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Clocks, Time Error, and Noise

By Shahid Ajmeri, Dennis Hagarty, Anshul Tanwar.
Sample Chapter is provided courtesy of Cisco Press.
Date: Jan 8, 2022.

Chapter Information

Chapter Description

In the world of electronics, the term clock refers to a microchip that generates a clock signal, which is used to regulate the timing and speed of the components on a circuit board. This sample chapter from Synchronizing 5G Mobile Networks explains the different metrics used to quantify time error and how to measure them.

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Chapter 5 Acronyms Key

The following table expands the key acronyms used in this chapter.

Term	Value
μs	microsecond or 1 × 10^-6 second
4G	4th generation (mobile telecommunications system)
BITS	building integrated timing supply (SONET)
cTE	constant time error
DPLL	digital phase-locked loop
dTE	dynamic time error
E1	2-Mbps (2048-kbps) signal (SDH)
EEC	Ethernet equipment clock
ESMC	Ethernet synchronization messaging channel
FFD	fractional frequency deviation
FFO	fractional frequency offset
GPS	Global Positioning System
HPF	high-pass filter
ITU	International Telecommunication Union
ITU-T	ITU Telecommunication Standardization Sector
LPF	low-pass filter
LTE	Long Term Evolution (mobile communications standard)
max\|TE\|	maximum absolute time error
MTIE	maximum time interval error
NE	network element
OCXO	oven-controlled crystal oscillator
PLL	phase-locked loop
ppb	parts per billion
ppm	parts per million
PRC	primary reference clock (SDH)
PRS	primary reference source (SONET)
PRTC	primary reference time clock
PRTC-A	primary reference time clock—class A
PRTC-B	primary reference time clock—class B
PTP	precision time protocol
RMS	root mean square
SDH	synchronous digital hierarchy (optical transport technology)
SDO	standards development organization
SEC	SDH equipment clock
SONET	synchronous optical network (optical transport technology)
SSU	synchronization supply unit (SDH)
SyncE	synchronous Ethernet—a set of ITU-T standards
T1	1.544-Mbps signal (SONET)
TCXO	temperature-compensated crystal oscillator
TDEV	time deviation
TE	time error
TIE	time interval error
VCO	voltage-controlled oscillator
VCXO	voltage-controlled crystal oscillator
XO	crystal oscillator

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