JPH05122209A - Closed area digital wired communication system - Google Patents

Abstract

PURPOSE:To simplify the configuration of a synchronization detection circuit of terminal equipment and to improve the transmission efficiency by utilizing code rule violation for synchronization establishment between terminal equipment. CONSTITUTION:Terminal equipment 12 on a sender side is provided with a code rule violation signal addition section 15, a code rule violation (CRV) signal is added to a head of a transmission signal and the result is sent to a transmission medium 11, a terminal equipment 13 at a receiver side is provided with a code rule violation signal detection section 17, and when the detection section 17 detects a code rule violation signal, a clock fed from an oscillation section 18 is frequency-divided to reset a frequency divider section 19 generating a prescribed clock thereby establishing the synchronization between the terminal equipment 12 on the sender side and the terminal equipment 13 on the receiver side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a closed digital wired communication system for establishing synchronization between terminals in order to guarantee the accuracy of transmission when a communication signal is encoded and transmitted.

[0002]

2. Description of the Related Art In recent years, closed area digital cable communication systems for the purpose of communication within the area have been developed in various places. In a system where multiple terminals communicate with each other in a closed area using a single transmission medium, a time division multiplexing method in which a frame composed of multiple time slots is repeated is used as the transmission method. Decode the data by extracting the required time slots. The receiving side identifies the first time slot in order to identify the beginning of the time slot in the frame, measures the time difference from the first time slot, and transmits / receives data. Hereinafter, a conventional closed area digital cable communication system will be described.

FIG. 4 shows the configuration of a conventional closed area digital cable communication system. In FIG. 4, 1 is a transmission medium. 2 is a terminal on the transmitting side, and 3 is a terminal on the receiving side. The number of terminals accommodated is two or more. Receiving terminal 3
Is a data decoding unit 4, a clock detection unit 5 configured by a PLL or the like, and a clock generation unit 6 configured by a VCO or the like.
And a data processing unit 7 including a microcomputer and the like.

FIG. 5 shows the structure of a conventional transmission signal. The transmission signal 8 is composed of a pre-signal (preamble) 9 and a transmission information signal 10.

The operation of the closed-range digital cable communication system configured as described above will be described below. First, when the terminal 2 communicates with each other as a sender and the terminal 3 as a receiver, the transmission signal 8 transmitted by the terminal 2 is
It is transmitted to the terminal 3 via the transmission medium 1 such as an optical fiber. The waveform of the transmission signal 8 is distorted when propagating through the transmission medium 1. The clock detection unit 5 extracts the clock component in the transmission signal 8 and transmits it to the clock generation unit 6, and the data decoding unit 4 extracts the necessary information from the transmission information signal 10 of the transmission signal 8 and the data processing unit. Process 7

[0006]

However, in the above-mentioned conventional closed area digital cable communication system, the transmission medium 1 is used.
In order to receive data normally without being affected by the transmission path error caused by the distortion caused by the clock, it is necessary to recover the clock from the received signal. Therefore, there is a problem that the circuit configurations of the clock detection unit 5 and the clock generation unit 6 become complicated, which causes a cost increase. Further, the advance signal 9 increases in proportion to the amount of information of the transmission information signal 10 and has, for example, several tens of bits, which causes a problem of a decrease in transmission efficiency.

SUMMARY OF THE INVENTION The present invention is intended to solve such a conventional problem, and an object thereof is to provide a closed-range digital wired communication system having a simple circuit configuration, excellent economical efficiency, and high transmission efficiency.

[0008]

In order to achieve the above object, the present invention intentionally adds a code conversion rule violation signal to the beginning of a signal transmitted by a transmitting terminal or center device on a transmission medium. The signal is transmitted, and the receiving side terminal detects the code conversion rule violation signal and generates the sample clock of the received data in synchronization with the timing.

[0009]

According to the present invention, with the above configuration, the terminal which receives the code conversion rule violation signal detects the beginning of the transmission signal by the signal and generates the sample clock of the reception data in synchronization with the timing. The configuration can be simplified and the transmission efficiency can be improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a closed digital cable communication system according to an embodiment of the present invention. In FIG. 1, 11 is a transmission medium such as an optical fiber,
Reference numeral 12 is a transmission side terminal, and 13 is a reception side terminal. The terminal 12 on the transmission side is provided with a coding rule violation signal adding section 15 in the data coding section 14. The terminal 13 on the receiving side is provided with a coding rule violation signal detecting section 17 in its data decoding section 16, and further, an oscillating section 18 for generating a signal having a frequency of about 16 times the received signal. A frequency dividing unit 19 that divides the clock to generate a predetermined clock.
A data processing unit 20 for restoring the data decoded by the data decoding unit 16 is provided.

FIG. 2 shows the structure of the transmission signal in this embodiment, and 21 is a CRV added to the beginning of the transmission signal.
This is a (code conversion rule violation) signal, and 22 is a transmission information signal indicating the transmission content. FIG. 3 shows a known signal structure C.
The MI code is shown.

The operation of the closed-range digital wired communication system configured as described above will be described with reference to FIGS. 1, 2 and 3. First, a known CM shown in FIG. 3 as a code rule.
It is assumed that the I code is used. The signal “0” is a 34 (01) signal, and the signal “1” is a 33 (00) or 32 (1
Alternately repeating 1). Therefore, 31 (10) is a code rule violation (CRV). The terminal 12 on the transmission side has the coding rule violation signal addition unit 15 of the data coding unit 14.
Then, the code rule violation (CRV) signal 21 of (10) is periodically added to the head of the transmission signal and transmitted to the transmission medium 11. On the other hand, in the terminal 13 that has received the transmission signal, the coding rule violation signal detection unit 17 of the data decoding unit 16 monitors the coding rule violation (CRV) signal 21 at the beginning of the received signal. , The frequency division unit 19 for generating a predetermined clock is reset, and the transmission information signal 22 in the reception signal is normally extracted at the center of the clock in synchronization with the transmission side. The data decoding unit 16 extracts necessary data from the received signal based on this clock,
The data processing unit 20 performs restoration processing. The coding rule violation (CRV) signal 21 is 1 bit.

Table 1 shows a comparison between the characteristics of the closed-range digital cable communication system according to this embodiment and the characteristics of the conventional closed-range digital cable communication system.

[0014]

[Table 1]

As is clear from Table 1, the closed-range digital wired communication system according to this embodiment has excellent effects in terms of simplification of the circuit configuration and improvement of transmission efficiency.
The coding rule is not limited to the above CMI code,
It can also be realized with an AMI code or the like. In addition, code rule violation (CR
The V) signal may be added by a center device connected to the transmission medium 11.

As described above, according to the present embodiment, when the receiving side terminal detects a coding rule violation (CRV) signal added to the beginning of the transmission signal, the frequency division section is reset at that timing, so that the terminals are connected to each other. Synchronization can be easily established. Therefore, the PLL section and VCO section which are conventionally required for clock reproduction can be deleted, and the circuit can be simplified and downsized.

[0017]

As described above, the present invention intentionally adds a code conversion rule violation signal to the beginning of a signal transmitted by a transmitting side terminal or a center device on a transmission medium and transmits the signal, and a receiving side terminal Since the conversion rule violation signal is detected and the sample clock of the received data is generated in synchronization with the timing, a closed-circuit digital wired communication system with a simple circuit configuration, excellent cost efficiency, and high transmission efficiency can be realized.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a closed digital cable communication system according to an embodiment of the present invention.

FIG. 2 is a data configuration diagram of a transmission signal in the embodiment.

FIG. 3 is a waveform diagram of a CMI code in the same embodiment.

FIG. 4 is a schematic block diagram of a conventional closed-range digital wired communication system.

FIG. 5 is a data configuration diagram of a transmission signal in the conventional example.

[Explanation of symbols]

 11 Transmission Medium 12 Terminal (Sending Side) 13 Terminal (Reception Side) 14 Data Encoding Section 15 Coding Rule Violation Signal Adding Section 16 Data Decoding Section 17 Coding Rule Violation Signal Detecting Section 18 Oscillating Section 19 Dividing Section 20 Data Processing Section 21 Code Rule violation (CRV) signal 22 Transmission information signal 31 CV code “0” CRV (10) 32 CMI code “1” signal (11) 33 CMI code “1” signal (00) 34 CMI code "0" signal (01)

Claims (1)

[Claims] 1. A transmission side terminal or a center device has means for intentionally adding a code conversion rule violation signal to the beginning of a signal to be transmitted onto a transmission medium and transmitting the signal, and the reception side terminal has a code conversion rule violation signal. And a closed-range digital wired communication system including means for detecting a signal and generating a sample clock of received data in synchronization with the timing.