NTS-3000 Acronyms and synchronization terms

Synchronization terms

Accuracy - The degree of conformity of a measured or calculated value to its definition or with respect to a standard reference time. In the meaning of NTP (Network Time Protocol) the accuracy determines how close the PC clock is to UTC reference (GNSS or external atomic clock).

Atomic Time Scale (TA) - a time scale based on atomic or molecular resonance phenomena. Elapsed time is measured by counting cycles of a frequency locked to an atomic or molecular transition. Earlier time scales were based on the rotational rate of the earth.

GBEIDOU– (see COMPASS)

Calibration - The process of identifying and measuring time or frequency errors, offsets, or deviations of a clock/oscillator relative to an established standard, such as UTC(NIST).

Clock - a device for maintaining and displaying time.

GOMPASS (BEIDOU)– is Chinese satellite navigation system. It consists of two separate satellite constellations – a limited test system that has been operating since 2000, and a full-scale global navigation system that is currently under construction. The first BeiDou system, officially called the BeiDou Satellite Navigation Experimental System.

Coordinated Universal Time (UTC) - a coordinated time scale, maintained by the Bureau International des Poids et Mesures (BIPM), which forms the basis of a coordinated dissemination of standard frequencies and time signals. A UTC clock has the same rate as a Temps Atomique International (TAI) clock or international atomic time clock but differs by an integral number of seconds called leap seconds. The UTC scale is adjusted by the insertion or deletion of leap seconds to ensure approximate agreement with UT1.

Drift (frequency) - the linear (first-order) component of a systematic change in frequency of an oscillator over time.

Frequency - the rate at which a periodic phenomenon occurs over time. Frequency drift - see drift.

Frequency offset - the frequency difference between the measured value and the defined value.

Frequency shift - change in frequency from a standard reference. Frequency stability - statistical estimate of the frequency fluctuations of a signal over a given time interval.

Frequency standard - an oscillator such as a rubidium (Rb), cesium (Cs), or hydrogen (H) maser who’s output is used as a frequency.

GALILEO – is a global navigation satellite system (GNSS) currently being built by the European Union (EU) and European Space Agency (ESA). One of the aims of Galileo is to provide a high-precision positioning system upon which European nations can rely, independently from the GLONASS, US GPS, and Chinese COMPASS (BEIDOU) which can be disabled in times of war or conflict. Galileo is compatible to US GPS (see GPS).

GLONASS – acronym for Globalnaya navigatsionnaya sputnikovaya sistema or Global Navigation Satellite System, is a space-based satellite navigation system. It provides an alternative to Global Positioning System (GPS) and is the only alternative navigational system in operation with global coverage and of comparable precision. Glonass use L1-1575.42MHz with additional frequency margin between 1597.50-1609.50Mhz.

GPS (Global Positioning System) - a highly accurate, global satellite navigation system based on a constellation of at 24 satellites orbiting the earth at a very high altitude 20000 km. GPS signals are: L1-1575.42MHz;L2-1227.6MHz;L3-1381.05 MHz

GMT (Greenwich Mean Time) - a 24 Hour system based on mean solar time plus 12 hours at Greenwich, England. Greenwich Mean Time can be considered approximately equivalent to Coordinated Universal Time (UTC), which is broadcast from all standard time and frequency radio stations. However, GMT is now obsolete and has been replaced by UTC.

International Atomic Time (TAI) - an atomic time scale based on data from a worldwide set of atomic clocks. It is the internationally agreed upon time reference conforming to the definition of the second, the fundamental unit of atomic time in the International System of Units (SI). It is defined as the duration of 9 192 631 770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium - 133 atom.

Synchronization - The process of measuring the difference in time of two time scales such as the output signals generated by two clocks. In the context of timing, synchronization means to bring two clocks or data streams into phase so that their difference is 0 (see time scales in synchronism).

Synchronization - Relative adjustment of two frequency sources with the purpose of canceling their frequency difference but not necessarily their phase difference.

Stability (frequency) - statistical estimate of the frequency fluctuations of a signal over a given time interval: Long term stability usually involves measurement averages beyond 100s. Short term stability usually involves measurement averages from a few tenths of a second to 100s.

Stratum - indicates how fare from cesium ref. the clock is in the chain of synchronization.

Time code - a system of symbols (digital or analog) used for identifying specific instants of time. An information format used to convey time information. IRIG-B is example of Time Code.

Time interval - The duration between two instants read on the same time scale.

Time scale - a system of unambiguous ordering of events. A time scale is meant to be stable and homogeneous.

Time standard - a continuously operated device used for the realization of a time scale in accordance with the definition of the second and with an appropriately chosen origin.

Time step - a discontinuity in a time scale at some instant. A step is positive (+) if the time scale reading is increased and negative (-) if the reading is decreased at that instant.

Acronyms

1PPS	1 Pulse Per Second
AIV	Assembly, Integration and Validation
CA	Bureau International des Poids et Mesures
CCTF	Consultative Committee for Time and Frequency
CIF	Core Infrastructure Facilities
COTS	Commercial Off-the-Shelf
CV	Common View
DAB	Digital Audio Broadcasting
DEMETRA	Demonstrator for EGNSS services based on Time Reference Architecture
DB	Database (mostly SQL)
DVB	Digital Video Broadcasting
ETH	Ethernet
EBU	European Broadcast Union
EGNOS	European geostationary navigation overlay system
EGNSS	European GNSS
EURAMET	European Regional Metrological Organisation
EWR	Extended White Rabbit
FO	Fibber Optic
FR	FREE-RUN mode
GCC	Galileo Control Centre
FTP	File Transfer Protocol
GDO	GPS Disciplined Oscillator
GGTO	Galileo GPS Time Offset
GMT	Greenwich Mean Time
GNSS	Global Navigation Satellite System
GPS	Global Positioning System
GPST	GPS Time Scale
GSA	GNSS Supervising Authority
GST	Galileo System Time
HTTP HTTPS	Hypertext Transfer Protocol Hypertext Transfer Protocol Secure
HO	HOLDOVER mode (e.g. operating w/o GNSS)
HW	Hardware
IPR	Intellectual Property Rights
IRIG-B	Time Code (AM or DM)
ITU	International Telecom Union
KPI	Key Performance Indicator
MCT	Modular Coherent Transfer
NMI	National Metrological Institutes
NTA	National Time Authority (mostly the same as NMI)
NTP	Network Time Protocol
OFT	Optical Fibber Technology
OSC	Oscillators (OCXO, Rubidium, Cs)
PPP	Point Precise Positioning
PTP PTPv2	Precise Time Protocol IEEE 1588 (WR –White Rabbit profile of PTP)
QR	Quality Report
RINEX	Receiver Independent Exchange Format
RMO	Regional Metrological Organization
SFN	Single Frequency Network
SIS	Signal In Space
SPF	Service Provision Facility
SV SVN#	Satellite Vehicle Satellite Vehicle Number
SVF	Service Validation Facility
SW	Software
T&F	Time and(&) Frequency
TAI	International Atomic Time
TA(PL)	Polish Atomic Time
TDMA	Time Division Multiple Access
TFL	Time and Frequency Laboratory
TLC	Time Local Clock (the same as UT)
TMC	Time Master Clock (see TSG)
TRF	Time Reference Facility (see TMC)
TSA	Time Stamping Authority
TSI	Time Service Infrastructures
TWSTF	Two Way Satellite Time and Frequency Transfer
UT	User Terminal (see also TLC)
UTC	Universal Time Coordinated
WP	Work Package
WR	White Rabbit (see PTP)
WPL	Work Package Leader