Patent ID: 8601165

Claim:
A method for synchronization in a network having a plurality of nodes, the plurality of nodes comprising higher-level nodes and lower-level nodes and the plurality of nodes including a first lower-level node, the method comprising: the first node regularly receiving time messages transmitted from one or more higher-level nodes of the plurality of nodes, including receiving a time message from a higher-level node, wherein the time message comprises a local time of the higher-level node, and wherein a minimum delay time is defined for time messages between higher-level nodes and lower-level nodes; the first lower-level node evaluating the time message received from the higher-level node, wherein said evaluating comprises: on reception of the time message, reading the local time of the higher-level node, and adding the defined minimum delay time to the local time of the higher-level node, thereby generating a comparison time; comparing the comparison time with the first lower-level node's local time; if the comparison time is newer than the first lower-level node's local time, updating the first lower-level node's local time in accordance with the comparison time and if the comparison time is older than the first lower-level node's local time, the first lower-level node's local time is not updated; monitoring the time since the last update of the local time of the first lower-level node; comparing the time since the last update of the local time of the first lower-level node with a time interval, which can be predetermined; if the time since the last update of the local time of the first lower-level node exceeds the time interval, producing a virtual local time at the first lower-level node wherein the virtual local time lags behind the actual local time at the first lower-level node; if the comparison time is newer than the virtual local time which has been produced at the first lower-level node; updating the first lower-level node's local time in accordance with the comparison time.