Cellphones and Digital Networks

Cell ph oneness(a)s ex imagine been around for more or less 15 years and atomic effect 18 at one condemnation e realwhere you savor. Over a quarter of Americans and a half of Europeans own carrel call backs and the numbers make believe been increasing exponenti bothy. With the continuing increase in technology boothular earphone phones wealthy person become smaller, cheaper, and thanks to the draw from elongate to formal the calls be frequently cle arr. They offer a great measurement of convenience, and can be very(prenominal)(prenominal) economically for the busy businessman on the go. Advancements in carrell phones are always macrocosm made, giving a clearer sound and lighter feel, as well as a longer life.The cell phone persistence has been one of the fastest growing in the world. The electronics are fairly plain, tho they are so small that they are truly and engineering marvel. This report card provide discuss in depth the mevery various component s of the comely cell phone, and whistle round how it converts your voice into something that can be move finished a digital network. The paper will excessively look at how the inner workings allow for a phone to act as a micro computing machine, with Internet glide path, address books, and hitherto games.Finally, it will reexamine the many exciting ideas for this growing market and look to the future of the diligence, and how the industry plans on overcoming various limiting factors. Alexander Graham Bell invented the mobilize in 1876, 18 years later Guglielmo Marconi created the first radio. It was only earthy that these two great technologies would eventually be combined to create the cellular craze. In the 80s few batch practiced radiophones, these phones were the precursor to cellular, just they had some(prenominal) limiting factors preventing them from every becoming a major part of effortless society.In the radio telephone system, there was one central feeler hover per major city, and no more than 25 pedigrees functional on that rise. Each phone takeed a powerful transmitter, puffy enough to transmit 40 or 50 miles. It as well meant that not many people could function radiotelephones due to the lack of channels. With the current cellular system any none adjacent cell can use the same frequency, so the sum up of phones that can be use are nearly limitless. These cells also mean that each phone does not need a strong transmitter, so the phone can be a lot smaller.With the innovation of digital phones, many great features are now avail fitted, such as caller id, Internet access, and several some other(a) parvenue features. It also meant that the phone would need a microprocessor to convert from analog to digital, this conglomerate the circuitry, but left it with new technology available the industry was able to make the phone as small as feasible. The only restriction in size became the user-input windings, and the screen s ize. Usefulness of the Digital Cell squallThe digital cellular phone offers many advantages to todays society. The comforts that it offers over simply not having one are obvious and they part from person to person. But there are many advantages over other types of phones as well. The cellular phone not only allows people to slip away with others while they are on the go, but it also offers many other features to help people. With the services that digital provides, people can access e-mail and find information almost anywhere in the world for a reasonable fee.In the future, as the integration of phones and computers grow, people will be able to access tutorials in the field, and use them to communicate with specialists saving a great amount of time for many researchers. Today digital cell phones, such as the one shown in appurtenance C range of a function 1, can process millions of calculations per second in order to compress and limber up the voice stream. In order to do thi s each phone is render with a circuit poster that contains many diametrical chips. The circuit board of a common phone is shown in Appendix C contrive 2.Two chips described earlier are the Analog-to-Digital and Digital-to-Analog conversion chips that translate the crush audio signal from analog to digital and the incoming signal from digital back to analog. There is also a Digital Signal central touch on unit that is highly customized processor designed to make out signal manipulation calculations at high speed. The microprocessor chequers the keyboard and display and deals with command and control signaling with the establish station, it also coordinates the rest of the functions on the board.This microprocessor is as powerful as the super computer of the 70s that took up whole rooms, but is now the size of a finger. By using its arithmetic/logic unit or ALU it can perform all mathematical operation that run many of today features in phones. It is also responsible for the transfer of data throughout the phone. It will also make decisions and whence run a new set of instructions. In Appendix C attribute 3 a very simple microprocessor is shown. Cell phones use microprocessors that are much more complex, but the use the same idea.The ROM and flash memory chips provide storage for the phones in operation(p) system and customizable features, such as the directory and various simple games. (Appendix C figure 4) The RF and power section handles power management and recharging, and also deals with the hundreds of FM channels. Finally, the Radio oftenness amplifiers handle signals in and out of the antenna. The Radio Frequency amplifier is the same device as you would find in your cars radio. The display has fully grown considerably in size as the number of features offered by cell phones has increased.Most phones currently available offer built-in phone directories, calculators and even games. It some new products that will be discussed later, cell phon e rejoinder as PDAs offering very commodious screen and offer all of the benefit you would find in todays hand held computers. The display is a fluent crystal display (LCD). It is made of thousands of tiny crystals with two possible colors. They chip in recently announced that they will be offering color screens on some new phones that work like the display of a laptop computer computer.Very small speakers and microphones, about the size of a dime, amplify the analog waves. These devices are just like that of a portable radio and the microphones used on television sing shows. They are both wired to the microprocessor. In order for digital cell phones to take advantage of the added capacitor and clearer quality, they essential convert your voice into binary information. This means that it must break it downcast to 1s and 0s. The reason that this is so advantageous is that unlike analog, digital is either on or off, 1 or 0, instead of oscillating between the two.For the conve rsion, the device must first record an analog wave, such as the one in Appendix B figure 1. To create the highest fidelity possible, it records number to represent the wave, instead of the wave itself as represented in Appendix B figure 2. The cell phones analog-to-digital converter, a device that is also imbed in a CD player, does this process. On the other end a decompose digital-to-analog converter is used for playback. The quality of transfer depends on the take rate, that controls how many samples are taken per second, and the sampling precision.The precision controls how many different levels are possible in the sample. The better these two are the clearer the sound, but it takes a higher speed processor and requires a greater amount of data transfer. In Appendix B the benefits are shown in figure 3. Most common digital cellular systems use Frequency shift Keying to send data back and forth. This system uses one frequency for 1s and another(prenominal) for 0s and rapidly s witching between the two. This requires optimal modulation and encoding schemes for recording, compressing, sending, and then decoding without discharge of quality.Because of this digital phones contain an amazing amount of processing power. The cellular network is web of towers covering areas, generally thought of as hexagonal cells as shown in APPENDIX A Figure 1. The mastermind of the cellular system is because cell phones and base stations use low-power transmitters, so the same frequencies can be reused in non-adjacent cells. Each cell is about 10 square miles and has a base station that consists of a tower and a small building containing the radio equipment. As more people join the cellular world, companies are quickly adding more towers to accommodate them. each digital carrier is designate different frequencies, an average carrier whitethorn get about 2400 frequencies per city, and this number is about three times the amount as analog. The reason that more channels are av ailable is because digital data can be compressed and manipulated much easier than analog. Each tower uses one seventh of the available frequencies, so none of the surrounding 6 towers interfere. The cell phone uses two frequencies per call, called a duplex channel. The duplex channel allows one channel to be used for listening and the other for talking, so unlike a CB or walkie-talkie, both people can talk at the same time.This system currently allows for about 168 people to talk in each cell, for each system. The cellular approach requires a large number of base stations in a city of any size, but because so many people are using cell phones, costs remain low per user. Every cell phone has a special code associated with it, called an electronic serial number (ESN). It is a strange 32-bit number programmed into the phone when it is manufactured. When the phone is activated another five digit code called a system identification code (SID), a fantastic 5 digit number that is assign ed to each carrier by the FCC, is imprinted in the phones memory.When you first power up a cell phone, it checks a control channel to find the SID. If the phone cannot find any control channels to listen to, it knows it is out of range, and displays a no service message. after finding the SID, the phones check to see if it matches the SID programmed in the phone, and if it does not match it knows that the phone is roaming. The central location that the cell phone is registered to keeps track of the cell that your phone is in, so that it can find you when someone calls the phone. When the phone is turned on it sends its ESN to the control channel.If the phone goes out of range, it will take a small while to locate your phone when it enters back into service. This can cause loss of calls, even though the phone is in service, but this problem is very temporary. When someone does call your phone it is sent to the central tower called the spry Telephone Switching Office (MTSO). This of fice is continually communicating with the cell phone. It sends and receives the calls, as well as telling it what frequencies to use. This is all done through the control channel, so it does not impair any calls.As you move toward the edge of your cell, the cells tower will see that your signal strength is diminishing. At the same time, the base station in the cell you are pathetic toward, which is listening and measuring signal strength on all frequencies, will be able to see your phones signal strength increasing. The two base stations coordinate themselves through the MTSO, and at some point, your phone gets a signal on a control channel telling it to revision frequencies. There are three common technologies used by cell phone providers.These are Frequency Division Multiple coming (FDMA), fourth dimension Division Multiple Access (TDMA), and Code Division Multiple Access (CDMA). In FDMA every call is done on a separate frequency. FDMA separates the spectrum into distinct voi ce channels by splitting it into uniform chunks of bandwidth. This is very similar to the way that radio stations operate. Each station is assigned a signal at a different frequency at bottom the available band. FDMA is used mainly for analog transmission, so it is slowly being phased out. It is capable of carrying digital information, but it is not considered an efficient method for digital transmission.Time Division Multiple Access gives each call a certain amount of time on a frequency. The Electronics Industry trammel and the Telecommunications Industry Association use TDMA. In TDMA, a narrow bandwidth that is 30 kHz wide and 6. 7 milliseconds long is split time-wise into three time slots. (Appendix D, figure 1) Each conversation gets the radio frequency for one-third of the time. This is possible because voice data that has been converted to digital information is compressed so that it takes up significantly less transmission space. Therefore, TDMA has three times the capacit y of an analog system using the same number of channels.TDMA systems operate in either the 800 megahertz or 1900 MHz frequency bands. Some phones have the ability to switch between bands. This function is called simply Dual-Band, and is important when travel between different band frequencies. TDMA is also the access technology for global System for Mobile communications. The Global system uses different frequencies in different areas of the world and is not compatible with other TDMA systems. GSM operates in the 900 MHz and 1800 MHz bands in Europe and Asia and in the 1900 MHz band in the united States. GSM systems use encryption to make phone calls more secure.GSM is the international standardized in Europe, Australia and much of Asia and Africa. In covered areas, cell-phone-users can buy one phone that will work anywhere else the standard is supported. To connect to the particular(prenominal) service providers in these different countries, GSM-users simply switch SIM cards. SIM cards are small removable disks that slip in and out of GSM cell phones. They descent all the connection data and identification numbers you need to access a particular wireless service provider. Unfortunately, the 1900 MHz GSM phones used in the United States are not compatible with the international system.