A novel PLS technique for secure ESM based MIMO systems

Multiple-input multiple-output systems with spatial modulation has evolved into an energy efficient and less complex wireless transmission system due to the use of limited radio frequency chains. In this work, a novel physical layer security scheme with enhanced spatial modulation (ESM) and secret key generation using multi-level adaptive threshold binary-coded decimal quantization algorithm is introduced. The proposed method, as SPACESM, enhances spectral efficiency using ESM and achieves confidentiality by adaptively selecting and shuffling the codebook in ESM. For selection of ESM codebook, SPACESM uses physical layer signature called channel signal to noise ratio (SNR) and for shuffling of codebook and rotation of transmit vector, secret key is generated at the transmitter and receiver separately by threshold-based quantization algorithm, which uses channel state information. Adaptive modulation technique selects the modulation order for different SNR. The performance of the proposed method is evaluated in terms of confidentiality, spectral efficiency, and robustness of secret key through MATLAB simulation.The proposed SPACESM technique provides 2 bpcu improvement for both $$N_t$$ N t = 2 and $$N_t$$ N t = 4 with M = 64 than the existing SM. Also it provides 3 dB and 4 dB SNR gain than SM for $$N_t$$ N t = 2 and $$N_t$$ N t = 4 respectively. Similarly, it provides 2 dB and 4 dB SNR gain than the SMX technique for $$N_t$$ N t = 2 and $$N_t$$ N t = 4 respectively. In summary, the proposed method outperforms than the SMX and SM technique in all aspects.