›› MIND Lab Seminar Series: 08 October 2007

Cyclone Time Technology: Deriving Common Time Using Location Information

Dr. Ashok Agrawala
Professor of Computer Science, University of Maryland at College Park

›› Logistics

Date: Monday, 08 October 2007

Time: 2:00p to 3:00p

Location: AVW 3258

›› Abstract

The IEEE 1588 standard defines a protocol for clock synchronization in measurement and control systems communicating by local area networks including but not limited to Ethernet. The protocol enables heterogeneous systems that include clocks of various inherent precision, resolution and stability to synchronize. The IEEE 1588 protocol takes a master-slave approach for clock synchronization where each slave synchronizes its clock with its master. In this paper, we take an alternative approach to clock synchronization where all nodes can share a notion of common clock in a distributed scheme, and where all nodes are considered peers.

The proposed scheme works by first assuming a local clock model at each node that takes the clock offset and drift rate into account. Timestamps are exchanged between neighboring nodes which permit each node to derive a common time base using only its local information. The mathematical basis of the approach comes from linear algebra, in which the principal eigenvector of a stochastic matrix can be calculated by repeated multiplications of matrices, and is a method which has been used in consensus algorithms.

Our initial results show that we can achieve a stable and high degree of clock synchronization. The degree of synchronization achieved is affected by the perturbations in both (i) the transit time and (ii) the clock drift rate, but does not depend on the clock drift rate. We believe that the proposed technique offers several advantages over the current master-slave based technique by avoiding a single point of failure and achieving accuracy that does not depend on the actual local clock drift rates. Further, the use of only local information makes the scheme highly scalable.