Abstract
In this paper, we research synthesis scheme for secure wireless communication in multibeam directional modulation (MBDM) system, which consists of multiple legitimate users (LUs) receiving their own individual confidential messages, respectively, and multiple eavesdroppers (Eves) intercepting confidential messages. We propose a new type of array antennas, termed frequency diverse arrays (FDA), to enhance security of confidential messages. Leveraging FDA technology and artificial noise (AN) technology, we aim to address the PHY security problem for MBDM by jointly optimizing the frequency offsets, the precoding matrix and the AN projection matrix. In the first stage, with known locations of Eves, precoding matrix is designed to minimize Eve’s receiving power of confidential message (Min-ERP), while satisfying power requirement of LUs. And then artificial-noise projection matrix (ANPM) is calculated to enhance AN impact on Eves without influencing LUs. Furthermore, we research a more practical scenario, where locations of Eves are unknown. Unlike the scenario of the known locations of Eves, precoding matrix is designed to maximize AN transmit power (Max-ATP), while satisfying each LU’s requirement received power of confidential message. In the second stage, we analyze and further optimize secrecy capacity. The problem is solved by optimizing frequency offsets through modified artificial bee colony (M-ABC) algorithm. Numerical results show that the proposed scheme can achieve a secure transmission in MBDM system.
Highlights
Wireless communication systems have gained considerable growth rate due to its merits, such as flexibility and convenience
The main contributions of our work are as follows: (1) We extend secure wireless communications based on frequency diverse arrays (FDA) from previous point-to-point communication to multibeam directional modulation (MBDM) system
In this paper, we propose a modified artificial bee colony (M-artificial bee colony (ABC)) algorithm that combines the global optimal solution idea of particle swarm optimization algorithm and crossover operation of genetic algorithm on the basis of ABC algorithm to obtain the time-invariant optimal frequency offsets, which further maximize the secrecy capacity of MBDM system
Summary
Wireless communication systems have gained considerable growth rate due to its merits, such as flexibility and convenience. The secure wireless communication includes two aspects: preventing confidential message from being received by undesired LUs and minimizing the leakage of all confidential messages from transmitter to Eves To address these secure problems, AN-based synthesis scheme combined with FDA is employed. The proposed scheme achieves multiuser secure wireless communication in practical application scenario with unknown locations of Eves (2) We design new optimization methods with known/unknown locations of Eves These methods achieve secure multibeam wireless communication while improving the utilization of total transmit power (3) We judiciously design the AN projection matrix to maximize the interference caused by AN to Eves, which makes Eves harder to decipher the confidential messages (4) The scheme-based R-FDA can achieve a good secrecy performance, but it cannot guarantee the maximum secrecy capacity due to its frequency randomness.
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