Cellular Technical Information
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Mobile phones transmit and receive voice and data signals using radio waves. These transmissions occur on a particular set of frequencies, using specific protocols. Since it is necessary for a mobile phone system to support more than one conversation at a time, each protocol uses a multiple access method, in order to accommodate multiple users.

The main thing that makes large-scale mobile phone networks possible, and the reason that they are sometimes called "cellular" phone systems, is the concept of frequency re-use. (It would be a good idea to read the page on frequency re-use before continuing with the rest of the information on this page.)

Frequencies, Multiple Access Systems, and Protocols:

• Four Mobile Phone Frequency Ranges Are in Use Worldwide:
  • North America & Much of South America:
    • 800MHz (USA original "Cellular" band, introduced in 1983)
    • 1900MHz (USA "PCS" band, introduced in 1994)
  • Europe & Much of Asia and Africa:
    • 900MHz
    • 1800MHz

  These frequencies cover most parts of the world. A few countries use a 400MHz or 450MHz band, and there is talk of a future 2100MHz band for 3G systems.

• Three Types of Multiple Access Systems:
  • FDMA
• TDMA
• CDMA

• Five Air Interfaces ("Cellular Protocols") Based on FDMA, TDMA & CDMA:
  • AMPS (uses FDMA)
  • IS-54 & IS-136 (Uses FDMA and TDMA, and is commonly referred to as just "TDMA".)
  • GSM (uses FDMA and TDMA)
  • iDEN (uses FDMA and TDMA)
  • IS-95 (Uses CDMA and is commonly referred to as just "CDMA" or "cdmaOne".)
  • CDMA2000 1xRTT, 1xEV-DO & 1xEV-DV (3G protocols that use CDMA.)