Introduction of Mobile phone:
A mobile phone (also known as a hand phone, cell phone, or cellular telephone[1]) is a small portable radio telephone.
The mobile phone can be used to communicate over long distances without wires. It works by communicating with a nearby base station (also called a "mobile tower") which connects it to the main phone network. When moving, if the mobile phone gets too far away from the cell it is connected to, that cell sends a message to another cell to tell the new cell to take over the call. This is called a "hand off," and the call continues with the new cell the phone is connected to. The hand-off is done so well and carefully that the user will usually never even know that the call was transferred to another cell.
As mobile phones became more popular, they began to cost less money, and more people could afford them. Monthly plans became available for rates as low as US$30 or US$40 a month. Cell phones have become so cheap to own that they have mostly replaced pay phones and phone booths except for urban areas with many people.
In the 21st century, a new type of mobile phone, called smartphones, have become popular. Since the 2010s, more people use smartphones than the old kind of mobile phone, which are called feature phones.
History
Mobile phones in the 1950s through 1970s were large and heavy, and most were built into cars. In the late 20th century technology improved so people could carry their phones with ease.
Although Dr. Martin Cooper from Motorola made the first call using a mobile phone in 1973 (using a handset weighing 2 kilograms), it did not use the type of cellular mobile phone network that we use today.
The first cellular mobile phone networks were created in 1979 in Japan. Now almost all urban areas, and many country areas, are covered by mobile phone networks.
Technology
A cell phone combines technologies, mainly telephone, radio, and computer. Most also have a digital camera inside.
Cell phones work as two-way radios. They send electromagnetic microwaves from base station to base station. The waves are sent through antennas. This is called wireless communication.
Early cell telephones used analog networks. They became rare late in the 20th century. Modern phones use digital networks.
The first digital networks are also known as second generation, or 2G, technologies. The most used digital network is GSM (Global System for Mobile communication). It is used mainly in Europe and Asia, while CDMA (Code-Division Multiple Access) networks are mainly used in North America. The difference is in communication protocol. Other countries like Japan have different 2G protocols. A few 2G networks are still used. 3G are more common, and many places have 4G.
The radio waves that the mobile phone networks use are split into different frequencies. The frequency is measured in Hz. Low frequencies can send the signal farther. Higher frequencies provide better connections and the voice communications are generally clearer. Four main frequencies are used around the world: 850, 900, 1800 and 1900 MHz. Europe uses 900 and 1800 MHz and North America uses 850 and 1900 MHz.
Today there are mobile phones that work on two, three or four frequencies. The most advanced phones work on all frequencies. They are called 'world' phones and can be used everywhere.