JPH1041954A - Data transmitter-receiver and data communication system using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the transmission efficiency while the system is adapted flexibly to fluctuation in traffic by varying a window size of a logic link control section in response to a characteristic of a channel access control section in the case that a function of each communication station is made up of a channel access control section and the logic link control section in the communication system where a plurality of communication stations use in common one communication channel. SOLUTION: A channel access control section 4 of each communication station has two kinds of channel access control means or over and a logic link control section 5 of a transmitter side communication station has a function to select the channel access control means in the unit of transmission data. Furthermore, the logic link control section 5 of the transmitter side communication station has a function that uses the selected channel access control means to change maximum data number sent continuously without a reception reply from receiver side communication stations and adds the result to each of transmission data A-H or the like as window information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission / reception device and a data communication system using the data transmission / reception device, and more particularly to a communication configuration in which one communication line is shared by a plurality of communication stations. A line access control unit for controlling access to a communication line to communicate with each other;
The present invention relates to a data communication system suitable for use in a data communication system including a logical link control unit that performs transmission confirmation between communication stations and error recovery control.

[0002]

2. Description of the Related Art An example of a communication mode in which one communication line is shared by a plurality of communication stations is a LAN (Local Arrangement).
ea Network). In this LAN, a data link control function for performing data transmission confirmation and error recovery control between two stations communicating with each other is provided by a MAC (Media Access Control) for controlling access to a transmission path and an LLC (for performing logical link control). Logical Link Control).

[0003] As an AC access control method, C
SMA CD method (Carrier SenseMultiple Access)
And token passing methods. In the CSMA CD system, the MAC of each communication station monitors a carrier wave output on a transmission path, and outputs a carrier wave from its own station only when no other communication station outputs a carrier wave. In addition, when a plurality of communication stations start access at almost the same time, carrier waves may collide with each other on the transmission path. In such a case, the MAC detects the collision at the same time as the transmission, and
Try sending again.

[0004] On the other hand, the token passing system circulates control information for giving a transmission right called a token between communication stations, and a communication station that wants to transmit data acquires this token. This is a method that allows the use of a transmission path.

On the other hand, LLC requests its own MAC to transmit data to the transmission line,
C receives the data received from the transmission path.
The LAN LLC uses IEEE802.2 as a standard, establishes a logical link between two communication stations, and performs data delivery confirmation and error recovery control.

In LLC, a transmitting station can continuously transmit a plurality of data without waiting for a reception acknowledgment from the receiving station. However, the number of data that can be continuously transmitted is regulated by a parameter called a window size. This window size is determined when a logical link is established between two communication stations, and a fixed value is used until the logical link is disconnected.

In Japanese Patent Application Laid-Open No. Hei 2-241247, priorities are determined when a logical link is established, and when traffic on a line increases, transmission control is performed on a logical link basis according to the priority.

A second example of a communication mode in which one communication line is shared by a plurality of communication stations is satellite communication. An example of an access control method for sharing and using one satellite line by a plurality of ground stations is a time division multiple access method.

In this time division multiple access system, one satellite channel is time-divided into units called time slots to control the transmission right to each time slot. The control method includes a method of periodically allocating a time slot to each ground station (TDMA), a method of randomly transmitting a time slot to each ground station (slot Aloha), and a method of transmitting data to each ground station. There are a method of reserving a time slot and transmitting the assigned time slot, and a method of combining these three methods.

FIG. 5 shows a slot aloha system and a system using a reserved slot. This is an example of a line access method in a case where a plurality of ground stations share one satellite line and transmit data to the center station in a star network including one central station and a plurality of ground stations.

The data A is transmitted by the slot ALOHA, and when the data is generated, the peripheral station randomly accesses the time slot. On the other hand, data B, C, D,... Are transmitted using reserved slots. In this case as well, the first data B is transmitted by slot ALOHA. Make a reservation request. As a result, the subsequent data C, D, and E are transmitted on the reserved slot allocated by the central station.

[0012]

FIG. 10 shows an example in which the logical link control of the LLC of the LAN is performed in the star type satellite communication network for performing the line access control as shown in FIG.

Here, the satellite line is first time-divided into units called frames, and this frame is further time-divided into six time slots. It is assumed that allocation of a reserved slot from the central station is performed during a frame immediately before a frame including a slot to be allocated.

Further, it is assumed that a frame to which a reservation is assigned is two frames later than a frame to which a peripheral station transmits data with a reservation request added. Further, in this example, the window size of the logical link control is set to 3.

At this time, six data A, B,
It is assumed that C, D, E, and F are generated and transmitted using reserved slots. A, Β, C, D, E, and F are respectively assigned numbers from 0 to 5 as transmission order numbers NS. Since the window size is 3, only three of A, B, and C can be transmitted continuously from the logical link control unit of the peripheral station first. At this time, the reservation request 5 is added to the data A as the data up to the subsequent data F,
It is assumed that frame 1 has been transmitted by slot Aloha.

On the other hand, reservation allocation of five slots is performed for frame 3 two frames later.
By this time, the number of data for which the reception confirmation is notified by the reception response RR from the logical link control unit of the central station is 1, that is, only data A. Therefore, the window size is updated by one, and only the data D can be newly transmitted from the logical link control unit of the peripheral station. For this reason,
Of the five reserved slots allocated in frame 3,
Two slots cannot be used. Further, in order to transmit the subsequent data E and F, the reservation request is made again in a later frame or the transmission is performed by slot Aloha.

The transmission restriction based on the window size performed by the logical link control aims at suppressing an increase in traffic on the line and avoiding overflow of the reception buffer on the receiving station side.

In the CSMA / CD system in the LAN and the slot Aloha system in the satellite communication, data collision occurs.
It is important to control transmission by window size in link control. However, when using an access method that does not cause collision, such as a slot reservation method in satellite communication, it is more efficient to use a large window size.

A LAN IE@E802.2 LLC,
A similar procedure is the ISO standard ΗDLC (High
-1 evel Data Link Control) procedure and ITU-II Recommendation X. 25 LAPB (Link Access Procedure-Balanc)
ed) All procedures use a fixed window size from the time each link is established until it is disconnected.

In JP-A-2-241247, priority is set for each link and the degree of transmission restriction is changed for each link. However, transmission restriction cannot be changed for each data.

An object of the present invention is to provide a data transmission / reception apparatus and a data communication system capable of improving the performance of data communication, and in particular, improving the data transmission efficiency. By making the window size of the logical link control unit variable, transmission efficiency can be improved while flexibly adapting to traffic fluctuations.

[0022]

A data transmitting apparatus according to the present invention is a data transmitting apparatus for a communication station in a data communication system in which one communication line is shared by a plurality of communication stations. Means to send
It is characterized by including means for adding transmission order information indicating the transmission order to each transmission data, and means for adding window information indicating the maximum number of data to be continuously transmitted to these transmission data. .

A data receiving apparatus according to the present invention is a data receiving apparatus of a communication station that receives transmission data from the data transmitting apparatus, wherein the buffer means for temporarily storing the received data, and the transmission order information is detected. Means for extracting the received data stored in the buffer means in accordance with its transmission order, detecting the window information to determine a range of receivable transmission order information, and discarding received data outside this range; Means for notifying the data transmitting apparatus of the transmission order information of the received data last taken from the buffer means as a reception response.

A data communication system according to the present invention is a data communication system in which one communication line is shared by a plurality of communication stations, and a data transmission device of the communication station continuously transmits a number of transmission data. Means, means for adding transmission order information indicating the transmission order to each of these transmission data, and means for adding window information indicating the maximum number of data to be continuously transmitted to these transmission data, A buffer unit for receiving the transmission data from the data transmission device and temporarily storing the reception data, and detecting the transmission order information and transmitting the reception data stored in the buffer unit. Means for extracting the window information in accordance with the transmission order, determining the range of receivable transmission order information by detecting the window information, and discarding received data outside the range. When it is characterized by having a means for notifying a reception response finally the transmission order information of the received data fetched from the buffer means to the data transmission device.

Another data communication system according to the present invention comprises:
In a communication mode in which one communication line is shared and used by a plurality of communication stations, the function of each communication station is a line access control unit that controls access to the shared communication line, and two communication units that communicate with each other. A data communication system comprising: a logical link control unit that performs transmission confirmation of station inquiry and error recovery control, wherein the logical link control unit of the transmitting communication station does not wait for a reception response from the receiving communication station. Means for continuously transmitting two or more data, wherein the logical link control unit of the transmitting communication station includes means for adding transmission order information indicating a transmission order to each transmission data; Means for adding window information indicating the maximum number of data to be transmitted to each transmission data, wherein the logical link control unit of the receiving communication station comprises: a buffer for temporarily storing the reception data; Message added to Means for detecting order information and window information; means for fetching the received data stored in the buffer in the order of transmission; and determining the range of receivable transmission order information from the window information and transmitting order information outside the range. And means for discarding the received data to which the data is attached from the buffer and notifying the transmitting communication station of the transmission order information of the received data lastly taken from the buffer as a reception response.

The line access control section of the communication station has two or more types of line access control means, and the logical link control section of the transmitting communication station selects the line access control means for each transmission data unit. Means, and the logical link control unit of the transmitting side communication station changes the maximum number of data to be continuously transmitted by the selected line access control means and adds this to each transmission data as window information. It is characterized by having means.

The logical link control unit regulates transmission based on the window size, and makes the window size variable in data units by the selected line access control means. That is, a small window size is used when selecting a line access control unit suitable for low traffic, and a large window size is used when selecting a line access control unit suitable for a large amount of data transfer.
This makes it possible to improve transmission efficiency while flexibly responding to traffic fluctuations.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a configuration example of a satellite communication network employing the data communication system of the present invention. This satellite communication network has one central station C and a plurality of peripheral stations # 1
, Τ2,... These peripheral stations access the central station C by time-dividing one channel via the satellite S. The central station C has a host terminal,
A star-type network is realized by connecting a data terminal that exchanges data bidirectionally with the host terminal to the peripheral stations # 1 and T2.

FIG. 2 is a block diagram of the central station C. Central station C
Comprises a transmission / reception device 1, a modulation / demodulation device 2, and a baseband processing unit 3.

The transmission / reception device 1 performs transmission / reception to / from the satellite S and performs frequency conversion between a high frequency band and an intermediate frequency band.

The modulation / demodulation device 2 demodulates / error-corrects a signal received from the transmitting / receiving device 1 and encodes / modulates a signal transmitted to the transmitting / receiving device 1.

The baseband processing unit 3 comprises a line access control unit 4 and a logical link control unit 5. The configuration of the line access control unit 4 is as follows.

The frame timing signal generator 6 generates a frame timing signal for synchronizing with all peripheral stations. At the same time, the frame timing signal generator 6 also generates a reception frame timing used in the central station C.

The channel monitoring unit 7 determines the reception slot timing based on the reception frame timing received from the frame timing signal generation unit 6, and performs CRC (Cyclic
Redundancy Check) is used to detect transmission errors in packet data received on each time slot. Furthermore, if there is no transmission error in the received packet data, the channel monitoring unit 7 determines that the data transmitted on the time slot has been correctly received, and in other cases, whether data collision has occurred or It is determined that no data has been transmitted in that time slot.

Then, the channel monitoring unit 7 outputs the source peripheral station address of the correctly received data to the reception response generation unit 8. Further, the channel monitoring unit 7 delivers the received packet data to the logical link control unit 5. further,
When the reservation request from the peripheral station is added to the correctly received data, the channel monitoring unit 7 outputs the address of the source peripheral station of the data and the requested number of slots to the reservation management unit 9.

The reception response generator 8 generates a reception response signal using the source peripheral station address received from the channel monitor 7 and outputs it to the multiplexer 11.

The reserved slot management unit 9 includes a channel monitoring unit 7
A reservation information signal is created by using the source peripheral station address and the number of requested slots received from, and is output to the multiplexing unit 11.

The P / S section 10 converts the transmission data received from the logical link control section 5 from parallel to serial, adds a frame check sequence for detecting a transmission error, and outputs it to the multiplexing section 11.

The multiplexing unit 11 outputs a frame timing signal output from the frame timing signal generation unit 6, a reception response signal output from the reception response generation unit 8, a reservation information signal output from the reservation slot management unit 9, and P / The output from the S section 10 is time-division multiplexed and output to the modem 2.

The configuration of the logical link control unit 5 is as follows. The transmission buffer 12 receives data from the host terminal, buffers the data, and outputs it to the line access control unit 4. However, the output to the line access control unit 4 is under the control of the transmission control unit 13.

The transmission control unit 13 determines a window size WS that regulates the maximum number of data that can be continuously transmitted by the own station without acknowledgment of transmission, and transmits only the data allowed by the window size WS to the transmission buffer. 12 and output to the line access control unit 4. In addition, based on the reception response number from the peripheral station, which is notified from the reception control unit 17, the transmission confirmation of the data transmitted by the own station is performed, and the data whose transmission is confirmed is deleted from the transmission buffer 12, and Data that has not been acknowledged within a fixed time is retransmitted. Further, the transmission control unit 13 transmits the transmission order number {S
Is stored as the confirmation state variable V (A).

The transmission sequence number management unit 14 stores the transmission buffer 1
2, the transmission sequence number NS is assigned to the untransmitted data on the second transmission data, and the transmission sequence number
It is managed as (S).

The transmission window management unit 15 includes the transmission control unit 1
Based on the window size WS determined by No. 3, it is determined how many data of the transmission order number can be transmitted. That is, the transmission state variable V held by the transmission order number management unit 14
Referring to (S) and the confirmation state variable V (A) held by the transmission control unit 13, when the transmission order number NS of the untransmitted data in the transmission buffer 12 satisfies the following conditional expression (1). The transmission control unit 13 is notified that the untransmitted data can be transmitted.

V (S) ≦ NS <V (Α) + WS (1) The reception buffer 16 buffers the data received from the line access control unit 4, and if there is an order error in the received data, the order until the order is established. Buffer the data,
Outputs the ordered data to the host terminal. However, buffering of received data and output to the host terminal are performed by the reception control unit 17 and the reception sequence number management unit 18.
Control.

The reception control unit 17 temporarily buffers the reception data on the reception buffer 16, detects the transmission sequence number and the window information added to the reception data, and uses them to detect the reception sequence number management unit 18 and the reception window management unit. 19
Output to Further, the reception control unit 17 outputs the reception response number NR added to the reception data to the transmission control unit 13.

The reception sequence number management unit 18 has a function of reading data from the reception buffer 16 in the order according to the transmission sequence number and outputting the data to the host terminal. Receiving order number
Numeral 8 manages, as a reception state variable V (R), a value obtained by adding l to the transmission sequence number of the data finally output to the host terminal, that is, the transmission sequence number of the data to be next output to the host terminal.

The reception sequence number management unit 18 determines that the transmission sequence number of the data in the reception buffer 16 is
Only when it is equal to (R), the data is output to the host terminal, and 1 is added to the reception state variable V (R). Other reception data is held in the reception buffer 16 as it is.

The reason why the received data that does not arrive according to the transmission sequence number is not discarded is that the data transfer from the peripheral station to the central station involves retransmission control between the line access control units of both stations, so that the data is lost. Does not occur, and all data arrives at the central station within a fixed time.

The reception window management section 19 has a function of determining the effective range of the transmission sequence number added to the reception data. The reception window management unit 19 uses the window information WS of each reception data and the reception state variable V (R) held by the reception order number management unit 18 to set the transmission order number NS of the reception data on the reception buffer 16 to: Only when the following conditional expression (2) is satisfied, the data is transferred to the reception buffer 16.
V (R) ≦ NS <V (R) tens WS (2) Otherwise, illegal data that deviates from the transmission restriction control of the peripheral station logical link control unit on the transmission side Assuming that there is, the received data is discarded from the reception buffer 16.

Finally, the reception control unit 18 notifies the transmission control unit 13 of the value of the reception state variable V (R) held by the reception sequence number management unit 18.

The transmission control unit 13 determines that data having a transmission sequence number equal to [V (R) -1] has been received.
The value of [V (R) -1] is assigned to the untransmitted data in the transmission buffer 12 as the reception response number NR. If there is no untransmitted data in the transmission buffer, the transmission control unit 13 creates a monitoring packet for reception response and adds the reception response number NR to this.

However, it is assumed that the logical link control unit 5 exists separately for each peripheral station of the communication partner, and for the data input from the host terminal, selects the logical link control unit to be processed according to the address of the peripheral station of the destination. For the data input from the line access control unit 4, it is assumed that the logical link control unit is selected according to the address of the peripheral station of the transmission source.

FIG. 3 is a block diagram of the peripheral stations T1, T2,... The peripheral station includes a transmission / reception device 20, a modulation / demodulation device 21, and a baseband processing unit 22.

The transmitting / receiving device 20 transmits / receives signals to / from the satellite S and performs frequency conversion between a high frequency band and an intermediate frequency band.

The modulation / demodulation device 21 performs demodulation and error correction processing on the signal received by the transmission / reception device 20, and adds an error correction redundant bit to the signal output to the transmission / reception device 20 for encoding and demodulation.

The baseband processing unit 22 includes a line access control unit 23 and a logical link control unit 24. The configuration of the line access control unit 23 is as follows. The separation unit 25 receives the output of the modem 21, detects the frame timing signal generated by the central station C from the output, and
It outputs the frame timing to the frame / slot timing generation unit 26, the reception response signal to the delivery confirmation unit 33, the reservation information signal to the reservation slot management unit 34, and other data to the S / P unit 27.

Frame / slot timing generator 26
Determines the frame timing to be used when the own station performs transmission, taking into account the distance between the own station and the satellite, based on the frame timing signal transmitted from the central station C.
Further, this frame is time-divided into a predetermined number to determine the slot timing, and the slot timing is output to the buffer selecting unit 35.

The S / P unit 27 performs error detection on the data received from the separation unit 25, performs serial-parallel conversion on the normally received data, and outputs the data to the address comparison unit 28.

The address collating unit 28 looks at the destination peripheral station address of the received data, passes only the data addressed to the own station to the logical link control unit 24, and discards the other data.

The SW unit 29 receives the transmission data from the logical link control unit 24, and selects a transmission buffer for buffering the transmission data according to the access control means selected by the logical link control unit 24.

The transmission buffer has a function of temporarily buffering transmission data and outputting it to the transmission unit 36. In this example, since the slot Aloha system and the reserved slot system are used as the line access control means, the transmission buffer includes
Slot Aloha transmission buffer 30 and reservation transmission buffer 3
1. Assume that a retransmission buffer 32 for retransmission exists.

The slot ALOHA transmission buffer 30 buffers the data for which the logical link control unit 24 has selected the slot ALOHA as the line access means, and the reservation transmission buffer 31 uses the logical link control unit 24 as the line access means to reserve the data. Buffer the data for which the slot method has been selected.

At this time, the slot Aloha transmission buffer 30
The reservation transmission buffer 31 temporarily holds the data output to the transmission unit 36 in the retransmission buffer 32 for confirming delivery. The retransmission buffer 32 receives the retransmission / buffer release instruction signal from the delivery confirmation unit 33, erases the data instructed to be released from the buffer, and buffers the data instructed to be retransmitted in the internal dedicated buffer for retransmission data. Try again.

Receiving confirmation section 33 receives the output from buffer selecting section 35 and stores the time slot in which the own station tried to transmit, and the reception response signal outputted from separating section 25. Are compared with each other, and a response to the slot to which the own station has transmitted data is an ACK (ACKNOWLEDG)
MENT) or a negative acknowledgment NAK (NOT ACKNOWLEDGMENT).

That is, if the received response signal indicates the address of the own station, it is determined to be an acknowledgment ACK, and if all 0 or the address of another peripheral station is indicated, it is determined to be a negative response NAK. Then, the delivery confirmation unit 33 retransmits the data whose response is a negative response NAK and releases the data whose response is an acknowledgment ACK.
Instruct 2

The reservation slot management section 34 assigns each time slot to a slot Aloha slot, a reservation slot allocated to its own station, and a reservation for another peripheral station based on the reservation information signal output from the separation section 25. Classify into slots.

The buffer selection unit 35 receives the output from the frame slot timing generation unit 26, and refers to the slot type held by the reserved slot management unit 34 for each slot timing to select a transmission buffer from which data is read. In other words, if it is a slot for slot Aloha,
Retransmission buffer 32 or slot Aloha transmission buffer 3
From 0, if it is a reserved slot assigned to its own station,
The data is read from the reservation transmission buffer 31, and the transmission unit 36
Output to

If the time slot is a reserved slot for another peripheral station, data is not read. Further, the buffer selecting unit 35 notifies the delivery confirming unit 33 whether data transmission has been performed in each time slot.

The transmitting section 36 outputs data read from each transmission buffer to the modem 21. At this time, the transmitting unit 36 adds a frame check sequence for detecting the address of the own station and a transmission error to the data transferred to the modem 21.

The configuration of the logical link control unit 24 is as follows. The packetizer 37 converts the data input from the terminal into a packet that can be transmitted on a time slot. That is, when the length of the data input from the terminal is longer than one time slot, the data is divided into a plurality of packets and buffered in the transmission buffer 38.

Transmission buffer 38, transmission control unit 39, transmission sequence number management unit 40, transmission window management unit 41, reception buffer 42, reception control unit 43, reception sequence number management unit 4
4. The reception window management unit 45 includes the transmission buffer 12 and the transmission control unit 1 in the configuration of the central station C in FIG.
3, transmission sequence number management unit 14, transmission window management unit 1
5, have the same functions as the reception buffer 16, reception control unit 17, reception sequence number management unit 18, and reception window management unit 19.

However, the following two points are different from the central station C side. The difference 1 is that the transmission control unit 39 does not retransmit data. This is because the line access control unit 23 performs retransmission control on data transfer from the peripheral station to the central station.

The second difference is that the reception window management unit 45
When the transmission sequence number ΝS of the reception data buffered on the reception buffer 42 is not equal to the reception state variable V (R) held by the reception sequence number management unit 44, the data is deleted from the reception buffer. .

FIG. 4 (A) shows a case where the central station moves from the peripheral stations T1, T
The format of the signal going to 2, ... is shown.

The central station C transmits user data to the peripheral stations T 1, T 2,..., And transmits a frame timing signal indicating a frame break of a fixed time length in the broadcast mode. The frame timing signal serves as a reference for timing used when the peripheral stations T1, T2,... Transmit from their own stations. The interval at which the frame timing signal is transmitted is determined by the time of the channel when transmitting from the peripheral station. Equal to the length of the frame to be split.

The central station C transmits a reception response signal for the data transmitted by the peripheral station and a reservation information signal for notifying the reservation slot allocation requested by the peripheral station in the broadcast mode, following the frame timing signal. Send.

In the signal from the central station C to the peripheral station, the packet data is sandwiched between flags (F) indicating the start and end of the packet. In the packet data, an information frame containing user data transmitted from the host terminal connected to the central station C to the user data terminal connected to the peripheral station, and the logical link control unit 5 of the central station C And a monitor frame transmitted for link control.

The information frame has a destination peripheral station address (AD
RS), transmission sequence number (NS) and reception response number (N
R) window information (WS), data (DATA) generated from the host terminal of the central station, and a frame check sequence (FCS) for detecting a transmission error.

The monitoring frame has a configuration in which data (DATA) is excluded from the configuration of the information frame. However, the monitoring frame has a monitoring function display S indicating that it is a monitoring frame instead of the transmission order number NS.

In the packet data format, the ADRS section, NS section, NR section, and WS section correspond to the central station C.
The logical link control unit 5 of FIG.
This is added by the unit 10.

Further, the monitoring frame transmitted by the central station link control unit 5 is only a reception response frame called an RR frame.

FIG. 4B shows a format of a signal transmitted from the peripheral station to the central station C. In transmitting a signal from the peripheral station to the central station C, one channel is first divided into frames of a fixed time length, and this frame is further divided into several time slots, and this time slot is divided into one transmission unit. And In the example of FIG. 4B, one frame is divided into six time slots.

The packet data transmitted from the peripheral station to the central station C includes a user data terminal connected to the peripheral station.
There are an information frame containing user data transmitted to a host terminal connected to the central station, and a monitoring frame transmitted by the logical link control unit 24 for link control.

The information frame includes a header section (O) including a preamble section for carrier / clock recovery.
Η), a field (AD) indicating the peripheral station address of the transmission source
RS), a field (P
L), a field (R) indicating the number of slots for which reservation is requested
EQ), transmission sequence number (NS), reception response number (NR)
Window information (WS), a field for accommodating user data (DATA), a dummy bit (DUM) for adjusting the length of a packet to the length of a time slot, a frame check sequence field (FCS) for detecting a transmission error, Redundant bits for error correction (FE
C), and a guard time (CΤ) for securing an interval with a packet transmitted in the previous slot.

On the other hand, the configuration of the monitoring frame is obtained by removing the DATA part from the configuration of the information frame. However, the monitoring frame has a monitoring function display S instead of the transmission order number NS.

In the packet data format, the ADRS part, PL part, REQ part, NS part, NR part,
The WS unit is added by the logical link control unit 24 of the peripheral station,
The UΜ section / FCS section is added by the transmission section 36, and the OΗ section / FE
The C / GT is added by the modem 21.

The monitoring frame transmitted by the peripheral station logical link control unit 24 notifies a reception response frame called an RR frame and a request for the detection and retransmission of the order error to the central station logical link control unit 5. REJ frame.

FIG. 5 shows a slot ALOHA system and a reserved slot system, which are two access control means used by the line access control unit in data transmission from the peripheral station to the central station. Here, the satellite link is first time-divided into frames, and this frame is further time-divided into six time slots.

The allocation of reserved slots from the central station is as follows:
It is assumed to be performed during the frame immediately before the frame including the slot to be allocated. In addition, it is assumed that a frame to which a reservation is assigned is two frames later than a frame to which a peripheral station transmits data with a reservation request added. It is also assumed that a reception response signal from the central station line access control unit for data transmitted from the peripheral station line access control unit is notified two frames after the transmitted frame.

The data A is transmitted by the slot ALOHA, and when the data is generated, the peripheral station randomly accesses the time slot. On the other hand, data B, C, D, and E are transmitted using reserved slots, and also in this case, the first data Β is transmitted by slot ALOHA.
A reservation request for the subsequent three data is made. As a result, the subsequent data C, D, and E are transmitted on the reserved slots allocated by the central station.

FIG. 6 shows the format of a reception response signal and reservation information signal broadcast from the central station.
The reception response signal is obtained by arranging, in the order of the used slots, the source peripheral station addresses of the data correctly received by the central station C, the slot in which no data is received,
Alternatively, all 0s are written for slots in which data could not be received normally due to data collisions or transmission errors.

On the other hand, the reservation information signal is obtained by arranging addresses of peripheral stations to which slots are allocated in the order of slots.
All 1s are written for slots that are not assigned to any peripheral station, that is, slots for slot Aloha. However, it is assumed that there is no peripheral station having an address corresponding to all 0 or all 1. The reception response signal and the reservation information signal are transmitted in units of 1 frame.

FIG. 7A shows the details of the instruction link control unit 5 of the central station C. The three data P0, P1, P2 existing in the transmission buffer 12 have already been
Output to the server and waiting for delivery confirmation. Also,
Since there is one line access control means for data transfer from the central station to the peripheral station, the window size WS is 3
Fixed. Confirmation state variable V held by transmission control unit 13
(A) is 0, and the transmission state variable V (S) held by the transmission order number management unit 14 is 3, so that V (S) = V (A) -WS (3).

According to the equation (3), the logical link control unit of the central station C cannot transmit data until there is a response from the peripheral station due to the restriction by the window size.

On the other hand, on the reception buffer 16, two data P0 ', P1 of transmission sequence numbers NS = 0 and NS = 2 are stored.
'Is buffered. Of these, data P0
Is output to the host terminal, and the reception state variable V (R) of the reception order number management unit 18 is updated to 1. Next data P
Since 1 'has arrived before NS = 1 data,
It is not output to the host terminal as an incorrect order. However, since the window information WS of the data P1 'is 3, which satisfies the condition of the above equation (2), this data is held in the reception buffer 16 as it is.

Here, data of transmission sequence number NS = 1
When 2 'arrives, the reception sequence number management unit 18 reads out the data P2' and then the data P1 'from the reception buffer and outputs them to the host terminal. As a result, the reception state variable V (R) held by the reception order number management unit 18 is updated to 3.

FIG. 7B shows the details of the logical link control unit 24 of the peripheral station #. The three data P0, P1, P2 existing in the transmission buffer 38 are already stored in the line access control unit 2
3 and is waiting for delivery confirmation. Also, as line access control means for these three data,
Assuming that the slot Aloha method has been selected, the window size WS is set to a predetermined minimum value (3 in this example).

Confirmation state variable V held by transmission control unit 39
(A) is 0, and the transmission state variable V (S) held by the transmission sequence number management unit 40 is 3, so that the logical link control unit of the peripheral station T Until there is a reception response from the station, data cannot be transmitted due to the restriction by the window size.

On one receiving buffer 42, there are three data P0 ', P1',
Ρ2 'is buffered. Since the three data have arrived according to the sequence numbers, the reception sequence number management unit 18 immediately reads out the three data from the reception buffer and outputs the data to the terminal. As a result, the reception state variable V (R) of the reception sequence number management unit 18 is updated to 3.

FIG. 8A is a second detailed explanation of the logical link control unit 5 of the central station C. It is assumed that the data P3 in the transmission buffer 12 has already been output to the line access control unit 4, and that transmission confirmation has been performed. Since the transmission state variable V (A) held by the transmission control unit 13 is 3 and the transmission state variable V (S) held by the transmission sequence number management unit 14 is 4, [V (A) + WS] −V ( S) = 2 (4) According to the equation (4), the logical link control unit of the central station C can transmit the remaining two data without waiting for the reception response from the peripheral stations.

On the other hand, on the reception buffer 16, there are four data P3, # 4 of transmission sequence number NS = 3, 4, 5, 6
, # 5, and P6 are buffered. Although the reception state variable V (R) of the reception order number management unit 18 is 3,
Since the window information WS added to the data P3 ', P4', P5 ', P6' is all four, the above (2)
It satisfies the condition of the formula and arrives at the order number. For this reason, the reception order number management unit 18 reads out the four data P3 ', P4', P5 ', P6' from the reception buffer and outputs them to the host terminal. As a result, the reception state variable V (R) held by the reception order number management unit 18 is updated to 7.

FIG. 8B is a second detailed explanatory diagram of the logical link control unit 24 of the peripheral station T. It is assumed that the four data P3, P4, P5, P6 existing in the transmission buffer 38 have already been output to the line access control unit 23 and are waiting for a delivery confirmation. It is also assumed that the slot reservation method is selected as the line access control means for these four data.

For this reason, the window size WS is extended to 4. Since the confirmation state variable V (A) held by the transmission control unit 39 is 3 and the transmission state variable V (S) held by the transmission sequence number management unit 40 is 7, under the same conditions as the above equation (3), The logical link control unit of the peripheral station T has just finished transmitting data of the full window size.

FIG. 9 shows an example of data transfer from the peripheral station T to the central station C in the system of the present invention. Data A and B generated in the peripheral station are transmitted by the slot ALOHA method. Here, six data C, D, E, F, G. It is assumed that H occurs in a peripheral station and is transmitted using a reserved slot. If the window size remains 3, the data C1 can be transmitted from the logical link control unit 24 of the peripheral station Τ without receiving a response from the logical link control unit 5 of the central station C.
One. However, in this method, the extended window size is determined by the following equation (5).

WS = number of transmitted windows (= 2) × number of data waiting to be transmitted (= 6) (5) As a result, the window size WS becomes 8, and the confirmation state variable V (A) of the peripheral station logical link control unit 24 ) = 0 and the transmission state variable V (S) = 2, the expressions (6) and (7) are given as follows: V (A) + WS = 8 (6) [V (A) + WS] − V (S) = 6 (7) The peripheral station logical link control unit 24 can transmit all six data CΗ.

At this time, the logical link control unit 24 sets WS = 8
Is added to the data C to Η, and the number of reservation requests is set to 5 in C of the first data.

When the reservation slot 5 is allocated from the central station C, the data D to Η are transmitted to the line access control unit 2 of the peripheral station.
3 so that they can all be transmitted on the reserved slot.

[0109]

According to the present invention, when a line access control means that can cause a collision is used, as in the slot Aloha method, the window size is reduced.
In order to realize system stabilization and to use line access control means suitable for large-volume data transfer without collision, as in the case of the reserved slot method, the transmission efficiency is increased by expanding the window size. There is an effect that it can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a satellite communication network according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a central station C.

FIG. 3 is a block diagram showing a configuration of a peripheral station.

4A is a diagram showing a signal format from a central station C to a peripheral station, and FIG. 4B is a diagram showing a signal format from a peripheral station to a central station C.

FIG. 5 is a diagram illustrating an example of line access control in data transmission from a peripheral station to a central station C;

FIG. 6 is a format diagram of a reception response signal and a reservation information signal broadcast from the line access control unit of the central station C;

FIG. 7A is a detailed diagram of the operation of the logical link control unit 5 of the central station C, and FIG. 7B is a diagram showing details of the operation of the logical link control unit 24 of the peripheral station;

8A is a diagram illustrating a second example of the details of the operation of the logical link control unit 5 of the central station C, and FIG. 8B is a diagram illustrating a second example of the details of the operation of the logical link control unit 24 of the peripheral station; It is a figure showing an example.

FIG. 9 is a diagram illustrating an example of data transmission from a peripheral station to a central station C according to the present invention.

FIG. 10 is a diagram showing an example of logical link control in the related art.

[Explanation of symbols]

 S satellite C Central station T1 to T3 Peripheral station 1,20 Transmitter / receiver 2,21 Modulator / demodulator 3,22 Baseband processor 4,23 Line access controller 5,24 Logical link controller 6 Frame timing signal generator 7 Channel monitoring Unit 8 reception response generation unit 9 reserved slot management unit 10 P / S unit 11 multiplexing unit 12, 38 transmission buffer 13, 39 transmission control unit 14, 40 transmission sequence number management unit 15, 41 transmission window management unit 16, 42 reception buffer 17, 43 Reception control unit 18, 44 Reception sequence number management unit 19, 45 Reception window management unit 25 Separation unit 26 Frame / slot timing generation unit 27 S / P unit 28 Address collation unit 29 SW 30 Slot Aloha transmission buffer 31 Reserved transmission Buffer 32 Retransmission buffer 33 Delivery confirmation unit 34 Reserved slot Management unit 35 buffer selector 36 transmitting unit

Claims (5)

[Claims] 1. A data transmission apparatus for a communication station in a data communication system in which one communication line is shared by a plurality of communication stations, comprising: means for continuously transmitting a plurality of transmission data; A data transmission apparatus, comprising: means for adding transmission order information indicating a transmission order to the transmission data; and means for adding window information indicating the maximum number of data to be continuously transmitted to the transmission data. 2. A data receiving device of a communication station for receiving transmission data from the data transmitting device according to claim 1,
Buffer means for temporarily storing received data; means for detecting the transmission order information and extracting the received data stored in the buffer means in accordance with the transmission order; and detecting the window information to enable reception of transmission order information. Determining a range, means for discarding received data out of the range, and means for notifying the data transmitting device of the transmission order information of the last received data from the buffer means as a reception response, Data receiving device. 3. A data communication system in which one communication line is shared by a plurality of communication stations, wherein a data transmission device of the communication station continuously transmits a plurality of transmission data; Means for adding transmission order information indicating the transmission order to the transmission data, and means for adding window information indicating the maximum number of data to be continuously transmitted to these transmission data; A buffer means for receiving transmission data from the data transmission apparatus and temporarily storing the reception data; and a means for detecting the transmission order information and extracting the reception data stored in the buffer means in accordance with the transmission order. Means for detecting the window information to determine the range of receivable transmission order information, discarding received data outside this range, Means for notifying the data transmitting apparatus of the transmission order information of the received data fetched as a reception response. 4. In a communication mode in which one communication line is shared and used by a plurality of communication stations, a function of each communication station includes a line access control unit for controlling access to a shared communication line and a line access control unit. A logical link control unit that performs transmission confirmation and error recovery control of two communication stations that perform communication, wherein the logical link control unit of the transmission side communication station performs reception from the reception side communication station. Means for continuously transmitting two or more data without waiting for a response, wherein the logical link control unit of the transmitting communication station includes means for adding transmission order information indicating a transmission order to each transmission data; Means for adding window information indicating the maximum number of data to be continuously transmitted to each transmission data, wherein the logical link control unit of the receiving communication station temporarily stores the reception data. Buffer and received data Means for detecting the added transmission order information and the window information,
Means for fetching the received data stored in the buffer in the transmission order, and determining a range of receivable transmission order information from the window information, and discarding the received data added with transmission order information outside the range from the buffer. And a means for notifying a transmitting communication station of transmission order information of the last received data from the buffer as a reception response. 5. The line access control unit of the communication station has two or more types of line access control units, and the logical link control unit of the transmission side communication station selects the line access control unit for each transmission data unit. Means, and the logical link control unit of the transmitting side communication station changes the maximum number of data to be continuously transmitted by the selected line access control means and adds this to each transmission data as window information. 5. The data communication system according to claim 4, further comprising means.