JP2702031B2 - Satellite communication controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite communication control device, and more particularly to a satellite communication control device used for communication between local area networks using a satellite communication line.

[0002]

2. Description of the Related Art Data communication between computers using a satellite communication line using a communication satellite, a broadcasting satellite, or the like as a relay has been conventionally performed. Excellent expandability.

Data communication using a satellite communication line between computers is often performed as a transmission control procedure using a high-level data link (HDLC) having high transmission efficiency and high reliability.
Is adopted.

[0004]

When a computer that transmits and receives data is one node of a local area network constructed in each local area,
In other words, when data communication is performed between local area networks, a transmission frame for data transmission between computers exists in the local area network, in addition to a transmission frame in satellite communication.

[0005] In such a case, if the access method of each local area network for transmitting and receiving data is the same, satellite communication between the local area networks for each transmission frame of the local area network can be performed by each local area network. This is effective in reducing the communication processing load in the communication.

In a communication satellite, each receiving station receives all transmission data from the transmitting station, including unnecessary data. Therefore, if all the received data is indiscriminately taken into the local area network, Therefore, the traffic volume of the local area network increases, and various problems occur.

The present invention has been made in view of the above-mentioned points and problems in communication between local area networks by satellite communication, and has been made without the necessity of a large-scale device. Local area network / satellite communication transmission / reception that can perform satellite communication for each local area network transmission frame without being aware of satellite communication transmission control, and can transfer only necessary received data to the local area network An object is to provide a satellite communication control device as an inter-station adapter.

[0008]

According to the present invention, there is provided a local area network controller, a high-level data link controller, a memory, and a direct memory access controller,
The direct memory access controller transfers data obtained by removing a preamble and a frame check sequence from a transmission frame of the local area network to the memory from the local area network controller, and transfers the data from the memory to the high-level data link controller. And transferring only the data of the information field of the frame of the high-level data link from the high-level data link controller to the memory, and transferring the data from the memory to the local area network controller. The high-level data link controller writes all of the data transferred from the memory into an information field, and writes a flag and A high-level data link frame by adding a nation address and a frame check sequence, outputting the frame to the satellite communication transmitting station, and inputting the high-level data link frame from the satellite communication receiving station. The local area network controller generates a local area network transmission frame by adding a preamble and a frame check sequence to the data transferred from the memory, and outputs the frame to the local area network; This is achieved by a satellite communication control device, which is configured to input a transmission frame of a local area network from an area network.

In order to achieve the above-mentioned object, in the satellite communication control apparatus according to the present invention, the high-level data link controller includes information in a destination address field held in a high-level data link frame. It may have a function of writing a service identification code indicating the type of service.

In order to achieve the above-mentioned object, in the satellite communication control device according to the present invention, the high-level data link controller writes the data in a destination address field held in a frame of the high-level data link. It may be configured to identify the service identification code given, and to fetch and process only a frame to which a specific service identification code is assigned.

[0011]

According to the above-mentioned configuration, when data is transmitted between the local area network and the satellite communication transmitting station or the satellite communication receiving station, the protocol conversion is automatically performed between the local area network and the satellite communication transmitting station or the satellite communication receiving station. Satellite communication by high-level data link is performed for each transmission frame of the local area network,
The transmission frame of the local area network is exchanged with each local area network.

The data transmitting side writes a service identification code indicating the type of the information service in the destination address field of the frame of the high-level data link, and the data receiving side writes the service identification code in the destination address field. A service identification code is identified, and only a frame to which a specific service identification code is assigned is fetched and processed.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 1 shows an example of the overall configuration of a communication system using a satellite communication control device according to the present invention. There are at least two local area networks as indicated by reference numerals 1 and 3. A workstation 7 is connected to each of the local area networks 1 and 3 via a LAN transmission line 5. The access method of the local area networks 1 and 3 is, for example, CSMA / CD
In this case, the transmission frames (LAN frames) of the local area networks 1 and 3 are Ethernet frames as shown in FIGS. 3 (a) and 3 (c). Ethernet frames are
An 8-byte preamble as an Ethernet synchronization flag, a 6-byte destination address indicating a partner station, a 6-byte source address indicating a local station,
It has a byte type field, a data field of 46 to 1500 bytes, and a frame check sequence in order.

A satellite communication control device 9 as an adapter between a local area network and a satellite communication transmitting / receiving station is connected to each LAN transmission line 5, and a satellite communication transmitting station 11 or a satellite communication receiving station 13 is connected to the satellite communication control device 9. RS44
9 and the like. In this case, the satellite communication transmitting station 11 is connected to the satellite communication control device 9 of the local area network 1 and the local area network 1 becomes a host, and the satellite communication receiving station 13 is connected to the satellite communication control device 9 of the local area network 3. Is connected to the local area network 3
Becomes local.

The satellite communication control device 9 has a control terminal 1 for setting various parameters and monitoring status.
5 are connected by an input / output interface 14 such as RS232C.

The satellite communication transmitting station 11 has an encoder 17, a modulator 19, a frequency converter 21, an amplifier 23, and an antenna unit 25.
The transmission data is given by the antenna unit 25, and a radio wave is transmitted from the antenna unit 25 to the communication satellite 27.

The satellite communication receiving station 13 has a decoder 29, a demodulator 31, an amplifier 33, and an antenna unit 35,
The antenna unit 35 receives radio waves from the communication satellite 27,
The received data is output from the decoder 29 to the satellite communication control device 9.

The work station 7 of the local area network 1 and the work station 7 of the local area network 3 are communicably connected by a terrestrial communication network 28 such as an ISDN, a DDX, and a dedicated line. Is sent to the terrestrial communication network 28
Is to be performed.

FIG. 2 shows a specific configuration example of the satellite communication control device 9. The satellite communication control device 9 includes an Ethernet transceiver 37 for connecting to the LAN transmission line 5 by Ethernet, an Ethernet serial communication controller 39, a local area network controller (hereinafter, LAN controller) 41, and a CPU 43 having a built-in DAM controller. A high-level data link controller (hereinafter, HDLC controller) 45;
An SRAM 47 as a memory, a ROM 49 in which respective programs for transmission control and reception control are written,
An external direct memory access controller (hereinafter, DMA controller) 51, a transceiver 53 for connecting the satellite communication transmitting station 11 or the satellite communication receiving station 13 by the input / output interface 10, and a control terminal by the input / output interface 14. 15 and a transceiver 55 for connection with the communication device 15.

Ethernet serial communication controller 3
Reference numeral 9 indicates that the satellite communication control device 9 monitors the collision of carriers in Ethernet so that the satellite communication control device 9 functions as one node in the local area network, encodes the received data into Manchester code, and transfers it to the Ethernet transceiver 37. It has become.

The LAN controller 41 fetches an Ethernet frame from the Ethernet serial communication controller 39 in the transmission mode, and adds a preamble and a frame check sequence to the data transferred from the SRAM 47 in the reception mode. Such an Ethernet frame is generated, and the Ethernet frame is output to the Ethernet serial communication controller 39.

The CPU 43 operates by being supplied with an operation clock from an oscillator 59, and has a DMA built in the CPU 43.
The controller includes a LAN controller 41 and an SRAM 4
7 is controlled by the LAN controller 41 in the transmission mode.
Data obtained by removing the preamble and the frame check sequence from the Ethernet frame is transferred to M47, and equivalent data is transferred from the SRAM 47 to the LAN controller 41 in the reception mode.

The external DMA controller 51 is
The data transfer between the HDLC controller 45 and the SRAM 47 is controlled. In the transmission mode, data is transferred from the SRAM 47 to the HDLC controller 4.
5, in the reception mode, only the data of the information field of the frame of the high-level data link is transferred from the HDLC controller 45 to the SRAM 47.

The HDLC controller 45 includes an oscillator 59
The operation clock is generated via a 1/2 frequency divider 61 and operates. In the transmission mode, all of the data transferred from the SRAM 47 is written in the information field in its entirety, and a flag and a destination are written to the information field. A high-level data link frame (hereinafter, HDLC frame) as shown in FIG. 3B is generated by adding the address and the frame check sequence, and this HDLC frame is transmitted from the transceiver 53 to the satellite communication transmitting station 11. It is configured to output the HDLC frame from the satellite communication receiving station 13 from the receiver 53 in the receiving mode.

In the satellite communication, it takes a long time to transmit, and since this satellite communication is one-way 1: N communication, a retransmission request is not made. In the link, the number management is unnecessary, so that the control field in the HDLC frame may be omitted.

A parallel port 65 is connected to the CPU 43. A dip switch 67, an LED driver 69 and an LED driver 71 for displaying numbers are connected to the parallel port 65, and the LED driver 69 displays a normal operation. The LED 73 for displaying the transmission error occurrence is connected to the LED driver 71 for displaying the number, and the numeral display L is provided to the LED driver 71 for displaying the number.
The ED 75 is connected.

The dip switch 67 sets the satellite communication control device 9 for either transmission or reception.
The parallel port 65 is used for setting the transfer rate and parity of the input / output interface 14 for connecting the control terminal 15 and setting the service identification code.
The CPU 43 is directly accessed via the. The setting of the service identification code by the dip switch 67 can be performed for a plurality of units.

The service identification code read by the CPU 43 is set in the destination address register of the HDLC controller 45, and is set to H in the transmission mode.
The data is written to the destination address of the HDLC frame by the DLC controller 45. The service identification code read by the CPU 43 is transferred to the numeral display LED driver 71, and the value is displayed on the numeral display LED 75.

Also, as described above, the HDLC controller 45
In the reception mode, the HDLC controller 45 identifies the service identification code written in the destination address of the HDLC frame by setting the service identification code in place of the destination address in the destination address register. Then, only the HDLC frame in which the same service identification code as the set service identification code is written in the destination address is processed.

As described above, the service identification code is inserted in the destination address of the HDLC frame in place of the destination address, and the destination address of the HDLC frame is not used as the address information field because it is included in the information field of the HDLC frame. This is because the Ethernet frame has a destination address, which is used as address information.

The setting of the service identification code, the setting of the transmission / reception mode of the satellite communication control device 9, the setting of the transfer rate of the input / output interface 14 for connecting the control terminal 15, the setting of the parity, etc. , The control terminal 15, and the workstations 7 connected to the local networks 1, 3.

The service identification code includes electronic catalog information, new product information, product sales information, housing information, stock information,
It may indicate the type of information service such as ticket reservation information, travel guidance information, news, and electronic conference.

The service identification code includes a management information code, which is used for information transmitted from the transmitting station to all the receiving stations simultaneously for system management. The management information for management includes data transmission suspension due to trouble occurrence, data transmission restart due to recovery, and the like. In the management information, there is a command that all the receiving stations can send a response signal to the transmission by the terrestrial communication network 28 so that the transmitting station checks the number of the receiving stations. The transmitting station can detect the transmission error rate by checking the number of receiving stations, and this check may be performed periodically.

In the case of data transmission, the workstation 7
LAN transmission path 5, Ethernet transceiver 37,
LA via Ethernet serial communication controller 39
The destination address, the source address, the type field, and the data field of the Ethernet frame input to the
SRAM 4 by the built-in DMA controller
7 sequentially.

Next, the CPU 43 writes the currently set service identification code into the destination address register of the HDLC controller 45, and the data held in the SRAM 47 by the DMA controller 51, ie, the destination address and the source address of the Ethernet frame. The type field and the data field are sequentially transferred to the HDLC controller 45.

The HDLC controller 45 has the SRAM 4
7, a HDLC flag is added to the beginning of the data, a destination address in which the service identification code written in the destination address register is written, and a CR is added to the end of the data.
An HDLC frame is generated by adding a frame check sequence such as C and an HDLC flag.

This HDLC frame is sent as transmission data to the transceiver 53, and the transceiver 53
The signal is converted from the TL level to the electrical level of the input / output interface 10 and transferred to the satellite communication transmitting station 11.

The transmission of the transmission data to the satellite communication transmitting station 11 is performed in synchronization with the transfer clock from the satellite communication transmitting station 11. As a result, the satellite communication control device 9 operates without depending on the data communication speed of the satellite communication line.

When there is no transmission data, the HDLC controller 45 outputs "1".

In the case of data reception, the HDLC controller 45 takes in the received data from the satellite communication receiving station 13 via the transceiver 53 in synchronization with the transfer clock from the satellite communication receiving station 13. The received data is based on the HDLC frame, and the HDLC controller 45 firstly writes the service identification code described in the destination address of the received HDLC frame into the service identification code written in the destination address register of the HDLC controller 45. Is determined, and if they do not match, the data acquisition is stopped and the data is discarded. If the service identification codes match, only the data in the information field of the HDLC frame is transferred from the HDLC controller 45 to the SRAM 47 by the DMA controller 51.

At this time, a transmission error is detected by the frame check sequence of the HDLC frame. If a transmission error is detected, the data in the information field is discarded, and the data is not transferred to the SRAM 47. When a transmission error occurs, the receiving station does not make a retransmission request, the upper communication protocol of the work station 7 detects a missing frame, and makes a request using the terrestrial communication network 28.

When a transmission error occurs, the time and frequency of occurrence of the transmission error are recorded in the SRAM 47, which can be monitored and counted by the control terminal 15 or the workstation 7.

When the data of the information field of the HDLC frame is transferred from the HDLC controller 45 to the SRAM 47, the data of the information field is transferred from the SRAM 47 to the LAN controller 41 by the DMA controller built in the CPU 43.

The LAN controller 41 has an SRAM 47
Then, a preamble is added to the head of the data, and a frame check sequence such as CRC is added to the end of the data to generate an Ethernet frame, and this is transferred to the serial communication controller 39. The serial communication controller 39 encodes the received data into a Manchester code and transfers this to the transceiver 37.
The transceiver 53 converts it from the TTL level to the Ethernet electrical level and sends it out to the LAN transmission line 5.

By the flow control as described above, the difference between the data transfer rate in the Ethernet and the data transfer rate in the serial input / output interface 10 such as RS449 is absorbed.

Error control is required for a data transmission error on a data transmission path by Ethernet.
In the above-described system, a serial number is assigned to the Ethernet frame so that a predetermined number of frames can be continuously transmitted unless a transmission error notification is issued from the receiving side. The maximum number of frames that can be transmitted continuously is called the maximum number of outstanding frames. When the transmitting side has transmitted the maximum number of outstanding frames without error, transmission of the next frame is stopped until the receiving side receives an acknowledgment (ACK) signal from the receiving side that the data has been received without error. After confirming the reception of the acknowledgment signal, the next frame transmission may be resumed.

The data transfer rate in Ethernet is R
Serial input / output interface 10 such as S449
Since the data transfer rate is higher than the data transfer rate in the above, the above-described error control is required when transmitting a transmission frame from the workstation 7 to the satellite communication control device 9. In this case, in order to speed up data transmission, it is preferable to increase the maximum number of outstanding frames and relatively increase the capacity of the communication buffer in the satellite communication control device 9. When transmitting a transmission frame from the satellite communication control device 9 to the workstation 7, the maximum number of outstanding frames does not need to be set to a very large value.

In satellite communication as described above, HDLC
Since frames are used, satellite communication is a mere transmission path, and data is dripped as it is.Even if it is difficult to distinguish between when transmission data exists and when it does not exist, the existence of transmission data is determined by the receiving side. Easily detected by
It is unnecessary to generate useless operation and traffic on the receiving side. In addition, the use of the HDLC frame makes it possible to detect a transmission error using an error detection code at the final stage on the receiving side.

The satellite communication line to which the satellite communication control device according to the present invention as described above is applied is not limited to the digital satellite communication using a communication satellite, but the satellite communication line to which the satellite communication control device is applied. The line may use an independent data part of a format of a QPSK-FM system by a broadcasting satellite.

[0051]

As can be understood from the above description, according to the satellite communication control apparatus of the present invention, in data communication between local area networks by satellite communication, the local area network and the satellite communication transmitting station or the satellite communication receiving station. Protocol conversion that is compatible with each other, that is, conversion between a transmission frame of a local area network such as Ethernet and a frame of a high-level data link is automatically performed, and satellite transmission by the high-level data link is performed for each transmission frame of the local area network. Therefore, each local area network exchanges transmission frames of the local area network, so that large-scale devices are not required, and satellite communication between local area networks can be efficiently performed without being aware of satellite communication transmission control. Yo Become to be done.

The data transmitting side writes the service identification code indicating the type of the information service in the destination address field of the frame of the high-level data link, whereby the service different from one transmitting workstation is written. Can be transmitted at the same time, and if there are multiple transmitting stations, the data with a unique service identification code from each transmitting station can be used by time-sharing the satellite channel. Will be able to send. Also, the data receiving side identifies the service identification code written in the destination address field of the frame of the high-level data link, and fetches and processes only the frame to which the specific service identification code is assigned, thereby obtaining necessary reception data. Only the local area network can be transferred, thereby avoiding an unnecessary increase in the traffic volume of the local area network.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of the overall configuration of a communication system using a satellite communication control device according to the present invention.

FIG. 2 is a block diagram showing a specific configuration example of a satellite communication control device according to the present invention.

FIG. 3 is an explanatory diagram showing a frame configuration of data transmission used in the satellite communication control device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Local area network 3 Local area network 5 LAN transmission line 7 Workstation 9 Satellite communication control apparatus 11 Satellite communication transmitting station 13 Satellite communication receiving station 15 Control terminal 41 Local area network controller (LA)
N controller) 43 CPU 45 High-level data link controller (HDLC)
Controller 47 SRAM 51 Direct memory access controller (DMA)
controller)

Claims (3)

(57) [Claims] 1. A local area network controller, a high-level data link controller, a memory, and a direct memory access controller, wherein the direct memory access controller receives a signal from the local area network controller to the memory. Transferring the data obtained by removing the preamble and the frame check sequence from the transmission frame, and transferring the data from the memory to the high-level data link controller; and transmitting the high-level data link frame from the high-level data link controller. Transferring only the data of the information field to the memory, and transferring the data from the memory to the local area network controller; The high-level data link controller writes all of the data transferred from the memory into an information field, and adds a flag, a destination address, and a frame check sequence to the information field, and And outputting the frame to a satellite communication transmitting station, and inputting a high-level data link frame from the satellite communication receiving station. The local area network controller includes a preamble for data transferred from the memory. And a frame check sequence to generate a transmission frame of the local area network, output the frame to the local area network, and output the frame of the local area network from the local area network. And it is configured to enter the transmission frame, it satellite communication control apparatus according to claim. 2. The high-level data link controller has a function of writing a service identification code indicating a type of information service in a destination address field held by a frame of the high-level data link. The satellite communication control device according to claim 1. 3. The high-level data link controller identifies a service identification code written in a destination address field held by a high-level data link frame, and assigns a specific service identification code to the frame. The satellite communication control device according to claim 1 or 2, wherein the satellite communication control device is configured to take in only the data.