How Does Mobile Phone Works

      How Mobile Phone Woks

For most people, a mobile could be a a part of our lives. But many of us are curious to know as how a mobile makes a call, and why there are different generations of mobile communications?

     Image Source: File- uploaded by Sajal K. Das (Research Gate)

 

                                                                                                                     

Let's explore the technology behind mobile communications. When you speak on your phone, your voice is picked up by your phone's microphone. The microphone turns your voice into a digital signal with the assistance of MEMS sensor and IC. The digital signal contains your voice in the variety of zeroes and ones. An antenna inside the phone receives these zeroes and ones and transmits them within the form of electromagnetic waves. Electromagnetic waves transmit the zeroes and ones by altering the wave characteristics, such as the amplitude, frequency, phase, or combinations of those. For example, within the case of frequency, zero and one are transmitted by using low and high frequencies respectively. So, if you may find some way to transmit these electromagnetic waves to your friend's phone, you would be ready to establish a call. However, electromagnetic waves are incapable of traveling long distances. They lose their strength due to the presence of physical objects, electrical equipment, and some environmental factors. In fact, if there have been no such issues, even then, electromagnetic waves would not stick with it forever, due to the Earth's circular structure. To overcome these issues, cell towers were introduced, using the concept of cellular technology.

In cellular technology, a geographical area is divided into hexagonal cells with each cell having its own tower and frequency slot. Generally, these cell towers are connected through wires, or more specifically, optical fibre cables. These fibre cables are laid under the bottom or the ocean, to provide national or international connectivity. The electromagnetic waves produced by your phone are picked up by the tower in your cell and convert them into high frequency light pulses. These light pulses are carried to the bottom transceiver box, located at the bottom of the tower for further signal processing, after processing, your voice signal is routed towards the destination tower. Upon receiving the pulses, the destination tower radiates it outwards in the variety of electromagnetic waves, and your friend's phone then receives the signal. This signal undergoes a reverse process, and your friend hears your voice. So, it's true that mobile communications are not entirely wireless, they do use a wired medium too. This is how mobile communications are dole out.

However, Mobile communication is just successful when your tower transfers the signal to your friend’s tower. But how does your tower know in which cell tower area your friend is located? Well, for this process, the cell tower gets help from something called a mobile switching centre. The MSC (Mobile switching Centre) is that the central point of a group of cell towers. Before moving further, let's explain more information about the MSC. When you purchase a SIM card, all the subscription information is registered in an exceedingly specified MSC. This MSC are going to be your home MSC. The home MSC stores information such as service plans, your current location, and your activity status. If you progress outside the range of your home MSC, the new MSC, which serves you instead, is known as an overseas MSC. As you enter an overseas MSC region, it communicates along with your home MSC. In short, your home MSC always knows which MSC area you're in. To understand within which cell location the subscriber is within the MSE area, the MSC uses some techniques. One way is to update the subscriber location after a specific period. When the phone crosses a predefined number of towers, the location update is again done. The last one among these is when the phone is turned on. Let's attempt to understand all of those procedures with an example. Suppose, Annie wants to call David. When Annie dials David’s number, the call request arrives at Annie’s home MSC. Upon receiving David’s number, the request are going to be forwarded to David's home MSC. Now, David's MSC checks for his current MSC. If David is in his home MSC, the call requests are going to be immediately sent to his current cell location, and it checks whether David is performing on another call, or if his mobile is converted. If everything is positive, David's phone rings, and the call are going to be connected. However, if David isn't in his home MSC, David's home MSC simply forwards the decision request to the foreign MSC. The foreign MSC will follow the previously explained procedure to locate David's phone, and will then establish the decision. Now, let's discuss why the frequency spectrum is quite important in mobile phone communications. To transfer zeroes and ones in electronic communication, each subscriber is allocated a frequency range. However, the frequency spectrum available for cellular communications is quite limited, and there are billions of subscribers. This issue is solved with the help of two technologies, one frequency slot distribution, and two, multiple access technique. In the first technique, different frequency slots are carefully allocated to different cell towers. In the multiple access technique, this frequency slot is efficiently distributed amongst all the active users within the cell area. Now, the large question. Why are there different generations of mobile technologies? 1G originally allowed users, for the primary time, to carry a phone without a cable attached thereto. But 1G suffered from two major problems. The first problem was that the wireless transmission was in an analog format. Analog signals that are easily altered by external sources. So, it provided poor voice quality and poor security. The second problem was that it used the frequency division multiple access technique, which used the available spectrum in an inefficient way. These factors paved the way for the second generation of mobile communications, 2G used digital multiple access technologies, namely TDMA (Time-division multiple access), or CDMA (Code Division Multiple Access) technology. The second generation also introduced a revolutionary data service, SMS, and internet browsing. 3G technology was focused on giving a better data transfer speed. It used a WCD (Wireless collision detect ) multiple access technique, along with a rise in bandwidth. To achieve this, the 3G speed of two Mbps allowed the transfer of information for uses such as GPS, videos, voice calls, et cetera. 3G was an enormous step within the transformation of the essential phone to a smartphone. Next came 4G, which achieved speeds of 20 to 100 Mbps. This was suitable for prime resolution movies and tv. This higher speed was made possible due to the OFMDA (Orthogonal frequency division multiple access )multiple access technology, and MIMO ((multiple input, multiple output) technology. MIMO uses multiple transmitter receiver antennas inside both the mobile phone and also the towers. The next generation of mobile communication, 5G, to be unrolled soon, will use enhanced MIMO technology and millimetre waves. It will provide seamless connectivity to support the web of things, such as driverless cars and smart homes