training report

A

SIX WEEKS SUMMER TRAINING REPORT

On

TELECOMMUNICATION in

ELECTRONICS & COMMUNICATION ENGINEERING

From

ADVANCE LEVEL TRAAINING IN TELE COMMUNICATION (ALTTC)

GHAZIABAD

Submitted to Submitted by Mr.Sohail Khan Vidyanshu Shankhadhar Roll No.-0723131085

DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGG. R.D. ENGINEERING COLLEGE

GHAZIABD-201206 1

PREFACE

Industrial training is must for every student perusing professional degree because the

ultimate goal of every student is to get the information the industrial training helps us to

get an idea of things.

We should known in order to get a good job i.e. have a good professional carrier.

Industrial training teaches us a lot of things. It helps us to know the kind of environment

we would be getting in an industry and help us to get with the kind of environment.

Industrial training helps us to know what kind of grade an engineer of specific branch

plays in an industry. It help us to get used to working in groups of known people in it teach

us team work because my work in industrial is accomplished by a group and not an

individual.

In totality the industrial teaches us industrial ethics. Some advance technical

knowledge how and help us to acquired with industrial working style.


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ACKNOWLEDGEMENT

Completing a job is never one-man effort. It is often the result of invaluable

contribution of number of individuals in a direct or indirect manner that helps in

sharing or making success.

I take this opportunity to express our deep sense of gratitude and whole hearted

thanks to all faculty members of ALTTC, for their valuable guidance, interest and

affectionate encouragement throughout the work.

Lastly i take this opportunity to thank all those who directly or indirectly helped

me during the course of this task.


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CONTENTS

Training certificate

Acknowledgement……………………………………………………3

1. Intoduction…………………………………………………………….5

Company profile……………………………………………………..5

a. About the company

b. ALTTC vision

c. ALTTC mission

Objective of training

2. PCM Principle

3. Advanced Optical Networks: DWDM

4. MOBILE COMMUNICATION & CELLULAR CONCEPTS

Mobile Communications: Basic concepts

Cellular Concepts

5. GSM Technology

Call Processing in GSM GSM Network structure6. CDMA Technology7. Overview Of Intranet8. Wi-Max9. Wi-Fi10.Conclusion11.Bibliography


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2. PCM PRINCIPLEIntroduction

A long distance or local telephone conversation between two persons could be provided

by using a pair of open wire lines or underground cable as early as early as mid of 19th

century. However, due to fast industrial development and increased telephone awareness,

demand for trunk and local traffic went on increasing at a rapid rate. To cater to the increased

demand of traffic between two stations or between two subscribers at the same station we

resorted to the use of an increased number of pairs on either the open wire alignment, or in

underground cable. This could solve the problem for some time only as there is a limit to the

number of open wire pairs that can be installed on one alignment due to headway

consideration and maintenance problems. Similarly increasing the number of open wire pairs

that can be installed on one alignment due to headway consideration and maintenance

problems. Similarly increasing the number of pairs to the underground cable is uneconomical and

leads to maintenance problems.

It, therefore, became imperative to think of new technical innovations which could

exploit the available bandwidth of transmission media such as open wire lines or underground

cables to provide more number of circuits on one pair. The technique used to provide a number of

circuits using a single transmission link is called Multiplexing.

Multiplexing Techniques

There are basically two types of multiplexing techniques

i. Frequency Division Multiplexing (FDM)

ii Time Division Multiplexing (TDM)

Frequency Division Multiplexing Techniques (FDM)

The FDM technique is the process of translating individual speech circuits (300-3400 Hz)

into pre-assigned frequency slots within the bandwidth of the transmission medium. The

frequency translation is done by amplitude modulation of the audio frequency with an


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appropriate carrier frequency. At the output of the modulator a filter network is connected to

select either a lower or an upper side band. Since the intelligence is carried in either side band,

single side band suppressed carrier mode of AM is used. This results in substantial saving of

bandwidth mid also permits the use of low power amplifiers. Please refer Fig. 1.

FDM techniques usually find their application in analogue transmission systems. An

analogue transmission system is one which is used for transmitting continuously varying signals.

Fig. 1 FDM Principle

Time Division Multiplexing

Basically, time division multiplexing involves nothing more than sharing

a transmission medium by a number of circuits in time domain by establishing a sequence of

time slots during which individual channels (circuits) can be transmitted. Thus the entire

bandwidth is periodically available to each channel. Normally all time slots1 are equal in length.

Each channel is assigned a time slot with a specific common repetition period called a frame

interval. This is illustrated in Fig. 2.


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Fig. 2 Time Division Multiplexing

Each channel is sampled at a specified rate and transmitted for a fixed duration. All channels

are sampled one by, the cycle is repeated again and again. The channels are connected to

individual gates which are opened one by one in a fixed sequence. At the receiving end also

similar gates are opened in unison with the gates at the transmitting end.

The signal received at the receiving end will be in the form of discrete

samples and these are combined to reproduce the original signal. Thus, at a given instant of

time, only one channel is transmitted through the medium, and by sequential sampling a number of

channels can be staggered in time as opposed to transmitting all the channel at the same time as

in EDM systems. This staggering of channels in time sequence for transmission over a

common medium is called Time Division Multiplexing (TDM).

Pulse Code Modulation

It was only in 1938; Mr. A.M. Reaves (USA) developed a Pulse Code Modulation

(PCM) system to transmit the spoken word in digital form. Since then digital speech

transmission has become an alternative to the analogue systems.


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PCM systems use TDM technique to provide a number of circuits on the same

transmission medium viz. open wire or underground cable pair or a channel provided by carrier,

coaxial, microwave or satellite system.

Basic Requirements for PCM System

To develop a PCM signal from several analogue signals, the following processing

steps are required

• Filtering

• Sampling

• Quantization

• Encoding

• Line Coding

Signaling In Telecommunications

The term signaling, when used in telephony, refers to the exchange of control information

associated with the establishment of a telephone call on a telecommunications circuit. An

example of this control information is the digits dialed by the caller, the caller's billing number,

and other call-related information.

When the signaling is performed on the same circuit that will ultimately carry the

conversation of the call, it is termed Channel Associated Signaling (CAS). This is the case for

earlier analogue trunks, MF and R2 digital trunks, and DSS1/DASS PBX trunks.

In contrast, SS7 signaling is termed Common Channel Signaling (CCS) in that the path

and facility used by the signaling is separate and distinct from the telecommunications channels

that will ultimately carry the telephone conversation. With CCS, it becomes possible to exchange

signaling without first seizing a facility, leading to significant savings and performance increases

in both signaling and facility usage.


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3. ADVANCED OPTICAL NETWORKS: DWDM

Introduction

The revolution in high bandwidth applications and the explosive growth of the Internet, however,

have created capacity demands that exceed traditional TDM limits. To meet growing demands

for bandwidth, a technology called Dense Wavelength Division Multiplexing (DWDM) has been

developed that multiplies the capacity of a single fiber. DWDM systems being deployed today

can increase a single fiber’s capacity sixteen fold, to a throughput of 40 Gb/s. The emergence of

DWDM is one of the most recent and important phenomena in the development of fiber optic

transmission technology. Dense wavelength-division multiplexing (DWDM) revolutionized

transmission technology by increasing the capacity signal of embedded fiber. One of the major

issues in the networking industry today is tremendous demand for more and more bandwidth.

Before the introduction of optical networks, the reduced availability of fibers became a big

problem for the network providers. However, with the development of optical networks and the

use of Dense Wavelength Division Multiplexing (DWDM) technology, a new and probably, a

very crucial milestone is being reached in network evolution. The existing SONET/SDH network

architecture is best suited for voice traffic rather than today’s high-speed data traffic. To upgrade

the system to handle this kind of traffic is very expensive and hence the need for the

development of an intelligent all-optical network. Such a network will bring intelligence and

scalability to the optical domain by combining the intelligence and functional capability of

SONET/SDH, the tremendous bandwidth of DWDM and innovative networking software to

spawn a variety of optical transport, switching and management related products.

In traditional optical fiber networks, information is transmitted through optical fiber by a single

light beam. In a wavelength division multiplexing (WDM) network, the vast optical bandwidth

of a fiber (approximately 30 THz corresponding to the low-loss region in a single-mode optical

fiber) is carved up into wavelength channels, each of which carries a data stream individually.

The multiple channels of information (each having a different carrier wavelength) are transmitted

simultaneously over a single fiber. The reason why this can be done is that optical beams with

different wavelengths propagate without interfering with one another. When the number of


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wavelength channels is above 20 in a WDM system, it is generally referred to as Dense WDM or

DWDM.

DWDM technology can be applied to different areas in the telecommunication networks, which

includes the backbone networks, the residential access networks, and also the Local Area

Networks (LANs). Among these three areas, developments in the DWDM-based backbone

network are leading the way, followed by the DWDM-based LANs. The development on

DWDM-based residential access networks seems to be lagging behind at the current time.

Development Of DWDM Technology

Early WDM began in the late 1980s using the two widely spaced wavelengths in the 1310 nm

and 1550 nm (or 850 nm and 1310 nm) regions, sometimes called wideband WDM. The early

1990s saw a second generation of WDM, sometimes called narrowband WDM, in which two to

eight channels were used. These channels were now spaced at an interval of about 400 GHz in

the 1550-nm window. By the mid-1990s, dense WDM (DWDM) systems were emerging with 16

to 40 channels and spacing from 100 to 200 GHz. By the late 1990s DWDM systems had

evolved to the point where they were capable of 64 to 160 parallel channels, densely packed at

50 or even 25 GHz intervals.

As fig. 1 shows, the progression of the technology can be seen as an increase in the number of

wavelengths accompanied by a decrease in the spacing of the wavelengths. Along with increased

density of wavelengths, systems also advanced in their flexibility of configuration, through add-

drop functions, and management capabilities.


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Figure 1 Evolution of DWDM

Varieties Of WDM

Early WDM systems transported two or four wavelengths that were widely spaced. WDM and

the “follow-on” technologies of CWDM and DWDM have evolved well beyond this early

limitation.

WDM

Traditional, passive WDM systems are wide-spread with 2, 4, 8, 12, and 16 channel counts

being the normal deployments. This technique usually has a distance limitation of less than

100 km.

CWDM

Today, coarse WDM (CWDM) typically uses 20-nm spacing (3000 GHz) of up to 18

channels. The CWDM Recommendation ITU-T G.694.2 provides a grid of wavelengths for

target distances up to about 50 km on single mode fibers as specified in ITU-T

Recommendations G.652, G.653 and G.655. The CWDM grid is made up of 18 wavelengths

defined within the range 1270 nm to 1610 nm spaced by 20 nm.

DWDM


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Dense WDM common spacing may be 200, 100, 50, or 25 GHz with channel count reaching

up to 128 or more channels at distances of several thousand kilometers with amplification

and regeneration along such a route.

DWDM System Components

Figure 3 shows an optical network using DWDM techniques that consists of five main

components:

1. Transmitter (transmit transponder):

- Changes electrical bits to optical pulses

- Is frequency specific

- Uses a narrowband laser to generate the optical pulse

2. Multiplexer/ demultiplexer:

- Combines/separates discrete wavelengths

3. Amplifier:

- Pre-amplifier boosts signal pulses at the receive side

- Post-amplifier boosts signal pulses at the transmit side (post amplifier) and on the

receive side (preamplifier)

- In line amplifiers (ILA) are placed at different distances from the source to provide

recovery of the signal before it is degraded by loss.

- EDFA (Erbium Doped Fiber Amplifier) is the most popular amplifier.

4. Optical fiber (media):

- Transmission media to carry optical pulses

- Many different kinds of fiber are used

5. Receiver (receive transponder)

- Changes optical pulses back to electrical bits


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- Uses wideband laser to provide the optical pulse

Figure 3: DWDM System Components

Benefits of DWDM

• Increases bandwidth (speed and distance)

• Does not require replacement or upgrade their existing legacy systems

• Provides "next generation" technologies to meet growing data needs

• Less costly in the long run because increased fiber capacity is automatically available;

don't have to upgrade all the time.


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4. Mobile Communication & Cellular Concepts

Mobile communications: Basic concepts

From ancient to modern times, mankind has been looking for means of long distance communications. For centuries, letter proofed to be the most reliable way to transmit information. Fire, flags, horns, etc. were used to transmit information faster. Technical improvements in the 19th century simplified long distance communications: Telegraphy, and later on telephony. Both techniques were wire line. In 1873, J.C.Maxwell laid the foundation of the electro-magnetic theory by summarizing empirical results in four equations, which are still valid today. It would however be several decades before Marconi made economic use of this theory by developing devices for wireless transmission of Morse signals (about 1895). Voice was transmitted the first time in 1906 (R. Fesseden), and one of the first radio broadcast transmission 1909 in New York.

The economically most successful wireless application in the first half of the 20th century was radio broadcast. There is one transmitter, the so-called radio station. Information, such as news, music, etc. is transmitted from the radio station to the receiver equipment, the radio device. This type of one-way transmission is called simplex transmission. The transmission takes place only in one direction, from the transmitter to the receiver.

The first commercial wireless car phone telephone service started in the late 1940 in St. Louise, Missouri (USA). It was a car phone service, because at this time, the mobile phone equipment was bulky and heavy. Actually, in the start-up, it filled the whole back of the car. But it was a real full duplex transmission solution. In the 50ies, several vehicle radio systems were also installed in Europe. These systems are nowadays called single cell systems. The user data transmission takes place between the mobile phone and the base station (BS). A base station transmits and receives user data. While a mobile phone is only responsible for its user’s data


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transmission and reception, a base station is capable to handle the calls of several subscribers simultaneously. The transmission of user data from the base station to the mobile phone is called downlink (DL), the transmission from the mobile phone to the base station uplink (UL) direction. The area, where the wireless transmission between mobile phones and the base station can take place, is the base stations supply area, called cell. For conversation, a technical solution is required, where the information flow can take place in two directions. This type of transmission is called duplex transmission. Walky-talky was already available the early 30ies. This system already allowed a transmission of user data in two directions, but there was a limitation: The users were not allowed to transmit at the same time. In words, you could only receive or transmit user information. This type of transmission is therefore often called semi-duplex transmission. For telephony services, a technical solutions is required, where subscribers have the impression, that they can speak (transmit) and hear (receive) simultaneously. This type of transmission solution is regarded as full duplex transmission.

Single cell systems are quite limited. The more and more distant the subscriber is from the base station, the lower the quialty of the radio link. If the subscriber is leaving the supply area of the cell, on communication is possible any more. In other words, the mobile communication service was only available within the cell. In order to overcome this limitation, cellular systems were introduced. A cellular mobile communication system consists of several cells, which can overlap. By doing so, a whole geographical area can be supported with the mobile communication service.


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Cell = supply area

Uplink (UL)

Base station

Downlink (DL)

But what happens, when a subscriber moves during moves during a call from one cell to another cell? It would be very annoying, if the call is dropped. If the subscriber is leaving a cell, and in parallel is entering a new cell, then the system makes new radio resource available in the neighboring cell, and then the call is handed over from on cell to the next one. By doing so, service continuation is guaranteed, even when the subscriber is moving. The process is called handover (HO).

A handover takes place during a call, i.e. when the mobile phone is in active (dedicated) mode. A mobile phone can also be in idle mode. In this case, the mobile phone is switched on, but no resources are allocated to it to allow user data transmission. In this mode, the mobile phone is still listening to information, broadcasted by the base station. Why? Imagine, there is a mobile terminated call. The mobile phone is then paged in the cell. This means the phone receives information that there is a mobile terminated call. A cellular system may consist of hundreds of cells. If the mobile network does not know, in which cell the mobile phone is located, it must be paged in all of them. To reduce load on networks, paging in is done in small parts of a mobile an operators network. Mobile network operators group cells in administrative units called location areas (LA). A mobile phone is paged in only one location area.But how does the cellular system know, in which location area the mobile phone is located? And how does the mobile phone know? In every cell, system information is continuously transmitted. The system information includes the location area information. In the idle mode, the mobile phone is listening to this system information. If the subscriber moves hereby from one cell to the next cell, and the new cell belongs to the same location area, the mobile stays idle. If the new cell belongs to a new location area, then the mobile phone has to become active. It starts a communication with the network, information it about it new location. This is stored in databases within the mobile network, and if there is a mobile terminated call, the network knows where to page the subscriber.


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Service continuation without interruption

Mobile phone is active, e.g. a call takes place

Cellular Concepts

Traditional mobile service was structured similar to television broadcasting: One very powerful transmitter located at the highest spot in an area would broadcast in a radius of up to fifty kilometers. The Cellular concept structured the mobile telephone network in a different way. Instead of using one powerful transmitter many low-powered transmitter were placed through out a coverage area. For example, by dividing metropolitan region into one hundred different areas (cells) with low power transmitters using twelve conversation (channels) each, the system capacity could theoretically be increased from twelve conversations using one hundred low power transmitters.

The cellular concept employs variable low power levels, which allows cells to be sized according to subscriber density and demand of a given area. As the populations grows, cells can be added to accommodate that growth. Frequencies used in one cell cluster can be reused in other cells. Conversations can be handed over from cell to cell to maintain constant phone service as the user moves between cells.

Cells :A cell is the basic geographic unit of cellular system. The term cellular comes

from the honeycomb areas into which a coverage region is divided. Cells are base stations transmitting over small geographic areas that are represented as hexagons. Each cell size varies depending upon landscape. Because of constraint imposed by natural terrain and man-made structures, the true shape of cell is not a perfect hexagon.

A group of cells is called a cluster. No frequencies are reused in a cluster.

Features of Digital Cellular Systems:

n Small cells n Frequency reuse n Small, battery-powered handsets n Performance of handovers


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Cellular System Characteristics

General

characteristics of digitalcellular systems

Cellular radio systems allow the subscriber to place and receive telephone calls over the wire-line telephone network where ever cellular coverage is provided. Roaming capabilities extend service to users traveling outside their “outside” home service areas.

The distinguishing features of digital cellular systems compared to other mobile radio systems are:

Small cells A cellular system uses many base stations with relatively small coverage radii (on the order of a 100 m to 30 km).

Frequency reuseThe spectrum allocated for a cellular network is limited. As a result

there is a limit to the number of channels or frequencies that can be

used. For this reason each frequency is used simultaneously by

multiple base-mobile pairs. This frequency reuse allows a much higher

subscriber density per MHz of spectrum than other systems. System

capacity can be further

increased by reducing the cell size (the coverage area of a single base station), down to radii as small as 200 m.

Small, battery-powered handsets In addition to supporting much higher densities than previous systems, this approach enables the use of small, battery-powered handsets with a radio frequency that is lower than the large mobile units used in earlier systems.

Performance of handovers

In cellular systems, continuous coverage is achieved by executing a “handover” (the seamless transfer of the call from one base station to another) as the mobile unit crosses cell boundaries. This requires the mobile to change frequencies


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under control of the cellular network.

Frequency Reuse :

Why frequencyreuse

Cell clustering

The spectrum allocated for a cellular network is limited. As a result there is a limit to the number of frequencies or channels that can be used. A cellular network can only provide service to a large number of subscribers, if the channels allocated to it can be reused. Channel reuse is implemented by using the same channels within cells located at different positions in the cellular network service area.

Radio channels can be reused provided the separation between cells containing the same channel set is far enough apart so that co-channel interference can be kept below acceptable levels most of the time. Cells using the same channel set are called co-channel cells.

The figure on the opposite page shows an example. Within the service area (PLMN), specific channel sets are reused at a different location (another cell). In the example, there are 7 channel sets: A through G. Neighboring cells are not allowed to use the same frequencies. For this reason all channel sets are used in a cluster of neighboring cells. As there are 7 channel sets, the PLMN can be divided into clusters of 7 cells each. The figure shows three clusters.

The number of channel sets is called K. K is also called the reuse factor. In the figure, K=19. Valid values of K can be found using equation (where i and j are integers):

K=i²+j²+I*j

Explaining this equation is beyond the scope of this course. Some constraints to K are provided later in this chapter.

Note that in the example:

Cells are shaped ideally (hexagons). The distance between cells using the same channel set is

always the same.


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Capacity/Performance Trade-offs :

n If K increases, then performance increases

n If K increases, then call capacity decreases per cell

The number of sites to cover a given area with a given high traffic density, and hence the cost of the infrastructure, is determined directly by the reuse factor and the number of traffic channels that can be extracted from the available spectrum. These two factors are compounded in what is called spectral efficiency of the system. Not all systems allow the same performance in this domain: they depend in particular on the robustness of the radio transmission scheme against interference, but also on the use of a number of technical tricks, such as reducing transmission during the silences of a speech communication. The spectral efficiency, together with the constraints on the cell size, determines also the possible compromises between the capacity and the cost of the infrastructure. All this explains the importance given to spectral efficiency.

Many technical tricks to improve spectral efficiency were conceived during the system design and have been introduced in GSM. They increase the complexity, but this is balanced by the economical advantages of a better efficiency. The major points are the following:

The control of the transmitted power on the radio path aims at minimizing the average power broadcast by mobile stations as well as by base stations, whilst keeping transmission quality above a given threshold. This reduces the level of interference caused to the other communications;

Frequency hopping improves transmission quality at slow speeds through frequency diversity, and improves spectral efficiency through interferer diversity;

Discontinuous transmission, where by transmission is suppressed when possible, allows a reduction in the interference level of other communications. Depending on the type of user information transmitted, it is possible to derive the need for effective transmission. In the case of speech, the mechanism called VAD (Voice Activity Detection) allows transmission requirements to be reduced by an important factor (typically, reduced by half);

The mobile assisted handover, whereby the mobile station provides measurements concerning neighboring cells, enables efficient handover decision


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algorithms aimed at minimizing the interference generated by the cell (whilst keeping the transmission quality above some threshold).

5. GSM Technology

INTRODUCTION

A GSM system is basically designed as a combination of three major subsystems: the

network subsystem, the radio subsystem, and the operation support subsystem. In order to ensure

that network operators will have several sources of cellular infrastructure equipment, GSM

decided to specify not only the air interface, but also the main interfaces that identify different

parts. There are three dominant interfaces, namely, an A interface between MSC and the Base

Station Control (BSC), an A-bis interface between BSC and the Base Transceiver Station (BTS),

and an Um interface between the BTS and MS.

Call Processing in GSM

In this we discuss the call processing aspect and look into specifics case of a mobile originated (MO) call and a mobile terminated (MT) call. We also look into short message (SMS) and voice mail service (VMS) as implemented IMPCS pilot project.

RF channel overview: - RF channel play important role in call processing case. These are basically three types of RF control channel.

1. Broadcast control channel : The broadcast channels are points to multi-point channel, which are defined only for down-link direction (BTS to mobile station). They are divided into:

BCCH (Broad cast control channel:- BCCH acts as a beacon. It informs the mobile about system configuration parameters (e.g. LAI, CELL IDENTITY, NEIGHBOURING CELL). Using this information MS choose the best cell to attach to.

BCCH is always transmitted on full power and it is never frequency hopped.


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FCCH frequency correction channel. MS must tune to FCCH to listen to BCCH. FCCH transmits a constant frequency shift of the radio carrier that is used by the MS for frequency correction.

SCH (synchronization channel). . SCH is used to synchronize the MS in time .SCH carries TDMA frame number and BSIC (Base Station Identity Code)

2. Common control channels : Common control channels are specified as point to multi-point, which operate only in one direction either in up-link or down-link direction.

PCH (Paging Channel): - PCH is used in down-link direction for sending paging message to MS whenever there is incoming call.

RACH (Random Access Channel ) :-RACH is used by the MS to request allocation of a specific dedicated control channel (SDCCH) either in response to a paging message or for call origination /registration from the MS. this is an up-link channel and operate in point to point mode.

AGCH (Access Grant Channel ):- AGCH is a logical control channel which is used to allocated a specific dedicated control channel (SDCCH) to MS when MS request for a channel over RACH. AGCH is used in downlink direction.

3.Dedicated Control Channel : dedicated control channel are full duplex, point to point channel. They are used for signalling between the BTS and certain MS. They are divided into: -

(I). SACCH (Slow Associated Control Channel): the SACCH is a duplex channel, which is always allocated to TCH or SDCCH. The SACCH is used for

- Radio link supervision measurements.- Power control.- Timing advance information.

In 26 frame traffic multi-frame 13th frame (frame no .12) is used for SACCH.SACCH is used only for non-urgent procedures.

(II). FACCH (Fast Associated Control Channel). FACCH is requested in case the requirement of signaling is urgent and signaling requirement can not be met by SACCH. This is the case when hand-over is required during conversation phase. During the call FACCH data is transmitted over allocated TCH instead of traffic data. This is marked by a flag known as stealing flag.


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(III). SDCCH (Stand Alone Dedicated Control Channel)- The SDCCH is a duplex, point to point channel which is used for signaling in higher layer. It carries all the signaling between BTS & MS when no TCH is allocated to MS. The SDCCH is used for service request, location updates, subscriber authentication, ciphering. equipment validation and assignment of a TCH.

Mobile originated (MO) call: - There are four distinct phase of a mobile originated call- -Setup phase.

-Ringing phase.-Conversation phase.-Release phase.

Out of these phases the setup phase is the most important phase and includes authentication of the subscriber, Ciphering of data over radio interface, validation of mobile equipment, validation of subscriber data at VLR for requests service and assignment of a voice channel on A-interface by MSC. Whenever MS wants to initiate on outgoing call or want to send an SMS it requested for a channel to BSS over RACH. On receiving request from MS, BSS assigns a stand-alone dedicated control channel (SDCCH) to MS over access grant channel (AGCH). Once a SDCCH has been allocated to MS all the call set up information flow takes place over SDCCH. A connection management (CM) entity initiates a CM Service Request message to the network. Network tries to establish an MM connections between the MS and the network and upon successful establishment of MM connection a CM Service Accept message is received by MS from the network. MS now sends a Call Set up Request to the network which contains the dialed digits (DD) of the called party. As the call setup message is received at the MSC/VLR certain check are performed at MSC/VLR like- whether the requested service is provisioned for the subscriber or not, whether the dialed digits are sufficient or not, any operator determined barring (ODB) does not allow call to proceed further etc. As these checks are performed at MSC/VLR a Call Proceeding Message is sent from the network towards the MS. After all the checks are successfully passed MSC sends Assignment command to the BSS which contains a free voice channel on A-interface On getting this message BSS allocates a free TCH to the MS and informs the MS to attach to it. MS on attaching to this TCH informs the BSS about it. On receiving a response from the BSS, MSC switches the speech path toward the calling MS. Thus at the end of Assignment the speech path is through from MS to MSC. It is important to note that at this stage mobile has not connected user connection as yet. MS at this stage does not listen anything.

When the destination party goes off hook, PSTN informs the MSC of this event. At this point, MS is connected to the destination party and billing is started. MSC informs the MS that connection has been established and MS acknowledges the receipts of the connect message.

Under normal condition, the termination of a call is MS initiated or network initiated. In this scenario, we have assumed that MS initiates the release of the call by pressing “end” button


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and MS send a disconnect message to the MSC. The PSTN party is notified of the termination of the call by a release message from the MSC. The end- to- end connection is terminated. When MSC is left with no side task (e.g. charging indication etc.) to complete a release message is sent to the MS. MS acknowledges with a release complete message. All the resources between MSC and the MS are released completely.

Mobile Terminated (MT) call - The different phases of a mobile terminated call are

- Routing analysis - Paging. - Call setup. - Call release.

The phases of mobile terminated (MT) call are similar to a mobile originated (MO) call except routing analysis and paging phase. Call to a mobile subscriber in a PLMN first comes to gateway MSC (GMSC). GMSC is the MSC, which is the capable of querying HLR for subscriber routing information. GMSC need not to be part of home PLMN, though it is normal practice to have GMSC as part of PLMN in commercially deployed networks.

GMSC opens a MAP (Mobile Application Part) dialogue towards HLR and Send / Routing / Info-Request (SRI request) specific service message is sent to HLR. SRI request contains MSISDN of the subscriber. HLR based on location information of this subscriber in its database, opens a MAP dialogue towards VLR and sends Provide / Roaming / Number-request (PRN request)to the VLR. VLR responds to PRN request with PRN response message, which carries an MSRN (mobile subscriber roaming number), which can be used for routing toward visiting MSC in the network. HLR returns MSRN to GMSC (MSC that queried HLR) in SRI response message. On getting MSRN the GMSC routes the call towards VMSC The purpose of this entire exercise is to locate where the terminating mobile subscriber is.

The MSRN received at GMSC is in international format (Country Code + Area Code + subscriber number). Normally, based on the routing info at GMSC, the call may be routed out of the GMSC towards VMSC of the terminating subscriber, in which case appropriate signaling protocol (MF or ISUP) depending on the nature of connecting of GMSC with subsequent exchange along the route will apply. If at VMSC the terminating mobile subscriber is found to be free (idle), paging is initiated for terminating mobile subscriber. MSC uses the LAI provided by the VLR to determine which BSS’s should page the MS. MSC transmit a message to each of these BSS requesting that a page be performed. Included in the message is the TMSI of the MS. Each of the BSS’s broadcasts the TMSI of the mobile in a page message on paging channel (PCH).

When MS detects its TMSI broadcast on the paging channel , it responds with a channel request message over Random Access Channel (RACH). Once BSS receives a channel request message , it allocates a stand –alone Dedicated Control Channel(SDCCH) and forwards this channel assignment information to the MS over Access Grant Channel (AGCH). It is over this


GHAZIABD-201206 24

SDCCH that the MS communicates with the BSS and MSC until a traffic channel assigned to the MS. MS transmits paging response message to the BSS over the SDCCH. Included in this message is MS TMSI and LAI. BSS forwards this paging response message to the MSC. Now Authentication and Ciphering phases are performed to check the authenticity of MS and encrypt data over radio interface.

On the network side after paging is initiated, while waiting for paging response, a defensive timer called, ”Early ACM” timer is run at MSC to avoid network timeouts. On successfully getting paging response, a setup message is constructed to be sent towards terminating MS. In case paging fails due to authentication failure or when the subscriber is out of radio-coverage, the call is cleared.

In case CLIP is not subscribed by the terminating mobile subscriber, calling number is not included in set-up message. In case CLIP is subscribed and PI value in calling number parameter indicates “presentation allowed” the number is included in the set-up message. In case CLIP is subscribed but PI received in calling number parameter indicates “presentation restricted” then number is included only if CLIRO is also subscribed to.

MS on receiving the set-up message performs compatibility Checking before responding to the set-up message – it is possible that MS might be incompatible for certain types of call set-ups. Assuming that MS passes compatibility checking, it acknowledges the call setup with set-up confirm message. After getting set-up confirm message from the MS, MSC performs assignment phase (similar to one discussed in MO call) and a voice path is established from MSC to the MS. MS begins altering the user after it receives the traffic channel assignment. MS send alerting message to the MSC .MSC upon receiving the alerting indication from the MS, begins generating an audible ringing tone to the calling party and sends a network alerting via GMSC to the PSTN. Prior to this the calling party heard silence.

At this point in the call, MS is alerting the called party by generating on audible tone. One of the three events can occur-calling party hangs-up, mobile subscriber answers the phone, or the MSC times out waiting for the mobile subscriber to the answer the call. Since radio traffic channel is a valuable resource, GSM does not allow a MS to ring forever.

In the present scenario we have assumed that the mobile subscriber answers the phone. The MS in response to this action stops alerting and sends a connect message to the MSC. MSC removes the audible tone to the PSTN and connects the PSTN trunk to BSS trunk (terrestrial channel) and sends a connect message via GMSC to the PSTN. The caller and the called party now have a complete talk path. This event typically marks the beginning of the call for billing purposes. MSC sends a connect acknowledge message to the MS.

The release triggered by the land user is done in similar way as the release triggered by mobile user. MSC receives a release message from the network to terminate end-to-end connection. PSTN stops billing the calling landline subscriber. MSC sends a disconnect message towards the MS and MS responds by a Release message. MSC release the connection to the


GHAZIABD-201206 25

PSTN and acknowledges by sending a Release Complete message to PSTN. Now the voice trunk between MSC and BSS is cleared, traffic channel (TCH) is released and the resources are completely released.

The mobile-to-mobile call scenario is a combination of phases encountered in mobile originated (MO) and mobile terminated (MT) call.

5. CDMA Technology

Access Network:

Access network, the network between local exchange and subscriber, in the Telecom

Network accounts for a major portion of resources both in terms of capital and manpower. So

far, the subscriber loop has remained in the domain of the copper cable providing cost effective

solution in past. Quick deployments of subscriber loop, coverage of inaccessible and remote

locations coupled with modern technology have led to the emergence of new Access

Technologies. The various technological options available are as follows:

1. Multi Access Radio Relay

2. Wireless in Local Loop

3. Fiber in the Local Loop

Wireless in Local Loop (WILL)

Fixed Wireless telephony in the subscriber access network also known as Wireless in Local Loop

(WLL) is one of the hottest emerging market segments in global telecommunications today.

WLL is generally used as “the last mile solution” to deliver basic phone service expeditiously

where none has existed before. Flexibility and expediency are becoming the key driving factors

behind the deployment of WILL.

WLL shall facilitate cordless telephony for residential as well as commercial complexes where

people are highly mobile. It is also used in remote areas where it is uneconomical to lay cables

and for rapid development of telephone services. The technology employed shall depend upon

various radio access techniques, like FDMA, TDMA and CDMA.

Different technologies have been developed by the different countries like CT2 from France,

PHS from Japan, DECT from Europe and DAMPS & CDMA from USA. Let us discuss CDMA

technology in WLL application as it has a potential ability to tolerate a fair amount of


GHAZIABD-201206 26

interference as compared to other conventional radios. This leads to a considerable advantage

from a system point of view.

Spread Spectrum Principle:

Originally Spread spectrum radio technology was developed for military use to counter the

interference by hostile jamming. The broad spectrum of the transmitted signal gives rise to

“Spread Spectrum”. A Spread Spectrum signal is generated by modulating the radio frequency

(RF) signal with a code consisting of different pseudo random binary sequences, which is

inherently resistant to noisy signal environment.

A number of Spread spectrum RF signals thus generated share the same frequency spectrum and

thus the entire bandwidth available in the band is used by each of the users using same frequency

at the same time.

Fig-1 CDMA ACCESS – A CONCEPT

On the receive side only the signal energy with the selected binary sequence code is accepted and

original information content (data) is recovered. The other users signals, whose codes do not

match contribute only to the noise and are not “despread” back in bandwidth (Ref Fig-1) This

transmission and reception of signals differentiated by “codes” using the same frequency

simultaneously by a number of users is known as Code Division Multiple Access (CDMA)

Technique as opposed to conventional method of Frequency Division Multiple Access and Time

Division Multiple Access.


GHAZIABD-201206 27

In the above figure, it has been tried to explain that how the base band signal of 9.6 Kbps is

spread using a Pseudo-random Noise (PN) source to occupy entire bandwidth of 1.25 MHz. At

the receiving end this signal will have interference from signals of other users of the same cell,

users of different cells and interference from other noise sources. All these signals get combined

with the desired signal but using a correct PN code the original data can be reproduced back.

CDMA channel in the trans and receive direction is a FDD (Frequency Division Duplexing)

channel. The salient features of a typical CDMA system are as follows:

Frequency of operation: 824-849Mhz and 869-894 MHz

Duplexing Method: Frequency Division Duplexing (FDD)

Access Channel per carrier: Maximum 61 Channels

RF Spacing: 1.25 MHz

Coverage: 5 Km with hand held telephones and approx.

20 Km with fixed units.

Mobile switch center (MSC)


GHAZIABD-201206 28

MSC is a functional entity that performs control and switching to the mobile stations within the

area that it serves, and an automatic connecting device for the subscriber traffic between the

CDMA network and other public networks or other MSCs. MSC is the kernel of the CDMA

cellular mobile communication system, and it is different from a wired switch in that an MSC

must consider the allocation of the wireless resources and the mobility of subscribers, and at least

it must implement the follows processing activities:

1. Location Registration processing;

2. Handoff.

Gateway MSC (GMSC)

When a non-CDMA subscriber calls a CDMA subscriber, the call will first be routed to an MSC,

which will inquires the corresponding HLR and further route the call to the called party’s MSC.

This kind of MSC is called Gateway MSC (GMSC). It is up to the network operator to select

which MSCs as GMSCs.

Visitor location register (VLR)

VLR is responsible for the storage and updating of the subscriber data of mobile stations that

roamed to the service area of this VLR. The VLR is generally configured together with the MSC.

When the mobile station enters a new location area, the MSC will notice the VLR, which will

initiate registration processing to the HLR to update the subscriber location information. The

VLR also stores necessary information for the establishment of calls in the database for the MSC

to search. One VLR can cover one or more MSC areas.

Home location register (HLR)

The HLR provides subscriber information storage and management functions for the mobile

network, including mobile subscriber subscription and cancellation and service authorization and

cancellation. At the same time, it helps in the implementation of subscriber’s call and service

operations. A CDMA can contain one or more HLRs based on the number of subscribers,

equipment capacity and network organization mode, with multi-HLR mode realized in the form


GHAZIABD-201206 29

of virtual HLRs. The subscriber information stored in the HLR includes the following two types

in information:

1. Subscription information

2. Subscriber-related information stored in the HLR

Authentication center (AUC)

Authentication center is a function entity for the management of authentication information

related to the mobile station. It implement mobile subscriber authentication, stores the mobile

subscriber authentication parameters, and is able to generate and transmit the corresponding

authentication parameters based on the request from MSC/VLR. The authentication parameters

in the AUC can be stored in the encrypted form. The authentication center is generally

configured together with the HLR. The authentication parameter stored in the AUC includes:

1. Authentication key (A_KEY);

2. Share secret data (SSD);

3. Mobile identification number/international mobile subscriber identity (MIN/IMSI);

4. Authentication algorithm (AAV);

5. Accounting (COUNT).

Short message center (MC or SC)

As an independent entity in the CDMA cellular mobile communication system, the short

message center works in coordination with other entities such as MSC, HLR to implement the

reception, storing and transfer of the short messages from CDMA cellular mobile

communication system subscribers, and store subscriber-related short message data.

Short message entity (SME)

SME is a function entity for synthesis and analysis of short messages.

Operation and maintenance Center (OMC)

The OMC provides the network operator with network operation and maintenance services,

manages the subscriber information and implements network planning, to enhance the overall


GHAZIABD-201206 30

working efficiency and service quality of the system. There two type of operation and

maintenance centers: OMC-S and OMC-R. An OMC-S is mainly used for the maintenance work

at the mobile switching subsystem (MSS) side; an OMC-R is mainly used for the maintenance

work at the base station subsystem (BSS) side.

Third Generation Standards

CDMA2000/FDD-MC — CDMA2000 using Frequency Division Duplexing-Multicarrier

(FDD-MC) mode. Here multicarrier implies N x 1.25 MHz channels overlaid on N existing

IS-95 carriers or deployed on unoccupied spectrum. CDMA2000 includes:

1. 1x —using a spreading rate of 1.2288 Mcps

2. 3x —using a spreading rate of 3 x 1.2288 Mcps or 3.6864 Mcps

3. 1xEV-DO (1x Evolution - Data Optimized)—using a spreading rate of 1.2288 Mcps

optimized for data

WCDMA/FDD-DS —Wideband CDMA (WCDMA) Frequency Division Duplexing-Direct

Sequence spreading (FDD-DS) mode. This has a single 5 MHz channel. WCDMA uses a

single carrier per channel and employs a spreading rate of 3.84 Mcps.

UTRA TDD/ TD-SCDMA — Universal Mobile Telephone Services Terrestrial

Radio Access (UTRA) and TD-SCDMA. These are Time Division Duplexed

(TDD) standards aimed primarily at asymmetric services used in unpaired (i.e., no

separate uplink and downlink) bands. TD-SCDMA is based on a synchronous

Time Division scheme for TDD and wireless local loop applications. The frame

and slot structure are the same as W-CDMA. However, in TDD mode each slot

can be individually allocated either the uplink or the downlink.


GHAZIABD-201206 31

7. OVERVIEW OF INTRANET

WHAT IS INTRANET

Smaller private version of Internet. It uses Internet protocols to create enterprise-wide

network which may consists of interconnected LANs.

It may or may not include connection to Internet.

Intranet is an internal information system based on Internet technology and web protocols

for implementation within a corporate organization.

This implementation is performed in such a way as to transparently deliver the immense

informational resources of an organization to each individual’s desktop with minimal

cost, time and efforts.

Who needs an Intranet?

In an Intranet environment is used to communicate over two or more networks across different

locations.

1. Users having multi-locations with multi-networks.

2. Users having single locations with multi-networks.

3. Users having single locations with single networks.

What’s really HOT about Intranets?

From a technology point of view, an Intranet is simply beautiful. because:

1. It is scaleable.


GHAZIABD-201206 32

2. It is Interchangeable.

3. It is platform independent

4. It is Hardware independent.

5. It is vendor independent.

Why Intranet for an Organization:

Quick access to voice, video, data and other resources needed by users.

Variety of valuable applications of Intranet applications improve communication and

productivity across all areas of an enterprise.

An Intranet can give immediate access to products specifications, pricing charts and new

collateral’s, sales lead, competitive information and list of customer wins including profit/loss

analysis, thus boosting the success of the business.

A Typical Intranet setup


GHAZIABD-201206 33

Technical Overview Of The Intranet Technology

Intranet runs on open TCP/IP network, enable companies to employ the same type of servers and

browser used for World Wide Web for internal applications distributed over the corporate LAN.

A typical Intranet implementation involves a high end machine called a server which can be

accessed by individual PCs commonly referred to as clients, through the network.

The Intranet site setup can be quite inexpensive, especially if your users are already connected by

LAN. Most popular Intranet web servers can run on a platform widely found in most

organizations. Basic requirements for setting up an intranet site are:

Requirements:

Software:

Server : OS can be Windows server, Unix, LINUX .Web Server s/w should be installed

Client : OS can be Windows workstation, LINUX .Web Browser software

Hardware:

Server: 4 GB RAM, 360 GB secondary storage, Pentium processor with CD ROM.

Client: 1GB RAM, 180 GB Secondary storage, Pentium processor.


GHAZIABD-201206 34

8. Wi-MAX

Introduction:

Broadband wireless sits at the confluence of two of the most remarkable growth stories of the

telecommunications industry in recent years. Both wireless and broadband have on their own

enjoyed rapid mass-market adoption. The staggering growth of the Internet is driving demand for

higher-speed Internet-access services, leading to a parallel growth in broadband adoption.

So what is broadband wireless? Broadband wireless is about bringing the broadband

experience to a wireless context, which offers users certain unique benefits and convenience.

There are two fundamentally different types of broadband wireless services. The first type

attempts to provide a set of services similar to that of the traditional fixed-line broadband but

using wireless as the medium of transmission. This type, called fixed wireless broadband, can be

thought of as a competitive alternative to DSL or cable modem. The second type of broadband

wireless, called mobile broadband, offers the additional functionality of portability, nomadicity

and mobility. Mobile broadband attempts to bring broadband applications to new user experience

scenarios and hence can offer the end user a very different value proposition. Wi-MAX is an

acronym that stands for World-wide Interoperability for Microwave Access and this

technology is designed to accommodate both fixed and mobile broadband applications.

EVOLUTION OF BROADBAND WIRELESS

WiMAX technology has evolved through four stages, albeit not fully distinct or clearly

sequential: (1) narrowband wireless local-loop systems, (2) first-generation line-of-sight (LOS)

broadband systems, (3) second-generation non-line-of-sight (NLOS) broadband systems, and (4)

standards-based broadband wireless systems.


GHAZIABD-201206 35

Wimax And Other Broadband Wireless Technologies

WiMAX is not the only solution for delivering broadband wireless services. WiMAX occupies a

somewhat middle ground between Wi-Fi and 3G technologies when compared in the key

dimensions of data rate, coverage, QoS, mobility, and price. Table provides a summary

comparison of WiMAX with 3G and Wi-Fi technologies.

Table Comparison of WiMAX with Other Broadband Wireless Technologies

Parameter Fixed WiMAX Mobile WiMAX HSPA 1x EV-DO

Rev A

Wi-Fi

Standards IEEE 802.16-

2004

IEEE 802.16e-2005 3GPP Release 6 3GPP2 IEEE 802.11a/g/n

Parameter Fixed WiMAX Mobile WiMAX HSPA 1x EV-DO

Rev A

Wi-Fi

Peak down

link data

rate

9.4Mbps in

3.5MHz with

3:1 DL-to-UL

ratio TDD;

6.1Mbps with

1:1

46Mbps with 3:1 DL-

to-UL ratio TDD;

32Mbps with 1:1

14.4Mbps

using all 15

codes;

7.2Mbps with 10

codes

3.1Mbps;

Rev.

B will support

4.9Mbps

54 Mbpsshared

using 802.11a/g;

more than

100Mbps peak

layer 2 throughput

using 802.11n

Peak uplink

data rate

3.3Mbps in

3.5MHz using

3:1 DL-to-UL

ratio; 6.5Mbps

with 1:1

7Mbps in 10MHz

using 3:1 DL-to-UL

ratio; 4Mbps using

1:1

1.4Mbps

initially;

5.8Mbps later

1.8Mbps


GHAZIABD-201206 36

http://www.wimax.com/commentary/wimax_weekly/1-4-wimax-and-other-broadband-wireless-technologies

Bandwidth 3.5MHz and

7MHz in

3.5GHz band;

10MHz in

5.8GHz band

3.5MHz, 7MHz,

5MHz, 10MHz, and

8.75MHz initially

5MHz 1.25MHz20MHz for

802.11a/g;

20/40MHz for

802.11n

Modulation QPSK, 16

QAM, 64 QAM

QPSK, 16 QAM, 64

QAM

QPSK, 16 QAMQPSK,

8 PSK, 16

QAM

BPSK, QPSK, 16

QAM, 64 QAM

Multiplexin

g

TDM TDM/OFDMA TDM/CDMA TDM/CDMA CSMA

Duplexing TDD, FDD TDD initially FDD FDD TDD

Frequency 3.5GHz and

5.8GHz

initially

2.3GHz, 2.5GHz, and

3.5GHz initially

800 / 900 / 1,800

/ 1,900/ 2,100

MHz

800/900/1,80

0/1,900MHz

2.4GHz, 5GHz

Coverage

(typical)

3–5 miles < 2 miles 1–3 miles 1–3 miles < 100 ft indoors; <

1000 ft outdoors

Mobility Not applicable Mid High High Low

A broad industry consortium, the WiMAX Forum has begun certifying broadband

wireless products for interoperability and compliance with a standard. WiMAX is based on

wireless metropolitan area networking (WMAN) standards developed by the IEEE 802.16 group

and adopted by both IEEE and the ETSI HIPERMAN group.

WiMAX NETWORK ARCHITECTURE


GHAZIABD-201206 37

The WiMAX NWG has developed a network reference model to serve as an architecture

framework for WiMAX deployments and to ensure interoperability among various WiMAX

equipment and operators. The network reference model envisions a unified network architecture

for supporting fixed, nomadic, and mobile deployments and is based on an IP service model.

Below is simplified illustration of an IP-based WiMAX network architecture. The overall

network may be logically divided into three parts:

1. Mobile Stations (MS) used by the end user to access the network.

2. The access service network (ASN), which comprises one or more base stations and one

or more ASN gateways that form the radio access network at the edge.

3. Connectivity service network (CSN), which provides IP connectivity and all the IP core

network functions.

The network reference model developed by the WiMAX Forum NWG defines a number of

functional entities and interfaces between those entities. Fig below shows the logical

representation of the network architecture.


GHAZIABD-201206 38

Mobile Subscriber Station

BS

BS ASN GW(FA)

HA

ASN

CSN

Another ASN

Another Operator’s CSN

NAPNSP

R1

R2

R6

R3

R4

R5

AAA

ASN-ACCESS SERVICES NETWORKNAP-NETWORK ACCESS PROVIDER CSN- CORE SERVICES NETWORKNSP- NETWORK SERVICES PROVIDER BS- BAS STATIONHA-HOME AGENTFA-FOREGN AGENTAAA-AUTHENTICATION AUTHONZATION & ACCOUNTING

Fig. WiMAX Network Reference Model

Base Station (Bs): The BS is responsible for providing the air interface to the MS.

Additional functions that may be part of the BS are micro mobility management functions,

such as handoff triggering and tunnel establishment, radio resource management, QoS policy

enforcement, traffic classification, DHCP (Dynamic Host Control Protocol) proxy, key

management, session management, and multicast group management.

Access Service Network Gateway (Asn-Gw): The ASN gateway typically acts as a layer 2

traffic aggregation point within an ASN. Additional functions that may be part of the ASN

gateway include intra-ASN location management and paging, radio resource management

and admission control, caching of subscriber profiles and encryption keys, AAA client

functionality, establishment and management of mobility tunnel with base stations, QoS and

policy enforcement, foreign agent functionality for mobile IP, and routing to the selected

CSN.

Connectivity Service Network (Csn): The CSN provides connectivity to the Internet, ASP,

other public networks, and corporate networks. The CSN is owned by the NSP and includes

AAA servers that support authentication for the devices, users, and specific services. The

CSN also provides per user policy management of QoS and security. The CSN is also

responsible for IP address management, support for roaming between different NSPs,

location management between ASNs, and mobility and roaming between ASNs, subscriber

billing and inter operator settlement, inter-CSN tunneling to support roaming between

different NSPs.


GHAZIABD-201206 39

9. WI-FI

Scope:

Wi-Fi is a registered trademark by the Wi-Fi Alliance. The products tested and approved as "Wi-

Fi Certified" are interoperable with each other, even if they are from different manufacturer. It is

Short form for “Wireless-Fidelity” and is meant to generically refer to any type of ‘802.11’

network, whether ‘802.11’b, ‘802.11’a, dual-band, etc.

General description of Wi-Fi Network:

A Wi-Fi network provides the features and benefits of traditional LAN technologies such as

Ethernet and Token Ring without the limitations of wires or cables. It provides the final few

metres of connectivity between a wired network and the mobile user thereby providing mobility,

scalability of networks and the speed of installation.

WIFI is a wireless LAN Technology to deliver wireless broad band speeds up to 54 Mbps to

Laptops, PCs, PDAs , dual mode wifi enabled phones etc.

In a typical Wi-Fi configuration, a transmitter/receiver (transceiver) device, called the Access

Point (AP), connects to the wired network from a fixed location using standard cabling. A

wireless Access Point combines router and bridging functions, it bridges network traffic, usually

from Ethernet to the airwaves, where it routes to computers with wireless adapters. The AP can

reside at any node of the wired network and acts as a gateway for wireless data to be routed onto

the wired network as shown in Figure-1. It supports only 10 to 30 mobile devices per Access

Point (AP) depending on the network traffic. Like a cellular system, the Wi-Fi is capable of

roaming from the AP and re-connecting to the network through another AP. The Access Point

(or the antenna attached to the Access Point) is usually mounted high but may be mounted

essentially anywhere that is practical as long as the desired radio coverage is obtained.


GHAZIABD-201206 40

http://www.webopedia.com/TERM/W/Wi_Fi.html#%23

http://www.webopedia.com/TERM/W/Wi_Fi.html#%23

Figure -1: A typical Wi-Fi Network.

Like a cellular phone system, the wireless LAN is capable of roaming from the AP and re-

connecting to the network through other APs residing at other points on the wired network. This

can allow the wired LAN to be extended to cover a much larger area than the existing coverage

by the use of multiple APs such as in a campus environment as shown in Figure 2.

Figure -2: Extending Wi-Fi coverage with multiple APs.


GHAZIABD-201206 41

An important feature of the wireless LAN is that it can be used independent of a wired network.

It may be used as a stand alone network anywhere to link multiple computers together without

having to build or extend a wired network. Then a peer to peer workgroup can be established for

transfer or access of data. A member of the workgroup may be established as the server or the

network can act in a peer to peer mode as Shown in Figure-3.

Figure-3: Wireless LAN workgroup.

End users access the Wi-Fi network through Wi-Fi adapters, which are implemented as cards in

desktop computers, or integrated within hand-held computers. Wi-Fi wireless LAN adapters

provide an interface between the client Network Operating System (NOS) and the airwaves via

an antenna. The nature of the wireless connection is transparent to the NOS. Wi-Fi deals with

fixed, portable and mobile stations and of course, the physical layers used here are fundamentally

different from wired media.

Wi-Fi Network Configuration:

A Wireless Peer-To-Peer Network: This mode is also known as ADHOC mode. Wi-Fi

networks can be simple or complex. At its most basic, two PCs equipped with wireless adapter

cards can set up an independent network whenever they are within range of one another. This is

called a peer-to-peer network. It requires no administration or pre-configuration. In this case,


GHAZIABD-201206 42

each client would only have access to the resources of the other client and not to a central server

as shown in Figure-4.

Figure-4: A Wi-Fi Peer-To-Peer Network.

Client and Access Point:

This is known as INFRASTUCTURE mode and is normally employed.

However, wireless gateway can be configured to enable peer to peer

communication in this mode as well.

In this mode, one Access Point is connected to the wired network and each client would have

access to server resources as well as to other clients. The specific number client depends on the

number and nature of the transmissions involved. Many real-world applications exist where a

single Access Point services from 15 to 50 client devices as shown in Figure-5.

Figure-5: A Server and Clint Wi-Fi Network.


GHAZIABD-201206 43

Multiple Access Points and Roaming:

Access points can be connected to each other through UTP cable or they can be

connected to each other over radio through wireless bridging. There is an option to

connect access points in a mesh architecture where in event of a fault in an access

point the network heals itself and connectivity is ensured through other access point.

This changeover takes place dynamically.

Access Points have a finite range, of the order of 500 feet indoor and 1000 feet outdoors. In a

very large facility such as a warehouse, or on a college campus, it will probably be necessary to

install more than one Access Point. Access Point positioning is done by a site survey. The goal is

to blanket the coverage area with overlapping coverage cells so that clients might range

throughout the area without ever losing network contact. The ability of clients to move

seamlessly among a cluster of Access Points is called roaming. Access Points hand the client off

from one to another in a way that is invisible to the client, ensuring unbroken connectivity as

shown in Fig-6.

Figure-6: Multiple Access Points and Roaming.

Use of an Extension Point: To solve particular problems of topology, the network designer

some times uses Extension Points (EPs) to augment the network of Access Points (APs).

Extension Points look and function like Access Points, but they are not tethered to the wired

network as are APs. EPs function just as their name implies: they extend the range of the

network by relaying signals from a client to an AP or another EP. EPs may be strung together in

order to pass along messaging from an AP to far-flung clients as shown in Figure-7.


GHAZIABD-201206 44

Figure -7: Wi-Fi network with Extension Point (EP).

The Use of Directional Antennae: One last item of wireless LAN equipment to consider is the

directional antenna. Let’s suppose you had a Wi-Fi network in your building-A and wanted to

extend it to a leased building-B, one mile away. One solution might be to install a directional

antenna on each building, each antenna targeting the other.

The antenna on ‘A’ is connected to your wired network via an Access Point. The antenna on ‘B’

is similarly connected to an Access Point in that building, which enables Wi-Fi network

connectivity in that facility as shown in Figure-8.

Figure-8: A Wi-Fi network using Directional Antennae.


GHAZIABD-201206 45

CONCLUSION

I saw various division of C.T.O. Compound Ajmer Exchange and tried to group as much as I

could, which switched my knowledge and logic. As a student of ECE. I learned Telecom

Networks which is mainly concerned with my focus area.

At last, I would like to say thanks again all staff of the unit who helped me through my

training period.

THANKS!

VIDYANSHU SHANKHADHAR Final Year (ECE)

R.D. ENGINEERING COLLEGE, GHAZIABAD

Bibliography

1. Material provided by Advance Level Training in Tele

Communication (ALTTC) center.

2. www.wikipedia.org


GHAZIABD-201206 46

http://www.wikipedia.org/

3. www.tec.gov.in

4. www.tcoe.in

5. www.tdsat.nic.in

6. www.itu.int

7. www.aptsec.org

8. www.etsi.org

9. www.mtnl.net.in

10.www.tcil-india.com

11.www.itiltd-india.com


GHAZIABD-201206 47

http://www.tcil-india.com/

http://www.mtnl.net.in/

http://www.etsi.org/

http://www.aptsec.org/

http://www.itu.int/

http://www.tdsat.nic.in/

http://www.tcoe.in/

http://www.tec.gov.in/

training report

Documents

preface industrial training

engineering college

number of open wire

number of circuits

industrial ethics

increased number of

multiplexing techniquesthere

open wire alignment