Saturday, September 28, 2019
A cellular network
A cellular network A cellular network is a radio network made of number of radio cells, each severed by fixed positioned based station. These cells stations cover several different areas and provide large radio coverage. In order for this to happen a variable number of portable transceivers can be used in any cell and moved through one cell during transmission. The use of multiple cells means that if the distributed transceivers are mobile and moving from one point to another point they should change also from cell to cell. This mechanism could be different according to the type of network and change of circumstances. In this case clear coordination between base station and mobile station is must in order to avoid communication interruption. The most common example of cellular Network is a cell or mobile phone, which is a portable telephone that could be dialled or receives calls through base station or transmitting tower. Radio waves transfer signal to and from mobile phone. The coverage area of serv ice provider sometime is split into small cells in order to prevent signal losses and also a large number of active phones in the area. The range of signals could be different in cities and rural areas. All base stations are connected to mobile phone switches centre, which connect to a public telephone network or to another mobile company switch. As the mobile consumer moves from one cell area to another cell, the switch automatically commands the handset and a cell site with a stronger signal (reported by each handset) to switch to a new radio channel (frequency). When the handset responds through the new cell site, the exchange switches the connection to the new cell site. Modern cell phones networks use cell as radio frequencies are limited, shared resource, base stations and handsets change frequency and use low power transmitters in order that limited number of radio frequency can be used at the same time by many users with less interferences. To distinguish signals from a vari eties of different transmitters, frequency division multiple access (FDMA) and code division multiple access (CDMA) has been developed. Advantage of cellular Network over other alternative solutions is: Increase capacity. Power usage reduced. Huge coverage area. Interference from other signals reduced. Reference paper 10 The evolution of the cellular Network started to flourish during the last years in which several different systems were developed; as a result we have first generation (1G), second generation (2G), third generation (3G) cellular networks and the trend is continuously increasing. The first generation (1G) was used from 1970-1980 and now is retired. In 1990 the second generation (2G) of Networks were launched such as Global System for Mobile communications (GSM), Personal Communications Service (PCS), and Integrated Digital Enhanced Network (IDEN) and so on. The second generation (2G) of networks replaced the (1G) and became very popular with digital processing, enabl ing wireless transmission of voice as well as data and have different Variety of new features such as a Push to Talk, Short Messaging service(SMS), caller ID, conference calling, voice mail, email messaging and so on.