Communication and Media Technology – Mobile Telephone Networks
Mobile telephone networks allow users to be reached at any time and in most parts of the world. Modern mobile devices are increasingly powerful and versatile and have become an indispensable modern device.
Mobile phones or cell phones are small, portable telephones, connected via radio to mobile telephone networks. A mobile network consists of fixed transmitting and receiving centers, called cell sites or base stations. Each base station is responsible for a specific area. Together, they create a network of cells providing full coverage. In city centers, base stations may be only a few hundred yards or meters apart, while in rural areas they might be separated by several miles or kilometers.
Neighboring cells use different frequencies to avoid interference. Within each cell, a large number of users can place calls simultaneously. This means that their radio signals must be easily distinguishable. This is achieved, for instance, through the use of different frequencies, or through cooperatively timing transmission and reception.
Technical standards
The Global System for Mobile Communications, or GSM, is an international standard for digital mobile phone networks. It includes voice telephone systems and also the transmission of text messages. The GSM standard has gradually been expanded, with the addition of HSCSD, GPRS, and EDGE, among others. These standards and technology allow mobile and cell phones to carry out data transfer and offer Internet access.
Among the latest standards for mobile phones and cell phone networks is the Universal Mobile Telecommunications System, or UMTS, which allows even faster data transmission. Presently, GSM and UMTS networks are being operated in parallel, but UMTS will soon replace GSM.
The universal mobile phone
Modern cell phones serve as portable offices, featuring diaries, word processing, e-mail and web browsing. They can also receive radio and television broadcasts, function as digital cameras and with an optional GPS, operate similarly to an in-car satellite navigation system.
Cell phones can also be used to buy items in special stores, pay for parking or purchase tickets.
ELECTROSMOG
This term refers to the environmental effects caused by electromagnetic fields. These are most notably produced by high-tension wires, electrical appliances, computers, radio towers, and mobile phone base stations. The fields can affect living things as well as electronic devices.
The effect of low levels of electrosmog generated by personal electronics and its potential harmful effects is controversial. High numbers of people have claimed negative health effects; however, further studies by doctors have been inconclusive
BASICS
IN ADDITION to land-based cell phone systems, satellite networks also offer mobile calling services. Because of their higher calling costs and larger, more awkward phones, they are mainly used in places offering no other means of communication, such as unpopulated areas.
Despite the cost, so-called Sat Phones remain popular with sailors, mountain climbers, and the military.