JPS63193635A - Loop transmission system - Google Patents

Abstract

PURPOSE:To allow remote stations to execute packet exchange through a loop transmission system asynchronously with a center station and to prevent the titled system from generating communication stop by transmitting a receiving signal from a transmission line to a packet exchanging part as it is at the time of asynchronizing a frame. CONSTITUTION:When a frame synchronizing clock from the center station 1 is asynchronous, respective remote stations 2-5 can not obtain the synchronism of line exchanging slots at a TDMA part 23. In this case, the frame asynchronism is detected by a detection control part 26, a multiplexer 27 is controlled and receiving data in a receiving part 21 is directly transmitted to a packet exchanging part 24. The exchanging part 24 extracts a packet exchanging data area from the receiving signal based on a switching signal between packet exchange and line exchange to execute interface with a packet exchanging terminal equipment.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a loop transmission method in a loop transmission system used for local communication.

BACKGROUND OF THE INVENTION FIG. 3 shows a configuration example of a loop transmission system to which a conventional loop transmission method is applied. In FIG. 3, 6 is a master station that generates a synchronized clock for frames that circulate on the transmission path 10 at a fixed time, and 7 is a master station that generates a synchronized clock for frames that circulate on the transmission path 10 in a fixed period of time. This is a sub-master station that generates a frame synchronization clock on behalf of station 6. 3 to 5 are remote stations,
A terminal device that performs packet switching or a terminal device that performs line switching is connected to these remote stations to perform data transmission by packet switching or line switching.

Frame transmission and reception at the remote station (d), carried out in synchronization with the synchronized clock generated at the master station 6 or submaster station 7.The data is
At the remote station, the information is stored in fixed-length slots within the frame circulating on the transmission path, and after writing various information to the frame header,
It is sent out on the transmission line together with the switching signal between packet switching and circuit switching, and is received by the destination remote station.

FIG. 4 shows a configuration diagram of a conventional remote station.

In FIG. 4, reference numeral 21 is a receiving section that takes in the signal on the transmission path 10, and 22 is a transmitting section that sends out the signal onto the transmission path 11. 23 distributes the signal on the transmission path received by the receiving section to a slot for packet switching and a slot for line switching, and sends each signal to the packet switching section 24 or the line switching section 2.
This is a TDMA section that combines signals from the packet switching section 24 and line switching section 25 as a series of slots and sends them to the transmitting section 22 together with these switching signals. The packet exchange unit 24 performs an interface with a terminal device for packet exchange. The line switching section 26 performs an interface with a terminal device for line switching.

Problems to be Solved by the Invention In the conventional loop transmission system configured as described above, when the frame synchronization clock generated at the master station 6 in FIG. A frame synchronization clock is generated, but if synchronization occurs in this case as well, the cyclic frames will not be synchronized at each remote station, making it impossible to perform not only circuit switching but also packet switching. All communications in the transmission system stop.

An object of the present invention is to provide a loop transmission method that can prevent a complete communication stoppage in the above-mentioned transmission system.

Means for solving the problem 6. A common transmission path configured in a loop includes a center station that manages and controls frames that circulate on the transmission path at regular intervals, and a terminal device that performs packet switching or circuit switching. A loop transmission system is formed by connecting multiple remote stations and transmitting data.
When a frame consisting of a frame header and a plurality of fixed-length slots circulates through the loop-shaped transmission path together with switching control signals for packet switching and circuit switching, and transmits data, the remote station transmits data to the center station. It is equipped with both synchronization means that transmits and receives cyclic frames in synchronization with A loop transmission method, characterized in that data is transmitted using a synchronization means, and when a cyclic frame becomes out of synchronization, switching to the asynchronous means prevents a complete stoppage of communication in the loop transmission system. .

6.7 Effects According to the present invention, with the above-described configuration, when each remote station existing on the loop transmission system detects out-of-synchronization of the cyclic frame, it is controlled to perform packet exchange asynchronously with the center station. and prevent a complete communication outage in the loop transmission system.

Embodiment An embodiment of the present invention will be explained with reference to FIGS. 1 and 2. FIG. 1 shows a loop transmission system to which the present invention is applied. In FIG. 1, reference numeral 1 denotes a center station that manages and controls frames circulating on a transmission path at a constant cycle by generating a synchronized clock. 2 to 5 are remote stations for transmitting and receiving data arranged on the loop-shaped transmission line 10. A packet switching terminal device and a circuit switching terminal device are connected to each remote station, and packet switching and circuit switching are performed via these remote stations. At the remote station, data is stored in slots divided into fixed lengths within frames circulating on the transmission path, and after various information is written in the frame header, data is transferred via packet exchange and circuit exchange. The signal is sent out onto the transmission path along with a switching signal, and is taken in by the destination remote station.

A configuration diagram of the remote station is shown in Figure 2.

In FIG. 2, numeral 21 is a receiving section that receives signals on the transmission path 10, and 22 is a transmitting section that sends out signals onto the transmission path 11. 23 distributes the signal on the transmission path taken in by the receiving section to the slot for packet switching and the slot for line switching, and sends each signal to the packet switching section 24 or the line switching section 2.
This is a TDMA section that combines the signals from the packet switching section 24 and the line switching section 26 as a series of slots, and outputs them together with the switching signals. The packet exchange unit 24 performs an interface with a terminal device for packet exchange. The line switching section 26 performs an interface with a terminal device for line switching.

26 is an out-of-synchronization detection controller that detects out-of-frame synchronization of the signal received by the receiving section 21 and sends a control signal to the multiplexer 27. The multiplexer 27 is controlled by the out-of-synchronization detection controller 26 and switches the signal to be input to the packet switching unit 24.

The operation of this embodiment configured as above will be described below. In FIG. 1, it is assumed that the frame synchronization clock generated by the center station 10 becomes out of synchronization. In this case, in each remote station configured as shown in FIG. 2, all 23 TDMADMA line switching slots cannot be synchronized, and line switching on the loop transmission system becomes impossible. However, this out-of-frame synchronization is detected by the out-of-synchronization detection controller 26 shown in FIG.
The multiplexer 27 is controlled so that all DMAs 23 are connected directly to the receiving section 21. That is, when frame synchronization occurs, control is performed so that the signals received by the receiving section 21 of each remote station are transmitted as they are to the packet switching section 24.

At this time, the packet exchange section 24 performs packet exchange 9.

Based on the line switching switching signal and the line switching switching signal, a data area for packet switching is extracted from the received signal, and an interface with a terminal device for packet switching is performed.

In addition, the output signal from the packet switching terminal device is TD
The signal is sent to the transmitter 22 along with a switching signal between packet switching and circuit switching carried out by the MADMA 23, and is sent out onto the transmission line 11. Note that during normal operation, frames are transmitted and received in synchronization with the center station without bypassing the TDMA section.

As described above, according to this embodiment, a frame out-of-synchronization detection controller is provided, and when out-of-synchronization, the signal received from the transmission path is transmitted to the -1:''!!bucket exchange section without going through the TDMA section. , it is possible to exchange packets in the loop transmission system asynchronously with the center station, and prevent a complete stoppage of communication in the transmission system.

As described in detail, according to the present invention, even if frame synchronization occurs due to failure of the center station, communication between packet switching terminal devices existing in the loop transmission system is possible. This has a great practical effect, since the worst-case scenario of a complete stoppage of communication can be avoided.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a loop transmission system according to an embodiment of the present invention, Figure 2 is a configuration diagram of a remote station in the same system, Figure 3 is a configuration diagram of a conventional loop transmission system, and Figure 4 is a configuration diagram of a conventional loop transmission system. FIG. 2 is a configuration diagram of an example remote station. 1...Mountain/Central Station, 2-5...
Remote station, 6...Master station, 7...Submaster station, 1
0 to 11...Transmission path, 21...Receiving section, 22...Transmitting section, 23...TDMA section, 24...Packet exchange section, 26... line switching section, 26... out-of-synchronization detection controller, 27... multiplexer.

Claims (1)

[Claims] A common transmission path configured in a loop includes a center station that manages and controls frames circulating on the transmission path at regular intervals, and multiple remote stations that perform data transmission by connecting terminal devices that perform packet switching or circuit switching. and form a loop transmission system as components,
When a frame consisting of a frame header and a plurality of fixed-length slots circulates through the loop-shaped transmission path together with switching control signals for packet switching and circuit switching, and transmits data, the remote station transmits data to the center station. It is equipped with both a synchronization means for transmitting and receiving a cyclic frame in synchronization with the center station, and an asynchronous means for controlling to perform only packet exchange without synchronizing with the center station when it detects that the cyclic frame is out of synchronization. A loop transmission characterized in that data transmission is performed using the synchronization means, and when synchronization of cyclic frames occurs, switching to the asynchronous means prevents a complete stoppage of communication in the loop transmission system. system.