Secrecy Enhancement for Multiple-Input Multiple-Output OFDM with Index Modulation

摘要

In this paper, we consider the security issue of multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing with index modulation (OFDM-IM) systems with a passive multiple-antenna eavesdropper. A physical-layer security scheme based on quadrature spatial modulation (QSM) and artificial noise (AN) is proposed to resist eavesdropping while maintaining the same receiver as the conventional OFDM-IM at the destination. By exploiting the structure of QSM, the generated OFDM-IM symbols are split into two orthogonal parts, and precoded ANs are injected into each part to produce combined symbols for transmission. Secrecy rate of the proposed secure MIMO OFDM-IM is derived and evaluated through numerical simulations. Compared to the existing secure OFDM-IM scheme, the proposed secure MIMO OFDM-IM shows better security against eavesdropping, especially when the eavesdropping channel is correlated to the legitimate channel.