The index modulation is a novel technique. This index modulation concept firstly introduced in MIMO system. So it is
possible to adopt this concept in case of OFDM. Orthogonal frequency division multiplexing (OFDM) with index modulation
(OFDM-IM) is a recently proposed multicarrier transmission technique. In which the indices of the active subcarriers are used
to carry additional information bits. In order to achieve a diversity gain for index detection a simple transmit diversity scheme
is used with OFDM-IM. Convolution encoder is used in the OFDM-IM with transmit diversity(OFDM-IM-TD) to achieve better
BER performance under Rayleigh fading channel. But OFDM-IM with transmit diversityc has poor spectral efficiency. Because
only 50% of active subcarrier is used for the transmission of information in the existing work. So here propose adaptive
selection of active subcarrier. We can choose 75% active subcarrier, 50% active subcarrier and 25% active subcarrier out of
total subcarrier adaptively.
