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OWD is becoming increasingly important nowadays, as SLA agreements use it as a parameter to ensure QoS levels. However, its measurement is still a much debated topic due to the difficulty in the clock synchronization process. The paper approaches a new methodology to measure OWD, using NTP protocol with virtual clocks and bigger packets. This approach works over a measurement tool developed by the...
Using the Precision Time Protocol (PTP) specified by the IEEE 1588 standard, synchronization of distributed clocks is achieved by propagating the timing information of a preselected master clock throughout the entire network. Based on this directly or indirectly obtained noisy timing information, each slave clock tries to follow as closely as possible the master time. This paper formulates the PTP...
Time synchronization is an essential problem for wireless sensor networks (WSNs). There have been many research works about time synchronization in WSNs in the literature. Most of them only correct the clock offset, i.e., adjust two clocks to the same time. However, as the clock drift is not compensated, two clocks run at different rates, and will be different again after a while. In this paper, an...
With the increasing use of Ethernet for real-time control of distributed dynamic systems, and inexpensive processing power at the sensor and actuator nodes, there is a growing interest in the process control community to move towards “model based” distributed control. Prior work shows that the lack of precise time synchronization is a critical hindrance to reliable model generation or estimation in...
IEEE 1588 is a standard to synchronize independent clocks running on separate nodes of a distributed measurement and control system. In PTN (Packet Transport Network), it is considered as a key technology for supporting legacy TDM services and synchronizing 3G base stations. However, conventional IEEE 1588 synchronization algorithm assumes symmetrical links, and makes errors for asymmetric links for...
This paper presents a novel clock synchronization algorithm based on the transparent clock mechanism of peer-to-peer precision time protocol. To model the dynamics of the oscillator and the influence of the uncertainties, e.g., random stamping and quantization errors, on the synchronization performance, clock synchronization is formulated as a probabilistic inference problem which can be solved by...
Traditional time synchronization algorithm focuses on improving the synchronization mechanism to improve the synchronization accuracy. With development of time synchronization, more and more focuses on how to process the synchronization information to improve the synchronization accuracy. Maximum likelihood estimation method is one of the mathematical statistics theories commonly used in parameter...
Precision Time Protocol (PTP) synchronizes clocks of networked elements by exchanging messages containing precise time-stamps. A master clock is carefully chosen to provide the reference clock to the rest elements in the network, called slaves. Using the time-stamps, slave element learns the relation between its own clock and the master clock so that it can synchronize its time to the reference time...
It is often required to analyze the behavior and reliability of large distributed systems before deploying them. This task relies on the existence of a dependency graph. The dependency graph can be constructed according to the blueprint of the system (if available) or by measuring runtime messages. To construct such a graph by measuring the runtime messages, the clocks on different nodes must be weakly...
Providing a powerful synchronization system is one of the most important goals to be pursued if an efficient utilization of sensor networks has to be addressed. The basic concept behind a Wireless Sensor Network is to deploy a large number of sensor nodes able to acquire and process data. Most of WSNs applications require sensor nodes to maintain local clocks both to determine the events order and...
This paper presents GConf, a peer-to-peer Gossip-based delay sensitive N-to-N information dissemination protocol, intended for applications such as real-time multiparty conferencing. Through 3-way gossip-based exchanges with randomly selected peers, information frames can be spread throughout the whole community within a delay of 1.5 round-trip-times. The non-delivery probability can be improved exponentially...
This paper introduces a methodology for using self- timed logic in FPGA-based embedded systems starting from a high-level specification of data-flow networks. It uses CodeS- imulink as an environment for code generation. The asynchronous circuits are synthesized using conventional commercial tools and we propose solutions for the issues raised. Also we describe a simple way of simulating these designs.
A conflict of multiplicity k occurs when k stations transmit simultaneously to a multiple access channel. As a result, all stations receive feedback indicating whether k is 0, 1, or is ≥ 2. If k = 1 the transmission succeeds, whereas if k ≥ 2 all the transmissions fail. In general, no a priori information about k is available. We present and analyze an algorithm that enables the conflicting stations...
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