Resource Guide.ppt

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SUMMER INDUSTRIAL TRAINING REPORT

Vivekanand Institute of Technology and Science

SUBMITTED BYPANKAJ YADAV

ROLL.NO 1022331068

RANCH: ELECTRONICS AND ECOMMUNICATION


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Contents

B.S.N.L. An Introduction

DIGITALSWITCHING

MODULATION:

MULTIPLEXING:

POWER PLANT

Microprocessor

.S.D.N (Integrated service digital network)-

Electronic Exchange

GSM

CDMA

Fiber-optic communication

Wi-Fi


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B.S.N.L. AnIntroductionharat Sanchar Nigam Limited (known as BSNL, India

ommunications Corporation Limited) is a state-owned

lecommunication

ompany in India.

SNL is the sixth largest cellular service provider, with over 57.22illion customers as of December 2009 and the largest land line

lephone provider in India.

s headquarters are at Bharat Sanchar Bhawan, Harish Chandra

athur Lane, Janpath, New Delhi. It has the status of Mini Ratna, a

tatus assigned to reputed public sector companies in India.

SNL is India's oldest and largest Communication Service Provider

CSP). Currently has a customer base of 90 million as of June 2008.has footprints throughout India except for the metropolitan cities

f Mumbai and New Delhi which are managed by MTNL.

s on March 31, 2008 BSNL commanded a customer base of 31.55

illion Wireline, 4.58 million CDMA-WLL and 54.21 million GSM

ervices.


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1 B.S.N.L. AnIntroduction

harat Sanchar Nigam Limited (known as BSNL, India Communications Corporatio

mited) is a state-owned telecommunication

SNL is the sixth largest cellular service provider, with over 57.22 million customers as

ecember 2009 and the largest land line telephone provider in India.

headquarters are at Bharat Sanchar Bhawan, Harish Chandra Mathur Lane, Janpath, Ne

elhi. It has the status of Mini Ratna, a status assigned to reputed public sector companie

BSNL is India's oldest and largest Communication Service Provider (CSP). Currently ha

customer base of 90 million as of June 2008. It has footprints throughout India except fo

e metropolitan cities of Mumbai and New Delhi which are managed by MTN

s on March 31, 2008 BSNL commanded a customer base of 31.55 million Wireline, 4.5

llion CDMA-WLL and 54.21 million GSM services.


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DIGITALSWITCHING:

Digital switching has become a synonym for timeivision multiplex. In digital switching system,igital signals are switched in two nodes, timewitching and space switching. Time switchingasically involves rearrangement of channel

equence in the same PCM from whereas spacewitching involves interconnection of samehannels of a different PCM high way. In aractical digital switching both time and spacewitching stage is employed to increase the

raffic handling capacity of the switch at minimumost. Among the various possible combinations

TST structure is most commonly used.Synchronization of various exchange clocks in aigital network is essential to provide requiredervices. Causing a slip due to mismatchetween the clocks will result in multination of

nformation and description of services. Hence,lip has to be controlled using plesiochronous

nd synchronous approaches. D


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MODULATION:

Often the message signal is notsuitable for transmission overhe medium in its original forms.

Therefore, the message signal isocated in a carrier wave, whichs more suited for transmissionover the medium. This process

s called modulation of thecarrier wave. At the receivingend station the message signal

eceived back from the incomingmodulated carrier wave by aprocess is called demodulation

which is inverse of modulation.


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MULTIPLEXING:

Modulation enables multiple messageignals to be simultaneously transmittedover the same medium without interferingeach other. Transmission of multiple

message signals simultaneously over amedium is called multiplexing.Modulation is essentially a process ofelocation of a message signal in a carrier

wave, which is more suitable forransmission for transmission over themedium than the message signal itself.Three types of modulation can occur-

. Amplitude modulation2. Frequency modulation3. Pulse modulation


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POWER PLANT

One of the primary requirements ofany computer system is that servicewill be available to the subscriber atany time. In the vast majority of

exchanges the electrical energyequired for signaling, switching,

speed transmission mains. Theexchange power system is designedo provide continuous anduninterrupted telephone service evenwhen the public electric fails. We can

divide power plant in three majorblocks such as

FLOAT RECTIFIERBATTERY CHARGERSWITCHING CUBICAL


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Microprocessor

A microprocessor is a complexelectronic processor on a singlesilicon chip (Large-scale integrated

circuit). It is capable of performingarithmetic and logical functionsunder the control of program.Functional units of microprocessor-

. Arithmetic and logic unit2. Registers (Temporary memory)3. Timing and control unit

Functions

. FETCH

2. DECODE


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S.D.N (Integrated service digital network)-

Presently, there is a multiplicity of services suchs telephoning, telex, data cable television etc.

hat are provided by separate dedicated networkor each of them. These non-integrated servicesequire separate switching system. Specialubscribers access plants, individual trunketworks and separate operations and

maintenance staff. These services are costly tohe subscriber as well as to department. InS.D.N, these services are provided by one

ntegrated network, which can be accessed by

ifferent customer premises equipment.n I.S.D.N, subscriber loop from the localxchange will be terminated at the networkerminal (N.T). From N.T the signal will beistributed to the information sockets. These

nformation sockets will be distributed in theremises just like power sockets are distributedor providing on the information sockets, differenterminals for voice and nonvoice services can beonnected.


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Electronic Exchange

These are entirely computerized and

electronic devices, which work on storeprogramme control. Electronic logicomponent can do ten thousand times

operation during signal in the comparison

of electromechanical exchange.

n an electronic exchange a single controlevice simultaneously process a number

of calls on time-sharing basis. Suchentralization is more economical, but it isisadvantageous in making switchingystem more vulnerable to system failure.

This, however, can be overcome atandby control devices.These electronic exchanges havepowerful processing unit. Part of control

equipment capacity utilize for functionother than for processing.


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GSM (Global System for MobileCommunications, originally Groupe Spcial

Mobi le), is a standard set developed by the

European Telecommunications Standardsnstitute (ETSI) to describe protocols for secondeneration (2G) digital cellular networks used by

mobile phones. It became the de facto global

tandard for mobile communications with over0% market share.

The GSM standard was developed as aeplacement for first generation (1G) analogellular networks, and originally described a

igital, circuit-switched network optimized forfulluplex voice telephony. This was expanded overme to include data communications, first byircuit-switched transport, then packet dataransport via GPRS (General Packet Radio

Services) and EDGE (Enhanced Data rates forGSM Evolution or EGPRS).

urther improvements were made when theGPP developed third generation (3G) UMTS

tandards followed by fourth generation (4G) LTEAdvanced standards.

GSM
http://en.wikipedia.org/wiki/LTE_Advancedhttp://en.wikipedia.org/wiki/European_Telecommunications_Standards_Institutehttp://en.wikipedia.org/wiki/European_Telecommunications_Standards_Institutehttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/Cellular_networkhttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Comparison_of_mobile_phone_standardshttp://en.wikipedia.org/wiki/Comparison_of_mobile_phone_standardshttp://en.wikipedia.org/wiki/1Ghttp://en.wikipedia.org/wiki/Duplex_%28telecommunications%29http://en.wikipedia.org/wiki/Duplex_%28telecommunications%29http://en.wikipedia.org/wiki/Telephonyhttp://en.wikipedia.org/wiki/Network_packethttp://en.wikipedia.org/wiki/GPRShttp://en.wikipedia.org/wiki/EDGEhttp://en.wikipedia.org/wiki/3GPPhttp://en.wikipedia.org/wiki/3Ghttp://en.wikipedia.org/wiki/UMTShttp://en.wikipedia.org/wiki/4Ghttp://en.wikipedia.org/wiki/LTE_Advancedhttp://en.wikipedia.org/wiki/LTE_Advancedhttp://en.wikipedia.org/wiki/LTE_Advancedhttp://en.wikipedia.org/wiki/LTE_Advancedhttp://en.wikipedia.org/wiki/4Ghttp://en.wikipedia.org/wiki/UMTShttp://en.wikipedia.org/wiki/3Ghttp://en.wikipedia.org/wiki/3GPPhttp://en.wikipedia.org/wiki/EDGEhttp://en.wikipedia.org/wiki/GPRShttp://en.wikipedia.org/wiki/Network_packethttp://en.wikipedia.org/wiki/Telephonyhttp://en.wikipedia.org/wiki/Duplex_%28telecommunications%29http://en.wikipedia.org/wiki/Duplex_%28telecommunications%29http://en.wikipedia.org/wiki/1Ghttp://en.wikipedia.org/wiki/Comparison_of_mobile_phone_standardshttp://en.wikipedia.org/wiki/Comparison_of_mobile_phone_standardshttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Cellular_networkhttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/European_Telecommunications_Standards_Institutehttp://en.wikipedia.org/wiki/European_Telecommunications_Standards_Institute


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n 1981, work began to develop a European standard forigital cellular voice telephony when the European

onference of Postal and Telecommunicationsdministrations (CEPT) created the Groupe Spcial

Mobile committee and later provided a permanentechnical support group based in Paris. Five years later,n 1987, 15 representatives from 13 European countriesgned a memorandum of understanding in Copenhagen

o develop and deploy a common cellular telephoneystem across Europe, and EU rules were passed to

make GSM a mandatory standard.The decision toevelop a continental standard eventually resulted in anified, open, standard-based network which was larger

han that in the United States In 1989, the Groupepcial Mobile committee was transferred from CEPT tohe European Telecommunications Standards InstituteETSI).n 1987 Europe produced the very first agreed GSMechnical Specification in February). Ministers from the

our big EU countries cemented their political support forGSM with the Bonn Declaration on Global Information

etworks in May and the GSM MoU was tabled forgnature in September. The MoU drew-in mobileperators from across Europe to pledge to invest in new

GSM networks to an ambitious common date. It gotGSM up and running fast.

History
http://en.wikipedia.org/wiki/European_Conference_of_Postal_and_Telecommunications_Administrationshttp://en.wikipedia.org/wiki/European_Conference_of_Postal_and_Telecommunications_Administrationshttp://en.wikipedia.org/wiki/European_Conference_of_Postal_and_Telecommunications_Administrationshttp://en.wikipedia.org/wiki/Parishttp://en.wikipedia.org/wiki/Memorandum_of_understandinghttp://en.wikipedia.org/wiki/Copenhagenhttp://en.wikipedia.org/wiki/European_Telecommunications_Standards_Institutehttp://en.wikipedia.org/wiki/European_Telecommunications_Standards_Institutehttp://en.wikipedia.org/wiki/Copenhagenhttp://en.wikipedia.org/wiki/Memorandum_of_understandinghttp://en.wikipedia.org/wiki/Parishttp://en.wikipedia.org/wiki/European_Conference_of_Postal_and_Telecommunications_Administrationshttp://en.wikipedia.org/wiki/European_Conference_of_Postal_and_Telecommunications_Administrationshttp://en.wikipedia.org/wiki/European_Conference_of_Postal_and_Telecommunications_Administrations


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GSM is a cellular network, which meanshat cell phones connect to it by searching

or cells in the immediate vicinity. There areve different cell sizes in a GSM networkmacro, micro, pico, femto, and umbrellaells. The coverage area of each cell variesccording to the implementation

nvironment. Macro cells can be regardeds cells where the base stationantenna is

nstalled on a mast or a building aboveverage rooftop level. Micro cells are cells

whose antenna height is under average

ooftop level; they are typically used inrban areas. Picocells are small cells

whose coverage diameter is a few dozenmetres; they are mainly used indoors.

emtocells are cells designed for use inesidential or small business environmentsnd connect to the service providers

etwork via a broadband internetonnection. Umbrella cells are used to

over shadowed regions of smaller cells

Base Station subsystem
http://en.wikipedia.org/wiki/Cellular_networkhttp://en.wikipedia.org/wiki/Cell_phonehttp://en.wikipedia.org/wiki/Macrocellhttp://en.wikipedia.org/wiki/Microcellhttp://en.wikipedia.org/wiki/Picocellhttp://en.wikipedia.org/wiki/Femtocellhttp://en.wikipedia.org/w/index.php?title=Umbrella_cells&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Umbrella_cells&action=edit&redlink=1http://en.wikipedia.org/wiki/Base_stationhttp://en.wikipedia.org/wiki/Antenna_%28electronics%29http://en.wikipedia.org/wiki/Antenna_%28electronics%29http://en.wikipedia.org/wiki/Base_stationhttp://en.wikipedia.org/w/index.php?title=Umbrella_cells&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Umbrella_cells&action=edit&redlink=1http://en.wikipedia.org/wiki/Femtocellhttp://en.wikipedia.org/wiki/Picocellhttp://en.wikipedia.org/wiki/Microcellhttp://en.wikipedia.org/wiki/Macrocellhttp://en.wikipedia.org/wiki/Cell_phonehttp://en.wikipedia.org/wiki/Cellular_network


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GSM networks operate in a number of different carrierequency ranges (separated into GSM frequency ranges

or 2G and UMTS frequency bands for 3G), with most 2GGSM networks operating in the 900 MHz or 1800 MHzands. Where these bands were already allocated, the50 MHz and 1900 MHz bands were used instead (for

xample in Canada and the United States). In rare caseshe 400 and 450 MHz frequency bands are assigned inome countries because they were previously used forrst-generation systems.

Most 3G networks in Europe operate in the 2100 MHzequency band. For more information on worldwide GSM

equency usage, see GSM frequency bands.Regardless of the frequency selected by an operator, it isivided into timeslots for individual phones. This allowsight full-rate or sixteen half-rate speech channels peradio frequency. These eight radio timeslots (orburst

eriods) are grouped into a TDMA frame. Half-ratehannels use alternate frames in the same timeslot. Thehannel data rate for all 8 channels is 270.833 kbit/s, andhe frame duration is 4.615 ms.he transmission power in the handset is limited to a

maximum of 2 watts in GSM 850/900 and 1 watt in GSM

800/1900.

GSM carrier frequencies
http://en.wikipedia.org/wiki/GSM_frequency_rangeshttp://en.wikipedia.org/wiki/UMTS_frequency_bandshttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/3Ghttp://en.wikipedia.org/wiki/GSM_frequency_bandshttp://en.wikipedia.org/wiki/Time_division_multiplexinghttp://en.wikipedia.org/wiki/Radio_frequencyhttp://en.wikipedia.org/wiki/Burst_transmissionhttp://en.wikipedia.org/wiki/Time_division_multiple_accesshttp://en.wikipedia.org/wiki/Time_division_multiple_accesshttp://en.wikipedia.org/wiki/Burst_transmissionhttp://en.wikipedia.org/wiki/Radio_frequencyhttp://en.wikipedia.org/wiki/Time_division_multiplexinghttp://en.wikipedia.org/wiki/GSM_frequency_bandshttp://en.wikipedia.org/wiki/3Ghttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/UMTS_frequency_bandshttp://en.wikipedia.org/wiki/GSM_frequency_ranges


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GSM was designed with a moderate level

of service security. The system wasesigned to authenticate the subscribersing a pre-shared key and challenge-esponse. Communications between the

ubscriber and the base station can beencrypted. The development ofUMTSntroduces an optional UniversalSubscriber Identity Module (USIM), that

ses a longer authentication key to givereater security, as well as mutually

authenticating the network and the user,whereas GSM only authenticates the user

o the network (and not vice versa). Theecurity model therefore offersonfidentiality and authentication, butmited authorization capabilities, and no

on-repudiation.

GSM service security
http://en.wikipedia.org/wiki/Pre-shared_keyhttp://en.wikipedia.org/wiki/Challenge-response_authenticationhttp://en.wikipedia.org/wiki/Challenge-response_authenticationhttp://en.wikipedia.org/wiki/Universal_Mobile_Telecommunications_Systemhttp://en.wikipedia.org/wiki/Universal_Subscriber_Identity_Modulehttp://en.wikipedia.org/wiki/Universal_Subscriber_Identity_Modulehttp://en.wikipedia.org/wiki/Non-repudiationhttp://en.wikipedia.org/wiki/Non-repudiationhttp://en.wikipedia.org/wiki/Non-repudiationhttp://en.wikipedia.org/wiki/Non-repudiationhttp://en.wikipedia.org/wiki/Universal_Subscriber_Identity_Modulehttp://en.wikipedia.org/wiki/Universal_Subscriber_Identity_Modulehttp://en.wikipedia.org/wiki/Universal_Mobile_Telecommunications_Systemhttp://en.wikipedia.org/wiki/Challenge-response_authenticationhttp://en.wikipedia.org/wiki/Challenge-response_authenticationhttp://en.wikipedia.org/wiki/Challenge-response_authenticationhttp://en.wikipedia.org/wiki/Pre-shared_keyhttp://en.wikipedia.org/wiki/Pre-shared_keyhttp://en.wikipedia.org/wiki/Pre-shared_key


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The network is structured into a

number of discrete sections:Base Station Subsystem thebase stations and their controllers

Network and SwitchingSubsystem the part of thenetwork most similar to a fixednetwork, sometimes just called the

core network"GPRS Core Network theoptional part which allows packet-

based Internet connectionsOperations support system (OSS) network maintenance

Network structure
http://en.wikipedia.org/wiki/Base_Station_Subsystemhttp://en.wikipedia.org/wiki/Network_and_Switching_Subsystemhttp://en.wikipedia.org/wiki/Network_and_Switching_Subsystemhttp://en.wikipedia.org/wiki/GPRS_Core_Networkhttp://en.wikipedia.org/wiki/Operations_support_systemhttp://en.wikipedia.org/wiki/Operations_support_systemhttp://en.wikipedia.org/wiki/GPRS_Core_Networkhttp://en.wikipedia.org/wiki/Network_and_Switching_Subsystemhttp://en.wikipedia.org/wiki/Network_and_Switching_Subsystemhttp://en.wikipedia.org/wiki/Base_Station_Subsystem


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Code division multiple access (CDMA) is ahannel access method used by various radioommunication technologies.

CDMA is an example ofmultiple access, whichs where several transmitters can sendnformation simultaneously over a singleommunication channel. This allows severalsers to share a band of frequencies (seeandwidth). To permit this to be achieved

without undue interference between the usersCDMA employs spread-spectrum technologynd a special coding scheme (where eachransmitter is assigned a code).

CDMA is used as the access method in many

mobile phone standards such as cdmaOne,CDMA2000 (the 3G evolution of cdmaOne),nd WCDMA (the 3G standard used by GSMarriers), which are often referred to as simply

CDMA.

Code division multiple access
http://en.wikipedia.org/wiki/Channel_access_methodhttp://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Multiple_accesshttp://en.wikipedia.org/wiki/Bandwidth_%28signal_processing%29http://en.wikipedia.org/wiki/Spread-spectrumhttp://en.wikipedia.org/wiki/List_of_mobile_phone_standardshttp://en.wikipedia.org/wiki/IS-95http://en.wikipedia.org/wiki/CDMA2000http://en.wikipedia.org/wiki/3Ghttp://en.wikipedia.org/wiki/WCDMAhttp://en.wikipedia.org/wiki/GSMhttp://en.wikipedia.org/wiki/GSMhttp://en.wikipedia.org/wiki/WCDMAhttp://en.wikipedia.org/wiki/3Ghttp://en.wikipedia.org/wiki/CDMA2000http://en.wikipedia.org/wiki/IS-95http://en.wikipedia.org/wiki/List_of_mobile_phone_standardshttp://en.wikipedia.org/wiki/Spread-spectrumhttp://en.wikipedia.org/wiki/Spread-spectrumhttp://en.wikipedia.org/wiki/Spread-spectrumhttp://en.wikipedia.org/wiki/Bandwidth_%28signal_processing%29http://en.wikipedia.org/wiki/Multiple_accesshttp://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Channel_access_method


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he technology of code division multiple accesshannels has long been known. In the USSR, the first

work devoted to this subject was published in 1935 byrofessorDmitriy V. Ageev.[1] It was shown that throughhe use of linear methods, there are three types of signaleparation: frequency, time and compensatory. Theechnology of CDMA was used in 1957, when the young

military radio engineerLeonid Kupriyanovich in Moscow,

made an experimental model of a wearable automaticmobile phone, called LK-1 by him, with a base station.K-1 has a weight of 3 kg, 2030 km operating distance,nd 2030 hours of battery life.[2][3] The base station, asescribed by the author, could serve several customers.n 1958, Kupriyanovich made the new experimental

pocket" model of mobile phone. This phone weighed.5 kg. To serve more customers, Kupriyanovichroposed the device, named by him as correllator.[4][5] In958, the USSR also started the development of theAltai" national civil mobile phone service for cars, based

n the Soviet MRT-1327 standard. The phone systemweighed 11 kg and was approximately 3 cubic meters inze[dubiousdiscuss]. It was placed in the trunk of theehicles of high-ranking officials and used a standardandset in the passenger compartment. The mainevelopers of the Altai system were VNIIS (Voronezh

cience Research Institute of Communications) andGSPI (State Specialized Project Institute

History
http://en.wikipedia.org/wiki/USSRhttp://ru.wikipedia.org/wiki/%D0%90%D0%B3%D0%B5%D0%B5%D0%B2,_%D0%94%D0%BC%D0%B8%D1%82%D1%80%D0%B8%D0%B9_%D0%92%D0%B0%D1%81%D0%B8%D0%BB%D1%8C%D0%B5%D0%B2%D0%B8%D1%87http://en.wikipedia.org/wiki/Code_division_multiple_accesshttp://en.wikipedia.org/wiki/Leonid_Kupriyanovichhttp://en.wikipedia.org/wiki/Code_division_multiple_accesshttp://en.wikipedia.org/wiki/Code_division_multiple_accesshttp://en.wikipedia.org/wiki/Altai_%28mobile_telephone_system%29http://en.wikipedia.org/wiki/Wikipedia:Disputed_statementhttp://en.wikipedia.org/wiki/Talk:Code_division_multiple_accesshttp://en.wikipedia.org/wiki/Talk:Code_division_multiple_accesshttp://en.wikipedia.org/wiki/Wikipedia:Disputed_statementhttp://en.wikipedia.org/wiki/Altai_%28mobile_telephone_system%29http://en.wikipedia.org/wiki/Code_division_multiple_accesshttp://en.wikipedia.org/wiki/Code_division_multiple_accesshttp://en.wikipedia.org/wiki/Code_division_multiple_accesshttp://en.wikipedia.org/wiki/Code_division_multiple_accesshttp://en.wikipedia.org/wiki/Leonid_Kupriyanovichhttp://en.wikipedia.org/wiki/Code_division_multiple_accesshttp://ru.wikipedia.org/wiki/%D0%90%D0%B3%D0%B5%D0%B5%D0%B2,_%D0%94%D0%BC%D0%B8%D1%82%D1%80%D0%B8%D0%B9_%D0%92%D0%B0%D1%81%D0%B8%D0%BB%D1%8C%D0%B5%D0%B2%D0%B8%D1%87http://en.wikipedia.org/wiki/USSR


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CDMA is a spread spectrum multiple access[6]

echnique. A spread spectrum technique spreadshe bandwidth of the data uniformly for the sameransmitted power. A spreading code is a pseudoandom code that has a narrow ambiguityunction, unlike other narrow pulse codes. In

CDMA a locally generated code runs at a muchigher rate than the data to be transmitted. Dataor transmission is combined via bitwise XORexclusive OR) with the faster code. The figurehows how a spread spectrum signal is

enerated. The data signal with pulse duration ofsymbol period) is XORed with the code signal

with pulse duration of (chip period). (Note:andwidth is proportional to where = bit time)

Therefore, the bandwidth of the data signal isnd the bandwidth of the spread spectrum signa

s . Since is much smaller than , theandwidth of the spread spectrum signal is much

arger than the bandwidth of the original signal.

The ratio is called the spreading factor

Steps in CDMA Modulation
http://en.wikipedia.org/wiki/Code_division_multiple_accesshttp://en.wikipedia.org/wiki/Ambiguity_functionhttp://en.wikipedia.org/wiki/Ambiguity_functionhttp://en.wikipedia.org/wiki/XORhttp://en.wikipedia.org/wiki/Bandwidth_%28signal_processing%29http://en.wikipedia.org/wiki/Bandwidth_%28signal_processing%29http://en.wikipedia.org/wiki/XORhttp://en.wikipedia.org/wiki/Ambiguity_functionhttp://en.wikipedia.org/wiki/Ambiguity_functionhttp://en.wikipedia.org/wiki/Code_division_multiple_access


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Synchronous CDMA exploits mathematicalroperties oforthogonality between vectors

epresenting the data strings. For example,inary string 1011 is represented by the vector1, 0, 1, 1). Vectors can be multiplied by takingheirdot product, by summing the products ofheir respective components (for example, if u =

a, b) and v = (c, d), then their dot product uv =c + bd). If the dot product is zero, the twoectors are said to be orthogonalto each other.

Some properties of the dot product aidnderstanding of how W-CDMA works:

Code division multiplexing (Synchronous

CDMA)
http://en.wikipedia.org/wiki/Orthogonalityhttp://en.wikipedia.org/wiki/Coordinate_vectorhttp://en.wikipedia.org/wiki/Dot_producthttp://en.wikipedia.org/wiki/W-CDMAhttp://en.wikipedia.org/wiki/W-CDMAhttp://en.wikipedia.org/wiki/W-CDMAhttp://en.wikipedia.org/wiki/W-CDMAhttp://en.wikipedia.org/wiki/Dot_producthttp://en.wikipedia.org/wiki/Coordinate_vectorhttp://en.wikipedia.org/wiki/Orthogonality


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When mobile-to-base links cannot be preciselyoordinated, particularly due to the mobility ofhe handsets, a different approach is required.

Since it is not mathematically possible toreate signature sequences that are bothrthogonal for arbitrarily random starting pointsnd which make full use of the code space,nique "pseudo-random" or "pseudo-noise"PN) sequences are used in asynchronous

CDMA systems. A PN code is a binaryequence that appears random but can beeproduced in a deterministic manner by

ntended receivers. These PN codes are usedo encode and decode a user's signal in

Asynchronous CDMA in the same manner ashe orthogonal codes in synchronous CDMAshown in the example above). These PN

equences are statistically uncorrelated, andhe sum of a large number of PN sequencesesults in multiple access interference (MAI)hat is approximated by a Gaussian noiserocess (following the central limit theorem intatistics.

Asynchronous CDMA
http://en.wikipedia.org/wiki/Central_limit_theoremhttp://en.wikipedia.org/wiki/Central_limit_theorem


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iber-optic communication is a method of

ransmitting information from one place tonother by sending pulses oflight through anptical fiber. The light forms an electromagneticarrier wave that is modulated to carrynformation. First developed in the 1970s, fiber-

ptic communication systems haveevolutionized the telecommunications industrynd have played a major role in the advent of thenformation Age. Because of its advantages overlectrical transmission, optical fibers have largelyeplaced copper wire communications in coreetworks in the developed world.

The process of communicating using fiber-opticsnvolves the following basic steps: Creating the

ptical signal involving the use of a transmitter,elaying the signal along the fiber, ensuring thathe signal does not become too distorted or

weak, receiving the optical signal, and convertinginto an electrical signal.

Fiber-optic communication
http://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Electromagnetic_radiationhttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Communication_systemhttp://en.wikipedia.org/wiki/Telecommunicationshttp://en.wikipedia.org/wiki/Information_Agehttp://en.wikipedia.org/wiki/Fiber-optic_communicationhttp://en.wikipedia.org/wiki/Fiber-optic_communicationhttp://en.wikipedia.org/wiki/Core_networkhttp://en.wikipedia.org/wiki/Core_networkhttp://en.wikipedia.org/wiki/Developed_worldhttp://en.wikipedia.org/wiki/Electrical_signalhttp://en.wikipedia.org/wiki/Electrical_signalhttp://en.wikipedia.org/wiki/Developed_worldhttp://en.wikipedia.org/wiki/Core_networkhttp://en.wikipedia.org/wiki/Core_networkhttp://en.wikipedia.org/wiki/Fiber-optic_communicationhttp://en.wikipedia.org/wiki/Fiber-optic_communicationhttp://en.wikipedia.org/wiki/Information_Agehttp://en.wikipedia.org/wiki/Telecommunicationshttp://en.wikipedia.org/wiki/Communication_systemhttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wikipedia.org/wiki/Electromagnetic_radiationhttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Light


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n 1880Alexander Graham Bell and hisassistant Charles Sumner Tainterreated a very early precursor to fiber-

optic communications, the Photophone,

at Bell's newly established VoltaLaboratory in Washington, D.C. Bellonsidered it his most important

nvention. The device allowed for the

ransmission of sound on a beam ofght. On June 3, 1880, Bell conductedhe world's first wireless telephoneransmission between two buildings,

ome 213 meters apart.[1][2]

Due to itsse of an atmospheric transmissionmedium, the Photophone would notprove practical until advances in laser

and optical fiber technologies permittedhe secure transport of light.

History
http://en.wikipedia.org/wiki/Alexander_Graham_Bellhttp://en.wikipedia.org/wiki/Charles_Sumner_Tainterhttp://en.wikipedia.org/wiki/Photophonehttp://en.wikipedia.org/wiki/Volta_Laboratory_and_Bureauhttp://en.wikipedia.org/wiki/Volta_Laboratory_and_Bureauhttp://en.wikipedia.org/wiki/Washington,_D.C.http://en.wikipedia.org/wiki/Transmission_%28telecommunications%29http://en.wikipedia.org/wiki/Telephonehttp://en.wikipedia.org/wiki/Fiber-optic_communicationhttp://en.wikipedia.org/wiki/Fiber-optic_communicationhttp://en.wikipedia.org/wiki/Fiber-optic_communicationhttp://en.wikipedia.org/wiki/Telephonehttp://en.wikipedia.org/wiki/Transmission_%28telecommunications%29http://en.wikipedia.org/wiki/Washington,_D.C.http://en.wikipedia.org/wiki/Volta_Laboratory_and_Bureauhttp://en.wikipedia.org/wiki/Volta_Laboratory_and_Bureauhttp://en.wikipedia.org/wiki/Photophonehttp://en.wikipedia.org/wiki/Charles_Sumner_Tainterhttp://en.wikipedia.org/wiki/Alexander_Graham_Bell


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Modern fiber-optic communicationystems generally include an opticalransmitter to convert an electricalignal into an optical signal to send intohe optical fiber, a cable containingbundles of multiple optical fibers that isouted through underground conduits

and buildings, multiple kinds ofamplifiers, and an optical receiver toecover the signal as an electricalignal. The information transmitted isypically digital information generated by

omputers, telephone systems, andable television companies.

Technology
http://en.wikipedia.org/wiki/Optical_fiber_cablehttp://en.wikipedia.org/wiki/Digital_communicationshttp://en.wikipedia.org/wiki/Digital_telephonyhttp://en.wikipedia.org/wiki/Cable_televisionhttp://en.wikipedia.org/wiki/Cable_televisionhttp://en.wikipedia.org/wiki/Digital_telephonyhttp://en.wikipedia.org/wiki/Digital_communicationshttp://en.wikipedia.org/wiki/Optical_fiber_cable


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Optical fiber can be used as a medium forelecommunication and computer networking because it flexible and can be bundled as cables. It is especiallydvantageous for long-distance communications,ecause light propagates through the fiber with littlettenuation compared to electrical cables. This allows

ong distances to be spanned with few repeaters.he per-channel light signals propagating in the fiber

ave been modulated at rates as high as 111 gigabitser second (Gbit/s) by NTT,[ although 10 or 40 Gbit/s isypical in deployed systems.[ In June 2013, researchersemonstrated transmission of 400 Gbit/s over a singlehannel using 4-mode orbital angular momentum modeivision multiplexing.[

ach fiber can carry many independent channels, eachsing a different wavelength of light (wavelength-division

multiplexing (WDM)). The net data rate (data ratewithout overhead bytes) per fiber is the per-channel dataate reduced by the FEC overhead, multiplied by the

umber of channels (usually up to eighty in commercialense WDM systems as of 2008). As of 2011 the recordor bandwidth on a single core was 101 Tbit/sec (370hannels at 273 Gbit/sec each) The record for a multi-ore fibre as of January 2013 was 1.05 petabits perecond. In 2009, Bell Labs broke the 100 (Petabit per

econd)kilometre barrier (15.5 Tbit/s over a single000 km fiber).[

Optical fiber communication
http://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Optical_communications_repeaterhttp://en.wikipedia.org/wiki/Gigabit_per_secondhttp://en.wikipedia.org/wiki/Gigabit_per_secondhttp://en.wikipedia.org/wiki/Nippon_Telegraph_and_Telephonehttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Orbital_angular_momentum_of_lighthttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Wavelength-division_multiplexinghttp://en.wikipedia.org/wiki/Wavelength-division_multiplexinghttp://en.wikipedia.org/wiki/Dense_WDMhttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Dense_WDMhttp://en.wikipedia.org/wiki/Wavelength-division_multiplexinghttp://en.wikipedia.org/wiki/Wavelength-division_multiplexinghttp://en.wikipedia.org/wiki/Wavelength-division_multiplexinghttp://en.wikipedia.org/wiki/Wavelength-division_multiplexinghttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Orbital_angular_momentum_of_lighthttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Nippon_Telegraph_and_Telephonehttp://en.wikipedia.org/wiki/Gigabit_per_secondhttp://en.wikipedia.org/wiki/Gigabit_per_secondhttp://en.wikipedia.org/wiki/Optical_communications_repeaterhttp://en.wikipedia.org/wiki/Computer_network


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An optical fiber is a cylindrical

dielectric waveguide(nonconducting waveguide) thattransmits light along its axis, bythe process oftotal internal

reflection. The fiber consists of acore surrounded by a claddinglayer, both of which are made of

dielectric materials. To confine theoptical signal in the core, therefractive index of the core mustbe greater than that of the

cladding. The boundary betweenthe core and cladding may eitherbe abrupt, in step-index fiber, or

gradual, in graded-index fiber.

Principle of operation
http://en.wikipedia.org/wiki/Dielectric_waveguidehttp://en.wikipedia.org/wiki/Insulator_%28electrical%29http://en.wikipedia.org/wiki/Total_internal_reflectionhttp://en.wikipedia.org/wiki/Total_internal_reflectionhttp://en.wikipedia.org/wiki/Cladding_%28fiber_optics%29http://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Refractive_indexhttp://en.wikipedia.org/wiki/Step-index_profilehttp://en.wikipedia.org/wiki/Graded-index_fiberhttp://en.wikipedia.org/wiki/Graded-index_fiberhttp://en.wikipedia.org/wiki/Graded-index_fiberhttp://en.wikipedia.org/wiki/Graded-index_fiberhttp://en.wikipedia.org/wiki/Step-index_profilehttp://en.wikipedia.org/wiki/Step-index_profilehttp://en.wikipedia.org/wiki/Step-index_profilehttp://en.wikipedia.org/wiki/Refractive_indexhttp://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Cladding_%28fiber_optics%29http://en.wikipedia.org/wiki/Total_internal_reflectionhttp://en.wikipedia.org/wiki/Total_internal_reflectionhttp://en.wikipedia.org/wiki/Insulator_%28electrical%29http://en.wikipedia.org/wiki/Dielectric_waveguide


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iber with large core diameter (greater than0 micrometers) may be analyzed by geometricaptics. Such fiber is called multi-mode fiber, fromhe electromagnetic analysis (see below). In atep-index multi-mode fiber, rays of light are

uided along the fiber core by total internaleflection. Rays that meet the core-claddingoundary at a high angle (measured relative to ane normal to the boundary), greater than theritical angle for this boundary, are completelyeflected. The critical angle (minimum angle forotal internal reflection) is determined by theifference in index of refraction between the corend cladding materials. Rays that meet the

oundary at a low angle are refracted from theore into the cladding, and do not convey lightnd hence information along the fiber. The criticangle determines the acceptance angle of theber, often reported as a numerical aperture.

Multi-mode fiber
http://en.wikipedia.org/wiki/Geometrical_opticshttp://en.wikipedia.org/wiki/Geometrical_opticshttp://en.wikipedia.org/wiki/Ray_%28optics%29http://en.wikipedia.org/wiki/Surface_normalhttp://en.wikipedia.org/wiki/Critical_angle_%28optics%29http://en.wikipedia.org/wiki/Core_%28optical_fiber%29http://en.wikipedia.org/wiki/Guided_rayhttp://en.wikipedia.org/wiki/Numerical_aperturehttp://en.wikipedia.org/wiki/Numerical_aperturehttp://en.wikipedia.org/wiki/Guided_rayhttp://en.wikipedia.org/wiki/Core_%28optical_fiber%29http://en.wikipedia.org/wiki/Critical_angle_%28optics%29http://en.wikipedia.org/wiki/Surface_normalhttp://en.wikipedia.org/wiki/Ray_%28optics%29http://en.wikipedia.org/wiki/Geometrical_opticshttp://en.wikipedia.org/wiki/Geometrical_optics


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iber with a core diameter less than about tenmes the wavelength of the propagating lightannot be modeled using geometric optics.nstead, it must be analyzed as anlectromagnetic structure, by solution of

Maxwell's equations as reduced to thelectromagnetic wave equation. The

lectromagnetic analysis may also be requiredo understand behaviors such as speckle thatccur when coherent light propagates in multi-

mode fiber. As an optical waveguide, the fiberupports one or more confined transverse

modes by which light can propagate along theber. Fiber supporting only one mode is calledingle-mode ormono-mode fiber. The behaviorf larger-core multi-mode fiber can also be

modeled using the wave equation, which showshat such fiber supports more than one mode ofropagation (hence the name). The results ofuch modeling of multi-mode fiberpproximately agree with the predictions of

eometric optics, if the fiber core is largenough to support more than a few modes.

Single-mode fiber
http://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Electromagnetismhttp://en.wikipedia.org/wiki/Maxwell%27s_equationshttp://en.wikipedia.org/wiki/Electromagnetic_wave_equationhttp://en.wikipedia.org/wiki/Coherence_%28physics%29http://en.wikipedia.org/wiki/Transverse_modehttp://en.wikipedia.org/wiki/Transverse_modehttp://en.wikipedia.org/wiki/Transverse_modehttp://en.wikipedia.org/wiki/Transverse_modehttp://en.wikipedia.org/wiki/Coherence_%28physics%29http://en.wikipedia.org/wiki/Electromagnetic_wave_equationhttp://en.wikipedia.org/wiki/Maxwell%27s_equationshttp://en.wikipedia.org/wiki/Electromagnetismhttp://en.wikipedia.org/wiki/Wavelength


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Wi-Fi, also spelled Wi-Fi orWi-Fi, is a

popular technology that allows anelectronic device to exchange data oronnect to the internet wirelesslysing radio waves. The Wi-Fi Alliance

efines Wi-Fi as any "wireless localarea network (WLAN) products thatare based on the Institute of Electricaland Electronics Engineers' (IEEE)

tandards".[1]

However, since mostmodern WLANs are based on thesetandards, the term "Wi-Fi" is used ineneral English as a synonym for

WLAN". Only Wi-Fi products thatomplete Wi-Fi Alliancenteroperability certification testinguccessfully may use the "Wi-Fi

CERTIFIED" trademark.

Wi-Fi
http://en.wikipedia.org/wiki/Wireless_networkhttp://en.wikipedia.org/wiki/Radio_waveshttp://en.wikipedia.org/wiki/Wi-Fi_Alliancehttp://en.wikipedia.org/wiki/Wireless_LANhttp://en.wikipedia.org/wiki/Wireless_LANhttp://en.wikipedia.org/wiki/Institute_of_Electrical_and_Electronics_Engineershttp://en.wikipedia.org/wiki/Institute_of_Electrical_and_Electronics_Engineershttp://en.wikipedia.org/wiki/802.11http://en.wikipedia.org/wiki/Wi-Fihttp://en.wikipedia.org/wiki/Interoperabilityhttp://en.wikipedia.org/wiki/Interoperabilityhttp://en.wikipedia.org/wiki/Wi-Fihttp://en.wikipedia.org/wiki/802.11http://en.wikipedia.org/wiki/802.11http://en.wikipedia.org/wiki/Institute_of_Electrical_and_Electronics_Engineershttp://en.wikipedia.org/wiki/Institute_of_Electrical_and_Electronics_Engineershttp://en.wikipedia.org/wiki/Wireless_LANhttp://en.wikipedia.org/wiki/Wireless_LANhttp://en.wikipedia.org/wiki/Wi-Fi_Alliancehttp://en.wikipedia.org/wiki/Wi-Fi_Alliancehttp://en.wikipedia.org/wiki/Wi-Fi_Alliancehttp://en.wikipedia.org/wiki/Radio_waveshttp://en.wikipedia.org/wiki/Wireless_network


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802.11 technology has its origins in a 1985 ruling by theUS Federal Communications Commission that releasedthe ISM band for unlicensed use. In 1991, NCRCorporation withAT&T Corporation invented theprecursor to intended for use in cashier systems. Thefirst wireless products were under the name WaveLAN.A large number of patents by many companies are usedin 802.11 standard.Vic Hayes has been called the "fatheof Wi-Fi" by some, due to his involvement in negotiatingthe initial standards within the IEEE while chairing theworkgroup.[

A key patent used in Wi-Fi was developed by theAustralian radioastronomerJohn O'Sullivan as a by-product in a CSIRO research project, "a failedexperiment to detect exploding mini black holes the sizeof an atomic particle In 1992 and 1996,Australianorganization CSIRO obtained patents for a method later

used in Wi-Fi to "unsmear" the signal.In 1999, the Wi-Fi Alliance was formed as a tradeassociation to hold the Wi-Fi trademark under whichmost products are sold

History
http://en.wikipedia.org/wiki/ISM_bandhttp://en.wikipedia.org/wiki/NCR_Corporationhttp://en.wikipedia.org/wiki/NCR_Corporationhttp://en.wikipedia.org/wiki/AT%26T_Corporationhttp://en.wikipedia.org/wiki/WaveLANhttp://en.wikipedia.org/wiki/Vic_Hayeshttp://en.wikipedia.org/wiki/Institute_of_Electrical_and_Electronics_Engineershttp://en.wikipedia.org/wiki/Wi-Fihttp://en.wikipedia.org/wiki/John_O%27Sullivan_%28engineer%29http://en.wikipedia.org/wiki/CSIROhttp://en.wikipedia.org/wiki/Wi-Fihttp://en.wikipedia.org/wiki/Australianhttp://en.wikipedia.org/wiki/Wi-Fi_Alliancehttp://en.wikipedia.org/wiki/Wi-Fi_Alliancehttp://en.wikipedia.org/wiki/Wi-Fi_Alliancehttp://en.wikipedia.org/wiki/Wi-Fi_Alliancehttp://en.wikipedia.org/wiki/Australianhttp://en.wikipedia.org/wiki/Wi-Fihttp://en.wikipedia.org/wiki/CSIROhttp://en.wikipedia.org/wiki/John_O%27Sullivan_%28engineer%29http://en.wikipedia.org/wiki/Wi-Fihttp://en.wikipedia.org/wiki/Institute_of_Electrical_and_Electronics_Engineershttp://en.wikipedia.org/wiki/Vic_Hayeshttp://en.wikipedia.org/wiki/WaveLANhttp://en.wikipedia.org/wiki/AT%26T_Corporationhttp://en.wikipedia.org/wiki/NCR_Corporationhttp://en.wikipedia.org/wiki/NCR_Corporationhttp://en.wikipedia.org/wiki/ISM_band


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The IEEE does not test equipment forompliance with their standards. The non-profit

Wi-Fi Alliance was formed in 1999 to fill thisoid to establish and enforce standards fornteroperability and backward compatibility, ando promote wireless local-area-networkechnology. As of 2010, the Wi-Fi Alliance

onsisted of more than 375 companies fromround the world.[23][24] The Wi-Fi Alliancenforces the use of the Wi-Fi brand toechnologies based on the IEEE 802.11tandards from the Institute of Electrical and

Electronics Engineers. This includes wirelessocal area network (WLAN) connections, deviceo device connectivity (such as Wi-Fi Peer to

Peer aka Wi-Fi Direct), Personal area network

PAN), local area network (LAN) and evenome limited wide area network (WAN)onnections. Manufacturers with membershipn the Wi-Fi Alliance, whose products pass theertification process, gain the right to mark

hose products with the Wi-Fi logo.

Wi-Fi certification
http://en.wikipedia.org/wiki/Non-profithttp://en.wikipedia.org/wiki/Backward_compatibilityhttp://en.wikipedia.org/wiki/Wirelesshttp://en.wikipedia.org/wiki/Wi-Fihttp://en.wikipedia.org/wiki/IEEE_802.11http://en.wikipedia.org/wiki/Institute_of_Electrical_and_Electronics_Engineershttp://en.wikipedia.org/wiki/Institute_of_Electrical_and_Electronics_Engineershttp://en.wikipedia.org/wiki/Wireless_LANhttp://en.wikipedia.org/wiki/Wireless_LANhttp://en.wikipedia.org/wiki/Personal_area_networkhttp://en.wikipedia.org/wiki/Local_area_networkhttp://en.wikipedia.org/wiki/Wide_area_networkhttp://en.wikipedia.org/wiki/Wide_area_networkhttp://en.wikipedia.org/wiki/Local_area_networkhttp://en.wikipedia.org/wiki/Personal_area_networkhttp://en.wikipedia.org/wiki/Wireless_LANhttp://en.wikipedia.org/wiki/Wireless_LANhttp://en.wikipedia.org/wiki/Institute_of_Electrical_and_Electronics_Engineershttp://en.wikipedia.org/wiki/Institute_of_Electrical_and_Electronics_Engineershttp://en.wikipedia.org/wiki/IEEE_802.11http://en.wikipedia.org/wiki/Wi-Fihttp://en.wikipedia.org/wiki/Wi-Fihttp://en.wikipedia.org/wiki/Wirelesshttp://en.wikipedia.org/wiki/Backward_compatibilityhttp://en.wikipedia.org/wiki/Non-profithttp://en.wikipedia.org/wiki/Non-profithttp://en.wikipedia.org/wiki/Non-profit


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A Wi-Fi-enabled device can

connect to the Internet when withinrange of a wireless network whichis configured to permit this. The

coverage of one or more(interconnected) access pointscalled hotspots can extend froman area as small as a few rooms to

as large as many square miles.Coverage in the larger area mayrequire a group of access points

with overlapping coverage. Outdoopublic Wi-Fi technology has beenused successfully in wireless meshnetworks in London, UK.

Internet access
http://en.wikipedia.org/wiki/Wireless_networkhttp://en.wikipedia.org/wiki/Wireless_access_pointhttp://en.wikipedia.org/wiki/Wireless_mesh_networkhttp://en.wikipedia.org/wiki/Wireless_mesh_networkhttp://en.wikipedia.org/wiki/Wireless_mesh_networkhttp://en.wikipedia.org/wiki/Wireless_mesh_networkhttp://en.wikipedia.org/wiki/Wireless_access_pointhttp://en.wikipedia.org/wiki/Wireless_network


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n the early 2000s, many cities around theworld announced plans to construct city-

wide Wi-Fi networks. There are manyuccessful examples; in 2004, Mysorebecame India's first Wi-Fi-enabled cityand second in the world afterJerusalem.

A company called WiFiyNet has set upotspots in Mysore, covering the completeity and a few nearby villages.[n 2005, Sunnyvale, California, became

he first city in the United States to offerity-wide free Wi-Fi. Minneapolis hasenerated $1.2 million in profit annually

orits provider.

n May 2010, London, UK, MayorBorisohnson pledged to have London-wideWi-Fi by 2012. Several boroughsncluding Westminster and Islington

already have extensive outdoor Wi-Fioverage.

City-wide Wi-Fi
http://en.wikipedia.org/wiki/Mysorehttp://en.wikipedia.org/wiki/Jerusalemhttp://en.wikipedia.org/wiki/Wi-Fihttp://en.wikipedia.org/wiki/Sunnyvale,_Californiahttp://en.wikipedia.org/wiki/Minneapolishttp://en.wikipedia.org/wiki/Minneapolis_wireless_internet_networkhttp://en.wikipedia.org/wiki/Londonhttp://en.wikipedia.org/wiki/Boris_Johnsonhttp://en.wikipedia.org/wiki/Boris_Johnsonhttp://en.wikipedia.org/wiki/Boris_Johnsonhttp://en.wikipedia.org/wiki/Boris_Johnsonhttp://en.wikipedia.org/wiki/Londonhttp://en.wikipedia.org/wiki/Minneapolis_wireless_internet_networkhttp://en.wikipedia.org/wiki/Minneapolishttp://en.wikipedia.org/wiki/Sunnyvale,_Californiahttp://en.wikipedia.org/wiki/Wi-Fihttp://en.wikipedia.org/wiki/Jerusalemhttp://en.wikipedia.org/wiki/Mysore


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Wi-Fi allows cheaper deployment oflocal areaetworks (LANs). Also spaces where cables

annot be run, such as outdoor areas andistorical buildings, can host wireless LANs.Manufacturers are building wireless networkdapters into most laptops. The price ofchipsetsor Wi-Fi continues to drop, making it an

conomical networking option included in evenmore devices.[citation needed]Different competitive brands of access points andlient network-interfaces can inter-operate at aasic level of service. Products designated asWi-Fi Certified" by the Wi-Fi Alliance areackwards compatible. Unlike mobile phones,ny standard Wi-Fi device will work anywhere inhe world.

Wi-Fi Protected Access encryption (WPA2) isonsidered secure, provided a strongassphrase is used. New protocols forquality-of-ervice (WMM) make Wi-Fi more suitable foratency-sensitive applications (such as voice and

ideo). Power saving mechanisms (WMM PowerSave) extend battery life.

Advantages
http://en.wikipedia.org/wiki/Local_area_networkhttp://en.wikipedia.org/wiki/Local_area_networkhttp://en.wikipedia.org/wiki/Chipsethttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Backwards_compatiblehttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Wi-Fi_Protected_Accesshttp://en.wikipedia.org/wiki/Passphrasehttp://en.wikipedia.org/wiki/Quality_of_servicehttp://en.wikipedia.org/wiki/Quality_of_servicehttp://en.wikipedia.org/wiki/Wireless_Multimedia_Extensionshttp://en.wikipedia.org/wiki/Wireless_Multimedia_Extensionshttp://en.wikipedia.org/wiki/Quality_of_servicehttp://en.wikipedia.org/wiki/Quality_of_servicehttp://en.wikipedia.org/wiki/Quality_of_servicehttp://en.wikipedia.org/wiki/Quality_of_servicehttp://en.wikipedia.org/wiki/Quality_of_servicehttp://en.wikipedia.org/wiki/Passphrasehttp://en.wikipedia.org/wiki/Wi-Fi_Protected_Accesshttp://en.wikipedia.org/wiki/Wi-Fi_Protected_Accesshttp://en.wikipedia.org/wiki/Wi-Fi_Protected_Accesshttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Backwards_compatiblehttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Chipsethttp://en.wikipedia.org/wiki/Local_area_networkhttp://en.wikipedia.org/wiki/Local_area_network


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pectrum assignments and operational limitations areot consistent worldwide: most of Europe allows for andditional two channels beyond those permitted in theS for the 2.4 GHz band (113 vs. 111), while Japanas one more on top of that (114). As of 2007, Europe essentially homogeneous in this respect.

Wi-Fi signal occupies five channels in the 2.4 GHzand. Any two channel numbers that differ by five or

more, such as 2 and 7, do not overlap. The oft-repeateddage that channels 1, 6, and 11 are the onlynon-verlapping channels is, therefore, not accurate.hannels 1, 6, and 11 are the only group of three non-

verlapping channels in the U.S. In Europe and Japansing Channels 1, 5, 9, and 13 for802.11g and 802.11nrecommended.[citation needed]

quivalent isotropically radiated power(EIRP) in the EU limited to 20 dBm (100 mW).

he current 'fastest' norm, 802.11n, uses double theadio spectrum/bandwidth (40 MHz) compared to02.11a or 802.11g (20 MHz).[citation needed] This meanshere can be only one 802.11n network on the 2.4 GHzand at a given location, without interference to/fromther WLAN traffic. 802.11n can also be set to use

0 MHz bandwidth only to prevent interference in denseommunity.[citation needed]

Limitations
http://en.wikipedia.org/wiki/IEEE_802.11http://en.wikipedia.org/wiki/IEEE_802.11http://en.wikipedia.org/wiki/IEEE_802.11http://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Equivalent_isotropically_radiated_powerhttp://en.wikipedia.org/wiki/DBmhttp://en.wikipedia.org/wiki/IEEE_802.11http://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/IEEE_802.11http://en.wikipedia.org/wiki/DBmhttp://en.wikipedia.org/wiki/Equivalent_isotropically_radiated_powerhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/IEEE_802.11http://en.wikipedia.org/wiki/IEEE_802.11http://en.wikipedia.org/wiki/IEEE_802.11


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Wi-Fi networks have limited range. Aypical wireless access point using

802.11b or802.11g with a stock antennamight have a range of 35 m (120 ft)ndoors and 100 m (300 ft) outdoors. IEEE802.11n, however, can more than double

he range.[41] Range also varies withrequency band. Wi-Fi in the 2.4 GHzrequency block has slightly better rangehan Wi-Fi in the 5 GHz frequency block

which is used by 802.11a and optionallyby 802.11n. On wireless routers with

etachable antennas, it is possible tomprove range by fitting upgraded

antennas which have higher gain inparticular directions. Outdoor ranges canbe improved to many kilometers throughhe use of high gain directional antennas

at the router and remote device(s).

Range
http://en.wikipedia.org/wiki/IEEE_802.11http://en.wikipedia.org/wiki/IEEE_802.11http://en.wikipedia.org/wiki/IEEE_802.11http://en.wikipedia.org/wiki/IEEE_802.11http://en.wikipedia.org/wiki/Wi-Fihttp://en.wikipedia.org/wiki/Directional_antennahttp://en.wikipedia.org/wiki/Directional_antennahttp://en.wikipedia.org/wiki/Wi-Fihttp://en.wikipedia.org/wiki/IEEE_802.11http://en.wikipedia.org/wiki/IEEE_802.11http://en.wikipedia.org/wiki/IEEE_802.11http://en.wikipedia.org/wiki/IEEE_802.11


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The most common wireless encryption-tandard, Wired Equivalent Privacy (WEP),

as been shown to be easily breakable evenwhen correctly configured. Wi-Fi ProtectedAccess (WPA and WPA2) encryption, whichecame available in devices in 2003, aimedo solve this problem. Wi-Fi access pointsypically default to an encryption-free (open)

mode. Novice users benefit from a zero-onfiguration device that works out-of-the-ox, but this default does not enable any

wireless security, providing open wirelessccess to a LAN. To turn security on requireshe user to configure the device, usually via aoftware graphical user interface (GUI). Onnencrypted Wi-Fi networks connecting

evices can monitor and record datancluding personal information). Suchetworks can only be secured by using other

means of protection such as a VPN or

Data security risks
http://en.wikipedia.org/wiki/Encryptionhttp://en.wikipedia.org/wiki/Wired_Equivalent_Privacyhttp://en.wikipedia.org/wiki/Fluhrer,_Mantin_and_Shamir_attackhttp://en.wikipedia.org/wiki/Wi-Fi_Protected_Accesshttp://en.wikipedia.org/wiki/Wi-Fi_Protected_Accesshttp://en.wikipedia.org/wiki/Wireless_access_pointhttp://en.wikipedia.org/wiki/Wireless_securityhttp://en.wikipedia.org/wiki/Graphical_user_interfacehttp://en.wikipedia.org/wiki/Virtual_private_networkhttp://en.wikipedia.org/wiki/Virtual_private_networkhttp://en.wikipedia.org/wiki/Graphical_user_interfacehttp://en.wikipedia.org/wiki/Wireless_securityhttp://en.wikipedia.org/wiki/Wireless_access_pointhttp://en.wikipedia.org/wiki/Wi-Fi_Protected_Accesshttp://en.wikipedia.org/wiki/Wi-Fi_Protected_Accesshttp://en.wikipedia.org/wiki/Wi-Fi_Protected_Accesshttp://en.wikipedia.org/wiki/Wi-Fi_Protected_Accesshttp://en.wikipedia.org/wiki/Fluhrer,_Mantin_and_Shamir_attackhttp://en.wikipedia.org/wiki/Wired_Equivalent_Privacyhttp://en.wikipedia.org/wiki/Encryption

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