Linear Constellation Precoded OFDM With Interleaved Subcarrier Index Modulation

Abstract

Orthogonal frequency-division multiplexing with index modulation (OFDM-IM) is an emerging and promising multicarrier transmission technique; however, frequency diversity achievement requires further investigation for the OFDM-IM. In this paper, the linear constellation precoded OFDM with interleaved subcarrier index modulation (LCP-OFDM-ISIM) is proposed, where a unitary matrix is employed to spread the constellation symbols over all the active subcarriers of the block and the binary constant weight code (BCWC) is utilized as the subcarrier activation pattern (SAP). At the receiver, energy detection is employed to initialize the SAP estimation, and then, the cascaded feedback detection is proposed to refine the detection performance by passing the detection results between the symbol detection and the data-assisted SAP detection. For L-taps channel, conditioned on the BCWC with the minimum Hamming distance of d, energy detection can achieve the diversity order of min(d/2, r), and a closed-form expression is derived for the energy detection. It is shown, via the pair-wise error probability, that the data-assisted SAP detection included in cascaded feedback detection can achieve the diversity order of min(d, L). The simulation results are provided to show the superiority of the LCP-OFDM-ISIM over the benchmarks.

Keywords

• Orthogonal frequency division multiplexing
• index modulation
• linear constellation precoding
• frequency diversity