There are four major techniques that allocate capacity for wireless WAN communications. These techniques are Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Code Division Multiple Access (CDMA), and Orthogonal Frequency Division Multiplexing (OFDM). (Goleniewski, L. 2007) Each technique has pros and cons when compared amongst each other. The following is a summary of why each technique has a need, and some of the challenges that come with that technique.
Radio Frequency or RF is used in our everyday lives whether or not you realize it. Some of the common uses of Radio Frequencies are:
• AM radio - 535 kilohertz to 1.7 megahertz
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The electromagnetic wave or voltage as it can be called is usually broadcast by velocity at the rate of 186,300 miles per second. Radio Frequency Identification is measured by identifying unique items using radio waves. The classic RF structure has a transmitter and a receiver. The transmitter creates electrical signals that are called a carrier signal. The carrier signal frequency is determined by the wave length. The carrier signal is modulated to carry voice by adding a contrast signal to the wave form. The receiver gets the pair of sidebands and transforms them into speech or other sounds. RF in a wireless environment can have dead spots due to line of sight issues.
Frequency Division Multiple Access (FDMA) is a technique in which each user is assigned to a different frequency; it is used in older analog cellular systems. (Goleniewski, L. 2007) This allows everyone to speak at the same time, but it requires a different frequency band for each user. This creates a limitation of the technique, as each cell can only support 60 users. With the digital technology of today, FDMA is no longer a viable solution due to the limitation on users. It is also expensive for the service provider since there needs to be a transceiver for each channel, and because of the great amount of power that is consumed. FDMA does still serve a purpose today, though. It is used to divide the allocated spectrum into individual channels, by which other channels will then...