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  1. 1. radio wavesLau Siu Ching Jonathan p08294715
  2. 2. According to an online encyclopedia, the definition of radio waves are a type of electromagnetic radiation with wavelengthsin the electromagnetic spectrum longer than infrared light.
  3. 3. James Clerk Maxwell first formally assumed the existence of electromagnetic waves and it was confirmed by Heinrich Rudolf Hertz afterwards.
  4. 4. Radio waves were broadly used during theearly history of radio to produce radioinstruments. The radio technologydevelopment began as “wireless telegraphy”.
  5. 5. Radio broadcasting is a one-way wirelesstransmission over radio waves which reaches a wide range audiences. - There are two types of modulation usedin the process of radio broadcasting and they are AM broadcasting and FM broadcasting.
  6. 6. AM broadcasting (amplitude modulation) It is the first method of broadcasting sound on a radio signal and is still widely used today. Amplitude modulation was used for a smallscale voice and music broadcasts until the World War One.
  7. 7. FM broadcasting (frequency modulation)FM radio was invented in the 1930s forovercoming the interferences problems the AMradios were facing. And it was made possible byspacing station further apart. Frequencymodulation stations are much more popularsince higher sound quality and stereobroadcasting became the common format.
  8. 8. Cellular networkIt is a radio network distributed over land areascalled cells, which are transmitted throughfixed-location transceiver known as a cell siteor a base station.
  9. 9. Cellular networks are now widely used becauseof its advantages, for example it allows a bigrange of people using it at the same time, itreduces power use, and it covers a large areawithout huge interference from other signals.Nowadays, people use them daily with portabletransceivers (mobile phones/ smart phones).
  10. 10. Cellular network was launched in Japan in 1979as the 1st Generation (1G). But it was replacedbut the 2nd Generation (2G) digitaltelecommunication in a year after it waslaunched. In May 2001, the 3rd Generation (3G)was released and the transmission rates arehigher than before and improving.
  11. 11. In 2009, the 4th Generation (4G) wasintroduced and it is based on cellular wirelessstandards. It is now available for a pre-releasetrial as a form of LTE (Long-term-evolution) andit will be available late 2012.