Joergen Mad

Bio: Joergen Mad is an academic researcher. The author has contributed to research in topics: Synchronization & White noise. The author has an hindex of 1, co-authored 1 publications receiving 4 citations.

An Oscillator Model for High-Precision Synchronization Protocol Discrete Event Simulation

Abstract: : It is well known that a common notion of time in distributed systems can be used to ensure additional properties such as real-time behavior or the identification of the order of events As large-scale hardware testbeds for such systems are neither efficient nor easy to manage, discrete event simulations (DES) can be used to model such networks However, to ensure an exact behavior of such simulations, high precise models of the local clocks are also needed: the driving oscillators have to be modeled in a way that a DES simulation of a free-running node clock shows the same Allan deviation as the simulated counterpart This paper shows an approach to find a corresponding model for a simulator using white noise and a filter with the same power density spectrum as real-world oscillators

Master failures in the Precision Time Protocol

Abstract: If all clocks within a distributed system share the same notion of time, the application domain can gain several advantages. Among those is the possibility to implement real-time behavior, accurate time stamping, and event detection. However, with the wide spread application of clock synchronization another topic has to be taken into consideration: the fault tolerance. The well known clock synchronization protocol IEEE1588 (precision time protocol, PTP), is based on a master/slave principle, which has one severe disadvantage. This disadvantage is the fact that the failure of a master automatically requires the re-election of a new master. The start of a master election based on timeout and thus takes a certain time span during which the clocks are not synchronized and thus running freely. Moreover the usage of a new master also requires new delay measurements, which prolong the time of uncertainty as well. This paper analyzes the results of such a master failure and proposes democratic master groups instead of hot-stand-by masters to overcome this problem by. It is shown by means of simulation that the proposed solution will not deteriorate the accuracy of the slave clocks in case of a master failure.

Achieving a Realistic Notion of Time in Discrete Event Simulation

Abstract: Distributed sensor systems require clock synchronization between all sensor nodes to provide consistent view of the overall system. Owing the growing size of networks, the evaluation of the synchronization performance becomes difficult, if done by means of experiments. Simulation is another method to tackle this issue. Realistic simulation of synchronization schemes requires accurate modelling of oscillators which are the driving timers generating various events. One way to characterise oscillators is to utilize the Allan variance, which can be used to generate a phenomenological model based on power spectral density. Since discrete event simulation (DES) tools are widely used to model network protocols, models which combine accuracy and performance are needed. This paper presents a model that was optimised for use in DES. To verify that the simulation results sufficiently match measurements, an implementation in OMNeT

A novel, high resolution oscillator model for DES systems

Abstract: High accurate synchronization of clocks in environments with a high number of nodes can take advantage of modern communication networks. However, with the large number of nodes another problem arises: systems of this size cannot any more be evaluated on experimental basis. Therefore, simulation tools and models are required. These simulator models have special requirements which are outlined in this paper. Moreover, a modeling strategy is proposed and demonstrated, which can be implemented for Discrete Event Simulation tools.

Out-Degree Based Clock Synchronization In Wireless Networks Using Precision Time Protocol

Abstract: In this paper, an extension of Precision Time Protocol (PTP) to enable energy-efficient clock synchronization between the nodes within Wireless Sensor Network (WSN) is proposed. PTP is nanosecond accuracy clock synchronization protocol in which nodes are organized in master-slave hierarchy on the basis of clock accuracy by means of Best Master Clock (BMC) algorithm. The algorithm considers clock accuracy to select best clock in the system. A novel modification of IEEE 1588 BMC algorithm for energy-constraint multi-hop WSN has been proposed to reduce clock convergence time and energy needed by considering out-degree of clocks without sacrificing synchronization accuracy. The new algorithm results in energy efficient clock synchronization that makes it most appropriate for low-power multi-hop wireless sensor networks. We present NS-3 simulation data that confirms the effectiveness of work.