Overview - Symmetricom TimeSource 3600 User Manual

Chapter 1 Overview of the TimeSource 3600

Overview

Overview
The TimeSource 3600 is a Primary Reference Source (PRS) that receives and
processes signals from GPS satellites, and outputs Stratum 1 synchronization
signals traceable to UTC. TimeSource 3600 applications include synchronization for
central offices, wireless base stations, transmission nodes, and other cases where a
primary reference source can improve the performance of a telecommunications
network infrastructure.
The TimeSource 3600 is also ideal for installation in environments where receiving
GPS signals is difficult. Examples of environments hostile to GPS signals include
urban canyons which have a very limited view of the sky because of blockage from
nearby buildings, and high interference zones where GPS signals are jammed by
competing over-the-air signals.
The TimeSource 3600 creates timing outputs by ensembling signals from several
sources. The sources include GPS signals, an onboard rubidium local oscillator,
and optional E1 or analog signals. Timing outputs created from the ensemble are
composed of the most stable and least noisy parts of each input. The performance
of the E1 sources can be monitored and classified using standard measures.
Synchronization outputs are delivered in a framed, all-ones, E1 format or 2.048
MHz analog signal, a 10 MHz signal, a 1 pps signal, and a choice of time of day
(TOD) formats.
The TimeSource 3600 minimizes timing impairments, such as jitter and wander, that
are created by network and transmission systems. The synchronization timing is
traceable to the GPS, which provides the highest level of synchronization for
telephony networks. The TimeSource 3600 with its GPS input is a stand-alone office
PRS. With the optional inputs ensembled, holdover is extended if GPS signals are
disrupted.
Global Positioning System
The United States Government developed the GPS navigation system. It is a
satellite-based, radio navigation aid designed to provide global, all-weather, precise
navigation and timing capability to users 24 hours a day.
The satellites, circling the earth at approximately 20,197 km, are arranged in 6 orbits
with 4 operational satellites in each orbit. Each satellite has an orbital period of
approximately 12 hours. This configuration assures that a minimum of 4 satellites,
and as many as 12, are in view anywhere in the world at all times.
The TimeSource 3600 tracks all satellites within its field of view. The performance of
each tracked satellite is observed and compared to the others, and available for use
in the timing solution. A satellite with unacceptable performance data is dropped
from the timing solution.
22 TimeSource 3600 User's Guide 097-72060-01 Revision J – June, 2007