A new spectrally efficient pilot scheme for OFDM systems

In this paper, new pilot insertion techniques that make use of index modulation (IM) idea for channel estimation (CE) are proposed for orthogonal frequency division multiplexing (OFDM) systems. These techniques not only perform CE but also convey additional bits. Simulation results show that the performance of the proposed schemes are very close to the performance of the classical pilot symbol-assisted (PSA) OFDM system, with the additional benefit that more bits can be transmitted. Despite a slight increase in the complexity of the receiver, higher spectral efficiency than conventional OFDM systems can be achieved. Especially, the proposed method-II transmits more bits than the proposed method-I owing to its subblock form.