Novel OFDM System Using Data-Nulling Superimposed Pilots With Subcarrier Index Modulation

A novel orthogonal frequency-division multiplexing system using data-nulling superimposed pilots with subcarrier index modulation (SIM) is proposed, where the constellation modulation vector is first spread over all subcarriers using a precoding matrix, then the subcarriers activated by SIM are nulled and inserted by the superimposed pilots (SPs). As the nonzero subcarriers index of the SP is exploited to convey additional information using SIM, the SP not only completes channel estimation without a loss of bandwidth, but also transmits additional information. Two different blind pilot-detection techniques (BPDTs) (which detects the nonzero subcarriers index of the SP without any prior knowledge at the receiver) are designed to demodulate the information conveyed by the SP using SIM and extract the SP from the received signal to estimate channel state information. Monte Carlo simulation results show that the proposed BPDTs achieve good pilot detection performances, and the nonzero subcarrier index of the SP is effectively exploited to convey additional information.