JPH0828736B2 - Communications system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a communication system that performs bidirectional communication by frequency multiplexing.

[Prior Art] In conventional communication systems, particularly in the field of LAN (local area network), a transmission method such as a baseband type, a broadband type, or an optical fiber type is used. Various products such as communication devices of different systems have been announced. Also, CATV has been put to practical use for video signal transmission.

On the other hand, in terms of the switching function corresponding to these various transmission methods, the electronic exchange is still the mainstream, and the current situation is that the research of the optical exchange is being done with the spread of optical communication.

[Problems to be Solved by the Invention] The above conventional example has the following problems.

(1) When performing bidirectional video transmission using CATV,
The line amplifier becomes very expensive and the channel allocation becomes strict. Also, it is difficult for specific subscribers to communicate with each other.

(2) When exchange is performed using an electronic exchange, quality deterioration due to crosstalk occurs during transmission of high frequency signals. Further, in order to perform an arbitrary N-to-N exchange, an N × N circuit scale is required, and when the subscriber system N increases, the circuit scale increases in proportion to the square of N.

(3) Although researches on optical switching equipment are actively conducted, they have not yet reached the stage of practical use.

(4) It is difficult for existing LANs to cope with an increase in transmission capacity.

The present invention has been made in view of the above conventional example, by performing communication between nodes with a signal having a frequency different from the frequency of the signal transmitted between nodes having a plurality of terminals,
An object of the present invention is to provide a communication system capable of performing inter-node communication and intra-node communication independently.

Another object of the present invention is to provide a communication system capable of using a frequency with little attenuation in long distance transmission even for a destination node located at a long distance.

[Means for Solving Problems] In order to achieve the above object, the communication system of the present invention has the following configuration. That is, a communication system having a plurality of terminals connected to each other via a communication line, each of the plurality of nodes being connected via a communication line, wherein the terminal transmits transmission data at a first frequency. Of the plurality of frequency signals output from the terminals in the node, the output means modulating and outputting the signal and the receiving means receiving the signal of the second frequency. Multiplexing means for distributing to each terminal in the node, control means for performing frequency tuning between the transmitting side terminal and the receiving side terminal between the nodes and within the node, and a frequency for converting the frequency of the signal transmitted between the nodes And a conversion means.

[Operation] In the above configuration, the terminal can receive the second frequency signal while modulating the transmission data into the signal of the first frequency and outputting the signal, and each of the plurality of nodes can
A plurality of frequency signals output from the terminals in the node are multiplexed and distributed to each terminal in the node, and frequency tuning is performed between the transmission side terminal and the reception side terminal between and within the nodes. Further, it is possible to perform the inter-node communication by converting the frequency of the signal transmitted between the nodes.

[Embodiment] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[Description of Communication System (FIG. 1)] FIG. 1 is a diagram showing the basic configuration of the communication system of the first embodiment.

Each terminal 3-1 to 3-i (i is an arbitrary positive integer) is connected to a pair of input / output ports of the multiplexing circuit 1 via the corresponding interface unit (I / F) 2-1 to 2-i. Has been done. One input signal line and one output signal line are connected to each input / output port of the multiplex circuit 1, and the multiplex circuit 1 inputs and outputs signals of different frequencies from each terminal. A frequency division multiplexed signal in which the frequency signal from each terminal is superimposed on the signal line for output is output. The controller 4 passes through the multiplex circuit 1 to each interface circuit 2-1 to 2-2.
-Updates with i and controls connection and communication between each terminal.

[Explanation of Interface Unit (FIG. 2)] FIG. 2 is a diagram showing the structure and connection of the interface unit 2, and the same parts as those in FIG. 1 are designated by the same symbols.

The transmission data 20 from the terminal 3 is modulated by the modulator 21 into a signal having a frequency designated by the CPU 22. The multiplexer 23 multiplexes the modulated signal 24 from the modulator 21 and the control signal of the CPU 22 and outputs the multiplexed signal to the multiplexing circuit 1. On the other hand, the frequency signal 25 input from the multiplexing circuit 1 is demultiplexed by the demultiplexer 26 including a band filter and a band elimination filter, and the demultiplexed frequency signals are input to the CPU 22 and the variable tuner 27, respectively. To be done. The variable tuner 27 tunes the input signal at the frequency instructed by the CPU 22, demodulates the modulated input signal, and outputs it as received data 28 to the terminal.

With the above configuration, the terminal 3 is another terminal 3 in the same node.
-When you want to communicate with n, specify the terminal you want to communicate with CPU22 via bus 29. As a result, the CPU 22 outputs the calling of the partner terminal 3-n and the partner designation data (control signal) to the multiplexing circuit 1 through the multiplexer 23 and transmits it to the controller 4.

Upon receiving the control signal, the controller 4 outputs the reception frequency and the transmission frequency of the partner terminal 3-n to the multiplexing circuit 1 as a response. The interface circuit 2 inputs this signal by the demultiplexer 26. CPU 22 uses the frequency of the other side terminal based on the signal of the duplexer 26 (transmission / reception frequency)
When it recognizes, the modulator 21 and the variable tuner 27 are adjusted to the reception frequency and the transmission frequency of the partner terminal, respectively. The frequency may be tuned so that the other terminal (terminal 3-n in this case) tunes to the frequency of the communication request terminal (terminal 3). Alternatively, the transmission frequency from each terminal may be fixed, and the tuning frequency of the variable tuner 27 on the receiving side may be adjusted to the transmission frequency of the other terminal.

Further, if there is an unused frequency band among the frequency bands available in the present communication network (node), the controller 4 may allocate the frequency band to the communication requesting terminal.

By doing so, it is possible to easily add or reduce terminals in the communication system.

[Explanation of Controller Operation (FIGS. 1 to 3)] FIG. 3 is a flow chart of pre-processing of communication by the controller 4, and this program is started by communication request from the interface section 2.

First, in step S2, the interface section 2 of the terminal 3
The other terminal with which the terminal 3 wishes to communicate (for example, the terminal 3-2
Input), the process proceeds to step S2, where a communication request is sent to the interface section 2-2 of the terminal 3-2 and the operation of the terminal 3-2 is checked at step S2. In step S3, it is checked whether the terminal 3-2 can communicate, and if not, the process proceeds to step S4 and the terminal 3-2 is connected to the terminal 3.
Is notified via the bus 29 that the communication is not possible, and the processing ends.

If terminal 3-2 can communicate with step S3, step
In step S5, the frequency band not currently used in the communication network is checked, and in step S6, the terminal 3 and the terminal 3-2 are instructed as the transmission or reception frequency. In accordance with this instruction, the interface unit of each terminal changes either or both of the transmission and reception frequencies to perform communication. If the transmission frequency of each terminal is fixed, the controller 4 omits step S5, and in step S6, the interface section of each terminal is instructed to the transmission frequency of the other terminal, and each interface section uses a variable tuner. It is only necessary to set the tuning frequency of the above to the instructed frequency.

[Explanation of the operation of the interface unit (Figs. 2 and 4)] Fig. 4 is a flow chart of a program for communication pre-processing by the interface unit. This program is the CPU2 of Fig. 2.
It is stored in ROM2. It should be noted that this program is started by a communication instruction from the connected terminal.

This flow chart shows the operation executed corresponding to the operation of the controller 4 shown in FIG.
When there is a further communication request, the process proceeds to step S10, where the multiplexer 23,
Through the multiplex circuit 1, the controller 4 is designated with the partner terminal with which communication is desired. At step S11, the response from the controller 4 input via the multiplex circuit 1 and the demultiplexer 26 is waited for, and at step S12 it is checked whether the other terminal can communicate.

If communication is not possible, the process proceeds to step S13 and the terminal 3 is notified to that effect, and the process ends, but if communication is possible with the partner terminal, the process proceeds to step S14, and the transmission or reception frequency instructed by the controller 4 is responded to. In order to do so, either or both of the modulation frequency of the modulator 21 and the tuning frequency of the variable tuner 27 are set, and communication is started in step S15. Needless to say, the frequency setting here corresponds to the frequency instructed by the controller 4 in step S6 of FIG. 3 as described above.

[Description of Second Embodiment (FIGS. 5 to 7)] FIG. 5 is a diagram showing a configuration of the entire communication system of the second embodiment.

FIG. 6 is a diagram showing a configuration of an optical star coupler node corresponding to each node which is a basic unit in the configuration of this system.

In each node, each terminal 12 (12a to 12c) is connected to the corresponding interface section 11 (11a to 11c), and each interface section 11 is connected to the optical star coupler 10 via the optical fiber cable 16 (16a to 16c). Are connected to a corresponding pair of input / output ports. Further, the optical star coupler 10 is connected to a controller 13 and a remote bridge 14 for transmitting data between nodes at a long distance, and the remote bridge 14 is connected to the controller 13 via a bus 15 and controlled. There is. The operation of the controller 13 in the case of intra-node communication is basically the same as the operation of the controller 4 of the first embodiment.

Each node (node 1 to node 3) in FIG. 5 corresponds to the node shown in FIG. 6, and is for long distance between the remote bridges (14-1 to 14-6) of each node. The communication line 17 is an NTT dedicated line, an optical fiber line or the like, and the control line 18 between the controllers is composed of a telephone line or the like, and the controllers execute control by sending and receiving control signals to and from each other.

With this configuration, it is possible to communicate via a plurality of nodes. At this time, the combination of the remote bridge 14 and the controller 13 causes the entire node to function as a repeater having a relay function.

The optical star coupler 10 has n fibers connected to the input / output ports, and a pair of input / output lines of the corresponding ports are connected to the interface unit 11 or the controller 13 and the remote bridge 14. At this time, a signal in which the frequencies of the input signals of all the input ports are superimposed is output to the signal line of any output port. Each interface section selectively receives this signal at a desired frequency.

At least one controller 13 is arranged in the node, and is connected to the interface section 11 via the optical star coupler 10 and to the remote bridge 14 by a bus line 15. In addition to the line status in the node, "connection" and "disconnection" of the line, and the switching function, all controls such as billing management are performed. At the same time, in long-distance node-to-node communication, since the controllers are connected to each other via a public telephone line via a modem, mutual control such as frequency allocation of line channels can be performed by handshake.

7 (A) and 7 (B) are diagrams showing a specific example of the unidirectional optical star coupler used in this embodiment.

FIG. 7A is a diagram showing an optical star coupler having a direct biconical taper structure, in which a plurality of optical fiber cables are fused at a portion 70. FIG. 7B shows a concentrated coupling type optical star coupler by the flat plate mixer 71.

[Explanation of Interface Unit (FIG. 8)] FIG. 8 is a diagram showing the configuration of the interface unit 11 connected to each terminal. The same portions as the configuration of the interface unit 2 shown in FIG. 2 are the same. It is indicated by a symbol. The operation of the communication pre-processing of the CPU 22 is the same as that of the flowchart shown in FIG.

Briefly explaining the transmission / reception operation, the interface unit 11
In the transmission system of, the transmission data 20 is modulated by the modulator 21 at the carrier frequency assigned to the own channel by the controller 13 or a unique carrier frequency, and the control signal from the CPU 22 (response to each check, calling and It is sent after being combined with the other party's designation). The electric-optical (E / O) converter 80 converts the electric signal from the multiplexer 23 into an optical signal and sends it to the optical star coupler 10.

On the other hand, the receiving system will be described. An optical reception signal 83 including a control signal from the controller 13 (fault check, in-use check, tuner control, ringing signal, etc.) and a signal from each terminal is an optical-electrical (O / E) It is converted into an electric signal by the device 82, separated by the demultiplexer 26 and sent to the CPU 22 and the variable tuner unit 27. The CPU 22 inputs a transmission / reception frequency setting instruction from the controller 13 via the demultiplexer 26, and sets the tuning frequency of the variable tuner unit 27 or the modulation frequency of the modulator 21. As a result, the variable tuner unit 27 selectively receives only the natural frequency of the communication destination among the received signals from the optical star coupler 10 and outputs it to the terminal 3.

[Description of Remote Bridge (FIG. 9)] FIG. 9 is a diagram showing the configuration of the remote bridge 14.

The remote bridge 14 is used during communication between the optical star couplers 10 (between the nodes), and the remote bridge 14 is connected to a pair of input / output ports of the optical star coupler 10 with an optical fiber cable, and is connected to an NTT dedicated line or It is connected to a long-distance line 17 such as an optical fiber.

The signal from the optical star coupler 10 is converted into an electric signal by the O / E converter 90, and then the bus line 15 is converted by the controller 13.
They are separated by the branching filter 91 (variable tuner group) which is controlled via the. This demultiplexed signal is converted to the frequency assigned to the long-distance transmission channel by the controller.
VFO 92-1 to 92-n are controlled by the signal from 13 and mixer 9
Convert with 3-1 to 93-n. After that, the signal is sent to the long-distance line 17 by the driver 95 through the multiplexer 94. However, at this time, if the line 17 is an optical fiber, the E / O converter 96 is required.

On the other hand, the signal from the long distance line is received by the receiver 98 (when the line 17 is an optical fiber, the O / E converter 97
The optical signal is converted into an optical signal by the E / O converter 99 and then sent to the optical star coupler 10. However, when the long-distance line 17 is a high-speed digital line, the above function is performed by digital processing.

[Description of Controller Operation (FIG. 10)] FIG. 10 is a flow chart of communication preprocessing by the controller 13, and this program is started by communication request from the interface unit 11 corresponding to the terminal in the node.

First, in step S20, the interface unit 11 of the terminal 12 inputs a command for designating the other terminal with which the terminal 12 desires to communicate. If the partner terminal is a terminal within the same node, the process proceeds to step S22 to check whether the partner terminal can communicate. The operation of steps S23 to S27 is the same as the operation of steps S3 to S7 in FIG.

If the other terminal is not in the same node in step S21, the process proceeds to step S28 and the other node controller
For example, through the control line 18 such as a public telephone line,
It conveys terminal instructions and usable long-distance transmission and reception frequencies. The other party's controller checks if the instructed terminal can communicate, and when it returns the status, checks in step S29 if the other terminal can communicate, and if it cannot communicate, proceeds to step S24 and cannot communicate. Is notified to the communication requesting terminal, and the processing ends.

On the other hand, when communication is possible, the controller of the node on the other side checks the free frequency band in the node among the frequencies that can be transmitted / received on the node (the node on the other side) to determine the transmission frequency f _x and the reception frequency f _y . decide. Then, the carrier frequency of the remote bridge of the node is set to f _x, and the frequency is notified to the communication requesting node via the line 18. This causes the controller of the node desiring communication to input the above-mentioned frequencies f _x and f _y via the control line 18 at step S30, and at step S31 the optical fiber cable 16 and the optical fiber cable 16 to the communication desiring terminal in the own node. The transmission / reception frequency is designated via the star coupler 10.

As a result, the interface unit corresponding to the communication requesting terminal
11 sets the tuning frequency of the variable tuner 27 to f _x .
It is needless to say that this frequency may be set for either or both of the transmission frequency and the reception frequency as required.

In step S32, the duplexer 91 of the remote bridge 14 is controlled to set the carrier frequency of the terminal desired to communicate, and VF
O92-i is controlled and the frequency f
Output as _y .

[Explanation of frequency band (FIG. 11)] FIG. 11 is a diagram showing a frequency band used in this embodiment.
Band 110 is assigned to a control signal between controllers between nodes, and band 111 shows a frequency band of a signal used between remote bridges for long distance. Since lower frequencies have less attenuation in this way, a relatively low frequency band is used for long distances.

Band 112 is a transmission / reception frequency band for short distances used between interface units in each node, and the bandwidth of one video channel (including audio) is 6MHz, and analog AM modulation is applied to this signal to 6MHz. On the other hand, a guard band of 6 MHz is provided for each, and 10 channels for long-distance lines (band 111) and 20 channels for short-distance channels (band 112) are allocated.

At this time, the communication within the node is completely independent,
The same channel can be assigned to each node, while the communication between nodes requires the assignment of a common channel throughout the system.

As described above, the present embodiment has the following effects.

(1) By combining an optical star coupler, a controller (personal computer class) and an interface, it becomes possible to construct a video interactive network system having a simple exchange function.

(2) Although N × N can be arbitrarily exchanged, since it is an exchange method by frequency separation, it does not require an N × N circuit scale, and it is small and lightweight, and can handle a large capacity.

(3) Due to the systemization by the distributed control method of controlling in units of nodes, it is possible to easily cope with the expansion and contraction of the system scale, and at the same time, it is possible to easily cope with the increase of the transmission capacity by wavelength multiplexing.

(4) The system configuration becomes very simple by using the public telephone line only when the line for long distance transmission is opened.

(5) Crosstalk of high-frequency signals can be reduced compared to the exchange transmission of mechanical relays, and a high-quality exchange transmission line can be realized.

[Effects of the Invention] As described above, according to the present invention, communication between nodes is performed by performing communication between nodes with a signal having a frequency different from the frequency of a signal transmitted between nodes having a plurality of terminals. There is an effect that communication within a node can be performed independently.

Further, according to the present invention, it is possible to use a frequency with low attenuation in long-distance transmission even for a destination node located at a long distance.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of a communication system according to the first embodiment, FIG. 2 is a diagram showing a configuration of an interface unit according to the first embodiment and connections thereof, and FIG. 3 is a first embodiment. 4 is a flow chart showing the pre-processing of the communication by the controller of FIG. 4, FIG. 4 is a flow chart showing the pre-processing of the communication by the interface section of the first embodiment, and FIG. 5 is the overall configuration of the communication system of the second embodiment. FIG. 6 is a diagram showing a configuration of an optical star coupler node corresponding to each node on the configuration of the present system, and FIGS. 7 (A) and (B) are diagrams showing a specific example of the optical star coupler. FIG. 8 is a diagram showing a configuration of an interface unit of the second embodiment, FIG. 9 is a diagram showing a configuration of a remote fridge, and FIG. 10 is a flow chart of communication preprocessing by the controller of the second embodiment. Fig. 11 shows the frequency band used in this example. It illustrates. In the figure, 1 ... Multiplex circuit, 2,11 ... Interface section (I /
F), 3,12 ... Terminal, 4,13 ... Controller, 10 ... Optical star coupler, 14 ... Remote bridge, 21 ... Modulator, 22 ... CPU, 23 ... Multiplexer, 26 …… Splitter, 27 ……
Variable tuner, 80,99 ... Electric-optical (E / O) converter, 82,9
0 …… Optical-electric (O / E) converter, 91 …… Splitter, 92 …… VF
O, 93 …… Mixer, 94 …… Multiplexer, 95 …… Driver, 98
...... It is a receiver.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H04J 14/00 14/02 H04B 9/00 N (72) Inventor Genmei Miura 3 Shimomaruko Ota-ku, Tokyo Canon No. 30-2 (56) References JP-A-56-98949 (JP, A) JP-A-57-50142 (JP, A) JP-A-58-120330 (JP, A) JP-A 59-215135 (JP, A) JP-A-63-74238 (JP, A)

Claims (1)

[Claims] 1. A communication system having a plurality of terminals, each of which is connected to a plurality of nodes via a communication line, and each of the plurality of nodes being connected to the communication line, An output unit that modulates and outputs a signal of a frequency of 1 and a reception unit that receives a signal of a second frequency, and each of the plurality of nodes outputs a plurality of frequency signals output from terminals in the node. Multiplexing means for multiplexing and distributing to each terminal in the node, control means for performing frequency tuning between the transmitting side terminal and the receiving side terminal within the node and within the node, and the frequency of the signal transmitted between the nodes A communication system comprising: a frequency conversion means for converting.