Design and Implementation of Secure CP-Less Multi-User OCDM Transceiver for 6G Wireless Communication Networks

In this paper, we designed and implemented a multi-antenna configured secure millimeter-wave (mmWave) CP-less multi-user orthogonal chirp division multiplexing (OCDM) transceiver. The proposed simulated system emphasizes more applicable performance metrics for a typically assumed case of four users and a passive eavesdropper for audio data transmission. We introduce a four-dimensional hyperchaotic system-based encryption algorithm to enhance physical layer security (PLS). In addition, low-density parity check (LDPC), TURBO, (3, 2 ) single parity check (SPC), and repeat and accumulate (RA) channel coding with Cholesky decomposition-based zero-forcing (CD-ZF) and minimum mean square error (MMSE) signal detection techniques for a better bit error rate (BER) were also implemented. The simulation results signify the effectiveness of the proposed system in terms of PLS enhancement with low correlation coefficients (14.62%, 7.61%, 13.61%, and 15.39% for users 1, 2, 3, and 4, respectively), an achievable secrecy rate with a low signal-to-interference and noise ratio (SINR) of the passive eavesdropper, an achievable out-of-band (OOB) power emission of 341 dB, an estimated average short-time Fourier transform (STFT) spectral power difference of 7.68 dB and estimated peak-to-average power ratios (PAPRs) ranging from 7 to 7.5 dB at a complementary cumulative distribution function (CCDF) of 1\times 10^-3 for different ground transmitting channels. At an identical signal-to-noise ratio (SNR) of 17 dB, all four users achieved a bit error rate of 1\times 10^-4 under RA channel coding, CD-ZF, and 16-QAM (quadrature amplitude modulation) digital modulation.