| 摘要 |
The invention refers to a method for clock synchronization in a communication network comprising a plurality of nodes (MA, SL1, SL2), wherein the nodes (MA, SL1, SL2) comprise a master node (MA) and slave nodes (SL1, SL2), wherein the master node (MA) has a master clock generating master counter values and wherein each slave node (SL1, SL2) has a slave clock generating slave counter values, the clock synchronization being performed in successive synchronization cycles. In one synchronization cycle, synchronization messages (SY(k)) are transmitted in a sequence of synchronization messages (SY(k)) from the master node (MA) to a slave node (SL1) and from one slave node (SL1) to another slave node (SL2), wherein a synchronization message (SY(k)) sent from one node (MA, SL1, SL2) to another node (MA, SL1, SL2) includes information based on one or more measured counter values (TS(M(k)), TS(S 1 in (k)), TS(S 1 out (k))) of the node (MA, SL1, SL2) sending the synchronization message (SY(k)). For each slave node (SL1, SL2) the master counter value (x 1 in (k), x 2 in (k)) for a measured slave counter value (TS(S 1 in (k)), TS(S 2 in (k)) is estimated by using an estimation method applied to a probabilistic model for state variables of the nodes (MA, SL1, SL2), wherein each slave clock is synchronized based on the estimated master counter value (x1 in (k), x 2 in (k)). Preferably, the well-known Kalman filter or a sum-product algorithm is used as the estimation method applied to the probabilistic model. The method of the invention is preferably performed in communication networks in the industrial automation domain. It enables very good clock synchronization with higher precision than standard synchronization methods.
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