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Cellular network History

Cellular network History






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    Cellular network History Cellular network History Document Transcript

    • DECLARATION I, Mr. Kumar Gaurav hereby declare that this paper is the record of authenticstudy carried out by me during the First semester of my MCA and has not beensubmitted to any other University or Institute for the award of any degree etc.SignatureKUMAR GAURAVDate 1
    • ACKNOWLEDGEMENT The successful completion of a research all incomplete without mentioning thepeople who make it possible and whose guidance helped lot for the success of it. I hereby express my gratitude and sincere thanks to Dr. M S Prasad(Director, MCA, I.M.E.D, Bharti VidyaPeeth, Pune )for providing me all opportunityto do this opportunity for studying this topic. I also express my sincere thanks to Mrs. Baljeet kaur my guide,for her timely and invaluable help and suggestion and encouragement until completionof this study. Signature KUMAR GAURAV 2
    • Evolution of Mobile Phones KUMAR GAURAVMCA 1st sem Roll No.26 Email Id-gauravsitu@gmail.com______________________________________________________Statement of the problem:-The problem is to study Evolution and development of Mobile phones .The problem is subdivided further into following topics.  1. Introduction to Mobile phones.  2. History of Mobile phones.  3. Course of development.  4. Generations. i. 1G ii. 2G iii. 2.5G iv. 3G v. 4G  5. Cellular networks  Technologies used in cellular network. i. GSM ii. CDMA iii. OFDMA iv. 3G 3
    • Table of Content. Content Page No.Introduction to Mobile phones. 4History of Mobile phones. 4Course of development. 5First Generations. 10Second Generations. 10Third generation. 11Forth generation 13Cellular networks 15Technologies used in cellular network. 16GSM 17CDMA 24OFDMA 263G 30Summary 32Conclusion 34 4
    • HistoryThis history of mobile phones chronicles the development of radio telephonetechnology from two-way radios in vehicles to handheld cellular communicatingdevices.In the beginning, two-way radios (known as mobile rigs) were used in vehicles such astaxicabs, police cruisers, ambulances, and the like, but were not mobile phones becausethey were not normally connected to the telephone network. Users could not dial phonenumbers from their vehicles. A large community of mobile radio users, known as themobileers, popularized the technology that would eventually give way to the mobilephone. Originally, mobile phones were permanently installed in vehicles, but laterversions such as the so-called transportables or "bag phones" were equipped with acigarette lighter plug so that they could also be carried, and thus could be used as eithermobile or as portable two-way radios. During the early 1940s, Motorola developed abackpacked two-way radio, the Walkie-Talkie and later developed a large hand-heldtwo-way radio for the US military. This battery powered "Handie-Talkie" (HT) wasabout the size of a mans forearm.  In 1866  The first trans-Atlantic telegraph is built (not much to do with cell phones, but a major advancement in communication nonetheless.  In 1910  Lars Magnus Ericsson installed a telephone in his car, although this was not a radio telephone. While travelling across the country, he would stop at a place where telephone lines were accessible and using a pair of long electric wires he could connect to the national telephone network.  In 1921  The Police Department in Detroit, Mich. begins installing mobile radios, operating around 2 MHz, in their squad cars. They encounter many problems such as overcrowding on the channels and terrible interference. 5
    •  In 1934  The U.S. Congress creates the Federal Communications Commission. They decide who gets to use certain radio frequencies. Most channels are reserved for emergency use and for the government. Radio is still a baby. In 1940’s  the mobile radios are able to operate at 30 to 40 MHz and become much more common between police departments, and the wealthy. Several private companies and organizations begin using these same radios for personal gain. In1945  The first mobile-radio-telephone service is established in St. Louis, Miss. The system is comprised of six channels that add up to 150 MHz. The project is approved by the FCC, but due to massive interference, the equipment barely works. In 1946 soviet engineers G. Shapiro and I. Zaharchenko successfully tested their version of a radio mobile phone mounted inside a car. The device could connect to local telephone network on a range up to 20 kilometers. In 1947  Douglas H. Ring and W. Rae Young, Bell Labs engineers, proposed hexagonal cells for mobile phones in vehicles. Philip T. Porter, also of Bell Labs, proposed that the cell towers be at the corners of the hexagons rather than the centers and have directional antennas that would transmit/receive in 3 directions into 3 adjacent hexagon cells AT&T comes out with the first radio-car-phones that can be used only on the highway between New York and Boston; they are known as push-to-talk phones. The system operates at frequencies of about 35 to 44 MHz, but once again there is a massive amount of interference in the system. AT&T declares the project a failure. 6
    •  In 1949  The FCC authorizes the widespread use of many separate radio channels to other carriers. They are know as Radio Common Carriers (RCC) and are the first link between mobile phones and the telephone, rather than just radio to radio. The RCCs are the first step toward the cellular phone industry, which is were designed more for profit than for the general public. In 1956  The first real car phones, not car radios, come into play accross the United States. Although, the system is still using push-to-talk phones, it is an improved version that acctually works. However, the units are big and bulky, and require a personal radio operator to switch the calls. A simular system appeared in Sweden a few years earlier. In 1964  A new operating system is developed that operates on a single channel at 150 MHz. In essence, this removes the need for push-to-talk operators. Now customers can dial phone numbers directly from their cars. RCCs are finally taken seriously by the FCC as ligitimate competitors to the land-line phone companies. In 1966  Bulgaria presented the pocket mobile automatic phone RAT-0,5 combined with a base station RATZ-10 (RATC-10) on Interorgtechnika-66 international exhibition. One base station, connected to one telephone wire line, could serve up to 6 customers. In 1967  each mobile phone had to stay within the cell area serviced by one base station throughout the phone call. This did not provide continuity of automatic telephone service to mobile phones moving through several cell areas. In 1970 Amos E. Joel, Jr., another Bell Labs engineer, invented an automatic "call handoff" system to allow mobile phones to move through several cell areas during a single conversation without loss of conversation. 7
    •  In 1969  The self-dialing capability is now upgraded to 450 MHz and becomes standard in the United States. This new service is known as (IMTS) Improved mobile telephone service.  In 1970  Cell phone lobbyists finally win with the FCC and get a window of 75 MHz in the 800 MHz region, which allocated specifically for cell phones. The FCC realizes the potential of the industry and can’t ignore it any longer.  In 1971  AT&T is the first company to propose a modern-day mobile-phone system to the FCC. It involves dividing cities into “cells”. It is the first company to do so.  In 1973  Dr. Martin Cooper invents the first personal handset while working for Motorola. He takes his new invention, the Motorola Dyna-Tac., to New York City and shows it to the public. His is credited with being the first person to make a call on a portable mobile-phone.Top of cellular telephone tower Dr. Martin Cooper of Motorola, made the first US analogue mobile phone call on a larger prototype model in 1973. 8
    • One of the first successful public commercial mobile phone networks was the ARPnetwork in Finland, launched in 1971. Posthumously, ARP is sometimes viewed as azero generation (0G) cellular network, being slightly above previous proprietary andlimited coverage networks. The First Mobile Phone: Motorola DynaTAC 8000X (1983) Motorolas DynaTAC 8000X wasnt commercially available until 1983, but its beginnings can be tracked back to 1973 when the company showed off a prototype of what would become the worlds first mobile phone. The DynaTAC weighed almost a kilogram, provided one hour of battery life and stored 30 phone numbers in its phonebook. The Motorola DynaTAC is best known for bring used in the 1987 movie Wall Street, starring Michael Douglas as corporate raider Gordon Gecko.  In 1975  AT&T adapts its own cellular plan for the city of Chicago, but the FCC is still uneasy about putting the plan into action. They have concerns about its success. 9
    •  In 1977  Finally cell phone testing is permitted by the FCC in Chicago. The Bell Telephone Company gets the license; they are in a partnership with AT&T which is a gerneral effort to battle the stubborn FCC. In 1981  The FCC makes firm rules about the growing cell phone industry in dealing with manufactures. It finally rules that Western Electric can manufacture products for both cellular and terminal use. (Basically they admit that they put the phone companies about 7 years behind) First Car Phone: Nokia Mobira Senator (1982) In the early 1980s, the mobile phone was best known for its in-car use. Nokias Mobira Senator, released in 1982, was the first of its kind. A car phone that weighed almost 10 kilograms, the Nokia Mobira Senator resembled a large radio rather than a conventional mobile phone. In 1988  One of the most important years in cell phone evolution. The Cellular Technology Industry Association is created and helps to make the industry into an empire. One of its biggest contributions is when it helped create TDMA phone technology, the most evolved cell phone yet. It becomes available to the public in 1991 10
    • GENERATIONS OF MOBILE PHONESFirst generation(1G) 1G (First Generation) is the name given to the first generation of mobile telephone networks. These systems used analogue circuit-switched technology, with FDMA (Frequency Division Multiple Access), and worked mainly in the 800-900 MHz frequency bands. The networks had a low traffic capacity, unreliable handover, poor voice quality, and poor security.First Generation mobile phone networks were the earliest cellular systems to develop,and they relied on a network of distributed transceivers to communicate with the mobilephones. First Generation phones were also analogue, used for voice calls only, and theirsignals were transmitted by the method of frequency modulation. These systemstypically allocated one 25 MHz frequency band for the signals to be sent from the cellbase station to the handset, and a second different 25 MHz band for signals beingreturned from the handset to the base station. These bands were then split into a numberof communications channels, each of which would be used by a particular caller.Second Generation(2G) 2G - Second Generation mobile telephone networks were the logical next stage in the development of wireless systems after 1G, and they introduced for the first time a mobile phone system that used purely digital technology. The demands placed on the networks, particularly in the densely populated areas within cities, meant that increasingly sophisticated methods had to be employed to handle the large number of calls, and so avoid the risks of interference and dropped calls at handoffs. Although many of the principles involved in a 1G system also apply to 2G -they both use the same cell structure - there are also differences in the way that thesignals are handled, and the 1G networks are not capable of providing the moreadvanced features of the 2G systems, such as caller identity and text messaging. 11
    • In GSM 900, for example, two frequency bands of 25 MHz bandwidth are used. Theband 890-915 MHz is dedicated to uplink communications from the mobile station tothe base station, and the band 935-960 MHz is used for the downlink communicationsfrom the base station to the mobile station. Each band is divided into 124 carrierfrequencies, spaced 200 kHz apart, in a similar fashion to the FDMA method used in 1Gsystems. Then, each carrier frequency is further divided using TDMA into eight 577 uSlong "time slots", every one of which represents one communication channel - the totalnumber of possible channels available is therefore 124 x 8, producing a theoreticalmaximum of 992 simultaneous conversations. In the USA, a different form of TDMA isused in the system known as IS-136 D-AMPS, and there is another US system calledIS-95 (CDMAone), which is a spread spectrum code division multiple access (CDMA)system. CDMA is the technique used in 3G systems.2.5G 2.5G (Second Generation Enhanced) is a generic term used to refer to a standard of wireless mobile telephone networks that lies somewhere between 2G and 3G. The development of 2.5G has been viewed as a stepping-stone towards 3G, which was prompted by the demand for better data services and access to the Internet. In the evolution of mobile communications, each generation provides a higher data rate and additional capabilities, and 2.5G is no exception as it is provides fasterservices than 2G, but not as fast or as advanced as the newer 3G systems.Some observers have seen 2.5G as an alternative route to 3G, but this appears to beshort-sighted as 2.5G is several times slower than the full 3G service. In technical terms2.5G extends the capabilities of 2G systems by providing additional features, such as apacket-switched connection (GPRS) in the TDMA-based GSM system, and enhanceddata rates (HSCSD and EDGE).These enhancements in 2.5G systems permit data speeds of 64-144 kbps, which enablesthese phones to feature web browsing, the use of navigation and navigational maps,voice mail, fax, and the sending and receiving of large email messages. 12
    • Third Generation (3G)3G - Third Generation mobile telephone networks are the latest stage in the developmentof wireless communications technology. Significant features of 3G systems are that theysupport much higher data transmission rates and offer increased capacity, which makesthem suitable for high-speed data applications as well as for the traditional voice calls.In fact, 3G systems are designed to process data, and since voice signals are converted todigital data, this results in speech being dealt with in much the same way as any otherform of data. Third Generation systems use packet-switching technology, which is moreefficient and faster than the traditional circuit-switched systems, but they do require asomewhat different infrastructure to the 2G systems.Compared to earlier mobile phones a 3G handset provides many new features, and thepossibilities for new services are almost limitless, including many popular applicationssuch as TV streaming, multimedia, videoconferencing, Web browsing, e-mail, paging,fax, and navigational maps.Japan was the first country to introduce a 3G system, which was largely because theJapanese PDC networks were under severe pressure from the vast appetite in Japan fordigital mobile phones. Unlike the GSM systems, which developed various ways to dealwith demand for improved services, Japan had no 2.5G enhancement stage to bridge thegap between 2G and 3G, and so the move into the new standard was seen as a solutionto their capacity problems.It is generally accepted that CDMA is a superior transmission technology, when it iscompared to the old techniques used in GSM/TDMA. WCDMA systems make moreefficient use of the available spectrum, because the CDMA technique enables all basestations to use the same frequency. In the WCDMA system, the data is split into separatepackets, which are then transmitted using packet switching technology, and the packetsare reassembled in the correct sequence at the receiver end by using the code that is sentwith each packet. WCDMA has a potential problem, caused by the fact that, as moreusers simultaneously communicate with a base station, then a phenomenon known as“cell breathing” can occur. This effect means that the users will compete for the finitepower of the base station’s transmitter, which can reduce the cell’s range – W-CDMAand cdma2000 have been designed to alleviate this problem. 13
    • The operating frequencies of many 3G systems will typically use parts of the radiospectrum in the region of approximately 2GHz (the IMT-2000 core band), which werenot available to operators of 2G systems, and so are away from the crowded frequencybands currently being used for 2G and 2.5G networks. UMTS systems are designed toprovide a range of data rates, depending on the user’s circumstances, providing up to144 kbps for moving vehicles (macrocellular environments), up to 384 kbps forpedestrians (microcellular environments) and up to 2 Mbps for indoor or stationary users(picocellular environments). In contrast, the data rates supported by the basic 2Gnetworks were only 9.6 kbps, such as in GSM, which was inadequate to provide anysophisticated digital services.Forth generation (4G)As the limitation of the 3G, people are try to make new generation of mobilecommunication, this is the 4th generation. This 4G system is more reliable,Nowadays, some companies have started developing the 4G communication system, thistechnology can have a high uplink rate up to 200Mbps, more data can transfer in themobile phone. So the 4G mobile can have more function such as work as the television.Some telecommunication companies claimed that they would applied this 4G system tothe business and it will bring more convenience to people. 14
    • Technology 1G 2G 2.5G 3G 4G 5G Beyond 4G will be 5G with incredible transmission speed with no limitation for access and zone size1Design Begin 1970 1980 1985 1990 2000 Implementat 1984 1991 1999 2002 2010ionService Analog voice, Digital voice, Higher Higher CompletelyIP synchronous data short messages capacity, capacity, oriented, 9.6 kbps packetized broadband multimedia, data data up to 2 Data to hundreds Mbps of megabitsStandards AMPS, TACS, TDMA, CDMA, GPRS, WCDMA, Single standard NMT, etc. GSM, PDC EDGE, CDMA2000 1xRTTData Bandwidth 1.9 kbps 14.4 kbps 384 kbps 2 Mbps 200 MbpsMultiplexing FDMA TDMA, CDMA TDMA,CD CDMA CDMA? MACore Network PSTN PSTN PSTN, Packet Internet Packet network Network 15
    • Cellular network Mobile phone networksThe most common example of a cellular network is a mobile phone (cell phone)network. A mobile phone is a portable telephone which receives or makes calls througha cell site (base station), or transmitting tower. Radio waves are used to transfer signalsto and from the cell phone. Large geographic areas (representing the coverage range of aservice provider) may be split into smaller cells to avoid line-of-sight signal loss and thelarge number of active phones in an area. In cities, each cell site has a range of up toapproximately ½ mile, while in rural areas, the range is approximately 5 miles. Manytimes in clear open areas, a user may receive signals from a cellsite 25 miles away. Allof the cell sites are connected to cellular telephone exchanges "switches", which connectto a public telephone network or to another switch of the cellular company.As the phone user moves from one cell area to another cell, the switch automaticallycommands the handset and a cell site with a stronger signal (reported by each handset)to switch to a new radio channel (frequency). When the handset responds through thenew cell site, the exchange switches the connection to the new cell site.With CDMA, multiple CDMA handsets share a specific radio channel. The signals areseparated by using a pseudonoise code (PN code) specific to each phone. As the usermoves from one cell to another, the handset sets up radio links with multiple cell sites(or sectors of the same site) simultaneously. This is known as "soft handoff" because,unlike with traditional cellular technology, there is no one defined point where the phoneswitches to the new cell.Modern mobile phone networks use cells because radio frequencies are a limited, sharedresource. Cell-sites and handsets change frequency under computer control and use lowpower transmitters so that a limited number of radio frequencies can be simultaneouslyused by many callers with less interference.Since almost all mobile phones use cellular technology, including GSM, CDMA, andAMPS (analog), the term "cell phone" is used interchangeably with "mobile phone".However, satellite phones are mobile phones that do not communicate directly with aground-based cellular tower, but may do so indirectly by way of a satellite.Old systems predating the cellular principle may still be in use in places. The mostnotable real hold-out is used by many amateur radio operators who maintain phonepatches in their clubs VHF repeaters. 16
    • There are a number of different digital cellular technologies, including: Global System for Mobile Communications (GSM), General Packet Radio Service(GPRS), Code Division Multiple Access (CDMA), Evolution-Data Optimized (EV-DO), Enhanced Data Rates for GSM Evolution (EDGE), 3GSM, Digital EnhancedCordless Telecommunications (DECT), Digital AMPS (IS-136/TDMA), and IntegratedDigital Enhanced Network (iDEN). 17
    • GSMGSM (Global System for Mobile communications: originally from Groupe SpécialMobile) is the most popular standard for mobile phones in the world. Its promoter, theGSM Association, estimates that 80% of the global mobile market uses the standard.GSM is used by over 3 billion people across more than 212 countries and territories. Itsubiquity makes international roaming very common between mobile phone operators,enabling subscribers to use their phones in many parts of the world. GSM differs fromits predecessors in that both signaling and speech channels are digital, and thus isconsidered a second generation (2G) mobile phone system. This has also meant that datacommunication was easy to build into the system.The ubiquity of the GSM standard has been an advantage to both consumers (whobenefit from the ability to roam and switch carriers without switching phones) and alsoto network operators (who can choose equipment from any of the many vendorsimplementing GSM). GSM also pioneered a low-cost (to the network carrier) alternativeto voice calls, the short message service (SMS, also called "text messaging"), which isnow supported on other mobile standards as well. Another advantage is that the standardincludes one worldwide emergency telephone number, 112. This makes it easier forinternational travellers to connect to emergency services without knowing the localemergency number.Newer versions of the standard were backward-compatible with the original GSMphones. For example, Release 97 of the standard added packet data capabilities, bymeans of General Packet Radio Service (GPRS). Release 99 introduced higher speeddata transmission using Enhanced Data Rates for GSM Evolution (EDGE). 18
    • HistoryIn 1982, the European Conference of Postal and Telecommunications Administrations(CEPT) created the Groupe Spécial Mobile (GSM) to develop a standard for a mobiletelephone system that could be used across Europe.[6] In 1987, a memorandum ofunderstanding was signed by 13 countries to develop a common cellular telephonesystem across Europe. Finally the system created by SINTEF lead by Torleiv Masengwas selected.In 1989, GSM responsibility was transferred to the European TelecommunicationsStandards Institute (ETSI) and phase I of the GSM specifications were published in1990. The first GSM network was launched in 1991 by Radiolinja in Finland with jointFirst GSM Phone: Nokia 101 technical infrastructure maintenance from(1992) Ericsson. By the end of 1993, over a million subscribers were using GSM phone networksNokias 101 was the worlds first being operated by 70 carriers across 48 countries.commercially available GSMmobile phone. Paving the way forfuture "candy-bar" designs, the101 had a monochrome display, anextendable antenna and aphonebook that could store 99phone numbers. It did howeverlack Nokias famous "Nokia tune"ringtone — this wasnt introduceduntil the next model in 1994. 19
    • Technical detailsCellular radio networkGSM is a cellular network, which means that mobile phones connect to it by searchingfor cells in the immediate vicinity.There are five different cell sizes in a GSM network—macro, micro, pico, femto andumbrella cells. The coverage area of each cell varies according to the implementationenvironment. Macro cells can be regarded as cells where the base station antenna isinstalled on a mast or a building above average roof top level. Micro cells are cellswhose antenna height is under average roof top level; they are typically used in urbanareas. Picocells are small cells whose coverage diameter is a few dozen metres; they aremainly used indoors. Femtocells are cells designed for use in residential or smallbusiness environments and connect to the service provider’s network via a broadbandinternet connection. Umbrella cells are used to cover shadowed regions of smaller cellsand fill in gaps in coverage between those cells.Cell horizontal radius varies depending on antenna height, antenna gain and propagationconditions from a couple of hundred meters to several tens of kilometres. The longestdistance the GSM specification supports in practical use is 35 kilometres (22 mi). Thereare also several implementations of the concept of an extended cell, where the cellradius could be double or even more, depending on the antenna system, the type ofterrain and the timing advance.Indoor coverage is also supported by GSM and may be achieved by using an indoorpicocell base station, or an indoor repeater with distributed indoor antennas fed throughpower splitters, to deliver the radio signals from an antenna outdoors to the separateindoor distributed antenna system. These are typically deployed when a lot of callcapacity is needed indoors; for example, in shopping centers or airports. However, this isnot a prerequisite, since indoor coverage is also provided by in-building penetration ofthe radio signals from any nearby cell. 20
    • The modulation used in GSM is Gaussian minimum-shift keying (GMSK), a kind ofcontinuous-phase frequency shift keying. In GMSK, the signal to be modulated onto thecarrier is first smoothed with a Gaussian low-pass filter prior to being fed to a frequencymodulator, which greatly reduces the interference to neighboring channels (adjacentchannel interference).Interference with audio devicesSome audio devices are susceptible to radio frequency interference (RFI), which couldbe mitigated or eliminated by use of additional shielding and/or bypass capacitors inthese audio devices. However, the increased cost of doing so is difficult for a designer tojustify.It is a common occurrence for a nearby GSM handset to induce a "dit, dit di-dit, dit di-dit, dit di-dit" audio output on PAs, wireless microphones, home stereo systems,televisions, computers, cordless phones, and personal music devices. When these audiodevices are in the near field of the GSM handset, the radio signal is strong enough thatthe solid state amplifiers in the audio chain act as a detector. The clicking noise itselfrepresents the power bursts that carry the TDMA signal. These signals have been knownto interfere with other electronic devices, such as car stereos and portable audio players.This also depends on the handsets design, and its conformance to strict rules andregulations allocated by the US body, the FCC, in part 15 of its rules and regulationspertaining to interference with electronic devices.GSM frequenciesGSM networks operate in a number of different frequency ranges (separated into GSMfrequency ranges for 2G and UMTS frequency bands for 3G). Most 2G GSM networksoperate in the 900 MHz or 1800 MHz bands. Some countries in the Americas (includingCanada and the United States) use the 850 MHz and 1900 MHz bands because the 900and 1800 MHz frequency bands were already allocated. Most 3G GSM networks inEurope operate in the 2100 MHz frequency band.The rarer 400 and 450 MHz frequency bands are assigned in some countries where thesefrequencies were previously used for first-generation systems. 21
    • GSM-900 uses 890–915 MHz to send information from the mobile station to the basestation (uplink) and 935–960 MHz for the other direction (downlink), providing 125 RFchannels (channel numbers 0 to 124) spaced at 200 kHz. Duplex spacing of 45 MHz isused.In some countries the GSM-900 band has been extended to cover a larger frequencyrange. This extended GSM, E-GSM, uses 880–915 MHz (uplink) and 925–960 MHz(downlink), adding 50 channels (channel numbers 975 to 1023 and 0) to the originalGSM-900 band. Time division multiplexing is used to allow eight full-rate or sixteenhalf-rate speech channels per radio frequency channel. There are eight radio timeslots(giving eight burst periods) grouped into what is called a TDMA frame. Half ratechannels use alternate frames in the same timeslot. The channel data rate for all 8channels is 270.833 kbit/s, and the frame duration is 4.615 ms.The transmission power in the handset is limited to a maximum of 2 watts inGSM850/900 and 1 watt in GSM1800/1900..Network structure 22
    • The structure of a GSM networkThe network behind the GSM seen by the customer is large and complicated in order toprovide all of the services which are required. It is divided into a number of sections andthese are each covered in separate articles. • the Base Station Subsystem (the base stations and their controllers). • the Network and Switching Subsystem (the part of the network most similar to a fixed network). This is sometimes also just called the core network. • the GPRS Core Network (the optional part which allows packet based Internet connections). • all of the elements in the system combine to produce many GSM services such as voice calls and SMS.Subscriber Identity Module (SIM)One of the key features of GSM is the Subscriber Identity Module, commonly known asa SIM card. The SIM is a detachable smart card containing the users subscriptioninformation and phone book. This allows the user to retain his or her information afterswitching handsets. Alternatively, the user can also change operators while retaining thehandset simply by changing the SIM. Some operators will block this by allowing thephone to use only a single SIM, or only a SIM issued by them; this practice is known asSIM locking, and is illegal in some countries.In Australia, North America and Europe many operators lock the mobiles they sell. Thisis done because the price of the mobile phone is typically subsidised with revenue fromsubscriptions, and operators want to try to avoid subsidising competitors mobiles. Asubscriber can usually contact the provider to remove the lock for a fee, utilize privateservices to remove the lock, or make use of ample software and websites available onthe Internet to unlock the handset themselves. While most web sites offer the unlockingfor a fee, some do it for free. The locking applies to the handset, identified by itsInternational Mobile Equipment Identity (IMEI) number, not to the account (which isidentified by the SIM card).In some countries such as Bangladesh, Belgium, Costa Rica, Indonesia, Malaysia, HongKong and Pakistan, all phones are sold unlocked. However, in Belgium, it is unlawfulfor operators there to offer any form of subsidy on the phones price. This was also thecase in Finland until April 1, 2006, when selling subsidized combinations of handsetsand accounts became legal, though operators have to unlock phones free of charge aftera certain period (at most 24 months). 23
    • GSM securityGSM was designed with a moderate level of security. The system was designed toauthenticate the subscriber using a pre-shared key and challenge-response.Communications between the subscriber and the base station can be encrypted. Thedevelopment of UMTS introduces an optional USIM, that uses a longer authenticationkey to give greater security, as well as mutually authenticating the network and the user- whereas GSM only authenticates the user to the network (and not vice versa). Thesecurity model therefore offers confidentiality and authentication, but limitedauthorization capabilities, and no non-repudiation. GSM uses several cryptographicalgorithms for security. The A5/1 and A5/2 stream ciphers are used for ensuring over-the-air voice privacy. A5/1 was developed first and is a stronger algorithm used withinEurope and the United States; A5/2 is weaker and used in other countries. Seriousweaknesses have been found in both algorithms: it is possible to break A5/2 in real-timewith a ciphertext-only attack, and in February 2008, Pico Computing, Inc revealed itsability and plans to commercialize FPGAs that allow A5/1 to be broken with a rainbowtable attack. The system supports multiple algorithms so operators may replace thatcipher with a stronger one… 24
    • CDMACode division multiple access (CDMA) is a channel access method utilized by variousradio communication technologies. It should not be confused with the mobile phonestandards called cdmaOne and CDMA2000 (which are often referred to as simply"CDMA"), which use CDMA as an underlying channel access method.One of the basic concepts in data communication is the idea of allowing severaltransmitters to send information simultaneously over a single communication channel.This allows several users to share a bandwidth of different frequencies. This concept iscalled multiplexing. CDMA employs spread-spectrum technology and a special codingscheme (where each transmitter is assigned a code) to allow multiple users to bemultiplexed over the same physical channel. By contrast, time division multiple access(TDMA) divides access by time, while frequency-division multiple access (FDMA)divides it by frequency. CDMA is a form of "spread-spectrum" signaling, since themodulated coded signal has a much higher data bandwidth than the data beingcommunicated.An analogy to the problem of multiple access is a room (channel) in which people wishto communicate with each other. To avoid confusion, people could take turns speaking(time division), speak at different pitches (frequency division), or speak in differentlanguages (code division). CDMA is analogous to the last example where peoplespeaking the same language can understand each other, but not other people. Similarly,in radio CDMA, each group of users is given a shared code. Many codes occupy thesame channel, but only users associated with a particular code can understand eachother. 25
    • UsesA CDMA mobile phone • One of the early applications for code division multiplexing—predating, and distinct from cdmaOne—is in GPS. • The Qualcomm standard IS-95, marketed as cdmaOne. • The Qualcomm standard IS-2000, known as CDMA2000. This standard is used by several mobile phone companies, including the Globalstar satellite phone network. • CDMA has been used in the OmniTRACS satellite system for transportation logistics. 26
    • OFDMAOrthogonal Frequency-Division Multiple Access (OFDMA) is a multi-user version ofthe popular Orthogonal frequency-division multiplexing (OFDM) digital modulationscheme. Multiple access is achieved in OFDMA by assigning subsets of subcarriers toindividual users as shown in the illustration below. This allows simultaneous low datarate transmission from several users.Claimed advantages over CDMA • OFDM can combat multipath interference with more robustness and less complexity. • OFDMA can achieve a higher MIMO spectral efficiency due to providing flatter frequency channels than a CDMA RAKE receiver can. • No Cell size breathing as more users connectClaimed OFDMA Advantages • Flexibility of deployment across various frequency bands with little needed modification to the air interface. • Averaging interferences from neighboring cells, by using different basic carrier permutations between users in different cells. • Interferences within the cell are averaged by using allocation with cyclic permutations. • Enables orthogonality in the uplink by synchronizing users in time and frequencyEnables Single Frequency Network coverage, where coverage problem exists and givesexcellent coverage • Enables adaptive carrier allocation in multiplication of 23 carriers = nX23 carriers up to 1587 carriers (all data carriers). • Offers Frequency diversity by spreading the carriers all over the used spectrum. • Offers Time diversity by optional interleaving of carrier groups in time. • Using the cell capacity to the utmost by adaptively using the highest modulation a user can use, this is allowed by the gain added when less carriers are allocated (up to 18dB gain for 23 carrier allocation instead of 1587 carriers), therefore gaining in overall cell capacity. 27
    • Recognised disadvantages of OFDMA • Higher sensitivity to frequency offsets and phase noise. • Asynchronous data communication services such as web access are characterized by short communication bursts at high data rate. Few users in a base station cell are transferring data simultaneously at low constant data rate. • The complex OFDM electronics, including the FFT algorithm and forward error correction, is constantly active independent of the data rate, which is inefficient from power consumption point of view, while OFDM combined with data packet scheduling may allow that the FFT algorithm hibernates during certain time intervals. • The OFDM diversity gain, and resistance to frequency-selective fading, may partly be lost if very few sub-carriers are assigned to each user, and if the same carrier is used in every OFDM symbol. Adaptive sub-carrier assignment based on fast feedback information about the channel, or sub-carrier frequency hopping, is therefore desirable. • Dealing with co-channel interference from nearby cells is more complex in OFDM than in CDMA. It would require dynamic channel allocation with advanced coordination among adjacent base stations. • The fast channel feedback information and adaptive sub-carrier assignment is more complex than CDMA fast power control. Characteristics and principles of operation • Based on feedback information about the channel conditions, adaptive user-to- subcarrier assignment can be achieved. If the assignment is done sufficiently fast, this further improves the OFDM robustness to fast fading and narrow-band cochannel interference, and makes it possible to achieve even better system spectral efficiency. • Different number of sub-carriers can be assigned to different users, in view to support differentiated Quality of Service (QoS), i.e. to control the data rate and error probability individually for each user. • OFDMA resembles code division multiple access (CDMA) spread spectrum, where users can achieve different data rates by assigning a different code spreading factor or a different number of spreading codes to each user. 28
    • • OFDMA can be seen as an alternative to combining OFDM with time division multiple access (TDMA) or time-domain statistical multiplexing, i.e. packet mode communication. Low-data-rate users can send continuously with low transmission power instead of using a "pulsed" high-power carrier. Constant delay, and shorter delay, can be achieved. • OFDMA can also be described as a combination of frequency domain and time domain multiple access, where the resources are partitioned in the time-frequency space, and slots are assigned along the OFDM symbol index as well as OFDM sub-carrier index. • OFDMA is considered as highly suitable for broadband wireless networks, due to advantages including scalability and MIMO-friendliness, and ability to take advantage of channel frequency selectivity.[1] • In spectrum sensing cognitive radio, OFDMA is a possible approach to filling free radio frequency bands adaptively. Timo A. Weiss and Friedrich K. Jondral of the University of Karlsruhe proposed a spectrum Pooling system in which free bands sensed by nodes were immediately filled by OFDMA subbands.UsageOFDMA is used in: • the mobility mode of the IEEE 802.16 Wireless MAN standard, commonly referred to as WiMAX, • the IEEE 802.20 mobile Wireless MAN standard, commonly referred to as MBWA, • the downlink of the 3GPP Long Term Evolution (LTE) fourth generation mobile broadband standard. The radio interface was formerly named High Speed OFDM Packet Access (HSOPA), now named Evolved UMTS Terrestrial Radio Access (E-UTRA). • the Qualcomm Flarion Technologies Mobile Flash-OFDM • the now defunct Qualcomm/3GPP2 Ultra Mobile Broadband (UMB) project, intended as a successor of CDMA2000, but replaced by LTE.OFDMA is also a candidate access method for the IEEE 802.22 Wireless Regional AreaNetworks (WRAN). The project aims at designing the first cognitive radio basedstandard operating in the VHF-low UHF spectrum (TV spectrum).The term "OFDMA" is claimed to be a registered trademark by Runcom TechnologiesLtd., with various other claimants to the underlying technologies through patents. 29
    • 3GInternational Mobile Telecommunications-2000 (IMT-2000), better known as 3G or 3rdGeneration, is a family of standards for mobile telecommunications defined by theInternational Telecommunication Union, which includes GSM, EDGE, UMTS, andCDMA2000 as well as DECT and WiMAX. Services include wide-area wireless voicetelephone, video calls, and wireless data, all in a mobile environment. Compared to 2Gand 2.5G services, 3G allows simultaneous use of speech and data services and higherdata rates (up to 14.0 Mbit/s on the downlink and 5.8 Mbit/s on the uplink with HSPA+).Thus, 3G networks enable network operators to offer users a wider range of moreadvanced services while achieving greater network capacity through improved spectralefficiency.The International Telecommunication Union (ITU) defined the third generation (3G) ofmobile telephony standards – IMT-2000 – to facilitate growth, increase bandwidth, andsupport more diverse applications. For example, GSM (the current most popular cellularphone standard) could deliver not only voice, but also circuit-switched data at downloadrates up to 14.4 kbps. But to support mobile multimedia applications, 3G had to deliverpacket-switched data with better spectral efficiency, at far greater bandwidthsThe first pre-commercial 3G network was launched by NTT DoCoMo in Japan brandedFOMA, in May 2001 on a pre-release of W-CDMA technology. The first commerciallaunch of 3G was also by NTT DoCoMo in Japan on October 1, 2001, although it wasinitially somewhat limited in scope; broader availability was delayed by apparentconcerns over reliability. The second network to go commercially live was by SKTelecom in South Korea on the 1xEV-DO technology in January 2002. By May 2002the second South Korean 3G network was by KTF on EV-DO and thus the Koreanswere the first to see competition among 3G operators.The first commercial United States 3G network was by Monet Mobile Networks, onCDMA2000 1x EV-DO technology, but this network provider later shut downoperations. The second 3G network operator in the USA was Verizon Wireless inOctober 2003 also on CDMA2000 1x EV-DO. AT&T Mobility is also a true 3Gnetwork, having completed its upgrade of the 3G network to HSUPA.In December 2007, 190 3G networks were operating in 40 countries and 154 HSDPAnetworks were operating in 71 countries, according to the Global Mobile SuppliersAssociation (GSA). In Asia, Europe, Canada and the USA, telecommunication 30
    • companies use W-CDMA technology with the support of around 100 terminal designs tooperate 3G mobile networks.In Europe, mass market commercial 3G services were introduced starting in March 2003by 3 (Part of Hutchison Whampoa) in the UK and Italy. The European Union Councilsuggested that the 3G operators should cover 80% of the European national populationsby the end of 2005.Roll-out of 3G networks was delayed in some countries by the enormous costs ofadditional spectrum licensing fees. In many countries, 3G networks do not use the sameradio frequencies as 2G, so mobile operators must build entirely new networks andlicense entirely new frequencies; an exception is the United States where carriers operate3G service in the same frequencies as other services. The license fees in some Europeancountries were particularly high, bolstered by government auctions of a limited numberof licenses and sealed bid auctions, and initial excitement over 3Gs potential. Otherdelays were due to the expenses of upgrading equipment for the new systems.China announced in May 2008, that the telecoms sector was re-organized and three 3Gnetworks would be allocated so that the largest mobile operator, China Mobile, wouldretain its GSM customer base. China Unicom would retain its GSM customer base butrelinquish its CDMA2000 customer base, and launch 3G on the globally leadingWCDMA (UMTS) standard. The CDMA2000 customers of China Unicom would go toChina Telecom, which would then launch 3G on the CDMA 1x EV-DO standard. Thismeant that China would have all three main cellular technology 3G standards incommercial use. Finally in January 2009, Ministry of industry and InformationTechnology of China has awarded licenses of all three standards.TD-SCDMA to ChinaMobile, WCDMA to China Unicom and CDMA2000 to China Telecom.Still, several developing countries have not awarded 3G licenses and customers await3G services. China delayed its decisions on 3G for many years, mainly because of theirGovernments delay in establishing well defined standards.[12]The first African use of 3G technology was a 3G videocall made in Johannesburg on theVodacom network in November 2004. The first commercial launch of 3G in Africa wasby EMTEL in Mauritius on the W-CDMA standard. In north African Morocco in lateMarch 2006, a 3G service was provided by the new company Wana.T-Mobile, a major Telecommunication services provider has recently rolled out a list ofover 120 U.S. cities which will be provided with 3G Network coverage in the year 2009.In 2008, India entered into 3G Mobile arena with the launch of 3G enabled Mobileservices by Mahanagar Telephone Nigam Limited (MTNL). MTNL is the first Mobileoperator in India to launch 3G services. 31
    • With so much ease it is surely a desirable possession. But ever since it was launched,every country faced similar problems in introducing it as India does today – itsinstallation being the main one. It requires humungous amounts to set up infrastructurefor 3G technology. Not many telecom companies have the ability to incur such hugeexpenditures to lay up its networks across the nation. India faces this problemcurrently/today. Even if they decide to set up networks, it may not be far reaching andlocated everywhere. Then, how will it serve to be better than laptop enabled broadband?How will it help one stay connected when traveling? And how will it offer continuedfacility at all times and places? Apart from this, licensing a 3G technology remains animpediment. So, it’s not just the expenditure on infrastructure but also on license, whichsums up/amounts to be undesirably mammoth.Talking for the benefit of users, even if one or two of the telecom companiessuccessfully launch 3G technology, its growth and usage will still remain minimal. Thatis because, its strongest feature, video conferencing can be undertaken only when theothers too are using smart phones. If even one of the persons participating in theinteraction does not possess it, it will not be possible to interact with him. This will bethe weakest point as not everybody would want to take up connections of the companiesthat are offering 3G technology. To make things tougher, a 3G enabled handset isdifferent from the other handsets available in the market and it’s more expensive than anormal 2G enabled one. So, to enjoy the benefits of 3G technology, one will first have tocondemn the older handset and then incur huge amounts of losses to buy a smartphone.Not just this, its mobile services are also very highly priced. Internet access is prettyexpensive too. 32
    • SummaryThe Mobile phone which we used today is a result of long course of development .as weknow that “Rome was not built in a day.” Likewise the Mobile phone, its technologyand cellular networking has a glorious course of continuous research work anddevelopment. History of mobile phone include the first Two-way radios (known asmobile rigs) which were used in vehicle to the present scenario in which we have touchscreen phones . Cellular Networking includes the development from the first car phone to theseries which include generations of mobile phones. And the technologies like GSM,CDMA, and 3G.First Generation mobile phone networks includes FDMA technology. Analog systemdesigned for voice only communication. 1G system is almost extinct now.Second Generation (2G) Use GSM and IS-95 CDMA technologies and they introducedfor the first time a mobile phone system that used purely digital technology.Third Generation mobile telephone networks are the latest stage in the development ofwireless communications technology.4G communication system is still under development. It will Combined the technologiesof Wireless local area network (will be introduced soon) and 3G.Then comes the Different digital cellular technologies like GSM, CDMA and OFDMA.GSM (Global System for Mobile communications) is a second generation cellularstandard developed to cater voice services and data delivery using digital modulation.CDMA (Code division multiple access) is a high-speed wireless data and voice networksolution for low-cost, easy to deploy, high-performance services, that address the needsof governments, operators and subscribers.Orthogonal Frequency-Division Multiple Access (OFDMA) is a multi-user version ofthe popular Orthogonal frequency-division multiplexing (OFDM) digital modulationscheme. Multiple accesses are achieved in OFDMA by assigning subsets of subcarriersto individual users as shown in the illustration below. This allows simultaneous low datarate transmission from several users. 33
    • International Mobile Telecommunications-2000 (IMT-2000), better known as 3G or 3rdGeneration, is a family of standards for mobile telecommunications defined by theInternational Telecommunication Union,3G Wireless Systems are the new generation ofsystems that offer high bandwidth and support digital voice along with multimedia andglobal roaming. It remains to be seen how much of the promised features andapplications are actually implemented in today’s economy. 34
    • Conclusion3G cellular wireless technologies provide much greater levels of functionality andflexibility than previous generations. 3G offers improved RF spectral efficiency andhigher bit rates. While the focus for the first 3G systems appears to be voice andlimited data services, 3G is also expected to become a significant Internet accesstechnology. As always, equipment manufacturers that are early to market will gain abig jump on the competition. However, performance of 3G systems will be just asimportant as a competitive differentiator. The only way to achieve both objectiveswill be through a carefully planned and streamlined test and verification strategy.Understanding, these pros and cons, India still remains incompetent to grow in termsof 3G technology. Progress is on and companies have started to introduce 3G inIndia. However, it does only when every communication company decides to takethis up then its success can be identified. For the time being, this service does notseem suitable for all the income groups and remains confined only to high-earningpersons due to its expensive handsets and services. Nonetheless, prices will belowered once competition is increased by more and more companies introducing it.We are waiting for the same to happen. 35