MOBILE PHONEPART 3 CONTINUED FROM PART2
17. The GSMSystem Global System for Mobile Communications is thestandard for mobile telephone systems in the world. In GSM, the signaling and speech channels aredigital, therefore GSM is considered a 2G (Second Generation) system.This helps wide-spread implementation of data communication applications. There are five different cellsizes in a GSM network These are macro, micro, pico, femto and umbrella cells. Macro cells arecells where the base station antenna is installed on a mast above average roof top level. Micro cells are cells whose antenna height is under average rooftop level. Pico cells are small cells whose coverage diameter is a fewdozen metres. These are mainly used in indoors applications. Femto cells are cells designed for use in residential or smallbusiness environments and connect to the service provider’s network via abroadband internet connection. Umbrellacells are used to cover shadowed regions of smaller cells and fill in gaps in coverage betweenthose cells. Horizontal radius of the cell varies depending on the antennaheight, antenna gain and propagation conditions. Maximumdistance the GSM supports is 35 kilometers. Most 2G GSM networks operate in the 900 MHz or 1800MHz bands while 3G GSM in the 2100 MHz frequency band. My note- Now 5 G is being implemented. This means better quality andchange in MHz 18 Time Sharing Time Division Multiplexing technique is used to shareeight full-rate or sixteen half-rate speech channels per radio frequencychannel. There are eight radio time slots grouped into a TDMA frame. 19 Mobile Network Mobile phone convertsvoice, text, multi-media messages or data calls into Radio Frequencies (RF). Mobile phone base stationstransmit and receive these RF signals and connect callers to other phones andother networks. Mobile phone network is divided into thousands of overlapping,individual geographic areas or ‘cells’, each with a base station. The size of acell depends on the area of coverage and the number of calls that are made inthat area. The smallestcells are in crowded urban areas with large buildings and heavy populationdensity, while the biggest cells are in rural areas, where people are dispersed. 20 Channelsemployed There are two types of channels used in GSM . Theseare Control channels and Traffic channels. 20a Controlchannels These are responsible for housekeeping tasks such astelling the mobile when a call is coming in and which frequency to use. Toensure this handover works, the phone constantly monitors the broadcast control channel of up to 16neighboring cells. In normal operation, phones continually adjustthe power of the radio waves they send out to be the minimum needed for thebase station to receive a clear signal. If a phone moves far away from its base station and if thesignal is weak, the network consults the list and triggers a handover to aneighboring cell with best signal. 20b Trafficchannels It is used to carry calls or other data from themobile phone to the base station and vice versa. In the Traffic channel, voiceor text data is carried in bursts. Each burst comprises two consecutive stringsof bits (a series of signals representing 1s and 0s), each 57 bits long. 21 Range The range within which mobile devices can connect isnot a fixed figure. Itdepends on a number of factors like the frequency of signal in use, thetransmitter’s rated power, the transmitter’s size etc. My note-Often while we travel in train/ bus the range differs, speech becomes unclear or disrupted. With in the premisesof home many times while coming outside the speech becomes clear because range increases (The resistance ofwalls in the home are removed and strong signals and frequency is received. 22 Inside theMobile phone Mobile phone is a sophisticated device using SMD components,Microprocessor, Flash memory etc. In addition to the Circuit board, Mobilephone also has Antenna, Liquid Crystal Display(LCD) , Keyboard, Microphone, Speaker andBattery. The circuit boardis the heart of the Mobile phone. It has chips like Analog-to-Digital and Digital-to-Analog conversionchips that translate the outgoing audio signal from analog to digital and theincoming signal from digital back to analog. Following arethe Chips present in Mobile phone. 1Digital signalprocessor It is generally rated as having 40 MIPS (millions ofinstructions per second) to conduct calculations of signal manipulation at highspeed. This chip deals with both compression and decompression of the signals. 2. Microprocessor It handles all the housekeeping tasks for the keyboardand display. It also deals with command and control signaling with the basestation, and coordinates the rest of the functions on the board. 3.The Flash memory The Flashmemory and ROM Chips of the Mobile phone act as a storage location for the phone. These chips store the customizableoptions of the cell phone, as well as the entire operating system. The powerand radio frequency sections of the phone, phone recharging and powermanagement etc are controlled by this chip. It also controls several hundred FMchannels. The RFamplifiers focus on signals that go in and out of the phone’s antennae. My note- Pressent day smart phones and ordinary phones, the antenna is not much visible protruding outif the device. It will be appearing through a small hole to theright of charging connector in ordinary phones and smartphones. 23 Mobile Phone Maintenance Mobile phone is a delicate device and needs care forits proper functioning. Here are the common measures to keep the mobile phonein good condition. Do not keepMobile phone in wet area or use it with wet hands. Moisture can cause non-repairable internalcorrosion of parts. Do not drop the phone or damage the connection points. Do not overstress the phone. It may damage the display. Do not keepthe phone near heat generating devices. High temperature in a car can damageits electronics. Do not overcharge the battery. Charge the battery only its charge status goes below 50 percent. PreventCloning. A phone is“Cloned” when someone steals its ID number and is able to make fraudulent callson the owner’s account. When the phone makes a call, it transmits the ESN and MIN- a uniquetag- for your phone to the network at the beginning of the call. When the phonetransmits its MIN/ESN pair, it is possible to capture the ESN-MIN pair. Using aScanner device it is easy to modify another phone so that it contains yourMIN-ESN tags. This allows the person to make calls on your account. Cloning mayalso occurs when the phone is repaired in an unauthorized service centre. It ispossible to copy the data including images and video present in the phone. My note- Manyother points like erasing memory information, tapping a mobile etc, which are commonly heard now, are offences and punishableunder law -- You received this message because you are subscribed to the Google Groups "Thatha_Patty" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/thatha_patty/1735012450.2861561.1671960891533%40mail.yahoo.com.
