S1, a network protocol processing unit M2, a wireless data link processing unit M3, and a wireless TCP advertisement window control processing unit MS2. The functions of the network protocol processing unit M2 and the wireless data link processing unit M3 are as described above.

The transport protocol processing section MS1 includes all functions of the transport protocol processing section M1 shown in FIG. That is, the units MS11 to MS1 included in the transport protocol processing unit MS1
Reference numeral 3 has all the functions of the corresponding units M11 to M13 in the transport protocol processing unit M1. Each part MS11
The new functions of the MS 13 will be described later. on the other hand,
TCP link window control processing unit M for wireless link
S2 includes a radio field strength inspection processing section MS21, a reception segment storage processing section MS22, an ACK information designation section MS23, an advertisement window size designation section MS24, and a timer processing section M
S25 is included.

(3-2-1) Functions of the Transport Protocol Processing Unit MS1 The new functions of the TCP segment reception processing unit MS11 of the transport protocol processing unit MS1 include:
A function of notifying the radio wave intensity inspection processing unit MS21 when a TCP segment is received, and a function of permitting the reception segment storage processing unit MS22 to access a reception buffer (not shown).

As a new function of the advertisement window size determination section MS12, when an advertisement window size is designated by the advertisement window size designation section MS24, the advertisement window size is adopted as the advertisement window size of the own terminal. And a function of calculating the advertisement window size by ordinary calculation when a restart instruction described later is given from the radio wave intensity inspection processing unit MS21.

The ACK transmission processing section MS13 has a new function that, when ACK information is passed from the ACK information specifying section MS23, the ACK is transmitted based on the ACK information.
A segment is generated, and the ACK segment is set in the window field of the advertisement window size determination unit MS.
There is a function of passing the calculated advertisement window size to the IP protocol processing unit M21 of the network protocol processing unit M2 after designating (adopting) the advertisement window size.

(3-2-2) TCP for Wireless Link
The function of the advertisement window control processing unit MS2 The radio wave intensity inspection processing unit MS21 acquires the radio wave intensity from the base station list L in the wireless data link processing unit M3. Notification from the unit MS11 and the timer processing unit MS
25 is an interrupt notification. Further, the radio wave intensity inspection processing unit MS21 determines whether or not the obtained radio wave intensity is equal to or smaller than a preset threshold value, and if the obtained radio wave intensity exceeds the threshold value, notifies the restart instruction to the advertisement window size determination unit MS12. This restart instruction is an instruction to restart the process of obtaining the advertisement window size by normal calculation. Further, the radio wave intensity inspection processing unit MS21 notifies the reception segment storage processing unit MS22 of the above determination result and the type of the trigger.

Upon receiving the information from the radio wave intensity inspection processing unit MS21, the reception segment storage processing unit MS22
A process according to this information is performed. When receiving the information indicating that the radio field intensity is equal to or less than the preset threshold from the radio field intensity inspection processing unit MS21, the reception segment storage processing unit MS22 notifies the fact to that effect.
Notify to S12. In addition, the radio wave intensity inspection processing unit MS21
If the information from indicates that the radio field intensity obtained upon reception of the TCP segment is equal to or less than the threshold,
The reception segment storage processing unit MS22 reads out the reception segment of the TCP segment reception processing unit MS11 from the reception buffer and stores it as the storage segment SS. At this time, if the storage segment SS already exists, its contents are replaced.

If the information from the radio wave intensity inspection processing unit MS21 indicates that the radio wave intensity obtained as a result of the interrupt notification exceeds the threshold, the reception segment storage processing unit MS22 advertises that fact. In addition to notifying the window size determining unit MS12, the storage segment SS
ACK for the segment from the header field of
The information (sequence number, acknowledgment number, etc.) necessary for generating the segment is read out and passed to the ACK information designation section MS23 to clear (delete or delete) the storage segment SS.

The information from the radio wave intensity inspection processing unit MS21 indicates that the radio wave intensity obtained when the TCP segment is received exceeds the threshold value and that the radio wave intensity obtained when the interrupt notification is received is equal to or less than the threshold value. In the case of indicating any of the above, the received segment storage processing unit MS2
2 does nothing.

The ACK information designation section MS23 notifies the information passed from the reception segment storage processing section MS22 to the ACK transmission processing section MS13 as ACK information.

The advertisement window size designation section MS24
When receiving a notification from the received segment storage processing unit MS22 that the radio field intensity obtained upon reception of the TCP segment is equal to or less than a preset threshold, the minimum advertisement window size ( In the present embodiment, 0) is specified, and the setting of the timer and the contents of the setting are instructed to the timer processing unit MS25. It should be noted that the information indicating the setting content of the timer includes a time interval for periodically notifying the radio wave intensity inspection processing unit MS21. The time interval is set in advance, and the set value is arbitrary. In the present embodiment, a set value of about several seconds is adopted. In addition, upon receiving a notification from the reception segment storage processing unit MS22 that the radio field intensity obtained in response to the interrupt notification exceeds a preset threshold from the reception segment storage processing unit MS22, the advertisement window size specification unit MS24 To cancel the timer.

Upon receiving a timer setting instruction from advertisement window size specifying section MS24, timer processing section MS25 sets the timer in accordance with the instruction. The timer processing unit MS25 in a state where the timer is set issues an interrupt notification to the radio wave intensity inspection processing unit MS21 at a timing according to the set contents (every several seconds in the present embodiment). Further, when receiving a timer release instruction from the advertisement window size designation unit MS24, the timer processing unit MS25 releases the timer according to this instruction. When the timer is released, the timer processing unit MS25 does nothing.

(4) TCP Communication Control Operation of Mobile Terminal MS Next, the operation of the mobile terminal MS having the above-described configuration and function will be described. However, here, the CPU of the control unit 2
It is assumed that 21 executes various programs stored in the non-updatable storage unit 22 or the updatable storage unit 23 and realizes the functions shown in FIG.

FIG. 10 is a flowchart showing the flow of the TCP communication control process executed by the mobile terminal MS. The difference between the flow shown in FIG. 10 and the flow shown in FIG.
The difference is that the process of step SC3 is provided instead of the process of A7, and the process of steps SC1 and SC2 is newly provided.

As shown in FIG. 10, in the mobile terminal MS,
The event that occurred during the event waiting is not the delivery of the OPEN command or the CLOSE command from the upper application layer (steps SA1, SA2, S
A4) If the notification is an interrupt notification output from the timer processing unit MS25, a periodic process described later is performed (steps SC1 and SC2). After the execution of the periodic processing, the mobile terminal M returns to the event waiting state. If the generated event is not any of the above-mentioned events, the mobile terminal MS performs a process corresponding to the event (step SC).
3). The TCP advertisement window control process (described later) included in the process of step SC3 is different from the same process included in the process of step SA7.

Next, regarding the above TCP communication control operation,
This will be specifically described with reference to FIGS. 10, 11, and 12. However, here, the mobile terminal MS and the optimal base station BS
It is assumed that the radio wave condition during the first period is stabilized at a sufficiently high level, then gradually deteriorates, and finally recovers rapidly.

When the TCP segment is transferred from the communication partner, the TCP advertisement window control processing of FIG. 11 is performed (step SC3). In the TCP advertisement window control process, first, the TCP segment reception processing unit MS11
Receives the TCP segment (step SD
1), the reception is notified to the radio wave intensity inspection processing unit MS21. This notification triggers the signal strength inspection processing unit MS
21, the radio field intensity corresponding to the optimal base station BS is obtained from the base station list L in the radio data link processing unit M3 (step SD2), and this radio field intensity is compared with a preset threshold value (step SD3). .

Since the radio wave condition between the mobile terminal MS and the optimal base station BS is stable at a sufficiently high level at first, the radio wave intensity exceeds a preset threshold. Therefore, the advertisement window size is calculated by the advertisement window size determination unit MS12 in a usual manner (step SD).
9) The ACK segment in which the calculated advertisement window size is set in the window field is transmitted to the network protocol processing unit M2 by the ACK transmission processing unit MS13.
(Step SD10). Thereafter, the mobile terminal MS enters the event waiting state again (step SA1 in FIG. 10). When the TCP segments are continuously transferred, the above-described processing is repeatedly performed until the radio wave condition deteriorates below a certain level.

If the radio wave condition deteriorates below a certain level and the TCP segment is transferred immediately after the radio wave intensity becomes lower than the threshold value, the judgment result in step SD3 changes.
As a result, the received segment is temporarily stored as the storage segment SS by the reception segment storage processing unit MS22 that has been notified of the information from the radio wave intensity inspection processing unit MS21 (step SD5). The timer is set in the timer setting section MS25 by the advertisement window size specification section MS24 receiving the information from the reception segment storage processing section MS22, and the advertisement window size setting section M
In S12, an advertisement window size having a value of 0 is adopted (steps SD7, SD8). The ACK segment whose advertising window size (ie, 0) is set in the window field is the ACK transmission processing unit M
It is passed to the IP protocol processing unit MS21 in S13 (step SD10). Thereafter, the mobile terminal MS enters the event waiting state again.

When the timer is set, the timer processing unit MS
25, an interruption notification is issued to the radio wave intensity inspection processing unit MS21 at predetermined time intervals (for example, at intervals of several seconds). When an interrupt notification is issued in the event waiting state, the mobile terminal MS starts the periodic processing in FIG. 12 (step SC).
1, SC2). In the periodic processing, the radio wave intensity inspection processing unit MS21 having received the interrupt notification obtains the radio wave intensity corresponding to the optimum base station BS (step SE1), and compares this radio wave intensity with a preset threshold (step S1).
E2). Here, since the radio wave intensity is equal to or less than the threshold value, the mobile terminal MS is again in an event waiting state. The above process is periodically repeated until the radio wave condition is restored and the radio wave intensity exceeds the threshold.

When the TCP segment is transferred in this situation, since the storage segment SS has already been stored, the received segment storage processing section MS22 stores the TCP segment as the storage segment SS ( Steps SD4 and SD5). That is, the contents of the storage segment SS are exchanged. Subsequent processing is the same as the processing for storing the storage segment SS first, and after the processing of steps SD7, SD8, and SD10, the mobile terminal MS again enters the event waiting state.

Here, when an interrupt notification is issued from the timer processing unit MS25 in a situation where the radio wave condition is rapidly recovered and the radio wave intensity exceeds the threshold value, the determination result in step SE2 in FIG. 12 changes. As a result, the radio wave strength inspection processing unit
1 to the advertisement window size determination unit MS12, a restart instruction is passed, and the advertisement window size determination unit MS12 calculates the advertisement window size by a normal method (step SE5). Further, information (sequence number, acknowledgment number, etc.) is acquired from the header field of the storage segment SS by the reception segment storage processing unit MS22 which has received the information from the radio wave intensity inspection processing unit MS21, and ACK information based on this information is ACK. It is passed from the information specifying unit MS23 to the ACK transmission processing unit MS13 (step SE).
3). Further, the timer is canceled in the timer setting unit MS25 by the advertisement window size designation unit MS24 receiving the information from the received segment storage processing unit MS22 (step SE4).

Then, the AC for the storage segment SS
The ACK segment in which the advertisement window size calculated by the normal calculation is specified in the window field is the K segment and the ACK transmission processing unit
It is passed to the protocol processing unit MS21 (step SE1).
0). At this time, the storage segment SS is cleared by the reception segment storage processing unit MS22 (step SE7). Therefore, the next time the received segment is temporarily stored, it is not a replacement but a new storage. Thereafter, the mobile terminal MS enters the event waiting state again. Since the timer has already been released, the periodic processing is not performed unless the radio wave intensity falls below the threshold and the timer is set again.

When the radio wave condition is restored and the radio wave intensity exceeds the threshold, the TCP segment is transferred, and the operation is performed when the radio wave condition is stable at a sufficiently high level. This is the operation in the case where it has been performed, as described above.

(5) Operation of Mobile Communication System According to First Embodiment Next, the operation of the mobile communication system using the mobile terminal MS will be described with reference to FIG. FIG. 13 shows a mobile terminal MS and a service node S in the mobile communication system.
FIG. 7 is a conceptual diagram showing an example of the exchange with the N. The example shown in this figure is based on the condition (the radio wave condition between the mobile terminal MS and the optimal base station BS,
It stabilizes at a sufficiently high level at first, then gradually worsens,
Finally, it is obtained under the same conditions.

In this figure, the sequence depicted on the service node SN side is a TCP segment transmitted from the service node SN to the mobile terminal MS, and the sequence depicted on the mobile terminal MS side is received at the mobile terminal MS. TCP segment. Further, on the mobile terminal MS side, the transition of the content of the storage segment SS is drawn in association with the above sequence. The numbers 1 to 6 indicate the order of appearance of the segments, and in each sequence and transition, the same number is described in the corresponding part. Note that in this figure, the time is the time t
The section has passed in the direction from 1 to time t6, and before time t1 and after time t5, the section where the radio field intensity exceeds the threshold, and the section from time t1 to time t5 is the section where the field intensity is below the threshold. Further, in the section from the time t1 to the time t5, the radio wave intensity gradually decreases.

When the first TCP segment is transmitted from the service node SN in a situation where the radio field intensity before the time t1 exceeds the threshold, the TCP segment d1 is received by the mobile terminal MS with a certain delay. You. This delay is a delay due to the delay time of the communication path. In the example shown in this figure, the transfer timing of the third TCP segment d3 in the service node SN and the reception timing of the first TCP segment in the mobile terminal MS are different. There is a delay time that matches.

The mobile terminal MS receiving the first TCP segment d1 sends an ACK segment a1 corresponding to the received segment to the service node SN. Since this time is before the time t1, the advertisement window size specified in the window field in the ACK segment a1 is a size obtained by normal calculation, and the service node SN that has received the ACK segment a1 The minimum value of the gradually increasing congestion window size and advertisement window size is determined as the transmission window size.

The reception time (time t2) of the second TCP segment d2 in the mobile terminal MS is within the section from time t1 to time t5 when the radio field intensity is below the threshold.
Therefore, in the mobile terminal MS, the second TCP segment d2 is temporarily stored as the storage segment SS. Also, A transmitted from the mobile terminal MS to the service node SN corresponding to the second TCP segment d2
0 is specified in the window field in the CK segment a2. Therefore, in the service node SN receiving this ACK segment a2, the transmission window size becomes 0, and the subsequent transfer of the TCP packet is stopped.

However, since the ACK segment a2 is received by the service node SN after the fifth TCP segment d5 has been transmitted, the third TCP segment d is transmitted from the service node SN to the mobile terminal MS.
The third and fourth TCP segments d4 and the fifth TCP segment d5 are sequentially transmitted. here,
Of these TCP segments, the third TCP segment d3 and the fourth TCP segment d4 are received at the mobile terminal MS, and the fifth TCP segment d
5 is assumed to be lost in the wireless section because the radio wave intensity has become extremely weak.

In the mobile terminal MS, at the reception timing (time t3, t4) of the third TCP segment d3 and the fourth TCP segment d4, the content of the storage segment SS is replaced with the latest reception segment.
ACK with 0 specified in each window field
Segments a3 and a4 are sent to service node SN. However, these ACK segments a3 and a4 are
It is assumed that it disappears for the same reason as the fifth TCP segment d5.

As a result, the ACK segment received at service node SN until time t5 is the first T
The one corresponding to the CP segment d1 and the second TCP
Only those corresponding to the segment d2 are provided. After the transmission of the fifth TCP segment d5, the service node S
The transmission of the TCP segment from N is stopped. When the radio wave condition recovers at time t5 and the radio wave intensity exceeds the threshold value, this is detected by the mobile terminal MS and the time t5
In 6, an ACK segment a4 corresponding to the storage segment SS (the fourth TCP segment d4) is transmitted from the mobile terminal MS. The advertisement window size specified in the window field in the ACK segment a4 is a size obtained by ordinary calculation.

The fourth TC in the service node SN
Assuming that the ACK segment a4 is received before the timeout of the P segment d4 and the third TCP segment has not timed out, no TCP segment has timed out at this time. Therefore,
The transmission window size of the service node SN does not become smaller than the transmission window size before stopping the transfer.

Since the third TCP segment has not timed out, the mobile node MS
The sixth TCP segment d6 is sent to
The segment d7 is sent out. By this point 3
When the TCP segment d3 times out, the TCP segment is retransmitted.

(6) Supplement According to First Embodiment As described above, according to the first embodiment of the present invention, when the radio field intensity becomes weak due to factors such as the mobile terminal MS being separated from the base station BS, the TCP is used. Since the communication is temporarily interrupted, it is possible to avoid the reduction of the width window size and the decrease of the threshold value due to the packet loss. Further, when the radio wave intensity becomes strong, the advertisement window size is calculated by a normal method, so that the communication throughput can be quickly restored. From these facts, in the above-described embodiment, a large increase in communication throughput is achieved.

Further, in the present embodiment, the TCP segment received when the radio wave intensity is weakened in the mobile terminal MS is stored as the storage segment SS, and the ACK segment corresponding to the storage segment SS is restored when the radio wave intensity is restored. The message is transmitted to the node SN.
As a result, it is possible to more reliably avoid a reduction in the width window size and a decrease in the threshold value due to packet loss. Since the ACK segment is used as the notification method of the advertisement window size similarly to the existing method, there is an advantage that the existing service node SN can be used as it is.

In the above-described embodiment, the number of the storage segments SS is set to one. However, a plurality of storage segments SS may be set, and a plurality of ACK segments corresponding to the plurality of storage segments may be transmitted after the recovery of the radio field intensity. Further, the timeout time in the service node SN and the service node SN
Only the storage segment that can avoid the timeout based on the round trip time between and may be returned to the service node SN after the recovery of the radio wave intensity.

Although not specifically mentioned in the present embodiment, the threshold value may be set at the time of shipment of the mobile terminal MS from the factory, or may be set by the user.
Furthermore, the mobile terminal MS may be any wireless communication device that supports TCP / IP, and may be, for example, a single mobile phone or a PDA having a wireless communication function. Of course, a wired fixed terminal can be used as the receiving device. Also, the advertising window size during the period when the signal strength is weak is not limited to 0,
It should be set appropriately according to the required specifications.

Further, various determinations are made based on the radio wave intensity at a point in time. However, various determinations may be made by predicting the near future radio wave intensity based on the transition of the radio wave intensity. For example, only when the radio field intensity exceeding the threshold is continuously maintained for a predetermined time (or a predetermined number of times), T
You may make it restart CP communication. Of course, the user may instruct that the radio wave intensity has recovered, and restart TCP communication in accordance with the instruction.

Further, in the present embodiment, the example in which the transmission window size of the service node SN is changed by changing the advertisement window size on the premise of the data transfer by TCP has been described. When applied to transfer, it is also conceivable to employ another method suitable for the communication protocol of the application destination. In addition, the sliding window method is not only TCP, but also HDLC
(High level DataLinkControl), packet switching, etc.

<Second Embodiment> (1) System Configuration According to Second Embodiment FIG. 14 is a conceptual diagram showing a configuration example of a mobile communication system using a relay node TN according to a second embodiment of the present invention. ,
The mobile communication system shown in this figure is significantly different from the mobile communication system shown in FIG. 7 in that the base station BS and the service node SN are not the network NW but the relay node TN.
Is connected via the The base station BSa
The base station BSb and the base station BSb have the same function as the base station BS. Further, the relay node TNa and the relay node TNb are relay nodes having the same function, and hereinafter, when they are not distinguished from each other, they are simply referred to as relay nodes TN.

The base station BSa is connected to the relay node TNa via the local network LNa covering a relatively small area.
And the base station BSb is connected to the regional network L
It is connected to the relay node TNb via Nb. Further, each relay node TNa, TNb is connected to the service node SN via a wide area network GN covering a relatively wide area. That is, the relay node TNa
The mobile terminal MS accommodated in a subordinate base station (for example, the base station BSa),
a, the TCP segment is transferred from the service node SN via the relay node TNa and the wide area network GN. Similarly, the mobile terminal M accommodated in a base station (for example, base station BSb) under the relay node TNb
S receives the transfer of the TCP segment from the service node SN via the base station, the regional network LNb, the relay node TNb, and the wide area network GN. The local network LNa and the local network LNb
Since they have the same function, hereinafter, when they are not distinguished from each other, they are simply described as a regional network LN.

(2) Hardware Configuration of Relay Node TN FIG. 15 is a block diagram showing the hardware configuration of the relay node TN. In FIG. 15, reference numeral 3 denotes a communication unit, which is a subordinate base station via a local network LN. It communicates with the station BS and with the service node SN via the wide area network GN. The communication unit 3 communicates with another relay node TN via the wide area network GN.

Reference numeral 4 denotes a control unit for controlling the communication unit 3, which exchanges data with the communication unit 3. The control unit 4 includes a CPU 41 that performs various controls and calculations, and various programs and parameters (for example, ACK described later) read by the CPU 41.
Transfer delay time) and the like,
A work memory 43 used as a work area of the PU 41, a buffer 44 for the CPU 41 to temporarily save relay data from the service node SN to the mobile terminal MS, and a time interval controlled by the CPU 41 and set by the CPU 41 And a timer 45 for generating an interrupt signal. Various functions described later are realized by the CPU 41 executing various programs stored in the nonvolatile memory 42.

(3) Function of Relay Node TN (3-1) Overview Basically, the relay node TN transfers a TCP segment from the service node SN to the mobile terminal MS, and also transmits an ACK segment from the mobile terminal MS to the service node SN. , The size of the advertisement window in the ACK segment is extracted, and if this size is 0, the ACK
The transfer of the segment to the service node SN is delayed by an ACK transfer delay time, which is a predetermined fixed time, and the mobile terminal MS from the service node SN thereafter.
Buffer without forwarding the TCP segment to the mobile terminal MS, and then the advertisement window size becomes 0
, The buffered data (hereinafter, buffer data) is transmitted to the mobile terminal MS.

That is, the relay node TN delays the time when the service node SN receives the ACK segment for temporarily stopping the transmission of the TCP segment from the service node SN when the radio wave intensity is too weak, and The transmission of the TCP segment is made longer by the ACK transfer delay time as compared with the first embodiment, and the TCP segment transmitted during this time is buffered and transferred to the mobile terminal MS after the recovery of the radio wave intensity. Then, the mobile node MS operates so as not to notify the service node SN of the influence of the instantaneous decrease in communication quality (reduction in radio wave intensity) on communication. Also, by operating the relay node TN as described above, as a result, the radio field intensity when the communication between the mobile terminal MS and the service node SN is completely interrupted is lower than the radio field intensity in the first embodiment. Expected to be weak.

When the mobile terminal MS moves under the control of another relay node TN, the relay node TN transfers the buffer data up to that time to the other relay node TN, When the mobile terminal MS has its own relay node T
N, the mobile terminal M receives buffer data transferred from another relay node TN and moves to the mobile terminal M.
By transferring to S, it is possible to efficiently cope with a decrease in radio field intensity at the time of handover.

(3-2) Specific Functions Next, specific functions of the relay node TN will be described with reference to FIG. FIG. 16 is a block diagram showing a functional configuration related to relay control in the relay node TN. As shown in FIG.
A protocol processing unit TN1, a movement notification reception processing unit TN2,
TCP buffer TN3, retrieval condition inspection unit TN4, A
CK reception processing unit TN5, ACK transfer processing unit TN6, TC
P reception processing unit TN7, TCP transmission processing unit TN8, buffer transfer unit before movement TN9, and destination buffer reception unit TN
With 10. Although a processing unit related to the data link layer and a processing unit related to the physical layer exist between the IP protocol processing unit TN1 and the network (regional network LN / wide area network GN), they are not shown here. .

The IP protocol processing unit TN1 performs network layer transfer processing, and assembles and disassembles IP packets and assembles and disassembles movement notification packets and buffer data transfer packets described later.

The TCP buffer TN3 is the service node S
The TCP segment from N to the mobile terminal MS is temporarily stored for each TCP connection, and is constituted by a buffer 44 in FIG. In the present embodiment, the storage capacity of the buffer 44 can accommodate the maximum value of the ACK transfer delay time, the data transfer speed from the service node SN to the mobile terminal MS, and the delay time between the service node SN and the local relay node TN. Are set according to the number of mobile terminals MS.

When the IP protocol processing unit TN1 receives an IP packet from the network, the extraction condition inspection unit TN4 determines whether or not the IP packet satisfies a predetermined condition, and performs a process according to the determination result. In particular,
The extraction condition inspection unit TN4 extracts an advertisement window size from the IP packet, determines whether or not the advertisement window size is 0. If the advertisement window size is 0, extracts the IP packet and sends it to the ACK reception processing unit TN5. hand over. In the embodiment of the present invention, “to take out” an IP packet also means to stop the subsequent processing (through output to the network side) of the IP packet in the IP protocol processing unit TN1. . When the ACK reception processing unit TN5 sets a fetching condition described later, the fetching condition checking unit TN4 checks whether or not the IP packet from the service node SN to the mobile terminal MS satisfies the fetching condition. In this case, the IP packet is extracted and passed to the TCP reception processing unit TN7. In addition, the extraction condition checking unit TN4 in which the extraction condition is set indicates that the IP packet from the mobile terminal MS to the service node SN satisfies the extraction condition and the advertisement window size of the ACK segment included in the IP packet is not 0 Then, the IP packet is extracted and passed to the ACK reception processing unit TN5.

When the ACK reception processing unit TN5 receives the IP packet having the advertising window size of 0 from the extraction condition inspection unit TN4, the ACK reception processing unit TN5
The extraction conditions for the TCP connection from which the IP packet is extracted are set, and the IP packet is used as the ACK storage packet ASS in the work memory
3 is temporarily stored. Note that the extraction condition includes information designating the TCP connection, and the extraction condition inspection unit TN4 in which the extraction condition is set is used for the IP transmitted from the service node SN via the TCP connection specified by the extraction condition. At the same time as the packet is extracted, the IP packet transmitted from the mobile terminal MS via the TCP connection and having an advertising window size other than 0 is extracted. Further, when receiving the IP packet whose advertising window size is not 0 from the extraction condition checking unit TN4, the ACK reception processing unit TN5 reads the IP packet stored in the corresponding area of the TCP buffer TN3 and passes it to the TCP transmission processing unit TN8. A process of clearing the area, a process of canceling the extraction condition set in the extraction condition inspection unit TN4 for the corresponding TCP connection, and a process of extracting the extraction condition T
A process of passing an IP packet from N4 (an IP packet whose advertisement window size is not 0) to the ACK transfer processing unit TN6 is performed.

The ACK transfer processing unit TN6 measures the elapsed time from the time when the storage of the ACK storage packet ASS is started by using the timer 45, and when the elapsed time reaches the ACK transfer delay time, the corresponding ACK storage packet. The ACK is transferred to the service node SN via the IP protocol processing unit TN1 and the ACK storage packet A
Delete SS. Also, the ACK transfer processing unit TN6
The IP packet passed from the K reception processing unit TN5 is used as it is by the service node S via the IP protocol processing unit TN1.
Transfer to N

When receiving the IP packet from the extraction condition checking unit TN4, the TCP reception processing unit TN7
It is stored in the P buffer TN3.

The movement notification reception processing unit TN2 is a mobile terminal MS
From the relay node TN via the local network LN (notification that the mobile terminal MS has moved from the subordinate of the other relay node TN to the subordinate relay node TN) and the wide area network GN from the other relay node TN. (A packet notifying that the mobile terminal MS has moved from the subordinate of the own relay node TN to the subordinate of the other relay node TN), and the mobile terminal transmits these mobile notifications before the mobile terminal MS moves. Transfer to buffer transfer unit TN9.

The pre-migration buffer transfer unit TN9 performs processing according to the movement notification passed from the movement notification reception processing unit TN2. Specifically, if the movement notification is a movement notification from the mobile terminal MS, the pre-move buffer transfer units TN9 and TN9
The P protocol processing unit TN1 generates a movement notification packet including the movement notification, and transmits the movement notification packet to the relay node TN from which the mobile terminal MS has moved. If the movement notification is a movement notification from another relay node TN, the pre-migration buffer transfer unit TN9 reads out the IP packet stored in the corresponding area of the TCP buffer TN3, The protocol processing unit TN1
A buffer data transfer packet encapsulating the packet is generated and transmitted to the other relay node TN. In addition,
The buffer data transfer packet is an ACK packet of a movement notification packet, and is a TCP buffer TN.
Even when an IP packet is not stored in the corresponding area of No. 3, the packet is transmitted in a form in which an empty IP packet is encapsulated.

FIG. 17 is a diagram showing a part of the structure of a movement notification packet and a buffer data transfer packet. Both packets have a header having the structure shown in FIG.
(User Datagram Protocol) It is obtained by adding to the header of the packet. The added header includes an 8-bit type field, a 1-bit A, I, M, and G field, a 4-bit reserved bit field,
It has a 6-bit effective time field, a 32-bit long mobile terminal address field and a destination relay node address field, an ID field, and an extension field.

The type field is a field indicating a packet type, and in this embodiment, a value indicating that the packet is exchanged between the relay nodes TN is set.
The A field is a field indicating whether or not an ACK packet is required.
Is set. The I field is a field indicating the presence or absence of an ID field. The M and G fields indicate the packet encapsulation method.

The valid time field is a 16-bit field, and is used in this embodiment to set the valid time of the movement notification in the movement notification packet. In the present embodiment, if there is buffer data to be transferred even after the expiration of the valid time, the movement notification packet is transferred again. The ID field is a field for storing information capable of identifying a packet. However, in the ACK packet, the ID of the movement notification packet requesting this packet is stored in the ID field.

When the destination buffer receiving unit TN10 receives a buffer data transfer packet from another relay node TN via the IP protocol processing unit TN1, the destination buffer receiving unit TN10 extracts the IP packet contained in the buffer data transfer packet and transmits the TCP packet. Transfer to processing section TN8.

The TCP transmission processing unit TN8 transmits the IP packet passed from the ACK reception processing unit TN5 to the mobile terminal MS via the IP protocol processing unit TN1, and transmits the IP packet passed from the destination buffer receiving unit TN10 to the IP. The message is transmitted to the mobile terminal MS via the protocol processing unit TN1.

(4) Operation of Relay Node TN Next, the operation of the relay node TN having the above-described configuration and function will be described. However, here, the CP of the control unit 4
It is assumed that U41 executes various programs stored in the non-volatile memory 42 and realizes the functions shown in FIG. Also, it is assumed that the extraction condition has not been set in the extraction condition inspection unit.

(4-1) ACK-Compliant Operation FIG. 18 is a flowchart showing the flow of the ACK-compliant process executed by the relay node TN. As shown in FIG.
When the IP packet including the ACK segment is transmitted from the mobile terminal MS, the extraction condition inspection unit TN4 extracts the advertisement window size in the ACK segment, and determines whether or not the value is 0 (step). SF1, SF2). If the advertisement window size is not 0, the IP packet is not taken out and is transferred to the service node SN as it is (step SF3).

When the advertisement window size is 0, the IP packet is extracted by the extraction condition inspection unit TN4, and is temporarily stored in the work memory 43 as the ACK storage packet ASS by the ACK reception processing unit TN5 (step SF4). At this time, the measurement of the elapsed time from the time when the storage of the ACK storage packet ASS is started is started by the ACK transfer processing unit TN6 (step SF5), and the extraction condition in the TCP connection from which the IP packet is extracted is extracted. Set for the condition inspection unit TN4 (step SF
6). As a result, thereafter, until the extraction condition is released, the IP packet transmitted from the service node SN to the mobile terminal MS via the TCP connection is extracted by the extraction condition inspection unit TN4, and the TCP reception processing unit TN7 extracts the TCP packet. The data is stored in the buffer TN3 (buffering).

When an IP packet including an ACK segment is transmitted from the mobile terminal MS via the TCP connection when the buffering is being performed,
The extraction condition inspection unit TN4 extracts the advertisement window size in the ACK segment, and determines whether or not the value is 0 (steps SF7 and SF8). Here, if the advertisement window size is 0, the processing of the above-described steps SF4 to SF6 is repeated. If not, the IP packet is extracted by the extraction condition inspection unit TN4 and passed to the ACK reception processing unit TN5.

Then, the ACK reception processing unit TN5, which has received the IP packet whose advertisement window size is not 0, reads out the IP packet stored in the corresponding area of the TCP buffer TN3, and transmits the IP packet to the TCP transmission processing unit TN8 and the The data is transferred to the corresponding mobile terminal MS via the unit TN1 (step SF9). At this time, IP
The storage contents of the area of the TCP buffer TN3 from which the packet has been read are cleared, and the extraction condition set in the extraction condition inspection unit TN4 for the TCP connection is released. ACK reception processing unit TN
IP passed to 5, non-zero advertising window size
The packet is transferred to the service node SN via the ACK transfer processing unit TN6 and the IP protocol processing unit TN1. Thereafter, the process returns to step SF1.

(4-2) Delayed Relay Operation FIG. 19 is a flowchart showing the flow of the delayed relay processing executed by the relay node TN. The processing shown in FIG. As long as there is an ACK storage packet ASS that is being performed, the ACK transfer processing unit TN6 continuously performs the ACK storage packet ASS. That is, A
The CK transfer processing unit TN6 monitors whether or not there is an ACK storage packet ASS whose elapsed time from the storage start time has reached the ACK transfer delay time (step SG1). The ACK storage packet ASS to be transferred is transferred to the service node SN via the IP protocol processing unit TN1 and is deleted from the relay node TN (step SG2). That is, an IP packet having an advertisement window size of 0 is transmitted after being delayed by an ACK transmission delay time.

(4-3) Mobile-Aware Transmission Operation FIG. 20 is a flowchart showing the flow of the mobility-aware transmission process executed by the relay node TN. As shown in FIG. It is constantly monitored whether or not it has moved to the subordinate (step SH1). If it has moved, the buffered data is transferred to the destination relay node TN (step SH2). Mobile terminal M
When S moves under the control of another relay node TN, the mobile terminal MS does not directly receive a mobile notification, so that the mobile terminal MS receives the mobile notification packet from the destination relay node TN and performs the mobile Is determined to have occurred.
The movement notification packet from the transfer destination relay node TN is received by the movement notification reception processing unit TN2, and the movement notification in the packet is passed to the pre-migration buffer transfer unit TN9.
An IP packet corresponding to the movement notification is read from the TCP buffer TN3 by the buffer transfer unit TN9 before movement, and a buffer data transfer packet encapsulating the IP packet is transferred via the IP protocol processing unit TN1 to the relay node TN of the movement destination. Sent to

(4-4) Movement-Receiving Reception Operation FIG. 21 is a flowchart showing the flow of movement-reception reception processing executed by the relay node TN. As shown in FIG. It is constantly monitored whether or not there is a mobile terminal MS that has moved under the control of the own relay node TN (step SI1). Then, a process of transferring the data to the mobile terminal MS is performed (steps SI2 to SI4).

The determination as to whether or not there is a mobile terminal MS that has moved due to handover is made based on whether or not a movement notification has been transmitted from the mobile terminal MS. Mobile terminal MS
Is received by the movement notification reception processing unit TN2 (step SI).
1), transferred to the pre-migration buffer transfer unit TN9. The pre-migration buffer transfer unit TN9 generates a movement notification packet including the movement notification, and the IP protocol processing unit T
The data is transferred to the source relay node TN via N1 (step SI2).

When a buffer data transfer packet is transmitted from the source relay node TN in response to the movement notification packet, the buffer data transfer packet is
Destination buffer receiving unit T via protocol processing unit TN1
It is received by N10 (step SI3). The destination buffer receiving unit TN10 extracts an IP packet included in the buffer data transfer packet,
The IP packet is transmitted to the TCP transmission processing unit TN8 and the IP
The data is transferred to the mobile terminal MS via the protocol processing unit TN1 (step SI4).

(5) Operation of Mobile Communication System According to Second Embodiment Next, the operation of the mobile communication system using the relay node TN will be described with reference to FIG. FIG. 22 is a conceptual diagram showing an example of a data transfer flow in the mobile communication system. An example shown in FIG.
The mobile terminal MS performing data transfer with the N through the TCP connection is transmitted from the base station BSa to the base station BSb.
This is an example obtained by performing a handover to.

In a situation where the radio field intensity of the mobile terminal MS with respect to the base station BSa exceeds the threshold value, the T via the relay node TNa between the mobile terminal MS and the service node SN.
A CP connection is established, and a TCP is transmitted from the service node SN to the mobile terminal MS via the TCP connection.
When the segment (TCP data) is transferred, an ACK segment is transferred from the mobile terminal MS to the service node SN in response to the transfer. At this time, since the advertisement window size in the ACK segment is not 0, the relay node TNa does not participate in communication on the TCP connection at all.

Here, when the mobile terminal MS moves away from the base station BSa and the radio field intensity with respect to the base station BSa falls below the threshold value, as described in the first embodiment, the mobile terminal MS sets the advertisement window size to 0. Is transmitted to the service node SN. The IP packet including the ACK segment is extracted at the relay node TNa and is delayed by an ACK transfer delay time. An ACK segment with an advertising window size of 0 is a relay node T
While the IP packet including the TCP segment is transmitted from the service node SN to the mobile terminal MS even while being delayed by the ACK transfer delay time at the Na, the IP packet is extracted at the relay node TNa,
Buffered. An IP packet including an ACK segment with the advertisement window size set to 0 is ACK
After being delayed by the transfer delay time, the data is transferred from the relay node TNa to the service node SN, and the service node SN that has received the ACK segment has a transmission window size of 0, and the subsequent transmission is stopped.

In such a situation, when the mobile terminal MS approaches the base station BSb, the radio field intensity for the base station BSb exceeds the threshold value, and the handover from the base station BSa to the base station BSb is performed, the handover is performed. The indicated movement notification is transmitted from the mobile terminal MS to the relay node TNb. At this time, the TCP connection between the mobile terminal MS and the service node SN is changed to a connection via the relay node TNb.

Next, a transfer notification packet including the transfer notification is transferred from relay node TNb having received the transfer notification to relay node TNa, and a buffer data transfer packet (service node SN) corresponding to the transfer notification packet is transferred.
Is transmitted to the mobile terminal MS and the IP packet buffered in the relay node TNa) is transferred from the relay node TNa to the relay node TNb.

In the relay node TNb, the relay node TNa
Receives the buffer data transfer packet transferred from the server, and extracts the original IP packet from the buffer data transfer packet. The extracted IP packets are sequentially
The IP packet including the ACK segment is returned from the mobile terminal in response to the transfer to the mobile terminal MS. The return destination of the IP packet is the service node SN,
Since the advertisement window size in the ACK segment is not 0, the IP packet is transferred without involving the relay node TNa and received by the service node SN. The service node SN performs processing based on the advertisement window size in the ACK segment, and thereafter, transmission of the TCP segment is restarted.

When the signal strength is restored without performing the handover from the base station MSa to the base station MSb, the reception of the ACK segment (the ACK segment whose advertising window size is not 0) from the mobile terminal MS is triggered. , The buffered IP packet is transferred from the relay node TNa to the mobile terminal MS. of course,
At this time, the path of the TCP connection is not changed.
The ACK segment is directly transferred to the service node SN.

(6) Supplement on Second Embodiment As described above, according to the second embodiment of the present invention, not only the same effects as in the first embodiment can be obtained, but also
As a result, it is possible to lower the radio wave intensity when communication is completely interrupted, and to reduce the influence on the service node in a situation where the radio wave intensity decreases for a short time. For these reasons, according to the second embodiment of the present invention, the communication throughput can be further increased. The mobile communication system according to the second embodiment of the present invention can be modified in the same manner as in the first embodiment. Further, in the second embodiment of the present invention, the transfer of the ACK segment having the advertisement window size of 0 in the relay node TN is delayed by a certain time, but the present invention is not limited to this.
For example, it may be delayed by a time corresponding to the data transfer rate on the TCP connection, or if an untransmitted ACK segment remains in the relay node TN when the radio wave intensity exceeds the threshold, The ACK segment may be forcibly transferred from the relay node TN to the service node SN. Furthermore, it goes without saying that the invention is not limited to the embodiments described above,
It includes various aspects.

[0133]

As described above, according to the present invention,
The upper limit size of the window used on the transmission side in data transfer on the transport layer is determined based on the communication quality (for example, radio wave intensity) of a link (for example, a radio link) of a layer lower than the transport layer on the reception side. That is, window control is performed in consideration of not only the status of the transport layer but also the status of lower layers. Therefore, a more appropriate upper limit size can be set. For example, in data transfer in which the window size of the transmitting device changes in accordance with the delivery confirmation status, if the upper limit size is reduced when the communication quality of the lower layer link deteriorates, in an environment where packet loss is likely to occur, Can be suppressed, and a situation in which the window size becomes too small can be avoided.

In the receiving apparatus, when the communication quality of the lower layer is degraded, the received data is stored, and when the communication quality of the lower layer is restored, acknowledgment data corresponding to the received data is transmitted to the transmitting apparatus. That is, it is possible to reliably return the delivery confirmation data that is likely to be lost. This is an important effect in data transfer in which the window size of the transmitting device changes according to the delivery confirmation status.

As described above, in the present invention, it is possible to avoid a situation in which the window size used in the transmitting device becomes too small. This is especially true in a communication protocol having a function such as slow start. This has a remarkable effect when data transfer is performed via a wireless communication path. In such a case, the reduction in the window size causes a significant decrease in throughput in the subsequent communication over a long period of time. However, according to the present invention, such a problem is avoided because the reduction in the window size is suppressed. be able to.

Furthermore, according to the present invention, when the value of the upper limit size in the acknowledgment data transmitted from the receiving device to the transmitting device is small, the relay device transmits the acknowledgment data to the transmitting device. When the transfer is delayed and the data from the transmitting device to the receiving device is temporarily saved, and in this situation, when the delivery confirmation data including the large upper limit size is transmitted from the receiving device to the transmitting device, the temporarily saved data is deleted. Transferred to the receiving device. That is, the communication quality when communication is completely interrupted can be reduced as a result, and the influence on the transmission from the transmitting device is reduced in a situation where the communication quality is deteriorated only for a short time. Can be. Therefore, the communication throughput can be further increased.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a configuration of a segment which is a data transfer unit in TCP.

FIG. 2 is a conceptual diagram showing a communication image based on a sliding window method.

FIG. 3 is a conceptual diagram showing a conventional communication protocol configuration in data communication between a mobile terminal M and a service node SN.

FIG. 4 is a flowchart showing a flow of a TCP communication control process executed by the mobile terminal M.

FIG. 5 is a flowchart showing a flow of a TCP advertisement window control process executed by the mobile terminal M.

FIG. 6 is a block diagram showing a functional configuration related to wireless data link communication control that is not involved in data communication between the mobile terminal M and a base station.

FIG. 7 is a conceptual diagram showing a configuration example of a mobile communication system using the mobile terminal MS according to the first embodiment of the present invention.

FIG. 8 is a block diagram showing a hardware configuration of the mobile terminal MS.

FIG. 9 is a block diagram showing a functional configuration related to TCP advertisement window control in the mobile terminal MS.

FIG. 10 is a flowchart showing a flow of a TCP communication control process executed by the mobile terminal MS.

FIG. 11 is a flowchart showing a flow of a TCP advertisement window control process executed by the mobile terminal MS.

FIG. 12 is a flowchart showing a flow of a periodic process executed by the mobile terminal MS.

FIG. 13 shows a mobile terminal MS in the mobile communication system.
FIG. 4 is a conceptual diagram showing an example of an exchange between a service node SN and a service node SN.

FIG. 14 is a diagram illustrating a relay node T according to a second embodiment of the present invention.
FIG. 2 is a conceptual diagram showing a configuration example of a mobile communication system using N.

FIG. 15 is a block diagram illustrating a hardware configuration of the relay node TN.

FIG. 16 is a block diagram illustrating a functional configuration related to relay control in the relay node TN.

FIG. 17 is a diagram showing a part of the configuration of a movement notification packet and a buffer data transfer packet.

FIG. 18 is a flowchart illustrating a flow of an ACK-adaptive process executed by the relay node TN.

FIG. 19 is a flowchart illustrating a flow of a delay relay process executed by the relay node TN.

FIG. 20 is a flowchart showing a flow of a movement-adaptive transmission process executed by the relay node TN.

FIG. 21 is a flowchart showing a flow of a mobile reception processing executed by the relay node TN.

FIG. 22 is a conceptual diagram showing an example of a data transfer flow in a mobile communication system using the relay node TN.

[Explanation of symbols]

Reference Signs List 1 wireless unit 2, 4 control unit 3 communication unit 21, 41 CPU 22 non-updatable storage unit 23 updatable storage unit 24, 45 timer 42 non-volatile memory 43 work memory 44 buffer ASS ACK storage packet BS, BS1, BSa, BSb base Station BS11, M32 Beacon frame processing unit BS12, M35 Synchronization processing unit GN Wide area network L Base station list LN, LNa, LNb Regional network M, MS Mobile terminal M1, MS1, SN1 Transport protocol processing unit M2, SN2 Network protocol processing unit M3, SN3 Wireless data link processing unit M11, MS11 TCP segment reception processing unit M12, MS12 Advertisement window size determination unit M13, MS13 ACK transmission processing unit M21, SN21 IP protocol processing unit M31 SN31 Wireless link data processing unit M33 Base station list update processing unit M34 Optimal base station processing unit MS2 TCP advertisement window control processing unit for wireless link MS21 Signal strength inspection processing unit MS22 Received segment storage processing unit MS23 ACK information designation unit MS24 Advertising window size Designation unit MS25 Timer processing unit NW network SN Service node SN11 TCP segment transmission processing unit SN12 ACK segment reception processing unit SN13 Window update unit SS Saved packet TN, TNa, TNb Relay node TN1 IP protocol processing unit TN2 Movement notification reception processing unit TN3 TCP Buffer TN4 Extraction condition inspection unit TN5 ACK reception processing unit TN6 ACK transfer processing unit TN7 TCP reception processing unit TN8 TCP transmission processing unit TN 9 Buffer transfer unit before moving TN10 Buffer receiving unit to move to

Continued on the front page F term (reference) 5B089 GA25 GB01 GB02 HA11 HB02 JB22 KA12 KB10 KC52 MC02 5K030 GA03 HA08 HC09 JL01 LA08 LC03 5K033 AA02 CB06 CB14 CC01 DA01 DA19 5K034 AA05 BB06 DD02 EE03 FF10 H13 H13 H01 H13 BB10 DD DD44 DD51 EE02 EE10 GG11

Claims (22)

[Claims] 1. Receiving transport layer data transmitted from a transmitting apparatus that controls data transmission using a window whose size varies according to a transmission data delivery confirmation state within a notified upper limit size range. In the window control method in the receiving device, the communication quality of a link of a layer lower than the transport layer is obtained, an upper limit size is determined based on the communication quality, and the upper limit size is notified to the transmitting device. Window control method. 2. A transport layer data transmitted from a transmitting apparatus that controls data transmission using a window having a size that varies according to a transmission data delivery confirmation status within a notified upper limit size range. In the window control method in the receiving device, when receiving communication layer data transmitted from the transmission device during a period in which communication quality related to a link in a layer lower than the transport layer does not satisfy a predetermined criterion. A method of notifying the transmitting device of an upper limit size having a minimum value. 3. The window control method according to claim 2, wherein a start of a period in which the communication quality satisfies a predetermined criterion is detected, and after this detection, the upper limit size of a value larger than the minimum value is set in the transmission device. A window control method characterized by notifying to a window. 4. Receiving transport layer data transmitted from a transmission device that controls data transmission using a window whose size varies according to a transmission data delivery confirmation status within a notified upper limit size range. In the window control method in the receiving device, when the communication quality of the link of the layer lower than the transport layer does not satisfy the preset criterion, when the data of the transport layer transmitted from the transmitting device is received, Detecting the end of a period in which the communication quality does not satisfy a preset criterion, and transmitting the information indicating the delivery of the data stored in the storing step after the detection. And transmitting an acknowledgment to the device. 5. The window control method according to claim 4, wherein the communication quality is periodically acquired to detect the end of the period. 6. The window control method according to claim 1, wherein the receiving device is a mobile radio terminal, the link is a radio link, and the communication quality is radio field intensity. Window control method. 7. Receiving transport layer data transmitted from a transmitting apparatus that controls data transmission using a window whose size varies according to a transmission data delivery confirmation state within a range of a received upper limit size. A communication quality acquiring unit for acquiring communication quality related to a link of a layer lower than a transport layer, based on the communication quality acquired by the communication quality acquiring unit. An upper limit size determining unit that determines the upper limit size, and a transmission acknowledgment transmitting unit that transmits the upper limit size determined by the upper limit size deciding unit to the transmitting device while including the upper limit size in the acknowledgment data. Receiving device. 8. The receiving apparatus according to claim 7, further comprising: a reference determining unit that determines whether a communication quality acquired by the communication quality acquiring unit satisfies a preset standard. The determining unit may further determine a preset minimum value as an upper limit size when the reference quality determining unit determines that the communication quality acquired by the communication quality acquiring unit does not satisfy a preset standard. A receiving device characterized by the above-mentioned. 9. The receiving apparatus according to claim 8, wherein the acquisition trigger control unit that controls the communication quality acquisition unit to periodically acquire the communication quality, and the acquisition trigger control unit based on a determination result by the reference determination unit. A recovery detection unit that detects a start of a period in which communication quality satisfies a preset criterion, wherein the upper limit size determination unit further detects the start of the period by the recovery detection unit from the minimum value. A receiving device for determining a large value as an upper limit size. 10. Receiving transport layer data transmitted from a transmission device that controls data transmission using a window whose size varies according to a delivery confirmation status of transmission data within a range of a received upper limit size. A communication quality acquiring unit for acquiring communication quality related to a link of a layer lower than a transport layer, and a communication quality acquired by the communication quality acquiring unit. Based on the set criterion, a degradation period determination unit that determines whether the communication quality is within a period that does not satisfy a preset criterion, and the degradation period determination unit determines that the communication quality is within the period. A storage acknowledgment processing unit that stores the data of the transport layer transmitted from the transmitting device during the period of time, A recovery detecting unit that detects a start of a period in which the communication quality satisfies a predetermined criterion based on the communication quality acquired by the communication quality acquiring unit and a preset criterion, The receiving apparatus further comprising: when the recovery detecting section detects the start of the period, the processing section transmits acknowledgment data according to the data stored in the storage section to the transmitting apparatus. 11. The receiving device according to claim 10, further comprising: an acquisition trigger control unit that controls the communication quality acquiring unit to periodically acquire the communication quality. 12. The receiving device according to claim 7, further comprising: a wireless communication unit configured to receive transport layer data transmitted from the transmitting device via a wireless communication network, wherein the link includes: A receiving apparatus, wherein the receiving apparatus is a wireless link, and the communication quality is a radio field intensity in the wireless link. 13. The receiving apparatus according to claim 12, wherein a radio wave intensity storage unit storing information indicating the radio wave intensity of the wireless link, and constantly monitoring the radio wave intensity of the wireless link, and according to the monitoring result. A radio wave intensity monitoring unit that sequentially updates information stored in the storage unit, wherein the communication quality obtaining unit obtains the radio wave intensity of the link by reading the information from the radio wave intensity storage unit. Receiving device. 14. A data transfer method for transmitting data of a transport layer from a transmission device to a reception device using a window whose size varies according to a transmission data delivery confirmation status, wherein reception in a layer lower than the transport layer is performed. A data transfer method comprising: a receiving-side communication quality obtaining step of obtaining communication quality of a side link; and a size determining step of determining the size in consideration of the communication quality obtained in the communication quality obtaining step. Method. 15. A transmission apparatus for controlling data transmission using a window whose size varies according to a transmission data delivery confirmation state within a range of a received upper limit size, and a transport layer transmitted from the transmission apparatus. Transfers data to and from a receiving device that receives data and returns the upper limit size based on the communication quality related to the link of a layer lower than the transport layer in the delivery confirmation data to the data of the transport layer. In the relay control method in the relay device, when the value of the upper limit size in the acknowledgment data transmitted from the receiving device to the transmitting device is small, the transfer of the acknowledgment data to the transmitting device is delayed and the transmission is performed. The data from the device to the receiving device is temporarily saved, and in this situation, the acknowledgment data including the large upper size is stored in the receiving device. Relay control method characterized by transferring the temporarily saved data to the receiving device when it is sent to the Luo the transmitting device. 16. The relay control method according to claim 15, wherein the receiving device is a mobile wireless terminal, the link is a wireless link, the communication quality is a radio wave intensity, and the receiving device is another relay. A relay control unit that transfers temporarily saved data to the other relay device when receiving the data under the control of the device, receives data transferred from the other relay device, and transfers the data to the receiving device; Method. 17. The relay control method according to claim 15, wherein, when the upper limit size of the acknowledgment data transmitted from the receiving device to the transmitting device is small, the acknowledgment data is transmitted to the transmitting device. A relay control method characterized by delaying the transfer of a message by a certain time. 18. The relay control method according to claim 16, wherein when the receiving device moves to another relay device, the temporarily saved data is transferred to the other relay device and the transfer is delayed. Transferring the received unacknowledged acknowledgment data to the transmitting device. 19. A transmission apparatus for controlling data transmission using a window whose size varies according to a delivery confirmation status of transmission data within a range of a received upper limit size, and a transport layer transmitted from the transmission apparatus. Transfers data to and from a receiving device that receives data and returns the upper limit size based on the communication quality related to the link of a layer lower than the transport layer in the delivery confirmation data to the data of the transport layer. A temporary storage unit for temporarily storing data, an upper limit size extracting unit for extracting an upper limit size from acknowledgment data transmitted from the receiving device to the transmitting device, and an upper limit size extracting unit. An inspection unit that determines the size of the upper limit size obtained, and an upper limit size when the inspection unit determines that the upper limit size is small. A delay processing unit that delays acknowledgment data including a delay before transferring the data to the transmitting device; and, when the inspection unit determines that the upper limit size is small, temporarily transfers data from the transmitting device to the receiving device. An evacuation processing unit that starts evacuation processing to be stored in the storage unit; and if the upper limit size is determined to be large by the inspection unit in an environment in which the evacuation processing is being performed, the evacuation processing unit starts the evacuation processing. A relay device comprising: a recovery processing unit that transfers data stored in a temporary storage unit to the receiving device and ends the saving process. 20. The relay device according to claim 19, further comprising: a mobile-compatible receiving unit that receives data transferred from another relay device and transfers the data to the receiving device, wherein the receiving device is a mobile wireless terminal. Yes, the link is a wireless link, the communication quality is radio wave intensity, the recovery processing unit, when the receiving device moves to another relay device under the environment where the evacuation process is performed Wherein the data stored in the temporary storage unit is transferred to the other relay device from the start of the evacuation process. 21. The relay device according to claim 19, wherein the delay processing unit delays acknowledgment data including the upper limit size by a predetermined time when the inspection unit determines that the upper limit size is smaller. A relay device that transfers the data to the transmission device after the transmission. 22. The relay device according to claim 20, wherein the recovery processing unit is configured to, when the receiving device moves to a position under another relay device in an environment where the evacuation process is performed, From the start of the evacuation process, the data stored in the temporary storage unit is transferred to the other relay device, and the untransferred acknowledgment data whose transfer has been delayed is transferred to the transmitting device. Relay device.