NATIONAL COLLEGE OF SCIENCE AND TECHNOLOGY Amafel Bldg. Aguinaldo Highway Dasmariñas City, Cavite ASSIGNMENT 1 CELLULAR TECHNOLOGYBani, Arviclyn C. October 03, 2011Communications 1/ BSECE 41A1 Score: Engr. Grace Ramones Instructor
The history of mobile phones records the development of interconnection between the publicswitched telephone systems to radio transceivers. From the earliest days of transmitting speechby radio, connection of the radio system to the telephone network had obvious benefits ofeliminating the wires. Early systems used bulky, high power consuming equipment andsupported only a few conversations at a time, with required manual set-up of theinterconnection. Today cellular technology and microprocessor control systems allow automaticand pervasive use of mobile phones for voice and data.The transmission of speech by radio has a long and varied history going back to ReginaldFessendens invention and shore-to-ship demonstration of radio telephony, through the SecondWorld War with military use of radio telephony links. Mobile telephones for automobiles becameavailable from some telephone companies in the 1950s. Hand-held radio transceivers havebeen available since the Second World War. Mobile phone history is often divided intogenerations (first, second, third and so on) to mark significant step changes in capabilities asthe technology improved over the years.First generation: Cellular networksThe technological development that distinguished the First Generation of mobile phones fromthe previous generation was the use of multiple cell sites, and the ability to transfer calls fromone site to the next as the user travelled between cells during a conversation. The firstcommercially automated cellular network (the 1G generation) was launched in Japan by NTT in1979. The initial launch network covered the full metropolitan area of Tokyos over 20 millioninhabitants with a cellular network of 23 base stations. Within five years, the NTT network hadbeen expanded to cover the whole population of Japan and became the first nation-wide 1Gnetwork.
Analog Motorola DynaTAC 8000X Advanced Mobile Phone System mobile phone as of 1983The next 1G network to launch was the Nordic Mobile Telephone (NMT) system in Denmark,Finland, Norway and Sweden in 1981. NMT was the first mobile phone network to featureinternational roaming. The Swedish electrical engineer Östen Mäkitalo started work on thisvision in 1966, and is considered to be the father of the NMT system, and by some the father ofthe cellular phone itself, since he and two colleagues hold a patent from 1971 on a cellularsystem with handover and roaming. The NMT installations were based on the EricssonAXE digital exchange nodes.Several other countries also launched 1G networks in the early 1980s including the UK, Mexicoand Canada. A two year trial started in 1981 in Baltimore and Washington DC with 150 usersand 300 Motorola DynaTAC pre-production phones. This took place on a seven tower cellularnetwork that covered the area. The DC area trial turned into a commercial services in about1983 with fixed cellular car phones also built by Motorola. They later added the 8000X to theirCellular offerings. A similar trial and commercial launch also took place in Chicago by Ameritechin 1983 using the famous first hand-held mobile phone Motorola DynaTAC.AT&Ts 1971 proposal for Advanced Mobile Phone System (AMPS) was approved by the FCCin 1982 and frequencies were allocated in the 824–894 MHz band. Analog AMPS wassuperseded by Digital AMPS in 1990.In 1984, Bell Labs developed modern commercial cellular technology (based, to a large extent,on the Gladden, Parelman Patent), which employed multiple, centrally controlled base stations(cell sites), each providing service to a small cell area. The sites were set up so that cellspartially overlapped and different base stations operated using the same frequencies with littleor no interference.
Vodafone made the UKs first mobile call at a few minutes past midnight on January 1 1985.The technology in these early networks was pushed to the limit to accommodate increasingusage. The base stations and the mobile phones utilized variable transmission power, whichallowed range and cell size to vary. As the system expanded and neared capacity, the ability toreduce transmission power allowed new cells to be added, resulting in more, smaller cells andthus more capacity. The evidence of this growth can still be seen in the many older, tall cell sitetowers with no antennae on the upper parts of their towers. These sites originally created largecells, and so had their antennae mounted atop high towers; the towers were designed so that asthe system expanded—and cell sizes shrank—the antennae could be lowered on their originalmasts to reduce range.Second generation: Digital networksTwo 1991 GSM mobile phones with several AC adaptersIn the 1990s, the second generation (2G) mobile phone systems emerged, primarily using theGSM standard. These differed from the previous generation by using digital instead of analogtransmission, and also fast out-of-band phone-to-network signaling. The rise in mobile phoneusage as a result of 2G was explosive and this era also saw the advent of prepaid mobilephonesIn 1991 the first GSM network (Radiolinja) launched in Finland. In general the frequencies usedby 2G systems in Europe were higher than those in America, though with some overlap. Forexample, the 900 MHz frequency range was used for both 1G and 2G systems in Europe, sothe 1G systems were rapidly closed down to make space for the 2G systems. In America the IS-54 standard was deployed in the same band as AMPS and displaced some of the existinganalog channels.
Coinciding with the introduction of 2G systems was a trend away from the larger "brick" phonestoward tiny 100–200g hand-held devices. This change was possible not only throughtechnological improvements such as more advanced batteries and more energy-efficientelectronics, but also because of the higher density of cell sites to accommodate increasingusage. The latter meant that the average distance transmission from phone to the base stationshortened, leading to increased battery life whilst on the move.Personal Handy-phone System mobiles and modems used in Japan around 1997–2003The second generation introduced a new variant of communication called SMS or textmessaging. It was initially available only on GSM networks but spread eventually on all digitalnetworks. The first machine-generated SMS message was sent in the UK on 3 December 1992followed in 1993 by the first person-to-person SMS sent in Finland. The advent of prepaidservices in the late 1990s soon made SMS the communication method of choice amongst theyoung, a trend which spread across all ages.2G also introduced the ability to access media content on mobile phones. In 1998 the firstdownloadable content sold to mobile phones was the ring tone, launched by Finlands Radiolinja(now Elisa). Advertising on the mobile phone first appeared in Finland when a free daily SMSnews headline service was launched in 2000, sponsored by advertising.Mobile payments were trialled in 1998 in Finland and Sweden where a mobile phone was usedto pay for a Coca Cola vending machine and car parking. Commercial launches followed in1999 in Norway. The first commercial payment system to mimic banks and credit cards waslaunched in the Philippines in 1999 simultaneously by mobile operators Globe and Smart.The first full internet service on mobile phones was introduced by NTT DoCoMo in Japan in1999.Third generation: High speed IP data networks and mobile broadbandAs the use of 2G phones became more widespread and people began to utilize mobile phonesin their daily lives, it became clear that demand for data services (such as access to theinternet) was growing. Furthermore, experience from fixed broadband services showed therewould also be an ever increasing demand for greater data speeds. The 2G technology wasnowhere near up to the job, so the industry began to work on the next generation of technology
known as 3G. The main technological difference that distinguishes 3G technology from 2Gtechnology is the use of packet switching rather than circuit switching for data transmission. Inaddition, the standardization process focused on requirements more than technology (2 Mbit/smaximum data rate indoors, 384 kbit/s outdoors, for example).Inevitably this led to many competing standards with different contenders pushing their owntechnologies, and the vision of a single unified worldwide standard looked far from reality. Thestandard 2G CDMA networks became 3G compliant with the adoption of Revision A to EV-DO,which made several additions to the protocol whilst retaining backwards compatibility: the introduction of several new forward link data rates that increase the maximum burst rate from 2.45 Mbit/s to 3.1 Mbit/s. protocols that would decrease connection establishment time. the ability for more than one mobile to share the same time slot. the introduction of QoS flags.All these were put in place to allow for low latency, low bit rate communications such as VoIP.The first pre-commercial trial network with 3G was launched by NTT DoCoMo in Japan in theTokyo region in May 2001. NTT DoCoMo launched the first commercial 3G network on October1, 2001, using the WCDMA technology. In 2002 the first 3G networks on the rival CDMA20001xEV-DO technology were launched by SK Telecom and KTF in South Korea, and Monet in theUSA. Monet has since gone bankrupt. By the end of 2002, the second WCDMA network waslaunched in Japan by Vodafone KK (now Softbank). European launches of 3G were in Italy andthe UK by the Three/Hutchison group, on WCDMA. 2003 saw a further 8 commercial launchesof 3G, six more on WCDMA and two more on the EV-DO standard.During the development of 3G systems, 2.5G systems such as CDMA2000 1x and GPRS weredeveloped as extensions to existing 2G networks. These provide some of the features of 3Gwithout fulfilling the promised high data rates or full range of multimedia services. CDMA2000-1X delivers theoretical maximum data speeds of up to 307 kbit/s. Just beyond these is theEDGE system which in theory covers the requirements for 3G system, but is so narrowly abovethese that any practical system would be sure to fall short.The high connection speeds of 3G technology enabled a transformation in the industry: for thefirst time, media streaming of radio (and even television) content to 3G handsets becamepossible, with companies such as RealNetworks  and Disney  among the early pioneers inthis type of offering.In the mid 2000s an evolution of 3G technology begun to be implemented, namely High-SpeedDownlink Packet Access (HSDPA). It is an enhanced 3G (third generation) mobile telephony
communications protocol in the High-Speed Packet Access (HSPA) family, also coined 3.5G,3G+ or turbo 3G, which allows networks based on Universal Mobile TelecommunicationsSystem (UMTS) to have higher data transfer speeds and capacity. Current HSDPAdeployments support down-link speeds of 1.8, 3.6, 7.2 and 14.0 Mbit/s. Further speed increasesare available with HSPA+, which provides speeds of up to 42 Mbit/s downlink and 84 Mbit/s withRelease 9 of the 3GPP standards.By the end of 2007 there were 295 million subscribers on 3G networks worldwide, whichreflected 9% of the total worldwide subscriber base. About two thirds of these were on theWCDMA standard and one third on the EV-DO standard. The 3G telecoms services generatedover 120 Billion dollars of revenues during 2007 and at many markets the majority of newphones activated were 3G phones. In Japan and South Korea the market no longer suppliesphones of the second generation.Although mobile phones had long had the ability to access data networks such as the Internet, itwas not until the widespread availability of good quality 3G coverage in the mid 2000s thatspecialized devices appeared to access the mobile internet. The first such devices, known as"dongles", plugged directly into a computer through the USB port. Another new class of deviceappeared subsequently, the so-called "compact wireless router" such as the Novatel MiFi, whichmakes 3G internet connectivity available to multiple computers simultaneously over Wi-Fi,rather than just to a single computer via a USB plug-in.Such devices became especially popular for use with laptop computers due to the addedportability they bestow. Consequently, some computer manufacturers started to embed themobile data function directly into the laptop so a dongle or MiFi wasnt needed. Instead, the SIMcard could be inserted directly into the device itself to access the mobile data services. Such3G-capable laptops became commonly known as "netbooks". Other types of data-awaredevices followed in the netbooks footsteps. By the beginning of 2010, E-readers, such as theAmazon Kindle and the Nook from Barnes & Noble, had already become available withembedded wireless internet, and Apple Computer had announced plans for embedded wirelessinternet on its iPad tablet devices beginning that Fall.Fourth generation: All-IP networksBy 2009, it had become clear that, at some point, 3G networks would be overwhelmed by thegrowth of bandwidth-intensive applications like streaming media. Consequently, the industrybegan looking to data-optimized 4th-generation technologies, with the promise of speedimprovements up to 10-fold over existing 3G technologies. The first two commercially available
technologies billed as 4G were the WiMAX standard (offered in the U.S. by Sprint) and the LTEstandard, first offered in Scandinavia by TeliaSonera.One of the main ways in which 4G differed technologically from 3G was in its elimination ofcircuit switching, instead employing an all-IP network. Thus, 4G ushered in a treatment of voicecalls just like any other type of streaming audio media, utilizing packet switching over internet,LAN or WAN networks via VoIP
MULTIPLE ACCESSFrequency reuseThe increased capacity in a cellular network, comparing to a network with a single transmitter,comes from the fact that the same radio frequency can be reused in a different area for acompletely different transmission. If there is a single plain transmitter, only one transmissioncan be used on any given frequency. Unfortunately, there is inevitably some level ofinterference from the signal from the other cells which use the same frequency. This meansthat, in a standard FDMA system, there must be at least a one cell gap between cells whichreuse the same frequency.The frequency reuse factor is the rate at which the same frequency can be used in the network.It is 1/n where n is the number of cells which cannot use a frequency for transmission.Code division multiple access based systems use a wider frequency band to achieve the samerate of transmission as FDMA, but this is compensated for by the ability to use a frequencyreuse factor of 1. In other words, every cell uses the same frequency and the different systemsare separated by codes rather than frequencies.Depending on the size of the city, a taxi system may not have any frequency reuse in its owncity, but certainly in other nearby cities, the same frequency can be used. In a big city, on theother hand, frequency reuse could certainly be in use.Frequency Division Multiple Access or FDMA is a channel access method used in multiple-access protocols as a channelization protocol. FDMA gives users an individual allocation of oneor several frequency bands, or channels. It is particularly commonplace in satellitecommunication. FDMA, like other Multiple Access systems, coordinates access betweenmultiple users. Alternatives include TDMA, CDMA, or SDMA. These protocols are utilizeddifferently, at different levels of the theoreticalOSI model.Disadvantage: Crosstalk may cause interference among frequencies and disrupt thetransmission.FREQUENCY DIVISION MULTIPLE ACCESSFDMA is distinct from frequency division duplexing (FDD). While FDMA allows multiple userssimultaneous access to a transmission system, FDD refers to how the radio channel is sharedbetween the uplink and downlink (for instance, the traffic going back and forth between amobile-phone and a mobile phone base station). Frequency-division multiplexing (FDM) is alsodistinct from FDMA. FDM is a physical layer technique that combines and transmits low-
bandwidth channels through a high-bandwidth channel. FDMA, on the other hand, is an accessmethod in the data link layer.FDMA also supports demand assignment in addition to fixed assignment. Demandassignment allows all users apparently continuous access of the radio spectrum by assigningcarrier frequencies on a temporary basis using a statistical assignment process. The firstFDMA demand-assignment system for satellite was developed byCOMSAT for use onthe Intelsat series IVA and V satellites.There are two main techniques: Multi-channel per-carrier (MCPC) Single-channel per-carrier (SCPC)Time division multiple access (TDMA) is a channel access method for shared mediumnetworks. It allows several users to share the same frequency channel by dividing the signalinto different time slots. The users transmit in rapid succession, one after the other, each usingits own time slot. This allows multiple stations to share the same transmission medium (e.g.radio frequency channel) while using only a part of its channel capacity. TDMA is used in thedigital 2G cellular systems such as Global System for Mobile Communications (GSM), IS-136, Personal Digital Cellular (PDC) and iDEN, and in the Digital Enhanced CordlessTelecommunications (DECT) standard for portable phones. It is also used extensivelyin satellite systems, combat-net radio systems, and PON networks for upstream traffic frompremises to the operator. For usage of Dynamic TDMA packet mode communication.TDMA is a type of Time-division multiplexing, with the special point that instead of havingone transmitter connected to one receiver, there are multiple transmitters. In the case ofthe uplink from a mobile phone to abase station this becomes particularly difficult because themobile phone can move around and vary the timing advance required to make its transmissionmatch the gap in transmission from its peers.TDMA in 2G systemsMost 2G cellular systems, with the notable exception of IS-95, are based on TDMA. GSM, D-AMPS, PDC, iDEN, and PHS are examples of TDMA cellular systems. GSM combines TDMAwith Frequency Hopping and wideband transmission to minimize common types of interference.In the GSM system, the synchronization of the mobile phones is achieved by sending timingadvance commands from the base station which instructs the mobile phone to transmit earlierand by how much. This compensates for the propagation delay resulting from the light speed
velocity of radio waves. The mobile phone is not allowed to transmit for its entire time slot, butthere is a guard interval at the end of each time slot. As the transmission moves into the guardperiod, the mobile network adjusts the timing advance to synchronize the transmission.Initial synchronization of a phone requires even more care. Before a mobile transmits there is noway to actually know the offset required. For this reason, an entire time slot has to be dedicatedto mobiles attempting to contact the network (known as the RACH in GSM). The mobileattempts to broadcast at the beginning of the time slot, as received from the network. If themobile is located next to the base station, there will be no time delay and this will succeed. If,however, the mobile phone is at just less than 35 km from the base station, the time delay willmean the mobiles broadcast arrives at the very end of the time slot. In that case, the mobile willbe instructed to broadcast its messages starting nearly a whole time slot earlier than would beexpected otherwise. Finally, if the mobile is beyond the 35 km cell range in GSM, then theRACH will arrive in a neighbouring time slot and be ignored. It is this feature, rather thanlimitations of power, that limits the range of a GSM cell to 35 km when no special extensiontechniques are used. By changing the synchronization between the uplink and downlink at thebase station, however, this limitation can be overcome.3G systemsAlthough most major 3G systems are primarily based upon CDMA , time divisionduplexing (TDD), packet scheduling (dynamic TDMA) and packet oriented multiple accessschemes are available in 3G form, combined with CDMA to take advantage of the benefits ofboth technologies.While the most popular form of the UMTS 3G system uses CDMA and frequency divisionduplexing (FDD) instead of TDMA, TDMA is combined with CDMA and Time Division Duplexingin two standard UMTS UTRACode division multiple access (CDMA) is a channel access method used by various radiocommunication technologies. It should not be confused with the mobile phonestandards called cdmaOne, CDMA2000 (the 3G evolution of cdmaOne) and WCDMA (the 3Gstandard used by GSM carriers), which are often referred to as simply CDMA, and use CDMAas an underlying channel access method.One of the basic concepts in data communication is the idea of allowing several transmitters tosend information simultaneously over a single communication channel. This allows severalusers to share a band of frequencies (see bandwidth). This concept is called multiple access.CDMA employs spread-spectrum technology and a special coding scheme (where eachtransmitter is assigned a code) to allow multiple users to be multiplexed over the same physical
channel. By contrast, time division multiple access (TDMA) divides access bytime,while frequency-division multiple access (FDMA) divides it by frequency. CDMA is a formof spread-spectrum signalling, since the modulated coded signal has a much higher databandwidth than the data being communicated.An analogy to the problem of multiple access is a room (channel) in which people wish to talk toeach other simultaneously. To avoid confusion, people could take turns speaking (time division),speak at different pitches (frequency division), or speak in different languages (code division).CDMA is analogous to the last example where people speaking the same language canunderstand each other, but other languages are perceived as noise and rejected. Similarly, inradio CDMA, each group of users is given a shared code. Many codes occupy the samechannel, but only users associated with a particular code can communicate. The technology ofcode division multiple access channels has long been known. In the USSR, the first workdevoted to this subject was published in 1935 by professor D.V. Aggeev in the "CDMA". It wasshown that through the use of linear methods, there are three types of signal separation:frequency, time and compensatory. The technology of CDMA was used in 1957, when theyoung military radio engineer Leonid Kupriyanovich in Moscow, made an experimental model ofa wearable automatic mobile phone, called LK-1 by him, with a base station. LK-1 has a weightof 3 kg, 20-30 km operating distance, and 20-30 hours of battery life ("Nauka i zhizn", 8, 1957,p. 49, "Yuniy technik", 7, 1957, p. 43-44). The base station, as described by the author, couldserve several customers. In 1958, Kupriyanovich made the new experimental "pocket" model ofmobile phone. This phone weighs 0,5 kg. To serve more customers, Kupriyanovich proposedthe device, named by him as correllator. ("Nauka i zhizn", 10, 1958, p.66, "Technika-molodezhi",2, 1959, 18-19) In 1958, the USSR also started the development of the "Altay" national civilmobile phone service for cars, based on the Soviet MRT-1327 standard. The main developersof the Altay system were VNIIS (Voronezh Science Research Institute of Communications)andGSPI (State Specialized Project Institute). In 1963 this service started in Moscow and in 1970Altay service was used in 30 USSR cities.Space-Division Multiple Access (SDMA) is a channel access method based on creatingparallel spatial pipes next to higher capacity pipes through spatial multiplexing and/or diversity,by which it is able to offer superior performance in radio multiple access communicationsystems. In traditional mobile cellular network systems, the base station has no information onthe position of the mobile units within the cell and radiates the signal in all directions within thecell in order to provide radio coverage. This results in wasting power on transmissions whenthere are no mobile units to reach, in addition to causing interference for adjacent cells using the
same frequency, so calledco-channel cells. Likewise, in reception, the antenna receives signalscoming from all directions including noise and interference signals. By using smartantenna technology and differing spatial locations of mobile units within the cell, space-divisionmultiple access techniques offer attractive performance enhancements. The radiation pattern ofthe base station, both in transmission and reception, is adapted to each user to obtain highestgain in the direction of that user. This is often done using phased arraytechniques.In GSM cellular networks, the base station is aware of the mobile phones position by use of atechnique called "timing advance" (TA). The Base Transceiver Station (BTS) can determine howdistant the Mobile Station (MS) is by interpreting the reported TA. This information, along withother parameters, can then be used to power down the BTS or MS, if a power control feature isimplemented in the network. The power control in either BTS or MS is implemented in mostmodern networks, especially on the MS, as this ensures a better battery life for the MS and thusa better user experience (in that the need to charge the battery becomes less frequent). This iswhy it may actually be safer to have a BTS close to you as your MS will be powered down asmuch as possible. For example, there is more power being transmitted from the MS than whatyou would receive from the BTS even if you are 6 m away from a mast. However, thisestimation might not consider all the MSs that a particular BTS is supporting with EM radiationat any given time.Advanced Mobile Phone System (AMPS) was an analog mobile phone system standarddeveloped byBell Labs, and officially introduced in the Americas in 1983, Israel in 1986,and Australia in 1987. It was the primary analog mobile phone system in North America (andother locales) through the 1980s and into the 2000s. As of February 18, 2008, carriers in theUnited States were no longer required to support AMPS and companies such as AT&T andVerizon have discontinued this service permanently. AMPS was discontinued in Australia inSeptember 2000