How Multiple users Access the radio “resource” or set of frequencies allocated to each cell. In Orthogonal Frequency Division Multiple Access each user gets given a specific set of “orthogonal” frequencies from within a (usually very large) set with which to talk to the cell. Other users get other frequencies, so there is no interference between users. Typically OFDMA is combined with another technology like TDMA to maximise flexibility. A set of orthogonal frequencies is one where each frequency is an integer multiple of a base frequency and exactly one cycle of the base frequency is used in the time dimension. OFDMA has the great benefit that it can be easily generated using a piece of chip hardware called a Fast Fourier Transform.

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