Radio Communication and the Mobile Phone


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Radio Communication and the Mobile Phone

  1. 1. Radio Communication and the Mobile Phone Tom Kellett
  2. 2. Radio Waves <ul><li>What is a radio wave? </li></ul><ul><ul><li>Mobile phones and their base stations and receive signals using electromagnetic waves (aka electromagnetic fields or radio waves) </li></ul></ul><ul><ul><li>Electromagnetic radiation consists of oscillating electric and magnetic fields. The frequency (the number of times per second the wave oscillates) determines their properties and therefore, their use. </li></ul></ul><ul><ul><li>Frequencies are measured in Hertz (Hz) </li></ul></ul><ul><ul><ul><li>1Hz = one oscillation per second </li></ul></ul></ul><ul><ul><ul><li>1kHz = one thousand </li></ul></ul></ul><ul><ul><ul><li>1MHz = one million </li></ul></ul></ul><ul><ul><ul><li>1GHz = a thousand million </li></ul></ul></ul>
  3. 3. <ul><li>Frequencies between 30kHz and 300GHz are used for telecommunications including radio and television </li></ul><ul><li>In UK: </li></ul><ul><ul><li>AM radio = 180kHz – 1.6MHz (1600kHz) </li></ul></ul><ul><ul><li>Cellular Mobile Services = 872 – 960MHz, 1710 – 1875MHz, 1920 – 2170MHz </li></ul></ul>1251kHz (Bury St. Edmunds, Suffolk) 909kHz 1260kHz (Leicester)
  4. 4. Radio communication using amplitude modulation (AM) <ul><li>Carrier wave = a radio frequency wave used for radio communication </li></ul><ul><li>This is produced by the transmitter as a sine wave, which conveys very little information as it simply repeats. </li></ul><ul><li>It can be switched on and off, however, which led to it being used in the earliest radio transmissions involving Morse Code. </li></ul><ul><li>In order to carry more information, the data has to be added via the process of modulation. This process involves a feature of the carrier wave being varied in accordance with the information transmitted. </li></ul><ul><li>AM (Amplitude Modulation) Transmission, uses the electrical signal from a microphone to vary the amplitude of the carrier wave. </li></ul>
  5. 5. Amplitude Modulation:
  6. 6. How a mobile phone network uses radio communication <ul><li>A mobile phone sends and receives information by radio communication. </li></ul><ul><li>Radio frequency signals are transmitted from the phone to the nearest base station. Incoming signals are sent from the base station to the phone at a slightly different frequency. Base stations link mobile phones to the rest of the mobile and fixed phone network. </li></ul><ul><li>Each base station provides radio coverage to a geographical area known as a cell. </li></ul><ul><ul><li>Base stations are connected to one another by central switching centres, which track calls and transfer them as the caller moves from one cell to the next. </li></ul></ul>
  7. 7. <ul><li>An ideal network may be seen as consisting of hexagonal cells, each with a base station at its centre. The cells overlap at the edges to ensure the mobile phone users always remain within range of the base station. </li></ul><ul><li>The size of each cell depends on three factors. </li></ul><ul><ul><li>First, the local terrain; radio signals are blocked by trees, hills and buildings. </li></ul></ul><ul><ul><li>Second, the frequency band in which the network operates (in general, the higher the radio frequency, the smaller the cell). </li></ul></ul><ul><ul><li>Third, the capacity (i.e. number of calls) needed in any given area. </li></ul></ul>The cell structure of a mobile phone network.
  8. 8. References <ul><li>Brain, Marshall, Jeff Tyson and Julia Layton (2000) How Cell Phones Work [WWW] Available from: [Accessed 27 January 2011] </li></ul><ul><li>PUBLIC TELECOMMUNICATION NETWORKS UNIT (2001) How Mobile Phone Networks Work [WWW] Ofcom. Available from: [Accessed 27/01/11] </li></ul><ul><li>BBC Radio 5 Live logo (nd) [Online Image] Available from: [Accessed 27/01/11] </li></ul><ul><li>'Gold_(Radio)_logo.png' (nd) [Online Image] Available from: [Accessed 27/01/11] </li></ul><ul><li>'How-to-improve-Mobile-Phone-Communication-network-Signals.jpg' (2010) [Online Image] Available from: [Accessed 27/01/11] </li></ul><ul><li>Sabras Sound Logo (nd) [Online Image] Available from: [Accessed 27/01/11] </li></ul>