Issue 05/01 Slide 1.1 http://www.oscilloquartz.com Oscilloquartz SA
The Synchronisation ofTelecommunications Networks
Issue 05/01 Slide 1.2 http://www.oscilloquartz.com Oscilloquartz SA
ContentsContentsI. The Need for Synchronisation
II. Characterizing Synchronisation Quality
III. Synchronisation Distribution: General Principles
IV. Synchronisation Distribution: SDH/SONET-basedSolution
1. Elements
2. Architecture
3. Synchronisation Status Message (SSM)
V. Synchronisation Distribution: GPS-based andMixedSolution
I. The Need for Synchronisation
II. Characterizing Synchronisation Quality
III. Synchronisation Distribution: General Principles
IV. Synchronisation Distribution: SDH/SONET-basedSolution
1. Elements
2. Architecture
3. Synchronisation Status Message (SSM)
V. Synchronisation Distribution: GPS-based andMixedSolution
Issue 05/01 Slide 1.3 http://www.oscilloquartz.com Oscilloquartz SA
ContentsContents
VI. Synchronisation Distribution: From Co-operating Network
VII. Summary on Standards
VIII. How to Synchronize Mixed TechnologyNetworks
1. Mixed Technology Network Example
2. SDH and SONET Networks
3. The Public Switched Telephony Network
VI. Synchronisation Distribution: From Co-operating Network
VII. Summary on Standards
VIII. How to Synchronize Mixed TechnologyNetworks
1. Mixed Technology Network Example
2. SDH and SONET Networks
3. The Public Switched Telephony Network
Issue 05/01 Slide 1.4 http://www.oscilloquartz.com Oscilloquartz SA
ContentsContents
VIII. How to Synchronize Mixed TechnologyNetworks (cont ’d)
4. ATM Networks
5. Optical Networks
6. GSM and UMTS-FDD Radio Access Networks
7. cdmaOne and cdma2000 Radio Access Networks
VIII. How to Synchronize Mixed TechnologyNetworks (cont ’d)
4. ATM Networks
5. Optical Networks
6. GSM and UMTS-FDD Radio Access Networks
7. cdmaOne and cdma2000 Radio Access Networks
Issue 05/01 Slide 1.5 http://www.oscilloquartz.com Oscilloquartz SA
AbbreviationsAbbreviations» ADM Add Drop Multiplexer
» ATM Asynchronous TransferMode
» BITS Building Integrated TimingSupply
» bit/s bits per second1kbit/s = 1,000 bits/s1Mbit/s = 1,000,000 bits/s1Gbit/s = 1,000,000,000 bit/s
» CBR Constant Bit Rate
» CDV Cell Delay Variation
» DNU Do Not Use
» DXC Digital Cross-Connect
» f frequency
» FIFO First-In First-Out
» GPS Global Positioning System
» GUI Graphical User Interface
» HSC High Stability Clock
» ADM Add Drop Multiplexer
» ATM Asynchronous TransferMode
» BITS Building Integrated TimingSupply
» bit/s bits per second1kbit/s = 1,000 bits/s1Mbit/s = 1,000,000 bits/s1Gbit/s = 1,000,000,000 bit/s
» CBR Constant Bit Rate
» CDV Cell Delay Variation
» DNU Do Not Use
» DXC Digital Cross-Connect
» f frequency
» FIFO First-In First-Out
» GPS Global Positioning System
» GUI Graphical User Interface
» HSC High Stability Clock
» Hz Hertz (cycles per second)1mHz = 0.001Hz1 µHz = 0.000001Hz
» ITU International TelecommunicationsUnion
» k kilo = 1,000
» LOS Loss Of Signal
» LT Line Terminal
» MTIE Maximum Time Interval Error
» NE Network Element
» OC-N Optical Carrier level N
» OS Operating System
» p pointer
» PABX Private Automatic BranchExchange
» PDH Plesiochronous Digital Hierarchy
» PEC Plesiochronous Equipment Clock
» PLL Phase Locked Loop
» Hz Hertz (cycles per second)1mHz = 0.001Hz1 µHz = 0.000001Hz
» ITU International TelecommunicationsUnion
» k kilo = 1,000
» LOS Loss Of Signal
» LT Line Terminal
» MTIE Maximum Time Interval Error
» NE Network Element
» OC-N Optical Carrier level N
» OS Operating System
» p pointer
» PABX Private Automatic BranchExchange
» PDH Plesiochronous Digital Hierarchy
» PEC Plesiochronous Equipment Clock
» PLL Phase Locked Loop
Issue 05/01 Slide 1.6 http://www.oscilloquartz.com Oscilloquartz SA
AbbreviationsAbbreviations» PRC Primary Reference Clock
» ps/km/°C pico seconds per kilometreper degree centigrade
» QL Quality Level
» QOS Quality Of Service
» s second1ms = 0.001s
» SASE Stand Alone Synchronous Equipment
» SD Synchronisation Distribution
» SDH Synchronous Digital Hierarchy
» SC SONET Clock
» SEC Synchronous Equipment Clock
» SETG Synchronous Equipment TimingGenerator
» SETS Synchronous Equipment Timing Source
» sin Sine function
» SOH Section OverHead
» SONET Synchronous Optical Network
» SRTS Synchronous Residual TimeStamp
» PRC Primary Reference Clock
» ps/km/°C pico seconds per kilometreper degree centigrade
» QL Quality Level
» QOS Quality Of Service
» s second1ms = 0.001s
» SASE Stand Alone Synchronous Equipment
» SD Synchronisation Distribution
» SDH Synchronous Digital Hierarchy
» SC SONET Clock
» SEC Synchronous Equipment Clock
» SETG Synchronous Equipment TimingGenerator
» SETS Synchronous Equipment Timing Source
» sin Sine function
» SOH Section OverHead
» SONET Synchronous Optical Network
» SRTS Synchronous Residual TimeStamp
» SSM Synchronisation Status Message
» SSU Synchronisation Supply Unit
» STM-N Synchronous Transport Modulelevel N
» STS-N Synchronous Transport Signallevel N
» TF Transfer Function
» TIE Time Interval Error
» TS0 Time Slot Zero
» VBR Variable Bit Rate
» VCO Voltage Controlled Oscillator
» VC Virtual Container
» VT Virtual Tributary
» VTG Virtual Tributary Group
» UN Undefined
» W Wander
» w radians per second
» d variation
» SSM Synchronisation Status Message
» SSU Synchronisation Supply Unit
» STM-N Synchronous Transport Modulelevel N
» STS-N Synchronous Transport Signallevel N
» TF Transfer Function
» TIE Time Interval Error
» TS0 Time Slot Zero
» VBR Variable Bit Rate
» VCO Voltage Controlled Oscillator
» VC Virtual Container
» VT Virtual Tributary
» VTG Virtual Tributary Group
» UN Undefined
» W Wander
» w radians per second
» d variation
Issue 05/01 Slide 1.7 http://www.oscilloquartz.com Oscilloquartz SA
The Need for SynchronisationThe Need for Synchronisation
Issue 05/01 Slide 1.8 http://www.oscilloquartz.com Oscilloquartz SA
Frequency synchronisationFrequency synchronisation
System A
t
t
Clock signal of system A
Clock signal of system B
System B
TA = 1 / fA
TB = 1 / fB
fA = fB
Issue 05/01 Slide 1.9 http://www.oscilloquartz.com Oscilloquartz SA
Phase synchronisationPhase synchronisation
System A
t
t
Clock signal of system A
Clock signal of system B
System B
! !!
Issue 05/01 Slide 1.10 http://www.oscilloquartz.com Oscilloquartz SA
Time synchronisationTime synchronisation
System A
t
t
Time signal of system A
Time signal of system B
System B
14/01/0008:34:56
14/01/0008:34:57
14/01/0008:34:55
14/01/0008:34:55
14/01/0008:34:56
14/01/0008:34:57
Issue 05/01 Slide 1.11 http://www.oscilloquartz.com Oscilloquartz SA
Where do we need synchronisation?Three examples
Where do we need synchronisation?Three examples
»Public Switched Telephone Networks
»SONET and SDH transport networks
»Cellular mobile telecom networks
»Public Switched Telephone Networks
»SONET and SDH transport networks
»Cellular mobile telecom networks
Issue 05/01 Slide 1.12 http://www.oscilloquartz.com Oscilloquartz SA
Public Switched Telephone Network:Synchronous Multiplexing
Public Switched Telephone Network:Synchronous Multiplexing
30 x 64 kbit/s 1 x 2.048 Mbit/s
Multiplexer
30
1
21 2 30
Issue 05/01 Slide 1.13 http://www.oscilloquartz.com Oscilloquartz SA
Public Switched Telephone Network:Space-Time Switching
Public Switched Telephone Network:Space-Time Switching
Switch
1 2 3 54 6
1 2 3 54 6
N x 2.048 Mbit/s N x 2.048 Mbit/s
Issue 05/01 Slide 1.14 http://www.oscilloquartz.com Oscilloquartz SA
What is a slip?What is a slip?
»A slip occurs when a buffer over- or underflows due to differences in timing
»A slip occurs when a buffer over- or underflows due to differences in timing
Incoming data rate
Outgoing data rate
SlipSlipIncoming data rate
Issue 05/01 Slide 1.15 http://www.oscilloquartz.com Oscilloquartz SA
Some services affected by slipsSome services affected by slips» Voice» Uncompressed - only 5% of slips lead to clicks» Compressed - a slip will cause an audible click
» Facsimile» A slip can wipe out several lines
» Modem» A slip can cause several seconds of drop out
» Compressed video» A slip can wipe out several lines» More slips can freeze frames for several
seconds
» Encrypted/compressed data protocol» Slips will reduce transmission throughput
» Voice» Uncompressed - only 5% of slips lead to clicks» Compressed - a slip will cause an audible click
» Facsimile» A slip can wipe out several lines
» Modem» A slip can cause several seconds of drop out
» Compressed video» A slip can wipe out several lines» More slips can freeze frames for several
seconds
» Encrypted/compressed data protocol» Slips will reduce transmission throughput
Issue 05/01 Slide 1.16 http://www.oscilloquartz.com Oscilloquartz SA
Slip rate due to frequency deviationSlip rate due to frequency deviation
»Slip rate = fractional freq. dev / frame duration
»For 2 Mbit/s signals, frame duration =125 microseconds :»10-11 = 1 slip in 4.8 months»10-10 = 1 slip in 14.5 days»10-9 = 1 slip in 1.45 days»10-8 = 6.9 slips per day»10-7 = 2.9 slips per hour»10-6 = 28.8 slips per hour»10-5 = 4.8 slips per minute
»Slip rate = fractional freq. dev / frame duration
»For 2 Mbit/s signals, frame duration =125 microseconds :»10-11 = 1 slip in 4.8 months»10-10 = 1 slip in 14.5 days»10-9 = 1 slip in 1.45 days»10-8 = 6.9 slips per day»10-7 = 2.9 slips per hour»10-6 = 28.8 slips per hour»10-5 = 4.8 slips per minute
Issue 05/01 Slide 1.17 http://www.oscilloquartz.com Oscilloquartz SA
A customer affected by slips:A customer affected by slips:
Issue 05/01 Slide 1.18 http://www.oscilloquartz.com Oscilloquartz SA
SDH/SONET Transport Networks:Nominally Synchronous MultiplexingSDH/SONET Transport Networks:Nominally Synchronous Multiplexing
63 x E1 1 x STM-1
Multiplexer
63
1
2OH 1 2 63
Issue 05/01 Slide 1.19 http://www.oscilloquartz.com Oscilloquartz SA
Wander induced by pointer activityWander induced by pointer activity
t
TIE of E1 signal
t
TIE of E1 signal
PRC
NE
NE
NE
SDH/SONET Network
ADME1
ADME1
Synchronisation distributiontrails affected by wander
Issue 05/01 Slide 1.20 http://www.oscilloquartz.com Oscilloquartz SA
SDH/SONET Transport Networks:Nominally Synchronous MultiplexingSDH/SONET Transport Networks:Nominally Synchronous Multiplexing
»PDH tributaries need not be synchronous with the SDH aggregates (pointer technique).
»However, relative wander between the incoming PDH tributary and the SDH aggregates induce wander on the outgoing PDH tributary (pointer adjustments!).
» If excessive, this tributary wander causes slips.
»PDH tributaries need not be synchronous with the SDH aggregates (pointer technique).
»However, relative wander between the incoming PDH tributary and the SDH aggregates induce wander on the outgoing PDH tributary (pointer adjustments!).
» If excessive, this tributary wander causes slips.
Issue 05/01 Slide 1.21 http://www.oscilloquartz.com Oscilloquartz SA
Cellular Mobile Telecom NetworksCellular Mobile Telecom Networks
BTS
BTS
BTS
BTS
Successful handover requires synchronisation between base transceiver stations (BTS)
Issue 05/01 Slide 1.22 http://www.oscilloquartz.com Oscilloquartz SA
Cellular Mobile Telecom NetworksCellular Mobile Telecom Networks
Radio carrier frequencies must be synchronized preciselyin order to prevent cross-talk
Radio spectrum
Frequency
Issue 05/01 Slide 1.23 http://www.oscilloquartz.com Oscilloquartz SA
Characterizing Synchronisation Quality
Characterizing Synchronisation Quality
Issue 05/01 Slide 1.24 http://www.oscilloquartz.com Oscilloquartz SA
Definition of jitter : ITU-T Rec. G.810Definition of jitter : ITU-T Rec. G.810ÂThe short term variations of the significant
instants of a digital signal from their reference positions in time
ÂGreater than 10Hz in modulation frequency
ÂThe short term variations of the significantinstants of a digital signal from their reference positions in time
ÂGreater than 10Hz in modulation frequency
IdealIdeal
JitteredJittered
Sampling (reading) pointsSampling (reading) points
Issue 05/01 Slide 1.25 http://www.oscilloquartz.com Oscilloquartz SA
Definition of jitter : ITU-T Rec. G.810Definition of jitter : ITU-T Rec. G.810ÂThe short term variations of the significant
instants of a digital signal from their reference positions in time
ÂGreater than 10Hz in modulation frequency
ÂThe short term variations of the significantinstants of a digital signal from their reference positions in time
ÂGreater than 10Hz in modulation frequency
IdealIdeal
JitteredJittered
Sampling (reading) pointsSampling (reading) points
Issue 05/01 Slide 1.26 http://www.oscilloquartz.com Oscilloquartz SA
Definition of wander : ITU-T Rec. G.810Definition of wander : ITU-T Rec. G.810
·The long term variations of the significantinstants of a digital signal from their reference positions in time
·Less than 10Hz in modulation frequency
·The long term variations of the significantinstants of a digital signal from their reference positions in time
·Less than 10Hz in modulation frequency
IdealIdeal
WanderedWandered
Sampling pointsSampling pointsSampling pointsSampling points
Issue 05/01 Slide 1.27 http://www.oscilloquartz.com Oscilloquartz SA
Tref(t)
T(t)
t
x(t) = jitter + wander
Time Error or Phase-Time x(t)Time Error or Phase-Time x(t)
Issue 05/01 Slide 1.28 http://www.oscilloquartz.com Oscilloquartz SA
Fractional Frequency Deviation y(t)Fractional Frequency Deviation y(t)
y(t) =
where
ν(t) = actual frequency of the signal
νNOM = specified nominal frequency
y(t) =
where
ν(t) = actual frequency of the signal
νNOM = specified nominal frequency
ν(t) - νNOM
νNOM
Issue 05/01 Slide 1.29 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation Distribution:
General Principles
Synchronisation Distribution:
General Principles
Issue 05/01 Slide 1.30 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation between telecommunication systems : 1
Synchronisation between telecommunication systems : 1
»Master-slave intra-network synchronisation»Master-slave intra-network synchronisation
MasterMasterSystemSystemdatadata SlaveSlave
SystemSystem
clockclock
datadatadata +data + clockclock
transmissiontransmissionlinklink
Issue 05/01 Slide 1.31 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation between telecommunication systems : 2
Synchronisation between telecommunication systems : 2
»The slave system continually adjusts its own clock to the incoming signal»The incoming signal contains both the clock
and data information
»Therefore both the master and slavesystems have the same transmit andreceive rates»There are no slips
»The slave system continually adjusts its own clock to the incoming signal»The incoming signal contains both the clock
and data information
»Therefore both the master and slavesystems have the same transmit andreceive rates»There are no slips
Issue 05/01 Slide 1.32 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation between telecommunication systems : 3
Synchronisation between telecommunication systems : 3
» Inter-network synchronisation» Inter-network synchronisation
NetworkNetwork AASystemSystemdatadata NetworkNetwork BB
SystemSystem
atomic clockatomic clock
datadatadata data
atomic clockatomic clock
transmissiontransmissionlinklink
Issue 05/01 Slide 1.33 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation between telecommunication systems : 4
Synchronisation between telecommunication systems : 4
»Each system is synchronised by separate atomic clocks
»The atomic clocks have nearly the samefree running frequency»There is little difference between the transmit
and receive rates at both ends
»The slip rate is only one in every 72 days»Totally acceptable for inter-national and
intra-national traffic of every kind of services
»Each system is synchronised by separate atomic clocks
»The atomic clocks have nearly the samefree running frequency»There is little difference between the transmit
and receive rates at both ends
»The slip rate is only one in every 72 days»Totally acceptable for inter-national and
intra-national traffic of every kind of services
Issue 05/01 Slide 1.34 http://www.oscilloquartz.com Oscilloquartz SA
Physicalsynchronisation network : 1
Physicalsynchronisation network : 1
mastermaster--slaveslavechainschains
PRCPRCPRC
SSU
SynchronisationSynchronisationSupplySupply UnitUnit
SDHSDHEquipment ClockEquipment Clock
PRC =PRC = PrimaryPrimaryReferenceReferenceClockClock
SEC
Telecom equipment clocksTelecom equipment clocks
Issue 05/01 Slide 1.35 http://www.oscilloquartz.com Oscilloquartz SA
Physical synchronisationnetwork : 2
Physical synchronisationnetwork : 2
»Not every system in the network can have a direct connection to the master network clock.
»Therefore the telecommunication systemsare synchronised in chains or trees»Each system clock is the master clock of the
subordinate system clocks slaved to it»The chains can be very long or very short
»Not every system in the network can have a direct connection to the master network clock.
»Therefore the telecommunication systemsare synchronised in chains or trees»Each system clock is the master clock of the
subordinate system clocks slaved to it»The chains can be very long or very short
Issue 05/01 Slide 1.36 http://www.oscilloquartz.com Oscilloquartz SA
Physicalsynchronisation network : 3
Physicalsynchronisation network : 3
PRC SDPRC SD trailtrail clock qualityclock qualitytraceable backtraceable back
to theto the PRCPRC
PRCPRCPRC
SSU
clock qualityclock qualitytraceable backtraceable back
to theto the SECSEC
SEC SDSEC SD trailtrail SSU SDSSU SD trailtrail
clock qualityclock qualitytraceable backtraceable back
to theto the SSUSSU
SEC
Issue 05/01 Slide 1.37 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation Distribution (SD) Trails
Synchronisation Distribution (SD) Trails
»The clock frequency along a SD trail is theSAME as the head-end, ie PRC, SSU or SEC»SD trails can be very long or very short»There can be hundreds of SD trails in a
synchronisation network
»The clock frequency along a SD trail is theSAME as the head-end, ie PRC, SSU or SEC»SD trails can be very long or very short»There can be hundreds of SD trails in a
synchronisation network
Issue 05/01 Slide 1.38 http://www.oscilloquartz.com Oscilloquartz SA
Causes of jitterCauses of jitter
»Phase-noise generated by clock recovery circuits in transmission network elements
»Phase-noise generated by low-quality equipment clocks
»Phase-noise generated by clock recovery circuits in transmission network elements
»Phase-noise generated by low-quality equipment clocks
Issue 05/01 Slide 1.39 http://www.oscilloquartz.com Oscilloquartz SA
Causes of wanderCauses of wander
½Temperature variations induce low-frequency phase-noise in network element clocks
½Temperature variations (e.g. between day and night) modify the propagation delays in transmission cables
½Temperature variations induce low-frequency phase-noise in network element clocks
½Temperature variations (e.g. between day and night) modify the propagation delays in transmission cables
Issue 05/01 Slide 1.40 http://www.oscilloquartz.com Oscilloquartz SA
Jitter and wander controlJitter and wander control
ÁJitter and wander must be kept below predefined limits called Network Limits
ÁTwo distinct techniques are used for the following jitter and wander components:ÁJitter and wander in the spectral domain above ≈
1 mHzÁWander in the spectral domain below ≈ 1 mHz
ÁJitter and wander must be kept below predefined limits called Network Limits
ÁTwo distinct techniques are used for the following jitter and wander components:ÁJitter and wander in the spectral domain above ≈
1 mHzÁWander in the spectral domain below ≈ 1 mHz
Issue 05/01 Slide 1.41 http://www.oscilloquartz.com Oscilloquartz SA
Jitter and wander filteringJitter and wander filtering
ÁRequired to prevent excessive accumulation of jitter and wander in the spectral domain above ≈ 1 mHz
ÁUse very narrow bandwidth (≈ 1 mHz) slaveclocks (SSUs) at intervals on the SD trails
ÁRequired to prevent excessive accumulation of jitter and wander in the spectral domain above ≈ 1 mHz
ÁUse very narrow bandwidth (≈ 1 mHz) slaveclocks (SSUs) at intervals on the SD trails
Issue 05/01 Slide 1.42 http://www.oscilloquartz.com Oscilloquartz SA
PLL transfer function (TF)PLL transfer function (TF)» TF = A plot of : Amplitude of output jitter (frequency)
Amplitude of input jitter (frequency)» TF = A plot of : Amplitude of output jitter (frequency)
Amplitude of input jitter (frequency)
--2020
--1010
00
1010
0.001f0.001f 0.01f0.01fffpeakpeak
ff 10f10f 100f100f
modulationmodulationfrequencyfrequency
Gain inGain in dBdB
--33
peakpeak
RollRoll--offoffFilter BandwidthFilter Bandwidth
0.1f0.1fffcutcut--offoff
Issue 05/01 Slide 1.43 http://www.oscilloquartz.com Oscilloquartz SA
Wander buffering on input portsWander buffering on input ports
»Wander in the spectral domain below the bandwidth of the SSUs cannot be attenuated
ÁThis low frequency wander accumulates across the synchronisation network
ÁBuffer stores on traffic input ports must be able to absorb at least 18 µs of wander
»Wander in the spectral domain below the bandwidth of the SSUs cannot be attenuated
ÁThis low frequency wander accumulates across the synchronisation network
ÁBuffer stores on traffic input ports must be able to absorb at least 18 µs of wander
Issue 05/01 Slide 1.44 http://www.oscilloquartz.com Oscilloquartz SA
Input wander greater than 18µsInput wander greater than 18µs
»The size of the buffer in telecommunications systems is usually just slightly larger than 18µs.
» If the input wander is greater than the size ofthe buffer, then the buffer over- or underflows, thus causing slips.
»To prevent slips the level of wander in the network must be kept below 18 µs.
»The size of the buffer in telecommunications systems is usually just slightly larger than 18µs.
» If the input wander is greater than the size ofthe buffer, then the buffer over- or underflows, thus causing slips.
»To prevent slips the level of wander in the network must be kept below 18 µs.
Issue 05/01 Slide 1.45 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation Distribution:
SDH-Based Solution
Synchronisation Distribution:
SDH-Based Solution
Issue 05/01 Slide 1.46 http://www.oscilloquartz.com Oscilloquartz SA
1. Elements1. Elements
Clocks and LinksClocks and Links
Issue 05/01 Slide 1.47 http://www.oscilloquartz.com Oscilloquartz SA
ClocksClocks
»Primary Reference Clock (PRC)
»Node Clock or Synchronisation Supply Unit (SSU)»If it is an independent piece of equipment, then
it is called a SASE (Stand-Alone Synchronisation Equipment)
»SDH Equipment Clock (SEC)
»Primary Reference Clock (PRC)
»Node Clock or Synchronisation Supply Unit (SSU)»If it is an independent piece of equipment, then
it is called a SASE (Stand-Alone Synchronisation Equipment)
»SDH Equipment Clock (SEC)
Issue 05/01 Slide 1.48 http://www.oscilloquartz.com Oscilloquartz SA
Primary Reference Clock (PRC)Primary Reference Clock (PRC)
»Master clock used to synchronise the entire network with a frequency accuracy of
< 1 x 10-11
»Based on atomic Cesium clocks
»Master clock used to synchronise the entire network with a frequency accuracy of
< 1 x 10-11
»Based on atomic Cesium clocks
Issue 05/01 Slide 1.49 http://www.oscilloquartz.com Oscilloquartz SA
PRC ImplementationPRC Implementation
»Autonomous equipment with one or several atomic Cesium clocks
»Radio-controlled clock synchronized to remote atomic Cesium clocks (e.g. Global Positioning System - GPS)
»A combination of the above
»Autonomous equipment with one or several atomic Cesium clocks
»Radio-controlled clock synchronized to remote atomic Cesium clocks (e.g. Global Positioning System - GPS)
»A combination of the above
Issue 05/01 Slide 1.50 http://www.oscilloquartz.com Oscilloquartz SA
Node Clock or SynchronisationSupply Unit (SSU)
Node Clock or SynchronisationSupply Unit (SSU)
Reference
Selector
Input
Interface
Input
Interface
Input
InterfaceOutput
Interface
Output
Interface
Output
Interface
Output
InterfaceJitter/Wander
Low-Pass
Filter
Holdover
Memory
Issue 05/01 Slide 1.51 http://www.oscilloquartz.com Oscilloquartz SA
Node Clock or Synchronisation Supply Unit (SSU)
Node Clock or Synchronisation Supply Unit (SSU)
»Selects an input reference signal based on»priority table, or»SSM signaling and priority table.
»Attenuates the jitter and wander present at the input via narrow-band (mHz) low-pass filtering.
» If all reference signals are lost, maintains the last phase & frequency as good as it can (holdover mode).
»Selects an input reference signal based on»priority table, or»SSM signaling and priority table.
»Attenuates the jitter and wander present at the input via narrow-band (mHz) low-pass filtering.
» If all reference signals are lost, maintains the last phase & frequency as good as it can (holdover mode).
Issue 05/01 Slide 1.52 http://www.oscilloquartz.com Oscilloquartz SA
• SSU Type• Application
Frequencyaccuracy
Holdover frequencydeparture Bandwith
Type I2048 kbit/s based N/A 5E-10 + t x 2E-10 / day 3 mHz
Type II1544 kbit/s based 1.6E-8 1E-10 + t x 1E-10 / day 1 mHz
Type III1544 kbit/s based 4.6E-6 1E-9 + t x 1E-9 / day 1 mHz
Node Clock or Synchronisation Supply Unit (SSU)
Node Clock or Synchronisation Supply Unit (SSU)
Issue 05/01 Slide 1.53 http://www.oscilloquartz.com Oscilloquartz SA
SDH network element ’s synchronisation functionSDH network element ’s synchronisation function
STM-Ninput external
timing output(2 MHz or1.5 Mbit/s, or 2 Mbit/s)
externaltiminginput(2 MHz or1.5 Mbit/s or 2Mbit/s)
SynchronousSynchronousEquipmentEquipment
TimingTimingGeneratorGenerator
SelectorSelector BB
NEinternaltiming
Synchronous Equipment Timing Source (SETS)
SelectorSelector CC
PDHinput
SelectorSelector AA
SDH Equipmemt Clock
Issue 05/01 Slide 1.54 http://www.oscilloquartz.com Oscilloquartz SA
SDH SEC featuresSDH SEC featuresÀ Input synchronisation signals are :»STM-N aggregates and tributaries»2 Mbit/s tributaries»2 MHz, 2 or 1.5 Mbit/s (non traffic) timing inputs
À Input selection is determined by :»a priority table, that is user definable»Synchronisation Status Message (SSM) on the
STM-N and 2 Mbit/s interfaces
ÀOutput synchronisation signals are :»All STM-N aggregates and tributaries»2 MHz, 2 or 1.5 Mbit/s (non traffic) timing
outputs
À Input synchronisation signals are :»STM-N aggregates and tributaries»2 Mbit/s tributaries»2 MHz, 2 or 1.5 Mbit/s (non traffic) timing inputs
À Input selection is determined by :»a priority table, that is user definable»Synchronisation Status Message (SSM) on the
STM-N and 2 Mbit/s interfaces
ÀOutput synchronisation signals are :»All STM-N aggregates and tributaries»2 MHz, 2 or 1.5 Mbit/s (non traffic) timing
outputs
Issue 05/01 Slide 1.55 http://www.oscilloquartz.com Oscilloquartz SA
Interworking between SDH NE and SASE
Interworking between SDH NE and SASE
SDH NESDH NE
cleanedcleanedtraffic traffic &&timingtiming
outputsoutputs
SASESASE
noisy noisy traffic traffic &&timingtiminginputinput
ExternalExternaltimingtiminginputinput
ExternalExternaltiming timing outputoutput
Issue 05/01 Slide 1.56 http://www.oscilloquartz.com Oscilloquartz SA
SEC PerformanceSEC Performance
• Type• Application
FrequencyAccuracy
Holdover frequencydeparture Bandwith
Option 12048 kbit/s based 4.6E-6 5E-8 + t x 1E-8 / day 1 .. 10 Hz
Option 21544 kbit/s based 20E-6 5E-8 + t x 5E-7 / day 0.1 Hz
Issue 05/01 Slide 1.57 http://www.oscilloquartz.com Oscilloquartz SA
SDH synchronisation link connectionsSDH synchronisation link connections
»Supported by an SDH multiplex section trail
» i.e. the timing information is carried by theSTM-N data rate ( N x 155 Mbits/s)
»SDH regenerator timing generators are not counted as elements of the synchronisation distribution layer, they belong to thesynchronisation link connection
»Supported by an SDH multiplex section trail
» i.e. the timing information is carried by theSTM-N data rate ( N x 155 Mbits/s)
»SDH regenerator timing generators are not counted as elements of the synchronisation distribution layer, they belong to thesynchronisation link connection
Issue 05/01 Slide 1.58 http://www.oscilloquartz.com Oscilloquartz SA
2. Architecture2. Architecture
Issue 05/01 Slide 1.59 http://www.oscilloquartz.com Oscilloquartz SA
2.1. Inter-Node Distribution Architecture
2.1. Inter-Node Distribution Architecture
Issue 05/01 Slide 1.60 http://www.oscilloquartz.com Oscilloquartz SA
Master-slave principleMaster-slave principle
»A designated master clock is used as a reference frequency generator.
»The frequency generated by the master clock is disseminated to all other clocks which are slaved to the master clock.
»A designated master clock is used as a reference frequency generator.
»The frequency generated by the master clock is disseminated to all other clocks which are slaved to the master clock.
Issue 05/01 Slide 1.61 http://www.oscilloquartz.com Oscilloquartz SA
Master-slave principleMaster-slave principle
PRC
SEC
SSU
SEC
SSU
SSU SSU SSU
SEC
SEC
SEC
SEC
SEC
SEC
SEC
SEC
SEC
SEC
= master
= slave
= slave
= slave
= slave
= slave
= slave
Issue 05/01 Slide 1.62 http://www.oscilloquartz.com Oscilloquartz SA
Principle of trail redundancyPrinciple of trail redundancy
»Each slave clock should get at least two reference signals form the master clock via geographically separate trails.
»Sometimes it is not possible to fulfill this principle for all nodes of the network (depending on connectivity).
»Each slave clock should get at least two reference signals form the master clock via geographically separate trails.
»Sometimes it is not possible to fulfill this principle for all nodes of the network (depending on connectivity).
Issue 05/01 Slide 1.63 http://www.oscilloquartz.com Oscilloquartz SA
Hierachy of clock quality levelsHierachy of clock quality levels
»There is a hierarchy of clock quality levels:
»The higher the clock quality level, the higher the frequency accuracy of the clock
»Frequency accuracy: either overall free-run accuracy or holdover accuracy over a limited time period
»There is a hierarchy of clock quality levels:
»The higher the clock quality level, the higher the frequency accuracy of the clock
»Frequency accuracy: either overall free-run accuracy or holdover accuracy over a limited time period
Issue 05/01 Slide 1.64 http://www.oscilloquartz.com Oscilloquartz SA
Clock quality levelsClock quality levels
2048 kbit/s based:
PRC: 1E-11
SSU I: 2E-10/d
SEC 1: 4.6E-6
2048 kbit/s based:
PRC: 1E-11
SSU I: 2E-10/d
SEC 1: 4.6E-6
1544 kbit/s based:
PRC: 1E-11
SSU II: 1.6E-8/1 yr
SSU III/IV: 4.6E-6
SEC 2: 20E-6
1544 kbit/s based:
PRC: 1E-11
SSU II: 1.6E-8/1 yr
SSU III/IV: 4.6E-6
SEC 2: 20E-6
Issue 05/01 Slide 1.65 http://www.oscilloquartz.com Oscilloquartz SA
Hierarchical distribution ruleHierarchical distribution rule
»A clock of a given quality level must always (also under failure conditions) take timing (directly or indirectly) from a source clock with the same or higher quality level.
»A clock of a given quality level must always (also under failure conditions) take timing (directly or indirectly) from a source clock with the same or higher quality level.
Issue 05/01 Slide 1.66 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation network with SSMSynchronisation network with SSM
PRC
SEC
SSU
SEC
SSU
SSU SSU SSU
SEC
SEC
SEC
SEC
SEC
SEC
SEC
SEC
Link failure!
Holdover mode!
SEC
SEC
Issue 05/01 Slide 1.67 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation network with SSMSynchronisation network with SSM
»Link failure within a chain of SECs!
»SSM signaling prevents the downstream SSU form following a SEC in holdover mode.
» Instead, the first SSU enters holdover mode and becomes the source clock for the cut off sub-network.
»Link failure within a chain of SECs!
»SSM signaling prevents the downstream SSU form following a SEC in holdover mode.
» Instead, the first SSU enters holdover mode and becomes the source clock for the cut off sub-network.
Issue 05/01 Slide 1.68 http://www.oscilloquartz.com Oscilloquartz SA
The control of jitter and wanderThe control of jitter and wander
»SDH requires that jitter and wander be kept below tight network limits.
»This is achieved by inserting narrow-bandwith SSUs in the synchronisation chain (SEC bandiwth is relatively wide).
»Narrow-bandwith SSUs attenuate jitter and wander components that lie outside theSSU bandwith.
»SDH requires that jitter and wander be kept below tight network limits.
»This is achieved by inserting narrow-bandwith SSUs in the synchronisation chain (SEC bandiwth is relatively wide).
»Narrow-bandwith SSUs attenuate jitter and wander components that lie outside theSSU bandwith.
Issue 05/01 Slide 1.69 http://www.oscilloquartz.com Oscilloquartz SA
SDH Synchronisation reference chain
SDH Synchronisation reference chain
PRC
SSU
SEC
SEC
SSU
SEC
SEC
SEC
SEC
max. 20 SEC
max. 20 SEC
max. 20 SEC
max. 10 x
max. 60 SEC
Issue 05/01 Slide 1.70 http://www.oscilloquartz.com Oscilloquartz SA
SDH synchronisation reference chain
SDH synchronisation reference chain
»For SDH (not SONET!) see ITU-T G.803 or ETSI EN 300 462-2
»The ITU-T/ETSI synchronisation reference chain meets the network limits on jitter andwander:»Not more than 60 SECs in a chain»Not more than 20 SECs between two SSUs»Not more than 10 SSUs in the chain
»For SDH (not SONET!) see ITU-T G.803 or ETSI EN 300 462-2
»The ITU-T/ETSI synchronisation reference chain meets the network limits on jitter andwander:»Not more than 60 SECs in a chain»Not more than 20 SECs between two SSUs»Not more than 10 SSUs in the chain
Issue 05/01 Slide 1.71 http://www.oscilloquartz.com Oscilloquartz SA
Summary - 1Summary - 1
SDH/SONET Network
SDH/SONET NE
SDH/SONET NE
PSTN Switch
SSU/SASE
PRC
Ext. timing signal
Ext. timing signal
Ext. timing signal
Synchronisationcarried bySTM-N signals
Issue 05/01 Slide 1.72 http://www.oscilloquartz.com Oscilloquartz SA
2.2. Intra-Node Distribution Architecture
2.2. Intra-Node Distribution Architecture
Issue 05/01 Slide 1.73 http://www.oscilloquartz.com Oscilloquartz SA
Intra-node star topologyIntra-node star topology
Node boundary
Primary PRC SD trail
PRC SD trail to other nodes PRC SD trail to other nodes
SEC SEC
SSU
Secondary PRC SD trail
SEC SDH equipmentclock
Other equipmentclock
Issue 05/01 Slide 1.74 http://www.oscilloquartz.com Oscilloquartz SA
Interworking between SDH NE, SASE, and other equipment
Interworking between SDH NE, SASE, and other equipment
SDH NEcleanedtraffic &timing
outputs
SASE
noisy traffic &timinginput
External timinginput
External timing output
e.g. Switch
Issue 05/01 Slide 1.75 http://www.oscilloquartz.com Oscilloquartz SA
3. Synchronisation Status Message (SSM)
3. Synchronisation Status Message (SSM)
Issue 05/01 Slide 1.76 http://www.oscilloquartz.com Oscilloquartz SA
Functions of the SSM signaling layerFunctions of the SSM signaling layer
Signal the source clock quality level from clock to clock down the synchronisation chains, in order to
»enable clocks to select the best available reference timing signal
»enable clocks to go into holdover mode if reference timing signals are of low quality
»prevent timig loops in SDH chains and rings
Signal the source clock quality level from clock to clock down the synchronisation chains, in order to
»enable clocks to select the best available reference timing signal
»enable clocks to go into holdover mode if reference timing signals are of low quality
»prevent timig loops in SDH chains and rings
Issue 05/01 Slide 1.77 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation Status MessagesSynchronisation Status Messages
¼The clock source quality level is indicated by the Synchronisation Status Message (SSM):¼QL-PRC = Primary Reference Clock
¼QL-SSU-T = SSU Transit Node Clock
¼QL-SSU-L = SSU Local Node Clock
¼QL-SEC = SDH Equipment Clock
¼QL-DNU = Do not use
¼The clock source quality level is indicated by the Synchronisation Status Message (SSM):¼QL-PRC = Primary Reference Clock
¼QL-SSU-T = SSU Transit Node Clock
¼QL-SSU-L = SSU Local Node Clock
¼QL-SEC = SDH Equipment Clock
¼QL-DNU = Do not use
Issue 05/01 Slide 1.78 http://www.oscilloquartz.com Oscilloquartz SA
Transmission Channels for the SSMTransmission Channels for the SSM
¼ The timing quality level carried by STM-N signals is indicated by S1 byte in the STM-N Multiplex Section Over Head (MSOH)
¼ The timing quality level carried over 2048 kbit/s synchronisation signals is indicated in one of the bits Sa4 to Sa8 in Time Slot Zero (TS0).
¼ OC-N signals (SONET): Multiplex SectionOverhead
¼ 1544 kbit/s T1 signals: see ITU-T Rec. G.704
¼ The timing quality level carried by STM-N signals is indicated by S1 byte in the STM-N Multiplex Section Over Head (MSOH)
¼ The timing quality level carried over 2048 kbit/s synchronisation signals is indicated in one of the bits Sa4 to Sa8 in Time Slot Zero (TS0).
¼ OC-N signals (SONET): Multiplex SectionOverhead
¼ 1544 kbit/s T1 signals: see ITU-T Rec. G.704
Issue 05/01 Slide 1.79 http://www.oscilloquartz.com Oscilloquartz SA
SSM-based reference selectionSSM-based reference selection
¿ Always select the timing input with the highest QL, and if a number of equal QL timing inputs areavailable, then select the highest priority timing input
» In the locked mode, the output SSMs are set to the selected input SSM, e.g. QL-PRC in => QL-PRC out
À The SSM in the return signal of the selected inputis automatically set to DNU
¿ Always select the timing input with the highest QL, and if a number of equal QL timing inputs areavailable, then select the highest priority timing input
» In the locked mode, the output SSMs are set to the selected input SSM, e.g. QL-PRC in => QL-PRC out
À The SSM in the return signal of the selected inputis automatically set to DNU
Issue 05/01 Slide 1.80 http://www.oscilloquartz.com Oscilloquartz SA
If all the timing inputs are badIf all the timing inputs are bad
À The SEC enters hold-over mode:À it remembers the phase and frequency values
of the previously good input, but drifts towardsy = 4.6 x 10-6 (4.6ppm)
À STM-N outputs get SSM = QL-SEC
À 2 MHz ext. timing outputs are squelched (cut off)
À 2 Mbit/s ext. timing outputs get SSM = QL-SEC or AIS = true
À The SEC enters hold-over mode:À it remembers the phase and frequency values
of the previously good input, but drifts towardsy = 4.6 x 10-6 (4.6ppm)
À STM-N outputs get SSM = QL-SEC
À 2 MHz ext. timing outputs are squelched (cut off)
À 2 Mbit/s ext. timing outputs get SSM = QL-SEC or AIS = true
Issue 05/01 Slide 1.81 http://www.oscilloquartz.com Oscilloquartz SA
Ring synchronisation with SSM: normal condition
Ring synchronisation with SSM: normal condition
PrimaryPrimary PRCPRC
SSM =QLSSM =QL--PRCPRC
QLQL--PRCPRC
SSM = QLSSM = QL--PRCPRC
SSM = QLSSM = QL--DNUDNU
QLQL--DNUDNU
SSM = QLSSM = QL--DNUDNU
1111
1111
22
SecondarySecondary PRCPRC
22
SSM = QLSSM = QL--PRCPRCSSM = QLSSM = QL--PRCPRC
22
QLQL--PRCPRC QLQL--PRCPRC
22
Issue 05/01 Slide 1.82 http://www.oscilloquartz.com Oscilloquartz SA
Ring synchronisation with SSMprimary PRC section failure
Ring synchronisation with SSMprimary PRC section failure
PrimaryPrimary PRCPRC
SSM = QLSSM = QL--DNUDNU
QLQL--PRCPRC
SSM = QLSSM = QL--PRCPRC
SSM = QLSSM = QL--PRCPRC
QLQL--DNUDNU
SSM = QLSSM = QL--DNUDNU
1111
1111
22
SecondarySecondary PRCPRC
22SSM = QLSSM = QL--PRCPRC
22
QLQL--PRCPRC QLQL--PRCPRC
22
input 1 = LOSinput 1 = LOS detecteddetectedinput 2 = QLinput 2 = QL--PRC PRC detecteddetectedSECSEC selectsselects input 2input 2
SECSEC selectsselects input 3input 3
Issue 05/01 Slide 1.83 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation Distribution:
GPS-Based and MixedSolutions
Synchronisation Distribution:
GPS-Based and MixedSolutions
Issue 05/01 Slide 1.84 http://www.oscilloquartz.com Oscilloquartz SA
The Global Positioning System (GPS)The Global Positioning System (GPS)
Issue 05/01 Slide 1.85 http://www.oscilloquartz.com Oscilloquartz SA
The Global Positioning System (GPS)The Global Positioning System (GPS)
» It ’s a global navigation satellite system owned by the US DoD.
»24 satellites broadcast time and their positions (orbits).
»Based on signals from four or more satellites, GPS receivers calculate their position and time.
»Synchronization signals can be derived from that time information.
» It ’s a global navigation satellite system owned by the US DoD.
»24 satellites broadcast time and their positions (orbits).
»Based on signals from four or more satellites, GPS receivers calculate their position and time.
»Synchronization signals can be derived from that time information.
Issue 05/01 Slide 1.86 http://www.oscilloquartz.com Oscilloquartz SA
The Global Positioning System (GPS)The Global Positioning System (GPS)
»Orbit and time information that is broadcast on civilian satellite signals can be degraded during times of war (« Selected Availability - S/A»).
»Frequency accuracy of GPS receivers is typically better than 1·10-12 over 24 hours.
»Time error is typically better than 150 ns (when degraded by S/A).
»Orbit and time information that is broadcast on civilian satellite signals can be degraded during times of war (« Selected Availability - S/A»).
»Frequency accuracy of GPS receivers is typically better than 1·10-12 over 24 hours.
»Time error is typically better than 150 ns (when degraded by S/A).
Issue 05/01 Slide 1.87 http://www.oscilloquartz.com Oscilloquartz SA
The Global Positioning System (GPS)The Global Positioning System (GPS)
»S/A degradation on timing can be (at least partially) removed by appropriate filteringtechniques.
»Good GPS receivers (good S/A filtering!)comply with the PRC specification of ITU-T Rec. G.811.
»GPS reception is subject to interferenceand can be jammed intentionally.
»S/A degradation on timing can be (at least partially) removed by appropriate filteringtechniques.
»Good GPS receivers (good S/A filtering!)comply with the PRC specification of ITU-T Rec. G.811.
»GPS reception is subject to interferenceand can be jammed intentionally.
Issue 05/01 Slide 1.88 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation distribution architecturesbased on the GPS
Synchronisation distribution architecturesbased on the GPS
1) Master-slave distribution tree plus GPS-receivers in important nodes
2) « Cellular synchronisation distribution »
1) Master-slave distribution tree plus GPS-receivers in important nodes
2) « Cellular synchronisation distribution »
Issue 05/01 Slide 1.89 http://www.oscilloquartz.com Oscilloquartz SA
Network example used for the comparisonNetwork example used for the comparison
= SDH node= Multiplex section
Issue 05/01 Slide 1.90 http://www.oscilloquartz.com Oscilloquartz SA
Master-slave tree plus GPS-receivers in important nodes
Master-slave tree plus GPS-receivers in important nodes
M = Master PRC
S = SSU/SASE
G =GPS-based PRCS
G
G GG
SM
SSS
S
Issue 05/01 Slide 1.91 http://www.oscilloquartz.com Oscilloquartz SA
»Conventionnel master-slave distribution tree with a central PRC and SSU/SASEs»GPS-receivers as back-up reference
sources in nodes equiped with SSU/SASEs
»Conventionnel master-slave distribution tree with a central PRC and SSU/SASEs»GPS-receivers as back-up reference
sources in nodes equiped with SSU/SASEs
Master-slave tree plus GPS-receivers in important nodes
Master-slave tree plus GPS-receivers in important nodes
Issue 05/01 Slide 1.92 http://www.oscilloquartz.com Oscilloquartz SA
»Redundancy is provided by the GPS»Therefore master-slave tree need not
necessariliy provide redundant synchronisation distribution, thus simplifying network design»Easier to modify (network evolution) than
with redundant master-slave tree
»Redundancy is provided by the GPS»Therefore master-slave tree need not
necessariliy provide redundant synchronisation distribution, thus simplifying network design»Easier to modify (network evolution) than
with redundant master-slave tree
Master-slave tree plus GPS-receivers in important nodes
Master-slave tree plus GPS-receivers in important nodes
Issue 05/01 Slide 1.93 http://www.oscilloquartz.com Oscilloquartz SA
»Lower risk of creating timing loops than with redundant master-slave tree»Equipment cost somewhat higher than
with redundant master-slave tree (additional GPS-receivers): that ’s the price to pay for all the advantages
»Lower risk of creating timing loops than with redundant master-slave tree»Equipment cost somewhat higher than
with redundant master-slave tree (additional GPS-receivers): that ’s the price to pay for all the advantages
Master-slave tree plus GPS-receivers in important nodes
Master-slave tree plus GPS-receivers in important nodes
Issue 05/01 Slide 1.94 http://www.oscilloquartz.com Oscilloquartz SA
« Cellular synchronisation distribution »« Cellular synchronisation distribution »
G = GPS-based PRC
GG
G G
G G
Issue 05/01 Slide 1.95 http://www.oscilloquartz.com Oscilloquartz SA
GPS GPS
1 1 1 1
2 2
2
2
« Cellular synchronisation distribution »:Cell pattern A
« Cellular synchronisation distribution »:Cell pattern A
Issue 05/01 Slide 1.96 http://www.oscilloquartz.com Oscilloquartz SA
GPS GPS
1 1 1 1
2 2
2
2
« Cellular synchronisation distribution »:Failure of a GPS-receiver
« Cellular synchronisation distribution »:Failure of a GPS-receiver
Issue 05/01 Slide 1.97 http://www.oscilloquartz.com Oscilloquartz SA
GPS GPS
1 1 1 1
2 2
2
2
« Cellular synchronisation distribution »:Link failure
« Cellular synchronisation distribution »:Link failure
Issue 05/01 Slide 1.98 http://www.oscilloquartz.com Oscilloquartz SA
1 1 1 1
2 2
2
2
« Cellular synchronisation distribution »:Cell pattern B
« Cellular synchronisation distribution »:Cell pattern B
Issue 05/01 Slide 1.99 http://www.oscilloquartz.com Oscilloquartz SA
»Each of the two synchronization inputs of a B-cell must be connected to a different synchronization output of an A-cell
»An A-cell ’s synchronization output may be connected to one or many synchronization inputs of B-cells
»Each of the two synchronization inputs of a B-cell must be connected to a different synchronization output of an A-cell
»An A-cell ’s synchronization output may be connected to one or many synchronization inputs of B-cells
« Cellular synchronisation distribution »:Interconnection rules
« Cellular synchronisation distribution »:Interconnection rules
Issue 05/01 Slide 1.100 http://www.oscilloquartz.com Oscilloquartz SA
« Cellular synchronisation distribution »« Cellular synchronisation distribution »
G = GPS-based PRC
GG
G G
G G
B BB
B BA
A
A
Issue 05/01 Slide 1.101 http://www.oscilloquartz.com Oscilloquartz SA
»All nodes get two reference signals coming from two GPS receivers located in different sites via geographically separate routes
»Protection against failures of links, clocks and GPS-receivers (including local corruption of the GPS radio signal)
»All nodes get two reference signals coming from two GPS receivers located in different sites via geographically separate routes
»Protection against failures of links, clocks and GPS-receivers (including local corruption of the GPS radio signal)
« Cellular synchronisation distribution »:Protection against failures
« Cellular synchronisation distribution »:Protection against failures
Issue 05/01 Slide 1.102 http://www.oscilloquartz.com Oscilloquartz SA
»Cells cannot be looped since A-cells only deliver synchronization, and B-cells only receive synchronization
»Cells are protected against timing loop formation by the SSM protocol
»Cells cannot be looped since A-cells only deliver synchronization, and B-cells only receive synchronization
»Cells are protected against timing loop formation by the SSM protocol
« Cellular synchronisation distribution »:Timing loop prevention
« Cellular synchronisation distribution »:Timing loop prevention
Issue 05/01 Slide 1.103 http://www.oscilloquartz.com Oscilloquartz SA
»Simple internal cell structure
»Simple interconnection rules
»Network can be expanded easily by»Adding new cells»Increasing cell length»Spitting a cell into several smaller cells
»Simple internal cell structure
»Simple interconnection rules
»Network can be expanded easily by»Adding new cells»Increasing cell length»Spitting a cell into several smaller cells
« Cellular synchronisation distribution »:Simple and scaleable network design
« Cellular synchronisation distribution »:Simple and scaleable network design
Issue 05/01 Slide 1.104 http://www.oscilloquartz.com Oscilloquartz SA
SummarySummary
»The GPS provides a synchronisation source compliant to ITU-T Rec. G.811
»Architectures must provide protection against failure of the GPS radio signal, e.g.:»Master-slave tree plus GPS-receivers in
important nodes»« Cellular synchronisation distribution »
»The GPS provides a synchronisation source compliant to ITU-T Rec. G.811
»Architectures must provide protection against failure of the GPS radio signal, e.g.:»Master-slave tree plus GPS-receivers in
important nodes»« Cellular synchronisation distribution »
Issue 05/01 Slide 1.105 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation Distribution:
From Co-operating Network
Synchronisation Distribution:
From Co-operating Network
Issue 05/01 Slide 1.106 http://www.oscilloquartz.com Oscilloquartz SA
Taking synchronisation from a co-operating network
Taking synchronisation from a co-operating network
»There is no PRC in the network»All clocks in the network are slaved to
synchronization signals from a co-operating network.»Under normal operating conditions all slave
clocks operate at the same frequency asthe PRC in the co-operating network.»There are normally no slip for on-net and
off-net traffic to the co-operating network.
»There is no PRC in the network»All clocks in the network are slaved to
synchronization signals from a co-operating network.»Under normal operating conditions all slave
clocks operate at the same frequency asthe PRC in the co-operating network.»There are normally no slip for on-net and
off-net traffic to the co-operating network.
Issue 05/01 Slide 1.107 http://www.oscilloquartz.com Oscilloquartz SA
»The clock signals from the co-operating network may be received at only a fewsynchronisation gateway nodes.»The clock signals from the co-operating
network may also be received at every node, or at every sub-network.
»The clock signals from the co-operating network may be received at only a fewsynchronisation gateway nodes.»The clock signals from the co-operating
network may also be received at every node, or at every sub-network.
Taking synchronisation from aco-operating network
Taking synchronisation from aco-operating network
Issue 05/01 Slide 1.108 http://www.oscilloquartz.com Oscilloquartz SA
PRCPRC
nn nn nn nn nn
nn nn nn nn
nn nn nn nn
COCO--OPERATING NETWORKOPERATING NETWORK
Taking synchronisation from aco-operating network
Taking synchronisation from aco-operating network
Issue 05/01 Slide 1.109 http://www.oscilloquartz.com Oscilloquartz SA
COCO--OPERATING NETWORKOPERATING NETWORK
PRCPRC
nn nn nn
nn nn nn
nn nn nn
nn nn
nn
nn
Taking synchronisation from aco-operating network
Taking synchronisation from aco-operating network
Issue 05/01 Slide 1.110 http://www.oscilloquartz.com Oscilloquartz SA
COCO--OPERATINGOPERATINGNETWORKNETWORK
PRCPRC
nn
nn
nn
nn
nn nn
nn
nn
nn
nn nn
nn nn
Taking synchronisation from aco-operating network
Taking synchronisation from aco-operating network
Issue 05/01 Slide 1.111 http://www.oscilloquartz.com Oscilloquartz SA
»The network’s synchronisation performance is dependent on the qualityof the synchronisation signals from the co-operating network.»There must be an agreement with the co-
operating operator on service level»The cost to lease the synchronisation
signals can be high.
»The network’s synchronisation performance is dependent on the qualityof the synchronisation signals from the co-operating network.»There must be an agreement with the co-
operating operator on service level»The cost to lease the synchronisation
signals can be high.
Critical issuesCritical issues
Issue 05/01 Slide 1.112 http://www.oscilloquartz.com Oscilloquartz SA
Agreement on synchronization interfaces
Agreement on synchronization interfaces
»Physical interface specification (e.g. 2 Mbit/s, G.703)»SSM configuration»Guaranteed synchronization quality (e.g.
G.823 Network Limit)»Upstream synchronisation chain length
(number of clocks)»Guaranteed availability of agreed quality
(e.g. 0.9999)
»Physical interface specification (e.g. 2 Mbit/s, G.703)»SSM configuration»Guaranteed synchronization quality (e.g.
G.823 Network Limit)»Upstream synchronisation chain length
(number of clocks)»Guaranteed availability of agreed quality
(e.g. 0.9999)
Issue 05/01 Slide 1.113 http://www.oscilloquartz.com Oscilloquartz SA
Agreement onsynchronization interfaces
Agreement onsynchronization interfaces
»Mean Time to Repair in case of failure»Worst case quality degradation in case of
failure (e.g. max. frequency error, max. frequency drift, max. jitter & wander)»Alarming method in case of failure (e.g.
SSM) »Quality monitoring criteria
»Mean Time to Repair in case of failure»Worst case quality degradation in case of
failure (e.g. max. frequency error, max. frequency drift, max. jitter & wander)»Alarming method in case of failure (e.g.
SSM) »Quality monitoring criteria
Issue 05/01 Slide 1.114 http://www.oscilloquartz.com Oscilloquartz SA
Summary onStandards
Summary onStandards
Issue 05/01 Slide 1.115 http://www.oscilloquartz.com Oscilloquartz SA
Standardisation BodiesStandardisation Bodies
International level : ITU Recommendations
Regional level, Europe: ETSI Legaly binding standards
USA: ANSI Legaly binding standards
Industry level: e.g. TIA Industry standards
Company level: e.g. Bellcore Internal standards
International level : ITU Recommendations
Regional level, Europe: ETSI Legaly binding standards
USA: ANSI Legaly binding standards
Industry level: e.g. TIA Industry standards
Company level: e.g. Bellcore Internal standards
ITU : International Telecommunication UnionETSI : European Telecommunications Standards InstituteANSI : American National Standards InstituteTIA: Telecommunication Industry Association
Issue 05/01 Slide 1.116 http://www.oscilloquartz.com Oscilloquartz SA
ITU-T Rec. concerning synch.ITU-T Rec. concerning synch.
» G.703 Electrical characteristics of digital interfaces
» G.781 Synchronisation layer function of SDH NEs
» G.783 SDH equipment functional blocks
» G.803 Architecture of SDH transport networks
» G.810 Definitions and terminology
» G.811 Specification for PRCs
» G.812 Specification for SSUs
» G.703 Electrical characteristics of digital interfaces
» G.781 Synchronisation layer function of SDH NEs
» G.783 SDH equipment functional blocks
» G.803 Architecture of SDH transport networks
» G.810 Definitions and terminology
» G.811 Specification for PRCs
» G.812 Specification for SSUs
Issue 05/01 Slide 1.117 http://www.oscilloquartz.com Oscilloquartz SA
ITU-T Rec. concerning synch.ITU-T Rec. concerning synch.
» G.813 Specification for SECs
» G.823 Jitter and wander control in 2048 kbit/s-based PDH networks (incl. synch. interfaces)
» G.824 Jitter and wander control in 1544 kbit/s-based PDH networks (incl. synch. interfaces)
» G.825 Jitter and wander control in SDH networks
» G.8251 Jitter and wander control in the OTN
» G.813 Specification for SECs
» G.823 Jitter and wander control in 2048 kbit/s-based PDH networks (incl. synch. interfaces)
» G.824 Jitter and wander control in 1544 kbit/s-based PDH networks (incl. synch. interfaces)
» G.825 Jitter and wander control in SDH networks
» G.8251 Jitter and wander control in the OTN
Issue 05/01 Slide 1.118 http://www.oscilloquartz.com Oscilloquartz SA
Cross-Reference TableCross-Reference Table
Definitions Network Clocks
Architecture NetworkLimits
SSM PRC SSU/BITS SEC
ITU-T G.810 G.803 PDH:G.823G.824
G.704G.832
G.811 G.812 G.813G.781
SDH:G.825
ETSI ETS 300 462-1 ETS 300 462-2 sync.:ETS 300 462-3
ETS 417-6-1ETS 300 147
ETS 300 462-6 ETS 300 462-4 ETS 300 462-5ETS 417-6-1
non sync.:ETS 302 084
ANSI T1.101 T1.101 T1.101T1.105.03
T1.105.09
Telcordia GR-436-CORE(1)
GR-253-COREGR-499-COREGR-253-CORE
GR-253-CORE GR-2830-CORE GR-378-COREGR-1244-CORE
GR-253-CORE
Note (1): Synchronisation Planning
Issue 05/01 Slide 1.119 http://www.oscilloquartz.com Oscilloquartz SA
How to Synchronize Mixed Technology Networks
How to Synchronize Mixed Technology Networks
Issue 05/01 Slide 1.120 http://www.oscilloquartz.com Oscilloquartz SA
1. Mixed Technology Network Example
1. Mixed Technology Network Example
Issue 05/01 Slide 1.121 http://www.oscilloquartz.com Oscilloquartz SA
Core Network LayersCore Network Layers
SDH or SONET
OTN
IP64 kbit/s
E1 or DS1 ATM
ATMAdaption
layer
MPLS
Issue 05/01 Slide 1.122 http://www.oscilloquartz.com Oscilloquartz SA
Access Network LayersAccess Network Layers
IP
UMTS-FDD RAN ISDN xDSL Ethernet
Compressed Voice
64 kbit/s Voice
IP
Wireless access network Wired access network
Issue 05/01 Slide 1.123 http://www.oscilloquartz.com Oscilloquartz SA
Symbols and TerminolgySymbols and Terminolgy
PSTN switch
IP Router
IP Label Switching Router
ATM Switch
PSTN switch
IP Router
IP Label Switching Router
ATM SwitchATM
PSTN
IP LSR
IP
Issue 05/01 Slide 1.124 http://www.oscilloquartz.com Oscilloquartz SA
Symbols and TerminolgySymbols and Terminolgy
UMTS Base Station
UMTS Radio Network Controller
Mobile Switching Center
Mobile Packet Router
UMTS Base Station
UMTS Radio Network Controller
Mobile Switching Center
Mobile Packet RouterMPR
MSC
RNC
C
BS
Issue 05/01 Slide 1.125 http://www.oscilloquartz.com Oscilloquartz SA
Symbols and TerminolgySymbols and Terminolgy
SDH/SONET Add-Drop-Multiplexer
SDH/SONET Crossconnect
Wavelength Add-Drop-Multiplexer
Wavelength Crossconnect
SDH/SONET Add-Drop-Multiplexer
SDH/SONET Crossconnect
Wavelength Add-Drop-Multiplexer
Wavelength CrossconnectOTN
OTN
SDH
SDH
Issue 05/01 Slide 1.126 http://www.oscilloquartz.com Oscilloquartz SA
Core Network LayersCore Network Layers
S
P
S
P
SS
M
O
S
O
IP
A
O
IP
A
O
IP
A
ATM
SDH/SONET
OTN
IP/PSTN
O
O
S
Issue 05/01 Slide 1.127 http://www.oscilloquartz.com Oscilloquartz SA
Wired Access NetworkWired Access Network
PSTN
Modem
DSLAM
Ethernet LAN
xDSL
E1 or DS1
64 kbit/s Voice
PBX
Core Network
ATM
IP
ATM
IP
Issue 05/01 Slide 1.128 http://www.oscilloquartz.com Oscilloquartz SA
ATM
Wireless Access NetworkWireless Access Network
BS
BS
S S
MSC
MPR
RNC
C
S
PSTN
IP Network
SDH/SONET
N x E1/DS1
N x E1/DS1
Issue 05/01 Slide 1.129 http://www.oscilloquartz.com Oscilloquartz SA
2. SDH and SONET Networks2. SDH and SONET Networks
Issue 05/01 Slide 1.130 http://www.oscilloquartz.com Oscilloquartz SA
Synchronization requirementsSynchronization requirements
»Frequency synchronization
»Frequency accuracy:»Normal operation: 1E-11»Failure conditions: 4.6E-6 (SDH Eqmt. Clock)
2E-5 (SONET Minimum Clock)
»Jitter and Wander:»ITU-T G.825 (Network Limits)»ANSI T1.101, § 7.2 and 7.3 (MTIE, TDEV, phase
transients)
»Frequency synchronization
»Frequency accuracy:»Normal operation: 1E-11»Failure conditions: 4.6E-6 (SDH Eqmt. Clock)
2E-5 (SONET Minimum Clock)
»Jitter and Wander:»ITU-T G.825 (Network Limits)»ANSI T1.101, § 7.2 and 7.3 (MTIE, TDEV, phase
transients)
Issue 05/01 Slide 1.131 http://www.oscilloquartz.com Oscilloquartz SA
Synchronization distribution architecture
Synchronization distribution architecture
»Tree of slave clocks locked to a master clock(master-slave distribution)
» Independent synchronization islands synchronized by GPS-receivers or other local PRCs
»A combination of master-slave distribution and local PRCs in important nodes
»Tree of slave clocks locked to a master clock(master-slave distribution)
» Independent synchronization islands synchronized by GPS-receivers or other local PRCs
»A combination of master-slave distribution and local PRCs in important nodes
Issue 05/01 Slide 1.132 http://www.oscilloquartz.com Oscilloquartz SA
Synchronization issuesSynchronization issues
»Jitter and wander levels more critical than frequency accuracy (therefore need for low-bandwith slave clocks in master-slave networks).
»Establishment and maintenace of a network plan with trail redundancy
»Avoiding timing loops
»Jitter and wander levels more critical than frequency accuracy (therefore need for low-bandwith slave clocks in master-slave networks).
»Establishment and maintenace of a network plan with trail redundancy
»Avoiding timing loops
Issue 05/01 Slide 1.133 http://www.oscilloquartz.com Oscilloquartz SA
3. The Public Switched Telephone Network
3. The Public Switched Telephone Network
Issue 05/01 Slide 1.134 http://www.oscilloquartz.com Oscilloquartz SA
Synchronization requirementsSynchronization requirements
»Frequency synchronization
»Frequency accuracy:»Normal operation: 1E-11»Failure conditions: depends on clock level or
stratum
»Jitter and Wander:»ITU-T Rec. G.823 & G.824 (Network Limits)»ANSI T1.101, § 7.2 (MTIE, TDEV, phase
transients)
»Frequency synchronization
»Frequency accuracy:»Normal operation: 1E-11»Failure conditions: depends on clock level or
stratum
»Jitter and Wander:»ITU-T Rec. G.823 & G.824 (Network Limits)»ANSI T1.101, § 7.2 (MTIE, TDEV, phase
transients)
Issue 05/01 Slide 1.135 http://www.oscilloquartz.com Oscilloquartz SA
Synchronization distribution architecture
Synchronization distribution architecture
» Synchronization distribution based on PDH transport network (E1 or DS1 signals as synchronization carriers).
» Synchronization distribution based on SDH/SONET transport network (STM-n or OC-n signals as synchronization carriers).
» Synchronization distribution based on the GPS
» Mixed solutions
» Synchronization distribution based on PDH transport network (E1 or DS1 signals as synchronization carriers).
» Synchronization distribution based on SDH/SONET transport network (STM-n or OC-n signals as synchronization carriers).
» Synchronization distribution based on the GPS
» Mixed solutions
Issue 05/01 Slide 1.136 http://www.oscilloquartz.com Oscilloquartz SA
Synchronization issuesSynchronization issues
»Frequency accuracy more critical than jitter and wander levels (therefore need for clocks with good holdover stability).
»The SDH/SONET network is not transparent for timing of E1 and DS1 signals (wander induced by SDH/SONET pointer adjustments).
»Frequency accuracy more critical than jitter and wander levels (therefore need for clocks with good holdover stability).
»The SDH/SONET network is not transparent for timing of E1 and DS1 signals (wander induced by SDH/SONET pointer adjustments).
Issue 05/01 Slide 1.137 http://www.oscilloquartz.com Oscilloquartz SA
4. ATM Networks4. ATM Networks
Issue 05/01 Slide 1.138 http://www.oscilloquartz.com Oscilloquartz SA
Synchronization requirementsSynchronization requirements
»Frequency synchronization
»Frequency accuracy for synchronous physical layer: »Normal operation: 1E-11»Failure conditions: 2E-5
»Frequency accuracy for asynchronous physical layer: »Failure conditions: 2E-5
»Jitter & wander: ITU-T G.825 Network Limits
»Frequency synchronization
»Frequency accuracy for synchronous physical layer: »Normal operation: 1E-11»Failure conditions: 2E-5
»Frequency accuracy for asynchronous physical layer: »Failure conditions: 2E-5
»Jitter & wander: ITU-T G.825 Network Limits
Issue 05/01 Slide 1.139 http://www.oscilloquartz.com Oscilloquartz SA
Synchronization distribution architecture
Synchronization distribution architecture
»Take synchronization from SONET-based synchronization distribution network
»Master-slave distribution tree using ATM traffic signals as synchronization carriers
»Take synchronization from GPS-receivers
»Combinations of the above techniques
»Take synchronization from SONET-based synchronization distribution network
»Master-slave distribution tree using ATM traffic signals as synchronization carriers
»Take synchronization from GPS-receivers
»Combinations of the above techniques
Issue 05/01 Slide 1.140 http://www.oscilloquartz.com Oscilloquartz SA
Synchronization from the SONET networkSynchronization from the SONET network
PRSPRS
ATMATMNENE
ATMATMNENEATMATM
NENE
ATMATMNENE
ATMATMNENE
ClockClock
ClockClock
ClockClock
ClockClock
ClcokClcok
ClockClock
ATMATMNENE
SONET-basedsynch.distribution
ATMnetwork
Issue 05/01 Slide 1.141 http://www.oscilloquartz.com Oscilloquartz SA
Master-slave synchronization distributionMaster-slave synchronization distribution
PRSPRS
ATMATMNENE
ATMATMNENE
ATMATMNENE
ATMATMNENE
ATMATMNENE
ATMATMNENE
ATMnetwork
Issue 05/01 Slide 1.142 http://www.oscilloquartz.com Oscilloquartz SA
GPS-receiversGPS-receivers
ATMnetwork
ATMATMNENE
GPSGPS
ATMATMNENE
GPSGPS
ATMATMNENE
GPSGPS
ATMATMNENE
GPSGPSATMATMNENE
GPSGPS
Issue 05/01 Slide 1.143 http://www.oscilloquartz.com Oscilloquartz SA
Mixed solutionMixed solution
PRSPRS
ATMATMNENE
ATMATMNENE
ATMATMNENE
ATMATMNENE
ATMATMNENE
ClockClock
ATMATMNENE
SONET-basedsynch.distribution
ATMnetwork
GPSGPS
Issue 05/01 Slide 1.144 http://www.oscilloquartz.com Oscilloquartz SA
Synchronization issuesSynchronization issues
»SDH/SONET-based synchronization not always available (e.g. in case of ATM overON)
»How can we achieve protection against reference failures in cases where SDH/SONET-based synchronization is not available?
»SDH/SONET-based synchronization not always available (e.g. in case of ATM overON)
»How can we achieve protection against reference failures in cases where SDH/SONET-based synchronization is not available?
Issue 05/01 Slide 1.145 http://www.oscilloquartz.com Oscilloquartz SA
5. Optical Networks5. Optical Networks
Issue 05/01 Slide 1.146 http://www.oscilloquartz.com Oscilloquartz SA
Today’s Optical Networks (ON)Today’s Optical Networks (ON)
»Transmission: optical fibre
»Multiplexing: (Dense) Wavelength Division Multiplexing (WDM, DWDM)
»Switching: circuit switching, where lightpaths are the circuits
»Control plane:»ASON (Automatically Switched Optical Network)
by ITU-T (G.8080/Y.1304)
»GMPLS (Generalized Multiprotocol Label Switching) by IETF (draft-ietf-mpls-generalized-signaling-07)
»Transmission: optical fibre
»Multiplexing: (Dense) Wavelength Division Multiplexing (WDM, DWDM)
»Switching: circuit switching, where lightpaths are the circuits
»Control plane:»ASON (Automatically Switched Optical Network)
by ITU-T (G.8080/Y.1304)
»GMPLS (Generalized Multiprotocol Label Switching) by IETF (draft-ietf-mpls-generalized-signaling-07)
Issue 05/01 Slide 1.147 http://www.oscilloquartz.com Oscilloquartz SA
Optical Transport NetworksOptical Transport Networks
The remaining slides are about today’s lightpath switched ONs as standardized by
ITU-T; they are called Optical Transport Networks (OTN)
(ITU-T Rec. G.709, G.871/Y.1301, G.872)
The remaining slides are about today’s lightpath switched ONs as standardized by
ITU-T; they are called Optical Transport Networks (OTN)
(ITU-T Rec. G.709, G.871/Y.1301, G.872)
Issue 05/01 Slide 1.148 http://www.oscilloquartz.com Oscilloquartz SA
General OTN FeaturesGeneral OTN Features
»New transport networking layer
»DWDM, each wavelength transports an Optical Channel (Och)
»Lightpath switching
»Data-rate per wavelength:»2.5 Gbit/s or 10 Gbit/s or 40 Gbit/s
»Service transparency for clients
»Asynchronous and bit-synchronous payload mappings
»New transport networking layer
»DWDM, each wavelength transports an Optical Channel (Och)
»Lightpath switching
»Data-rate per wavelength:»2.5 Gbit/s or 10 Gbit/s or 40 Gbit/s
»Service transparency for clients
»Asynchronous and bit-synchronous payload mappings
Issue 05/01 Slide 1.149 http://www.oscilloquartz.com Oscilloquartz SA
OTN Network LayersOTN Network Layers
+OPU/ODU/OTU Overhead
+OMS Overhead
OCh Overhead
Client Information1
+
+OTS/COMMS Overhead
Client InformationN
OC
h la
yer
net
wo
rkO
MS
laye
rn
etw
ork
OT
S la
yer
net
wo
rk
wavelengthN
wavelength1
wavelength0
opticalfibre
......
OCh1
OMU
OTM
OSC
OTU1
OChN
OTUN
Issue 05/01 Slide 1.150 http://www.oscilloquartz.com Oscilloquartz SA
OTN AbbreviationsOTN AbbreviationsOCh Optical Channel
OPU Optical Channel Payload Unit
ODU Optical Channel Data Unit
OTU Optical Channel Transport Unit
OMS Optical Multiplex Section
OMU Optical Multiplex Unit
OTS Optical Transmission Section
OTM Optical Transport Module
OCh Optical Channel
OPU Optical Channel Payload Unit
ODU Optical Channel Data Unit
OTU Optical Channel Transport Unit
OMS Optical Multiplex Section
OMU Optical Multiplex Unit
OTS Optical Transmission Section
OTM Optical Transport Module
Issue 05/01 Slide 1.151 http://www.oscilloquartz.com Oscilloquartz SA
OTN AbbreviationsOTN Abbreviations
OSC Optical Supervisory Channel
COMMS Management Communications
OADM Optical Add-Drop Multiplexer
OXC Optical Cross-Connect
LC Link Connection
REG Regenerator
OSC Optical Supervisory Channel
COMMS Management Communications
OADM Optical Add-Drop Multiplexer
OXC Optical Cross-Connect
LC Link Connection
REG Regenerator
Issue 05/01 Slide 1.152 http://www.oscilloquartz.com Oscilloquartz SA
OTN ArchitectureOTN Architecture
OADM OADMOXCREG REG
Client (e.g. SDH) Link Connection
OCh Link Connection (LC)
OTS LC
OCh Link Connection (LC)
OTS LCOTS LCOTS LC
OMS LC OMS LCOMS LCOMS LC
OChmatrix
Issue 05/01 Slide 1.153 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation IssuesSynchronisation Issues
»The OTN is required to limit jitter and wander accumulation.»Hence there are Network Limit specifications
(ITU-T Rec, G.8251).
»The OTN itself is not required to transportsynchronisation.»No requirement for different optical channels to
by synchronous.
»The OTN is required to limit jitter and wander accumulation.»Hence there are Network Limit specifications
(ITU-T Rec, G.8251).
»The OTN itself is not required to transportsynchronisation.»No requirement for different optical channels to
by synchronous.
Issue 05/01 Slide 1.154 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation IssuesSynchronisation Issues
»The OTN is required to allow the transport of synchronisation via SDH/SONET client connections.»SDH/SONET client connections must meet
G.825 Network Limits after transport over the OTN.»A synchronisation reference chain which meets
G.825 Network Limits is proposed in ITU-T Rec. G.8251.
»The OTN is required to allow the transport of synchronisation via SDH/SONET client connections.»SDH/SONET client connections must meet
G.825 Network Limits after transport over the OTN.»A synchronisation reference chain which meets
G.825 Network Limits is proposed in ITU-T Rec. G.8251.
Issue 05/01 Slide 1.155 http://www.oscilloquartz.com Oscilloquartz SA
SDH synchronisation link connectionsSDH synchronisation link connections
»Supported by an SDH multiplex section trail
»The SDH multiplex section trail may be supported by an optical channel of the OTN (Optical Transport Network)
»Supported by an SDH multiplex section trail
»The SDH multiplex section trail may be supported by an optical channel of the OTN (Optical Transport Network)
Issue 05/01 Slide 1.156 http://www.oscilloquartz.com Oscilloquartz SA
SDHSDH
OTNOTN
SDH/SONET
OTN
PRCSynchronizationSSU
SDH synchronisation link connectionsSDH synchronisation link connections
SDH multiplex section trail
Synch. link connection
Optical trail
Issue 05/01 Slide 1.157 http://www.oscilloquartz.com Oscilloquartz SA
The control of jitter and wanderThe control of jitter and wander
»SDH requires that jitter and wander be kept below tight network limits.
»This is achieved by inserting narrow-bandwith SSUs in the synchronisation chain.
»Narrow-bandwith SSUs attenuate jitter andwander components that lie outside theSSU bandwith.
»SDH requires that jitter and wander be kept below tight network limits.
»This is achieved by inserting narrow-bandwith SSUs in the synchronisation chain.
»Narrow-bandwith SSUs attenuate jitter andwander components that lie outside theSSU bandwith.
Issue 05/01 Slide 1.158 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation reference chain for SDH over OTN
Synchronisation reference chain for SDH over OTN
OTNIsland
OTNIsland
PRC
SSU
SSU
SEC
SEC
typ. 10 OTN NEs
typ. 10 OTN NEs
max. 20 SEC
x n (n < 10) max. n x 10 OTN NEs
Issue 05/01 Slide 1.159 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation reference chain for SDH over OTN
Synchronisation reference chain for SDH over OTN
» ITU-T Rec. G.8251 for SDH over Optical Transport Network (OTN):
»Not more than 10 OTN islands in the chain»Insertion of an SSU after each OTN island»Not more than 10 OTN NEs per OTN island
(may be redivided freely over the OTN islands)»Not more than 20 SECs in the pure SDH tail
» ITU-T Rec. G.8251 for SDH over Optical Transport Network (OTN):
»Not more than 10 OTN islands in the chain»Insertion of an SSU after each OTN island»Not more than 10 OTN NEs per OTN island
(may be redivided freely over the OTN islands)»Not more than 20 SECs in the pure SDH tail
Issue 05/01 Slide 1.160 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation reference chain for SDH over OTN
Synchronisation reference chain for SDH over OTN
OTNIsland
PRC
SSU
SSU
SEC
SEC
max. 20 SECs
typ. 10 OTN NEs
max. 20 SEC
n x SDHm x OTNn + m < 10
max. (60 SECs+ m x 10 OTN NEs)
SEC
SEC
Issue 05/01 Slide 1.161 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation reference chain for SDH over OTN
Synchronisation reference chain for SDH over OTN
»There may be a mix of pure SDH islands and SDH-over-OTN islands.»Not more than 10 islands alltogether»Insertion of an SSU after each island»Not more than 20 SECs in a pure SDH island»Not more than 60 SECs in the entire chain
»There may be a mix of pure SDH islands and SDH-over-OTN islands.»Not more than 10 islands alltogether»Insertion of an SSU after each island»Not more than 20 SECs in a pure SDH island»Not more than 60 SECs in the entire chain
Issue 05/01 Slide 1.162 http://www.oscilloquartz.com Oscilloquartz SA
6. GSM and UMTS-FDD Radio Access Networks
6. GSM and UMTS-FDD Radio Access Networks
Issue 05/01 Slide 1.163 http://www.oscilloquartz.com Oscilloquartz SA
GSM Network ArchitectureGSM Network Architecture
MSC
BSC
MS
BTS
BTS
BTS
TransportNetwork
» MSC: Mobile Switching Center
» BSC: Base Station Controller
» BTS: Base Transceiver Station
» MS: Mobile Station (handy)
» MSC: Mobile Switching Center
» BSC: Base Station Controller
» BTS: Base Transceiver Station
» MS: Mobile Station (handy)
Issue 05/01 Slide 1.164 http://www.oscilloquartz.com Oscilloquartz SA
UMTS Network ArchitectureUMTS Network Architecture
MSC
BS
UE
BS
BS
BS
TransportNetwork
» MSC: Mobile Switching Center
» RNC: Radio Network Controller
» BS: Base Station
» UE: User Equipment (handy)
» MSC: Mobile Switching Center
» RNC: Radio Network Controller
» BS: Base Station
» UE: User Equipment (handy)
Issue 05/01 Slide 1.165 http://www.oscilloquartz.com Oscilloquartz SA
Relevant GSM StandardsRelevant GSM Standards
»ETS 300 577: Digital cellular telecommunications systems (Phase 2+); Radio transmission and reception
»ETS 300 912: Digital cellular telecommunications systems (Phase 2+); Radio subsystem synchronization (GSM 05.10)
»ETS 300 577: Digital cellular telecommunications systems (Phase 2+); Radio transmission and reception
»ETS 300 912: Digital cellular telecommunications systems (Phase 2+); Radio subsystem synchronization (GSM 05.10)
Issue 05/01 Slide 1.166 http://www.oscilloquartz.com Oscilloquartz SA
Relevant UMTS-FDD StandardsRelevant UMTS-FDD Standards
»3G TS 25.401: …, UTRAN OverallDescription.
»3G TS 25.402: …, Synchronisation in UTRAN Stage 2.
»3G TS 25.305: ..., Stage 2 Functional Specification of Location Services in UTRAN.
»3G TS 25.401: …, UTRAN OverallDescription.
»3G TS 25.402: …, Synchronisation in UTRAN Stage 2.
»3G TS 25.305: ..., Stage 2 Functional Specification of Location Services in UTRAN.
Issue 05/01 Slide 1.167 http://www.oscilloquartz.com Oscilloquartz SA
GSM Synchronisation Requirements(at the radio interface)
GSM Synchronisation Requirements(at the radio interface)
» Max. frequency error: 0.05 ppm for observation intervals down to 0.577 ms
» Max. phase error over a 0.577 ms long « burst »:»20 degrees peak-to-peak»5 degrees RMS
» « Burst » timing error: 1 microsecond over 0.5 s observation interval
» Holdover capability to keep within 0.05 ppm max. freq. error over the repair time
» Max. frequency error: 0.05 ppm for observation intervals down to 0.577 ms
» Max. phase error over a 0.577 ms long « burst »:»20 degrees peak-to-peak»5 degrees RMS
» « Burst » timing error: 1 microsecond over 0.5 s observation interval
» Holdover capability to keep within 0.05 ppm max. freq. error over the repair time
Issue 05/01 Slide 1.168 http://www.oscilloquartz.com Oscilloquartz SA
UMTS Synchronisation Requirements(at the radio interface)
UMTS Synchronisation Requirements(at the radio interface)
» Max. frequency error: 0.05 ppm
» Holdover capability to keep within 0.05 ppm max.freq. error over the repair time
» Max. frequency error: 0.05 ppm
» Holdover capability to keep within 0.05 ppm max.freq. error over the repair time
Issue 05/01 Slide 1.169 http://www.oscilloquartz.com Oscilloquartz SA
Synchronisation Network Architectures
Synchronisation Network Architectures
»PDH-based solution
»SDH-based solution
»GPS-based solution
»PDH-based solution
»SDH-based solution
»GPS-based solution
Issue 05/01 Slide 1.170 http://www.oscilloquartz.com Oscilloquartz SA
PDH-Based SynchronisationPDH-Based Synchronisation
MSC BSC
MS
BTS
PDHMUX
PDHMUX
E1 E1
Switch
PRC
PDH transport network
PDHMUX
PDHMUX
E1 E1
PDHMUX
PDHMUX
E1 E1
Issue 05/01 Slide 1.171 http://www.oscilloquartz.com Oscilloquartz SA
SDH-Based SynchronisationSDH-Based Synchronisation
MSC BSC
MS
BTS
E1 E1
PRC
SDH transport network
SDH NE
E1 E1E1 E1
RET
SDH NESDH NE SDH NE
SYN
C
SYN
C
SYN
CRET = retiming
Issue 05/01 Slide 1.172 http://www.oscilloquartz.com Oscilloquartz SA
GPS-based SynchronisationGPS-based Synchronisation
MSC
BSC MS
BTS
BTS
BTS
TransportNetwork
GPS satellites
Issue 05/01 Slide 1.173 http://www.oscilloquartz.com Oscilloquartz SA
The problem with PDH over SDHThe problem with PDH over SDH
IMPORTANT:
»PDH path layers supported by SDH path layers are not suitable for transportingsynchronisation.
IMPORTANT:
»PDH path layers supported by SDH path layers are not suitable for transportingsynchronisation.
Issue 05/01 Slide 1.174 http://www.oscilloquartz.com Oscilloquartz SA
Wander from pointer adjustmentsWander from pointer adjustments¸ The payload is asynchronously mapped using bit
stuffing, but since its position is referenced to theSTM-N frame, each pointer adjustment causes a phase step to the PDH tributary desynchroniser
TRIBUTARYTRAFFIC SONET/SDH OUTPUTSIGNAL PAYLOAD WANDER
1.5Mbit/s VC-11, VT1.5 4.63µs2Mbit/s VC-12, VT2 3.47µs34,45Mbit/s VC-3, STS-1 0.16µs140Mbit/s VC-4 0.16µs
· Therefore unlike PDH, SONET and SDH are NOTsuitable to transport 1.5Mbit/s or 2Mbit/s SD trails
¸ The payload is asynchronously mapped using bitstuffing, but since its position is referenced to theSTM-N frame, each pointer adjustment causes a phase step to the PDH tributary desynchroniser
TRIBUTARYTRAFFIC SONET/SDH OUTPUTSIGNAL PAYLOAD WANDER
1.5Mbit/s VC-11, VT1.5 4.63µs2Mbit/s VC-12, VT2 3.47µs34,45Mbit/s VC-3, STS-1 0.16µs140Mbit/s VC-4 0.16µs
· Therefore unlike PDH, SONET and SDH are NOTsuitable to transport 1.5Mbit/s or 2Mbit/s SD trails
Issue 05/01 Slide 1.175 http://www.oscilloquartz.com Oscilloquartz SA
Typical 2Mbit/s output TIE plot for a VC-12 pointer adjustmentTypical 2Mbit/s output TIE plot for a VC-12 pointer adjustment
1E1E--66
2E2E--66
3E3E--66
4E4E--66
11 22 33 44 55 66 7700
00Time (s)Time (s)
3.1E3.1E--663.6E3.6E--66
dd = 1E= 1E--77dtdt
== FrequencyFrequency offsetoffset
TIE (s)TIE (s)
Issue 05/01 Slide 1.176 http://www.oscilloquartz.com Oscilloquartz SA
Retiming IRetiming I
ClockClockrecoveryrecovery
BufferBuffermemorymemorywritewrite
E1 or DS1 data inE1 or DS1 data in
EquipmentEquipmentclockclock
readread
RetimedRetimeddatadataoutout
Timing signalTiming signal
Issue 05/01 Slide 1.177 http://www.oscilloquartz.com Oscilloquartz SA
Retiming IIRetiming II»Retiming is applied on E1 or DS1 traffic signals
affected by excessive wander.
»The long-term frequency (data rate) of the traffic signal must locked to the network PRC.
»The retiming buffer transmits the incoming traffic at the data rate of the timing signal, thus removing the excessive wander.
»Retiming is used when E1/DS1 traffic signals transported over SDH/SONET are used as synchronisation links (e.g. GSM BST).
»Retiming is applied on E1 or DS1 traffic signals affected by excessive wander.
»The long-term frequency (data rate) of the traffic signal must locked to the network PRC.
»The retiming buffer transmits the incoming traffic at the data rate of the timing signal, thus removing the excessive wander.
»Retiming is used when E1/DS1 traffic signals transported over SDH/SONET are used as synchronisation links (e.g. GSM BST).
Issue 05/01 Slide 1.178 http://www.oscilloquartz.com Oscilloquartz SA
7. cdmaOne, cdma2000 and UMTS-TDD Radio Access
Networks
7. cdmaOne, cdma2000 and UMTS-TDD Radio Access
Networks
Issue 05/01 Slide 1.179 http://www.oscilloquartz.com Oscilloquartz SA
cdmaOne/2000 Synchronization Requirements
cdmaOne/2000 Synchronization Requirements
»Phase synchronization
»Frequency accuracy of base station transmit carrier: 5E-8
»Phase-time accuracy of base station time base:»Normal operation: 3 µs»Reference failure: 10 µs over 8 h failure period
»Phase synchronization
»Frequency accuracy of base station transmit carrier: 5E-8
»Phase-time accuracy of base station time base:»Normal operation: 3 µs»Reference failure: 10 µs over 8 h failure period
Issue 05/01 Slide 1.180 http://www.oscilloquartz.com Oscilloquartz SA
UMTS-TDD Synchronization Requirements
UMTS-TDD Synchronization Requirements
»Phase synchronization
»Frequency accuracy of base station transmit carrier: 5E-8
»Phase-time accuracy of base station time base in normal operation: 1.25 µs
»Phase synchronization
»Frequency accuracy of base station transmit carrier: 5E-8
»Phase-time accuracy of base station time base in normal operation: 1.25 µs
Issue 05/01 Slide 1.181 http://www.oscilloquartz.com Oscilloquartz SA
Synchronization distribution architecture
Synchronization distribution architecture
»A GPS-receiver in each base station
»A GPS-receiver per cluster of cells ormicrocells
»A GPS-receiver in each base station
»A GPS-receiver per cluster of cells ormicrocells
Issue 05/01 Slide 1.182 http://www.oscilloquartz.com Oscilloquartz SA
A GPS-receiver in each base stationA GPS-receiver in each base station
TransportNetwork
MSC
RNC
CBS
GPS
BS
GPS
Issue 05/01 Slide 1.183 http://www.oscilloquartz.com Oscilloquartz SA
A GPS-receiver per cluster of cells or microcellsA GPS-receiver per cluster of cells or microcells
TransportNetwork
MSC
BSC
C
GPS
BS
BS
Time transfer signal & protocol
Issue 05/01 Slide 1.184 http://www.oscilloquartz.com Oscilloquartz SA
Synchronization issuesSynchronization issues
»So far the GPS is the only practical source for phase synchronization - it may be accessed directly or indirectly (via other signals carrying GPS time or phase).
»Redundant GPS-receivers and GPS-antennas do not protect against degradation of the GPS radio signal due to interference or jamming.
»So far the GPS is the only practical source for phase synchronization - it may be accessed directly or indirectly (via other signals carrying GPS time or phase).
»Redundant GPS-receivers and GPS-antennas do not protect against degradation of the GPS radio signal due to interference or jamming.
Issue 05/01 Slide 1.185 http://www.oscilloquartz.com Oscilloquartz SA
Thank you