METHOD FOR A REDUNDANT TRANSMISSION SYSTEM WITH PRP AND MULTIPLE DATA PACKAGE TRANSMISSION

Description

[0001] The invention relates to a method for operating a transmission system comprising a first network and at least one further network, wherein data is exchanged between these at least two networks by feeding data from the first network to duplicating means, wherein the fed data is wirelessly transmitted via PRP over at least two transmission paths to separating means and is forwarded from the separating means to the connected further network.

[0002] Such well-known transmission systems are used in safety-critical cases in process engineering plants, stationary or mobile work equipment, for example in work vehicles such as cranes or the like.

[0003] It is crucial that data is reliably transmitted from the first network to at least the next network. Such safety-critical data transmission is particularly important when the data is transmitted wirelessly. Improvements have already been made to utilize not just one, but at least two, preferably exactly two, transmission links for this safety application. A further enhancement of this redundant data transmission has been achieved by using the Parallel Redundancy Protocol (PRP) wirelessly, i.e., via radio waves or light. PRP is a Layer 2 redundancy method that is independent of higher layers and is particularly well-suited for real-time Ethernet mechanisms.

[0004] From a security perspective, such a transmission system already functions satisfactorily because redundancy is provided between the two transmission links. For example, if one wireless transmission link is disrupted or fails, at least the second transmission link can be used to ensure data transmission from the first to the second network.

[0005] However, it cannot be ruled out that, despite this redundancy, data transmission between the two networks may be disrupted in an unacceptable manner from a security-critical perspective.

[0006] From DE 198 33 292 A1, a method for contactless data transmission is known, wherein a sending unit transmits information I, which contains the data to be transmitted, to a receiving unit, wherein the information I to be transmitted is sent out by the sending unit several times in the form of information I1 to information In, wherein the information I1 to In to be transmitted is received by the receiving unit and forwarded to a data processing unit, wherein in the data processing unit each received piece of information I is stored and compared with the other received pieces of information I, and wherein if the individual received pieces of information I1 to In match, the transmission of the information I is classified as error-free.

[0007] DE 10 2011 084 344 A1 concerns a method for runtime optimization in packet-oriented mobile communication of data telegrams between rail vehicles and fixed trackside equipment, between rail vehicles and / or between fixed trackside equipment for an ETCS (European Train Control System) from Level 2 upwards, in which the data telegrams are sent multiple times with time delays and / or via several transmission channels whose interference behavior is little or not correlated temporally and / or channel-related, as copies, and duplicates are discarded on the receiving side and the data telegrams are reorganized in the original order.

[0008] US 2010 / 085964 A1 describes a method for transmitting data using data packets and includes splitting a data portion of the data packet into two or more data segments, each containing a corresponding check snippet. The data packet can also be communicated via two or more logical communication channels. The order of the data segments in one communication channel can differ from the order of the data segments in a second communication channel. The respective data segments can be assigned the same or different check snippets.

[0009] The invention is therefore based on the objective of significantly improving a method for operating a transmission system with regard to safety-critical aspects.

[0010] This problem is solved by the features of claim 1.

[0011] According to the invention, the data is transmitted as data packets, and each data packet is transmitted multiple times over the same transmission path. It is assumed that if a single data packet is lost on this transmission path, at least its successor, i.e., the following data packet, is transmitted without error. This transmission method is supported by PRP. Advantageously, it can be accepted that a data packet is lost on a transmission path for whatever reason, and that the data packet subsequently sent is transmitted without error. The invention further incorporates a feedback mechanism that prevents the retransmission of data packets once a data packet has been recognized as having been transmitted without error.

[0012] In a further development of the invention, each data packet is transmitted at least twice over the same transmission path. This assumes that the first data packet sent to the transmission point is lost due to some kind of interference, and that the second data packet, sent immediately afterward, arrives without errors. Alternatively, it is of course conceivable that each data packet is transmitted more than twice over the same transmission path. For example, it is possible for each data packet to be transmitted three, four, or even more times over the same transmission path.

[0013] To achieve a compromise between transmission time and redundancy, it is advantageously designed so that each data packet is transmitted exactly three times over the same transmission path. This allows for the possibility that two of the three identical data packets sent may be lost due to interference on the same transmission path, ensuring that the third data packet arrives. It is assumed that transmitting three identical data packets consecutively over the same transmission path, accepting the loss of two out of three packets, is sufficient. This ensures a sufficiently high level of redundancy while maintaining fast data transmission.

[0014] Regarding the method of transmitting data packets over the same transmission path described above, it is assumed that the same data packet is transmitted at least twice consecutively over the same transmission path. If the first data packet sent over the transmission path arrives without errors, the second data packet can be discarded. The same applies if more than two identical data packets have been sent consecutively over the transmission path. If the first data packet, or the first and at least one subsequent data packet, is lost, the next data packet is used in the further network.

[0015] The same procedure is applied not only via the one transmission path, but also via at least one further transmission path, preferably via both transmission paths, so that only two such transmission paths are present. In such cases, it is possible to send identical data packets sequentially, simultaneously or with a time delay, or in different ways, to the at least two transmission paths, preferably exactly the two transmission paths.

[0016] In a further development of the invention, it is provided that the data are transmitted as data packets and that an error correction value is assigned to each data packet. This means that it is advantageously possible to add redundancy information in the form of an error correction value to the data packets in order to increase redundancy when transmitting the data over the two transmission paths. These error correction values ​​can be assigned only to those data packets that are transmitted over one transmission path or the other. Alternatively, it is conceivable that the error correction values ​​are assigned to the data packets that are transmitted over at least both transmission paths.Alternatively or additionally, it is of course also possible to assign different error correction values ​​to the data packets transmitted over one transmission path than to those transmitted over the first. In addition, a forward error correction procedure is performed using these error correction values. Forward error correction (FEC) provides a way to reduce the error rate during the transmission of data, especially digital data transmitted as data packets, thus offering an error correction method.When forward error correction is used in a transmission system, the sender (doubling device) redundantly encodes the data packets to be transmitted, allowing the receiver (separating device) to detect and correct transmission errors without consulting the sender. The error correction values ​​are thus added to the data packets in the form of additional bits, which are used after transmission over the transmission path to detect errors and, if necessary, to correct them.

[0017] According to the invention, redundancy is significantly increased and safety-critical conditions that could result from faulty data transmission are substantially reduced, both due to the multiple transmission of data packets over the same transmission path and the use of error correction values ​​under safety-critical aspects.

[0018] The method is particularly advantageous with regard to latency (waiting time) during transmission, reliability, and data throughput when transferring data between at least two networks.

[0019] The process can be implemented on a transmission system located in the Figure 1 It is shown that it will be carried out.

[0020] Figure 1 Figure 1 shows a basic arrangement of a transmission system comprising two networks, 2 and 3, which are intended to exchange data with each other. This data exchange can be either unidirectional from network 2 to network 3 (or vice versa), or bidirectional between the two networks, 2 and 3.

[0021] Networks 2 and 3 can be simple or complex networks, for example, in a ring or line topology, or the like. However, it is also conceivable that such a network 2 or 3 comprises only a single element, such as a sensor, an actuator, a control unit, or the like.

[0022] To transmit the data from network 2 to network 3, for example, duplicating devices 4 are provided. These duplicating devices 4 split the incoming data stream into two data streams. Similarly, the two data streams are merged after being received using separating devices 5, and the merged data streams are then forwarded to network 3.

[0023] The data is transmitted wirelessly between the duplicating means and the separating means 5 via two identical or different transmission links 6, 7 using PRP. The wireless transmission is advantageously radio-based, although optical transmission is also conceivable. It is also conceivable that one transmission link 6 is a radio link and the second transmission link 7 is an optical data link. If both transmission links 6, 7 are, for example, radio links, the data, more precisely the data packets, can be transmitted over these two radio links, for example, at the same frequency or at different frequencies and with otherwise identical or different transmission parameters. Identical transmission links 6, 7 are preferable with regard to their construction, whereas different transmission links 6, 7 (e.g., optical / radio or optical) are not.Different transmission parameters) are preferable with regard to increasing redundancy.

[0024] After the data from the primary network 2 has been fed to the duplication devices 4 (also referred to as the redundancy box in PRP), each data packet is transmitted multiple times over the same transmission path 6, 7 and / or an error correction value is assigned to each data packet. The data packets are then transmitted over transmission paths 6, 7 in the same manner, where they are evaluated by the separation devices 5 (also referred to as the redundancy box in PRP), processed if necessary, and fed as data packets to the subsequent network 3.

[0025] The above description of Figure 1refers to a unidirectional data transmission from the first network 2 to the further, in particular the second network 3. For this purpose, the doubling means 4 are designed to split the data stream and the separating means 5 are designed to merge the received data stream.

[0026] If data transmission from network 3 to network 2 is also desired, further doubling devices 4 or separating devices 5 can be present in the transmission path between network 3 and network 2, resulting in a duplicate structure. Alternatively, the devices 4 and 5 can also be configured not only to duplicate the incoming data stream but also to separate the data streams supplied via transmission paths 6 and 7, which also applies to the separating devices 5. Reference symbol list

[0027] 1. Transmission system 2. First network 3. Second network 4. Duplicator 5. Separator 6. First transmission path 7. Second transmission path

Claims

1. Method for operating a transmission system (1) comprising a first Ethernet network (2) and at least one further Ethernet network (3), wherein data are interchanged between these at least two networks (2, 3) by virtue of data of the first network (2) being supplied to duplicating means (4), wherein the supplied data are wirelessly transmitted to separating means (5) via at least two transmission links (6, 7) by means of the parallel redundancy protocol, PRP, and forwarded to the connected further network (3) by the separating means (5), wherein the data are transmitted as data packets and each data packet is transmitted repeatedly via the same transmission link (6, 7), wherein provision is made of error detection and a feedback mechanism, which prevents data packets from being resent if a data packet has been recognized as having being transmitted without errors.

2. Method according to Claim 1, characterized in that each data packet is transmitted at least twice via the same transmission link (6, 7).

3. Method according to Claim 1, characterized in that each data packet is transmitted three times via the same transmission link (6, 7).

4. Method according to any of the preceding claims, characterized in that each data packet is assigned an error correction value, and wherein a forward error correction method is carried out with the aid of the error correction values.