Orthogonal frequency division multiplexing (OFDM) with index modulation (IM) is a multicarrier transmission technique for frequency-selective fading channels. Although it is energy and spectral efficient, its performance may not be satisfactory as some active subcarriers can be suppressed by fading. In this letter, we consider trellis coded modulation (TCM) for OFDM-IM in order to improve the detection performance of active subcarriers by increasing the Hamming distance between index symbols. We devise mapping rules for TCM for two cases and it is shown that the diversity order can be improved, which results in a lower probability of index error.
- index modulation
- orthogonal frequency division multiplexing
- Trellis coded modulation