Lebanese university
Faculty of Engineering
Telecom Department
Planing and dimensioning of a
PSTN network
Prepared by : Mohamad Tawba
Rami Faour
Presented to : Dr. Ahmad Raad
2501
2488
Contents :
Overview of the telephony network………………….…………..………………….3
Subject of project……………………………………………………..………………10
1.Teletrafic study and dimensioning the network…………………..…………….12
1.1 Used formuls………………………………………………..……………..12
1.2 Traffic and dimenioning ………………………………….……………13
2. Switching……………………………………………………………….…………..18
2.1 Switching overview………………………………………….……………18
2.2 Design of switching system ………………………………………….…..18
3. Intelligent network……………………………………………………………….23
3.1 IN architecture………………………………………………..…….……..23
3.2 benefits of intelligent network…………………………………………….25
3.3 inportant IN services……………………………………………………….26
3.4 Design of IN network………………………………………………………27
4. Transmission………………………………………………………………….….31
4.1 Transmission overview…………………………………………………….31
4.2 Transmission network………………………………………………..……33
4.3 Design of transmission systems…………………………………..………35
5. Financial Study…………………………………………………………………47
5.1 Network cost……………………………………………………….……..47
5.2 Tariffing…………………………………………………………….…..…50
6. Next generation network………………………………………………..…...54
6.1 NGN functional architecture…………………………..….…….…….54
6.2 NGN components……………………………………………….….……57
6.3 migration to PSTN…………………………………………………….…57
6.4 advantges of NGN……………………………………….……….….…..60
7 conclusion……………………………………………………………….……62
2
Overview of the telephony network
I.
The Evolution of the Telephone system
The discovery of the telephone can be attributed to Alexander Graham Bell who in 1876
discovered that if a battery is applied across an electrical circuit (the wires) while the user
speaks, the sound wave produced by the human voice could be carried across this same pair of
wires to a receiving end set up to accept this electrical current and convert the electricity back
into sound.
Within a few decades (NOT a long duration at that time) of Bell’s discovery, the first telephone
sets were being sold. The first telephone sets were sold in pairs: each telephone was connected
to one and only one other telephone via a dedicated wire. This meant that if I wanted the
capability to be able to call 10 people, I had to have 10 telephones on my desk.
Furthermore, each telephone came with its own battery and a crank used to ring the far-end
telephone. Obviously, this was not a very scalable model.
Hence, the next step in the evolution was the development of the central office. In this model, a
user needed only one telephone set, which was connected by a single wire to the central office.
This reduced the demand on the infrastructure dramatically. To use the telephone, the user
would simply pick up the phone handset. This would connect him to the human operator sitting
at the central office. The user would then tell the human operator who he wished to be connected
to and the operator would use a patch-cord system on the telephone panel to connect him to the
destination party. Though much more efficient and scalable than the one-to-one model, the
model was limited in its capacity because of the human intervention required.
As the demand for telephone service grew and technology evolved, digital computers eventually
replaced the manual operators. This not only increased the speed of switching but also led to an
increase in the effective capacity of the network.
This eventually led to the evolution of the telephone network, aka PSTN, in its current form. For
this to happen, the analog voice signal needs to be converted to the digital world.
3
II. Digitizing Speech
The human voice produces an analog signal. When a speaker pushes air out of the lungs through
the glottis, air pulses escape through the mouth and sometimes the nose. These pulses produce
small variations in air pressure that result in an analog signal.
Human speech can be represented as an analog wave that varies over time and has a smooth,
continuous curve. The height of the wave represents intensity (loudness), and the shape of the
wave represents frequency (pitch). The continuous curve of the wave accommodates infinity of
possible values. A computer must convert these values into a set of discrete values, using a
process called digitization. Once speech is digitized, a computer can store speech on a hard
drive and transmit speech across digital networks, including corporate networks, the Internet,
and telephone-company networks, which are increasingly using digital components.
To digitize speech, an analog-digital converter samples the value of the analog signal repeatedly
and encodes each result in a set of bits. In conventional PSTN telephony, before sampling, the
converter filters the signal so that most of it lies between 300 and 3400 Hz.
This exploits the fact that, while humans can hear frequencies as high as 20 kHz, most of the
information conveyed in speech does not exceed 4 kHz.1
The sampling process uses a theorem developed by the American physicist Harry Nyquist in the
1920s. Nyquist’s Theorem states that the sampling frequency must be at least twice as high as
the highest input frequency for the result to closely resemble the original signal. Thus, the
“filtered” voice signal is sampled at 8000 Hz so that frequencies up to 4000 Hz can be recorded.
Every 125 μs (1/8000th of a second), the value (magnitude) of the analog voice signal is
recorded as a digital value. This value is typically a number between 0 and 255 (i.e., 8 bits,
which is the basic unit of storage on modern-day computers). Ten, 12 and 16 bit sampling is also
popular. By sampling this often, the result is a faithful representation of the original signal, and
the human ear will not hear distortion.
4
As the digital samples are collected, modern telephony systems may convert them into a digital
representation using pulse-code modulation or PCM. From Wikipedia, “Pulse-code modulation
(PCM) is a digital representation of an analog signal where the magnitude of the signal is
sampled regularly at uniform intervals, then quantized to a series of symbols in a digital (usually
binary) code.”
5
III. PSTN Architecture
The customer premises equipment (CPE) is typically a telephone. This connects via a dedicated
pair of wires (often known as twisted pair) to the local office (aka central office). This part of the
network that connects the end user to the local office is also known as the local loop, or the
access network.
Since many telephones (often in a single geographical area) connect to a central office, it is
possible for calls made within a geographical area to be completed within the access network.
However, for calls destined to far-away geographical areas, long-distance offices (aka Class
4 switches) come into play. The local office is connected to long-distance offices via trunks,
which can be thought of as huge capacity pipes. When a local office determines that the call is
meant for a telephone not connected directly to it, it routes the call to the appropriate Class 4
switch. This Class 4 switch is then responsible for routing this call to the appropriate Class 5
switch, which in turn will route it to the end telephone. For international calls, another level of
hierarchy comes into play, but the basic idea of hierarchical routing remains the same.
Thus far, we have discussed the PSTN architecture that carries voice calls, i.e., the media
network. However, the PSTN really consists of two logically separate networks: the signaling
6
network and the media network. To understand the difference between signaling and media,
consider what happens when you pick up your telephone and make a call. You get a dial tone,
dial digits, hear a ring-back tone and are then connected to the called party if (s)he answers the
call. Notice that a whole lot of things happen before the voice actually starts fl owing. Signaling
refers to the overall process of going off hook, getting a dial tone, dialing digits, getting a ring
back and finally getting a call connected. The media network comes into play only after the call
is connected and is used for carrying the voice. These two logically separate networks are
implemented as two physically separate networks in the PSTN.
IV.
the Telephony Network:
The Access network and the Trunk network are two main parts of the telephony network.
The Access network is a modern term used for the network, which connects subscribers to the
local exchange and supporting all type of telecommunication services. The access network is
also known as subscriber network or local network or local loop. The structure of the access
network is generally a “tree structure” meaning that it can be spread out to a large area. The
access network should detect if a certain subscriber holds his apparatus and then give a tone.
The operation and maintenance of such traditional network is about 50% of the total cost for
running the whole telephony network, we should have a good service quality. The quality of
service is identified by #of tries, successful calls.
We have 3 principle functions:



Set-up.
Release.
Supervision.
When 2 subscribers having an access between each other, then for each user we have a voice
channel allocated:


Voice channel 1: sent from subscriber A to subscriber B.
Voice channel 2: sent from subscriber B to subscriber A.
7
In Access network we don’t use copper (noise, attenuation, cross talk, cost…), we use coax, F.O.,
M. wave, DSL modem, ATM, ISDN (integrated service digital network).
The Trunk network supports the transfer of telephone traffic between different local exchanges.
The trunk cables are usually F.O. Since we need high capacity in spite of their high cost; these
are characterized by:



High bandwidth.
High bit rate.
High life time.
The structure of the trunk network was formed in hierarchical structure of local and transit
exchanges. In turn, the transit exchanges normally only transfer the traffic between the local
exchanges. In parallel with the hierarchical structure, a route selection hierarchy is used. At
each level, there is at least two or more route to a given destination. The shorted and fasted
route is called the “primary route” and it will be selected first. If this route is completely
occupied the secondary route will be selected.
The tandem exchange, also called local transit, exists in metropolitan areas. The use of a tandem
exchange eliminates the need for direct routes between all local exchanges in a metropolitan
area. In very big cities, there are a lot of interconnected tandem exchanges in cooperation.
8
9
Subject of project
1. objective
The abstract of this project is to planning , designing , and dimensioning of PSTN network for a
given country , the country consists of 6 big cities and 26 small cities and villages
2. input data









Originating traffic for residential subscribers : 500 KBHCC
Terminating traffic for residential subscribers is 66 % of originating one .
Originating traffic for business subscribers : 250 KBHCC.
Terminating traffic for business subscribers is 66 % of originating one .
Portion of internal calls pint = 30 %
Mean holding time (residential ) = 90 seconds .
Mean holding time (business ) = 120 %.
Big cities subscribers are considered to be 70 % residential and 30 % business , while
small cities and villages subscribers are 80 % residential and 20 % business .(the total
number of companies is about 2500 ).
Central processor (CP)-Execution time :






Internal
6.9 ms
Outgoing
12.5 ms
Incoming
10 ms
Maximum CP load : 75 %
Congestion : 1 %
Capacity of transit Exchange : 7000 Erlangs
Maximum capacity of RSU : 2048 Lines
40 % of traffic is interzone taffic
Links between LE and RSU : 3 E1/1000 Lines
This project is devided into 6 parts :
10
1.
2.
3.
4.
5.
6.
Teletraffic study and dimensioning of the desired network (loss System ).
Design of switching system ( Architecture , exchanges , type, capacity ,…)
Design of IN Platform (Architecture ,exchanges ,type ,capacity ,…)
Design of transmission system (Architecture, nodes, type, capacity ,…)
Financial study of the network .
Proposition of a solution to migrate the PSTN network to NGN network .
11
1.
Teletraffic study and dimensioning the network :
1.1. Used formulas
 Incoming call intensity: Yit = (N*At-N*Ao*P int) / S.
 Outgoing call intensity: Yot = N*Ao*(1-P int) / S.
 Internal call intensity: Yint = N*Ao*P int / S.
While N is the number of subscribers, Ao is the originating traffic per subscriber, and At Is the
terminating traffic per subscriber.

The average value of the Central Processor – Execution time:
Rcp= (6.9+12.5+10)/3 ms= 9.8 ms (=0.0098 sec).

Erlang B formula: the congestion E=
An/n!
∑ Ai /i!
.
While n is the number of circuits, and i is a counter from 0 to n, and A is the traffic (A= Y*S).

𝐿𝐸 𝑡𝑟𝑎𝑓𝑓𝑖𝑐 𝑜𝑢𝑡 = 𝑜𝑢𝑡𝑔𝑜𝑖𝑛𝑔 𝑐𝑎𝑙𝑙 𝑖𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 ∗ 𝑚𝑒𝑎𝑛 ℎ𝑜𝑙𝑑𝑖𝑛𝑔 𝑡𝑖𝑚𝑒 =
(1 − 𝑃 𝑖𝑛𝑡)
𝑌𝑜𝑡 (𝑟𝑒𝑠) ∗ 𝑆 𝑏 = [𝑁 ∗ 𝐴𝑜𝑟 ∗
] ∗ 𝑆 𝑏 = 𝑁 ∗ 𝐴𝑜𝑟 ∗ (1 − 𝑃 𝑖𝑛𝑡).
𝑆𝑏

LE traffic in = incoming call intensity * mean holding time =
(𝑁 ∗ 𝐴𝑡𝑟 − 𝑁 ∗ 𝐴𝑜𝑟 ∗ 𝑃 𝑖𝑛𝑡)
𝑌𝑖𝑡 (𝑟𝑒𝑠) ∗ 𝑆 𝑏 = [
] ∗ 𝑆 𝑏 = 𝑁 ∗ 𝐴𝑡𝑟 − 𝑁 ∗ 𝐴𝑜𝑟 ∗ 𝑃 𝑖𝑛𝑡.
𝑆𝑏

𝐿𝐸 𝑡𝑟𝑎𝑓𝑓𝑖𝑐 𝑖𝑛𝑡 = 𝑖𝑛𝑡𝑒𝑟𝑛𝑎𝑙 𝑐𝑎𝑙𝑙 𝑖𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 ∗ 𝑚𝑒𝑎𝑛 ℎ𝑜𝑙𝑑𝑖𝑛𝑔 𝑡𝑖𝑚𝑒 =
𝑃 𝑖𝑛𝑡
𝑌𝑖𝑛𝑡 (𝑟𝑒𝑠) ∗ 𝑆 𝑏 = [𝑁 ∗ 𝐴𝑜𝑟 ∗ 𝑆 𝑏 ] ∗ (𝑆 𝑏) = 𝑁 ∗ 𝐴𝑜𝑟 ∗ 𝑃 𝑖𝑛𝑡.








CP load (%) = [(LE traffic int+ LE traffic orig+ LE traffic term)*Rcp]/Sb *100.
Circuits LE_TE out: Is the number of circuits given by the Erlang B formula, while A utilized is
the LE Traffic out.
Circuits LE_TE in: Is the number of circuits given by the Erlang B formula, while A utilized is
the LE Traffic in.
E1 out: is the number of E1 corresponding to the Circuits LE_TE out
E1 out = circuit LE_TE out / 30
E1 in: is the number of E1 corresponding to the Circuits LE_TE in
E1 in = circuit LE_TE in /30
Interzone traffic out is the 40 % of traffic out.
Interzone traffic in is the 40 % of traffic in.
Transit traffic: LE traffic out + LE traffic in.
12
1.2. Traffic and dimensioning
The following information are used to calculate the zones tables :





The population of each city .
The population of each city after 5 years
The numbers of subscribers .
Note that the number of subscribers in the big cities are equal to 50 % of the estimated
population, and the number of subscribers in the small cities are equal to 20 % of the estimated
population.
The residential subscribers and the business subscribers .
Note that the residential subscribers in the big cities are equal to 70 % of the subscribers ,
and 80 % in the small cities .
The CP load = CP load (residential) + CP load (business )
-



Calculation of originating and terminating traffic for residential and business per
subscriber :
The total number of subscribers = 453453 subscriber
The total residential subscribers = 344847 subscriber
The total business subscribers = 137278 subscriber
Originating traffic per residential =
𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑡𝑖𝑛𝑔 𝑡𝑟𝑎𝑓𝑓𝑖𝑐(𝐵𝐻𝐶𝐶)∗𝑚𝑒𝑎𝑛 ℎ𝑜𝑙𝑑𝑖𝑛𝑔 𝑡𝑖𝑚𝑒(𝑏𝑢𝑠 𝑜𝑟 𝑟𝑒𝑠)
𝑡𝑜𝑡𝑎𝑙 𝑠𝑢𝑏𝑠𝑐𝑟𝑖𝑏𝑒𝑟(𝑏𝑢𝑠 𝑜𝑟 𝑟𝑒𝑠)∗1 ℎ𝑜𝑢𝑟
Terminating traffic per residential=0.66* Originating traffic per residential




The originating residential traffic (Aor) = 0.0384 E
The terminating residential traffic(Atr) = 0.0253 E
The originating business traffic(Aob) = 0.0644 E
The terminating business traffic(Atb) = 0.0425 E
In our project we have 6 big cities and 26 small cities , we associate each big city with the
nearest small cities . we obtain :
13
Also we devide our country into 3 zones .
14
After the calculations in each zone , we summarize the results in the following tables :
ZONE1
15
ZONE 2
16
ZONE 3 :
17
2. Switching
2.1




2.2
Switching overview :
The role of switching is to multiplex user channels together and enable subscribers of the
same area (belonging to the same exchange) to communicate together. In addition, it is
responsible for analog to digital conversion since the line from the subscriber carries an
analog signal and it has to be transmitted in a digital format to other switches.
Its name is derived from semiconductors materials that played a big role in the progress
of digital transmission. Semiconductors allow us to get rid of the thermal noise and
therefore the power will be zero (P = V*I = 0).
In Digital communication, we have known PCM as a coding technique converting an
analog signal into digital data or bits. This technique is adopted in PSTN network for
analog to digital conversion.
For multiplexing the channels, Time Division Multiplexing (TDM) technique is adopted.
Design of Switching system :
Zone 1 :
The capacity of transit Exchange = 7000 Erlangs
The transit traffic per zone = 7480.53654 Erlangs > 7000 Erlangs
So we need to use 2 transit switches per zone T1 , and TT1 .
Also the maximum CP load : 75 %
The CP load of A = 55.217084 % < 75 %.. then we need 1 local switch in A .
The CP load of C = 25.985383 % < 75 % .. then we need 1 local switch in C .
The maximum capacity of RSU : 2048 Lines and the links between LE and RSU : 3 E1/1000
lines. For each small city we need an RSU to connect with the local switch , we calculate the
18
number of RSU needed in each city , and we find the number of E1’s used in each small city (we
need 3 E1 for each 1000 lines )
The details are calculated in the zone1’s table described above .
These results let us know the data flow in zone 1 :
j2
p2
f2
we used a 70 % protection for each transit switch , so the LE – TE traffic going to T1 or TT1 are
equal to 70 % of the LE – TE traffic IN maximal .
and the LE – TE traffic coming from T1 or TT1 are equal to 70 % of the total LE – TE traffic out
maximal .
we are using a load balancing between the 2 transit switches T1 and TT1
Zone 2 :
The capacity of transit Exchange = 7000 Erlangs
The transit traffic per zone = 7921.48724 Erlangs > 7000 Erlangs
19
So we need to use 2 transit switches per zone T2 , and TT2 .
Also the maximum CP load : 75 %
The CP load of F = 29.232985 % < 75 %.. then we need 1 local switch in F .
The CP load of D = 58.465401 % < 75 % .. then we need 1 local switch in D .
The maximum capacity of RSU : 2048 Lines and the links between LE and RSU : 3 E1/1000
lines. For each small city we need an RSU to connect with the local switch , we calculate the
number of RSU needed in each city , and we find the number of E1’s used in each small city (we
need 3 E1 for each 1000 lines )
The details are calculated in the zone2’s table described above .
These results let us know the data flow in zone 2 :
x2
we used a 70 % protection for each transit switch , so the LE – TE traffic going to T1 or TT1 are
equal to 70 % of the LE – TE traffic IN maximal .
20
and the LE – TE traffic coming from T1 or TT1 are equal to 70 % of the total LE – TE traffic out
maximal .
we are using a load balancing between the 2 transit switches T2 and TT2
Zone 3 :
The capacity of transit Exchange = 7000 Erlangs
The transit traffic per zone = 7990.05152 Erlangs > 7000 Erlangs
So we need to use 2 transit switches per zone T3 , and TT3 .
Also the maximum CP load : 75 %
The CP load of E= 48.720596 % < 75 %.. then we need 1 local switch in F .
The CP load of B = 32.481302 % < 75 % .. then we need 1 local switch in D .
The maximum capacity of RSU : 2048 Lines and the links between LE and RSU : 3 E1/1000
lines. For each small city we need an RSU to connect with the local switch , we calculate the
number of RSU needed in each city , and we find the number of E1’s used in each small city (we
need 3 E1 for each 1000 lines )
The details are calculated in the zone3’s table described above .
These results let us know the data flow in zone 3 :
21
we used a 70 % protection for each transit switch , so the LE – TE traffic going to T1 or TT1 are
equal to 70 % of the LE – TE traffic IN maximal .
and the LE – TE traffic coming from T1 or TT1 are equal to 70 % of the total LE – TE traffic out
maximal .
we are using a load balancing between the 2 transit switches T3 and TT3 .
22
3.Intelligent Network : (Architecture, exchanges, type,
capacity..)
3.1 IN architecture:
I- Definition:
•
Intelligent Network (IN) :
IN is based on the existing PSTN network , it build on
overlay intelligent network , using computer technology , to control the
telecommunication network providing value added service.
• Originally, IN has been applied in telephone and voice services, but today its meaning is
also growing in the service integration of mobile and fixed telephone networks and as
gateway to Internet based networks.
Intelligent Network offers added value
•
•
•
•
•
•
•
•
Open standards, vendor independence.
Rapid service creation and deployment.
Customized services to users.
Centralized service management.
New opportunities to make business i.e. new services, markets and customers.
Rapid adaptation to market needs and competition.
Source of Competitive Advantage.
The Intelligent Network is a universal service platform providing:
– Service independence.
– Network independence.
23
2 .The main nodes that compose the IN platform are :
SSP: Service Switching Point
- provides user access to network (CCAF), trunk connection (CCF)
 Switching capabilities (local/transit exchange).
- contains mechanisms to detect IN services, to communicate with SCF
 Service switching capabilities.
SCP: Service Control Point
- contains service logic programs (SLPs) used to provide IN services.
- may access data in SDP directly or through SS No.7.
- is connected to IP via SSP relay function or through SS No.7.
SDP: Service Data Point
- contains data used by SLPs.
IP: Intelligent Peripheral
- supports flexible information interactions between user and network.
- Example of specialised resources: DTMF digit collection, tone generator, audio conference bridge,
customised voice announcement, voice/speech recognition devices, text to speech synthesis...
AD: Adjunct
- Functionally equivalent to the SCP but directly connected to SSP via a high speed interface.
SN: Service Node
- Functionally contains SCF, SDF, SRF and CCF/SSF.
SSCP: Service Switching and Control Point
- Functionally contains SCF, SDF and CCF/SSF.
SCEP: Service Creation Environment Point
- used to define, develop and test IN services.
SNAP: Service management Access Point
- provides service managers.
24
SMP: Service Management Point
- performs data base administration, network monitoring, network testing, network traffic management,
network data collection.
3.2 benefits of intelligent networks
The main benefit of intelligent networks is the ability to improve existing services and develop new
sources of revenue. To meet these objectives, providers require the ability to accomplish the following:




Introduce new services rapidly— IN provides the capability to provision new services or modify
existing services throughout the network with physical intervention.
Provide service customization—Service providers require the ability to change the service logic
rapidly and efficiently. Customers are also demanding control of their own services to meet their
individual needs.
Establish vendor independence—A major criterion for service providers is that the software
must be developed quickly and inexpensively. To accomplish this, suppliers must integrate
commercially available software to create the applications required by service providers.
Create open interfaces—Open interfaces allow service providers to introduce network elements
quickly for individualized customer services. The software must interface with other vendors'
products while still maintaining stringent network operations standards. Service providers are no
longer relying on one or two vendors to provide equipment and software to meet customer
requirements.
25
3.3 inportant IN services :
o Virtual private network: It is a network specific to a company (a telephone closed user
group with a specific telephone numbering plan) which is created for individual
corporate customers of the public network. The public network thus appears to the
corporate customer much as a private network with a ‘tailored’ company numbering
plan. There is a provision of private numbering plan and the call charging is on the basis
of duration of usage
o Free phone: The intelligent network converts dialed free phone number to standard
telephone number, allowing the SSP to complete the call set-up, while simultaneously
creating a call-charge record of the call receiver’s account.
o Premium rate service: The ability to charge a premium rate for calls besides the normal
telephone charges enables charging the caller for services such as weather information,
traffic information, etc. The extra charges collected are forwarded to the information
service provider.
o Tele-voting: This service is conceived to complement television games shows in which
viewers are invited to call different telephone numbers to register their vote for the best
participant.
o Universal access number service: This service enable the subscribers to publish a single
national number and have incoming calls routed to different destinations based on
criteria such as location, time and date of the call.
o Number Portability: The ability for a customer to change his telephone network provider
without being forced to change his telephone number is the basis of the number
portability service. The problems posed by changing number, otherwise dissuade change
of telephone network provider. Number portability is increasingly viewed as an essential
of competition among public telephone service providers.
o Universal personal telephone service: It is an extension of the universal number service,
allowing the customer not only to roam within the fixed telephone network, but also
connect to mobile telephones and other networks.
o Prepaid calling card service: This service enables card holders to make calls from any
telephone in the public network, by using a scratch card which represents certain amount
of prepaid charging units, invoicing call charges to their personal calling card account.
This card provides the user with specific amount of prepaid calling time. At the call setup, intelligent network verifies the card’s account number and requests caller’s
authorization by means of his personal identification number (PIN). To subscribe to this
service, which are sold on the market, trough various channels and points of sales.
26
The table below shows the paying party for every service:
IN services
Paying Party
Free phone service
Called party
Universal Access Number
Calling party
Virtual private network
Group ID authority
Pre-paid calling Card
Calling party through card
Premium rate services
Calling
Tele-voting charging to caller
Calling
Tele-voting not charging to caller
Called
Number Portability
____
Universal personal telephone service
Called
3.4 design of IN network
In our network , we will use :
1- The prepaid calling card service :
In our network , we have three type of people :
- residential subscribers
- business subscribers
- non subscribed people
the prepaid calling card will not be used by the business subscribers , but only by residential subscribers
and non subscribed people by a defined percentage :



15 % of residential subscriber
30 % of non subscriber
0 % of business
27
The following table determine the number of companies according to the number of subscribers
in each zone
local
A
B
C
D
E
F
Total
nb of
sub
101852
74055
52200
107581
91029
26736
453453
% of sub
0.224614
0.163313
0.115116
0.237248
0.200746
0.05896
1
nb of
companies
562
408
288
593
502
147
2500
The number of subscribers = number of residential subscribers + number of business
subscribers.
% of subscribers =( number of subscribers / number of business ).
Number of companies = % of subscribers * 2500 .
Now we will find the traffic out of the prepaid card service
= residential traffic + non subscribers traffic .
Originating traffic of non subscribers = Aor = 0.0384 E .
Traffic out = Aor * nb of persons ,
Note that number of persons = nb of residential using IN + number of non subscriber
using IN .
28
Now we will calculate the number of E1’s needed for non subscribers from each zone to SSP .
First we find traffic out of non subscriber = Aor * number of non subscriber uning IN * 0.2
Using B formula we find the number of lines .
The number of E1’s = number of lines / 30 .
So the total number of E1’s used for non subscribers = 63 E1
We will add this traffic to the traffic between transits .
2 free phone service :
We suppose that 15 % of the companies uses 5 free phone .
This service is used by business companies so we have Atb = 0.0425 E .
We suppose that each company uses 1 free phone then
Traffic = % of companies uses free phones * Atb
29
30
4. transmission
4.1 transmission overview :
Before describing the transmission section, let’s give a little description for some
characteristics of the signal that uses this section.
After the switching section, the signal that enters the transmission section is the PCM
signal.
What’s the PCM signal?
PCM means pulse code modulation
Analog
signal
S/H (sampler and holder)
Quantization
Coder
PCM
To block the aliasing, we can put a low pass filter before the S/H.
Let’s describe each device in this block diagram:
1- S/H: using shanon theorem, we can conclude that the sampling frequency must be more than
twice of the signal frequency.
Fs >= 2*Fm
As we know the voice frequency is limited between 300HZ and 3400 HZ
So for more security, Fs was been taken 8KHZ.
In the PCM signal, the two samples of the same signal are separated by 125μs.
31
1 sample (8 bits)
125 μs
64 kbits/s
1s
So for each customer, we reserve 64 Kbits/s.
2- Then, the next step is the quantization. In this step the sample takes a number by
approximation.
3- The final step to get the PCM signal is the coding.
Actually, we have many types of coding. Those types are:





RZ
NRZ
Manchester
Differential
HDB3( This the type used by OGERO)
Switch or Data network
Switch or Data network
DDF
DDF
TX
RX
Optical fiber cable
ADM
RX


ADM
TX
DDF: digital distribution frame
ADM: add drop multiplex (transmission equipment for multiplexing)
32
As we see, the transmission equipment is based on multiplexing. And the signal coming from
the switch to the ADM is an E1 (European system) signal.
So what’s the E1 signal:
We describe that each user is given 64Kbits/s, and the E1 signal is a group of 32 user of
64Kbits/s, so the rate of the E1 signal is:
64 K bits/s * 32 = 2,048 Mbits/s
In multiplexing, we have two methods:


TDM : time division multiplexing
FDM : frequency division multiplexing
4.2. Transmission network
In this part we are interested into two parts:
Transmission lines:
 fiber optics cables.
 Coaxial cables.
In this section, we have two types of hierarchy:


PDH Hierarchy.
SDH Hierarchy
PDH Hierarchy:
33
Drawbacks of PDH:
Whenever I need to Add or Remove an E1 at the stage of switches, we have to DeMultiplex and
then Multiplex all the E1’s in a hierarchal order, so this consumes time.
Repeatance, since same E1’s might be multiplexed and demultiplexed several times upon drop or
insertion including the E1’s that need not to be dropped or inserted.
If data passes by an exchange that is just on the path and not an end of the communication, this
exchange can’t just pass data through, it is obliged to demultiplex then multiplex it.
Multiplexing and DeMultiplexing several times weakens the signal and may introduce error bits
to the structure of signal.
SDH Hierarchy:
The original SDH standard defined the transport of 1.5/2/6/34/45/140 Mbps within a
transmission rate of 155.52 Mbps and is being developed to carry other types of traffic, such as
asynchronous transfer mode (ATM) and Internet protocol (IP), within rates that are integer
multiples of 155.52 Mbps. The basic unit of transmission in SONET is at 51.84 Mbps, but in
order to carry 140 Mbps, SDH is based on three times this (i.e., 155.52 Mbps [155 Mbps]).
Through an appropriate choice of options, a subset of SDH is compatible with a subset of
SONET; therefore, traffic inter working is possible. Interworking for alarms and performance
management is generally not possible between SDH and SONET systems. It is only possible in a
few cases for some features between vendors of SDH and slightly more between vendors of
SONET.
The standard rate for the SDH is the STM1(synchronous transport mode) which contains 63 E1,
that’s mean the standard bit rate is:
63 * 2.048 Mbits/s = 155 Mbits/s
34
STM1(first rate) : 63 * 2 Mbits/s = 155 Mbits/s (in 125 μs)
STM4(four STM1) : 4 * 155 = 622 Mbits/s (in 125 μs)
STM16(four STM4) : 4 * 622 = 2.5 Gbits/s (in 125 μs)
STM64(four STM16) : 4 * 2.5 Gbits/s (in 125 μs)
4.3 design of transmission systems :
4.3.1. transmission between zones :
We calculated in the first part the interzone traffic out and the interzone traffic in
from each transit .
Let :
Abi: number subscriber of the zone i (1≤ i ≤3).
Ti: number of outgoing E1 from zone i (1≤ i ≤3).
The following formula calculates the E1 transit traffic from zone I to zone j
𝑇𝑖𝑗 = 𝑇𝑖 ∑4
#𝐴𝑏𝑗
𝑘=1,𝑘≠𝑖 #𝐴𝑏𝑘
The number of subscriber of the zonez 1,2 and 3 are as follows :
Ab1
Ab2
Ab3
154052
134317
165084
35
 Traffic calculation of zone 1 :
𝐴𝑏2
𝑇12 = 𝑇1 ∑3
𝑘=1,𝑘≠1 𝐴𝑏𝑘
𝑇13 = 𝑇1 ∑3
= 67 ∗
𝐴𝑏3
𝑘=1,𝑘≠1 𝐴𝑏𝑘
134317
299401
= 67
= 31 𝐸1
165084
299401
= 37 𝐸1
 Traffic calculation of the zone 2 :

𝑇21 = 𝑇2
𝐴𝑏1
3
∑𝑘=1,𝑘≠2 𝐴𝑏𝑘
= 71
154052
= 35 𝐸1
319136
𝑇23 = 𝑇2
𝐴𝑏3
3
∑𝑘=1,𝑘≠2 𝐴𝑏𝑘
= 71
165084
= 37 𝐸1
319136
Traffic calculation of the zone 3 :
𝑇31 = 𝑇3
𝐴𝑏1
3
∑𝑘=1,𝑘≠3 𝐴𝑏𝑘
= 72
154052
= 39 𝐸1
288369
𝑇32 = 𝑇3
𝐴𝑏2
3
∑𝑘=1,𝑘≠3 𝐴𝑏𝑘
= 72
134317
= 34 𝐸1
288369
Results :
T1
T1
T2
T3
T2
31 E1
35 E1
39 E1
34 E1
36
T3
37 E1
37 E1
We know that :
Maximum capacity of an STM-1 = 63 E1
Maximum capacity of an STM-4 = 252 E1
Maximum capacity of an STM-16 = 1008 E1
T1-2 = max (T12, T21) = 35 E1.
T1-3 = max (T13, T31) = 39 E1.
The number of E1 out of the zone 1 is : 35 E1 + 39 E1 = 74 E1 > 63 E1
Then we need to use an ADM of type STM-4 .
T2-1= max (T12, T21) = 35 E1.
T2-3 = max (T23, T32) = 37 E1.
The number of E1 out of the zone 2 is : 35 E1 + 37 E1 = 72 E1 > 63 E1
Then we need to use an ADM of type STM-4.
T3-1= max (T13, T31) = 39 E1.
T3-2 = max (T23, T32) = 37 E1.
The number of E1 out of the zone 3 is : 39 E1 + 37 E1 = 76 E1 > 63 E1
Then we need to use an ADM of type STM-4.
The total number of E1’s used by the bus are : 74 + 72 + 76 = 223 E1 .
We add the number of E1’s used in the prepaid card service , we obtain the total number of E1’s
equal to 223 E1 + 63 E 1 = 286 E1 > 252 E1
We need to use an ADM of type STM-4 and an ADM of type STM-1
The backbone connecting each zone with the other zones is a bus connection , we use an SDH
and ADM to connect all the transit switchs , and we protect them with a 139 Mb/s PDH
microwave links .
37
T1
TT1
252
E1
252 E1
ADM
ADM
34 E1
34 E1
ADM
ADM
ADM
1 STM-4
1 STM-1
252
E1
ADM
34 E1
T2
TT2
T3
TT3
ADM
ADM
SSP
4.3.2. transmission inside each zone :
In this part we will describe the transmission between the local exchange and the transit
exchange , we will use a ring connection ,The ring connection means that all the E1 lines are
sent over all LEs in a ring or circular schema and in both directions.
We will use a ADM multiplexer .
We will use fiber optics , we will not make protection with microwave links because the ring
connection is protected .
We will find the summation of the incoming and outgoing E1’sand based on the determined
value we will decide what STM level to use or what conbination too use .
For transit T1 :
There are 2 local exchange A and C connected to the transit T1 .
Sum of incoming and outgoing E1’s = 0.7*(110+57+57+30)=178 E1
So we need 1 STM-4 connection .
The ring between T1 and the 2 local exchange A and C is described in the
following schematic :
38
T1
ADM
1 STM-4
178 E1
ADM
ADM
40
E1
77
21
E1
E1
40
E1
A
C
For transit TT1 :
There are 2 local exchange A and C connected to the transit TT1 .
Sum of incoming and outgoing E1’s = 0.7*(110+57+57+30)=178 E1
So we need 1 STM-4 connection .
The ring between TT1 and the 2 local exchange A and C is described in the
following schematic :
TT1
ADM
1 STM-4
178 E1
ADM
ADM
40
E1
E1
77
21
E1
E1
40
A
C
39
For transit T2 :
There are 2 local exchange F and D connected to the transit T2 .
Sum of incoming and outgoing E1’s = 0.7*(61+32+116+61)=190 E1
So we need 1 STM-4 connection .
The ring between T2 and the 2 local exchange F and D is described in the
following schematic :
T2
ADM
1 STM-4
190 E1
ADM
ADM
82
E1
E1
43
43
E1
E1
23
F
D
For transit TT2 :
There are 2 local exchange F and D connected to the transit TT2 .
Sum of incoming and outgoing E1’s = 0.7*(61+32+116+61)=190 E1
So we need 1 STM-4 connection .
The ring between TT2 and the 2 local exchange F and D is described in the
following schematic :
40
TT2
ADM
1 STM-4
190 E1
ADM
ADM
82
E1
43
43
E1
E1
23
E1
F
D
For Transit T3 :
There are 2 local exchange E and B connected to the transit T3 .
Sum of incoming and outgoing E1’s = 0.7*(99+51+80+42)=191 E1
So we need 1 STM-4 connection .
The ring between T3 and the 2 local exchange E and B is described in the
following schematic :
T3
ADM
1 STM-4
191 E1
ADM
ADM
56
E1
E1
50
30
E1
E1
36
E
B
41
For Transit TT3 :
There are 2 local exchange E and B connected to the transit TT3 .
Sum of incoming and outgoing E1’s = 0.7*(99+51+80+42)=191 E1
So we need 1 STM-4 connection .
The ring between TT3 and the 2 local exchange E and B is described in the
following schematic :
TT3
ADM
1 STM-4
191 E1
ADM
ADM
56
E1
E1
70
30
E1
E1
36
E
B
42
4.3.3 trasmission between local and RSU’s :
Now we will discuss the transmission between the local exchange and the RSU’s.
For Local exchange A :
We use PDH equipment on fiber in a loop connection. The total line send to the first city
“j” is 38 E1, so we use PDH 139Mbps for the total, then each village takes its lines and sends
the rest over PDH according bit rates, if less than 34 Mbps we use 34Mbps PDH, and if not we
use 139Mbps PDH.
38 E1
139
139
31 E1
139
139
25 E1
139
139
18 E1
139
c1
j2
b
139
31 E1
139
f1
139
139
25 E1
38 E1
139
j1
c2
139
139
139
31 E1
139
q1
139
q2
139
19 E1
139
34
139
o1
19 E1
C
139
7 E1
139
43
34
p1
o2
34
7 E1
31 E1
34
a1
34
For local exchange C :
139
10 E1
a2
f2
18 E1
A
34
p2
34
10 E1
139
34
For Local exchange D :
139
34
34 E1
139
D
l
139
139
139
28 E1
139
m1
34
m2
16 E1
n1
34
n2
n3
1
4E
139
34
16 E1
28 E1
34 E1
34
139
34
k
The village k is very far so we connect it to the LE with a microwave connection using PDH 39
Mb/s .
For local Exchange F :
We use PDH equipment on fiber in 2 loop connection. The total line send to the first city “d” is 23
E1 in first loop and The total line send to the first city “i” is 23 E1 in second loop, so we use PDH
139Mbps for the total, then each village takes its lines and sends the rest over PDH according bit
rates, if less than 34 Mbps we use 34 Mbps PDH, and if not we use 139 Mbps PDH.
44
For local exchange E :
34
34
t2
11 E1
22 E1
E
34
34
34
139
6 E1
v
139
34
139
4E
34
34
s
For local exchange B :
45
34
r
1
34
139
22 E1
t1
11 E1
6 E1
34
34
e1
34
e1
16 E1
e1
34
23E1
139
34
e2
139
23E1
139 139
B
139 139
43 E1
g1
43 E1
e1
16 E1
139
139
g2
139
46
30 E1
g3
139
i1
139
30 E1
34
139
i2
139
20 E1
h1
139
20 E1
139
h2 h3
139
h4
5. Financial Study
Objective:
 The objective is to determine the total costs of the established network , to
define the tariffs and finally to give the scale of charge that will lead us to get
our money back in 4 years .
Equipment price:
 Transit exchange : 400 MU/E.
 Local exchange: 30 MU/line ( RSU included )
 SDH STM-4: 120000 MU/unit.
 SDH STM-1: 35000 MU/unit.
 PDH : 150 MU/2 Mbits/s.
 +50% of price of transmission for the FO and MW.
 +40% of the total price of local loop.
 +6% of total network price for IN platform.
 +7% or O&M (TMN) per year.
 Mean holding time per subscriber per day= 10 min ( residential ) , 25 min (
business).
 +10% of the revenues added as income from international calls.
 Four years network damping.
 40% of the installed lines in the first year , 30% in second year and 20% in
the third year and 10% during the last one.
1. Network cost:
A-Prices of switches:
The price of the layer of communication is the sum of the price of transits and the
local switches.
 Transit exchanges cost
The cost of transit depend on the number of swiches used .
In our project we are using seven switches, one oh them used to the intelligent
network ,each switch have a capacity of 7000 𝜖 .
Cost of transit exchanges = 7*7000*400=19600000 MU.
 Local exchanges cost:
47
It is pointed out that we have 6 local switches and that the price of this kind of
switch depends on the number of lines (30 MU/lines). However each line
corresponds to only one subscriber. Thus the total price of each switch is worth 30
* the number of subscribers=30*482101=14463030 MU.
the total price of the switches is equal to the sum of the transit and local switches:
19600000+14463030=34063030 MU.
B-Transmission cost:
The price of transmission is the sum of the prices of BACKBONE, RINGS, LOOPS
and FO&MW.
One will then determine the price spent on the BACKBONE then on the BOXING
RINGS.
a. BACKBONE:
In this layer, one is interested in the transits. We used 8 SMT-4 and 8 STM-1 .
 4 SMT-4 and 4 STM-1 for the bus connection
 4 SMT-4 and 4 STM-1 for the microwave backup connection.
The total price is: 8*120000+8*35000=1240000 MU.
b. RING:
In the “rings”, we still use equipment SDH. Thus the price of each ring depends on
the type of the node SDH which one will use (STM-1 or STM-4).
In our project, there are 6 rings STM-4 in each one 3 ADMs.
Total SDH price: 6*3*120000=2160000 MU.
c. Loop cost:
We used PDH to connect LEs to RSUs in Loops or junctions:
36 PDH 139Mbps
32 PDH 34 Mbps
The total price is = 36*(139/2)*150+32*(34/2)*150
= 36*69.5*150+32*17*150=456900 MU.
The Total transmission cost is: 1240000+2160000+456900=3856900 MU.
48
C-Equipments cost:
 Fiber optics and microwaves cost:
The price of the links between the equipments(F.O. & M.W.)
Given the price of the links equals to 50% of the price of the transmission
equipments.
Price of Fo & MW = 0.5*price of transmission
=0.5*3856900
=1928450 MU.
 Local loop cost:
The price of the local loop is given as 40% of the total price.
Total price =34063030+3856900+1928450=39848380 MU.
Local loop price = 40%*total price
=0.4*39848380
=15939352 MU.
 New total cost of the network
The total price of the network=34063030+3856900+1928450+15939352
=55787732 MU.
 IN cost:
The price of IN platform is 60% of the total cost of the network.
IN cost = 0.06*55787732=3347264 MU.
 New total cost of the network = 55787732+ 3347264= 59134996 MU.
 TMN cost :
 First year:
0.07*0.4*59134996 = 1655780
 Second year: 0.07*0.7*59134996 = 2897615
 Third year: 0.07*0.9*59134996 = 3725505
 Fourth year: 0.07*1*59134996 = 4139449
The cost of management and operation of the network , At the end of the four
specified years is: TMN=0.07*(0.4+0.7+0.9+1)* 59134996=12418349 MU.
Thus the price total of the network which the operator must cover after four years
is the sum of the cost of maintenance and operation during the four years with the
price of the network: Total network price =12418349+59134996=71553345 MU.
49
2. TARIFFING:
In this part, we will determine the cost of installation, inscription monthly
magazine, and the tariff of a call. Moreover we will offer to the subscribers some
services IN, it is then necessary to define their tariffs.
Tariffing must be done in a way to have after four years an income able to cover
the total costs of the network.
1. Calculation of the income:
The income in our project comes from the several types of income:
 National
 Inscription
 Price of installation
 Returned of the intelligent network.
Conversation in the first 4 years:
We suppose that M is the price of a minute of subscriber’s conversation.
We have to calculate the total number of spent minutes in conversation:
% of installed lines * (business subscriber x Mean holding time per subscriber per
day + residential subscriber x Mean holding time per residential subscriber per
day) * number of days per year.
First Year: 0.4 x (137278 x 25mn + 344847 x 10mn) x 365 = 1 004 541 320 mn
Second Year: 0.7 x (137278 x 25mn + 344847 x 10mn) x 365 = 1 757 947 310 mn
Third Year: 0.9 x (137278 x 25mn + 344847 x 10mn) x 365 = 2260 217 970 mn
Fourth Year: 1 x (137278 x 25mn + 344847 x 10mn) x 365 = 2 511 353 300 mn
2. National income:
total number of min =1004541320+1757947310+2260217970+2511353300
=7 534 059 900 mn.
the income from minutes spoken during the four years
is : 7 534 059 900*M.
3. Monthly subscription income:
Assume that S is the cost of a month subscription. In the first year, subscribers will
pay 48 subscriptions in 4 years. In the second year, subscribers will pay 36
subscriptions in 3 years. In the third year, subscribers will pay 24 subscriptions in
2 years.
In the fourth year, subscribers will pay 12 subscriptions in 1 year.
Then the total revenue of subscription will be:
50
Total revenue of subscription =
total subscx40%x4yearsxS + total subscx70%x3yearsxS + total
subscx90%x2year1xS + total subscx100%x1yearxS =
482101*0.4*S*12 +482101*0.7*S*12 +482101*0.9*S*12 +482101*5*S*12 =
17355636 S = T2
4. Income of installation:
Assume that INS is the income from installation then the total income is:
482101*INS
5. Income from IN network:
In our project we have 3 services: prepaid calling card, universal access number
and free phone.
a. Prepaid calling card service:
Tariff/min:
National=2*M
International=7*M
Local GSM=6*M
Card Price=200*M
We suppose that we have 15% of our residential subscribers and 30 % of non
subscribers that take this service each year.
In 3 years we get as revenue from this service:
Revenue from this service=
(0.4+0.7+0.9+1)*(0.15*residential+0.3*nonsubscribers)*6*200*M=189988794
0*M
b. Free phone service:
Tariff/min=M
Initial fees per year=I
Monthly Subscription=4*S
We have 2500 company in our country; we suppose that 375 company take this
service each of the 4 years, but only 40% of the company take this services for
the first year and 70% in the second year, in the third year 90% of the company
51
take this services, finally in the fourth all the company that need to take this
services take it.
Each year the company must pay all the subscriptions (in each month) and the
initial fees if it wants to renew or to newly subscribe in this service.
Cost paid by each Business company that take this service=
(0.4+0.7+0.9+1)*((12*4*S +I )*nb of company+ residential subscribers * Mean
of % of residential subscribers that use this service per year*Mean number of
minutes talked every day per each subscriber *M*365)
We have supposed that:
Mean of % of residential subscribers that use this service per year is 65%
Mean of Number of minutes talked every day per each subscriber 4 minutes
As operator, we share 55% of the cost paid by these companies.
Our total Revenue from this service=375*The cost paid by the company +our cost
sharing with this company =[375*3*(12*4*S +I ) +0.55*residential subscribers *
0.65*4*M* 365)]=54000S+1125I+179992891.7M
Total IN revenue:
Adding up all IN revenue we obtain a total of: 40500S+1125I+1089641840M
Total revenue = National income + subscription income + income installation +
income IN
=7 534 059 900*M+17355636 S+ 482101*INS
+54000S+1125I+179992891.7M
= 7714052792M + 483226 I + 17396136 S
This must equal the total cost 71553345 MU.
52
We suppose that I=20S, and we propose a cost of month conversation equals to a
4 times the monthly subscription, then we get M*Mean number of minutes used
by a subscriber in a month=4*S
o
o
o
M*30*(residential subscriber* Mean holding time per subscriber
per day for residential subscriber+ business subscriber* Mean
holding time per subscriber per day for business subscriber) = 4*S
S=107*M
I=2140,65*M
Then the total IN revenue = 7714052792 M +483226*2140.65 M + 17396136
*107M =
= 10609857080 M
0.1of the total IN revenue is a international calls so :
Replacing each term we obtain: 10609857080 M * 1.1 =71553345 MU
o.1 of the total
then M = 6.13 * 10^-3 MU
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6. NEXT GENERATION NETWORK (NGN)
6.1. NGN Functional Architecture
The ▲NGN architecture as defined by the ITU
and ETSI
borrows heavily from the
work done by ▲3GPP. The diagram below shows the architecture that has been defined for the
NGN in ITU-T Rec. Y.2012.
NGN Architecture
According to Y.2012, the NGN architecture supports the delivery of multimedia services and
content delivery services, including video streaming and broadcasting. An aim of the NGN is to
serve as an ▲PSTN and ▲ISDN replacement.
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The NGN architecture defines a Network-Network Interface (NNI), User-Network Interface
(UNI), and an Application Network Interface (ANI). The Transport stratum provides IP
connectivity services to NGN users under the control of Transport control functions, including
the Network Attachment Control Functions (NACF) and Resource and Admission Control
Functions (RACF).
The NACF and RACF are two components of the NGN. A more detailed component view of the
NGN is shown in the following figure:
NGN Components
Terminals that talk to the NGN will authenticate with the Network Attachment Control Functions
(NACF), receive an IP address, get configuration information, etc. Once attached to the network,
terminals will communicate directly or indirectly with the Resource and Admission Control
Functions (RACF) in order to get desired QoS for communication, get permission to access
certain resources, etc.
There are a number of components within this architecture which would suggest a "freedom of
services" to users. Users would potentially have access to RTSP-based streaming services, PSTN
access, ▲IMS access, and access to "other multimedia components". In this author's opinion,
the very fact that these components are listed as the components of the NGN suggests that the
service providers behind this effort wish to have too much control.
Note that "legacy" terminals (user devices) must pass through a ▲gateway device. Perhaps this
makes sense for legacy PSTN equipment, but what about newer IP devices? Are all ▲IP devices,
by default, NGN devices? They are not, according to those trying to define the NGN. So, what
are IP devices we use today? Are they exclused from the NGN or locked into tight control with
55
limited access? It would seem so, suggesting that the NGN is at odds with the Internet and a
threat to the Internet as we know it.
The IMS layer, while certainly suitable for wireless networks, is very much a restrictive
component within any kind of "next generation" fixed network. Below is a diagram that shows
the functional architecture of the NGN with interfaces to the various functional elements.
IMS Functional Architecture Model
The primary purpose of IMS is to provide control over telephone calls. In a "next generation"
network, why would it be that the access provider would, in any way, try to specify how the
phone system internals should function? According to ITU-T Rec. Y.2001, access and service
should be separated and IMS really has no business being a core part of the NGN. You can look
at IMS as nothing more than a means of maintaining the current legacy telephone company
business model of counting minutes and charging for minutes of use. That kind of business model
is dated and needs to be replaced with something more forward-looking.
The only interesting aspect of the NGN architecture as proposed by the ITU and ETSI is the
"other multimedia" components. Through these components, it might be possible to truly deliver
a new kind of network that users may find useful. The NASS and RACS layers are quite
reasonable, as access to the network must necessarily be controlled. However, once network
access is granted, the kinds and types of services accessible to the user should be virtually
unlimited (though that does not equate to "free", understand). Through the "other multimedia"
components, it might be possible for terminal equipment manufacturers to provide equipment
that might deliver the services that users expect today, as well as new kinds of services that users
might want.
In fact, the ITU has initiated work on a new multimedia system called ▲H.325, which promises
to deliver on the promises of the NGN. Specifically, H.325 will allow a user to use multiple
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devices togther with multiple applications in order to communicate with another person. As the
system is envisaged, any application developer could create an application that simply "plug in"
to the H.325 terminal. The user could, for example, use a mobile phone to talk on a phone, see a
video feed on an LCD screen, collaborate on a document through a PC ("screen sharing" or
"application sharing"), and receive a file to a mobile handheld device, all within the context of a
call to another person. The possibilities are amazing.
A very important distinction between the work on H.325 and IMS is that H.325 is designed to
work on the Internet as it is today. Look at H.325 as a big step forward in terms of
communication capabilities, without all of the complexity of the NGN architecture.
6.2.
NGN Components
NGN architecture breaks the hierarchy-based architecture of the Traditional
Networks and advocates flat hierarchy for the NGN network.
1. Network Elements
 Converged IP/ MPLS Core (Soft switch/ media gateway controllers)
 Intelligent Provider Edge (PE) devices for service enablement (media gateway)
 Ethernet based Access infrastructure to aggregate business and residential users
 Diverse set of access architectures in the last mile
 Home gateway or CPE
2. Service Control Elements
 Policy Control Framework for subscriber policy tracking and enforcement
 Application level policy enforcement
 ‘AAA’ servers for billing and accounting & Authentication
3. End User Devices (CPE)
 Converged devices can be intelligent TVs, combined Mobile/ PDA/ Pocket
PC/IAD
6.3. The migration to PSTN
 NGN Relevance for different service providers
Migration to NGN has different implications for fixed line operators, mobile operators, cable
television operators, Internet Service Providers, software and hardware vendors etc. Each of
them sees a different combination of these benefits and risks. The implication of the move to
NGN is clear from the ITU definition: “NGN is about multi-platform access and a network
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where service provisioning is independent of the underlying network”. This definition suggests
that there is a role for multiple players within the NGN context.
These could potentially include:




Fixed telecom operators, both incumbents and new entrants;
Mobile telecom operators. especially in the 3G environment;
Internet Service Providers;
Cable television operators, which in some countries have greaterhousehold penetration
than fixed telephony, like in India, at present;
 Other value-added service providers, operators across multiple access technologies,
VSAT operators and other service providers (OSP);
 Vendors for both infrastructure and Customer Premises Equipment.
 Timing for migration to NGN
 Full steam ahead: BT’s 21CN project is the most prominent example of an early, rapid
and inclusive upgrade program. The test is whether or not an operator has announced
plans to retire their public switched telecoms network (PSTN). BT, TelekomAustria, NTT
and KPN all have plans to switch off some or all of their PSTN over the period to 2009;
 Gradual with narrower scope: Operators can take limited steps towards a core NGN
upgrade, for example by using IP for transport in the core PSTN. This is a low-cost, lowrisk move, but with few benefits other than the learning process. In contrast the
retirement of the PSTN, which implies the removal of the installed circuit switches, is a
much more risky project, but can provide significant cost savings. Operators in this
category are Telecom Italia and TeliaSonera;
 Wait and watch: Incumbents may choose to postpone any core NGN program, waiting to
see how other operators succeed with their projects, and avoiding the teething problems
of early NGN.
 Timeframe for migration
The general view from the initial feedback obtained from major operators is that the transport
backbone is nearly ready and service layer should be ripe for transition next year. The service
layer requires far less investment compared to other layers and offers scope to roll-out new
services viz. voice, messaging, gaming, mobility, IPTV etc., thus offering operators a chance to
reap their NGN investment. The transition to NGN access takes the most time because of the
following factors:



Of all the layers, access migration is most capital intensive;
With low PC and broadband penetration, there is limited drive to extend rollout
beyond the metros and major cities;
Low-cost Customer Premises Equipment/ non-PC-based IP terminals will be
needed to make a viable business case for NGN migration in the access layer.
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The issue for consideration in this regard is the likely time frame for a country to achieve
complete migration to NGN core. In what timeframe is the migration in other layers like access
and service layer likely to be achieved? What could be the NGN migration time frames in urban
and rural areas?
 Regulatory Initiative
Regulatory clarity can help reduce risks for operators and help make the transition less difficult.
Most operators believe that the transition to NGN is the single largest investment and business
change they will be making. On the other hand, regulatory intervention in the developing NGN
environment has the risk of delaying innovation, because services and business models are not
yet established in the market. A body such as ICANN, an international body, which manages the
Internet domain names and addresses, believes that regulation could kill innovation in the NGN
context.
It is indeed true that both operators and regulators must understand clearly the risks and the
benefits involved with NGN regulation. However, they cannot make informed choices based only
on a theoretical understanding of the technology and economic conditions in which the new
networks, applications and service-packages will operate. The issue is about whether and why
there is a need for regulatory initiatives within the NGN context.
“Light Touch” Regulation in the NGN Context: Regulators across the world are looking to move
away from detailed ex-ante regulation to “light-touch” that focuses on the main principles and
leaves specific compliance to “ex-post” activities and general law relevant to the sector.
However, internationally, views are split on the issue of “light touch” regulation. One view,
mainly expressed by operators in Europe and Far East Asia is that the transition to NGN is a
complete shift in the business model for telecom industry moving away from a well-established
practice of charging by time and distance (miles and minutes) to charging by capacity and
quality of service.
Telecom operators are becoming media companies and vice-versa. Third-party service providers
are able to provide services to customers connected by telecom operators without much revenue
accruing to the network infrastructure provider.
 Establishing Viable Competition
There are two related but contrary competition positions that can develop within the NGN
context:
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(a) Service-level competition: Open services access can result in the situation where third-party
service providers are able to ride on a telecom operator’s network to directly serve customers.
This can result in intense service-level competition (e.g. customer being able to buy services
from many IP telephony providers or television/education/gaming providers that are
independent of the network operator). There is a possibility that in this scenario, network
operators see themselves becoming pure connectivity providers and thus suffering a huge
erosion of revenues. Network operators are basing their NGN business plans on some estimation
of service revenues and cost, and such an open service scenario could well make their business
unviable.
(b) Network-level competition: NGN offers the most benefits to those with the largest scale; for
example, BT estimates annual Opex benefits of £1b on a Capex incurred of £3b-£4b; benefits to
competitive operators estimated to be about 20 per cent of BT’s. Incumbents also gain immense
advantage in being able to dictate the transition plan for the entire industry; as typically
upwards of 50 per cent termination occurs on the incumbent’s network. The incumbent has the
maximum clout in terms of deciding the network specifications; functions within the service layer
and on the nature of interconnection products to be offered in the NGN context. Access-level
competition will prove to be the most difficult in the non-local loop-unbundling environment.
One way to get over this problem is to offer incentives to alternate access paths (cable television,
WiMax, power line).
6.4 Advantages of NGN
NGN makes use of best of both the worlds (flexibility, efficiency & Innovativeness of IP and
QOS, Security, Reliability, Customer-friendly features of proven PSTN
•
Advantages for service providers
 Reduced CAPEX due to integrated and efficient IP-based technology (Packetized
Network)
 Reduced OPEX due to transmission cost saving, less power consumption, less
space requirement, less O&M costs
 Ability to offer increased range of services
 More flexibility increasing market penetration by offering personal service
customization and management
 Single network layer for management
 There is no need for separate voice and data networks
•
Advantages for subscribers
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 Reduced call charges
 New innovative services
 Single connection and bill for voice, data, video, mobile (Quad play)
 Better QoS
 Faster speed
 Availability of BW on Demand
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7. Conclusion
At the end of our project and after all the studies we have done .Our study is only theoretical, i.e.
it is difficult to realize this kind of network practically because there’s no enough details about
the country (geographical notes, annual population rate,…..)
Add to this, in our studies we respect the evolution of technology i.e. in some cases our need is
only by two or more STM-1 but we put a STM-4 taking in consideration the feature subscriber
and for the data network proposed (high bit rate).
Concerning the bill, considered that the cost of the minute is constant, but in reality the cost of
the minute must not be constant. To encourage the subscribers a certain offer must be done. We
know that phone is not used 24 hours a day, the usage of the phone according to the day time
differs from the usage of the phone during the night time. That distribution is shown in the
following figure:
So to improve that figure an offer is done like a night schedule that will be make a 50% discount
for example from 10:00PM to 2:00AM. And increase the cost of the minute during the day time.
That will cause the subscribers to use the lines equally during the day, thus enhancing the
distribution of the usage of the phone to the following figure:
This study is done to decrease the congestion of the lines during the day time.
Finally, we can say that the results are acceptable and realizable.
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