The document is a course outline for a Digital Networks course at Dar es Salaam Institute of Technology (DIT). The outline covers the following topics: SDH Network, IP Networks, MPLS Fundamentals, IMS, GSM Network, UMTS/HSPA Networks, LTE Network, and WLAN Network.

1. DIT
Dar es Salaam institute of Technology (DIT)
ETU 08102
Digital Networks
Ally, J
jumannea@gmail.com

2. Course Outline
 SDH Network
 IP Networks
 MPLS Fundamentals
 IP Multimedia Subsystem (IMS)
 GSM Network
 UMTS/HSPA Networks
 LTE Network
 WLAN Network
DIT

3. DIT
Synchronous Digital
Hierarchy (SDH) Network

4. DIT
Introduction
What is Synchronous Digital Hierarchy (SDH)?
 SDH is a transmission system (protocol) which defines the
characteristics of digital signals, including frame structure,
multiplexing method, digital rates hierarchy and interface code
pattern
 A synchronous digital transport system aimed at providing a more
simple, economical, and flexible telecommunications network
infrastructure
 An International Standard for a high capacity optical
telecommunication network
Why did SDH emerge?
 Need for a system to process increasing amounts of information
 New standard that allows mixing equipment from different suppliers

5. What is PDH?
 The Plesiochronous Digital Hierarchy (PDH) is a technology
used in telecommunications networks to transport large
quantities of data over digital transport equipment such as
fibre optic and microwave radio systems.
 PDH networks run in a state where different parts of the
network are nearly, but not quite perfectly, synchronized.
 PDH allows transmission of data streams that are nominally
running at the same rate, but allowing some variation on the
speed around a nominal rate
 By analogy, any two watches are nominally running at the
same rate, clocking up 60 seconds every minute.
 However, there is no link between watches to guarantee
they run at exactly the same rate, and it is highly likely that
one is running slightly faster than the other
DIT

6. PCM-30 System (1/2)
DIT

7. PCM-30 System (2/2)
 Digital data and voice transmission is based on a 2.048 Mbit/s
bearer consisting of 30 time division multiplexed (TDM)
channels, each running at 64 Kbps.
 The 2.048 Mbit/s bearer is known as E1. Channel 0 and 16 are
used to transmit additional signaling information within the
PCM-30 frame.
 Increasing traffic over the past decade has demanded that more
and more of these basic E1 bearers be multiplexed together to
provide increased capacity.
 At the same time, rates have increased through 8, 34, and 140
Mbit/s.
 The highest capacity commonly encountered today for
intercity fibre optic links is 565 Mbit/s, with each link carrying
7,680 base channels, and now even this is insufficient.
DIT

8. DIT
PDH Systems Worldwide

9. PDH Multiplexing
 The common base for the multiplex levels of plesiochronous bearers is
represented by the 64 kbit/s channel.
 One branch describes the multiplex levels of plesiochronous bearers in the
Japanese standard, one further branch shows the multiplex levels of the
American standard and a third one describes the conditions of the European
standard.
 Within the European standard the multiplex level 1 is made up of bearers with
a data rate of 2.048 Mbit/s. This rate is formed by the PCM-30 frame.
 The Japanese and American standards possess a data rate of 1.544 Mbit/s. In
this case, 24 channels of 64 kbit/s each are multiplexed together. Multiplex
level 2 is achieved by multiplexing 4 bearers of level 1.
 For the Japanese and American standards, this represents a multiplexed data
rate of 6.321 Mbit/s. The European standard has a combined data rate of 8.448
Mbit/s for multiplex level 2.
 In the European multiplex structure 4 bearers each of the corresponding
hierarchical level are multiplexed together to obtain the bearer for the next
higher multiplex level.
DIT

10. Limitation of PDH
 Existing PDH is point to point system
 Optical Fiber capacity is under utilized
 Difficulty in centralized supervision
 Restoration of fault is time consuming
 Manpower requirement is more
 If 140 Mbps is passing through and the customer
wants one 2 Mbps, then we have to Demultiplex
from 140 Mbps to 2 Mbps for providing the 2 Mbps
 The use of Justification Bits at different levels of
multiplexing means that locating the 2 Mbps in 140
Mbps is not possible
DIT

11. DIT
Disadvantages of PDH (2)

12. Why use SDH ?
 No world standard on digital format (three
incompatible regional standards - European,
North American and Japanese)
 No world standard for optical interfaces
Networking is impossible at the optical level
 Rigid asynchronous multiplexing structure
 Limited management capability
DIT

13. When do we use SDH ?
 When networks need to increase capacity,
SDH simply acts as a means of increasing
transmission capacity
 When networks need to improve flexibility, to
provide services quickly or to respond to new
change more rapidly
 When networks need to improve survivability
for important user services
 When networks need to reduce operation
costs, which are becoming a heavy burden
DIT

14. SDH Bit Rates Comparison
DIT

15. SDH Advantages
 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
connect capability
 Network survivability
 Auto restoration of faults in no time
 Optimum utilization of optical Fiber Bandwidth
 Centralized supervision by NMS, Less manpower
required
DIT

16. SDH Advantages
 Upgradation of system is easy
 Existing PDH can work on SDH
 Network Simplification- A single synchronous
multiplexer can perform the multiplexing function
 Future Proof Networking – SDH is able to handle
video on demand and all other new systems like ATM,
Ethernet, DVB, etc.
 As the number of equipment are reduced, the space,
power consumption & the maintenance cost also
reduced
 Bandwidth on demand - Any bandwidth required by
customer can be provided in short notice
DIT

17. DIT
Advantages of SDH
 Compatibility

18. DIT
Synchronous Network Structure

19. DIT
SDH Evolution
SDH evolution is possible because of the following factors :
 Fibre Optic Bandwidth : The bandwidth in Optical Fibre can be
increased and there is no limit for it. This gives a great advantage
for using SDH
 Technical Sophistication : Although, SDH circuitary is highly
complicated, it is possible to have such circuitary because of VLSI
technique which is also very cost effective
 Intelligence : The availability of cheaper memory opens new
possibilities
 Customer Service Needs : The requirement of the customer with
respect to different bandwidth requirements could be easily met
without much additional equipment. The different services it
supports are :
1. Low/High speed data.
2. Voice
3. Interconnection of LAN
4. Computer links
5. Feature services like H.D.T.V.
6. Broadband ISDN transport (ATM transport)

20. DIT
Synchronous Digital Hierarchy (SDH)
VT1.5 VT1.5 VT1.5 VT1.5
VT1.5 VT1.5 VT1.5 TU-11
VT1.5 VT1.5 VT1.5
TU-11 TU-11 TU-11 TU-11
TU-11 TU-11 TU-11
TU-11 TU-11 TU-11
STM-0 STM-0 STM-0
VC-3
DS3
other
other
other
other
other
other
New services, Data,
Video, etc.
STM-0
Standard SDH Rates
Equivalent voice calls
STM-0 51.84 Mb/s 672
STM-1 155.52 Mb/s 2,016
STM-4 622.08 Mb/s 8,064
STM-16 2488.32 Mb/s 32,256
STM-64 9953.28 Mb/s 129,024
VC: Virtual Container
TU: Tributary Unit
TU-11
DS1: Digital signal level-1

21. DIT
SDH Frame Structure
Bit rate of STM-1= 9*270*8*8000=155.52Mbits/s

22. DIT
SDH Frame Structure
 Section Overhead (SOH) Area
– operational functions
– monitoring functions
– control functions
 Administrative Unit (AU)-Pointer
– shows the beginning of the virtual container of the
highest level
 Payload Area
– transport of the data

23. DIT
Information Payload
 Also known as Virtual Container level 4 (VC-4)
 Used to transport low speed tributary signals
 Contains low rate signals and Path Overhead (POH)
 Location: rows #1 ~ #9, columns #10 ~ #270

24. DIT
Section Overhead (SOH)
 Fulfills the section layer
OAM functions
 Types of Section Overhead
1. RSOH monitor the
regenerator section
2. MSOH monitor the
multiplexing section
 Location:
1. RSOH: rows #1 ~ #3,
columns #1 ~ #9
2. MSOH: rows #5 ~ #8,
columns #1 ~ #9

25. DIT
Administrative Unit Pointer (AU-PTR)
 Indicates the first byte of VC4
► Location: row #4, columns #1 ~ #9

26. DIT
Why do we need pointer
 Neighboring network elements (NEs) may have different
bit rates
 In one NE the frequency of input fin may differ from the
output fout
 Tasks of the Pointer
• The pointer shows the begin of the Virtual Container
within the higher structure
• Adaptation of the bit rate of the VC to the velocity of the
transport channel (AU, TU)
• A flag within the pointer signals the changes made
• Kind of stuffing will be signalized also

27. DIT
SDH Multiplexing
 SDH Multiplexing includes:
 Low to high rate SDH signals (STM-1 STM-N)
 PDH to SDH signals (2M, 34M & 140M STM-N)
 Other hierarchy signals to SDH Signals (ATM STM-N)
 Some terms and definitions:
 Mapping - A process used when tributaries are adapted
into VCs by adding POH information
 Aligning - This process takes place when a pointer is
included in a Tributary Unit (TU) or an Administrative Unit
(AU), to allow the 1st byte of the VC to be located
 Multiplexing - This process is used when multiple low
order path signals are adapted into a higher-order path
signal, or when high-order path signals are adapted into a
Multiplexing Section

28. DIT
SDH Multiplexing Structure

29. DIT
STM-1 Signals as Transport Pipe
A STM-1 Signal Can Transport:
 One 140 Mbit/s PDH Signal
 Three 34 Mbit/s PDH Signals
 Sixty-three 2 Mbit/s PDH Signals
 Combinations, eg. twenty-one 2 Mbit/s and Two 34
Mbit/s PDH Signals
 ATM cells, FDDI, DQDB Protocols, etc.

30. DIT
Common SDH Network Element (NE)
 TM (Terminal Multiplexer)
The terminal multiplexer is used to multiplex local
tributaries (low rate) to the STM-N (high rate) aggregate.
The terminal is used in the chain topology as an end
element

31. DIT
Common SDH NE
ADM (Add and Drop Multiplexer)
The Add And Drop Multiplexer (ADM) passes the (high rate)
stm-N through from his one side to the other and has the
ability to drop or add any (low rate) tributary
The ADM used in all topologies

32. DIT
Common SDH NE
REG-Regenerator
It mainly performs 3R function:
1R – Re amplification
2R – Retiming
3R – Reshaping
It regenerates the clock and amplifies the incoming
distorted and attenuated signal. It derive the clock signal
from the incoming data stream.

33. DIT
Common SDH NE
Digital Cross Connect (DXC)
 Permits switching of transmission lines with different bit-
rate
 DXC can add and drop lower-order signals

34. PDH and SDH Comparison
DIT

35. DIT
Network Management System (NMS)
 SDH aims to provide standardized, centralized O&M
system
 SDH management
 Performance management
 Fault/Event management
 Configuration management
 Accounting management
 Security management

36. DIT
Photonic Network
Operation System
(GMPLS)
λ
2
3λ
λ1
Photonic LAN/
Enterprise Nwk
Regional/Metro Nwk
OXCOXC
OADMOADM
Submarine
Term.
WDMWDM
Term.Term.
Long-Haul Terrestrial
Backbone Nwk
SDH/SONETSDH/SONET
Gb/10Gb EtherGb/10Gb Ether100B-T100B-T
OXCOXC
OXCOXC
OADMOADM
OADMOADM
Photonic Networks
Metro/Access Nwk
International/
Submarine Network (Nwk)
OXCOXC
Σλ
Σλ
GMPLS: Generalized Multi Protocol Label SwitchingGMPLS: Generalized Multi Protocol Label Switching
PONPON
Residential Nwk
OADMOADM
OADM: Optical Add/Drop Multiplexing, OXC: Optical Cross-connectOADM: Optical Add/Drop Multiplexing, OXC: Optical Cross-connect
Σλ
Σλ
Σλ Σλ
Σλ
Σλ
Σλ
Σλ
Σλ
ΣλΣλ

37. DIT
Evolution of Photonic Networks
Optical
processing
Optical
processing
OXC
Optical RouterOptical Router
YEAR
1995 2000 2005 2010
1 st Generation 2 nd Generation 3 rd Generation 4 th Generation
REGILA
TRM WDM
Point - to - point
WDM transmission Add - Drop function
with Ring configuration
Optical cross connect function
with Mesh configuration
Optical packet/processing
capability with wavelength
conversionOADM
ILA
REG
OADMOADM
OXC
OXC
2015

38. DIT
2020 -2002 - 2005 2005 - 2010 2010 - 2020
Transmission
Capacity
Rate/ch.
Node/Server
Technologies
λ/Fiber
∼2 Tb/s
10G/2.5G...
10G Ether
OADM/OXC
(1 - 5 Tb/s)
Tunable-LD
VCSEL
Tunable filter
MEMS
∼5 Tb/s
∼ 500
40G/10G...
(40G Ether?)
Opt. routing
(∼10Tb/s)
Opt. packet
Opt. signal process.
Opt. 3R
λ-conversion
∼10 Tb/s
∼ 1000
160G/40G/10.
.
All-opt. router
(≥ 40Tb/s)
OTDM
Q-PSK
Opt. IC
Cryptography
∼100 Tb/s
∼ 10000
> 1T
Band ∼100 nm ∼200 nm ∼400 nm
≥ 1000 nm
Noiseless amp.
DWDM
Adaptive
compensation
Quantum computer
Quantum optical
communication
Devices
Short pulse LD
Photonic crystal
Holey fiber
Quantum dots
Opt. nano-device
Opt. Memory
Lower loss fiber
∼ 200
Ubiquitous
router
CPU/Storage ≥1 Gb/s
(Elec. connect.)
≥10Gb/s
(Elec./Opt. connect.)
≥100Gb/s
(Opt. connect.)
Photonic Technology Roadmap