  Orthogonal frequency division multiplexing with index modulation (OFDM-IM) is
a novel multicarrier scheme, which uses the k out of n subcarriers as active
subcarriers to transmit data. For detecting the subcarrier activation pattern
(SAP) at the receiver, maximum likelihood (ML) detection cannot be used because
of its high computational complexity. Instead, the detector selecting the most
likely active k subcarriers is used, which is called a k largest values (klv)
detector. However, this method degrades the detection performance especially if
the ratio of illegal SAPs to SAPs is high. In this letter, the suboptimal ML
detector is proposed, which is a slight modification of the klv detector.
However, the proposed detector has a similar detection performance compared to
the ML detection, which is suitable for flexible implementation of OFDM-IM
systems.
