JPH0758779A - Data transmission system - Google Patents

Abstract

PURPOSE:To receive ATM signals and STM signals in common, to transfer them inside a system, to return them to the original ATM signals and STM signals again and to transfer them. CONSTITUTION:A free cell detection circuit 12 detects the free cells of the ATM signals and outputs detection signals, a mode switching circuit 14 generates synchronizing pattern signals from synchronizing signals S2 and detection signals and a synchronizing pattern insertion circuit 16 receives and encodes input signals S1, inserts the synchronizing pattern signals and outputs them. A transmission circuit 18 transmits encoded signals through a transmission line 100, a reception circuit 22 receives the encoded signals and a synchronizing pattern detection circuit 24 decodes the encoded signals, detects the synchronizing pattern signals at the time and outputs them. A cell boundary signal generation circuit 26 outputs the cell boundary signals of the ATM signals based on the synchronizing pattern signals and the mode switching circuit 28 outputs the cell boundary signals from the cell boundary signal generation circuit 26 in synchronism with the ATM signals and outputs the synchronizing signals of a clock rate from the synchronizing pattern detection circuit 24 in synchronism with the STM signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission system, for example, a data transmission system used in a station device.

[0002]

2. Description of the Related Art In recent years, public telecommunications networks use ISDN (Integrated ser
vices digital network), and as a broadband service, BISDN (Broadcast integrated servicing)
Ices digital network) is under development and research. As a switching method suitable for these networks,
Asynchronous Transfer Mode (ATM) switching schemes with fixed length cells have received attention. This ATM switching system packetizes information in frames, so-called cell units, which have a shorter data length than conventional variable-length frame signals, and are transferred by high-speed switching. is there.

Conventionally, as a data transmission system for handling such fixed length cells, there is one disclosed in Japanese Patent Application No. 1-287947. In this system, ATM cells input to the transmitting side device are distinguished into valid cells containing valid signals and empty cells not containing valid signals according to the identification signal indicating the boundary of the cells, and the input ATM cell signal is further classified. It encodes according to a predetermined encoding method, inserts a specific synchronization pattern for empty cells and then outputs it, and the receiving side device recognizes the specific synchronization pattern from the input signal to identify the boundary of the ATM cell signal, The cell boundary signal of the ATM cell signal is output every cell length of the cell signal, and the ATM cell signal is decoded and output according to a predetermined coding method.

[0004]

However, as described above, the conventional technique has a problem that it cannot be applied to an existing communication system handling STM signals because it processes only ATM signals. In other words, in existing communication systems, there is an STM signal system in which variable length frames are synchronously transmitted in bit serial.Therefore, in a communication system that handles both STM and ATM signals, STM and A separate device for handling the signal system is required, which is unsuitable for reducing the cost of the system.

An object of the present invention is to solve the problems of the prior art and to provide a data transmission system which can be flexibly applied to ATM cell signals and STM signals in the same device.

[0006]

In order to solve the above-mentioned problems, a data transmission system of the present invention is a system which receives an ATM signal transmitted asynchronously and an STM signal transmitted synchronously from the outside. In a data transmission system in which data is sequentially transferred from an internal transmission side device to a reception side device and then transmitted again to the outside, the transmission side device receives the ATM signal or STM signal, and when receiving the ATM signal, the boundary of the ATM signal is received. An invalid cell detecting means for outputting an invalid cell detection signal corresponding to an invalid cell by distinguishing between a valid cell containing a valid signal and an invalid cell not containing a valid signal according to the identification signal
First mode switching means for selecting a sync signal of the invalid cell detection signal and the STM signal and generating a sync pattern insertion signal based on these detection signals to switch between the ATM signal compatible and the STM signal compatible, and the ATM signal and the STM signal Sync pattern inserting means for coding a signal according to a predetermined coding and inserting a specific sync pattern not included in the code at the time of coding into the coded signal based on the sync pattern inserting signal from the mode switching means; , And a transmitting means for transmitting each signal encoded by the synchronizing pattern inserting means to the receiving side device, and the receiving side device receives the signal transmitted from the transmitting side device to perform waveform shaping and logical identification. Receiving means for performing, and detecting a specific synchronization pattern included in the signal processed by this receiving means to output a synchronization pattern detection signal,
And a sync pattern detecting means for restoring the received signal according to a predetermined coding method, and a cell boundary signal generating means for outputting a cell boundary signal corresponding to the length of the ATM signal based on the detection signal from the sync pattern detecting means. And a second mode switching means for selecting and switching the cell boundary signal and outputting the selected signal.

In this case, the synchronization pattern insertion means of the transmission side device, based on the synchronization pattern insertion signal from the mode switching means, provides a part of the input encoded signal with a specific code which is not included in the encoding code. The sync pattern including means is inserted, and the sync pattern detecting means of the receiving side device detects the sync pattern of the invalid cell of the ATM signal based on the sync pattern inserted by the sync pattern inserting means.

On the other hand, in the data transmission system according to the present invention, basically, the ATM signals are transmitted asynchronously and cell boundary signals representing the boundaries of the transmission signals are added, and all signals are synchronized and transmitted. In the transmission side device of the data transmission system that receives the STM signal from the outside and transfers it inside the system, this device uses the ATM signal or
Receiving the STM signal, when receiving the ATM signal, it distinguishes between valid cells that contain valid signals and invalid cells that do not contain valid signals according to the cell boundary identification signal, and generates invalid cell detection signals corresponding to invalid cells. Mode detection means that outputs the invalid cell detection signal and the synchronization signal of the invalid cell detection signal or the STM signal, generates a synchronization pattern insertion signal based on these detection signals, and switches the mode between ATM signal compatible and STM signal compatible. And the ATM signal and the STM signal are encoded according to a predetermined encoding, and a specific synchronization pattern not included in the encoding code is inserted into the encoded signal based on the synchronization pattern insertion signal from the mode switching means. It has a synchronization pattern insertion means and a transmission means for transmitting each signal encoded by this synchronization pattern insertion means.

In addition, in the data transmission system according to the present invention, basically, the ATM signal is transmitted asynchronously and cell boundary signals representing the boundaries of the transmission signal are added, and all signals are synchronized and transmitted. In the receiving side device of the data transmission system that receives the STM signal from the outside and transfers it inside the system, this device receives the coded signal coded according to the predetermined coding system inside the system. Receiving means for performing waveform shaping and logical identification, detecting a specific synchronization pattern included in the signal processed by this receiving means, outputting a synchronization pattern detection signal, and restoring the received signal in accordance with a predetermined encoding method. A cell boundary signal that outputs a cell boundary signal corresponding to the length of the ATM signal based on the synchronization pattern detection means and the detection signal from this synchronization pattern detection means Raw unit, and has a mode switching means for switching and outputting by selecting a synchronization pattern detection signal and the cell boundary signal.

[0010]

According to the data transmission system of the present invention, when an ATM signal or an STM signal is received from the outside of the device to the transmitting side device, the invalid cell detecting means detects the AT signal when the ATM signal is received.
According to the identification signal indicating the boundary of the M signal, a valid cell including a valid signal and an invalid cell not including a valid signal are distinguished and an invalid cell detection signal is output corresponding to the invalid cell. Receiving this, the first mode switching means selects the sync signal of the invalid cell detection signal and the STM signal, generates the sync pattern insertion signal based on these detection signals, and switches between the ATM signal compatible and the STM signal compatible. . This switching signal is sent to the synchronization pattern inserting means, which means the ATM signal and
Each STM signal is encoded according to a predetermined encoding, and a specific synchronization pattern is inserted into the encoded signal based on the synchronization pattern insertion signal from the mode switching means. The respective signals encoded by the synchronization pattern inserting means are transmitted to the receiving side device via the transmitting means.

In the receiving side device, when the signal transmitted from the transmitting side device is received by the receiving means for waveform shaping and logical identification, a specific synchronization pattern included in the signal processed by this receiving means is synchronized. The pattern detecting means detects and outputs a synchronization pattern detection signal, and further restores the received signal according to a predetermined encoding method. When the cell boundary signal generating means outputs the cell boundary signal corresponding to the length of the ATM signal on the basis of the detection signal from the synchronization pattern detecting means, the second mode switching means causes the second mode switching means to detect the synchronization pattern detecting signal and the cell boundary. Signal and select to switch between ATM signal and ST
Return each M signal to its original state and output it to the outside.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the data transmission system according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an embodiment of a data transmission system according to the present invention. In the figure, the transmitting side device 10 is an intra-station device which receives respective signals from the ATM line or STM line, encodes these signals by a predetermined encoding method, and outputs them to the intra-station transmission line 100. The receiving-side device 20 is an in-station device that decodes the coded signal from the transmission path 100 based on a predetermined coding method and outputs the decoded signal to the external transmission path. In addition, in FIG.
Only the basic configuration of the system is shown, and parts that are not directly related to the understanding of the present invention are omitted.

Explaining the details of each part, the transmitting side device 10
Has an empty cell detection circuit 12, a mode switching circuit 14, a synchronization pattern insertion circuit 16, and a transmission circuit 18. The empty cell detection circuit 12 is a circuit that is connected to an ATM line or an STM line and detects the respective signals and synchronization signals. In particular, when a fixed length cell is received from an ATM line and a cell identification signal sent in synchronization with the beginning of the cell is detected, a valid cell is detected from the input signal and other invalid cell parts are detected as empty cells. , And outputs detection signals of these valid cells and empty cells, respectively. The mode switching circuit 14 is connected to the output of the empty cell detection circuit 12 and the synchronization signal input, respectively, and switches them according to the STM signal system and the ATM signal system.The mode setting signal S3 at the time of line switching is used. To switch. In the case of the STM signal, the synchronizing signal S2 is directly received and the synchronizing signal of the clock rate synchronized with the STM signal is outputted, and in the case of the ATM signal, the detection signal from the empty cell detecting circuit 12 is outputted as the synchronizing pattern signal. The synchronization pattern insertion circuit 16 includes an encoding circuit that receives an input signal S1 from the line, encodes these by a predetermined encoding method, and outputs the encoded signals. In this embodiment, the sync pattern signal from the mode switching circuit 14 is inserted into a predetermined position of the encoded signal and output. At this time, the sync pattern signal is inserted as a coded signal of a specific pattern that is not included in the coded signal when the actual signal is coded. The transmission circuit 18 is a circuit that modulates the coded signal from the synchronization pattern insertion circuit 16 into the transmission path 100 by a predetermined modulation circuit and transmits the modulated signal.

On the other hand, the receiving side device 20 comprises a receiving circuit 22, a synchronization pattern detecting circuit 24, a cell boundary signal generating circuit 26,
And a mode switching circuit 28. The receiving circuit 22 is a transmission line
It is a circuit that performs waveform shaping and logic identification of an encoded signal received via 100 and outputs the result. The synchronization pattern detection circuit 24 includes a decoding circuit for decoding the encoded signal received from the reception circuit 22, and further extracts the synchronization pattern signal in the encoded signal. The cell boundary signal generation circuit 26 receives the synchronization pattern signal from the synchronization pattern detection circuit 24 and generates a cell boundary signal indicating the head of the cell. The mode switching circuit 28 switches in response to the mode setting r2 at the time of line switching,
A circuit that outputs a sync signal based on the sync pattern signal from the sync pattern detection circuit 24 during a line, and outputs the cell identification signal from the cell boundary signal generation circuit 26 as a sync signal to the external transmission line during an ATM line. Is.

To explain the operation, first, when the ATM line is selected, a switching signal for selecting the mode switching circuit 14 and the detection signal from the empty cell detection circuit 12 is sent from the mode setting terminal of the transmission side device 10. Then, the input of the mode switching circuit 14 is set, and the mode switching circuit 28 of the receiving side device 10 is set to select the boundary signal from the cell boundary signal generating circuit 26. Next, the ATM cell signal input to the input terminal S1 of the transmitting side device 10 is validated by the idle cell detection circuit 12 as a synchronization signal supplied from the input terminal S2, that is, a valid cell including a valid signal according to the cell boundary identification signal. It is identified as an empty cell that does not contain any signal. At this time, the empty cell detection circuit 12 supplies an empty cell detection signal to the input terminal of the mode switching circuit 14 when an empty cell is detected. In this case, the sync signal input to the input terminal of the mode switching circuit 14 also includes a boundary identification signal indicating the boundary of the ATM cell signal, and the mode switching circuit 14 selects the input terminal b according to the above setting. Detected signal is the next stage sync pattern insertion circuit
Output to 16. The sync pattern insertion circuit 16 receives the input AT
The M cell signal is encoded according to a predetermined encoding method, and at the same time, a specific synchronization pattern is inserted into the ATM cell signal after the encoding, and the ATM cell signal is output to the transmission circuit 18 in the next stage. In this case, the sync pattern insertion phase is determined by the cell detection signal from the mode switching circuit 14. Then, the transmission circuit 18
Transmits the encoded signal supplied from the synchronization pattern insertion circuit 16 to the receiving side device 20 via the transmission line 100.

The receiving side device 20 performs waveform shaping and logical identification by the receiving circuit 22 of the encoded signal from the transmitting side device 10 received at the input terminal r1 and supplies it to the synchronization pattern detecting circuit 24 of the next stage. This enables the synchronization pattern detection circuit
Reference numeral 24 decodes the received encoded signal into an original signal according to the above encoding method, and outputs an ATM cell signal from the output terminal r4 of the receiving side device. At this time, the presence or absence of a sync pattern is detected from the input coded signal, the sync pattern detection signal is extracted and supplied to the cell boundary signal generation circuit 26 of the next stage. Upon receiving this, the cell boundary signal generation circuit 26 outputs a pulse based on the cell length cycle of the transmitted ATM cell signal (for example, counting the cell length and 54 bytes by a counter),
The counter value is initialized by the input sync pattern detection signal to determine the output phase, and the output terminal of the receiving side device
The boundary identification signal synchronized with the ATM cell signal output from r4 is supplied to the mode switching circuit 28 in the next stage. In response to this, the mode switching circuit 28 selects the signal of the cell boundary signal generation circuit 26 according to the above setting, so that the output terminal r3 of the receiving side device 20 is selected.
Outputs the boundary identification signal synchronized with the ATM cell signal output from output terminal r4. As a result, the transmitting side device 10 restores an ATM signal similar to the ATM system received from the line and outputs it to, for example, an external line.

Next, when the STM line is selected, the mode switching circuit 14 is set at the mode setting terminal of the transmitting side device 10 so as to select the synchronizing signal S2, and the mode setting terminal of the receiving side device is set. The mode switching circuit 28 is switched so as to select the sync signal from the sync pattern detection circuit 24. In this state, first, the synchronization signal input to the transmission side device 10 is supplied to the input terminal of the mode switching circuit 14. In this case, the synchronization signal input to the input terminal of the mode switching circuit 14 is a frame pulse synchronized with the STM signal. The mode switching circuit 14 outputs the supplied frame pulse to the synchronization pattern insertion circuit 16 in the next stage in order to select the synchronization signal according to the above setting. Receiving this, the synchronization pattern insertion circuit 16 encodes the STM signal input to the input terminal S1 according to a predetermined encoding method, and inserts a specific synchronization pattern into the encoded signal after encoding. Output to the transmission circuit 18 in the next stage. The sync pattern insertion phase is determined by the frame pulse supplied from the mode switching circuit 14. Next, the transmission circuit 18 transmits the encoded signal from the synchronization pattern insertion circuit 16 to the reception side device 20 via the transmission line 100.

The receiving side device 20 performs waveform shaping and logical identification of the coded signal received at the input terminal r1 by the receiving circuit 22 and supplies it to the synchronization pattern detecting circuit 24 of the next stage. Receiving this, the sync pattern detection circuit 24 decodes the supplied coded signal into the original signal according to the above coding method, outputs the STM signal from the output terminal r4 of the receiving side device 20, and outputs the sync pattern from the input coded signal. The presence / absence of the signal is detected and a sync pattern detection signal is supplied to the mode switching circuit 28 at the next stage. As a result, the mode switching circuit 28 selects from the synchronization pattern detection circuit 24 according to the above setting, and therefore outputs the frame pulse synchronized with the STM signal output from the output terminal r3 of the receiving side device 20 to the output terminal r4. As a result, a signal similar to the STM signal from the STM line received by the transmission side device 10 is restored and transmitted to, for example, an external line.

As described above, according to this embodiment, when the ATM signal is input from the external line, the fixed length cell is coded,
A synchronization pattern of valid cells and empty cells is generated based on the cell boundary identification signal and inserted into the encoded signal. ST
When the M signal is input from an external line, the frame signal is encoded, a synchronization pattern is generated based on the synchronization signal of the clock rate, and the synchronization pattern is inserted into the encoded signal. This allows ATM and STM signals to be transferred as similar signals within the station. The receiving device that receives these transfer signals extracts the synchronization pattern when decoding each signal, regenerates the synchronization signals of the ATM signal and STM signal, and transmits them to the external line as the original signal. can do.

[0020]

As described above in detail, according to the data transmission system of the present invention, it is possible to flexibly apply both the ATM cell signal system and the STM signal system in the same device, and to realize a system effective for cost reduction. Can be provided. Further, by integrating the present invention into an integrated circuit, it is possible to provide a system which is effective for miniaturization.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a data transmission system according to the present invention.

[Explanation of symbols]

 10 Transmission side device 12 Empty cell detection circuit 14 Mode switching circuit 16 Synchronization pattern insertion circuit 18 Transmission circuit 20 Reception side device 22 Reception circuit 24 Synchronization pattern detection circuit 26 Cell boundary signal generation circuit 28 Mode switching circuit

Claims (4)

[Claims] 1. An ATM signal, which is basically transmitted asynchronously and is provided with a cell boundary signal representing a boundary of a transmission signal, and an STM signal which is transmitted in synchronization with all signals, are externally received. In the data transmission system in which the transmission side device inside the system sequentially transfers to the reception side device and transmits again to the outside, when the transmission side device receives the ATM signal or the STM signal and receives the ATM signal, Invalid cell detection means for generating and outputting an invalid cell detection signal corresponding to an invalid cell by distinguishing between a valid cell including a valid signal and an invalid cell not including a valid signal according to a cell boundary identification signal, and the invalid cell detection Signal and STM
First mode switching means for selecting a synchronizing signal of signals and generating a synchronizing pattern insertion signal based on the detection signal to switch between ATM signal compatible and STM signal compatible; and a predetermined code for the ATM signal and STM signal. Encoding according to the encoding method,
Sync pattern inserting means for inserting a specific sync pattern, which is not included in the code at the time of encoding, into the encoded signal based on the sync pattern inserting signal from the mode switching means, and encoding by the sync pattern inserting means And a receiving unit that transmits the respective signals to the receiving device, the receiving device receiving the signal transmitted from the transmitting device and performing waveform shaping and logical identification, and Sync pattern detecting means for detecting a specific sync pattern included in the signal processed by the receiving means, outputting a sync pattern detecting signal, and restoring the received signal according to a predetermined coding method, and the sync pattern detecting means Based on the detection signal from the AT
It has a cell boundary signal generating means for outputting a cell boundary signal corresponding to the length of the M signal, and a second mode switching means for selectively outputting the synchronization pattern detection signal and the cell boundary signal by switching. Data transmission system characterized by. 2. The data transmission system according to claim 1, wherein the synchronization pattern insertion means of the transmission side device encodes a part of the input encoded signal based on the synchronization pattern insertion signal from the mode switching means. When inserting a synchronization pattern including a specific code not included in the code at the time, the synchronization pattern detection means of the receiving side device, based on the synchronization pattern inserted by the synchronization pattern insertion means
A data transmission system characterized by detecting a synchronization pattern of empty cells of an ATM signal. 3. An ATM signal, which is basically transmitted asynchronously and is provided with a cell boundary signal representing a boundary of a transmission signal, and an STM signal which is transmitted in synchronization with all signals, are externally received. Then, in the transmitting side device of the data transmission system for transferring inside the system, the device receives the ATM signal or the STM signal, and when the ATM signal is received, the valid cell including the valid signal according to the cell boundary identification signal is received. And an invalid cell detecting means for generating and outputting an invalid cell detection signal corresponding to an invalid cell by distinguishing into an invalid cell that does not include a valid signal, and selecting the synchronization signal of the invalid cell detection signal or the STM signal, Mode switching means for generating a sync pattern insertion signal based on the detection signal and switching between ATM signal correspondence and STM signal correspondence, and encoding the ATM signal and STM signal according to a predetermined encoding A sync pattern inserting means for inserting a specific sync pattern, which is not included in the code at the time of encoding, into the encoded signal based on the sync pattern inserting signal from the mode switching means; And a transmitting means for transmitting the respective converted signals, the transmitting side device of the data transmission system. 4. An ATM signal, which is basically transmitted asynchronously and is provided with a cell boundary signal representing a boundary of a transmission signal, and an STM signal which is transmitted in synchronization with all signals, are externally received. In the receiving side device of the data transmission system for transferring inside the system, the device receives a coded signal coded according to a predetermined coding system inside the system to perform waveform shaping and logical identification. Means for detecting a specific sync pattern included in the signal processed by the receiving means and not included in the code at the time of encoding to output a sync pattern detection signal, and the received signal in a predetermined encoding method A synchronous pattern detecting means for restoring in accordance with the above, and based on a detection signal from the synchronous pattern detecting means,
Cell boundary signal generating means for outputting a cell boundary signal corresponding to the length of the ATM signal, and mode switching means for selectively outputting the synchronization pattern detection signal and the cell boundary signal by switching. Device on the receiving side of the data transmission system.