Showing papers on "Precision Time Protocol published in 2008"

An Enhanced IEEE 1588 Time Synchronization Algorithm for Asymmetric Communication Link using Block Burst Transmission

Abstract: IEEE 1588 is a standard to synchronize independent clocks running on separate nodes of a distributed measurement and control system. In IP based cellular network, it is considered as a key technology to synchronize base stations. Especially, interests for the low-cost and very-small home cellular base station called the Femtocell is increasing, and it is connected to the cellular core network using an asymmetric communication link such as xDSL. However, the conventional IEEE 1588 synchronization algorithm assumes symmetrical links, and makes errors for asymmetric links for the calculation of the time difference between the master clock (a clock source) and the slave clock (a clock consumer). We propose an enhanced synchronization algorithm to calculate the asymmetric ratio of the communication link, and the proposed algorithm enhances an accuracy of the time synchronization.

Implementation of a precision time protocol over low rate wireless personal area networks

Abstract: Time synchronization is essential for a number of network applications. As the era of ubiquitous computing is ushered in, high precision time synchronization of nodes in wireless networks is required. High precision time synchronization can enable a variety of extensions of applications. This paper includes the design and implementation of the precision time protocol over low rate wireless personal area networks (LR-WPANpsilas). To achieve high precision in LR-WPANpsilas, we analyze the factors of latency and jitter in wireless environments, and we aim to minimize these factors. In addition, this paper presents experiments and the performance evaluation of the precision time protocol in LR-WPANpsilas. The result is that we established for nodes in a network to maintain their clocks to within a 50 nanosecond offset from the reference clock.

IEEE 1588 syntonization and synchronization functions completely realized in hardware

Abstract: The Precision Time Protocol (PTP) is an application layer protocol and therefore destined to be implemented in software. Hardware functions, if present, include a high resolution clock that helps to generate precise timestamps for PTP messages. The presented paper describes an IEEE 1588 clock that realizes syntonization and synchronization functions completely in hardware. It combines a three-port bridge with peer-to-peer Transparent Clock (TC) functionality and an Ordinary Clock (OC), together with other protocol and application specific logic within an FPGA. The aim of such an implementation is to provide a high accuracy and robust system clock that can be driven by a simple crystal oscillator. It can cope with oscillator instabilities caused by environmental effects such as fast temperature changes or accelerations (shock/vibration). It may deliver synchronicity in deeply cascaded topologies.

An experimental investigation of VoIP and video streaming over fixed WiMAX

Abstract: Despite the significant interest in WiMAX technology and deployment, there are very few publicly reported measurements from testbeds and field trials. As such, most WiMAX studies employ simulation and modeling. This paper contributes to our understanding of what is realistically possible using off-the-shelf fixed WiMAX equipment today. We employ multiple competing traffic sources over a point-to-multipoint WiMAX topology and measure the capacity of the WiMAX equipment to handle a multitude of VoIP flows between subscriber stations while delivering a variable number of video streams. We measure throughput, packet loss, and one-way delay for both line-of-sight (LOS) and non-line-of-sight (NLOS) conditions. For the one-way delay measurements we synchronize the clocks of all testbed hosts with a software-only, open source implementation of the IEEE 1588 Precision Time Protocol. We compare these one-way delay measurements with those obtained when GPS-based synchronization is used.

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.

System and method for providing quality inter-domain network time transport

Abstract: A method is provided in one example embodiment and includes providing a time protocol assistant associated with a time-synchronized domain (TSD). The TSD includes a set of nodes that are synchronized to a same time source. The TSD has defined egress and ingress edge points where bidirectional measurements can be made and the egress and ingress edge points are coupled to the time protocol assistant. The method also includes synchronizing one or more packets flowing through a network that includes the TSD through the same time source. In more specific embodiments, the nodes are synchronized to the same time source via the network and the same time source is a grandmaster clock that synchronizes one or more transparent clocks. In yet other embodiments, the transparent clocks manipulate precision time protocol (PTP) packets sent by the grandmaster clock.

Improving reliability of IEEE1588 in electric substation automation

Abstract: The IEEE 1588 precision time protocol seems to be a promising way to handle synchronization requirements of tomorrow substation automation. However, one of the remaining issues is its lack of reliability in case of the loss of the GPS signal (e.g. due to atmospheric disturbances or failure of the GPS antenna) which would lead to the desynchronization of the devices inside a substation or between different substations. To keep the devices synchronized without the GPS signal, this paper explores different drift clock prediction techniques. Three main approaches based on statistical, probabilistic and time series techniques are evaluated. On one hand, a statistical-based prediction technique can easily reach an accuracy of less than 10 musec for a prediction duration of a couple of seconds at a minimal computing cost. On the other hand, a time series-based prediction technique can provide an accuracy of 76 musec over a period of 48 hours but at a much higher computing power cost. Finally, we identify the most suitable technique for different type of GPS signal loss that typically occurs in the context of substation automation.

System and method for reducing latency associated with timestamps in a multi-core, multi-threaded processor

Abstract: A system and method are provided for reducing a latency associated with timestamps in a multi-core, multi threaded processor. A processor capable of simultaneously processing a plurality of threads is provided. The processor includes a plurality of cores, a plurality of network interfaces for network communication, and a timer circuit for reducing a latency associated with timestamps used for synchronization of the network communication utilizing a precision time protocol.

Synchronization performance of the Precision Time Protocol in the face of slave clock frequency drift

Abstract: This paper studies the performance of the precision time protocol (PTP) of the IEEE 1588 standard for drifting slave frequencies. The error expression for the master time estimate at the nth slave is analytically derived and demonstrated in simulation runs. We show that single-slave frequency drift is very benign compared to master frequency drift, which is only matched by all slaves drifting.

Synchronization performance of the Precision Time Protocol: Effect of clock frequency drift on the line delay computation

Abstract: The Precision Time Protocol (PTP) of the IEEE 1588 standard relies on two processes: the timing propagation process and the line delay estimation process It is important to study the factors that affect the quality of these synchronization sub-processes, in order to expand the limit on the number of slaves synchronizable within a given synchronization precision This short work-in-progress paper analytically studies the sensitivity of the line delay computation to linear clock frequency drift

1μs-conform line length of the Transparent Clock Mechanism defined by the Precision Time Protocol (PTP Version 2)

Abstract: This paper quantifies the ldquo1 mus-conformrdquo line-length of the Transparent Clock Mechanism of peer-to-peer Precision Time Protocol (PTP Version 2), i.e. the number of elements that stay within the plusmn1 mus sync error tolerance, for crystal oscillator output frequencies of 100 MHz, 250 MHz, 500 MHz and 1 GHz, i.e. for time quantization errors of 10 ns, 4 ns, 2 ns and 1 ns.

Implementation of local area network extension for instrumentation standard trigger capabilities in advanced data acquisition platforms.

Abstract: Synchronization mechanisms are an essential part of the real-time distributed data acquisition systems (DASs) used in fusion experiments. Traditionally, they have been based on the use of digital signals. The approach known as local area network extension for instrumentation (LXI) provides a set of very powerful synchronization and trigger mechanisms. The Intelligent Test Measurement System (ITMS) is a new platform designed to implement distributed data acquisition and fast data processing for fusion experiments. It is based on COMPATPCI technology and its extension to instrumentation (PXI). Hardware and software elements have been developed to include LXI trigger and synchronization mechanisms in this platform in order to obtain a class A LXI instrument. This paper describes the implementation of such a system, involving the following components: commercial hardware running a Linux operating system; a real-time extension to an operating system and network (RTAI and RTNET), which implements a software precision time protocol (PTP) using IEEE1588; an ad hoc PXI module to support hardware implementation of PTP-IEEE 1588; and the multipoint, low-voltage differential signaling hardware LXI trigger bus.

Time synchronization aid device, clock synchronization device, master communication station, and slave communication station

Abstract: PROBLEM TO BE SOLVED: To precisely synchronize clocks of a slave station of a wireless network enabling an IP access based on a PTP (high precision time protocol) synchronization protocol SOLUTION: The device (DA1) aids a clock synchronization device (DS1) by means of a master station (SM) in a wireless network when implementing a time synchronization procedure The master station includes a master clock (HM) represented as a value of a master counter (CM) and means (MG1) for generating wireless frames of IP packets containing particularly PTP messages of first and second types The aid device (DA1) includes detection means (MD1) and triggers sampling of a master clock value when a frame pulse received from the network is detected in a physical layer of the master station COPYRIGHT: (C)2008,JPO&INPIT

Clock synchronization aid device for communication station(s) of a wireless network, and associated clock synchronization device

Abstract: A clock synchronization aid device for communication stations of a wireless network and an associated clock synchronization device are provided to perform the synchronization of slave clocks of a slave communication station with master clocks of a master communication station. In a clock synchronization aid device(DA1) for communication stations of a wireless network, a master station(SM) includes a master clock(HM) to limit a reference time represented by a value of a master counter. The clock synchronization aid device includes a detecting unit(MD1) to trigger sampling of values of the master counter when a frame pulse received from the network is detected by a physical layer of the master station. When the master station includes a generating unit(MG1) to generate first and second types of PTP(Precision Time Protocol) messages in the form of a wireless frame of an IP(Internet Protocol) packet, each of the first type PTP messages signals transmission in the second type message following the first type message among images of the sampling of the values of the master counter. The detecting unit detects whether the wireless frame transmitted by the master station includes at least a selected part of the first type message and correlates the wireless frame with the sampling of the values of the master counter if the wireless frame includes at least the selected part of the first type message. If the wireless frame actually includes the first type message, the clock synchronization aid device is alerted to supply the images of the sampling to the generating unit so that the generating unit integrates images in the second type message following the first type message.

Test method and realization of EPA time synchronization

Abstract: According to the synchronous principle of PTP Precision Time Protocol, the test method and implement of time synchronization was researched. The test method and test system structure of time synchronization were put forward. The time synchronization test apparatus was developed. The practical application of test system indicate the validity of this test method.

Next Steps in Network Time Synchronization For Navy Shipboard Applications

Abstract: : Next generation Navy platform designs are evolving towards generalized multipurpose infrastructures based on open standards and commercial products. These platforms will support a wide range of new and expanding applications in a more flexible and dynamic manner than in previous designs. This new paradigm creates significant network time synchronization challenges. The Navy has been deploying the Network Time Protocol (NTP) in shipboard computing infrastructures to meet the current network time synchronization requirements. Additionally, a new standard, IEEE 1588 or the Precision Time Protocol (PTP), has emerged. It holds the promise of more precise synchronization through the use of hardware assists. New international standardization efforts intend to leverage NTP and PTP for a next generation of time synchronization protocols. This paper examines the emerging work in the International Standards communities in the area of precise network time synchronization. Additionally, it looks at preliminary evaluations of NTP and PTP in the types of products commonly used in Navy shipboard applications. Finally, this paper proposes potential focus areas for Navy standardization and experimentation efforts.

Study and implementation of Precision Time Protocol with C

Abstract: It is an important field of research to achieve precise time synchronization with precision time protocol in network. This paper mainly studies the kernel mechanism of synchronizing the clock between the host and slave devices with PTP, on which base the system is designed and realized through software simulation with the programming tool C#. The precision of synchronization reaches one millisecond. And simulation results show the validity of the proposed controller design method.

Estimation of the clock TIE state space model using a thinning unbiased FIR filtering algorithm

Abstract: A thinning algorithm is proposed for real-time unbiased finite impulse response (FIR) estimation of the local clock time interval error (TIE) model (time error, fractional frequency offset, linear frequency drift rate, etc.) employing GPS-based sawtooth measurements. We show that the approach allows obtaining practically optimal estimates of the clock states, by large horizons (number of the points in the average). The algorithm is applied to the TIE measurements allowing for different time steps and averaging horizons for each of the clock states and compared to the three state Kalman filter. It is demonstrated that, in the presence of the sawtooth noise induced by the GPS receiver, the unbiased FIR estimates with thinning out fit the clock states better than the Kalman filter, in terms of the Allan deviation and precision time protocol deviation.