The authors incorporate Alamouti space-time block coded orthogonal frequency division multiplexing (OFDM) with signal space diversity (SSD) in order to significantly strengthen the physical layer security of the communication network. The coordinate interleaving step of SSD is performed amongst OFDM subcarriers, according to distinct strategies that make the correlation coefficients between the subcarrier channel gains equal to zero. The proposed system model can improve the security by enabling a legitimate user to have much less error than an eavesdropper, even under the worst-case scenario where the unauthorised receiver somehow captures the interleaving strategy compromised by the transmitter and legitimate receiver. It is shown that a legitimate user with the introduced scheme can provide up to 14% more performance gain as compared to an unauthorised receiver for a bit error rate (BER) of 10 −4 under worst-case scenarios with different parameters. An exact closedform expression of the BER is derived for the legitimate user and shown to match with the simulation results. Finally, it is demonstrated that the system is also capable of enhancing the resistance against channel estimation errors at the receiver. The proposed system does not require high complexity or additional bandwidth or time resources.

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We combine multiple-input multiple-output zero-forcing receive beamforming (ZFRBF) with time and spatial component interleaved signal space diversity (SSD) and analyze the system’s error performance and implementation complexity. A transreceiver system with two transmit and [Formula: see text] ([Formula: see text]) receive antennas is considered where the number of simultaneous substreams equals two. The error performance of the proposed scheme with binary phase-shift keying (BPSK) and quadrature phase-shift keying (QPSK) modulations is studied. Under the time component interleaved SSD case, we derive an exact average bit error probability expression for BPSK and a tight approximation on the average symbol error probability for QPSK. The signal constellation rotation angles are accordingly computed. Using a similar approach, the signal constellation rotation angles are also determined for the scenario of spatial component interleaved SSD. It is demonstrated that the performance of the original ZFRBF model can be improved significantly by utilizing SSD especially with the time interleaving method. Another contribution to the literature is to study hardware complexity of the proposed scheme on FPGA. It is shown that while achieving considerable performance gain, SSD introduces only an insignificant increase to the system complexity without any extra bandwidth or time slot usage.

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