Introductin sdh-pdh

INTRODUCTION PDH &
SDH
On Job Training July 2006
PT Indonesia Comnets Plus

On Job Training, July 2006
Agenda
 Pre SDH (PDH)
 SDH
 The SDH Frame
 Frame Structure
 Overhead and Payload
Analysis
 Tributary Units
 SDH Network
Protection

Plesiochronous Digital Hierarchy

Multiplexing hierarchy
 The PDH high capacity transmission
networks are based on a hierarchy of
digital multiplexed signals: E.1 to E.4.
 The basic building block is the primary
rate of 2.048 Mb/s (E.1). This could be
made up of 30 x 64 Kb/s voice channels.
This would then be multiplexed up to a
higher rate for high capacity transmisson.

 Four signals at the primary rate can be
multiplexed up to the secondary rate,
E.2, of 8.448 Mb/s and so on up to a rate
of 139 Mb/s (E.4).
 Thus the 139 Mb/s rate represents 64 x
2.048 Mb/s signals and 1920 multiplexed
voice channels.

Developing networks
 The plesynchronous multiplexing
technology, often called PDH
(Plesiochronous Digital Hierarchy), left
no room in the signal structures for
network management and maintenance
functions.
 We are therefore left with no spare signal
capacity to provide improvements in the
signal transmission.

 As networks developed inter-connection
became increasingly complex. It required
banks of multiplexers and large,
unreliable distribution frames.
 It became clear that the original
standards, designed for point-to-point
links, were just not suitable.

Tributary access
 We want to have easy access to an
individual tributary, in order that it may be
re-routed.
 We cannot do this without having to
demultiplex the whole signal down to the
required tributary level.
 Costs go up as we demultiplex, and they
then double because we have to re-
multiplex the signal back up again.

No commont standard
 Before SDH there were no standards to ensure
that equipment from different vendors
interworked on the same system.
 Vendors can have their own unique designs
which means we have to buy the same
vendor’s equipment for both ends of the line.
 Ideally we would like to shop around for the
most suitable equipment, without having to
keep to the same supplier.

What we need
 Network operating companies have to
provide faster, cost effective provisioning
of customer circuits and services, as well
as control of transmission bandwidth.

SDH Definition
 SDH is a standard for ‘high speed – high
capacity’ optical telecommunication
networks ; more spesifically a
synchronous digital hierarchy.
 It is a synchronous digital transport
system aimed at providing a more
simple, economic and flexible
telecommunications network
infrastructure.

Advantages of SDH
 Designed for cost effective, flexible
telecoms networking – based on direct
synchronous multiplexing.
 Provides built-in signal capacity for
advanced network management and
maintenance capabilities.

 Provides flexible signal transportation
capabilities – designed for existing and
future signals.
 Allows a single telecommunication
network infrastructure – interconnects
network equipment from different
vendors

Where is SDH used ?
 SDH can be used in all of the traditional
network application areas.
 A single SDH network infrastructure is
therefore possible which provides an
efficient direct interconnection between
the three major telecommunication
networks.

Notes on SDH rates
 The most common SDH line rates in use
today are 155.52 Mbps, 622.08 Mbps,
2.5 Gbps, 10 Gbps.
 SDH is a structure that is designed for
the future, ensuring that higher line rates
can be added when required.

SDH signal structure
 The SDH signal is transported as a
synchronous structure which comprises
a set of 8-bit bytes organised into a two
dimensional frame.
 The ‘Truck analogy’ is a popular way to
help us understand the contents of the
SDH frame.

SDH FRAME STRUCTURE
TRUCK ANALOGY
Tractor
Unit
Payload
Unit

SDH FRAME STRUCTURE
TRUCK ANALOGY contd.
Virtual Container
Section
Overhead
Payload
Payload
OverHead
Multiplexer
Section
OverHead
Regenerator
Section
OverHead

The Payload
 The contents of the container carried by
the truck represent the real value.
 This ‘Payload’ is analogous to customer
traffic, being carried by the ‘container’
within an SDH frame.
 This Payload ‘container’ supports the
transportation of spesific tributary
signals.

The Section Overhead
 What actually gets the contentsof the truck
to it’s destination is the tractor unit.
 This analogous to the network
maintenance and management capability
carried by the SDH frame, known as it’s
Section OverHead, or SOH.

 The Section Overhead (SOH) provides
facilities that are required to support and
maintain the transportation of customer
traffic Safely across the network.
 THE SOH is split into Multiplexer Section
Overhead (MSOH) and Regenerator
Section Overhead (RSOH).

The Virtual Container
 Even if the container is loaded on to a
different truck, there is a portion of
overhead that always remains with it.
 This is known as the Path OverHead, or
POH.
 The Path Overhead is directly associated
with the payload capacity area, and
together they form what’s known as the
Virtual Container.

SDH FRAME STRUCTURE
STM-N FRAME STRUCTURE
270 x N Columns
261 x N Columns
9 x N Columns
9Rows
= 8 bits/byte

SDH FRAME STRUCTURE
signal frame transmission
The principle for SDH signal frame transmission is: the bytes (8-bit)
within the frame structure is transmitted byte-by-byte (bit-by-bit) from
left to right and from top to bottom. After one row is transmitted, the
next row will follow. After one frame is completed, the next frame will
start

SDH FRAME STRUCTURE
SDH Rate
ITU-T defines the frequency to be 8000 frames per second for all
levels in STM hierarchy
STM-1 Rate :
9 rows x 270 columns x 8 bits/byte x 8000 frames per second
= 155.52 Mb/s
STM-4 Rate :
9 rows x (270 x 4) columns x 8 bits/byte x 8000 frames per second
= 622 Mb/s

OVERHEAD ANALYSIS
MSOH MSOHRSOH
RSOH
RSOH
POH

OVERHEAD ANALYSIS
PATH OVERHEAD
Path Trace message
Parity check
VC structure
Alarm & performance info
User channel
Multiframe indication for TUs
Path protection switching

OVERHEAD ANALYSIS
PATH OVERHEAD contd.
• J1 : Path Trace byte
• B3: Path BIP−8 Code
• C2: Signal label byte
• G1: Path status byte
• F2, F3: Path user channels
bytes
• H4: TU position indicator byte
• K3: Spare byte
• N1: Network operator byte

SDH Multiplexing Structure
STM-1 AU-4
TU-3
AUG-1
TUG-3 VC-3 C-3
VC-4 C-4
TU-12 VC-12 C-12
TUG-2
×1 ×1
×3
×1
×7
×3
139264 kbit/s
34368 kbit/s
2048 kbit/s
Pointer processing
Multiplexing
Mapping
Aligning
AUG-4
AUG-16
AUG-64
STM-4
STM-16
STM-64
×1
×1
×1
×4
×4
×4
Go to glossary

SDH Tributary Multiplexing (34M)
34 Mbit/s to STM-N
34M Rate
Adaptation
Add POH
1
C3
1 84
9
125μs
1 1
9
VC3
P
O
H
125μs
1 85
Next
page
Packing Mapping

1st
align
Fill
gap
1 86
1
9
H1
H2
H3
R
×3
86
TU-3
1
H1
H2
H3
1
9
P
O
H
R R
VC-4
9
1
1 261
Aligning Stuffing
TUG-3
Multiplexing
3
Same as
for C4
Multiplexing route: 1X34M  1XTU-3  3XTUG-3  1XAU-4---One STM-1 can load three
34Mbit/s signals

2 Mbit/s to STM-N
2M
Next
page
125μs
POH
1 4
C12
1
9
VC12
1 4
1
9
TU12
1 4
1
9
TU-PTR
Rate
Adaptation
Add
POH
Packing
Add
Pointer
Mapping Aligning

×3
1 12
TUG-2
1
9
×7 R R
TUG-3
1 86
Multiplexing
1
9
Multiplexing
Same
as for
C3
Multiplexing route: 1X2M  3XTU12  7XTUG-2
 3XTUG-3  1XSTM-1--- One STM-1 can load
3X7X3 = 63X2M Signals
Multiplexing structure: 3-7-3 structure

SDH Network protection
 Bidirectional Traffic
 Traffic flow direction
along the ring
 Clockwise or counter-
clockwis
The traffic shares the same
equipment and link
B
a) Uniformly routed
A
Unidirectional Traffic
 Traffic flow direction along the ring
 Clockwise and counter-clockwise
T1516670-94
The traffic shares the same
equipment and link
B
A
a) Uniformly routed
B
b) Diversely routed
The traffic is on
different equipment
and links

Difference between Path and
Multiplex Section
Physical Layer
e.g. Optical fiber
Multiplex section
Path

1+1 Linear MS Protection
 Protection mechanism of 1+1linear MS
protection system:
 Concurrent sending is permanent bridging
 Selective receiving is switchingselective receiving
concurrent
sending
TU traffic TU traffic
concurrent
sending
selective receiving
switch
switch

1:N Linear MS Protection
 Structure of 1:N Linear MS Protection
A B
Bridging Selector
Protection section (Transmit)
Working section 1(Transmit)
Protection section (Receive)
Working section 1(Receive)
Working section 2(Transmit)
Working section 2(Receive)
Working section N(Transmit)
Working section N(Receive)
Selector Bridging

1:1 Linear MS Protection
 Protection mechanism of 1:1 linear MS
protection system:
 Traffic flow after protection switching
switch
switch
TU traffic TU traffic
Working
Protection

Two-fiber uni-directional path
protection ring
 Protection switching mechanism:
 Switching criteria
 Transmission quality of each individual channel
 Usually TU-AIS, TU-LOP alarms
A
B
C
D
switch
S1
P1

 Traffic flow when network is broken:
 Working channels=1-N/2 AU4
 Protection channesl=N/2-N AU4
Two-fiber bidirectional Multiplex
Section Shared Protection Ring

 APS controller:
 Transition of APS controller status:
Two-fiber bidirectional Multiplex

 Structure:
 Four fibers
 Working channels--S1,S2, carry normal traffic
 Protection channels--P1,P2, protect normal
traffic
Four-fiber bidirectional Multiplex
CA AC
CA AC
S1
P1
A
C
D B
P1
S1
S2
P2
P2
S2

SubNetwork Connection
Protection
 Description:
 Protection one SubNetwork Connection
 Can be adapted to all networks

 Normal condition for unidirectional
SNCP:
 Concurrent sending (transmit end)
 Selective receiving (receive end)
Protection

 Failure in working channels for unidirectional
SNCP:
 Concurrent sending (transmit end)
 Selective receiving (receive end)
Protection

 Protection Restoration:
 Restoration time - 10 minutes (5-12 minutes)
A
B
C
D
switch
S1
P1
A
B
C
D
S1
P1
Protection

Introductin sdh-pdh

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