In this paper, multi-antenna transceiver for zero-padded orthogonal frequency division multiplexing (OFDM) system is designed at mmWave by integrating full-duplex unmanned aerial vehicle (UAV) into the terrestrial cellular networks. Assuming that there exist no direct communication links between the ground base station (GBS) and the mobile users due to unexpected blockages from high storied buildings in urban area, the UAV applies decode-and-forward cooperative strategy on the received OFDM signals transmitted from GBS and re-transmits to the ground mobile users and passive eavesdropper. In this proposed system, intertwining logistic map (ILM)-cosine transform aided encryption algorithm combined with artificial noise enhancing physical layer security (PLS) is introduced. Also walsh-hadamard transform technique integrated with QR-decomposition based zero forcing (ZF) block diagonalization (QR-ZF-BD) precoding for multi-user interference reduction and non-iterative clipping and filtering technique for peak to average power ratio (PAPR) reduction are utilized. In addition, Low density parity check (LDPC) and repeat and accumulate (RA) channel coding with cholesky decomposition based ZF and minimum mean square error signal detection schemes for improved bit error rate (BER) are also introduced. Numerical results demonstrate the effectiveness of the proposed system in terms of PLS for color image transmission at high order digital modulation . At the complementary cumulative distribution function of probability level 1-6%, the estimated PAPR is found to have value of 6 dB.The three users achieve BER = 1 × 10 −4 at signal-to-noise ratio of 1.5 dB, 4 dB and 6 dB under RA channel coding and 16-QAM digital modulation.INDEX TERMS Bit error rate, channel coding, peak to average power ratio, physical layer security encryption, signal-to-noise ratio, zero-padded orthogonal frequency division multiplexing.

Unmanned aerial vehicle (UAV)-based communication system design has already attracted substantial interest due to UAV flexibility in deployment, cost effectiveness, and in-built line-of-sight air-toground channels. However, there is a persistent issue of security threats associated with the broadcast nature of UAV: physical layer security (PLS) can be introduced to enhance the secrecy performance in that regard.In the system proposed here, the combined effect of 3D fractional-order Liu chaotic system and 3D fractionalorder Li chaotic system is introduced to enhance the PLS of the UAV-to-ground communication network. In addition, to reduce multi-user interference (MUI), efficient orthogonal variable spreading factor (OVSF) codes are integrated with a zero forcing (ZF) scheme. Moreover, to improve bit error rate (BER), a combined MUI signal discrimination and ZF signal detection scheme is introduced, strengthened by various channel coding techniques with multi-user beamforming weighting. The numerical outcomes establish the efficacy of the proposed system in terms of PLS and improvement of data rate with signal-to-interference-plus-noise ratio. This approach achieved an out-of-band emission reduction of 119 dB. Furthermore, an improved BER of 1 × 10 −4 is achieved in 16-QAM for a signal-to-noise ratio of 6 dB.INDEX TERMS Millimeter-wave, orthogonal frequency-division multiplexing, orthogonal variable spreading factor, overlap-windowed discrete Fourier transform, physical layer security, unmanned aerial vehicle, zero forcing precoding.

In this paper, we investigate the performance of a single-relay cooperative wireless communication system with implementation of Orthogonal Frequency division multiplexing technique under Amplifyand-Forward (AAF) and Decode-and-Forward (DAF) relaying protocols on color image transmission. The system under investigation incorporates four conventional signal combining schemes such as Equal Ratio Combining (ERC) and Fixed Ratio Combining (FRC), Signal to Noise Ratio Combining (SNRC) and Enhanced Signal to Noise Ratio Combining (ESNRC) under BPSK and QPSK digital modulations. In the present study, results of BER simulation in AWGN and Raleigh fading channels shows that the system outperforms in ERC combining scheme as compared to others (FRC, SNRC and ESNRC) under BPSK digital modulation and AAF relaying protocol. It is observed that a quite

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