Abstract
The security issue on the physical layer is of significant challenge yet of paramount importance for 5G communications. In some previous works, transmit power allocation has already been studied for orthogonal frequency division multiplexing (OFDM) secure communication with Gaussian channel inputs for both a single user and multiple users. Faced with peak transmission power constraints, we adopt discrete channel inputs (e.g., equiprobable Quadrature Phase Shift Keying (QPSK) with symmetry) in a practical communication system, instead of Gaussian channel inputs. Finite-alphabet inputs impose a more significant challenge as compared with conventional Gaussian random inputs for the multiuser wiretap OFDM systems. This paper considers the joint resource allocation in frequency-domain artificial noise (AN) assisted multiuser wiretap OFDM channels with discrete channel inputs. This security problem is formulated as nonconvex sum secrecy rate optimization by jointly optimizing the subcarrier allocation, information-bearing power, and AN-bearing power. To this end, with a suboptimal subcarrier allocation scheme, we propose an efficient iterative algorithm to allocate the power between the information and the AN via the Lagrange duality method. Finally, we carry out some numerical simulations to demonstrate the performance of the proposed algorithm.
Highlights
Recent years have witnessed the rapid development of various 5G communication technologies provided with the high data rate
Since the redundancy is provided by the asymmetry between the filter shapes for the legitimate transmitter (LT) and the legitimate receiver (LR), we further consider the time slotted orthogonal frequency-division multiplexing (OFDM) symbols by assuming that the wireless channel remains constant over each time slot, but can vary from one-time slot to another
The channel coefficients only consist of small-scale fading, which is modeled as Rayleigh fading
Summary
Recent years have witnessed the rapid development of various 5G communication technologies provided with the high data rate. Symmetry 2019, 11, 855 which one LT could reliably send a secret message to one LR while keeping one PE unable to obtain any information Based on these works, various advanced techniques, such as beamforming, precoding, power allocation, and artificial noise design, have been developed to achieve the secrecy rate in multiple-input-multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems (see, e.g., [16,17,18,19]). Different from the Gaussian inputs [29], we develop a frequency-domain AN methodology with finite-alphabet symbols to jointly optimize the SC allocation and the power allocation of information signals and AN signals. System, including one legitimate transmitter (LT), K legitimate receivers (LRs) and one passive eavesdropper (PE)
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