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WHAT IS INDEX MODULATION IN OFDM?

By Admin on

INDEX MODULATION:

In recent years, multicarrier transmission has become an attractive technique in many wireless standards to meet the increasing demand for high data rate communication systems. One of the most popular multicarrier techniques, orthogonal frequency division multiplexing (OFDM), has developed into a widely-used scheme for wideband digital communication.  The major advantage of OFDM over single-carrier schemes is its ability to cope with frequency-selective fading channel with only one-tap equalizer.   



Spatial Modulation has been successfully applied to OFDM However, seems to be impractical because a perfect feed forward from the transmitter to the receiver needs to be assumed. Only in that way will the receiver know the mapping method for the subcarrier index selecting bits. This feed forward requirement from the transmitter to the receiver has later been removed. where an enhanced subcarrier index modulation OFDM (ESIM-OFDM) was proposed. Unfortunately, to achieve the same spectral efficiency as that of classical OFDM, this scheme needs to adopt higher order modulations. OFDM with generalized index modulation (OFDM-GIM) scheme is proposed in this paper. The generalization is proposed in two aspects. First, a more flexible selection of active subcarriers is proposed to further improve the spectral efficiency. However, the generalization in this aspect cannot fundamentally overcome OFDMIM’s difficulty in adopting QPSK symbols. In the second aspect of generalization, the in-phase component and quadrature component of QPSK symbols are split into two independent components so that index modulation is applied independently on these two components

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