• SDH provides transmission network with
vendor independent environment.
• (SDH) signals the beginning of a new
phase in evolution of the world‘s
• The network operator will experience significant cost
savings associated with reduced amount of hardware
in the network and increased efficiency and reliability
of the network.
• Designed to support future services such as
Metropolitan Area Network (MAN), Broadband
6. What is SDH?
• The SDH is a hierarchical set of digital transport
structures, standardized for the transport of payloads
over physical transmission networks.
• ITU-t recommendations
- STM-1 155Mbps,
- STM-4 622 Mbps
- STM-16 2.4 Gbps
- STM64 10 Gbps
8. Benefits of SDH-
• Network Simplification -performs the function of
the entire Plesiochronous multiplexer mountain‘
hence reduces no of equipment used . Simplified
maintenance, reduction in floor space required by
equipment and lower power consumption.
• Survivability -deployment of optical fiber makes end
to end monitoring and maintenance possible. The
failure of links or even nodes to be identified
immediately. Uses self-healing ring architecture, the
network will be automatically reconfigured , re-
routed as the faulty section has been repaired. As a
result, failures will not disrupt services.
• Software Control -fully software controllable. Other
functions such as performance monitoring,
configuration management, resource management,
network security etc. Remote provisioning and
centralized maintenance will mean a great saving in
time .Reduces expenses.
• Bandwidth on Demand -possible to dynamically
allocate network capacity or bandwidth on demand.
• Future-proof Networking -ideal platform for
services ranging form POTS, ISDN and mobile radio
through to data communications (LAN, WAN etc.).
Handles latest services like video on demand and
digital video broadcasting via ATM. Selected as the
bearer network for the next generation of
12. Advantages of the SDH system
• First world standard in digital format.
• First optical Interfaces.
• Transversal compatibility reduces networking cost.
Multi vendor environment drives price down
• Flexible synchronous multiplexing structure.
• Easy and cost-efficient traffic add-and-drop and cross
• Reduced number of back-to-back interfaces improves
network reliability and serviceability.
• Powerful management capability.
• New network architecture. Highly flexible and
survivable self healing rings available.
• Backward and forward compatibility: Backward
compatibility to existing PDH
• Forward compatibility to future B-ISDN, etc.
14. Services supported are -
• Low/High speed data.
• Interconnection of LAN
• Computer links
• Feature services like H.D.T.V.
• Broadband ISDN transport (ATM transport)
15. When to use SDH?
• Networks need increased transmission capacity.
• Networks need to provide improve flexibility (quick
• Networks need to provide improve survivability.
• Networks need to reduce operation costs.
• Number of rows in a frame : 9
• Number of columns in a frame : 9 + 261 = 270
• Number of bytes/frame : 9 x 270
• Number of bits /frame : 9 x 270 x 8
• Number of bits per second : 9 x 270 x 8 x 8000
• = 15552000 or 155.52 Mbps
18. Elements of frame Structure
Frame structure consists of –
• SOH -SOH bytes are used for communication
between adjacent pieces of synchronous equipment.
• RSOH –RSOH is used for the needs of the
• MSOH –MSOH is used for the needs of the multiplex
• Pointer -defines frame offset of a VC with respect to
• the frame reference
• Mapping In SDH
• Alignment In SDH
• Multiplexing In SDH
• Principle of SDH Multiplexing
• SDH Multiplexing Structure
• PDH Signal to STM frame conversion
• Multiplexing of 140Mbps Signal
• Multiplexing of 34Mbps Signal
• Multiplexing of 2Mbps Signal
21. What is Mapping
• This is the procedure by which tributaries are adapted into
• Container of C-11, C-12, C-2, C-3, C-4 type are filled with
• Mapping is the first step in creation of STM-N frame
22. What is Alignment
• This is the procedure by which the frame offset
information is incorporated into the Tributary unit or
• Alignment applied after the complition of Mapping.
• It is the process in which Virtual Container is
adapted to TU or AU.
23. What is Multiplexing
• It is a process in which multiple Higher order path layer
signals are Adapted into a Multiplex section.
• Also if the multiple Lower order path layer signals Adapted
to Higher order path layer signals.
• With multiplexing STM-N frame is completed.
24. Principle of SDH Multiplexing
• Depending upon the PDH bit rates, various VCs are formed.
• VC-1, VC-3 and VC-4 are formed for European PDH bit rates
2 Mbps, 34 Mbps and 140 Mbps respectively.
• STM-N frame is fully synchonized, but the location of VCs
within a STM-N frame are not be fixed with time.
• Multiplexing scheme allows each container of
any size and bit rate (PDH’s) to be fit in STM-
27. Multiplexing of 140Mbps Signal
Synchronous multiplexing of 140 Mbps signal Involves,
• Forming Container C-4
• Forming Virtual Container VC-4
• Forming Administrative Unit AU-4
• Formation of Administrative Unit Group (AUG)
• Adding SOH to form STM-1
29. Multiplexing of 34Mbps Signal
Synchronous multiplexing of 34 Mbps signal Involves,
• Forming Container C-3
• Forming Virtual Container VC-3
• Forming Tributary Unit TU-3
• Formation of Tributary Unit Group (TUG-3)
• Multiplexing TUG-3 into VC-4
• Next Procedure same as 140Mbps
31. Multiplexing of 2Mbps Signal
Synchronous Multiplexing of 2 Mbps signal Involves,
• Forming Container C-1
• Forming Virtual container (VC-12)
• Forming Tributary Unit (TU-12)
• Multiplexing of TU-12 to form TUG-3
• Next procedure same as 34Mbps
• SDH Network in Layers
• Elements of SDH Network
• Terminal multiplexer
• ADD/DROP multiplexer
• Digital cross connect(DXC)
• Network management system(NMS)
• Devices that implement SDH transmission referred as
• NE’s include regenerator section, multiplex section
and path terminating section equipment's.
• SDH NE’s integrate to form the Digital loop
carrier(DLC) to support SDH architecture and
• SDH NE are subdivided into various layers.
36. Terminal Multiplexer
• TM is a path terminating element that concentrate or
aggregate DS1,E1s ,STM-Ns.
• Various PDH signals are mapped with their associated
SDH electrical payload in TM. For eg.
37. Terminal Multiplexer
• Application of TM:
1. Transmission system (STM-1, STM-4,STM-16)
2. Multiplexing of Signals
3. For higher bit rates signals
4. Point-to-point (Chain network)
38. ADD/DROP Multiplexer(ADM)
• PTE that can multiplex & demultiplex various signals
to or from STM-N signals. At add/drop side, only
those signals that need to be accessed are dropped or
inserted. Remaining traffic continues through NE
without signal processing.
• Single stage ADM can multiplex or demultiplex one
or more tributary signals to or from STM-N. Used in
Terminal side(low speed side) where lower bit rate
signals can add or drop into high speed SDH signals.
• Automatic back-up path switching is possible using
elements in ring in fault.
• Next generation multiservice platform have their roots
in ADM which carry data services over SDH.
• It regenerates attenuated signals which causes due to
long distance between multiplexer.(Signals becomes
too low to drive receiver)
• Also called as repeater. As it retransmit regenerated
high power signal. They derive their clock signal from
incoming data stream.
• Since 1990, REG have been replaced by optical
• Functions of REG.:
1. Regeneration of signals
3. Retransmission of high power signals toward
1. In point-to-point and in ring network
2. For long haul distance communication
42. DIGITAL CROSS-CONNECT(DXC)
• Used for setting up semi-permanent interconnection
between different channels. Regroup & switch data
streams between interfaces of cross connect system.
For eg. UMUX- multiservice access system( equipped
for cross connect system with STM-4 system).
• 2 types- 1.Broadband DXC & 2.Wideband DXC
43. DIGITAL CROSS-CONNECT(DXC)
• Core function is cross connection
• Used at hub stations.
• Used for grooming telecommunication traffic,
switching traffic from one to other in network failure
44. NETWORK MANAGEMENT SYSTEM
• NMS is combination of software & hardware used to
monitor and administer a network.
• Network elements(NE’s ) in a network are managed
by this NMS system.
• NMS manages NE such as fault, accounting,
configuration and performance managements.
• NMS employs various protocols to perform these
tasks such as SNMP protocol can be used to gather
information from devices in network.
b) Topology types
i)point to point.
ii)point to multipoint.
v) star topology.
c)Extended star topology.
d)Deployment of SDH.
1)How the nodes in the system are connected.
2)Topology can be considered at many different levels:
physical, logical, connection, or organizational.
3)Topology is considered in terms of the information
– Nodes in the graph are individual computers or
– links between nodes indicate that those nodes are
sharing information regularly in the system.
48. Topology types
a) Point to point topology
b) Point to multipoint topology
51. Ring topology
• A single centralized server cannot handle high client
load, so a common solution is to use a cluster of
machines arranged in a ring to act as a distributed
• Communication between the nodes coordinates state-
sharing, producing a group of nodes that provide
identical function but have failover and load-
• Unlike the other topologies here, ring systems are
generally built assuming the machines are all nearby
on the network and owned by a single organization.
57. Star topology advantages
• Easy to add devices as the network expands
• One cable failure does not bring down the
entire network (resilience)
• Hub provides centralised management
• Easy to find device and cable problems
• Can be upgraded to faster speeds
• Lots of support as it is the most used
58. Star topology disadvantages
A star network requires more cable than a ring
or bus network
Failure of the central hub can bring down the
Costs are higher (installation and equipment)
than for most bus networks