A

PROJECT REPORT

ON TRAINING

AT

RELIANCE COMMUNICATIONS

Submitted by:

CHIRAG MOHANTY

Roll no.: 604045

B.Tech, 6th Semester

Department of Electronics and Telecommunications

Kalinga Institute of Industrial TechnologyKIIT UNIVERSITY

Bhubaneshwar

ACKNOWLEDGEMENT

With the completion of the training my experience at the firm was excellent. The task of undertaking the training travelled through a dynamic experience. With the constant guidance, valuable suggestions, timely help and heart warming encouragement rendered to me by Mr. Sarthak Dash along with all other members of the Installation and Commissioning (I&C) team the firm served as an excellent learning platform.

During the course of the training I came through the working pattern of the office along with professionalism. Also the basic practical experience at the site helped a lot. Theoretical discussions, off-site situation handling and on-site experience are to name a few of the environments to which I was exposed. Along with it I was given enough opportunities and encouragement to think independently in various problem solving situations.

I would like to express my deepest sense of gratitude to the whole team of engineers of the Installation and Commissioning (I&C) department – Mr. Sarthak Dash, Mr. Ajit Routray, Mr. Bijay Panda, Mr. Biswajit Mishra, and Mr. Saroj Jena.

I would also like to thank Mr. Manoj Mishra, Mr. Santosh Moharana and Mr. Debasish Mahapatra for the valuable help and support they have rendered throughout the training process.

I would like to express my thanks to all those people who directly or indirectly supported me throughout my term for the training.

Above all I want to thank Mr. Venkat Shastri, Head of Training & Placement Department, KIIT UNIVERSITY, for recommending me to the practical training; and Mr. Jugal Satapathy, HR, Orissa Circle, Reliance Communications for inducting me into the firm as a trainee.

Thanking you sincerely,

Chirag Mohanty

CERTIFICATION

This is to certify that Mr. Chirag Mohanty, Roll no. 604045, of 3rd year, Electronics and Telecommunication Engineering, underwent Practical Training from 1st May ’2009 to 15th June ‘2009 at our firm; for the course requirement at Kalinga Institute of Industrial Technology, KIIT UNIVERSITY, Bhubaneshwar.

He has completed his training with utmost dedication and sincerity.

We wish him all the best for his future endeavours.

Signature Signature

Jugal P. Satapathy Sarthak Dash

H.R. Engineer Incharge of

Orissa Circle Training

Reliance Communications Limited

Company Profile

Reliance – Anil Dhirubhai Ambani Group, an offshoot of the Reliance Group founded by Shri Dhirubhai H Ambani (1932-2002), ranks among India’s top three private sector business houses in terms of net worth. The group has business interests that range from telecommunications (Reliance Communications Limited) to financial services (Reliance Capital Ltd) and the generation and distribution of power (Reliance Infrastructure Limited).

Reliance – ADA Group’s flagship company, Reliance Communications, is India's largest private sector information and communications company, with over 77 million subscribers. It has been listed on the National Stock Exchange and the Bombay Stock Exchange. It has established a pan-India, high-capacity, integrated (wireless and wireline), convergent (voice, data and video) digital network, to offer services spanning the entire infocomm value chain.

Other major group companies — Reliance Capital and Reliance Infrastructure — are widely acknowledged as the market leaders in their respective areas of operation.

The Late Dhirubhai Ambani dreamt of a digital India - an India where the common man would have access to affordable means of information and communication. Dhirubhai, who single-handedly built India’s largest private sector company virtually from scratch, had stated as early as 1999: “Make the tools of information and communication available to people at an affordable cost. They will overcome the handicaps of illiteracy and lack of mobility.” It was one of Dhirubhai’s great dreams in life to see ordinary Indians enjoy the enormouseconomic benefits of being able to access affordable yet world class telecommunicationsinfrastructure. He wanted Reliance to spearhead a communications revolution that woulddramatically cut down the cost of connectivity, and propel India into the digital age. His ultimateambition: To make the cost of a phone call cheaper than that of a post card. It was thereforeentirely logical for Reliance to enter the telecommunications space when the sector was openedup for private participation in the 1990s.The rest, as they say, is history.Today, Reliance Communications is India’s largest information and communications servicesprovider offering the full range of integrated telecom services—at prices that are, by far, the lowest anywhere in the world.

It was with this belief in mind that Reliance Communications (formerly Reliance Infocomm) started laying 60,000 route kilometres of a pan-India fibre optic backbone. This backbone was commissioned on 28 December 2002, the auspicious occasion of Dhirubhai’s 70th birthday, though sadly after his unexpected demise on 6 July 2002.

Our business encompasses a complete range of telecom services covering mobile and fixed line telephony. It includes broadband, national and international long distance services and data services along with an exhaustive range of value-added services and applications. Our constant endeavour is to achieve customer delight by enhancing the productivity of the enterprises and individuals we serve.

Reliance Mobile (formerly Reliance India Mobile), launched on 28 December 2002, coinciding with the joyous occasion of the late Dhirubhai Ambani’s 70th birthday, was among the initial

initiatives of Reliance Communications. It marked the auspicious beginning of Dhirubhai’s dream of ushering in a digital revolution in India. Today, we can proudly claim that we were instrumental in harnessing the true power of information and communication, by bestowing it in the hands of the common man at affordable rates.

Reliance Communications has a reliable, high-capacity, integrated (both wireless and wireline) and convergent (voice, data and video) digital network. It is capable of delivering a range of services spanning the entire infocomm (information and communication) value chain, including infrastructure and services - for enterprises as well as individuals, applications, and consulting.

Today, Reliance Communications is revolutionizing the way India communicates and networks, truly bringing about a new way of life.

History of Telecommunications

Radio has been around only for the last 100 years (out of ~6000 years of written human history).

1680’s: Isaac Newton’s idea of the spectrum 1830’s: Basic Electricity 1890’s: First demos of radio by experimenters

Telegraphy:

Early electronic communication was carried only by wires and used only crude on-off signaling to laboriously spell out the message.

1837: Samuel Morse patented his telegraph 1844: First commercial telegraph systems operational 1857: First trans-atlantic cable put in service

Telephony:

In 1876, Alexander Graham Bell patented his telephone, a device for carrying actual voices over wires. Initial telephone demonstrations sparked intense public interest and by the late 1890’s, telephone service was available in most towns and cities across the USA.Thus, the telecommunications industry, as we know it today, originated in 1876 when Alexander Graham Bell developed the telephone in an attempt to communicate with his mother and wife, who were both deaf. Bell filed his patent for the telephone on February 14, 1876, just four hours before Elisha Grey applied for the same patent. But for that timing, we might have had the Grey Telephone System instead of the Bell Telephone System. Through legal maneuvering Bell’s patent was upheld and the Bell Telephone Company, which was formed in 1877, began to expand across the United States of America and emerged as a near monopoly supplier of telephone services. In 1880 the company was renamed American Bell.

Radio Milestones: 1888: Heinrich Hertz, German physicist, gives lab demo of existance of electromagnetic

waves at radio frequencies 1895: Guglielmo Marconi demonstrates a wireless radio telegraph over a 3-km path near

his home it Italy

1897: the British fund Marconi’s development of reliable radio telegraphy over ranges of 100 kM

1902: Marconi’s successful trans-Atlantic demonstration 1902: Nathan Stubblefield demonstrates voice over radio 1906: Lee De Forest invents “audion”, triode vacuum tube (feasible now to make steady

carriers, and to amplify signals) 1914: Radio became valuable military tool in World War I 1920s: Radio used for commercial broadcasting 1940s: first application of RADAR - English detection of incoming German planes

during WW-II 1950s: first public marriage of radio and telephony - MTS, Mobile Telephone System 1961: transistor developed: portable radio now practical 1961: IMTS - Improved Mobile Telephone Service 1970s: Integrated circuit progress: MSI, LSI, VLSI, ASICs 1979, 1983: AMPS cellular demo, commercial deployment

Frequencies Used by Wireless Systems:

Overview of the Radio Spectrum

Structure of a Typical Wireless System

Wireless Base Stations:

It provides the radio connection between mobile users and the switch. One wireless system in a large metropolitan area may require hundreds of base stations to

deliver unbroken coverage and provide sufficient capacity to handle all potential users.

The Switch:

Each call involves joining a circuit leading to one customer (usually on the radio side of the system) and a circuit leading to another person (usually out in the Public Switched Telephone Network (PSTN)

The device that makes the actual physical connection is called the switch The switch is also responsible for storing billing records, interpreting dialed phone

numbers, routing calls, and implementing all calling features

The Base Station Controller (BSC):

The Base Station Controller (BSC) interfaces the Switch and the base stations Compresses speech signals for more efficient transmission over the scarce radio spectrum Controls the base stations and implements the handoff of calls from one base station to

another as users drive across the system

Home Location Register (HLR):

The HLR (Home Location Register) is the official database of all customers on a wireless system

It can be part of the switch, or held in a server at a central location where multiple switches can interrogate it

Information held in the HLR:• current account status/validity• phone’s technical parameters• whether the phone is presently turned on, and if so, the identity of switch which is presently serving the phone • secret keys for authentication to avoid fraudulent use/cloning

Delivering an Incoming Wireless Call: Someone dials a mobile subscriber’s number

1. System checks database for current location of mobile, and pages this area Database is kept up-to-date by a process called registration

2. Mobile recognizes page and sends back acknowledgment to the strongest cell3. System assigns a voice channel to the mobile

System sends voice channel assignment to mobile on control channel mobile acknowledges and jumps to the assigned voice channel

4. Phone rings and mobile subscriber answers call Conversation begins

An illustration of the above is given on the following page.

Managing Handoffs:

As a mobile travels through the service area, it passes from the coverage zone of one base station into the coverage of another

Signal strength measurements by the mobile or the base station trigger the BSC and switch to “hand off” the call from base station to base station, avoiding dropped calls and interference

Each wireless technology uses its own methods to implement the handoffs. CDMA can even “simulcast” to the mobile from multiple base stations to reduce fading effects (this is called “soft handoff”)

What is Multiple Access?

Multiple Access is the simultaneous use of a communications system by more than one user

Each user’s signal must be kept uniquely distinguishable from other users’ signals, to allow private communications on demand

Users can be separated in many ways:• physically: on separate wires• by arbitrarily defined “channels” established in frequency, time, or any other variable imaginable

Wireless Multiple Access Methods

Frequency Division Multiple Access

• A user’s channel is a private frequency

Time Division Multiple Access

• A user’s channel is a specific frequency, but it only belongs to the user during certain time slots in a repeating sequence

Code Division Multiple Access

• Each user’s signal is a continuous unique code pattern buried within a shared signal, mingled with other users’ code patterns. If a user’s code pattern is known, the presence or absence of their signal can be detected, thus conveying information.

TDMA: Time Division Multiple Access Each user has a specific frequency but only during an assigned time slot. The frequencyis used by other users during other time slots, like a condominium at a beach resort

UNITED STATES VERSIONS:

IS-54: The original TDMA format, intended for use within existing AMPS systems IS-136: Enhanced TDMA with special control channels to allow short message service,

battery life extension, other features 6 timeslots, three users occupy in rotation

INTERNATIONAL VERSION

GSM: Groupe Special Mobile Developed in Europe, used in roughly 50% of all wireless systems worldwide 8 timeslots, 7 or 8 users occupy in rotation

CDMA: Code Division Multiple Access

Each user’s signal is a continuous unique code pattern buried within a shared signal, mingled with other users’ code patterns. If a user’s code pattern is known, the presence or absence of their signal can be detected, thus conveying information.

All CDMA users occupy the same frequency at the same time! Time and frequency are not used as discriminators

CDMA interference comes mainly from nearby users CDMA operates by using CODING to discriminate between users Each user is a small voice in a roaring crowd - but with a uniquely recoverable code

Third Generation Wireless Systems

2G to 3G Migration Paths:

A Game of Avoiding Extremes

The traffic engineer must walk a fine line between two problems:

Overdimensioning too much cost insufficient resources to construct traffic revenue is too low to support costs very poor economic efficiency!

Underdimensioning Blocking Poor technical performance(interference) Capacity for billable revenue is low very poor economic efficiency! revenue is low due to poor quality users unhappy, cancel service very poor economic efficiency

Principles of Traffic Engineering:

Blocking Probability / Grade of Service

Blocking is inability to get a circuit when one is needed Probability of Blocking is the likelihood that blocking will happen In principle, blocking can occur anywhere in a wireless system:

• not enough radios, the cell is full • not enough paths between cell site and switch • not enough paths through the switching complex • not enough trunks from switch to PSTN

Blocking probability is usually expressed as a percentage using a “shorthand” notation: • P.02 is 2% probability, etc. • Blocking probability sometimes is called “Grade Of Service”

Most blocking in cellular systems occurs at the radio level. • P.02 is a common goal at the radio level in a system

Wireless System Performance Optimization

Key Performance Indicators and Objectives • Dropped Calls, Access Failures, system BER, FER • Handoff Activity Levels • Capacity and Blocking

Success comes from managing resources • Handoff • Thresholds properly set • Neighbor lists well-optimized • RF Coverage: “holes” vs. excessive overlap • PN or Frequency Planning • Hardware defects: watch statistics for clues

ANALOG AND DIGITAL SIGNALS

ANALOG :

Historically, telephone systems were entirely analog circuits. When voice is converted to an electrical signal through the microphone in a telephone, it provides a continuously varying electrical wave. The wave matches the pressure pattern of the sound that created it and conveys loudness which is measured as amplitude, and pitch which is measured as frequency. Because the tone (pitch) and loudness (amplitude) of voice is unpredictable, the analog signal is also unpredictable.

The basic shape of an electrical wave used to transmit telecommunications signals is represented by the sine wave. The rate at which the electrical current alternates is measured in hertz, which means cycles per second. A voice telephone circuit is designed to handle frequencies from 300 to 4,000 hertz (4 Khz).

As an analog signal travels through a wire, the signal loses strength over distance (attenuation) and has to be amplified. Unfortunately, when the voice signal is amplified, any noise on the line is also amplified. After much amplification the line noise component may be larger than the actual voice signal. Circuit noise can make the conversion unintelligible.

DIGITAL :

Unlike the analog signal, a digital signal is predictable. A digital signal is a series of discrete, discontinuous voltage pulses. The analog voice signal is sampled at the rate of 8,000 samples per second, and each sample is transmitted as a binary code. The binary states of 0 and 1 are represented as discrete levels of voltage.

Digital transmission has higher quality than analog. Like analog signals, digital signals lose strength over distance. However, with digital transmission, regenerators detect the incoming bit stream of 0s and 1s and create a new signal that is identical to the original signal.

What is a Transmission Network?

Area of Telecom Network dealing with transport of data, voice, video and other signals over long distances is referred to as Transport (Tpt) or Transmission (Tx) Network. • e.g. - Intercity connectivity between local trunk and tandem exchanges within a city also falls in the category of ‘Tpt NW’ e.g. Intracity also called Backhaul NW

Tpt NW - Physically consists of MW, OFC or satellites as a medium (criterion of selection - Tx rate, distance, protection, cost, reliability, environmental conditions)

Figurative Rep of a Tpt NW NW design - STAR, TREE, RING or MESH topologies (main criterion - connectivity,

protection and cost)

Transport Systems required to carry large data

2.5 Gbps (1Gb=109b) - 30,000 voice channels, 10 Gbps, 40 Gbps Terabits per sec (1 Tb=1012b) - Lucent recently tried 2 Tbps data rate using

DWDM over a single fibre Future Data Rates in terms of Petabits per sec (1 Pb=1015b) and Exabits per

second (1 Eb = 1018b)

Transmission systems, since they carry large data rates, must have

Min “Down Time” (0.003%) Low “Bit Error Rates” (BER < 10-9) High MTBF (5 years) “Self Healing” Ring Structure

Transmission links used are primarily of two types these days:

Microwave Link Optical Fiber Cable (OFC) Link Coaxial cable VSAT

What is Microwave Radio?

Microwave radio is a point to point fixed link that operates in duplex mode I.e. each radio frequency channel consists of a pair of frequencies for the transmit and receive directions respectively. The base band signal which contains the user information occupies a limited

bandwidth depending upon the modulation scheme used. The signal is modulated over an RF carrier and is transmitted over the air as an electromagnetic waveform. The Microwave Radio links cover the frequency spectrum from 150 MHz to 60 GHz.

Characteristics of a Radio Link System:

Signal follows a straight line or line of sight (LOS) path. Beam traverses through the Troposphere. Microwaves are electromagnetic waves similar to light. Propagation is affected by Free Space Attenuation, Reflection, Precipitation, Refraction,

Diffraction, Scattering and Polarization. Uses frequencies above 150 MHz. Uses angle modulation I.e. Frequency Modulation or Phase Modulation

Advantages of Microwave Radio:

Microwave radios are cheaper than Satellite or Leased Line Service. Do not involve ROW (Right Of Way) Permissions. Radios have a stepped cost profile where as fibre has a linear cost profile. Radio systems are easy to install.

Installation of Radios does not impact the intervening terrain since no digging is involved.

Fast Roll out. Better overall reliability.

Stages in installation of a Microwave System:

Microwave links are set up for connecting two distinctly located points for establishing telecommunications circuits. This is similar to laying multi-core cables between the two points; but in quality and overall economics this is far superior to the cable system. Various sub-activities are briefly explained below:

1) Survey - The first job to be undertaken before establishing a microwave link is survey of the terrain between the two locations intended to be connected. The survey consists of

two parts: theoretical survey using survey maps and actual survey by visiting various sites.

Survey of India publishes maps which clearly indicate the height of various points above mean sea level (MSL) for theoretical survey. But in different terrain and in city areas it will be difficult to complete the survey without actual visits to the sites. For this purpose a accurate device, GPS (Global Positioning System) is extensively used by engineers for more accurate & reliable results.

2) Assessment of height - Once all the physical obstructions have been identified, distance from one of the point to be connected is plotted against the obstruction height at that point. However for assessment of the actual height of the obstruction it is not sufficient to consider the height of physical structure above MSL alone. For this purpose air filled balloons are used to estimate height.

For the purpose of economy following policies are followed:a) Existing structures if available are used so that structure’s height at the end it is available is used to check required tower height at the other end. b) Since ground space is costly at a location, lower tower height are used at that end. c) If any existing tall building is available at any end, choose the biggest tower height that the building can support. d) If transportation of the material is difficult or if soil condition is bad at one end, use of lower tower height at this end is going to be cheaper.

3) Construction of Equipment room - The equipment room is constructed keeping in view the size of the equipment as well as the capacity of the equipment to be installed in the room. Proper layout is made well in advance and should be approved from the owner/user. Care should be taken to keep elbow space i.e. space for future expansion. If the installation is to be done on the ground floor it should be ensured that water logging does not take place.If the room in which the equipment is to be installed is on the top floor of the building, it is to be made sure that the position chosen for installing the equipment is free from any water drips.

4) Erection of Tower - The erection of tower involves selection of proper tower design, fabrication of tower members, and design of the tower, provision of tower foundations and fitting of tower members. The tower design must ensure that the twist and sway of the tower is within the beam width of the microwave beam. Typical twist and sway is required to be restricted within about 0. 5 Degrees for antenna gains of about 40 dB.

5) Fitting Of Antenna - After erecting the tower and also the antenna-mounting arrangement, it is possible to install the antennas. For this purpose the antennas to be installed are brought below the tower structure and ropes tied at suitable anchoring points of the antennas. Once the antenna is lifted to the top is bolted onto the antenna mounting pipes through suitable fittings which normally come with the antenna. After that, other fittings such as the feed horn and wave-guide have to be done.

6) Waveguides & Flexible cable - Waveguides or coaxial cables are used for connecting antenna feed horns to radio transceivers. Normally the main waveguides/coaxial cables are very rigid and the ends connections are made by small lengths of flexible coaxial cables. These cables are flexible but cannot be used in lengths more than one metre.

7) Radio Transceivers -The installation of the radio transceiver does not involve much effort, as the present-day equipment are lightweight and modular in structure. Most of the equipment are rack mountable. Two standard racks are quite common-48cm (19 Inch) rack and slim rack which are first of all fixed to the floor. Radios are imported from SIAE, Italy and racks are locally ordered.

8) Alignment - This is the process in which the two antennae are optimised to receive the maximum signal from each other. The antennae alignment is carried out with the help of Compass, Binocular, Walkie-Talkie and other basic tools.

Free Space Loss

Before you can determine if a link is feasible, you must first calculate the link’s free space loss. Free Space Loss is the expected attenuation of a signal as it travels away from the Transmitting device. When a signal radiates from the antenna, it spreads out over an increasingly larger distance. As the area covered increases, the power density (or the amount of power per unit area) decreases. The effectively weakens the radio signal.

The radio signal is more concentrated at point A than at Point B. This is similar in principal to how objects appear in a car’s headlights at night.

Objects closer to the headlights appear brighter than objects further away.

Transmitting source (car head light)

pointA pointB

The loss between the transmitting and the receiving antenna with transmission medium as vacuum is termed as free space loss. The antenna at each side is isotropic having a gain of 1 or 0 dB.

FSL = 96.6 + 20 log D + 20 log F

Where F = frequency in GHz

D = distance in miles

Receiver Sensitivity Threshold:

The Receiver Sensitivity Threshold (Rx) defines the minimum signal strength required in order for a radio to successfully receive a signal. A radio can not receive or interpret a signal that is weaker than the receiver sensitivity threshold.

Receive Signal Level:

The Receive Signal Level (RSL) is the expected strength of a signal when it reaches the receiving radio. The following formula defines the Receive Signal Level:

O - Lctx + Gatx – Lcrx + Gatx – FSL = RSL

Where,

Po is the output power of the transmitter (in dBm)

Lctx is the cable loss between the transmitter and its antenna (in dB)

Gatx is the gain of the transmitter’s antenna (in dBi)

Lcrx is the cable loss between the receiver and its antenna (in dB)

Gatx is the gain of the receiver’s antenna (in dBi)

FSL is free space loss (in dB)

Link Feasibility Formula

To determine if a link is feasible, we have to compare the calculated Receive Signal Level with the Receiver Sensitivity Threshold. The link is theoretically feasible if

RSL = Rx

If the Receive Signal Level is greater than or equal to the Receiver Sensitivity Threshold, then the link may be feasible since the signal should be strong enough to be successfully interpreted by the receiver.The link is not feasible since RSL is less than Rx (-80.5 dB 77 dB).

Note: This formula is not a guarantee that a link is viable. It should be used for proof-of- concept purpose only. The Receiver Signal Level does account for path fading phenomena that may add addition loss to the radio signal and cause the strength of received signal to fall below the receiver sensitivity threshold.

Fade Margin and link availability

Fade margin is the difference between the unfaded received signal level and the receive sensitivity threshold. Each link must have sufficient fade margin to protect against path fading that weakens the radio signals. Fade margin is directly related to Link Availability, which is the percentage of time that the link is functional. The percentage of time that link is available increases as the fade margin increases. A link will experience fewer system outages with greater Fade Margin. A link with little or no Fade Margin may experience periodic outages due to path fading phenomena.

Climate condition and path fading

Path fading occurs more frequently in flat, humid environments (like south eastern U.S.) than in rough, dry location (like Rocky Mountain States). Therefore link in flat and humid area requires a greater Fade Margin to achieve the same level of Link Availability as a link in a rocky and dry location.

Path profile

A path profile is a graphical representation of the path traveled by the radio waves between the two ends of a link. The path profile determines the location and height of the antenna at each end of the link, and it insures that the link is the link of obstructions, such as hills, and not subject to propagation losses from radio phenomena, such as multipath reflections.

In addition to terrain elevation ,a Path Profile must consider the effects of several radio phenomena , including multipath reflections and refraction, and provide adequate Fresnel Zone clearance.

Fresnel Zone clearance

The endpoints of a radio link must have unobstructed radio line-of-sight. Radio line-of-sight is not the same optical line-of- sight (that is, the ability to see one end of a link from the other). Microwaves have a lower frequency than visible light and , therefore, behave differently in response to environmental conditions. Radio line-of- sight requires more clearance than optical line-of-sight to accommodate the characteristics of microwave signals. Figure illustrates a case where a path has optical line-of- sight but not radio line-of-sight.An electromagnetic wave does not travel in a straight line: the wave spreads out as it propagates. Also, the individual waves that make up a radio signal do not travel at the same phase velocity. A French physicist, Augustine Fresnel, defined the propagation of a radio wave as a three-dimensional elliptical path between the transmitter and receiver. Fresnel divide the path into several zones based on the phase and speed of the propagating waves ,as shown in the figure.

The size of each Fresnel Zone varies based on the frequency of the radio signal and the length of the path. As frequency decreases, the size of the Fresnel Zone increases. As the length of the path increases, the size of the Fresnel Zone also increases. A Fresnel Zone’s radius is greatest at the mid point of the path. Therefore, the midpoint requires the most clearance of any point in the path.

Multipath Reflections

As described earlier in the discussion of Fresnel Zones, a radio signal is composed of individual waves that travel in different directions as the signal propagates. When a radio wave hits a physical object, it may penetrate the object, be reflected by the object, or be absorbed by the object.

A reflected wave causes a phenomenon known as multipath. Multipath means that the radio signal can travel multiple paths to reach the receiver. Typically, multipath occurs when a reflected wave reaches the receiver at the same as the direct wave that travels in a straight line from the transmitter. If the two signals reach the receiver in-phase (that is, both signals are at the same point in the wave cycle when they reach the receiver), then the signal is amplified. This is known as an “upfade.” If the two waves reach the receiver out-of-phase

(that is, the two signals are at opposite points in the wave cycle when they reach the receiver), they weaken the overall received signal. If the two waves are 180 apart when they reach the receiver, they can completely cancel each other out so that a radio does not receive a signal at all. A location where a signal is canceled out by multipath is called a “null” or “downfade”.

Smooth surfaces , such as a body of water, a flat stretch of earth, or a metal roof, reflect radio signals. In figure below, the body of water reflects a wave that cancels out the direct signals and brings down the radio link.

To avoid system failures, one should design a path so that the reflected signal is dispersed by an uneven surface before it reaches the receiver and cancels out the direct wave. In other words, one should design the path so its reflection point does not fall on a reflective surface. An RF engineer is to be consulted or use a path profile software program to identify the location of a path’s reflection point.

Transmitter Receiver

Reflected Signal Cancels Out Direct Signal

If necessary, one can adjust the height or change the position of one or both antennas to move the reflection point so that it is blocked by an obstruction or strikes an uneven surface. In figure above, the height of the transmitting antenna has been reduced so that the reflected signal is dispersed by rocky terrain.

A Change in the Antenna Height Moves the Reflection Point

Refraction

Radio waves move slower through substances of greater densities. This causes a wave to bend or refract as it travels through substances of different densities. For example, light bends when it hits water. Since the density of the earth’s atmosphere decreases as altitude increases, the bottom of a radio wave travels through a denser atmosphere and moves more slowly than the top of the wave . This causes the radio signal to refract or bend towards to earth’s surface following the curvature of the earth. Refraction varies with environment conditions, such as humidity, temperature, barometric pressure, and air density. For example, a radio signal bends closer to the earth at night than during the day due to the increased moisture in the lower atmosphere that results from condensation. In fact, most path fading caused by refraction occurs between midnight and 7:00 am.

The refraction index, or K Factor, describes how a radio wave bends in relation to the earth’s surface. In general, a Path Profile will use K = 4/3 to determine the effects of refraction on a proposed radio link.

Commonly Used Capacity Configurations in MW Radio 4 x 2 Mbps or 4 x E1 8 x 2 Mbps or 8 x E1 16 x 2 Mbps or 16 x E1 155 Mbps or STM1

In microwave link there are mainly two types of transmission (Tx) technologies:

Plesiochronous Digital Hierarchy (PDH) Synchronous Digital Hierarchy (SDH)

Q. What is meant by "Plesiochronous"?

If two digital signals are Plesiochronous, their transitions occur at "almost" the same rate, with any variation being constrained within tight limits. These limits are set down in ITU-T recommendation G.811. For example, if two networks need to interwork, their clocks may be derived from two different PRCs. Although these clocks are extremely accurate, there's a small frequency difference between one clock and the other. This is known as a plesiochronous difference.

Q. What is meant by "Synchronous"?

In a set of Synchronous signals, the digital transitions in the signals occur at exactly the

same rate. There may however be a phase difference between the transitions of the two signals, and this would lie within specified limits. These phase differences may be due to propagation time delays, or low-frequency wander introduced in the transmission network. In a synchronous network, all the clocks are traceable to one Stratum 1 Primary Reference Clock (PRC).

Plesiochronous Digital Hierarchy (PDH)

There are three separate standards for PDH:

CEPT Standards (Committee of European Posts and Telegraph) Min packet size is 2Mbps (30 voice channels or 32´64kbps - 2 channels reserved for

signaling and related Tx info) also called E1 Further multiples such as 8Mbps (120 channels), 34Mbps (480 channels),

140Mbps(1920 channels) were standardised by ITU-T. These different Tx capacities are called Tx hierarchies. Each step, apart from data capacity, also contains some info for handling the data e.g. destination addresses. Higher value systems working at 565Mbps are also available as proprietary equipment

USA Standards Basic packet capacity - 1.5Mbps corresponding to 24 voice calls (also called T1) Later extended to 6Mbps (96 channels) and 45Mbps(672 channels)

Japan’s Standards Basic packet capacity - 1.5Mbps (like USA) Later expanded to 32Mbps (480 channels), 100Mbps (1,440 channels) and 400Mbps

(5,760 channels) & 1.6Gbps (23,040 channels)Comparison of Multiplexing Hierarchies

CEPT & USA Standards are most popular

This multiplexing hierarchy appears simple enough in principle but there are complications. When multiplexing a number of 2 Mbit/s channels they are likely to have been created by different pieces of equipment, each generating a slightly different bit rate. Thus, before these 2 Mbit/s channels can be bit interleaved they must all be brought up to the same bit rate adding 'dummy' information bits, or 'justification bits'. The justification bits are recognize as such when demultiplexing occurs, and discarded, leaving the original signal. This process is known as plesiochronous operation, from Greek, meaning "almost synchronous". The same problems with synchronization, as described above, occur at every level of the multipexing hierarchy, so justification bits are added at each stage. The use of plesiochronous operation throughout the hierarchy has led to adoption of the term "plesiochronous digital hierarchy", or PDH.

Details of PDH Signals:

Signal Digital Bit Rate Channels

E0 64 kbit/s One 64 kbit/s

E1 2.048 Mbit/s 32 E0

E2 8.448 Mbit/s 128 E0

E3 34.368 Mbit/s 16 E1

E4 139.264 Mbit/s 64 E1

The main limitations of PDH are:

Inability to identify individual channels in a higher-order bit stream.

Insufficient capacity for network management

Most PDH network management is proprietary

There's no standardised definition of PDH bit rates greater than 140 Mbit/s

There are different hierarchies in use around the world. Specialized interface equipment is required to interwork the two hierarchies

Synchronous Digital Hierarchy (SDH)

SDH stands for Synchronous Digital Hierarchy & is an international Standard for a high capacity optical telecommunications network. It is a synchronous digital transport system aimed at providing a more simple, economical and flexible telecommunication infrastructure.

Q. What led to SDH development ?

Before SDH, the first generations of fibre-optic systems in the public telephone network used proprietary architectures, equipment line codes, multiplexing formats, and maintenance procedures. The users of this equipment wanted standards so they could mix and match equipment from different suppliers

The primary reason for the creation of SDH was to provide a long-term solution for an optical mid-span meet between operators; that is, to allow equipment from different vendors to communicate with each other. This ability is referred to as multi-vendor interworking and allows one SDH-compatible network element to communicate with another, and to replace several network elements, which may have previously existed solely for interface purposes.

Traditionally, digital transmission systems and hierarchies have been based on multiplexing signals which are plesiochronous (running at almost the same speed). Also, various parts of the world use different hierarchies which lead to problems of international interworking; for example, between those countries using 1.544 Mbit/s systems (U.S.A. and Japan) and those using the 2.048 Mbit/s system.

Details of SDH Signals:

Bit Rate Abbreviated SDH SDH Capacity

51.84 Mbit/s 51 Mbit/s STM-0 21 E1

155.52 Mbit/s 155 Mbit/s STM-1 63 E1 or 1 E4

622.08 Mbit/s 622 Mbit/s STM-4 252 E1 or 4 E4

2488.32 Mbit/s 2.4 Gbit/s STM-16 1008 E1 or 16 E4

9953.28 Mbit/s 10 Gbit/s STM-64 4032 E1 or 64 E4

39813.12 Mbit/s 40 Gbit/s STM-256 16128 E1 or 256 E4

STM = Synchronous Transport Module

Q. What are the advantages of SDH over PDH?

The increased configuration flexibility and bandwidth availability of SDH provides significant advantages over the older telecommunications system.

These advantages include:

A reduction in the amount of equipment and an increase in network reliability.

The provision of overhead and payload bytes - the overhead bytes permitting management of the payload bytes on an individual basis and facilitating centralized Fault sectionalisation, nearly 5% of signal structure allocated for this purpose.

The definition of a synchronous multiplexing format for carrying lower-level digital signals (such as 2 Mbit/s, 34 Mbit/s, 140 Mbit/s) which greatly simplifies the interface to digital switches, digital cross-connects, and add-drop multiplexers.

The availability of a set of generic standards, which enable multi-vendor interoperability.

The definition of a flexible architecture capable of accommodating future applications, with a variety of transmission rates. Existing & future signals can be accommodated.

Various steps in multiplexing?

The multiplexing principles of SDH follow, using these terms and definitions:

Mapping:

A process used when tributaries are adapted into Virtual Containers (VCs) by adding justification bits and Path Overhead (POH) information.

Aligning:

This process takes place when a pointer is included in a Tributary Unit (TU) or an Administrative Unit (AU), to allow the first byte of the Virtual Container to be located.

Multiplexing:

This process is used when multiple lower-order path layer signals are adapted into a higher-order path signal, or when the higher-order path signals are adapted into a Multiplex Section.

Stuffing:

As the tributary signals are multiplexed and aligned, some spare capacity has been designed into the SDH frame to provide enough space for all the various tributary rates. Therefore, at certain points in the multiplexing hierarchy, this space capacity is filled with "fixed stuffing" bits that carry no information, but are required to fill up the particular frame.

1+1 protection:

In 1+1 protection switching, there is a protection facility (backup line) for each working facility At the near end the optical signal is bridged permanently (split into two signals) and sent over both the working and the protection facilities simultaneously, producing a working signal and a protection signal that are identical. At the Far End of the section, both signals are monitored independently for failures. The receiving equipment selects either the working or the protection signal. This selection is based on the switch initiation criteria which are either a signal fail (hard failure such as the loss of frame (LOF) within an optical signal), or a signal degrade (soft failure caused by the error rate exceeding some pre-defined value).

1:N protection:

In 1:N protection switching, there is one protection facility for several working facilities (the range is from 1 to 14). In 1:N protection architecture, all communication from the Near End to the Far End is carried out over the APS channel, using the K1 and K2 bytes. All switching is revertive; that is, the traffic reverts to the working facility as soon as the failure has been corrected. In 1:N protection switching, optical signals are normally sent only over the working facilities, with the protection facility being kept free until a working facility fails.

Standard Network Topologies

Star Advantages:

Optimised cost of paths Simple NMS

Disadvantages:o No Protection Patho Centre determines the performance of the whole NWo No optimised BW

TreeAdvantages:

Clear Hierarchies Simple NMS

Disadvantages:o No Protection Patho Failure of one branch separates whole NW parts

RingAdvantages:

High Availability Simple NMS

Disadvantages:o No. of elements depends on ring capacity and traffic relationso Connected rings increase complexity

MeshAdvantages:

High Availability High Flexibility Optimised paths Optimised BW

Diadvantages:o Complex NMS

Common Network Architectures

For N Stations N-1 Links are required Nth station depends on N-1 Links

• For N Stations N-1 Links are required• Each Station depends on Only 1 Link

For N Stations N Links are required Route Diversity is available for all stations

Each Station is Connected to Every Other Full Proof Route Protection

Typical Network Consist of Rings and Spurs

Network Routes and Route Capacities

Inter- City routes – Backbone

Backbone routes are planned at Lower Frequency Bands 2, 6 and 7 GHz Frequency Bands are used Backbone routes are normally high capacity routes Nominal Hop Distances 25 – 40 Km

Intra – City routes – Access

Access routes are planned at Higher Frequency Bands 15,18 and 23 GHz Frequency Bands are used Nominal Hop Distance 1 – 10 Km

Few well known MW Radio Manufacturers:

ABB Nera NEC Siemens Digital Microwave Corporation Fujitsu Ericsson Alcatel Lucent Hariss

SDH BackBone Rings

At the National level Reliance Communications has established 7 very high bandwidth Transport Rings, called National BackBone/ Long Distance Rings. Practically there are 11 rings as Ring 1 and 3 comprise 3 rings each (1A, 1B, 1C & 3A, 3B, 3C). These Rings are so designed that all major cities get enough bandwidth and not too many cities come on the same ring. Also having these 11 rings provide enough alternative routes in case of failure in one section. These rings traverse all the 18 circles, touch all major cities and cover about 90% of Indian population.Established (read utilized) Bandwidth of these rings is at 10 GBps, but that’s just tip of the iceberg compared to what we can achieve. What gives these rings such gargantuan bandwidth – OFC - which I will discuss later in this report.These rings connect 22 Core MCN’s. From these rings, at these 22 MCN’s, emerges several Metro Access Rings, which connect other small cities and towns to the NBB.

Network Elements

1. Optical Fiber Cable - Siemens, Corning2. OTDR - Tectorinx3. Fiber Management System Agilent4. SDH Equipment - Nortel, Fibcom5. DWDM Equipment - Nortel6. Sync Equipment - Datum7. Router - STM -256 - Cisco – Juniper8. Transport – TN1C at BTS – STM -1 - Nortel TN1X – STM- 1 TN-4X –STM 4X & TN 16 X / STM-16X Small mux equivalent to TN1C) N6110 – STM-1 - Tejas N6130 - STM - 16 N – 5200 – STM - N 6500 – 10 Gg / STM 649. Cross Connect - Dx -140 Gb/ STM-64 - Nortel HDx -1280 Gb / STM-64 / 80 λ Huawei T- 6040 16λ & 6130 – 40 λ OMS 1684 / 64 / 54 / 40 – Marconi - - - STM 64 to STM 4 (16 port STM- 1) & 4 port – STM-16 card Single port – STM -64

Cross Connect - Dx -140 Gb/ STM-64

Cross connect is connected with more then one links –each link having capacity STM-64 i.e. cross connect Equipment must be capable of controlling all of them simultaneously & that capacity is 140 GB (e.g. A train may be having capacity to carry 1000 passengers but the station should have capacity - much more than that train - to control many trains at a time). The backbone transport provides for connectivity between different LDCAs, SDCAs and cities. In addition interconnect is extended for other NLD, CSP and FSP networks. The core network comprises fully meshed, 7 primary and 14 secondary nodes. Physical architecture of the Core Network comprises of two-tier ring network – Express Ring & Collector Ring. Traffic between major metros and all major node cities is transported on the high capacity transport path – The Express Ring. Traffic from the other LDCA’s (Long Distance Charging Areas) is transported on The Collector Ring. The ring topology provides necessary protection to traffic in terms of alternate path in case of breakage of the optical fibre or equipment failure thus ensuring smooth undisrupted operation of the network.

The functions of the Core-Backbone Network are as follows:

Provide connections, either on permanent basis or temporary basis for the transfer of information in a cost effective, reliable and speedy manner

Routing – which way to send the information Transport – how the information is carried

Ring Elements and Terminologies

In a Ring each node is called an Add-Drop Multiplexer (ADM).

An ADM has grossly three parts:

Tributary - Interfaces with the non-ring nodes to bring in Traffic Payload Manager - Manages multiplexing & de-multiplexing activities Aggregate - Interfaces with the OFC Ring

From MCN’s on the NBB, we get Metro Access Rings - like state highways emerging from thenational highways. These MAR carry the traffic to over 1100 cities and town of the country. Bandwidth of these MAR are in the range of 625 Mbps – 2.5 GBps and upgradeable further with little change in the infrastructure. Nodes on MAR are known as MAN (e.g. SRM (Parel), Andheri MIDC, Chembur). From MAN (Metro Access Nodes) on Metro Access Rings, we get Building Access Rings (like Main Roads inside a City or Town.) These BAR connect various Building Access Nodes. At the BAN, we have the Central Terminals (CT’s) or the Base Transceiver Station (BTS). The CT’s connect several (14 as of today) Remote Terminal Units (RTU’s) which in turn provide Fixed Access. The BTS covers all the Mobile Stations (MS) within it’s radius of coverage, thus providing Wireless Access. Connection right up to the RTU is - through OFC (this is therefore called Fiber To The Building), thus providing enormous bandwidth. These networks are capable of providing both Narrow Band & Broadband services.Transport element on MAN & BAN is known as ADM.

Ring capacity – FTTB – STM-1, BAR - STM 1 to STM – 4 MAR - STM 4 to STM – 16 NBB - STM - 64

Optical Fiber Cable (OFC) Link

Advantages of Optical Fiber

Distance:

The extremely low losses of modern telecom grade fiber enable distances of 50-100Km betweenrepeaters to be routinely achieved.

Capacity/Bandwidth:

The information carrying capacity of optical fiber can be enormous. G-652 has capacity 2.5Gbps/fiber/wave length. It can provide the equivalent of 30,000 individual telephone signals of 64kbit/sec and G-655 has capacity 10Gbps/fiber/wavelength (1000GB/sec is now very close to being achieved).

Security:

Optical fiber systems do not radiate any signal, and hence have almost total immunity to ‘wiretapping’. It can be done but is very difficult unless access to splices or connectors is possible.

Immunity to Noise:

The glass optical fiber is a dielectric rather than a metal and thus does not act as an antenna in the way metal conducting elements do. The fiber will not, therefore suffer from inductive interference such as Radio Interference (RFI), Electromagnetic Interference (EMI), Electromagnetic Pulse (EMP). This effective immunity to interference makes it possible to use fibers alongside or even on power lines.

Long Life:

Fiber does not corrode like metal conductors.

Light Weight:

Optical fiber is remarkably light in weight. A 10Km stand of telecom grade fiber on a shipping spool weighs less than 2kg whereas a 500m reel of co-ax copper cable weighs 30kg.

Environmentally Friendly:

Manufactured from the most abundant material in the earths crust. Comparatively small amounts of raw material are required therefore energy, transport and process costs are reduced. By using fiber for communications the world’s copper reserves are saved for other purposes.

Future Proof:

Maybe yes - maybe no. It is impossible to know, however the signs are encouraging. It lasts a

long time –we only use a small amount of its theoretical capacity—as a result it is probably fair to say that fiber provides our most future proof transmission medium.

Disadvantages:1. OFC is costlier than Cu-wire.2. OFC is fragile.3. OFC are difficult to join.4. OFC has its own set of losses – dispersion, absorption, etc.

An optical fiber is made of three sections: The core that carries the light signals i.e. optic pulse travels in core only The cladding that keeps the light in the core serves the purpose of Compound wall The coating that protects the glass

Fiber dimensions are measured in μm. 1 μm = 0.000001 meters (10-6) 1 human hair ~ 50 μm

Refractive Index (n) n = c / v n ~ 1.468 n (core) > n (cladding) c = 3 x 108 Meter/second

Fiber Geometry

Core:

The core of an optical fiber is a glass rod - denotes the central part of the fiber where the majority of the light propagates.

Cladding:

The cladding of an optical fiber surrounds the core and has a Refractive Index lower than that of core. This difference in refractive index allows total internal reflection to occur within the fiber core and avoids the entry into the Cladding. Total internal reflection is the phenomenon by whichlight propagates in optical fiber.

Coating is made up of PVC material-available in different colours as per ITU code.

If we get an optical tunnel where once a light pulse enters at one end can only come out at the other end, would serve our purpose. An OFC is just that. Transmission through an OFC is like a light ball traveling down a tunnel. It reflects several times on the “wall” before reaching the end of the tunnel.

Snell's law is defined as: n1 sinA1 = n2 sinA2,

Where• n is the refractive index and A the corresponding angles as shown.• The refractive index is the ratio of the speed of light in a vacuum to the speed of light in a

given medium.• n1 = C / V• C = Velocity of light in Vacuum i.e. 3 x 108 metres per second.• V = Velocity of light in a given mediumSo, if the top part of the diagram is CORE & n1 is Refractive Index of the Core material and if the bottom part is Cladding, n2 is Refractive Index of the Cladding material. When light passes from one medium to another, the angles & refractive indexes of the media determined the path that light took. The relationship is a function of the sine of the angles, also known as the “Law of Sines” (by Descartes).

The phenomenon of total internal reflection was discovered by John Tendel in 1854, when he filled a can with water, which had a hole at the lowest level. Obviously water started flowing out of the hole forming a curved projectile path. As Tendell lit a torch at the top of the Can, a portion of that light would come out of the hole at the bottom. These light rays then experience total internal reflection because Refractive Index (n) of water is greater than air. Thus these rays would bend along with the watery projectile path giving rise to the idea that light could travel in a curved path if the phenomenon of TIR is repeated many times.

Optical Fibre Specifications

Optical Spectrum

The Optical Spectrum can be divided into three regions:

Ultra Violet:

That portion of the electromagnetic spectrum in which the longest wavelength is just below the visible spectrum, extending from approximately 4 nm to 400 nm.

Visible Light:

Electromagnetic radiation visible to the human eye; wavelengths of 400-700 nm.

Infrared (IR):

The region of the electromagnetic spectrum bounded by the long wavelength, extreme of the visible spectrum (about 0.7 μm) and the shortest microwaves (about 0.1 μm).

Nowadays to generate different wavelengths pluggable lasers of different Frequency areavailable. In the old days different cards were available for different frequency.

Attenuation

Attenuation is the measure of the reduction in signal magnitude, or loss, along a length of fiber.

Attenuation is one factor which determines the power loss. Attenuation in fiber optic cabling is usually expressed in decibels per unit length of cable

(i.e. dB/km) at a specified wavelength. Attenuation describes how energy is lost or dissipated.

Loss is the cost of moving something, like charges or particles or light pulses.

Attenuation in fiber optic cabling is usually expressed in decibels per unit length of cable (i.e. dB/km) at a specified wavelength.

Attenuation = 10 log10 (Iout / Iin)

Where,Iout = outgoing intensity (intensity is measured in Watt/m-2)Iin = incoming intensity (Watt/m-2)

Sources of Attenuation in Fibers

Absorption (proportional to 1 / λ)

Caused by impurities in the glass, and any atomic defects in the glass increases dramatically above 1700 nm. The peak absorption occurs at approximately 1400nmλ.

Scattering (proportional to 1 / λ4)

Scattering is caused by small variations in the density of glass. Loss of optical energy due to imperfections / in homogeneities (localized density variations). And therefore act as scattering objects.

Geometric Effects (proportional to λ)

Bending losses increases with increase in wavelength. Effects of 2 cm radius bend at three wavelengths.

Scattering and Absorption decides suitability of optical fiber for transmission at specific frequencies only. If a graph of Loss in dB/km is plotted against the wavelength then we observe that, ‘Attenuation varies with the wave length of light.’ The fiber exhibits minimum attenuation at wavelength slots, 1310nm, and 1550nm. These are called, second window and third window.

The second and the third windows are in practical use today, i.e. we don't use the 850 nm any more except for some restricted applications. The 850 nm was in use in the past when the Laser Diodes available were of 850 nm only.

Bending Losses

Wavelength Multiplexing

Large increase in Bandwidth can be achieved by using a technique called Dense Wave Division Multiplexing (DWDM). Suppose we had a one lane HW, only one vehicle can run at a time. If we needed more vehicles to run simultaneously we will have to add more lanes, say 4 or 6 lane or we can construct multistory Highway.

In the above sketch, each lane is equated with different colour of light (violet, blue, green, yellow, orange, red, etc.) .When seven colours are passed through a triangular prism ,it becomes one (Multiplexer theory) and when it will come out it becomes 7 colours again. DWDM uses the above phenomenon, but uses Laser and IR light instead of visible light. The result is the same, only that we can multiplex many more wavelengths and demultiplex them at the receiving end. Normally we can achieve BW 10 GBps with one wavelength, As per DWDM technology, we can go up to 800 GBps by using 80 Wave length, that too in a single fiber of OFC. And we have 48 cores in one cable and 6 such cables that can be laid in our NBB.

DWDM - 1530λ to 1563 λ = C band = Conventional 1570 λ to 1620 λ = L band = Long

DWDM Capacity with G 652 & G 655

G 652

1550 nm can support up to 32 Lambda wave lengths for DWDM The bandwidth per lambda are limited to 2.5Gbps. Total bit rate for 32 Lambda’s is 2.5 X 32Gbps. = 80 Gbps. Good for Short haul applications up to 350 - 400Km and Metro regions. This fiber is used for - City network – Access / SDCA routes

G 655

10 Gbps can be supported per wave length. For DWDM total number of wave length supported is 80 Lambda. Total capacity = 10Gbps x 80 λ = 800Gbps Good for Long haul applications - on NBB / NLD routes.

This is our Reliance India Roadmap. It’s a mega network of 80.000 km of OFC highway connecting 12 rings, 227 LDCA, 565 SDCA, covering 18 telecom circles, extending wireline connectivity to 138 cities and wireless connectivity in 578 cities. Business conducted in these cities constitutes 80% of India’s GDP. It is necessary to monitor the health of such a huge network. This is done by monitoring the health of Dark Fibers by means of Fiber Monitoring System.To the user it means how much competitive rates she/ he pays for a Local or STD call or on internet how fast is the download of an interesting article or favorite song. The core rings connect 22 Core MCN’s with 17 ILT’s at this moment. These are our Life-lines. The subtended rings interconnect some of these MCN’s and function like the Bypasses. Like how healthy you are in indicated by how well your heart is functioning and how good is your blood circulation, similarly the health of a telecom network can be measured by how is the reliability of these transport network is & how much bandwidth these transport network can handle .Like multiple lanes of Highways, Transport network provide bandwidth which decides how much traffic (read how many calls) can be carried. To the user it translates into how much she/ he pays for a short distance or long distance call or how fast is the download of an interesting article or favorite song. This module we will see how we live up to that challenge.

Reliance Optical Network – International

FLAG Telecom develops and operates advanced fibre-optic global cable systems over which it offers a growing range of value-added network services. It operates a global network and provides customers with connectivity to most of the major business centres around the world.

FLAG Europe-Asia is the world's longest privately funded undersea fibre-optic cable system stretching more than 28,000km from the UK to Japan with landing sites in 13 countries.

FLAG Atlantic-1 is the world's first multi-terabit transoceanic dual cable system providing a fully protected city-to-city service between London, Paris and New York.

FLAG North Asian Loop has been designed to support the strong growth in intra-Asia internet traffic and provides intra-regional, city-to-city connectivity between Hong Kong, Seoul, Tokyo and Taipei.

Network Detail – RIC Nodes / Plants

Inter city – NLD - NBB

Backbone Network : 55,000 km. (Inter city)Total Network : 80,000 kmMCN : 260 out of which 198 are Maintenance Point ( MSC = 90 + 6 , ILT Switches = 22 )IS : 206Preside Server : At Mumbai & Hyderabad

Intra - city

Interconnection Network : 25,000 km. (Intra city)BTS : 7713MANS : 45BANS : 670Wireless : 565 CitiesWireline : 184 Cities

No. of Ducts in National Backbone: 4/6 HDPE ducts Laying of ducts – (20 meters from road center) taking care of all future rearrangements

(eg. Road widening, bridge replacement, etc.) Cable marker stones placed along the route at every 200 m Warning tape placed below 0.5m from the finished grade Tracer wire for ease of detection of fibre placed above duct Buried at 1.65m below the ground along the route (Protection against Rodent) Standardized location of manholes and hand holes Man holes are spaced 4 km apart Hand holes are spaced 1 km apart . Cable slacks have been kept in every manhole (15 meters) and hand hole (10 meters)

from maintenance point of view

Switching

Switch not only reduces transmission cost but also reduces the complexity of connecting subscribers. Here subscribers have complete control on information flow to a subscriber. Similar concept is further extended to route subscribers traffic to long distance exchanges by taking calls through exchanges arranged in tandem. R2MFC – Registered & Registered Multi Frequency Channel.

STP - Signal Transferring point - All switches are connected to STPSCP - Switch Control Panel - available at STP for Database-passes data / information (details of caller & Receiver party) as & when required by STP.

CCS7 – Common Channel Signaling version-7In Dx connections are made for longer time. In switches connections change from call to call.

Switches are intra-network devices designed to increase performance in client/server networks by facilitating LAN segmentation. Because switches can be implemented without changing adapters, cabling, hubs, etc., network investments are preserved. In addition, switches facilitate the creation and management of virtual LANs, a logical grouping of users, independent of their physical location. With switches, ad hoc workgroups can be created, managed, and changed by software rather than hardwiring. Essentially, a LAN switch is a low-latency, multiport bridge that creates separate segments. Switches are used to provide dedicated bandwidth to specific users or server-based groups of users in Ethernet and Token Ring and/or to transition to higher-speed technologies, such as FDDI, Fast Ethernet, Gigabit Ethernet, and/or ATM.

Switches can be used to:

• Interconnect elements of a distributed computing system;• Provide high-speed connections to campus backbones and servers; and• Scale network bandwidth by adding more switched ports.

Switching technology has three principal advantages: scalable bandwidth, flexibility, and high performance. For all these reasons, switches have emerged as the industry’s hottest solution for increasing network bandwidth, providing higher levels of performance, and reducing overall cost of ownership. The common force driving the need for switching is network growth in clients, servers, and applications.

There are no hard and fast rules on where to switch and what technologies to use, but there are some generally accepted guidelines to consider. Switched Ethernet and Token Ring, since they are 10, 4, and 16 Mbps technologies respectively, are best suited for workgroup and departmental deployment. They are also the easiest to implement and most cost effective. Fast Ethernet, which is 100 Mbps, is ideal for connecting servers in workgroups and linking departments to building backbones. Gigabit Ethernet, with its 1000 Mbps speed, will provide even faster connectivity at this level and support super-user workgroups. Fast Ethernet is relatively easy to install and is cost-effective, since it’s based on existing technology and cabling.However, Fast Ethernet does have distance limitations and lower utilization rates, so it’s not ideal for backbone implementation. This backbone is for relatively shorter distances.