Zarlink Semiconductor Limited

Petrus W Simons

Robertus Laurentius Van Der Valk

Willem L Repko

Craig Barrack

Steven Roos

A method of recovering timing information in a packet network is disclosed wherein a modulation scheme is used to transport additional information required for clock recovery between the sender and receiver across the network.

Method to improve the resolution of time measurements and alignment in packet networks by time modulation

Disclosed is a method of aligning clocks over multiple networks having different clock domains. The method comprises transmitting timestamped packets over said networks between source and destination nodes, said timestamped packets conveying timing information based on a source clock at said source node, determining the expected delay over multiple nodes for a given traffic density, identifying at least one intermediate node between said source and destination node where said determined expected delay is such as to permit clock restoration within predefined acceptable parameters, restoring said source clock at said at least one intermediate restoration node to generate a restored intermediate clock signal, producing from said restored intermediate clock signal new timestamped packets conveying timing information based on said restored intermediate clock signal, and forwarding said new timestamped packets to said destination node.

Alignment of clocks over multiple packet networks

Disclosed is a method and apparatus for aligning clock domains over an asynchronous network between a source controlled by a first clock and a destination controlled by a second clock. The predicted delay is estimated for transmitting packets between a source and destination over the network. The time-stamped synchronization packets are sent to the destination, each time-stamped synchronization packet carries timing information based on a master clock at the source. A set of synchronization packets are received at the destination to create a set of data points, and the set of data points is weighted so that synchronization packets exhibiting a delay further from the expected delay are accorded less weight than synchronization packets exhibiting a delay closer to the expected delay. The expected delay is updated to create a current delay estimate based on the set of data points taking into account the different weighting of the data points. These steps are continually repeated on new sets of data points created from newly received synchronization packets using the current delay estimate for the expected delay. And a clock domain at the destination is continually aligned with a clock domain at the source based on the current delay estimate for packets traversing the network between the source and destination.

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Nieuwerkerk a/d IJssel, Netherlands

Petrus W Simons