Orthogonal Frequency Division Multiplexing (OFDM) is the method of modulation that uses in both LTE and WiMAX. So, what is exactly OFDM and what are the advantages of using it?
OFDM is a multicarrier modulation scheme utilized as a digital multicarrier modulation method. This technology is used in multiple communications. For instance, in wired communications; DSL, power line communications (PLC) and in wireless communications; wireless LAN (WLAN), terrestrial digital system digital video broadcasting terrestrial (DVB-T) or digital video broadcasting-handheld (DVB-H) amongst others. Its working principle is such that dividing a high rate data stream into several parallel smaller data streams or we call it "channel", and modulate each of the streams on separate carriers, called subcarriers.
In order to keep each OFDM symbol independent among others over the channel, it is necessary to introduce a guard time between each symbol. A larger guard band is able to guarantee a low possibility of interference between OFDM symbols (ISI).
Also, the other advantages of OFDM including:
Reduce computational complexity. Fast Fourier Transform (FFT) and Inverse Fourier Transform (IFFT) can be used to implement the OFDM.
Delay the degradation of performance under the delay spread. As the delay spread grows over the maximum delay spread which was designed for optimal performance, performance of an OFDM degrades slowly.
Exploitation of frequency diversity. OFDM facilitates coding and interleaving subcarriers in the frequency domain, which provide robustness against burst errors, parts of the data that are transmitted into spectral bad channel conditions.
Can be used as a multi access scheme. The resources are partitioned among other users. However, this is normally used in Mobile WiMAX.
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