JPH044785B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] The present invention is a transmission system for a transmission device that automatically adjusts a mark determination level based on a mark rate, and includes a scramble pattern generator on the transmission section side;
It is equipped with an initial pattern change mechanism and a retransmission mechanism that detects transmission errors and retransmits them, and by scrambling the transmission frame, it improves the mark rate and increases transmission efficiency. This is a scramble transmission method that improves reliability by increasing the probability of recovery through retransmission by changing the initial scramble pattern.

[Industrial application field]

The present invention relates to a transmission device, and is particularly suitable for optical transmission, and relates to a transmission method for a transmission device that has high transmission efficiency and has a high probability of being recovered by retransmission even if a transmission error occurs.

[Conventional technology]

In recent years, optical transmission devices using optical fiber cables have been used in a wide variety of fields due to their characteristics such as being unaffected by external noise, low loss, and wide bandwidth. On the receiving side of this optical transmission device,
Dynamically change the range for detecting 0/1 of the optical signal depending on the distance of the optical fiber
An AGC (automatic gain control) circuit is used. This AGC circuit normally provides an appropriate threshold level to determine whether the signal is 1/0 when the mark rate (ratio of mark time to transmission time) in data transmitted bit serially is 50%. . As a result, if the 0 signal, that is, the space continues for too long, this threshold will be lowered, making it impossible to accurately determine the subsequent 1/0. Therefore, it was not desirable to use NRZ codes or the like.

Therefore, in conventional optical transmission systems, a 1-bit signal is expressed as 2 bits, for example, 1 signal is expressed as 1, 0, 0 signal is expressed as 0, 1, or CMI
The mark rate was set at 50% by using a redundant code such as a code or a DMI code, or the mark rate was approached to 50% by scrambling due to statistical properties.

[Problem that the invention seeks to solve]

However, the conventional optical transmission system using redundant codes described above requires twice the bandwidth as when using NRZ codes, and has the disadvantage that the transmission efficiency is halved. For this reason, it could not be said to be suitable for use in high-speed transmission in CPU systems, for example. On the other hand, optical transmission methods that involve scrambling do not have the disadvantage of decreasing transmission efficiency, but
Since we expect the mark rate to be 50% using statistical properties, there is a probability that an unsatisfactory scramble pattern with a mark rate far from 50% will occur, resulting in transmission errors. Moreover, even when retransmission is performed, it is performed using a scrambling pattern with poor conditions as described above, which poses the problem that an unrecoverable error may occur.

The present invention solves the above problems, and includes:
It is an object of the present invention to provide a scramble transmission method that does not reduce transmission efficiency and has increased reliability.

[Means for solving problems]

FIG. 1 is a block diagram illustrating the principle of the present invention.

Means for achieving the above object of the present invention is a transmission device that automatically adjusts the mark determination level on the receiving side according to the mark rate of the transmission frame, and includes a scramble pattern generator 1 that scrambles the transmission frame; The transmitting unit 4 side is equipped with an initial pattern changing mechanism 2 that changes the initial pattern of the scramble pattern generator 1, and a retransmitting mechanism 3 that detects a transmission error and retransmits the transmission frame at least once. This is a scramble transmission method in which the initial pattern of the scramble pattern generator 1 is changed when detecting and retransmitting.

[Operation] The retransmission mechanism 3 detects a transmission error by monitoring responses from the receiving side and timeouts, and performs retransmission.
When performing this retransmission, the scramble pattern generator 1 creates a scramble pattern based on an initial pattern different from the initial pattern used for the previous scramble pattern, and by performing scrambling, it is possible to eliminate scramble patterns with poor conditions. Increasing the probability of recovering a transmission error that occurs. If this retransmission is repeated, the initial pattern is changed by the initial pattern changing mechanism 2 each time, so that the probability can be further increased and the reliability can be improved. The initial pattern is sent at the beginning of the transmission frame for descrambling at the receiving end.

〔Example〕

The present invention will be explained in detail based on examples and drawings.

First, an embodiment in which the present invention is applied between a channel device and an I/O interface of a CPU system will be described. FIG. 4 is a block diagram showing an example of its application. When transmitting data between a conventional channel device and an I/O interface, direct transmission was performed using a coaxial cable or the like, but this method could only extend the distance by about 120 meters at most. That is, since an interlock is taken for each piece of data in the data transfer, the transmission speed is reduced due to the round trip delay of the signal due to the cable. Therefore, in this embodiment, an adapter 7a is installed on the channel device (hereinafter referred to as CH) 7 side, and an I/O
An adapter 8a is provided on the interface (hereinafter referred to as IF) 8 side, and optical fiber 5 is used to perform optical transmission between them, thereby making it possible to extend the transmission distance to several kilometers. The above interlock is
Between CH7 and adapter 7a and between IF8 and adapter 8
It is carried out between A and A and is not affected by delays due to optical transmission.

FIG. 2 is a circuit configuration diagram showing an example of the circuit of the adapter 7a in FIG. 4 in which the present invention is implemented. The control unit 6 gives commands and data to the circuits within the adapter to control data transfer with the CH 7 and control transmission and reception of optical transmission. Data transfer with CH7 is performed by the interlock control unit 9 by exchanging data on the BUS IN and BUS OUT lines through TAG IN and TAG OUT. Since the transmission data from CH7 is transferred asynchronously with optical transmission, data is written to a buffer memory (hereinafter referred to as BM) 10 up to a predetermined capacity, for example in block units (64 bytes). The ECC 11 is a circuit that checks and corrects errors when reading from the BM 10, and the ECCG 12 is a circuit that adds error check and correction bits during writing. light counter 13
is incremented every time a write is made to the BM10, giving a write address to the BM10, and its counter value indicates that data has been written into the BM10. The read counter 14 has an initial value set to 0 and is incremented to provide a read address when reading the BM 10 for transmission. Comparator 15 is write counter 1
3 and the value of the read counter 14, if they do not match, it is determined that the transmitted data still exists, and if a specific bit group matches, it is determined that the data is the final data.

The circuit configuration of the transmitter 4 will be described. Transmission data is transmitted in a frame structure as described later. Transmission data is read from BM10 and sent to the transmission frame register (hereinafter referred to as TFR).
16 predetermined bit positions. this
The contents of the TFR 16 are aligned to a predetermined transmission format via an EXC circuit and set in a parallel serial exchange register (hereinafter referred to as TSR) 18. The transmission data of the TSR 18 is shifted by the transmission clock and converted into a serial signal, which is then combined with the pattern generated by the scramble pattern generator (hereinafter referred to as SCR) 1 and the EOR.
Exclusive-ORed in circuit 1a, optical modulation circuit 19, and adapter 8a via optical fiber 5a.
transmitted to. The initial pattern change mechanism 2 consists of a scramble counter (hereinafter referred to as SCRC) 2a and a counter update circuit 2b, and the SCRC 2a updates the counter value via the counter update circuit 2b during retransmission at least according to instructions from the retransmission control section 3a. Ru. However, in this embodiment, as will be described later, the information is updated every time a series of block transmissions start, but it is also updated every time a series of block transmissions starts. The counter value of SCRC2a is given to SCR1a as an initial pattern, and also when transmitting the first transmission frame.
Set to TFR16. A time file generator (TFG) 20 always transmits a time file frame as a dummy when transmission data is not set in the TFR. The time file frame pattern has a mark rate of approximately 50%.

Next, the circuit configuration of the receiving section 21 will be described. The optical signal transmitted via the optical fiber 5b is identified as 1/0 via the optical demodulation circuit 22. This optical demodulation circuit 22 includes the above-mentioned AGC circuit. The demodulated signal is sent to the descrambling circuit 23.
Only the data is selectively descrambled and serial parallel exchange register (hereinafter referred to as RSR)
24 and exchanged into a parallel signal,
It is aligned to the required sequence via the EXC circuit 25 and set in the receive frame register 26. The data in the receive frame register 26 is
Error checks such as CRC check are performed,
via the control section 6 or interlock control section 9
Transferred to CH7. When the adapter 7a is the receiving side of the transmitted data, if the CRC check is an error, the control unit 6 transmits a command frame requesting retransmission. If the adapter 7a is the sending side of the transmission data, the transmission frame received is a command frame from the other side, and as described later, the subsequent data request command (RR command) and retransmission request command (RNR command) are sent. It's coming.

Next, the retransmission mechanism consists of a retransmission control section 3a and a timeout monitoring timer (hereinafter abbreviated as timer).
It consists of 3b etc. Timer 3b is set at the start of block transmission, and reset when there is a response to the subsequent data request command (RR command).
When there is no response, this timer 2b determines that there is a transmission error and retransmits. It is also possible to send multiple blocks without waiting for the response on the data sending side,
If a timeout occurs, a command can be issued to the data receiving side to request a sequence number report indicating how much data has been received, and based on that report, data will be retransmitted from the next data block. Furthermore, if the command frame from the data receiving side is an RNR command, the retransmission control unit 3a determines that there is a transmission error and retransmits the data block starting from the previous data block of the sequence number.

FIG. 3 shows an embodiment of the counter update circuit of the SCRC 2a. In this circuit example, the counter value of SCRC2a is updated every time the first frame is transmitted. That is, a block transmission request is generated, and a block transmission flip-flop (hereinafter referred to as flip-flop) is generated.
When FF (abbreviated as FF) 101 is set, if the last frame transmitted FF 102 is reset and predetermined conditions are met, the first frame transmission wait is started.
FF102 is set. Subsequently, when TFR16 becomes set effective, this timing causes
Update SCRC2a. Note that the final frame transmission wait FF 103 is set when the final frame data is detected by the comparator 15a or 15b.

Although the configuration of the adapter 7a on the CH7 side has been described above, the configuration of the adapter 8a on the IF8 side is almost the same, and data can be transmitted bidirectionally between CH7 and IF8.

The operation of this embodiment with the above configuration will be described. The transmission frame in this embodiment consists of a first frame, a predetermined number of intermediate frames, and a final frame, as shown in FIGS. 5, 6, and 7. One frame is
It consists of 40 bits and carries a 4-byte record. In each frame, FF, CC, PS, and DL codes are commonly arranged at predetermined bit positions.
FF code is a data frame identifier,
Usually it is 01, and if it is 11, it indicates a time fill. The CC code indicates whether the frame is the first frame (CC=00), intermediate frame (CC=01), or last frame (CC=00).
11). Note that in the case of a command frame, CC=10. The PS code indicates a pilot signal and is inverted to 01 and 10 every time one frame is transmitted. The beginning of the data frame at the initial time is recognized by predictive judgment of this pilot signal. The DL code indicates the valid number of data in each frame. In the first frame of Fig. 5,
The initial scramble pattern for SCP is N(S)
contains the sequence number of the data block, and the remaining record parts contain 2-byte data. The sequence number of N(S) is
A comparison check is made with the next sequence number to be received. The intermediate frame in FIG. 6 carries a maximum of 4 bytes of data. The final frame in FIG. 7 carries a maximum of 2 bytes of data and a CRC check code for data check. In this embodiment, only the above data is selectively scrambled.

Figure 8 shows a command frame, and the command part contains the above-mentioned RR command (when received normally) or RNR.
When receiving a command (when an error is received), the sequence number of the next data block to be received is specified in N(R). FIG. 9 shows a time fill frame, which is configured with a mark rate of approximately 50% and is transmitted as a dummy when the data transmission frame is not transmitted, to ensure normal operation of the AGC circuit, and
It is identified and discarded at the receiving end by the FF code.

In the retransmission mechanism 2, when the above-mentioned RNR command arrives or even after the predetermined time set in the timer 3b has elapsed since the start of block transmission,
It operates when there is no response to either the RR or RNR command from the receiving side and instructs retransmission. If the transmitted data has a pattern with a poor mark rate, it may be a CRC check error on the receiving side, or
This appears as a sequence number mismatch, so retransmission is performed in response to the RNR command in that case.
Since the initial value of the scramble pattern generator 1 is updated every time it is retransmitted, the probability that the pattern with a poor mark rate will be resolved increases.The more this retransmission is repeated, the higher the recovery rate becomes, increasing the reliability of the transmission. improves.

Note that the present invention is not limited to the above embodiments,
It can be used for other general transmissions, and can be applied to things other than optical transmission, and various applications and embodiments can be taken in accordance with the gist of the present invention.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to improve transmission efficiency through scrambled transmission, and to provide a scrambled transmission method that can improve reliability.

[Brief explanation of drawings]

Figure 1 is a block diagram for explaining the principle of the present invention, Figure 2 is a block diagram for explaining the principle of the present invention.
FIG. 3 is a circuit diagram of an adapter implementing the present invention, FIG. 3 is an embodiment of a scramble counter update circuit, and FIG. 4 is a block diagram showing an example of application of the present invention.
5 to 9 are format diagrams of transmission frames. 1... Scramble pattern generator, 2
...Initial pattern change mechanism, 2a... Scramble counter, 2b... Counter update circuit, 3...
Retransmission mechanism, 3a... Retransmission control unit, 3b... Timeout monitoring timer, 4... Transmission unit.

Claims (1)

[Claims] 1 In a transmission device that automatically adjusts the mark determination level on the receiving side according to the mark rate of the transmission frame, there is a scramble pattern generator 1 that scrambles the transmission frame, and an initial generator that changes the initial pattern of the scramble pattern generator 1. The transmitter 4 side includes a pattern change mechanism 2 and a retransmission mechanism 3 that detects a transmission error and retransmits the transmission frame at least once, and at least when detecting the transmission error and retransmitting the transmission frame, the scramble pattern generator A scrambled transmission method characterized by changing the initial pattern of the generator 1.