Method of operating a redundant PRP

Abstract

The invention relates to a method for operating a transmission system (1) that comprises a first network (2) and at least one additional network (3), in which data are exchanged between said at least two networks (2, 3) by means of data of the first network (2) being fed to duplication means (4) in the form of data packets, these fed data packets being wirelessly transmitted to separator means (5) via at least two transmission paths (6, 7) using PRP, and being forwarded from said separator means (5) to the connected additional network (3) in the form of a data stream. The invention is characterized in that the data packets are temporarily stored in a memory once they have been transmitted via the at least two transmission paths (6, 7).

Claims

1. A method of operating a transmission system having a first network and one other network with exchange of the data packets between the networks, the method including the steps of: feeding the data packets from the first network to a doubler; splitting the data packets with the doubler into two separate data streams of the data packets; transmitting each of the two data streams separately from each other wirelessly by PRP via two respective wireless transmission paths to the second network; receiving and buffering the two separate data streams in a memory at the second network; and if one data packet on one transmission path did not arrive in correct sequence, buffering the two separate data streams in the memory at the second network and delaying transmission to the second network, deleting the one data packet that was transmitted in the incorrect sequence and replacing the one data packet that deleted in the data stream to be forwarded at a correct position by the corresponding data packet that was transmitted on the other transmission path and buffered, ending the buffering, and transmitting the corrected sequence after a timeout or after the sequence of the data stream is corrected.

2. The method defined in claim 1, wherein the buffering is performed according to a predetermined criterion.

3. The method defined in claim 2, further comprising the step, once the predefined criterion is reached, of deleting the buffered data packets.

4. The method defined in claim 2 further comprising the step, once the predetermined criterion is reached, of: forwarding the buffered data packets.

5. The method defined in claim 2, wherein the predetermined criterion is a period of time.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The proposed method can be carried out on a transmission system that is illustrated in the attached drawing in which;

(2) FIG. 1 is a simplified schematic view of this invention; and

(3) FIG. 2 is a schematic diagram illustrating the prior art.

SPECIFIC DESCRIPTION OF THE INVENTION

(4) FIG. 1 shows a basic layout of a transmission system having two networks 2 and 3 that exchange data between each other. This data exchange can take place either unidirectionally from the network 2 to the network 3 (or vice versa) or also bidirectionally between the two networks 2 and 3.

(5) The networks 2 and 3 can be simple or complex networks, for example with a ring or linear topology or the like. It is also conceivable, however, for such a network 2 and 3 to comprise only one single element such as a sensor, an actuator, a control device, or the like.

(6) In order to transmit the data from the network 2 to the network 3, for example, a doubler 4 is provided. This doubler 4 splits the data stream that is fed in into two data streams. After they are received, the two data streams are likewise merged by a splitter 5, with the received data streams being forwarded to the network 3 after having been merged.

(7) The transmission of the data between the doubler 4 and the splitter 5 takes place wirelessly by PRP via two similar or different transmission paths 6 and 7. The wireless transmission advantageously occurs via radio, although optical transmission is also conceivable. It is also conceivable for one transmission path 6 to be a r-f path and for the second transmission path 7 to be an optical data transmission path. If both transmission paths 6 and 7 are radio transmission paths, for example, the data, more precisely the data packets, can be transmitted over these two radio transmission paths at the same frequency or at different frequencies, for example, and otherwise with the same parameters or with different transmission parameters. Similar transmission paths 6 and 7 are to be preferred in terms of their construction, although transmission paths 6 and 7 that differ from one another (for example optical/radio or with different transmission parameters) are to be preferred in terms of the increased redundancy that provides.

(8) After the data have been fed from the first network 2 to the doubler (in PRP, also referred to as a redundancy box), each data packet is caused to be transmitted multiple times via the same transmission path 6 and 7 and/or an error correction value is assigned to each data packet. The transmission of the data packets via the transmission paths 6 and 7 then takes place analogously, with these being appropriately evaluated, optionally processed, by the splitter 5 (in PRP, also referred to as a redundancy box) and fed to the other network 3 as data packets.

(9) The foregoing description of FIG. 1 relates to a unidirectional data transmission from the first network 2 to the additional, particularly the second network 3. For this purpose, the doubler 4 is designed to split the data stream, whereas the splitter 5 is designed to merge the received data stream.

(10) If data transmission from the network 3 to the network 2 is also desired, additional doubler 4 and splitter 5 can be present in the transmission path between the network 3 and the network 2, thus resulting in a double construction. Alternatively, the splitting/doubling devices 4 and 5 can also be designed to not only double the supplied data stream, but also to separate the data streams fed in via the transmission paths 6 and 7, which also applied to the splitter 5.

(11) FIG. 2 shows the known, disadvantageous method of the sake of example in a case in which at least one data packet (here, the data packets three, four, and five) have been transmitted with delay on one transmission path 6 (top left in FIG. 2, data stream consisting of five data packets).

(12) On the other transmission path 7 (bottom left in FIG. 2, the data stream consisting of five data packets), one data packet (data packet three) has been lost during transmission.

(13) If these two (faulty) data streams are put back together by the splitter 5, this results in the faulty data stream shown in FIG. 2, with the data packets in the incorrect sequence one, two, four, three, five.

(14) This faulty data stream does not occur when the method according to the invention is used; rather, by virtue of the buffering and removal of the stored data packets from the buffer memory, the data packets are advantageously put into the correct sequence.