SWITCHING REGION

INTERNSHIP REPORT

ON

PAKISTAN TELECOMMUNICATION COMPANY LIMITED

SUBMITTED TO:The HR Department, Business South,

PTCL, Clifton Exchange

ACKNOWLEDGMENTI would like to acknowledge the Internship organizing staff that helped me attain the internship in the first place. Furthermore, the team as well as all the Field Engineers that I had the opportunity of working with; all played a huge part in helping me grab a grip on the core concepts of the drive testing of sites..

Introduction To PTCL

Pakistan Telecommunication Company Limited (PTCL) is the largest telecommunication company in Pakistan. This company provides telephony services to the nation and still holds the status of backbone for country's telecommunication infrastructure despite arrival of a dozen other telecoms including telecom giants like Telenor and China Mobile . The company consists of around 2000 telephone exchanges across country providing largestfixed line network. GSM, CDMA and Internet are other resources of PTCL,making it a gigantic organization. The Government of Pakistan sold 26%shares and control of the company to Etisalat in 2006. The Government ofPakistan retained 62% of the shares while the remaining 12% are held by the general public.

PTCL is also part of the consortium of three major Submarine communication cable networks: SEA-ME-WE 3, SEA-ME-WE 4 and I-ME-WE. In addition to wireless line operations, PTCL also provides fixed line service through its country wide CDMA based WLL (Wireless Local Loop) network, under the Vfone brand name. In the cellular segment, the second largest cellular provider in Pakistan, Ufone , is also a wholly owned subsidiary of PTCL.It hopes to be the leading Information and Communication Technology Service Provider in the region by achieving customer satisfaction and maximizing shareholders' value.

The company has over 15.5 million mobile subscribers under the name Ufone and more than 4.8 million fixed line customers. PTCL also continues to be the largest CDMA operator in the country P with approximately 1.25million V-fone customers. PTCL also offers mobile services under the Ufone brand to millions of customers across Pakistan. PTCL has the potential to bean instrumental agent in Pakistans economic growth, having laid Optical Fibre Access Network technologies in major metropolitan centers of Pakistan PTCL is also modernizing local loop services from copper to an optical network. PTCL is expanding its international capacity to meet the increasing demand of international traffic by acquiring supplementary capacity on the two SEA-ME-WE intercontinental cabling routes.

Huawei is a leading telecom solutions provider. Through continuous customer-centric innovation, we have established end-to-end advantages in Telecom Network Infrastructure, Application & Software, Professional Services and Devices. With comprehensive strengths in wire line, wireless and IP technologies, Huawei has gained a leading position in the All-IP convergence age. Their products and solutions have been deployed in over100 countries and have served 45 of the world's top 50 telecom operators, as well as one third of the world's population.

Also, they have established 17 R&D centers around the world such as in the Silicon Valley and Dallas of the United States, Stockholm in Sweden, Moscow in Russia and Bangalore in India to ensure global R&D with outstanding people.

In addition, we have 36 training centers worldwide to help out customers and local people to study advanced management, technologies and so on.

SWITCHING REGION

In early ages of telecommunication. When two users wants to talk with each other use point to point communication. In point to point communication one end of the copper wire is connected to the called user and other end of the wire is directly connected to the calling user. Point to point communication only gives the benefit of no time delay.

The advantages of this technique are less as compare to the disadvantages. Following are the demerits of point-to-point communication.

This method is so costly.

More complex to maintenance.

As the no of user increase no of link will also increase 700 times.

As the no of user increase the complication will also increase so the engineers give an idea to replace the point to point communication in to switching technique to accommodate more user in low cost.

As the no of user increase the complication will also increase so the engineers give an idea to replace the point to point communication in to switching technique to accommodate more user in low cost.

SWITCHING: is temporary path give to the calling user to communicate with called person. After introducing the switching system they doing only addition of switching office or exchange at starting and ending of point to point communication. In exchange using automatic cross bar switching system. Cross bar doing work by electrical pulses. Its give the advantage of accommodate large no of users easily. But the problem of troubleshooting will also increase. This system required a lot of space. In cross bar system call first come to the user A exchange then transfer to the exchange B and exchange B further transfer to the desired person (user B).

But the problem again facing by the engineers the limited users. And problem of troubleshooting and also noise and poor quality speech. So the whole network is divided in to multiple sections. Introducing the new sections (MDF, CABINET, D.P) from switching room to home user.

The section from MDF to CABINET is called primary section and the section from CABINET output to D.P output is known as secondary. In this system using copper wiring from switching room to home user. Now a days using fiber optics in primary section and replace MDF by ONU.

Optical network unit (ONU):An ONU closure is a mechanical compartment that houses the ONU equipment. The outer closure faces the outside environment and provides physical, mechanical, and environmental protection for cable (fiber and copper) components or equipment housed within it.

An ONU system consists of a closure that is a metallic or non-metallic enclosure that provides physical and environmental protection for the active electronic, optoelectronics, and passive optical components it houses. It terminates optical fibers from the ODN and processes the signals to and from the Customer Premises Equipment (CPE). It is the NE that provides the tariff telecommunications as well as video service interfaces for multiple residential and small business customers.

Services on the customer side of the ONU are communicated over metallic twisted pairs and coaxial cable drops (in the future, possibly fiber cable or wireless) to a Network Interface (NI) where they are handed off to the customers network (usually, inside wiring).

Depending on the deployment strategy, the ONU closure may provide one or more of the following additional features:

Access to the fiber distribution cable

Management of slack fiber and fiber splices

Access to the Telephone Support Cable (TSC) for the purpose of powering the ONU Prevention of unauthorized entry.

Primary power for ONUs is derived from either an external DC or an external AC power source. Back-up power for ONUs can either be derived from an external power source or be internal to the ONU closure and be provided by the FITL system supplier. Primary power and external back-up power can be delivered to ONUs over either copper twisted pairs or coaxial cable facilities. These cable facilities are commonly referred to as the TSC.

Deployment of an ONU system requires access to the fiber distribution cable, TSC, and metallic customer drop wires. When access to these cables is provided internal to the ONU closure (i.e., by looping each cable through the closure), it is necessary that the ONU closure also provide splicing and storage facilities for each of these cables.Switching Technology:

There are 4 different kinds of switching technologies currently operational in PTCL network.

Alcatel

Siemens

Hawaii

ZTE

TRANSMISSION REGION:I was supposed to get training in six divisions named as:

International transmission and maintenance (ITMC)

SMW-3 (South East Asia Middle East West Europe)

SMW-4 (South East Asia Middle East West Europe)

New cable and network support (NC & NS)

Multimedia and Broad Band (MM & BB)

Optical Fiber System

ITMC

(International transmission and maintenance)

The main task of ITMC is to provide cooperation between local media and international media. It establishes connectivity between the local haul or back haul and the forward haul or international media. This connectivity consists of voice and data. The transmission of voice and data is accomplished by using different techniques. The signals to be transmitted need to be undergone techniques like sampling, quantization, encoding and transmission. To increase the capacity of the transmission media techniques like multiplexing, modulation are also used.

SMW-3

SWM-3 connects 35 countries to Pakistan by means of optical fiber.

STM-64 is 1 i.e. 55 nanometer.

IPLC (LEASE CUSTOMER): Uses their own bus a single telephone line dedicated to themselves.

PFE (Power Feeding Equipment): Power cable travels along the optical fiber cable to provide power to regenerators and repeaters in the sea.

DCN (DATA Communications Network): consists of routers, which define the wavelength (). Mumbai is connected to fiber pair1 (=4) and Fujairah is connected to (=6). Router recognizes which cable is of Mumbai and which is of Fujairah. Cable from DCN connects to SLTE (Submarine Line Terminating Equipment). Each country has its own SLTE.

ROUTERS TRIBUTRY COMMON TWMA (Trans Wavelength Multiplex Amplifier) TWMA (Trans Wavelength Multiplex Amplifier) is used to amplify the signals while transmitting

RWDA (Receive Wavelength Differential Amplifier) amplify the signals while receiving.

Data rate in tributaries is STM-64.

FEC encoder (Forward Error Correction): Encodes the data in tributary to enable error correction.

Western side is connected by Djibouti at (=4) and (=6).

1= STM-64 = 10gbps.

De multiplexing occurs while receiving. STM-64 STM-16 STM-4 E1

STM-4 to STM-64 = Higher Order.

E1 to STM-1 = Lower Order.

SMW 4

2 Power Feeding Equipments installed.

1 for SMW-3.

1 for SMW-4.

Connects Pakistan to 17 different countries.

Process same as SMW-3.

Marine cables come and connect to DCN (Data Communication Network).

From DCN cables are connected to SLTE.

SLTE transfers the cables to ADM.

STM-64 gets de multiplexed to STM-16, STM-4, and STM-1.

Then the cables are fed to ODF.

This distributes the connection locally.

We have rectifiers to prevent damage.

SMW-4 connects Pakistan to 17 countries. Few examples are:

East West

MalaysiaSA

SingaporeUAE

IndiaAlexandria

WDM (Wavelength Division Multiplexing):

Different SDH come and connect to WDM.

Based on the frequency WDM allots channels to different signals.

Segment grouping of signals (countries are divided into segments) so that a problem occurs it can be rectified easily.

Last station Marseille (France)

Installing new project IMWE (Indian Middle East Western Europe)

Multimedia and Broad Band (MM&BB)Broadband:

The word broadband is used for the minimum bandwidth which can support the transmission of multimedia services.

Broadband access:

Broadband access is the high speed connection between the end user and internet through certain kind of network.

Broadband Access Technologies

XDSL

HSDLHigh speed digital subscriber

SDSLsymmetric DSL

ADSL.Asymmetric DSL

VDSLVery high bit rate DSL

EDSLEthernet DSL

ISDL..ISDN DSL

UDSL.Ultra high DSL

HFCHybrid fiber coaxial

Home PNA..Home phone line

Ethernet

Wireless Broadband

LMDSlocal multipoint Distribution

DBSDirect Broad service

Microwave Radio Access GPRS..General packet Radio service

Optical access network

PLC.Power line cable

SDHsynchronous digital hierarchy

Frame relay.

These are some broadband access technologies, which are used to access internet and other broadband services.

DSL Principles:

SHDSL

It is Single pair high bit rate DSL, one pair, symmetric transmission, Variable data rates

Generally the variable data rate is 192 Kbps..2.312Kbps

The range is valid up to a range of 5 Km.

VDSL

VDSL is very high data rate DSl, one wire pair, variable Data rates, Valid up to 5 Km. The data rate is up to 13mbps to 52Mbps.

ADSL

One wire pair, Asymmetric transmission, data rates from 64 Kbps to 1.5 Mbps, covering a distance of 5 Km.

Optical fiber system (OFS):

Optical fiber system consist a network of optical fibers which are used for the transmission of optical signals.

Initially all the signals are analog signal, which cant be transmitted to long distance because they undergo transmission impairments and path losses. To minimize such problems optical fibers have been

designed because in which signals are although analog but they undergo a very low line problems.

Usually in transmission of signal at a certain distance repeaters are used which regenerate the signal again; in case of optical fibers these repeaters are installed at a large distance usually 25 km.

Because of there light weight optical fibers are very easy to install even under water. Use of Optical fibers has increased the capacity of data transmission through a media. It is said that the bandwidth of a single optical fiber can be increased to infinity by using modern multiplexing techniques.

A single optical fiber can support a data of 10 GB. This is used commonly in long distance transmission.

STRUCTURE OF OPTICAL FIBER

Optical fiber generally consists of three parts

Core

Cladding

Jacket

CORE: Core is the inner most section and consists of one or more strands, made up of glass or plastic, the core has a diameter of 50 micrometer.

CLADDING:A glass or plastic coating having optical properties different from those of the core, and has diameter of 125 micrometer. The interface between core and cladding act as a reflector to confine light that would otherwise escape the fiber.

JACKET: The jacket is composed of plastic and other materials layered to protect against moisture, abrasion, crushing and other environmental dangers.

MODES OF TRANSMISSION:

The transmission of light signals through an optical fiber is accomplished by using different transmission modes like Single mode, graded index Multimode, step index mode.

SINGLE MODE

In single mode, the light rays travel in a straight line. Some Spacing is kept between the rays to avoid interference. This mode is used for large distance communication

GRADED INDEX MULTIMODE

This mode of transmission is done by varying the index of refraction of the core. Refractive index is higher at centre whereas it decreases towards the corners.This transmission mode is used for shorter distances.

STEP INDEX MULTIMODE:

Rays at shallow angle are reflected and propagated through along the fiber other rays are absorbed by the surrounding material. With this mode multi paths exist due to which signals undergo dispersion and data cant be accurately achieved.

WLL REGION

The WLL department deals with the installation of the CDMA2000 system .The engineers here are asked to make feasibility reports of various sites. The installation of the hardware then ensues when the feasibility of the system is suitable in the region. The engineers in this department have the job of contacting the contractors who then survey the area and try to make a minimum financial estimate for the installation of the hardware. This is primarily why this department is chosen for fresh internees, so that they can grasp a good idea about the workings and ins & outs of the CDMA2000system. Some terms that I had to acquaint to during my internship with PTCL are listed below:

WLL: Is an abbreviation for a Wireless Local Loop. It is a term for the use of a wireless communications link as the "last mile / first mile" connection for delivering plain old telephone service (POTS) and/or broadband Internet to telecommunications customers. Various types of WLL systems and technologies exist. During my internship at PTCL, I had to work with Broadband Wireless Access (BWA). Other terms for this type of access include Radio In The Loop (RITL), Fixed-Radio Access (FRA) and Fixed Wireless Access (FWA).

CDMA2000:It is also known as IMT Multi-Carrier (IMT-MC)) is a family of 3Gmobile technology standards, which use CDMA channel access, to send voice, data, and signaling data between mobile phones and cell sites. The set of standards includes: CDMA2000 1X, CDMA2000 EV-DO Rev. 0, CDMA2000 EV-DO Rev. A, and CDMA2000 EV-DO Rev. B. All are approved radio interfaces for the ITU's IMT-2000. CDMA2000 has a relatively long technical history and is backward compatible with its previous 2G iteration IS-95 (CDMA One). In the United States, CDMA2000 is a registered trademark of the Telecommunications Industry Association (TIA-USA). The successor toCDMA2000 is LTE, part of the competing 3GPP family.

Base transceiver station

A base transceiver station (BTS) or cell site is a piece of equipment that facilitates wireless communication between user equipment (UE) and a network. UEs are devices like mobile phones (handsets), WLL phones, computers with wireless Internet connectivity, WiFi and WiMAX gadgets etc. The network can be that of any of the wireless communication technologies like GSM, CDMA, WLL, WAN, WiFi, WiMAX etc. BTS is also referred to as the radio base station (RBS), node B (in 3G Networks) or, simply, the base station (BS). For discussion of the LTE standard the abbreviation eNB for evolved node B is widely used.

Though the term BTS can be applicable to any of the wireless communication standards, it is generally and commonly associated with mobile communication technologies like GSM and CDMA, In this regard, a BTS forms part of the base station subsystem (BSS) developments for system management. It may also have equipment for encrypting and decrypting communications, spectrum filtering tools (band pass filters) etc. antennas may also be considered as

Components of BTS in general sense as they facilitate the functioning of BTS. Typically a BTS will have several transceivers (TRXs), which allow it to serve several different frequencies and different sectors of the cell (in the case of sectorised base stations). A BTS is controlled by a parent base station controller via the base station control function (BCF). The BCF is implemented as a discrete unit or even incorporated in a TRX in compact base stations. The BCF provides an operations and maintenance (O&M) connection to the network management system (NMS), and manages operational states of each TRX, as well as software handling and alarm collection. The basic structure and functions of the BTS remains the same regardless of the wireless technologies.

A BTS in general has the following parts:

Transceiver (TRX):

Quite widely referred to as the driver receiver (DRX). DRX are either in the form of single (sTRU), double (dTRU) or a composite Double Radio Unit (DRU). It basically does transmission and reception of signals. Also does sending and reception of signals to/from higher network entities (like the base station controller in mobile telephony).

Power amplifier (PA):

Amplifies the signal from DRX for transmission through antenna; may be integrated with DRX.

Combiner:

Combines feeds from several DRXs so that they could be sent out through a single antenna. Allows for a reduction in the number of antenna used.

Duplexer

For separating sending and receiving signals to/from antenna. Does sending and receiving signals through the same antenna ports (cables to antenna).

Antenna:

This is the structure that lays underneath the BTS; it can be installed as it is or disguised in some way (Concealed cell sites).

Alarm extension system:

Collects working status alarms of various units in the BTS and extends them to operations and maintenance (O&M) monitoring stations.

Control function:

Control and manages the various units of BTS including any software. On-the-spot configurations, status changes, software upgrades, etc. are done through the control function.

Baseband receiver unit (BBxx):

Frequency hopping, signal DSP, etc.

Open BTS:

OpenBTS (Open Base Transceiver Station) is a software-based GSM access point, allowing standard GSM-compatible mobile phones to make telephone calls without using existing telecommunication providers' networks. OpenBTS is notable for being the first free software implementation of the industry-standard GSM protocol stack. It is written in C++ and released as free software under the terms of version 3 of the GNU Affero General Public License (AGPL)

Base station subsystem:

The base station subsystem (BSS) is the section of a traditional cellular telephone network, which is responsible for handling traffic and signaling between a mobile phone and the network switching subsystem. The BSS carries out transcoding of speech channels, allocation of radio channels to mobile phones, paging, transmission and reception over the air interface and many other tasks related to the radio network.

LTE: LTE Advanced

It is a preliminary mobile communication standard, formally submitted as candidate 4G systems to ITU-T in the fall 2009, and expected to be finalized in 2011. It is standardized by the 3rd Generation Partnership Project (3GPP) as a major enhancement of the pre-4G 3GPP Long Term Evolution (LTE) standard.

Base station controller:

The base station controller (BSC) provides, classically, the intelligence behind the BTSs. Typically a BSC has tens or even hundreds of BTSs under its control. The BSC handles allocation of radio channels, receives measurements from the mobile phones, and controls handovers from BTS to BTS (except in the case of an inter-BSC handover in which case control is in part the responsibility of the ancho MSC). A key function of the BSC is to act as a concentrator where many different low capacity connections to BTSs (with relatively low utilization) become reduced to a smaller number of connections towards the mobile switching center (MSC) (with a high level of utilizations). Overall, this means that networks are often structured to have many BSCs distributed into regions near their BTSs which are then connected to large centralized MSC sites. The BSC is undoubtedly the most robust element in the BSS as it is not only a BTS controller but, for some vendors, a full switching center, as well as an SS7 node with connections to the MSC and serving GPRS support node (SGSN) (when using GPRS). It also provides all the required data to the operation support subsystem (OSS) as well as to the performance measuring centers.

A BSC is often based on a distributed computing architecture, with redundancy applied to critical functional units to ensure availability in the event of fault conditions. Redundancy often extends beyond the BSC equipment itself and is commonly used in the power supplies and in the transmission equipment providing the A-ter interface to PCU.The databases for all the sites, including information such as carrier frequencies, frequency hopping lists, power reduction levels, receiving levels for cell border calculation, are stored in the BSC. This data is obtained directly from radio planning engineering which involves modelling of the signal propagation as well as traffic projections.A Summary of what I learnt at my InternshipThe main purpose of the Internship was to acquaint myself with the Technical aspects of various CDMA modulation techniques and to gain familiarization with its related machinery. The initial weeks at the internship were full of curriculum studying ..During the last few weeks of my Internship, I got the chance to visit various sites where I helped them install and perform different tests on BTS units .Apart from just going to the fields to gain hands on experience of unitinstallation, the engineers explained the architecture of the BTS units and how the various hardware devices are connected together. Add to that, the descriptions of how the system employs itself in case of power failure and emergencies which were very useful for learning.

Internship Report at PTCL