PTCL is Pakistan's largest telecommunications company. The internship report summarizes the author's 6-week internship at PTCL working in various departments including OFAN operations, switching operations, wireless operations, and transport network operations. The report provides an overview of PTCL's history and operations, and describes concepts learned about optical fiber networks, switching technologies, wireless local loop systems, and next generation networks.

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INTERNSHIP REPORT
SWITCHING, OFAN, TRANSIT,WLL,TRANSPORT
PAKISTAN TELECOMMUNICATION COMPANY LIMITED, ISLAMABAD.
Submitted By: Allah bux
Department of Electrical Engineering
Grafton university college , Islamabad

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Introduction:
Every year, many final year undergraduatestudents across Pakistan takepart
in summer internships organized and supervised by various organizations in
the country.
This document presents an internship reportat PTCL (Pakistan
Telecommunications limited). A brief history and information of the
organization is also included in the report.
Background:
The company traces its origin from the Posts and Telegraph department
established in 1947. Itwas later renamed Pakistan Telegraph and Telephone
department in 1962. In the early 90’s it became Pakistan Telecom Corporation.
PTCL became a public listed company in 1996. Etisalat acquired 26% PTCL
shares in 2006.
PTCL headquarters is located in Sector G-8, Islamabad, and has over ten
regional headquarters throughoutthe country.
Today PTCL is the largestfixed line telecommunications serviceprovider in the
country. PTCL services include Landline and Wireless Telephony, Broadband
and 3G internet, IPTV, Homesecurity (I Sentry).
Every year many of the students come across the country for internship at
PTCL. Engineering and computer science students usually work in the
Networks and Operation division. There are many departments under this
division.
The duration of this internship was 6 weeks, from 11 July 2016 to 26 august
2016. Theinternship was in the following departments:
 OFANOPs (2 Weeks)
 Switching OPs (1 Week)
 Wireless BSS OPs(1 Week)
 Transit North (1 Week)

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 TransportNetwork OPS(1 Week)
As PTCL is categorized in four main departments, which are as under;
I. Operating & Management System
II. Transmission
III. OFAN
IV. Switching
Conceptslearntindifferentdepartments
 oFAn
PTCL has laid optical fiber Access network in the major metropolitan centers
of Pakistan and it has modernized and upgraded the local loop services from
copper to optical fiber network.
PTCL Broadband, now available with new value added WiFiServices
Regarding the construction of optical fiber access network, access system
device occupies morethan 50% of the gross investment.
Research and Markets: China Optical Communication Industry Report, ...
The Lucent Automated Cross Connect(AXC) enables serviceproviders to
establish high-bandwidth services over copper and optical fiber access
networks withouthaving to send field technicians to remote terminals or
street cabinets, a time-consuming process which represents a significant
portion of a serviceprovider's operating expenses.
Optical fiber works by converting electrical signals into light of specific
wavelengths. The light is then transported through a special cable.
The cable consists of a core, cladding, and a buffer coating. The core is the
innermostregion through which light is transported. Cladding is used to
prevent the light fromleaking. Itinternally reflects any light coming out of the
cable. The picture below shows a basic structureof an optical fiber cable.

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The following types of networks can be established using optical fiber:
 Point – to – point Network
 Point-to-Multipoint Network
 Ring Network

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 Mesh Network
 Composite network

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 Advantagesoftheopticalfiber cables:
Optical fiber cables are not affected by any interference originated from
energy transmission lines. Radio waves and cross talk between the fibers does
not exist. No special protection is necessary.
1. Non Conductivity
No grounding is necessary becauseof metal free cable.
2. Large Wide bandwidth
Suitable for high speed. Wide-band, telecommunication lines.
3. Low Loss:
Because of Low few or no amplifiers are necessary.
4. Very Light Weight
The smallest cables can be designed and manufactured thereforereduce
pulling strength and reduce laying cost.
5. Economic
The most economical solution for the simultaneous transmission of several
multichannel users.
6. Low Attenuation
7. NoCross Talk
8. Many channel Capacity
9. Easy Installation
 Switching
A telephone exchange is a telecommunication system used in the PSTN or in
large enterprises. An exchange consists of electronic components and in older
systems also human operators that interconnect (switch) telephone subscriber
lines or virtual circuits of digital systems to establish telephone calls between
subscribers
There are two main types of switching, which are as under;
1.TDM

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a) EWSD(Siemens)
b) ZXJ-10(ZTE)
2.Soft Switches
a) C5(Huawei)
b) HCTE(Huawei)
 TDM:-
Introduction:-
Time-division multiplexing (TDM) is a method of transmitting and receiving
independent signals over a common signal path by means of synchronized
switches at each end of the transmission line so that each signal appears on
the line only a fraction of time in an alternating pattern. It is used when the
data rate of the transmission medium exceeds that of signal to be transmitted.

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 Soft Switches:-
Introduction:-
SoftX3000 is applicable to the network control layer of NGN and
implements call control and connection management of voice, data and
multimedia services based on the IP network.

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There are 7 different kinds of switching technologies currently operational in
PTCL network.
 Alcatel
 Siemens
 NEC
 Ericson
 Huawei
 J.S telecom
 ZTE
With these different switching technologies PTCL is running its huge
network and providing differentcommunication facilities to its
customers.
 ModesofSwitching
There are two modes of switching.
 Circuit Switching
 Packet Switching
Circuit switching includes mobile services. Itis not reliable as compared to
packet switching. Packetswitching includes mail via internet, mobile messages
etc. It is reliable mode of switching.
 NGN (NextGenerationNetwork)
Introduction:
A next generation network is a packetbased network that can be used for both
telephony and data that supportmobility. Initially, the term next generation
network is used to refer to the transformation of the core network to IP.
Sometime a NGN is referred to as all IP network.NGNare based on internet
technologies including internet protocoland multi-protocol label switching
(MPLS). Circuit Switching is the oldest and most commonly used switching

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technique used in telephony. However there are serious drawbacks of circuit
switching such as:
- Bandwidth inefficiency
- Difficult to maintain
- Connection set-up delay
To address the above problems, Packetswitching came into use. A packet
switched network does not requirea dedicated path. The packets can follow
different routes; hence utilize the bandwidth more efficiently.
NGN (Next Generation Networks) was developed as a packet switching method
to transportVoice, Video, and Data using a single network. Some advantages
of a NGN network are given below.
- Better Bandwidth utility
- Voice, Video, Data on a single network
- Easy management froma single location
- Reliability i.e. lost packets can easily be detected and be requested
again.
- Resilience i.e. if one network link fails, an alternate link can be used
PTCL uses the Huawei C5 NGN network. HuaweiSoftX3000 cardsareused to
manage voice, video and data services on the NGN network.
The NGN controllayer consists of the following SoftX3000 Boards
 Packet-based transfer
 Separation of control functions among bearer capabilities, call/session,
and application/ service
 Decoupling of service provision from network, and provision of open
interfaces
 Supportfor a wide range of services, applications and mechanisms
based on service building blocks (including real time/ streaming/non-
real time services and multi-media)
 Broadband capabilities with end-to-end QoS and transparency.
 WLL(WirelessLocalLoop)

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Introduction
• WLL is a system that connects the subscribers to the PSTN using radio
system as a substitute for the copper for all or part of the connection
between subscriber and switch.
 AdvantagesofWLL
1. Cost of installation and maintenance of WLL is lower than cable network
2. Installation time is less in case of WLL
3. Selective installation: Installation for thosewho requireconnection at a
certain time
4. Quality of wireless technologies have improved to nearly equal the
contemporary wired options which do face problems like longer distances
in xDSL and lack of infrastructure, so WLL offers tough competition
5. Cellular systems aretoo expensive with lesser signalquality than fixed
broadband wireless which uses directional antennas

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 WLL SYSTEMTECHNOLOGIES
1. Analog cellular
2. Digital cellular
3. Personalcommunications services / network (pcs/pcn)
4. Digital cordless systems
5. Proprietary implementations
 Transport
 SDH
SDH (Synchronous Digital Hierarchy) is a standard technology for
synchronous data transmission on optical media. It is the international
equivalent of Synchronous Optical Network. Both technologies provide faster
and less expensive network interconnection than traditional PDH
(Plesiochronous Digital Hierarchy) equipment.
SDH uses the following Synchronous TransportModules (STM) and rates: STM-
1 (155 megabits per second), STM-4 (622 Mbps), STM-16 (2.5 gigabits per
second), and STM-64 (10 Gbps).
 PDH
The plesiochronous digital hierarchy (PDH) is a technology used
in telecommunications networks to transport large quantities of data over
digital transport equipment such as fibre optic and microwave
radio systems. Theterm plesiochronous is derived from Greek plēsios, meaning

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near, and chronos, time, and refers to the fact that PDH networks run in a state
where different parts of the network are nearly, but not quite
perfectly, synchronized.
 Advantages of SDH over PDH
 INTERFACE
 Electrical interfaces
 SDH provides a set of standard rate levels----STM-N.
(N=4n=1,4,16,64……).
 The basic signal transmission structure level is STM-1, at a rate of
155Mb/s.
 Optical interfaces
 Optical interfaces adopt universal standards. Line coding of SDH
signals involves scrambling, instead of inserting redundancy codes
 MULTIPLEXING METHOD
 Low-rate SDH signals → high-rate SDH
 Signals via byte inter leaved multiplexing method
 PDH signals → SDH

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 Synchronous multiplexing method and flexible mapping
structure
 DWDM (Dense WaveDivisionMultiplexing)
An optical technology used to increase capacity over existing fiber
cables. It transmits multiple signals simultaneously at different wavelengths
on the same fiber. That is one fiber is transformed into multiple virtual
fibers.
Different signals with specific wavelengths are multiplexed into a fiber for
transmission.
 AdvantagesofDWDM
1. Transparenttransmission
2. Long haul transmission
3. High capacity
4. Use existing optical fibers
5. High performance-to-costratio
6. Reliability
7. Easy up-gradation
 SDH Network–NETypes
1. Regenerator(REG)
2. Terminal Multiplexer(TM)
3. Add/Drop Multiplexer(ADM)
1. Regenerator
Regenerator has the job of regenerating the clock and amplitude
relationships of the incoming data signals that have attenuated and

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distorted by dispersion The regenerator replaces the RSOH bytes before
re-transmitting the signal.
2. Terminal Multiplexer
Terminal multiplexers are used to combine plesiochronous and
synchronous inputsignals into higher bit rate STM-Nsignals.
2. Add / Drop Multiplexer
PDH and SDH signals can be extracted from or inserted into high speed
SDH bit streams by means of ADMs.
 TRANSIT
A switch or a telephone exchange has a basic task to perform -
switch communication paths. Now, the switch could be one that has
subscribers connected to it. You must be saying, all switches havesubscribers
connected to them. The point is, there are switches in any telephone network,
that do not havesubscribers connected to them. Instead they have other
switches connected to them. So, in a sense, this switch is 'a switch of switches',
performing switching for various other switches which may or may not be
directly connected to each other. So why is this done ? The answer to this is an
extension of our justification for the need for switching in the first place. It
goes like this.
A TransitExchange unlike a LE (Local Exchange), does not havesubscribers
connected to it and therefore does not act as a sourceor sink for traffic in the
network. Itonly collects and redirects the traffic among local exchanges.

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There are four main switches/exchanges in PTCL(Pakistan
Telecommunication limited) , which are listed as under;
1. Remote Exchange
2. Local/Main Exchange
3. TransitExchange
4. IGE(InternationalGateway Exchange)
 INTERNSHIPTASKS
1. I was assigned a task in the NGN department during the firstweek of the
internship. The task was to update the existing record of wire colors of ADMs,
which are used for E1’s. E1’s area way to transfer data and signaling between
two different exchanges. Every E1 has 32 channels. 30 channels are for voice
data, one is for synchronization and one is for timing. Each voice channel can
carry data at a maximum rate of 64kbits/s. Voiceconnections are made
directly between exchanges, however signaling is routed through STP’s (service
transfer points) for better efficiency and to saveE1’s. Each E1 can provide
services up to 4096 user through time division multiplexing. There weremany
wire colors i.e. Red, green, blue, yellow, grey, white, black, pink, orange. Some
wires were also multicolor. There were three groups, with each group
consisting of two interns, to complete the task. Normally one group member
was responsiblefor checking the wire color and the other was responsiblefor
writing the color down on a notebook. Writing down the colors of the wires in
the notebook of all the E1’s took aboutfour days. After this, all the data was
entered into a Microsoftexcel spreadsheet. The new data was compared with
the previous data and any differences between the colors werenoted.

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2. What are the advantages of Packet switching over TDM
switching..?
The importance of packetswitching is that it is more economical than
using private lines, especially if the amount of traffic between the two
terminals does not require a dedicated circuit. Packet switching is also more
economical than data when the data communication sessions areshorter than
the minimum time for a chargeable call. Packet switching is the technique of
sending data in small chunks called packets.
With packet switching, each packet contains destination information, thereby
making it easier to send many messages quickly to various destinations. The
delivery rate of the messages depends on the speed at which the data terminal
equipment can transmit packets. Computers allow dynamic routing at each
node.
3. what is difference b/w packet switches and circuit switches??
Packet switching is a digital network transmission processin which data is
broken into suitably-sized pieces or blocks for fast and efficient transfer via
different network devices. When a computer attempts to send a file to another
computer, the file is broken into packets so that it can be sent across the
network in the mostefficient way. These packets are then routed by network
devices to the destination.
Packet-switched networks movedata in separate, small blocks -- packets --
based on the destination address in each packet. When received, packets are
reassembled in the proper sequence to make up the message. Circuit-switched
networks requirededicated point-to-point connections during calls.
A circuit-switched network is good for certain kinds of applications with limited
points to go to. If you'redoing voice applications solely, it's great," says Maloff.
"But if you have multiple locations to get to and large amounts of data to
transmit, it's better to break it down into packets."

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 SWOT ANALYSIS
Strengths
 Largestoperational network and infrastructurewithin ICT(Information&
Communication Technologies) segment.
 Anintegrated Monopoly.
 Marketleadership inLocalloop, Wirelesslocalloop (WLL)andfixed telephony.
 PTCL(Ufone) ismarketchallenger in GSMsegment.
 Ufone is performing well though Warid and Telenor are tough
competitors. PTCL, Ufone’s profitability increased by 49.2percentto Rs
977 million in 1H/FY07 as compared to Rs 655million in the
corresponding period last.
Weakness
 Not been able to nurtureits growth around customer services oriented
strategy.
 Monopolistic culture has further added to its complexities.
 Packet , the internet serviceprovider arm of PTCL continues to incur
losses due to poor management and lack of networkoptimization.
 PTCL-V,thefixed wirelessphoneserviceispoor.
 Over employment & low productivity.
 Slow decision making including external interferences.
 Corporateculture akin to government departments.
OPPORTUNITIES
 PTCL should focus on new value added services.
 Up gradation of technology to flourish the industry.
 Re-structuring of organizational hierarchy (Proper planning and
implementation is required, to Improveoverallservices).
 Adopt latest technologies.

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 Making technology accessible to all (e.g. broadband).
 Hire competent marketers and adopt aggressivemarketing that is
required to promote offered services and give tough time to
competitors.
THREATS
 New players in the industry.
 Inconsistentand Adhoc decisions by Company management.
 Security and fraud issues.
 Cybercrimes percentage is increasing.
 Political instability.
 Inflation in the country, may increasethe costof services which will
finally transferred to customers.
 Strong competition fromtelecommunication companies.
 Recommendations:
The number of trainee engineers should be increased by increasing the
number of positions available through the one year paid internship program.
This way there will be enough engineers to train summer internees. Internees
should be given basic hands on training on the different hardwareand
softwareused by the departments. Also tasks, such as making databases,
should be assigned to every internee, not justa few. And other
recommendations are discuss below

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 No doubt P.T.C.L having the monopoly in providing the Land-Line
Telephone connection in Pakistan and its playing its role magnificently.
In currentscenario P.T.C.L has increases its Revenue quite dramatically
and probably that as soon as this organization has become privatized it
will flourish its revenue in better manner.
 PTCL should immediately change its Finance upper level of hierarchy
and should streamline in the good manner.
 PTCL should also encouragethe Billing On line system that each and
every customer should have to pay his/her bill on line basis..
 Analysis:
During the internship period, I observed that there were not
enough engineers to train internees. Overall there seemed to be a shortageof
staff in the NGN and OFS department. The engineers did not have enough time
to teach internees. Also, interns were not encouraged to learn the hardware
and softwareused by the different departments. There was no telecom
equipment only for training purposes. Only lectures were given, with very little
practice work. Not every internee was assigned a task.
But again i m thankfulto PTCL company and its staff who gaveme a chance to
be there in PTCL(Pakistan Telecommunication company limited).