Telecommunication Notes Topic 1

Topic 1:

Introduction to

Next Generation Network (NGN)

❑

1.1. History of Telephony Technology

❑

1.2. Public Switched Telephone Network

1.2.1. Pulse Code Modulation
1.2.2. PSTN Network Architecture

❑

1.3. Signalling System No. 7 (SS7)

❑

1.4. Transmission System

1.4.1. Time Division Multiplexing (TDM)
1.4.2. Frequency Division Multiplexing (FDM)
1.4.3. Code Division Multiplexing
1.4.4. Wavelength Division Multiplexing (WDM)

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1.5. Time Division Multiplexing in PSTN

1.5.1. Plesiochronous Digital Hierarchy (PDH)
1.5.2. Synchronous Digital Hierarchy (SDH)
1.5.3. Dense Wavelength Division Multiplexing (DWDM)

❑

1.6. Next Generation Network

1.6.1. NGN Characteristics
1.6.2. NGN Architecture

1.1. History of Telephone Technology

Can be divided into 4 eras;

Invention Era

Analogue Era

Digital Era

NGN Era

✓Introduction to the
voice communication
engineering

✓Conceptual of
switching
methodology

✓Introduction of
analogue switching
or exchange

✓Initiation of
automatic switching
activity

✓Enhancement of
telephony
technology

✓Opening to the new
service over
telephony
technology

✓Enabling telephony
service riding on IP
environment

1.1. History of Telephone Technology: Invention Era

“Mr Watson, come here – I want to see you”

oThe first voice message by Sir Alexander Graham Bell to his
assistant; Thomas Watson on 1876 by using the telephone

oThe telephone technology staring to replace the telegraph
for elite group – very expensive service

oEnd-to-end connection – No switching operation yet

First telephone technology

Sir Alexander Graham Bell

Thomas Augustus

Watson

1.1. History of Telephone Technology: Invention Era

Issue:

oNot all civilian capable to subscribe the telephone service. It is expensive service due to end-to-end
connection

oThe existing subscriber demand for more connection, require more telephone set and require
special space

1.1. History of Telephone Technology: Invention Era - Switching Methodology

1stModel Telephone Issue:

oNot all civilian capable to
subscribe the telephone
service. It is expensive
service due to end-to-end
connection

oThe existing subscriber
demand for more
connection, require more
telephone set and require
special space

Solution:

The operator execute switching activity

oThen, the telephone exchange was introduce to enable the switching

oThe switching manually execute by the operator

oThe operator will connect the wire between the caller and the
receiver

oBy switching, the telephone service become a mass product

oIt is enabling the customer to has more connection

1.1. History of Telephone Technology: Invention Era - Switching Methodology

Issue:

oSwitching exercise require manpower (operator), more space (exchange and workstation operator)
and much jumper cord cable

oDuring peak hour, there are more longer holding time to make a call

oSometimes, the wrong connection happened due to manual switching by the operator

1.1. History of Telephone Technology: Analog Era

Manual Switching Issue:

oSwitching exercise require
manpower (operator),
more space (exchange and
workstation operator) and
much jumper cord cable

oDuring peak hour, there are
more longer holding time
to make a call

oSometimes, the wrong
connection happened due
to manual switching by the
operator

Solution:

oThe 1stautomated exchange introduce at the end of 19thcentury

oThe Strowger switch was introduced

oThen, the Crossbar switch was introduced to replace the limitation of
Strowger switch

Strowger Switch

Strowger Switch Circuit Design

Crossbar Switch
Crossbar Switch Circuit Design

1.1. History of Telephone Technology: Analog Era

Issue:

oThe number of user increase tremendously

oThe high demand for more connection and more service over the telephony service/network

1.1. History of Telephone Technology: Digital Era

Analog Switching Issue:

oThe number of user
increase tremendously

oThe high demand for more
connection and more
service over the telephony
service/network

Solution:

oThe digital exchange was
deployed by Alcatel on 1972 in
France

oThe digital exchange resolve the
all issue on the analogue
exchange

oIt also improve the voice quality
for long distance call

oThe switching operator no more
longer since the digital exchange
was deployed

oIn 1979, the dial-up (up to 56kbps) service was rolled-out. It is
enable the data transmission can be operated over the telephony
network

oIn 1990s; the ISDN service was deployed. It is enhancement of
telephony technology to improve the telephony capability (multi-
channels) and data transmission (up to 128kbps with 2 channels)

Alcatel Digital Switch

1.1. History of Telephone Technology: Digital Era

Issue:

oThe significantly drop of traditional voice traffic and user; subscriber migrate to IP based network

oThe telephony network is the end-to-end network; complicated to merge with IP based network

1.1. History of Telephone Technology: NGN Era

Issue On Traditional Voice:

oThe significantly drop of
traditional voice traffic and
user; subscriber migrate to
IP based network

oThe telephony network is
the end-to-end network;
complicated to merge with
IP based network

Solution:

oNext Generation Network is design to enable the services riding on
the IP Based Network

oNGN merge all the telecommunication networks into single network

oBeside, the Public Switched Telephone Network protocol (SS-7) still
support by NGN

oThe migration to NGN mainly execute by Service Provider with
minimal or less effected to the subscriber

NGN Network Diagram

1.1. History of Telephone Technology: Summary

Earlier Era

•End-to-End (E2E) or direct
connection

Solution:
•Introduction to the switching
methodology

•First, manual switching that
executed by the operator to
establish the call session

•1stTelephone by
Sir Alexander
Graham Bell
(1876)

Issue:
o Expensive (E2E); not all can enjoy

the service

o Require more telephones

set/device for more connections

Issue:
o Require more resources to serve

the high demand

Analog Switch

•Strowger Switch:
End of 19th

Century

•Crossbar Switch:
1sthalf of 20 Century

Digital Switch

Issue:
o Limitation for long distance call

o Rapidly increase of demands

•1972; 1stDigital Switch
deployed in France by
Alcatel

•1979; Dial-up service roll-
out

•1990s; Deployment of
ISDN exchange/switch

NGN

•Motivated towards
All-IP technology

PUBLIC SWITCHED TELEPHONE NETWORK
(PSTN)

IBU SAWAT TM DUNGUN

MAIN DISTRIBUTION FRAME (MDF)

1.2. Public Switched Telephone Network (PSTN)

oPublic Switched Telephone Network or PSTN is the traditional circuit-switched telephone network

oThis is the system that has been in general use since the late 1800s

oPSTN also known as Plain Old Telephone System (POTS)

oIt is combination of the telephone networks used worldwide, including telephone lines, fiber optic
cables, switching centers, cellular networks, as well as satellites and cable systems

oThese network enable telephone service communicate with each other at anytime and anywhere

What is Public Switched Telephone Network?

Basic PSTN Network Diagram

1.2.1 Pulse Code Modulation (PCM)

oPulse Code Modulation or PCM is a method that is used to convert an analog signal into a digital
signal

oThen, the modified analog signal can be transmitted through the digital communication network

oPCM is in binary form, so there will be only two possible states high (bit 1) or low (bit 0)

oAt the receiver, the demodulation process will revert the digital signal into analog signal

What is Pulse Code Modulation?

oThe Pulse Code Modulation
process is done in three steps;

✓ Sampling

✓ Quantization

✓ Encoding

PCM Process

1.2.1 Pulse Code Modulation (PCM): Sampling

Sampling:

oSampling is a process of taking the analog voice signal sampler at regular time intervals (TS)

oSampling frequency, fs is the number of average
samples per second also known as Sampling Rate

oAccording to the Nyquist Theorem; sampling rate
should be at least 2 times the upper cutoff
frequency;

Sampling frequency; fs >= 2 * fmax

oThen frequency band for telephone is
from 0Hz upto 4000Hz (4kHz)

oHence, the fs = 2 X 4000Hz = 8000Hz

oThen, Ts = ;

= = 125 µs

1
T

1

8000

oSo, the sampling process will occur in every 125 µs

oThe output of Sampling called Pulse Amplitude Modulation (PAM) and it is still in an analog form

Sampling Process in

PAM Waveform

1.2.1 Pulse Code Modulation (PCM): Quantization

Quantization:

oThe output from sampling still in the waveform (PAM) with the respective amplitude

oQuantization is the next process by identify the binary code to represent the amplitude (voltage) of
the original analog (PAM) signal as per TS

oThe range of the amplitude of the analog signal is further divided into limited number of level, call
quantization level, 2x

oFor voice (telephone) the standard bits
per sample (resolution) is 8 bits

oHence, 2x = 28 = 256 levels

1.2.1 Pulse Code Modulation (PCM): Quantization - Resolution

Example Quantization:

oTo understand the concept of resolution in quantization, let’s analyze the 2 bits resolution (4 level)
vs 3 bits resolution (8 level)

oMore higher quantization level will more accurate, preventing noise and maintain the quality of
original signal

2 bits resolution (4 level)

3 bits resolution (8 level)

1.2.1 Pulse Code Modulation (PCM): Encoding

Encoding:

oThe encoding is the process to code
the quantized sampler into 8 bits
(telephone) binary code per TS

oThen, the original analog signal
input fully converted into the digital
signal and ready to transmit

The 8 bits binary
code that be
transmitted to the
network at every Ts

1.2.1 Pulse Code Modulation (PCM): Data Rate for Voice

Voice Frequency Band, f

Human voice frequency
Telephone band frequency

fmin = 0Hz

fmax = 4000Hz = 4kHz

fmax = 4000Hz

Sampling Frequency, fs

Nyquist Theorem

fs = 2 fmax
fs = 2 x 4000Hz

= 8000Hz = 8kHz

Quantization Level

Resolution

Telephone/Voice = 8 bits

8 bits

Data Rate = fs x Quantization Level

= 8000Hz x 8

= 64000bHz = 64kbHz

f =

; where T in second, s

then; unit f can be wrote per second;
Hz = per second (ps)

1
T
= 64000bHz = 64kbHz

= 64000bps = 64kbps

1.2.2 PSTN Network Architecture

oAll telephone device will connected to the
nearest local switch

oThe device may use;

▪Standalone telephone

▪Private Branch Exchange (PBX)

▪Dial-up Modem

▪Fax machine

oPBX nowadays become a Private
Automated Branch Exchange (PABX) is
widely use for business customer

Standalone
Telephone

Dial-up
Modem

Fax Machine

PBX/PABX System

1.2.2 PSTN Network Architecture: Nodes and Element

oBasically, there 2 types of switching
equipment; Local Switch and Trunk Switch

oBoth switches function to route the voice
messages

oAll Local Switch will be connected to the
Trunk Switch and other local switch with
associated with the same trunk switch

oFor connection with other local switch
with associated with other trunk switch
will conducted by both trunk switches

oAnother element inside the PSTN
architecture is logical network or signaling

oSignaling System No. 7 (SS7) is the standard signaling protocol inside the PSTN network architecture

oThe SS7 will be covered on the next sub-topic (1.3)

oSS7 define the PSTN architecture with 3 types of nodes;

▪Service Switching Point

▪Signal Transfer Point

▪Signal Control Point

SS7 Signaling Point Diagram

Service Switching Point (SSP)
Signal Transfer Point (STP)
Signal Control Point (SCP)

1.2.2 PSTN Network Architecture: Signaling Nodes

Service Switching Point (SSP)

oSSP is a part of element
inside the local switch

oSSP will convert the dialed
number into signaling
message to establish the
connection

oThen, SSP will manages the
session during voice
conversation

oAfter conversion is end, the
SSP will terminate the
session

Signal Transfer Point (STP)

oSignaling message between
SSP will be route by STP

oSTP is a router; and it
function is to route the
signaling message in the
network

oFor connectivity between
the other network will
manage by STP that
function as gateway node

Signal Control Point (SCP)

oSCP can be viewed as
database

oSCP will keep the data
record of subscriber,
destination and network to
be referred by SSP in order
to establish the connection
and session

Subscriber Line:

oSubscriber Line (SL) or Local Loop (LL) is physical connection from local switch/exchange up to the
telephone device

oThis connection traditionally using single copper twisted pair

1.2.2 PSTN Network Architecture: Subscriber Line

oSince the medium is copper, commonly the signal is in analog signal

oThe analog-to-digital conversion (PCM) is execute at local switch; where the user was connected

oThe local switch will supplied DC voltage; -48V from the local switch

oOnce user pick-up the phone (off-hook), the circuit between the telephone device and local switch
will change to the closed circuit.

oThen, the voltage and current from local switch will flown

1.2.2 PSTN Network Architecture: Local Access

oLocal Access Network is the physical
pre-connected twisted pair copper;
facing to the customer premises

oIt is starting from Main Distribution
Frame (MDF) room, inside the service
provider building; pre-connected wire
up to the Cabinet

oThere are a lot of manholes between
MDF and Cabinet; this manhole is for
underground cable route

oNext, the pre-connected twisted pair between cabinet up to Distribution Point (DP) box

oMost of the cable is lay as overhead cable

oDuring provisioning of telephone service, the technician will do the jumpering inside the MDF and at
cabinet

oThen, the technician will pull the drop wire from the DP box to the telephone socket inside the
customer premise

oSome premises, the technician will advice customer to prepare the internal wiring

oThe twisted between 2 wires will eliminate the noise such as a crosstalk

MANHOLE

CABINET

Distribution
Point Box (DP
Box)

1 point = 10
subscribers

•Standard RJ11 telephone socket/port

•Standard RJ11 cable and jack

•Standard RJ11 pin and color code

1.2.2 PSTN Network Architecture: Inside the Customer Premises

1.2.3 Switching technique in telephone network

Switching is the technique by which nodes control or switch data to transmit it
between specific points on a network.

Switching is the method that is used to establish connections between nodes within
a network. Once a connection has been made, information can be sent. Telephone
switching usually refers to the switching of voice channels.

1.2.3 Switching technique in telephone network

Type of switching

technique

Packet

Switching

Soft switch
switching

• Packet Switching

• Packet switching is the process of
segmenting or broken down a message/data
to be transmitted into several smaller packets.

• Each packet is enveloped with address or
labeled with its destination and other overhead
information to ensure that it travels to the
correct destination without errors.

• Each packet is delivered independently and
each may be routed via a different path. At the
destination, the original message is
reassembled in the correct order, based on the
packet number.

1.2.3 Switching technique in telephone network : Packet switching

• Softswitch

• A softswitch is a component used in the
core network of a telecom network operator
to provide call control and signalling as well as
processing of media streams.

• It is software-based device in a
telecommunications network which provides
managing of voice, fax, data and video traffic,
routing of a call within the network, and can
process the signaling for all types of packet
protocols.

• Traditional switch is the hardware, with
physical switchboards to route the calls.
Softswitch is the VoIP software solution
which is installed on servers and has the same
functionality.

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1.3. Signalling System No. 7 (SS7)

❑

1.4. Transmission System

1.4.1. Time Division Multiplexing (TDM)
1.4.2. Frequency Division Multiplexing (FDM)
1.4.3. Code Division Multiplexing
1.4.4. Wavelength Division Multiplexing (WDM)

What is Signaling?

oSignaling is the exchange of information between involved points in the network; start from call
sets up, controls, manage and terminates each telephone call/session

oSignaling can be done using analog signal (electrical pulse) or digital signal (bits, bytes or packets)

oGenerally, signaling in PSTN can be classified into 2 groups;

▪Channel Associated Signaling (CAS), where certain signaling information is associated with
the voice channels over the same transmission medium

▪Common Channel Signaling (CCS), where signaling information from many users is
multiplexed over a common channel and can be carried separately from the voice traffic.

1.3. Signaling System No. 7: Signaling

CAS

CCS

Switch A

Switch B

Link 1

Link 1

Link 2

Link 2

Link 3

Link 3

Link 4

Link 4

1.3. Signaling System No. 7: CAS vs CCS

Transmission Medium

Data/Voice Signal

Signaling

CAS signaling flown the same transmission
medium with data/voice signal

CCS signaling flown separately transmission
medium from data/voice signal

1.3. Signaling System No. 7

oSignaling System No. 7 or SS7 was developed by ITU in 1975

oSS7 is the CCS signaling standard to be followed by PSTN and Private Land Mobile Network (PLMN)
network provider

oStarting 1980, SS7 is widely used; and by 1985 the ITU enforce all PSTN and PLM to follow SS7

SS7 Characteristics

•

It is a Common Channel Signaling system.

•

The SS7 signaling data link is a full duplex, digital transmission channel operating at 64kbps.

•

It is optimized for application in digital network with integrated digital transmission and

digital switching of SPC type.

•

It is suitable for all kind of transmission media in a digital network.

•

It is suitable for dedicated network as well as service integrated network

•

Applicable for national and international network.

1.3. Signaling System No. 7

oDivide into 4 layers;

▪Layer-1 is MTP-1

▪Layer-2 is MTP-2

▪Layer-3 isMPT-3

▪Layer-4 consists of TUP, SCCP, TCAP and ISUP

▪MTP – Message Transfer Part

▪TUP – Telephone User Part

▪TCAP - Transaction Capabilities

▪SCCP – Signaling Connection Control Part

▪ISUP – ISDN User Part

1.3. Signaling System No. 7

▪MTP – Message
Transfer Part

▪TUP – Telephone User
Part

▪SCCP – Signaling
Connection Control Part

▪TCAP - Transaction
Capabilities

▪ISUP – ISDN User Part

Layer

Function

MTP-1

Defines the physical and electrical characteristics of the signaling
link

MTP-2

Provide reliability transfer of signaling messages (CCS) between
source and the destination signaling node via a signaling link

MTP-3

Provide functionalities for routing of signaling messages between
signaling nodes.
The routing was performed by the STP signal nodes.

TUP

Performs basic telephone call connect and disconnect.
TUP is an analog protocol

ISUP

Derived from TUP to support ISDN and intelligent networking
functions.
Widely replace the TUP in the most of PSTN network.
Link between mobile network and PSTN network.

1.3. Signaling System No. 7

▪MTP – Message
Transfer Part

▪TUP – Telephone User
Part

▪SCCP – Signaling
Connection Control Part

▪TCAP - Transaction
Capabilities

▪ISUP – ISDN User Part

Layer

Function

TCAP

This protocol is used for communication between SCP nodes
through STP nodes.
Since SCP represents databases, the TCAP is mainly used to access
databases.
The end-to-end of transmission of TCAP messages is performed by
using the SCCP

SCCP

SCCP provides end-to-end routing; by enabling TCAP messages to
the proper database.
MTP layers enables the transfer of signaling messages between
signaling points while SCCP enables end-to-end transmission of
signaling messages

1.3. Signaling System No. 7

The relationship of SS7 Protocol Stack with OSI Reference Model

OSI Reference Model

SS7 Protocol Stack

1.4. Transmission System

oIn the telecommunication network, all signals are carried transmission system

oThe signal can be in;

▪electrical signals that carried over copper cables

▪optical or light signals that carried over optical fiber cable

▪radio signals that carried over wireless links

Copper Cable

Microwave

Fibre Optic Cable

1.4. Transmission System

What is multiplexing ?

“Multiplexing is a process of simultaneously transmitting two or more individual signals
over a single communication channel or link”

1.4. Transmission System

1.4. Transmission System: Multiplexing

oThe transmission system was designed to carry multiple signals from multiple users by using
multiplexing technique

oMultiplexing (MUX) increase the efficiency on transmitting the signals

oMultiplexing will combine the input signals before transmit

oCommonly, there are 4 types of multiplexing;

▪Time Division Multiplexing (TDM)

▪Frequency Division Multiplexing (FDM)

▪Code Division Multiplexing (CDM)

▪Wavelength Division Multiplexing (WDM)

oDe-multiplexing (DEMUX) at the destination will retrieve the output signal

1.4.1 Transmission System: Time Division Multiplexing (TDM)

oTime Division Multiplexing; TDM combines the signals by assigning each signal with a different time-
slot

oThe set of time-slot is call frame

oTDM over the copper cable, will transmit the signal at different time interval (time-slot) with the
same frequency

oTDM over the optical cable, will transmit the signal at different time interval (time-slot) with the
same wavelength

oDuring internet and data explosion era, the TDM is widely used for signal (data) transmission

1.4.2 Transmission System: Frequency Division Multiplexing (FDM)

oFrequency Division Multiplexing; FDM is inherently an analog technology

oThe input signals will be modulated with the different carrier frequency at the same time

oThe modulated signal is call Channel

oEach channel was separated with the guard-band to eliminate the signal overlap

oFDM widely used in broadcasting technology such as television and radio

1.4.3 Transmission System: Code Division Multiplexing (CDM)

oCode Division Multiplexing; CDM based on using the different code sequences for different signal

oCDM signal was transmitted over the same frequency band and using the same time interval

oThe unique code for different signal is also call channel

oCDM mainly used in wireless and mobile network

1.4.4 Transmission System: Wavelength Division Multiplexing (WDM)

oWavelength Division Multiplexing; WDM enable different wavelength in optical cable can be
transmitted together in the same transmission medium

oWDM is the latest technology in optical transmission medium that allow bidirectional signal over
one strand of optical cable

oIn WDM, the signal will be assigned with lambda; λ that represent the wavelength

oWDM increasing the efficiency of bandwidth utilization and capable to carry highspeed connectivity

oThus, nowadays WDM is widely used in transmission system

1.4. Transmission System: Summary of Division Multiplexing

Multiplexing

Medium

Unit

Transmission Of Signal

Signal/Service

Time Division
Multiplexing (TDM)

Copper,
Optical

Time-Slot,
Frame

Same frequency (copper),
Same wavelength (optical),
Different time (Ts)

Signalling, Data,
Voice

Frequency Division
Multiplexing (FDM)

Copper,
Wireless/
Radiolink

Channel

Same time (Ts),
Different Frequency

Broadcasting
(television, radio),
Data, Voice

Code Division
Multiplexing (CDM)

Wireless/
Radiolink

Channel

Same time (Ts),
Same frequency,
Different/unique code

Mobile
(Data, voice)

Wavelength Division
Multiplexing (WDM)

Optical

Lambda (λ)

Same time (Ts),
Different wavelenght

Signalling, Data,
Voice

❑

1.5. Time Division Multiplexing in PSTN

1.5.1. Plesiochronous Digital Hierarchy (PDH)
1.5.2. Synchronous Digital Hierarchy (SDH)
1.5.3. Dense Wavelength Division Multiplexing (DWDM)

❑

1.6. Next Generation Network

1.6.1. NGN Characteristics
1.6.2. NGN Architecture

1.5. Time Division Multiplexing in PSTN

oRefer to PCM sub-topic; the data rate for voice signal in digital signal is 64kbps

oThen, the unit for TDM is time-slot; or channel

oHence, transmission of voice signal in digital signal by using TDM is 64kbps per time-slot

oITU-T standardize the 32 time-slots are multiplexed to obtain an E1 signal

oIn America and Japan, the 24 time-slots are multiplexed to obtain a T1 (America) / J1 (Japan) signal

Level

ITU

North America

0

64kbps

64kbps (DS0)

1

Level 0 X 32;
2.048Mbps (E1)

Level 0 X 24;
1.544Mbps (T1 or DS1)

2

Level 1 X 4;
8.448Mbps (E2)

6.312Mbps (DS2)

3

34.364Mbps (E3)

44.736Mbps (DS3)

4

139.264Mbps (E4)

5

565.148Mbps (E5)

oHowever the 32 time-slots are allocated in E1, practically only 30 time-slots are utilize for voice

oTime-slot 0 is used for synchronization; Time-slot 16 for signaling related to voice connection (ccs
signaling)

1.5. Time Division Multiplexing in PSTN

European E1-Line

1.5. Time Division Multiplexing in PSTN

ITU-T has standardized the hierarchy for bit rates in digital transmission systems.
First hierarchy level (E1) in Europe and most of world is 2048 kbit/s

Bit rates for E1 = fs x no of bits x no channel

= 8000 Hz x 8 bit x 32 channel
= 2048 kbit/s

32 channel = 32 time slots (TS)

Time slot are numbered as TS-0 to TS-31
30 time slots are used for voice (in telephone network)
First time slot, TS -0 is used for synchronization.
TS-16 is mainly used for signaling related to voice connections

- In America the first hierarchy level is 1544 kbit/s and it is consisted of 24
channels, multiplexed with TDM

1.5. Time Division Multiplexing in PSTN

oRefer to PCM sub-topic; the data rate for voice signal in digital signal is 64kbps

oThen, the unit for TDM is time-slot; or channel

oHence, transmission of voice signal in digital signal by using TDM is 64kbps per time-slot

oITU-T standardize the 32 time-slots are multiplexed to obtain an E1 signal

oIn America and Japan, the 24 time-slots are multiplexed to obtain a T1 (America) / J1 (Japan) signal

Level

ITU

North America

0

64kbps

64kbps (DS0)

1

Level 0 X 32;
2.048Mbps (E1)

Level 0 X 24;
1.544Mbps (T1 or DS1)

2

Level 1 X 4;
8.448Mbps (E2)

6.312Mbps (DS2)

3

34.364Mbps (E3)

44.736Mbps (DS3)

4

139.264Mbps (E4)

5

565.148Mbps (E5)

oHowever the 32 time-slots are allocated in E1, practically only 30 time-slots are utilize for voice

oTime-slot 0 is used for synchronization; Time-slot 16 for signaling related to voice connection (ccs
signaling)

1.5.1 TDM in PSTN: Pleosiohronous Digital Hierarchy (PDH)

oThe first international standardized form of digital higher-order multiplexing

oDeployed over a variety of cable and radio systems, as well as optical fiber cable around the world

o‘Plesiohronous’ is derived from Greek; meaning nearly synchronous - relates to the situation where
the individual 2Mbps multiplex are operating at close-but slightly-varying rates

oWidely used in 1970s till 1980s for trunk transmission system

oThen, widely used in access network till the end of 20thcentury

oThe process call ‘stuffing’ or ‘justification’ is require to manage the bit patterns that will effect the
synchronous transmission information

oThe ‘stuffing’ will inserting non-information bits into signal to break-up bit patterns

oThe bit rate is controlled by a clock source in the local equipment (e.g exchange)

oAdvantage of PDH;

▪Dimensioning of equipment is suitable for street cabinets

▪Point-to-point connections

▪Cost-effective for access networks

1.5.1 TDM in PSTN: Pleosiohronous Digital Hierarchy (PDH) Architecture

PDH Logical Architecture (ITU)

PDH Logical Architecture (America/Japan)

1.5.1 TDM in PSTN: Pleosiohronous Digital Hierarchy (PDH) Disadvantage

Disadvantage

oJust allow point-to-point connection; require more space and no redundant physical link

oEach link has their own referral clock source; no standard clock referral in the network

oMaximum capacity up to 566Mpbs

oAllowed tolerance in bit rates; overhead payload

oVendor/manufacturer proprietary; can not integrate the network

1.5.2 TDM in PSTN: Synchronous Digital Hierarchy (SDH)

oThe solution for disadvantages of PDH is Synchronous Digital Hierarchy

oThe SDH is almost optical network

oHence, it is also called Synchronous Optical Network (SONET)

oSDH/SONET then started replaced the PDH for trunk transmission system

oThen, the standard or clock source was introduced to maintain the stability of data transmission

oAdvantage of SDH;

▪Dimension to carry data signal with voice signal simultaneously

▪Designed to be worked in ring network

▪Able to work with protection link; Active link with stand-by link

▪Optimized of optical cable network; allow

▪Up to 80km optical cable

1.5.2 TDM in PSTN: Synchronous Digital Hierarchy (SDH) Architecture

SDH STM-1 frame format

1.5.2 TDM in PSTN: Synchronous Digital Hierarchy (SDH) Architecture

•STM-1 frame contains 2430 bytes of information.
Each byte contains 8 data bits (i.e. a 64kbit/s channel).
Duration of STM-1 transport frame is 125us.
The number of frames per second is 1 second / 125us = 8000 Frames per second.

•So, rate of STM-1 frame is calculated as follows: -

8 bits x 2430 bytes x 8000 per sec = 155,520,000 bits/s or 155 Mbit/s

1.5.2 TDM in PSTN: Synchronous Digital Hierarchy (SDH) Architecture

•Higher SDH transport levels are obtained by using multiplexing byte by byte. In
SDH transport modules there no additional pseudo bits.

•The STM-N can be calculated as N x 155.52Mbit/s

•Example : STM-4 = 4 x 155.52Mbit/s

= 622.08 Mbit/s

1.5.2 TDM in PSTN: Synchronous Digital Hierarchy (SDH) Architecture

1.5.3 Dense Wavelength Division Multiplexing (DWDM)

oThe DWDM is the latest multiplexing for transmission system

oIt is allow a number of wavelength for transmission at the same medium and at the same time

oIt is start replacing the SDH/SONET network since the more signal is the IP based

oAdvantage of DWDM;

▪Dimension to aggregate the SDH/SONET network and IP based network

▪Allow up to 80 wavelengths simultaneously

▪Capacity up to 400Mbps

▪Optimized of optical cable network; allow bi-directional signal in the same medium

1.5.3 Dense Wavelength Division Multiplexing (DWDM) Architecture

1.6. Next Generation Network (NGN)

oThe Next Generation Network is a packet-based network

oThe idea of NGN, that can be used for both telephony and data, and also mobile network

oNext Generation Network was started by transformed the core network to IP

oSometimes, NGN is referring to as an all-IP network

1.6. Next Generation Network (NGN): Convergence of The Two Worlds

oThe NGN is the network for the future

oMost of services still riding on the legacy network

oThe legacy network is end-to-end technology that not friendly for any integration

oBasically, voice either riding on PSTN or PLMN; broadcast service riding on broadcasting network
and data service riding on data communication network (DCN)

oThe boom of internet service that riding on IP Based network is motivated for NGN; since this
network almost closely to NGN

1.6. Next Generation Network: Convergence of The Two Worlds

PSTN

Voice
The 1stWorkable Telephone
Inventor:
Sir Alexander Graham Bell (1876)

Broadcasting

Data &
Internet

NGN

1988

1.6.1 NGN: Characteristics

What is NGN?

oThe ITU defined an NGN as:

▪“A Next Generation Network (NGN) is a packet-based network able to provide services
including Telecommunication Services and able to make use of multiple broadband, QoS-
enabled transport technologies and in which service-related functions are independent from
underlying transport-related technologies. It offers unrestricted access by users to different
service providers. It supports generalized mobility which will allow consistent and ubiquitous
provision of services to users.”

1.6.1 NGN: Characteristics

oPacket-based transfer

oSeparation of control functions among bearer capabilities, call/session, and application/service

oDecoupling of service provision from network and provision of open interfaces

oSupport for a wide range of services, applications and mechanisms based on service building blocks
(including real time/streaming/non-real time services and multi-media)

oBroadband capabilities with end-to-end Quality of Service (QoS) and transparency

oInterworking with legacy networks via open interfaces

oGeneralized mobility

oUnrestricted access by users to different service providers

oA variety of identification schemes which can be resolved to IP addresses for the purposes of routing
in IP networks

oUnified service characteristics for the same service as perceived by the user

oConverged services between Fixed/Mobile

oIndependence of service-related functions from underlying transport technologies

oCompliant with all Regulatory requirements, for example concerning emergency communications
and security/privacy, etc.

1.6.1 NGN: Characteristics

Next Generation Network (NGN) services

• Voice telephony.
• Voice gateway
• Data services
• Multimedia services
• Virtual private networks (VPN's)
• Public network computing (PNC)
• E-commerce
• Interactive gaming

Source: ITU-T Rec. Y.2001

1.6.1 NGN: Architecture