synchronization in sdh network

8/16/2019 Synchronization in SDH network

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1 © NOKIA 1999 FILENAMs.PPT/ DATE / NN

Synchronisation in SDH Network


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Synchronisation in SDH

• Synchronisation in SDH networks• Why? How? If not what happens?• Additional equipment needed

•Specifications

• Examples :• General SDH network• Cellular transport network

•Conclusions

• Synchronisation in SDH networks• Why? How? If not what happens?• Additional equipment needed

• Specifications• Examples :

• General SDH network• Cellular transport network

• Conclusions


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What happens if the SDH-equipment are not synchronisedWhat happens if the SDH-equipment are not synchronisedwell enoughwell enough

Why synchronisation is needed in SDH

• he !uffer in desyn"hronisers mayo#erflow $or e#en "ollapse% due tothe multiple pointer ad&ustments

• he elasti" !uffers in the 'DHequipment may o#erflow due tothe wander (enerated in SDH)equipment

• In other words there may happen!it errors if the SDH equipmentare not syn"hronised well enou(h

• '* S• "li"ks• noise !ursts

• low speed data• resends• +A,

• !la"k lines• #ideo

• rollin( pi"ture• GS-• "hannel o#erlap


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Synchronous Network Concept

• A Clock dis !i"# io$ $% &o!k is $%%d%d'• All (% s)$c(!o$i*+ io$ si,$+ls +!% !+c%+"l%

o P!i-+!) % %!%$c% Clock P C• T(% !% %!%$c% si,$+l o (% 0!i-+!) so#!c%

is !+$s0o! %d (!o#,(o# (% $% &o!k +$d

#s%d o s)$c(!o$i*% (% loc+l clocks• i%!+!c(ic+l i-i$, dis !i"# io$ s !#c #!%

• )$c(!o$o#s $% &o!k' A $% &o!k i$&(ic( +ll (% co--#$ic+ io$ li$ks +!%s)$c(!o$i*%d o + co--o$ clock so#!c%



What are !itter and wander

'hase De#iation is the de#iation of an ed(e from its ideal position in time.

/ow frequen"y $012 H3% phase de#iation 4 WA5D67Hi(h frequen"y $812 H3% phase de#iation 4 9I 67

Wander is also si(nal delay #ariation



" Clock noise" Diurnal wander #temperature effects etc$%" &ultiplexing" Clock offset #e$g$ in SDH%" 'ointer ad!ustments" 'DH - SDH mappingetc$$$

Causes of !itter and wander



(n SDH network synchronisationmaster sla)e principle is used with SS&

*$+,,' C

*$+,.SS/

*$+,.SS/

*$+,.SS/

*$+,.SS/

*$+,.SS/

*$+,.SS/

*$+,.SS/

*$+,.SS/

*$+,.SS/

0ransit

1ocal

SS& 2 Synchronisation Status &essage$SS; 4 Syn"hronisation Supply ;nit%

'rimary eference Clock



Synchronisation specifications

• (0/-0 network specs$• G.)> Introdu"tion• pr6 S =22 @ >)> Ar"hite"ture• pr6 S =22 @ >)= 5etwork limits

• E0S( equipment specs$• pr6 S =22 @ >)@ SS;• pr6 S =22 @ >)B S6C• pr6 S =22 @ >) '7C

+or traffi" "arryin( si(nals G.= G.B and 6 S D6 -)=2 apply


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Synchronisation reference chain

3 42 ,5

N 42 .5total SECs 42 65

3 42 ,5

N 42 .5total SECs 42 65

' C 2 'rimary eference Clock *$+,,

SS/ 2 Synchronisation Supply /nit *$+,.

SEC 2 Synchronous Equipment Clock *$+,7

N x SECs

SS/

' C

,st

3-,8th

38th

N x SECs

N x SECs

SS/

SS/

N x SECs

*$+57 9 E0S 755 :6.-.;


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SS& tells quality of sync$ originEuality ori(inator le#el

'7C $hi(hest% '7C defined in pr6 S =22 @ >) and G.


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Chain is the


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SS& ena


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Su


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Synchronisation planning

• -aster)sla#e syn"hronisation• 'riority ta!les• ;se of SS- ena!les all network

topolo(ies to !e prote"ted

• imin( loops are a#oided !ysyn"hronisation plannin(


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Synchronisation planning

• ;se only one !a"kup for ea"helement• Che"k the desi(n usin(

walkin( rule:

Stand on one node. Start walkin( alon(the arrows !oth priorities. If you e#erwalk throu(h any node twi"e you ha#ea timin( loopF$do not make ;)turns%

'7C

1st priority

>nd priority


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?dditional equipment

• *$+,,4 accuracy ,",5 -,,4 6, ns

rearrangement

• Caesium-


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?dditional equipment

• /sed to refresh timingand pro)ide hold-o)er

• *$+,. #sla)e clock%4 holdo)er accuracy",5 -,5 B ,",5 - day

#transit%

4 , us rearrangement

• u


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Synchronisation deli)ery for upper networklayersG e$g$ for digital exchanges

• Deri#e timin( fromsyn"hronisation trail

whi"h is not supported !ySDH

or

• 7e"o#er timin( fromS -)5 si(nal

,:5&7:&+& 7:&

+&

SS/ SS/.&HF .&


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PDH PDH

?)oid pointer processing in timingdistri


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What is re-timing

Without retiming;

' C

'ointers herea


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Cellular transport network #regional%

PSTN

MSC

BSC

BSC

?ccess network

?ccess network

MSC

BSC

SDH transportnetwork

,$ (ncoming .& from &SC.$ (nternal SE0S

PRC

,$ Iptical Dir ,.$ Iptical Dir .7$ (nternal SE0S

,$ Iptical Dir ,.$ Iptical Dir .7$ (nternal SE0S

,

. ,

.

,.,

.

,$ Iptical Dir ,.$ (nternal SE0S

, ,


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Cellular transport network #access%

BSC

BTS

BTS

BTS

BTSBTS

BTS

BTS

BTS

BTS&icrowa)e radio#n " .&


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.,

.,

SS/

A

A

A

' C

SynchronisationNIDE E EN

' (&? J SECIND? J

'rimaryComplete

StartSecondary

SS/


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3ey issues in synchronisation

• Syn"hronisation sour"es are prote"ted• frequen"y a""ura"y is not a pro!lem

• Wander a""umulation is "ontrolled• lo"ked mode sta!ility• referen"e swit"hin( and hold)o#er • wander referen"e model in G.=

5etwork limits for wander are spe"ified in 6 S =22 @ >)=


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Conclusions

• Sele"t the primary sour"e $'7C% for timin( "arefully• -o#e o#er to SDH

synchronization in sdh network

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