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Synchronisation signif icantly impacts network performance.The
global demand for telecommunications is increasing at an incredible
pace result ing in networks becoming moreand more sophisticated.
The same is true for synchronisation elements as they are
fundamental to any
telecommunications network. The qualit y and precision of
clocking equipment has a signif icant impact on a
networksperformance. Digital networks require a reliable supply of
accurate and stable synchronisation.
The ITU- T Recommendation G.811states that a PRC provides the
reference signal for the synchronisation of other clockswithin a
network. The long- term accuracy of the PRC should be maintained at
one part in 1011 or better with verif icationto Co-ordinated
Universal Time (UTC). The synchronisation reference frequency is
usually generated by PrimaryReference Clocks (PRCs) and d
istributed through the network. The availabi li ty requirements of
SDH based networksentails the use of multiple-site PRC systems.
Fexible ApproachA PRC may be an autonomous clock; alternatively,
it can be a non-autonomous clock that is locked to
UTC-derivedsignals. In either case, the requirements for long- term
accuracy and short- term stabi li ty , stil l apply.
Oscilloquartz PRCs comprise atomic Cesium clocks and/ or GPS
receivers as reference frequency sources. As theavailability of
synchronisation is crucial for the network, PRCs are implemented
with redundant reference sources.
Most networks are synchronised by decentral ised PRCs to achieve
protection against failures affecting a complete sit e.Todays PRCs
need to provide a flexible approach that allows the PRC to evolve
as the network grows, have a reliableand resil ient architecture
and interface with a management platform that can manage the entire
synchronisationnetwork.
Outputs
Output Signal Generator
Oscillator
and
Tracking Units
GPSReceiverCaesium Clock
GPSReceiver
InputInterface
Unit
InputInterface
Unit
Input
InterfaceUnit
InputInterface
Unit
GPSReceiverCaesium Clock
GPS Antenna
Outputs
Precise Quality
Architecture
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The OSA 6500B achieves the objectives required fordistributed
and stand-alone PRCs especially when thesystem is controlled by the
Oscil loquartz SyncViewsynchronisation management system.
A typical 6500B rack comprises Cesium and GPSreferences, a
synchronisation element, outputdistr ibution, alarms, management
and power suppl ies.
At the core of the OSA 6500B is an OSA 5548B StandAlone
Synchronisation Element (SASE) that handlesmany of the systems
primary functions. This reducesthe cost of conventional PRC
configurations andprovides greater management capabili ty .
The OSA 6500B can be equipped with up to threeCesium primary
references, such as the OSA 5585 PRS.This ensures ful l compliance
with the long term stabil it y
requirements of ITU-T, ETSI or Telcordia. The OSA 5585slong l
ife beam tube has an eight year warranty tominimise
maintenance.
An optional integrated GPS Receiver provides UTCtraceable
reference.
Selection of the references uses a priority table, in
eitherautomatic, manual or forced mode. Remote control is
available via the management interfaces.The selected reference
is applied to redundant channelscontaining the high stability
oscillators which providereferences in holdover mode. Swit ching
and phasealignment is automatic.
Output phase coherence is maintained well below 1/8UI, typically
< 15ns, in the event of any switchingoperation to minimise phase
variations in the network.
The OSA 6500B can be installed wi th a reducedconfiguration and
later expanded int o more complexnetwork.
Achieves Objectives
High Output CapacityThe OSA 6500B delivers up to 112 unprotected
or 64protected outputs or other combinations to suitindividual
requirements. Output capacity can beincreased to several hundreds
of outputs by adding OSA5530B expansion subracks.
Wide range of output interfacesSeveral output interface modules
are available each with16 outputs. Interface types include 2.048
Mbit / s, 2.048MHz, 1.544 Mbit/ s, 5 and 10 MHz.
All outputs can be squelched individually. The 2.048 and1.544
Mbit / s modules include provisions for SSMhandling. Output
squelching and SSM are configurableby the user via the management
interfaces.
Alarms and MonitoringThe OSA 6500B provides comprehensive alarm
reportingand remote monitoring capabil it ies. An alarm
paneldisplays urgent and non-urgent alarms. Monitoring andcontrol
are provided by a local management port . Theinterface allows the
user to configure the system as wellas to receive spontaneous
events and alarms with dateand time stamp.
Remote ManagementAn Embedded System Manager (ESM) ensures
effectivemanagement of the OSA 6500B by providing
extensivemanagement capabilit ies.
It provides a gateway to Oscilloquartzs centralmanagement
system, SyncView, and Local Manager.
Dedicated X25 or Ethernet communication ports providedirect
connection to the management system without theneed for addit ional
mediation devices.
This platform enables full management capabil it ies,including
spontaneous alarm report ing, equipmentconfiguration, alarm and
event log, real t ime calculationof MTIE& TDEV curves, security
and many otherfunctions.
The ESM software can be down- loaded from SyncView.ESM has no
impact on the overall equipment reliabi li ty .Internal
rearrangements and critical decisions are always
made automatically by the equipment itself, withoutintervent ion
of the ESM module.
User Choice
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ContinuousreferenceOSA 6500BPrimary Reference Clock
Decentralised PRCsMany telecom operators opt for a decentral
ised PRCarrangement especially in large countries, complexnetworks
or where network security is of paramountimportance. The network is
synchronised by severalPRCs, which are at dif ferent geographical
sites, toprotect against site failures. This ensures a higherdegree
of reliabil ity as the nodes receive referencesfrom at least two
sources which are routed overseparate paths.
In a PDH environment, references from one PRC areprovided to the
other using dedicated 2.048 Mbit/ slines. System status and control
uses the status bi ts in
the 2.048 Mbit/ s links. In an SDH networksynchronisation is
carried from the PRC to the SASE/SSUusing the STM-N signals.
Normally one of the PRCs is declared master. Thenetwork and
stand-by PRC derive their references fromthe master. In the event
of a failure the system willautomatically change over to ensure
continuoussynchronisation.
The OSA 6500B when combined with the SyncViewManagement System
achieves the objective of adistributed PRC arrangement.
We have detailed product informat ion for the OSA 5585, OSA
5548B, OSA 5548C, OSA 5533C, OSA 5581C and SyncView.Call your local
representative to obtain your fee copy.
Ed. 02-Sept . 2003Oscill oquartz SA reserves the right t o
change all specifications contained herein at any t ime without
prior noti ce.
Oscil loquartz S.A.- Rue des Brvards 162002
NeuchtelSwitzerlandtel. +410)32 722 55 55ax +410)32 722 55
[email protected]
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