System and method for packet transmission in a communications network
A communications network comprises a plurality of participants. A first participant transmits a message repeating sequence of N≥2 successive messages to a second participant. An action which can be performed by the second participant is assigned to each message in the sequence. The first participant begins to transmit one of the N messages at N successive transmission times T_I (I=O, . . . , N−1). Each of the N messages contains a field defining a waiting time. The second participant selects one message from among the messages in the sequence which are successfully received by the second participant as a useful message, measures a time elapsed since reception of the useful message, and performs the action assigned to the useful message when the elapsed time has reached the assigned waiting time.
1. A method for operating a communications network, wherein:
the communications network comprises a plurality of participants including a first participant and a second participant,
wherein the first participant transmits a message repeating sequence consisting of N successive messages to the second participant, where N≥2, wherein a respective action which can be performed by the second participant is assigned to each message in the message repeating sequence,
wherein the first participant respectively begins to transmit one of the N messages at N successive transmission times T_I (I=0, . . . , N−1), wherein each of the N messages contains a field which defines a waiting time assigned to a respective message of the N messages:
W_I=T _( N− 1)− T_I+ΔW_I ( I= 0 , . . . ,N− 1),
where ΔW_I is a non-negative tolerance time, and wherein the second participant selects one message from among the N messages in the message repeating sequence which are successfully received by the second participant as a useful message and measures a time elapsed since the reception of the useful message and performs the action assigned to the useful message when the elapsed time has reached the waiting time assigned to the useful message.
2. The method according to claim 1 , wherein the second participant selects the message received earliest by the second participant from among the successfully received messages in the message repeating sequence as the useful message.
3. The method according to claim 1 , wherein the action respectively assigned to the messages in the message repeating sequence respectively comprises generating an interrupt.
4. The method according to claim 1 , wherein the same action is assigned to each message in the message repeating sequence.
5. The method according to claim 1 , wherein, upon successful reception of a further message in the message repeating sequence, the second participant does not perform the action assigned to the further message.
6. The method according to claim 1 , wherein the second participant forwards each message in the message repeating sequence which is received by the second participant to a further participant of the communications network or returns said message to the first participant without waiting for the expiry of the waiting time stated in the message.
7. The method according to claim 1 , wherein the second participant writes useful data into a useful data field of the received message and forwards the message processed in this manner to a further participant of the communications network or returns said message to the first participant without waiting for the expiry of the waiting time stated in the message.
8. The method according to claim 1 , wherein the messages in the message repeating sequence each contain the same useful data and/or the same status data.
9. The method according to claim 1 , wherein the messages in the message repeating sequence are processed by the participants in passing.
10. The method according to claim 1 , wherein, at a time T_N which is later than T_(N−1), the first participant transmits a further message which does not belong to said message repeating sequence, and wherein the tolerance times ΔW_I are each shorter than T_N−T_(N−1) (I=0, . . . , N−1).
11. A communications network having a first participant and a second participant, wherein:
the first participant is set up to transmit a message repeating sequence consisting of N messages, where N≥2, wherein a respective action which can be performed by the second participant is assigned to each message in the message repeating sequence,
wherein the first participant respectively begins to transmit one of the N messages at N successive transmission times T_I (I=0, . . . , N−1), wherein each of the N messages contains a field which defines a waiting time assigned to a respective message of the N messages:
W_I=T _( N− 1)− T_I+ΔW_I ( I= 0, . . . , N− 1),
where ΔW_I is a non-negative tolerance time, and wherein the second participant is set up to select one message from among the N messages in the message repeating sequence which are successfully received by the second participant as a useful message and
to measure a time elapsed since the reception of the useful message and to perform the action assigned to the useful message when the elapsed time has reached the waiting time assigned to the useful message.
12. The communications network according to claim 11 , wherein the communications system is an Ethernet network.
13. A participant in a communications network, wherein:
the participant is set up to receive a message repeating sequence consisting of N messages,
where N≥2,
wherein the N messages are transmitted at N successive transmission times T_I (I=0, . . . , N−1),
wherein each of the N messages contains a field which defines a waiting time assigned to a respective message of the N messages:
W_I=T ( N− 1)− T_I+ΔW_I ( I= 0 , . . . ,N− 1),
where ΔW_I is a non-negative tolerance time,
to select a message in the message repeating sequence which is successfully received by said participant as a useful message, and
to measure a time elapsed since the reception of the useful message and to perform an action assigned to the useful message when the elapsed time reaches a waiting time assigned to the useful message.
14. The participant according to claim 13 , wherein the participant has a memory and is set up to store a copy of the selected message in the memory at least until the waiting time expires.
15. The participant according to claim 13 , wherein the participant has a clocked counter, to which a final value is assigned, and wherein the participant is set up, in response to the successful reception of a message, provided that the counter is then at its final value:
to select the message as the useful message;
to determine a starting value corresponding to the waiting time defined by the useful message, to set the counter to the starting value, to start the counter and to stop the counter when the final value is reached; and
to perform the action assigned to the message only when the down-counter has reached the final value.
16. The participant according to claim 15 , wherein the tolerance times ΔW_I (I=0, . . . , N−1) are each greater than zero.