Mobile phone function are as below: brands. This discussion does not include the extra components of a mobile phone like video camera and its related function, radio, music player and external memory. The topic is limited for mobile telecommunication only how its works and their interdependence. There are three major sections inside a mobile phone Power Section Radio Section Computer Section Power Section: A power section deals with power related tasks such as power distribution or charging the battery so this section can be divided into two sub sections like. Power Distribution A power distribution section is built around an "power IC" it takes 3.6V power from battery and regulates its power and then distributes to the other components used in mobile phone circuit. in some mobile phones tech "RF Power amplifier" uses more Power than provided bye mobile phone's battery .i.e. 4.7 V or 5.6 V in some phones. the power Ic with a power boaster coil is used to increase voltages. so we can say that power IC is used to provide power to other components how much they needed. either less than battery voltage or more than it. Charging Section A charging section works for battery charging purposes.it is often consists a fuse, a coil, a protecting diode, a filter capacitor and charging IC and some other discreet. the charging section helps battery to be charged when it needs and when battery is charged, charging IC reads its state of charge and feels it full charged and then disconnects charging from it. Radio Section: A radio section has basically a set of four main functions.wich are. Band Switching RF Power Amplification Transmitter (TX) Receiver (RX) Band Switching: In the modern mobile phone communication techniques. the frequency of mobile phone communication is divided into three bands GSM (operates on 900 MHz) DCS (operates on 1800 MHz) PCS (operates on 1900 MHz) DCS means Distributed control system.Its is state of the art technology to control almost any kind of process through various controllers. the third band is used only in USA whereas the first two bands are used in the rest of the world. band switching is done bye a "ceramic antenna switch" it reads from the radiation dispersed in the air and then switches to the appropriate band. in the very first phase of mobile phones there were single band handsets which operated on single frequency band but now a days all the handsets are dual band or tri band in operation. RF Power Amplifier RF power amplifier is often called as ".PA" or"Transmitter" its functions is to amplify or boast the power which is being transmitted to air, so may it would be able to communicate with long distances. a typical .PA can amplify rf power up to 0.6W or 600mW. This amount of rf power is sufficient to communicate nearly 20 to 25 kilometers in open area, but all the PA's are controlled by there rf signal processor, so if we are near our cell base tower the PA of our phone will transmit low power but if we are far away it will produce its maximum power. Transmitting (RX) A mobile phone's rf section is basically built around an rf IC which is often called rf signal processor whereas in nokia it is called hagar IC in some hand sets and in some hand sets it is called Mjoelner. irrespectively of the brands and verity of names we call it rf signal processor. this IC works as transmitter and receiver as well. working as transmitter it takes instructions from phone's computer and also takes audio data from audio section and creates radio waves then mixes audio data to its radio waves according to the instructions given by computer section. this mixer of audio and radio is sent to PA to amplify its strength Reciever (RX) A reciver section for rf waves is built in rf IC, as it is said that this IC works for dual purposes first transmitting and section recieving. in the recieving section of mobile phones a radio signal is gather from ceramic antenna switch and then it is filtered and sent to rf IC to further process. in rf IC signal is detected and then rectified for audio and data which is sent to audio IC or computer section. Computer Section: A computer section in mobile phone consists of two main functions CPU(central processing unit) Memory (RAM, FLASH, COMBO CHIP) CPU: A CPU is used in mobile phones as a central processing arithematic or controler. the cpu controls various functions in mobile phones like signal, display, sound converting(DSP), charging, power on, rf channel controler, rf tx power conroller, LEDs, vibrator, data processing, data storing etc. so we can say that if a cpu is damaged in any mobile phone it cannot be repaired unless the CPU is not replaced but this type of fault is not even seen to me ever either memory chips can be damaged. in brand Nokia CPU is named with two different words (MAD or UPP) Memory: there are two main types of memories used in mobile phones RAM (Random Access Memory) The RAM is used in mobile phones to store user data in mobile phones. So these a days we can store pictures, messages, ringtones, applications, themes and other these type of things in mobile phones so CPU stores these types of data in the RAM of our mobile phones. Flash (eeprom, ROM etc) The flash chip is used in mobile phones to hold mobile phone's operating system in it. so if the flash chip is damaged in mobile phones the phone cannot power on properly because all the instructions to start a mobile phones and its various tasks like call making , display etc are stored in the flash chip of mobile phones. Combo Chip In smoe mobile phones there is a combined type of memory used which is called combo memory chips these types of memories work for both like RAM and Flash.The clear example of this type of memory is used in Nokia 1100. Note: Multy Media Cards are not a part of mobile phones becaues they are used externally. How A GSM Cellular Network Operates GSM 900/DCS 1800 networks use a sophisticated array of digital equipment to provide you with a seamless, hiss-free connection. Below are some of the critical components & procedures that allow them to do so: GSM (Global System for Mobile Communications) uses a series of radio transmitters called Base Stations (BS) to connect you and your cellphone to your cellular network. Each BS is also termed a CELL so named because it covers a certain range within a discrete area (cell). Base Stations are all interconnected, which is why you can move from one cell to another - a process called "hand-over" – without losing your connection. Base Station Controller: A set of Base Stations is connected to a particular Base Station Controller. MSC :The combination of a cellphone and the SIM card creates a special digital "signature" - that includes your subscriber number - which is sent from your cellphone to the nearest BS asking that you as a subscriber of a particular network be allowed to use the network. The request is passed on along the network of BSs to the multifaceted heart of a cellular network -the Mobile Switching Center (MSC). The MSC also routes all your incoming and outgoing calls to and from the fixed-line networks or other cellular networks. HLR :The MSC also contains a critical component called the Home Location Register (HLR) which provides the administrative information required to authenticate, register and locate you as a that network's subscriber. Once it’s received your log-on request, the HLR immediately checks the special "signature" contained in the request against it’s special subscriber database. If your subscription is current, the MSC sends a message back to the phone via the network of BSs that indicates that you’re allowed to access the network. The name or code of that network will appear on the LCD screen of the cellphone. Once this network "name" message appears on your phone’s LCD screen, it means you’re connected to the network and able to make and receive calls. The entire log-on process usually takes only a couple of seconds. Polling: At the same time, the HLR also registers which BS your cellphone is currently connected to, so that when the network’s MSC needs to route an incoming call to your cellphone number, it will first check the HLR to see where you are. Every now and gain, the cellphone will send a message to the network indicating where it is, a process called Polling. Multiplexing Each BS uses digital techniques to enable a number of phones to be simultaneously connected to it, as well as simultaneously allowing a number of subscribers to make and receive calls. This sophisticated digital call-juggling ability is called Multiplexing. However, the combination of the tracking function and your unique digital signature allows the MSC to route that call to the precise BS your cellphone happens to be connected to, and then exclusively to your cellphone - even if a number of other subscribers are simultaneously connected to that BS. Hand Over: When you "hand-over" to another cell whilst driving, the HLR is automatically updated, and continues to monitor where exactly it should route your calls should you then move within range of another BS. This sophisticated routing procedure means that out of hundreds of thousands of subscribers, only the correct cellphone will ring when necessary. VLR: When you want to make an outgoing call, another section of the MSC called the Visitor Location Register (VLR) checks whether you are actually allowed to make that call. For example, if you are barred for international dialing, a message to that effect will be generated by the VLR, sent along the network, and almost instantly back to your cellphone. MailBox: If you’re unavailable for some reason and your Mailbox has been activated, any incoming voice calls will be transferred to the Mail system. SMSC: Some VoiceMail systems are linked to a network's SMS Center (SMSC), a special facility that handles Short Messages. The SMSC generates the special SMS message that notifies you that you have mail waiting in your Mailbox. SMS messages can be received on your SMS-capable cellphone even while you’re on a voice call. That’s because they are sent on a different radio frequency - the GSM data channel - than voice calls, so that the two never interfere. These sophisticated digital facilities are the reason why GSM is now considered the de facto global cellular standard We hope the topic is of great help to you.
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