Characterizing the performance of GPS disciplined oscillators with respect to UTC(NIT)

Lombardi, Michael A.; Novick, Andrew N.; Zhang, V.S.

doi:10.1109/freq.2005.1574017

Cited by 23 publications

(22 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We calibrated the masters for twenty-four hours and entered the average delays into the units to compensate for their offset from UTC(NIST) due to position errors, cable delays and hardware delays. The PTP masters have internal GPS disciplined oscillators (GPSDOs) that can vary significantly from device to device [4]. Figure 2 shows a comparison of the 1 pps outputs of the four PTP masters, with peak-to-peak variations that range from 30 ns to greater than 110 ns.…”

Section: Methodsmentioning

confidence: 98%

“…At present, there is no ITU requirement for time accuracy. In order to know how well a particular PTP master works with a GPSDO as its reference, it is advisable to have it calibrated by NIST or another National Metrology Institute (NMI) or a calibration laboratory [4]. Ideally, a GPSDO calibration should be performed with the antenna and cable that will be used in the field, leaving only the coordinate error.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Examination of time and frequency control across wide area networks using IEEE-1588v2 unicast transmissions

Novick

Weiss

Lee

et al. 2011

2011 Joint Conference of the IEEE International Frequency Control and the European Frequency and Time Forum (FCS) Proceedings

View full text Add to dashboard Cite

The IEEE 1588-2008 Precision Time Protocol (PTP) version 2 (IEEE 1588v2) can be used to synchronize a slave clock to a grandmaster clock over a wide area network (WAN). However, many of the algorithms the slaves use to steer to the master are optimized for a scenario where both devices are on the same subnet or local area network (LAN). This paper is a study of existing PTP hardware from a number of different manufacturers in unicast mode. We characterize the performance of the equipment, beginning with the timing outputs of the masters that are locked to their built-in Global Positioning System (GPS) receivers. Next, we compare the results of steering unicast clients to their masters through a LAN versus several wider-area network configurations such as virtual-LANs and the public Internet. Analysis of the results will show how clients of different manufacture handle the various network paths. It is our hope that these comparisons will instigate changes to clock steering and synchronization algorithms, which may help improve the overall capabilities of PTP for telecom and other networking environments. As network synchronization techniques improve, the quality of the PTP masters will become more significant. Therefore, the performance and calibration of PTP masters with respect to UTC(NIST) is also discussed.

show abstract

Section: Methodsmentioning

confidence: 98%

Section: Methodsmentioning

confidence: 99%

Examination of time and frequency control across wide area networks using IEEE-1588v2 unicast transmissions

Novick

Weiss

Lee

et al. 2011

2011 Joint Conference of the IEEE International Frequency Control and the European Frequency and Time Forum (FCS) Proceedings

View full text Add to dashboard Cite

show abstract

“…The timing accuracy under such condition usually depends on the stability of the local oscillator. Currently, the GPS disciplined oscillator (i.e., GPS receiver combined with a highly stable oscillator) [39] is widely used in timing applications. It provides accurate time synchronization even when GPS reception is disrupted.…”

Section: Protocol Designmentioning

confidence: 99%

Congestion-Controlled-Coordinator-Based MAC for Safety-Critical Message Transmission in VANETs

Sahoo¹,

Sahu³

et al. 2013

IEEE Trans. Intell. Transport. Syst.

View full text Add to dashboard Cite

Vehicular ad hoc networks (VANETs) provide the communication framework for the dissemination of safety-critical messages such as beacons and emergency messages. The communication channel witnesses significant network load generated by frequently exchanged beacons. Under high-density situations, it leads to a serious scalability problem in VANETs. Moreover, contention-based medium access control (MAC) protocols suffer from a great number of packet collisions, and as a result, the reliability and latency of safety messages are severely affected. Because of the periodic nature of beacons, time-division multiple access (TDMA) can be a good choice over contention-based MAC. In this paper, we propose congestion-controlled-coordinator-based MAC (CCC-MAC), which is a time-slot-based medium access protocol that addresses beacons and emergency messages. Basically, the network is virtually partitioned into a number of segments. Within a segment, medium access is accomplished by using a time-slot-scheduling mechanism supervised by a local coordinator vehicle. A significant number of vehicles can be supported under the proposed configuration. In fact, the proposed scheduling mitigates channel congestion by reducing the transmission time of beacons through the use of multiple data rates. Bandwidth utilization is also improved by reusing the unoccupied time slots. Finally, CCC-MAC ensures fast and reliable propagation of emergency messages by employing a pulse-based reservation mechanism.In the simulations, we demonstrate the ability of CCC-MAC to scale well in different vehicular density scenarios. Moreover, it outperforms existing MAC-layer protocols with respect to packet reception probability and latency of safety messages.Index Terms-Beacon, dedicated short-range communications (DSRC), emergency message, IEEE 802.11p, vehicular ad hoc network (VANET).

show abstract

“…Some authors propose applying the Kalman filters [13]- [15] and even neural networks [16]. Experimental investigations of several GPSDOs utilizing different filters can be found in [17] [18].…”

Section: Introductionmentioning

confidence: 99%

Efficient predictive steering of local clocks in GPS-based timekeeping

Shmaliy

Ibarra-Manzano

Arceo-Miquel

2009

2009 IEEE International Frequency Control Symposium Joint With the 22nd European Frequency and Time Forum

View full text Add to dashboard Cite

We discuss optimal synchronization of local clocks by the Global Positioning System (GPS) one pulse per second (1PPS) timing signals. To eliminate sawtooth errors peculiar to the 1PPS signals and optimally steer the clock errors each M seconds, we propose using a ramp predictive finite impulse response (FIR) filter that is known to be optimal for clock models on large averaging horizons. A low-pass filter is used to smooth the hold filter output between the optimally predicted points. A GPS locked crystal clock has been investigated in detail in terms of the time interval error, Allan deviation, and precision time protocol (PTP) variance. A high efficiency implementation of the proposed synchronization algorithm is demonstrated experimentally.

show abstract

Characterizing the performance of GPS disciplined oscillators with respect to UTC(NIT)

Cited by 23 publications

References 8 publications

Examination of time and frequency control across wide area networks using IEEE-1588v2 unicast transmissions

Examination of time and frequency control across wide area networks using IEEE-1588v2 unicast transmissions

Congestion-Controlled-Coordinator-Based MAC for Safety-Critical Message Transmission in VANETs

Efficient predictive steering of local clocks in GPS-based timekeeping

Contact Info

Product

Resources

About