Carolyn N. Kinder
Cell phone networks use three common technologies: 1) Frequency-Division Multiple Access (FDMA); 2) Time-Division Multiple Access (TDMA) and Code-Division Multiple Access (CDMA).
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Frequency-Division Multiple Access (FDMA)
First the FDMA puts each call on a separate frequency. It separates the spectrum into distinct voice channels by splitting it into equal pieces of bandwith and sending it out. This is used mainly for analog and not considered to be effective.
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Next, TDMA assigns each cell a certain portion of time on a designated frequency. TDMA is a 30 MHz wide analog channel broken down into 6.7 millisecond time slices with each split into three time slots. Voice data is compressed to digital information with less transmission space than analog. TDMA is the access technology for the global communication system for mobile communication (GSM) and operates at 1.9 GHz in the U.S. It is used in digital cellular.
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CDMA gives a unique code to each call and spreads it over the available frequencies by using spreading technology. Each phone will transmit on all the allotted frequencies. Each phone uses a different random number to decide which frequency. It will assign a code and will time stamp each signal. It uses the global positioning system (GPS) to get information.
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