JP3454998B2 - Communications system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to packet communication, and more particularly, to a packet communication system that supports multimedia for performing voice, image and data communication.

[0002]

2. Description of the Related Art TC is a transport layer protocol used when communication is performed between terminals such as computers.
There is a protocol called P (Transmission Control Protocol). In this TCP, the terminal that received the data
Error control is performed by returning a delivery confirmation response to the terminal that transmitted the data.

FIG. 5 shows an example of TCP behavior when data is downloaded to an application between terminals connected by Ethernet with a transmission rate of 10 Mbps. In this example, workstation 1 is workstation 2
And TCP are connected, the data is downloaded, and the response is sent by workstation 1 to workstation 2.
It shows how it is returned to. Also, TCP uses window control as flow control.

In FIG. 5, as an example, let us say that the window size is "8760" bytes. That is, the capacity of the reception buffer of the workstation 1 is “876
In Ethernet, the maximum packet length that can be transmitted at one time is “1500” bytes,
Usually, "1460" bytes obtained by subtracting the overhead "40" bytes of TCP / IP (Internet Protocol) is the amount of data that can be sent in one transmission.

The workstation 2 divides the data to be transmitted to the workstation 1 into "1460" bytes at the TCP layer and divides the data in one packet into "1460".
Send to workstation 1 as bytes. At that time, the window size, which is the number of bytes that can be transmitted without a response from the workstation 1, is managed by reducing the window size by the number of transmitted bytes.

In this example, since the window size of the workstation 1 is set to "8760", the number of bytes that the workstation 2 can transmit is "8760" minus the data amount "1460" bytes in one packet. This will be "7300" bytes. In this way, the workstation 2 reduces the number of bytes that can be transmitted each time data is transmitted to the workstation 1.

The workstation 1 on the receiving side stores the received data in the receiving buffer once, confirms that the correct data is received, and fetches the data from the receiving buffer into the application. Confirm the delivery of the captured data and the window size equivalent to the free space of the receive buffer that was generated by the workstation 2
As a response to.

When the workstation 2 receives the response from the workstation 1, from the window size information included in the response, the workstation 2 sets the size as the receivable byte, and the workstation 2 determines its own transmittable byte number. Update by the number of receivable bytes. In FIG. 5, since the value of the receivable byte number received is “8760” bytes, the workstation 2 will reset the window size to the initial value.

As shown in FIG. 5, a single response is returned to the data transmitted by a plurality of packets, so that the workstation 1 can send a response to each packet rather than a response. Communication that makes effective use of the transmission path to the workstation 2 can be performed.

By the way, in TCP, in order to control the timing of returning a response, a timer for instructing a transmission process of the response is provided at regular intervals to control the timing of the response. That is, as shown in FIG. 6, when the workstation 1 receives the data DT1, it sets a flag indicating a transmission confirmation waiting state. When data to be sent to the workstation 2 occurs, the data is packetized together with the data and a response is transmitted. However, if a response transmission process is instructed by the above-mentioned timer before the data to be transmitted to the workstation 2 occurs, only the delivery confirmation is packetized and the response is transmitted.

However, when the workstation 1 receives the packet transmitted from the workstation 2 and transmits the response at the timing shown in FIG. 6, the response transmitted by the workstation 1 has a slow transmission speed. The data having the same size as the window size is transmitted to the station 2 side and is received after a while.

At this point, the number of bytes that can be transmitted by the workstation 2 is updated for the first time. Therefore, the number of bytes that can be transmitted by the workstation 2 is not updated between the time when the workstation 2 finishes transmitting the data of the same size as the window size and the time when the response from the workstation 1 is received. There is a dead time in that no data is transmitted.

The communication using TCP as described above is applied to wired communication. In recent years, with the progress of wireless communication technology, the reduction in size and weight of terminals, and the spread of multimedia communication, A wireless communication system is desired so that multimedia communication can be performed anywhere.

For that purpose, it is desired that the portable terminal be downsized and consume less power. High-speed wireless transmission requires a high carrier frequency, a large high-frequency circuit, and high power consumption. Therefore, a mobile terminal that has an application that only receives a large amount of data and that does not send a large amount of data has a low transmission rate of transmission by a wireless channel.
A wireless system that communicates through a bidirectional wireless channel, which has a high transmission speed for reception by a wireless channel, is suitable.

FIG. 11 shows the behavior when the conventional TCP is mounted on such an asymmetric wireless channel having different upstream and downstream transmission rates. Workstation 2
The packet is received from and the response is transmitted at the same timing as in FIG.

In this case, the response message transmitted from the work station 1 is delayed in arriving at the work station 2 due to the slow transmission rate of the upstream channel. Therefore, the number of bytes that can be transmitted by the workstation 2 is not updated, which causes a time during which no data is transmitted. When the workstation 1 tries to transmit the second response, the first channel response is still being transmitted and cannot be sent because the transmission speed of the uplink channel is low.

Then, the second response is received with a further delay. Then, the state in which no data is transmitted becomes longer. In other words, it takes a very long time to receive the data.

[0018]

As described in the conventional example, in TCP (Transmission Control Protocol), the timing of returning a response is managed by a timer, and the response to the packet reception from the transmitting side is returned. A response will be returned at the timing after all packets have been sent on the sending side. In this case, no data can be sent until the response is received after sending all packets. There was a problem that it wasted time and it took time to transfer data.

With the spread of communication systems using portable intelligent wireless communication terminals, it is considered to use TCP for the wireless communication system. If you apply it to a wireless communication system where the transmission speed of the downlink wireless channel and the transmission rate of the downlink wireless channel are different, the data will not be transmitted at all. There is a problem in that the power consumption of a portable intelligent wireless communication terminal used as a power source is wasted, resulting in poor usability.

Therefore, the object of the present invention is to
When a packet is received, by controlling the receiving side to send back a response to the transmitting side as soon as possible, a packet communication system capable of efficiently transmitting data by eliminating the dead time in which the transmitting side cannot transmit data at all To provide.

[0021]

In order to solve the above problems, according to the present invention, the transmitting side is provided with information on the window size, which is the remaining receiving buffer capacity of the receiving side, and this window is used for packet transmission. It is a packet communication system that uses the size information to continue the transmission by the receivable capacity of the receiving side, the transmission rate of packets from the transmitting side is high, and the transmission rate of the response returned from the receiving side. In a low-speed communication system, the receiving side returns an acknowledgment containing information on the window size vacated by the receiving side from the receiving side to the transmitting side in time so that the window size does not become insufficient. It is characterized in that it is configured so as to update its own window size for information.

In a packet communication system for transmitting and receiving data in packets, the amount of data that can be continuously transmitted from the first terminal to the second terminal without waiting for delivery confirmation is below a certain threshold. The basic idea is that the second terminal returns a delivery confirmation when it reaches the threshold, and the threshold value is set to the transmission speed of the first terminal and the time required to transmit the delivery confirmation of the second terminal. The gist is to take the product of and.

Further, in the communication system in which the transmission rate of the wireless channel for communicating from the base station to the mobile terminal is higher than the transmission rate of the wireless channel for communicating from the mobile terminal to the base station, Error-free data (for applications that display data on the display of a mobile terminal or play sound on the speaker of a mobile terminal) by downloading data using a bidirectional wireless channel with different wireless channel transmission rates In the transport layer for providing the response, when the product of the response data length of the mobile terminal and the response data length is λ and the transmission rate of the uplink wireless channel is μ, the response of the response is set so that λ / μ becomes 1 or less. Characterized by determining the frequency of return. Further, when the sum of the response interval of the mobile terminal and the response transmission time is T, the reception buffer of the mobile terminal is larger than the product of T and the transmission rate of the downlink wireless channel. To do.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, while using TCP, it is possible to continue the transmission without a long time from the sender side, and as in the conventional case, the transmission is continued until the arrival of the acknowledgment. In order to eliminate the occurrence of such a situation, packet transmission can be efficiently performed in asymmetric communication, and time and communication resources can be effectively used. The present invention will be described below with reference to the drawings. A specific example will be described.

(First Specific Example) FIG. 1 is a system configuration diagram according to the present invention, and FIG. 2 shows a workstation in which the system shown in FIG. 1 is installed and a workstation connected to the workstation through a communication path. An operation diagram is shown in the system configuration diagram and FIGS. 3 and 4.

FIG. 1 is a block diagram showing the structure of a packet transmission / reception system. Reference numeral 4 is a transmission processing device for controlling packet transmission processing, 5 is a reception processing device for controlling packet reception processing, and 7 is a reception window size. A receiving window size storage device for storing information. The reception processing device 5
Packet reception processing means 21, determination means 22, STT (Sin
gle Trip Time) calculating means 23 and threshold value calculating means 24.

The packet reception processing means 21 performs packet reception processing, and the determination means 22 compares the current window size value with the vacant window size value which must be notified when transmitting the delivery confirmation. To do. The threshold value calculation means 24 determines a window size value (delivery confirmation threshold value) at which the acknowledgment must be transmitted. It calculates the time it takes to send information (single trip time).

FIG. 2 is a system configuration diagram in which FIG. 1 is applied to a workstation. 1 and 2 are workstations, 3 is transmitting / receiving means of the workstation 1, 10 is transmitting / receiving means of the workstation 2, and 5 is receiving. A processing means, 6 is a timer for time management to secure a timing for returning an acknowledgment when receiving a packet, 7 is a reception window size storage means for storing a value of a reception window size, and 8 is a transmission A transmission window size storage means for storing a window size value, a transmission processing device 9 for controlling packet transmission processing, and a reception processing device 11 for controlling packet reception processing. The reception processing device 11 also has the same configuration as the reception processing device 5 in FIG.

In FIG. 2, when the workstation 1 on the receiving side receives the data from the workstation 2 on the transmitting side, a TCP response is used as a delivery confirmation. The length of the TCP / IP response packet is 40 bytes [byte]. At this time, the receiving window size is 10 × 10 ⁶ / in an asymmetrical transmission path in which the transmission rate from the transmission side to the reception side is 10 [Mbps] and the transmission rate from the reception side to the transmission side is 32 [Kbps]. 32 x 10 ³ * (40 x
8) The delivery confirmation may be transmitted when the value obtained by adding "certain value A" to the bit = 12500 bytes is reached.

In FIG. 3, the window size is "1742".
The work station 2 sends data to the work station 1 in units of "1460" bytes, and the work station 1 receives the data.
The workstation 2 reduces the window size, which is the number of bytes that can be transmitted without a response from the workstation 1, by the number of transmitted bytes.

The window size, which is the number of bytes that can be received on the receiving side, is also reduced by the number of received bytes. When the window size reaches a value (“12500” + A) obtained by adding “certain value A” to “12500” bytes, the reception window size is transmitted to the workstation 2, which is the transmission side, together with the delivery confirmation.

Upon receiving this delivery confirmation, the workstation 2 updates the transmission window size with the reception window size included in this delivery confirmation packet as an available capacity. By updating the transmission window size, the workstation 2 can transmit more data. That is, by replacing the above free space with the current transmission window size, the transmittable window size increases, so that packets can be continuously transmitted until the transmittable window size is exhausted.

As described above, in the workstation 1 on the receiving side, every time the window size reaches "12500" + A due to the reception of the received data , the receiving window size is confirmed together with the delivery confirmation, and the workstation on the transmitting side. By repeating the transmission to the workstation 2, the workstation 2 can continue to transmit the data to the workstation 1 without any interruption.

Next, the operation will be described with reference to FIGS. 1, 2 and 4.

Assume workstation 2 has data to be sent to workstation 1. In this case, the workstation 2 divides the data, packetizes it, and transmits the data to the workstation 1 through the transmitting / receiving means 10 within a range where the window size of the workstation 1 has a spare capacity (S201 and S20 in FIG. 4).
2, S203).

Then, the transmission processing means 9 in the workstation 2 subtracts the value of the transmission window size in the transmission window size storage means 8 by the number of bytes of data (S204 in FIG. 4). After that, if there is data to be transmitted, this operation is repeated until the window size becomes “0”.

The workstation 1 is in the state of waiting for packet reception (S101 in FIG. 4), and when the packet transmitted from the workstation 2 is received by the transmitting / receiving means 3 (S102 in FIG. 4), whether there is data in the packet. Confirm (S103 of FIG. 4). When there is data in the packet, the packet reception processing means 21 in the reception processing means 5 subtracts the reception window size stored in the reception window size storage means 7 by the number of bytes of the data (FIG. 4).
S104). Then, let this be the current window size (CW).

The determination means 22 in the reception processing means 5 of the workstation 1 reads the value CW of the current window size from the window size storage means 7, and the delivery confirmation transmission threshold calculated by the threshold value calculation means 24. The value W is read and it is determined whether or not the value CW of the current window size is smaller than the delivery confirmation transmission threshold W (S10 in FIG. 4).
5). As a result, when it is small, a signal corresponding to the delivery confirmation transmission request is transmitted to the transmission processing means 4. The transmission processing means 4 transmits to the workstation 1 a response packet accompanied by a delivery confirmation for updating the reception window size (S106 in FIG. 4).

The workstation 2 which has received the response packet for updating the window size through the transmitting / receiving means 10 updates the value of the transmission window size in the transmission window size storage means 8 to the value transmitted from the workstation 1 (FIG. 4 S205).

As a result, in the workstation 2 on the transmitting side, the transmission window size becomes "0", and before the data cannot be transmitted to the workstation 1, the transmission window size is updated to the window size. Since there is always a margin, data transmission will not be delayed. Therefore, the transmission path can be effectively used.

Next, a method for obtaining the time required for the workstation 1 to transmit 1-bit information will be described.

1 / V where V is the upstream transmission rate
And

When the upstream transmission rate is V1, the downstream transmission rate is V2, and the round trip time is RTT,
V2 × RTT / (V1 + V2)

When the upstream transmission rate is sufficiently lower than the downstream transmission rate, STT = RTT.

The round trip time when a packet of a [bit] is sent from the workstation 2 and a delivery confirmation packet of c [bit] is received is RTT1, and a packet of b [bit] is sent from the workstation 1 to d. Round trip time when receiving the response packet of [bit] is RT
When T2 is set, (d * RTT1-c * RTT2) / (ad-bc) As a result, it becomes possible to make a setting suitable for the system state.

TCP has a function of transmitting a response by using a timer as a means for controlling the timing of returning the response. This timer interrupts every 200 [ms], and if it is in a state to be transmitted, it will instruct the transmission. Here, the following choices can be made for this timer.

That is, [1] Do not use the timer.

[2] Use a timer. Is one of.

When the above [1] is selected, it is possible to avoid sending an unnecessary response by not using the timer. When [2] is selected, a timer can be used to send a response even if a large amount of data is not transmitted from the workstation 2 and the reception window size does not decrease.

As described above, in the first specific example, data is packet-transmitted from the transmission side to the reception side through a communication path capable of high-speed transmission,
When the receiving side returns a confirmation response for packet reception together with the window size information to the transmitting side using a communication path with a slow transmission rate, the receiving side satisfies the window size which is the buffer capacity that the received data can receive. The reception window size is transmitted to the transmission side together with the delivery confirmation at a timing before the window size of the transmission side does not become zero at the time when the acknowledgment arrives at the transmission side. The transmission side can continue to transmit data to the reception side without any delay, and it is possible to efficiently transmit data.

Therefore, according to the present invention, in packet communication in which TCP is used as a protocol and an asymmetrical communication path is used as a transmission path, it is possible for the transmitting side to continue transmitting data to the receiving side without interruption. As a result, data can be efficiently transmitted.

Although all the examples of wired and wireless communication have been described above, an example of application to wireless communication using an asymmetrical transmission path for upstream and downstream transmission rates will be described as a second specific example.

(Second Specific Example) This specific example is optimally applied to packet communication using a mobile terminal, and particularly to a packet communication system for receiving multimedia services such as communication of voice, image, and data. Here is an example.

In this specific example, asymmetric wireless communication is targeted, and in the transport layer thereof, λ is the product of the response frequency of the mobile terminal and the response, and λ is the transmission rate of the uplink wireless channel. / Μ is 1 or less, the frequency of the response is determined, and when the sum of the time interval for the response of the mobile terminal and the transmission time of the response is T, the reception buffer of the mobile terminal is T It should be larger than the product of channel transmission rates.

A system configuration diagram of this specific example is shown in FIG. In the figure, 601 is a narrow band base station, 602 is a mobile terminal, 603 is a wide band base station, and 604 and 605 are service areas.

Although the narrow band base station 601 has a low transmission rate,
Since a relatively low frequency can be used, the service area, which is an area in which communication is possible, is wide, and communication can be performed with low power. In addition, the broadband base station 603 uses a high frequency,
Therefore, although the transmission speed is high, the service area is narrow and the power consumption is large.

The narrow band base station 601 performs bidirectional communication with the portable terminal 602 at a transmission rate of 32 Kbps, and the portable terminal 602 receives 10 from the broadband base station 603.
Data such as images and voices are received at a transmission rate of Mbps. Service area 60 formed by narrowband base station 601
4 is a service area 6 formed by the broadband base station 603.
Greater than 05, the coverage area 605 of the broadband base station 603 is included in the coverage area of the broadband base station.

The mobile terminal 602 makes a data request on the radio channel of 32 [Kbps], and the narrow band base station 6
01 to the server 607 in the network 600. The requested data is transmitted to the mobile terminal 602 via the broadband base station 603.

FIG. 9 shows a protocol stack for communication between the portable terminal 602 and the server 607. Mobile terminal 602
Has a radio part (RF) for 32 [Kbps] transmission / reception and a radio part (RF) for 10 [Mbps] reception in the physical layer. The second layer has a data channel of a radio channel of 32 [Kbps] and a data channel of a radio channel of 10 [Mbps]. The third layer uses IP (Internet Protocol) in this specific example.

The transport layer is modified by TCP (T) modified to be suitable for wireless communication in which transmission and reception are asymmetric.
transmission control Proto
col) is R-TCP.

The narrow band base station 601 is 32 [Kbps].
Has a data link with a wireless part for transmission / reception, and has a physical layer having Ethernet for connecting to the network 600, and uses a data link layer standardized by IEEE802.3. The data link is used for protocol conversion between the wireless part and the Ethernet part. The broadband base station 603 has a data link with a wireless part of transmission and reception of 10 [Mbps], has a physical layer having Ethernet for connecting to a network, and has a data link layer with I
Use the one standardized in EEE802.3. Also, the protocol conversion between the wireless part and the Ethernet part is
Data link.

In such a wireless communication system, when the portable terminal 602 receives data from the broadband base station 603, TCP "Ack (acknowledgement)" is confirmed as a delivery confirmation.
To use. The length of TCP “Ack” is “40” bytes including the header length of the network layer.

At this time, the portable terminal 602 sets the TCP "A"
The frequency of returning "ck" is 32000 / (40 *
8) = 100 times or less. At this time, the response transmission time is "0.01" seconds, and the response return time interval is "0.01" seconds.

In this case, the reception buffer is "(0.01+
0.01) × 10,000,000 = 200000 ″ bits.

When such parameters are set,
The behavior of R-TCP will be described with reference to FIG. Server 60
It is assumed that the workstation 2 is used as 7 and the workstation 1 is used as the mobile terminal 602. Workstation 2 is workstation 1
The data to be transmitted to the server is divided into "1460" bytes in the TCP layer, TCP and IP headers are added, and one packet is packetized as "1500" bytes, and the network 600 wirelessly transmits this via the broadband base station 603. By doing so, it is transmitted to the workstation 1.

[0066] At this time, the window size is the number of bytes that can be sent without a response from the workstation 1, gradually decrements byte Dzu that sent. In this case, the window size of workstation 1 is "20,000
Since it is set to 0 bit, that is, "25000" bytes, "1460" is subtracted from the number of bytes that can be transmitted by the workstation 2 to obtain "23540" bytes. The window size is set to "22080" bytes by subtracting "1460" bytes of packet data from "23540" bytes.

As described above, the workstation 2 sets the number of transmittable bytes to "1460" each time data is transmitted.
Reduce by bytes.

On the other hand, in the workstation 1, the application fetches the data, and when the built-in timer of the workstation 1 measures a predetermined time, it returns a confirmation response.

If the application fetches the received data of three packets at the stage of receiving three packets, the amount is "4380" bytes. Then, by receiving this "4380" bytes, the receiving buffer becomes all empty, and "25000" bytes become full. The response at this stage is "2500" which is an acknowledgment that indicates that up to the third packet has been received.
This is a notification of the window size value of 0 "bytes, which is sent to the narrow band base station 601 using the low speed transmission line.
This information is sent to the network 6 via the narrow band base station 601.
00, and is given to the workstation 2 from the network 600, the workstation 2 will update the value of the window size as follows.

That is, as shown in FIG. 8, assuming that the workstation 2 has transmitted the eleventh packet up to this stage, the window size is "104".
It is 00 ”bytes and is still“ 10400 ”at this stage
It is ready to send bytes. Then, "2500" from the workstation 1 received together with the confirmation response
Although it is a 0 "byte, the confirmation response has been received up to the third packet, and the workstation 2 side has not confirmed the fourth and subsequent packets. The total data amount of the 4th to 11th packets is “11680” bytes (“1460” bytes × 8 packets = “116”).
80 "bytes).

Therefore, when the 11th data arrives from the workstation 2 side to the workstation 1 side, the free space of the receiving buffer on the workstation 1 side is the case where the application does not take out any data from the receiving buffer. "25000"-
It is estimated that “11680” = “13320” bytes.

Then, on the workstation 2 side, the window size is updated to "13320" bytes.

As a result, the window size of the workstation 2 is from "10400" bytes to "1332".
It becomes 0 "bytes.

In this way, the window size is set to "2.
Workstation 1 with 5000 "bytes
The window size is prevented from becoming "0" during the time until the confirmation response from (1) arrives so that the workstation 2 can continuously transmit data.

After the first response is returned, the next confirmation response is generated again when a predetermined time has elapsed. This is the response indicated by reference numeral 101 in FIG. By this stage,
The workstation 2 transmits 8 packets, consumes the window size of “11680” bytes, and remains “1160”. The window size “3100” immediately before the response 101 in FIG. 8 is the value immediately before the transmission of the 19th packet.

At this time, if the confirmation response from the workstation 1 is returned together with the information that the window size is "25000" bytes, since the confirmation response for 8 packets has not been obtained, the amount is "11680" bytes. Yes, at this stage, the window size on the workstation 2 side is updated to "13320" bytes ("25000"-"11680" = "13320" bytes), and transmission of "13320" bytes is possible. Become. In this way, the workstation 2 side can continue data transmission without interruption.

As described above, by giving a margin to the window size (receivable buffer capacity) of the workstation 1 on the receiving side, the confirmation response periodically returned from the workstation 1 on the receiving side at the time of data reception. At the stage of receiving the message, the workstation 2 on the sending side updates the window size by the window size returned together with the confirmation response, so that the window size can be updated before the shortage occurs. 2 can send data. Also, the interval at which the workstation 1 returns a response is calculated from the upstream transmission rate and the data length of the response, so there is no possibility that the previous response is being transmitted and the next response cannot be transmitted.

Next, the configuration of this system and the configuration of the terminal will be described with reference to FIG.

The terminal (Terninal) is a narrow band base station 601.
(PS) which communicates with (CS)
Station) and a PU (SDL Receiver U) that receives a transmission from the broadband base station 603 (TU).
nit) and SD that integrates these two wireless channels
L TA (SDL Network Adapter)
And a display / input / output unit.

The narrow band base station 601 (CS) is a PBX.
When connected to a (private branch exchange) and performing data communication (multimedia communication), the network adapter S
A line is connected to the DLNA. In the case of only voice call, the PBX connects the line with PSTN / ISDN. S
DLNA uses a broadband base station 603 to transfer data from the LAN.
(TU). Further, the SDLNA transmits a "search request" coming from the narrowband base station 601 (CS) to the LAN.

The terminal (Terninal) receives the packet sent from the high bandwidth base station 603 (TU) using the high speed line (SDL) via the reception buffer, and the confirmation response is low power and slow. It is sent using a line (NDL), received by the narrow band narrow band base station 601 (CS), and given to the LAN by the PBX.

At this time, by performing the control as described above,
Before the reception buffer of the terminal (Terninal) becomes full, and moreover, it becomes possible to perform wireless transmission while updating the window size so that the transmission from the LAN side to the terminal (Terninal) is not interrupted. Moreover, it can be implemented without causing unnecessary consumption of electric power.

Various concrete examples have been described above. In short, according to the present invention, the window size information, which is the remaining receiving buffer capacity of the receiving side, is given to the transmitting side, and this window size information is transmitted when the packet is transmitted. TC which is used to continue transmission for the amount of data that can be received by the receiving side
In the packet communication using P, the transmission rate of the packet from the transmission side is high, and the transmission rate of the response returned from the reception side is low, so that the window size does not become insufficient in time. The receiving side sends a confirmation response including information about the window size vacated on the receiving side to the transmitting side, and the transmitting side controls to update its own window size by the information about the window size. .

Therefore, while using TCP, it is possible to continue the transmission without a long time from the transmitting side, and as in the conventional case, a situation occurs in which the transmission is delayed until the arrival of the confirmation response. By eliminating the problem, packet transmission can be efficiently performed in asymmetric communication, time and communication resources can be effectively used, and long waiting time is eliminated, which leads to energy saving.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the present invention and is a block diagram showing a main part of a communication system according to a first example of the present invention.

FIG. 2 is a diagram for explaining the present invention and is a diagram showing a configuration of a network system according to a first example of the present invention.

FIG. 3 is a diagram for explaining the present invention, showing the behavior of TCP according to the first example of the present invention.

FIG. 4 is a diagram for explaining the present invention, showing a process flow of the workstation according to the first example of the present invention.

FIG. 5 is a diagram showing the behavior of conventional TCP.

FIG. 6 is a diagram showing the behavior of conventional TCP.

FIG. 7 is a diagram showing the behavior of conventional TCP.

FIG. 8 is a diagram for explaining the present invention, showing the behavior of TCP according to the second example of the present invention.

FIG. 9 is a diagram for explaining the present invention and is a diagram showing a protocol stack of a system according to a second example of the present invention.

FIG. 10 is a diagram for explaining the present invention and is a configuration diagram of a system and a terminal according to a second example of the present invention.

FIG. 11: TC of a gun or the like in asymmetric transmission by wireless communication
The figure which showed the behavior of P.

FIG. 12 is a diagram showing the behavior of conventional TCP.

FIG. 13 is a diagram for explaining the present invention and is a schematic diagram showing a communication system according to a second example of the present invention.

[Explanation of symbols]

1,2 ... workstation 3, 10 ... Transmitting / receiving means 5 ... Reception processing means 6 ... timer 7 ... Reception window size storage means 8 ... Transmission window size storage means 9 ... Transmission processing means 11 ... Reception processing means 21 ... Packet reception processing means 22 ... Judgment means 23 ... STT (Single Trip Time) calculation means 24 ... Threshold calculation means 601 ... Narrowband base station 602 ... Mobile terminal 603 ... Broadband base station 604, 605 ... Service area.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-228855 (JP, A) JP-A 64-29146 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04L 29/08 H04L 12/28

Claims (2)

(57) [Claims] 1. A system for communicating between a transmitting side using a communication line having a high communication speed for transmission and a receiving side using a communication line having a slower communication speed for transmission, wherein the transmitting side , At least the receiving side can receive
A packet communication system in which information of various capacities is stored, and when the transmitting side transmits packets, the information of the receivable capacity is subtracted based on the transmitted capacity and the transmission is continued for the receivable capacity of the receiving side. In the above, the receiving side defined according to the transmission speed of the transmitting side
When the number reaches a predetermined threshold that does not make the capacity for receiving data insufficient, the receiving side returns to the sending side an acknowledgment containing information on the receivable capacity freed by the receiving process at the receiving side, A communication system characterized in that information on the receivable capacity held on the transmitting side is controlled to update its own receivable capacity on the receiving side . 2. A communication system in which the transmission rate of a downlink radio channel for communicating from a base station to a mobile terminal is higher than the transmission rate of an uplink radio channel for communicating from a mobile terminal to a base station, and transmission on the downlink radio channel. Has at least the information of the receiving buffer capacity that can be received by the mobile terminal side , and when transmitting a packet , based on the transmitted capacity
The mobile terminal side can receive capacity of while subtracting the information of the receivable buffer capacity Te, in a packet communication system to continue the transmission, the mobile terminal receives the data using the radio channel, data In the transport layer that takes in, let λ be the product of the response data length of the mobile terminal and the response data length,
When the transmission rate of the upstream radio channel is μ, the frequency of returning the response is determined so that λ / μ is 1 or less, and the sum of the time interval for returning the response and the transmission time of the response is T when the receivable buffer capacity of the mobile terminal
The amount is set to a capacity larger than the product of the transmission rate of T and the downlink radio channel, and the transmission from the base station side to the mobile terminal side on the downlink radio channel is performed each time the response is received by the transmitter side. The amount of transmission on the downlink radio channel transmitted until the response is received is calculated by the portable terminal.
A communication system having a configuration of updating to an amount obtained by subtracting from the reception buffer amount .