plesiochronous digital hierarchy.ppt
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7/23/2019 Plesiochronous Digital Hierarchy.ppt
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PlesiochronousPlesiochronousDigital HierarchyDigital Hierarchy
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PDHPDH
MULTIPLEXINGMULTIPLEXING
PLESIOCHRONOUS HIGHERPLESIOCHRONOUS HIGHER
ORDER DIGITLORDER DIGITL
MULTIPLEXINGMULTIPLEXING
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PDH MUX NORTH MERICPDH MUX NORTH MERIC
The !" channel PCM syste# is theThe !" channel PCM syste# is the
$ri#ary or%er o& Digital MUX'$ri#ary or%er o& Digital MUX'
I& it is necessary to trans#it #ore than !"I& it is necessary to trans#it #ore than !"channels( the syste# is )uil%*u$ as in thechannels( the syste# is )uil%*u$ as in the
+Plesiochronous Digital Hierarchy, as+Plesiochronous Digital Hierarchy, as
sho-n in the %iagra#sho-n in the %iagra#
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DIGITAL TRANSMISSIONDIGITAL TRANSMISSION
HIERARCHY HIERARCHY
TI MUX
T2 MUX
T3 MUX
T4 MUX
64kb/s
1
24 1.544 Mb/s
Four
1.544Mbits/s
Inputs
1
46.312 Mbits/s
Seven 6.312
inputs
1
7
274.17
Mbits
Six 44.736 Mbits/s
inputs
1
6
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DIGITAL MUX LEVELS IN North America, Europe, apa!DIGITAL MUX LEVELS IN North America, Europe, apa!
Digital MUXDigital MUXLe.elLe.el
No'o& /"0)1sNo'o& /"0)1sChannelsChannels
North #ericaNorth #erica
M)its1sM)its1s
Euro$eEuro$eM)its1sM)its1s
2a$an M)its1s2a$an M)its1s
33 44 3'3/"3'3/" 3'3/"3'3/" 3'3/"3'3/"
44 !"!" 4'5""4'5"" 4'5""4'5""
6363 !'3"7!'3"7
"7"7 6'45!6'45! 6'45!6'45!
!! 8/8/ /'64!/'64! /'64!/'64!
4!34!3 7'""77'""7
66 "73"73 6"'6/76"'6/7 6!'3/"6!'3/"
/9!/9! ""'69/""'69/
46""46"" 84'35684'356
4""34""3 89'9!789'9!7
"" 48!348!3 468'!/"468'!/"
"36!"36! !9"'49/!9"'49/
59/359/3 689'!33689'!33
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PDH MUXPDH MUX
:our $ri#ary syste#s ;!"*channle each<:our $ri#ary syste#s ;!"*channle each<
are co#)ine%( #ulti$le=e%( to &or# anare co#)ine%( #ulti$le=e%( to &or# an
out$ut ha.ing 8/ channels' This is calle%out$ut ha.ing 8/ channels' This is calle%
the secon% or%er o& #ulti$le=ing' Se.enthe secon% or%er o& #ulti$le=ing' Se.en
8/ channel syste#s can )e #ulti$le=e% to8/ channel syste#s can )e #ulti$le=e% to
gi.e an out$ut o& /9!* channels ;Thir%gi.e an out$ut o& /9!* channels ;Thir%
or%er o& Multi$le=ing<' Si= /9! > channelsor%er o& Multi$le=ing<' Si= /9! > channelssyste#s are #ulti$le=e% to gi.e an out$utsyste#s are #ulti$le=e% to gi.e an out$ut
o& "36! channels ;&ourth or%er<o& "36! channels ;&ourth or%er<
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Secon% Or%er ;DS!<PDHSecon% Or%er ;DS!<PDH
MUX;4'5"" to /'64! M)1s<MUX;4'5"" to /'64! M)1s< The /'64!*M)1s out$ut o& a secon% or%er ;The /'64!*M)1s out$ut o& a secon% or%er ;DS2DS2<<
Multi$le=er is create% )y #ulti$le=ing &our &irstMulti$le=er is create% )y #ulti$le=ing &our &irst
or%er ;or%er ;DS1DS1< #ulti$le=ing out$uts' This is %one )y< #ulti$le=ing out$uts' This is %one )y
interlea.ing the )it strea# o& the &our $ri#aryinterlea.ing the )it strea# o& the &our $ri#arysyste#s'syste#s'
Each in%i.i%ual )it strea# is calle% theEach in%i.i%ual )it strea# is calle% the
++tributary”tributary”''
The #ain $ro)le# to o.erco#e in this $rocess isThe #ain $ro)le# to o.erco#e in this $rocess is
the organi?ation o& the &our inco#ing tri)utaries'the organi?ation o& the &our inco#ing tri)utaries'
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Cont***Cont***
Synchronous Digital ha.e tri)utaries -ith the sa#eSynchronous Digital ha.e tri)utaries -ith the sa#ecloc@ &reAuency( an% they are all synchroni?e% to acloc@ &reAuency( an% they are all synchroni?e% to a
#aster cloc@'#aster cloc@'
Plesiochronous Digital Muti$le=ers are ha.e tri)utariesPlesiochronous Digital Muti$le=ers are ha.e tri)utaries
that ha.e the sa#e no#inal &reAuency ;that #eansthat ha.e the sa#e no#inal &reAuency ;that #eans
there can )e s#all %i&&erence &ro# one to another<( )utthere can )e s#all %i&&erence &ro# one to another<( )ut
they are not synchnroni?e% to each other'they are not synchnroni?e% to each other'
:or synchronous case( the $ulses in each tri)utary all:or synchronous case( the $ulses in each tri)utary allrise an% &all %uring the sa#e ti#e inter.al'rise an% &all %uring the sa#e ti#e inter.al'
:or the PDH( the rise an% &all ti#e o& the $ulses in:or the PDH( the rise an% &all ti#e o& the $ulses in
each tri)utaries %o not coinci%e -ith each other'each tri)utaries %o not coinci%e -ith each other'
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PDH Euro$ePDH Euro$e
63 ch
!'3"7 M)1s
4!3 ch
7'""M)1s
"73 ch6"'6/7
M)1s
48!3 ch
468'!/"M)1s
9/73 ch
5/"'88!
M)it1s
/"
@)its1s
=63=
"
="="
="
Euro$e
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Interlea.ingInterlea.ing
The #ulti$le=ing o& se.eral tri)utaries canThe #ulti$le=ing o& se.eral tri)utaries can
)e achie.e% )y either )e achie.e% )y either
Bit )y )it #ulti$le=ing ;)it interlea.ing<Bit )y )it #ulti$le=ing ;)it interlea.ing<
or% )y -or% #ulti$le=ing ;)yteor% )y -or% #ulti$le=ing ;)yte
interlea.ing<interlea.ing<
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BIT INTERLEINGBIT INTERLEING
There are &our )it strea#s to )eThere are &our )it strea#s to )e
#ulti$le=e%' One )it is seAuentially ta@en#ulti$le=e%' One )it is seAuentially ta@en
&ro# each tri)utary so that the resulting&ro# each tri)utary so that the resulting
#ulti$le=e% )it strea# has e.ery &i&th )it#ulti$le=e% )it strea# has e.ery &i&th )it
co#ing &ro# the sa#e tri)utary' s$eci&icco#ing &ro# the sa#e tri)utary' s$eci&ic
no' o& )its ;usually 7<( &or#ing a -or%( areno' o& )its ;usually 7<( &or#ing a -or%( are
ta@en &ro# each tri)utary in turn'ta@en &ro# each tri)utary in turn'
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Byte Interlea.ingByte Interlea.ing
Byte interlea.ing sets so#e restraints onByte interlea.ing sets so#e restraints on
the &ra#e structure o& the tri)utaries an%the &ra#e structure o& the tri)utaries an%
reAuire great a#ount o& #e#ory ca$acity'reAuire great a#ount o& #e#ory ca$acity'
Bit interlea.ing is #uch si#$ler )ecause itBit interlea.ing is #uch si#$ler )ecause it
is in%e$en%ent o& &ra#e structure an% alsois in%e$en%ent o& &ra#e structure an% also
reAuires less #e#ory ca$acity'reAuires less #e#ory ca$acity'
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PDH &eaturesPDH &eatures
Bit interlea.ing is use% &or North #ericanBit interlea.ing is use% &or North #erican
an% Euro$ean PDH syste#' ty$ical /'64!an% Euro$ean PDH syste#' ty$ical /'64!
M)1s $lesichronous #ulti$le=er has &ourM)1s $lesichronous #ulti$le=er has &our
$ri#ary ;DS4< MUX( each ha.ing an out $ut$ri#ary ;DS4< MUX( each ha.ing an out $ut
o& 4'5"" M)1s( )it interlea.e% to &or# theo& 4'5"" M)1s( )it interlea.e% to &or# the
ne=t le.el in hierarchy'ne=t le.el in hierarchy'
Note that this out$ut rate o& /'64! M)1s is notNote that this out$ut rate o& /'64! M)1s is note=actly &our ti#es the tri)utary )it rate o&e=actly &our ti#es the tri)utary )it rate o&
4'5"" M)1s' This is a result o& the non*4'5"" M)1s' This is a result o& the non*
sychronous nature o& the syste#'sychronous nature o& the syste#'
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PDH :eaturesPDH :eatures
E.ery tri)utary has its o-n cloc@' E.ery tri)utaryE.ery tri)utary has its o-n cloc@' E.ery tri)utaryis ti#e% -ith $lesiochronous &reAuency( that is ais ti#e% -ith $lesiochronous &reAuency( that is ano#inal &reAuency a)out -hich the shi&ts aroun%no#inal &reAuency a)out -hich the shi&ts aroun%
it -ithin $re&i=e% li#its' :or e=a#$le( the $ri#aryit -ithin $re&i=e% li#its' :or e=a#$le( the $ri#ary#ulti$le=er out$ut is 4'5"" M)1s * 53$$#'#ulti$le=er out$ut is 4'5"" M)1s * 53$$#'
To account &or the s#all .ariations o& theTo account &or the s#all .ariations o& thetri)utaries &reAuencies a)out the no#inal .aluetri)utaries &reAuencies a)out the no#inal .alue
-hen #ulti$le=ing &our tri)utaries to the ne=t-hen #ulti$le=ing &our tri)utaries to the ne=thierarchy le.el( a $rocess @no-n as $ositi.ehierarchy le.el( a $rocess @no-n as $ositi.estu&&ing ;also @no-n as $ositi.e Fusti&ication< isstu&&ing ;also @no-n as $ositi.e Fusti&ication< isuse%'use%'
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Positi.e Pulse stu&&ing orPositi.e Pulse stu&&ing or
Fusti&ication Fusti&ication
Pulse stu&&ing in.ol.es intentionally #a@ing thePulse stu&&ing in.ol.es intentionally #a@ing theout$ut )it rate o& a channel higher than theout$ut )it rate o& a channel higher than thein$ut rate' The out$ut channel there&orein$ut rate' The out$ut channel there&orecontains all the in$ut %ata $lus a .aria)lecontains all the in$ut %ata $lus a .aria)le
nu#)er o& +stu&&e% )its that are not $art o& thenu#)er o& +stu&&e% )its that are not $art o& theinco#ing su)scri)er in&or#ation'inco#ing su)scri)er in&or#ation'
The stu&&e% )its are inserte% at the s$eci&icThe stu&&e% )its are inserte% at the s$eci&ic
locations( to $a% the in$ut )it strea# to thelocations( to $a% the in$ut )it strea# to thehigher out$ut )it rate' This stu&&e% )its #ust )ehigher out$ut )it rate' This stu&&e% )its #ust )ei%enti&ie% at the recei.ing en% so that +%e*i%enti&ie% at the recei.ing en% so that +%e*stu&&ing, can )e %one to reco.er the original )itstu&&ing, can )e %one to reco.er the original )it
strea#'strea#'
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Cont***Cont***
Pulse stu&&ing is use% &or higher or%erPulse stu&&ing is use% &or higher or%er
#ulti$le=ing -hen each o& the inco#ing#ulti$le=ing -hen each o& the inco#ing
lo-er or%er tri)utary signal islo-er or%er tri)utary signal is
unsynchroni?e%( an% there&ore )ears nounsynchroni?e%( an% there&ore )ears no
$re&i= $hase relationshi$ to any o& the$re&i= $hase relationshi$ to any o& the
other'other'
The situation is .i.i%ly %e$icte% in &ig'The situation is .i.i%ly %e$icte% in &ig'
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BIT INTERLEINGBIT INTERLEING
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BTE INTERLEINGBTE INTERLEING
Word by Word MULTIPLEXING
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BIT INTERLEINGBIT INTERLEING
SIMPLI:IED SDH MULTIPLEXINGSIMPLI:IED SDH MULTIPLEXING
SNCHRONOUS BE INTERLEINGSNCHRONOUS BE INTERLEING
;No Stu&&ing nee%e%<;No Stu&&ing nee%e%<
HIGR ORDER
MULTIPLEXER
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Si#$li&ie% PDH )it interlea.ingSi#$li&ie% PDH )it interlea.ing
;Stu&&ing Nee%e%<;Stu&&ing Nee%e%<
** **Higher
Or%er
Multi$le=er
44
:ra#e no'4 :ra#e no !
Lo-er Bit Rate
Higher Bit Rate
Stu&&ing
Control )it Stu&&ing
)it is a%ata )it
Stu&&ing )it
is a stu&& )it
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De*stu&&ing at Recei.e si%eDe*stu&&ing at Recei.e si%e t the recei.ing en% the -riting cloc@ has the sa#e t the recei.ing en% the -riting cloc@ has the sa#e
characteristics as those o& the trans#it rea%ing cloc@'characteristics as those o& the trans#it rea%ing cloc@'That is( it has a &reAuency that is on a.erage the sa#eThat is( it has a &reAuency that is on a.erage the sa#e
as that o& the tri)utary( )ut it $resents $erio%ic s$acesas that o& the tri)utary( )ut it $resents $erio%ic s$aces
&or the &ra#e structure an% ran%o# s$aces &or the&or the &ra#e structure an% ran%o# s$aces &or the
stu&&ing $rocess' $hase loc@ loo$ ;PLL< circuit isstu&&ing $rocess' $hase loc@ loo$ ;PLL< circuit isuse% to re%uce(use% to re%uce(
2itter cause% )y the &ra#e structure2itter cause% )y the &ra#e structure
Higher &reAuency Fitter co#$onents ;-aiting ti#e<Higher &reAuency Fitter co#$onents ;-aiting ti#e<cause% )y stu&&ingcause% )y stu&&ing
Tri)utary signal Fitter Tri)utary signal Fitter
2itter intro%uce% )y the /'64! M)1s lin@'2itter intro%uce% )y the /'64! M)1s lin@'
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PDH MUX Euro$ePDH MUX Euro$e
In su##ary( the $ositi.e stu&&ing #etho% in.ol.esIn su##ary( the $ositi.e stu&&ing #etho% in.ol.esthe canceling o& a cloc@ $ulse assigne% to athe canceling o& a cloc@ $ulse assigne% to a$articular tri)utary in so#e o& the &ra#es in or%er to$articular tri)utary in so#e o& the &ra#es in or%er tocoor%inate the ti#ing o& the $lesiochronouscoor%inate the ti#ing o& the $lesiochronoustri)utaries into a #ulti$le=e% out$ut' Ran%o#tri)utaries into a #ulti$le=e% out$ut' Ran%o#s$aces are there&ore create% in the &ra#e( as -ells$aces are there&ore create% in the &ra#e( as -ellas $erio%ic s$aces' In the $erio%ic s$aces &ra#eas $erio%ic s$aces' In the $erio%ic s$aces &ra#ealign#ent -or% )its ser.ice )its( an% stu&&ing controlalign#ent -or% )its ser.ice )its( an% stu&&ing control)its are inserte%' The tri)utary in&or#ation )its are)its are inserte%' The tri)utary in&or#ation )its areinserte% in the ran%o# s$aces in the a)sence o&inserte% in the ran%o# s$aces in the a)sence o&stu&&ing( or logic 4 is use% -hen stu&&ing ta@enstu&&ing( or logic 4 is use% -hen stu&&ing ta@en$lace' Re#e#)er( the stu&&ing $luses carry no$lace' Re#e#)er( the stu&&ing $luses carry no
su)scri)er in&or#ation'su)scri)er in&or#ation'
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PDH ENDPDH END
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