NATIONAL COLLEGE OF SCIENCE AND TECHNOLOGY Amafel Bldg. Aguinaldo Highway Dasmariñas City, Cavite ASSIGNMENT 1 CELLULAR TECHNOLOGYOlaño, Reymart M. October 03, 2011Communications 1/ BSECE 41A1 Score: Engr. Grace Ramones Instructor
Cellular technology has changed the world. You can even successfully make the argument thatthis technology is more important than the Internet itself because it enables us to take the Internetanywhere. Since the invention of the Internet, the ability to take it anywhere has also changedthe world. The world has become one large mobile society. The significance of globalcommunications is such that we now know news instantaneously as it happens. Being mobileenables all of us to be connected and makes the world seem like a much smaller place. Howdoes this technology work?Cellular technology is actually a series of radio network served by a fixed location transceiverand known as a cell site.When these cells are connected together, they provide what we know as radio coverage over alarge geographic area. While knowing how this technology works is interesting (or not), thesignificance of it is how it affects and impacts our daily lives. Our lives are impacted in some ofthe following ways: texts, phone calls, videos, Internet, GPS, entertainment, learning, knowledgeand all of these falls under the broader heading of communications. How we communicate andwhat we communicate is what has changed our lives as we know it. For the person who is 45years old and older, you have probably lived through all of these changes and understand that theworld is progressively, substantially different that when you were a kid. For those reading thisthat is 20 or younger, the world most definitely was not always this way.The first major impact of this technology is the inexpensive availability of this technology toeveryone in the form of cell phones. Ownership of cellular devices range from the idle rich whohave latest version of whatever new gimmick is on the market and costs a small fortune to ahomeless individual with lower than low or non-existent credit scores. The point is that anyonecan own a cellular device. If you are homeless, you will obviously not be able to afford themake and model the rich own. However, you can still own the cheapest device out there and bepart of the mobile society.
Cellular Technology: The Impact on Modern Day LifeOne of the impacts of this relatively new technology is that an entire generation hascommunicated through texting, the typing and sending of brief messages over their cell phones.A new type of abbreviated language has even been created to keep the labor of thiscommunication brief.The most logical question about texting comes from the older generation and goes like this: whydon’t you just call the person instead of sending them a message? Phone calls are not alwaysconvenient. Some of the places where a phone call might cause a major interruption ordistraction would be in a meeting at work, in a classroom setting, in a church service or in themovies. However, a text is quiet and simple and gets the message across to the recipient. Youngpeople texts like older people breathe.The older people still primarily communicate through phone calls. However, the majoradvantage of cell phones is that you are now freed up to eliminate your land line because youreally don’t need both of them. With their cell phone they can now call anyone from anywhere.They are on the go like never before and their calls go with them.Another wonder of cellular technology is the ability to watch videos on your cell phone. Videosfirst gained prominence in the very early 1980s with the advent of MTV. The earliest videoswere music videos, but since have evolved into everything from home movies, major studiomotion picture releases and television programs. Probably the largest carrier of videos in avehicle called You Tube. This vehicle is a web site that is accessed through the Internet. Thanksto the ability to communicate through cell phones, we as a society are able to carry our videoswith us to amuse, entertain or inform.Arguably, the most significant aspect of cellular technology is the ability to carry the Internetwith us to any location where cell coverage is available and in the United States, that is amajority of the country with the exception of some rural areas. Think of the Internet as your own
pack and carry version of the most sophisticated public library that you have ever visited. TheInternet allows you to find practically anything that is out there in the form of knowledge. TheInternet facilitates most learning about any topic known to man. Colleges and universities offerclasses over the Internet. You do not even need to step into a classroom to get certain degrees.A mobile Internet, enabled by cellular technology, is arguably the greatest invention of the lastfifty years.The Major Advantages of Cellular TechnologyApps for mobile phones is one of the major advantages to being mobile and on the go, especiallyto places we are unfamiliar with, is what is known as the GPS, or global positioning system.Some of the more sophisticated cellular devices come with a GPS option, so you can always findyour way. Today’s GPS is like road maps used to be without all the clutter and information thatyou don’t need.Cellular technology is entertaining. Though you can tell a joke through texting or live during aphone call, the other possibilities are endless: music, music videos, movies, photographs, videogames, word games and television programs are just a few of the ways that you can keepyourself entertained. They key to this technology is how long your batter life is and keepingyour cellular device charged.None of this would have been possible without cellular technology, which is practicallysynonymous with being on the move. Being on the move is total freedom, not being tied to aspecific location for anything. In the past, vocations and careers stated that we sometimes had tostay in one location and for some, that is still the case. But most of us can work, be entertainedand socialize from the road thanks to cellular devices.
HistoryRadiophones have a long and varied history going back to Reginald Fessendens invention andshore-to-ship demonstration of radio telephony, through the Second World War with military useof radio telephony links and civil services in the 1950s.The first mobile telephone call made from a car occurred in St. Louis, Missouri, USA on June17, 1946, using the Bell Systems Mobile Telephone Service. The equipment weighed 80 pounds(36 kg), and the AT&T service, basically a massive party line, cost US$30 per month (equal to$337.33 today) plus 30–40 cents per local call, equal to $3.37 to $4.5 today.In 1956, the world’s first partly automatic car phone system, Mobile System A (MTA), waslaunched in Sweden. MTA phones were composed of vacuum tubes and relays, and had a weightof 40 kg. In 1962, a more modern version called Mobile System B (MTB) was launched, whichwas a push-button telephone, and which used transistors to enhance the telephone’s callingcapacity and improve its operational reliability, thereby reducing the weight of the apparatus to10 kg. In 1971, the MTD version was launched, opening for several different brands ofequipment and gaining commercial success.Martin Cooper, a Motorola researcher and executive is considered to be the inventor of the firstpractical mobile phone for handheld use in a non-vehicle setting, after a long race against BellLabs for the first portable mobile phone. Using a modern, if somewhat heavy portable handset,Cooper made the first call on a handheld mobile phone on April 3, 1973 to his rival, Dr. Joel S.Engel of Bell Labs.The first commercially automated cellular network (the 1G) was launched in Japan by NTT in1979, initially in the metropolitan area of Tokyo. Within five years, the NTT network had beenexpanded to cover the whole population of Japan and became the first nationwide 1G network. In1981, this was followed by the simultaneous launch of the Nordic Mobile Telephone (NMT)system in Denmark, Finland, Norway and Sweden. NMT was the first mobile phone networkfeaturing international roaming. The first 1G network launched in the USA was Chicago-basedAmeritech in 1983 using the Motorola DynaTAC mobile phone. Several countries then followedin the early-to-mid 1980s including the UK, Mexico and Canada.The first "modern" network technology on digital 2G (second generation) cellular technologywas launched by Radiolinja (now part of Elisa Group) in 1991 in Finland on the GSM standard,which also marked the introduction of competition in mobile telecoms when Radiolinjachallenged incumbent Telecom Finland (now part of TeliaSonera) who ran a 1G NMT network.In 2001, the launch of 3G (Third Generation) was again in Japan by NTT DoCoMo on theWCDMA standard.[
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 means that,in a standard FDMA system, there must be at least a one cell gap between cells which reuse thesame frequency.The frequency reuse factor is the rate at which the same frequency can be used in the network. Itis 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 the transmission.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 signal intodifferent time slots. The users transmit in rapid succession, one after the other, each using itsown time slot. This allows multiple stations to share the same transmission medium (e.g. radiofrequency 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 speedvelocity 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 DivisionDuplexing in 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 CDMA asan 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 several usersto share a band of frequencies (see bandwidth). This concept is called multiple access. CDMAemploys spread-spectrum technology and a special coding scheme (where each transmitter isassigned a code) to allow multiple users to be multiplexed over the same physical channel. Bycontrast, time division multiple access (TDMA) divides access bytime, while frequency-divisionmultiple access (FDMA) divides it by frequency. CDMA is a form of spread-spectrum signalling,since the modulated 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 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 same channel,but only users associated with a particular code can communicate. The technology of codedivision multiple access channels has long been known. In the USSR, the first work devoted tothis subject was published in 1935 by professor D.V. Aggeev in the "CDMA". It was shown thatthrough the use of linear methods, there are three types of signal separation: frequency, time andcompensatory. The technology of CDMA was used in 1957, when the young military radioengineer Leonid Kupriyanovich in Moscow, made an experimental model of a wearableautomatic mobile phone, called LK-1 by him, with a base station. LK-1 has a weight of 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, could serveseveral customers. In 1958, Kupriyanovich made the new experimental "pocket" model ofmobile phone. This phone weighs 0,5 kg. To serve more customers, Kupriyanovich proposed thedevice, 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 developers ofthe Altay system were VNIIS (Voronezh Science Research Institute of Communications)and
GSPI (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 creating parallelspatial pipes next to higher capacity pipes through spatial multiplexing and/or diversity, bywhich it is able to offer superior performance in radio multiple access communication systems.In traditional mobile cellular network systems, the base station has no information on theposition of the mobile units within the cell and radiates the signal in all directions within the cellin order to provide radio coverage. This results in wasting power on transmissions when there areno mobile units to reach, in addition to causing interference for adjacent cells using the samefrequency, so calledco-channel cells. Likewise, in reception, the antenna receives signals comingfrom all directions including noise and interference signals. By using smart antenna technologyand differing spatial locations of mobile units within the cell, space-division multiple accesstechniques offer attractive performance enhancements. The radiation pattern of the base station,both in transmission and reception, is adapted to each user to obtain highest gain in the directionof 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 thus abetter user experience (in that the need to charge the battery becomes less frequent). This is whyit may actually be safer to have a BTS close to you as your MS will be powered down as muchas possible. For example, there is more power being transmitted from the MS than what youwould receive from the BTS even if you are 6 m away from a mast. However, this estimationmight not consider all the MSs that a particular BTS is supporting with EM radiation at anygiven 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