Artificial-Noise-Aided Secure Transmission with Directional Modulation based on Random Frequency Diverse Arrays (1612.06649v1)

Abstract: In this paper, we propose a novel directional modulation (DM) scheme based on random frequency diverse arrays with artificial noise (RFDA-DM-AN) to enhance physical layer security of wireless communications. Specifically, we first design the RFDA-DM-AN scheme by randomly allocating frequencies to transmit antennas, thereby achieving two-dimensionally (i.e., angle and range) secure transmissions, and outperforming the state-of-the-art one-dimensional (i.e., angle) phase array (PA) based DM scheme. Then we develop the closed-form expression of a lower bound on the ergodic secrecy capacity (ESC) of our RFDA-DM-AN scheme. Based on the theoretical lower bound derived, we further optimize the transmission power allocation between the useful signal and artificial noise (AN) in order to enhance the ESC. Simulation results show that 1) our RFDA-DM-AN scheme achieves a higher secrecy capacity than that of the PA based DM scheme, 2) the lower bound derived is shown to approach the ESC as the number of transmit antennas N increases and precisely matches the ESC when N is sufficiently large, and 3) the proposed optimum power allocation achieves the highest ESC compared with other power allocations in the RFDA-DM-AN.

• The paper introduces the RFDA-DM-AN scheme, which enhances physical layer security through two-dimensional angle and range discrimination using random frequency allocation.
• The proposed RFDA-DM-AN scheme achieves higher secrecy capacity compared to phased arrays and optimizes power allocation for maximum security.
• Analysis shows the RFDA-DM-AN scheme is scalable with antenna array size and has potential applications in next-generation wireless networks like IoT and vehicular systems.

Artificial-Noise-Aided Secure Transmission with Directional Modulation Based on Random Frequency Diverse Arrays

This paper introduces an innovative approach to enhancing physical layer security in wireless communications through a novel scheme referred to as Artificial-Noise-Aided Secure Transmission with Directional Modulation based on Random Frequency Diverse Arrays (RFDA-DM-AN). The methodology elaborated in this paper significantly differentiates from traditional phased arrays by introducing randomness in frequency allocation, thus achieving a two-dimensional secure transmission by enhancing both angular and range discrimination.

Key Contributions

The RFDA-DM-AN scheme is designed by randomly allocating frequencies across transmit antennas, forming a transmission pattern that is secure in both the angle and range dimensions. This contrasts the conventional one-dimensional phase array (PA) directional modulation techniques, which only focus on angular discrimination. Several salient points are worth highlighting:

1. Secrecy Capacity Enhancement: The RFDA-DM-AN scheme demonstrates a higher secrecy capacity compared to PA based directional modulation. The paper derives a lower bound on the ergodic secrecy capacity (ESC) of the proposed method, showing its superiority numerically and through theoretical deductions.
2. Power Allocation Optimization: By optimizing the transmission power between the useful signal and artificial noise, the RFDA-DM-AN achieves the highest ESC. This optimization is critical because it enables the scheme to maximize the signal-to-noise ratio (SNR) for the intended receiver while minimizing the possibility of eavesdropping at other directions and ranges.
3. Scalability with Antenna Array Size: The analysis reveals that as the number of transmit antennas increases, the lower bound on the ESC closely approximates the actual ESC, validating the scheme’s scalability and efficiency in large antenna arrays.
4. Frequency Allocation Strategies: The paper examines both continuous and discrete frequency allocation strategies. It is found that continuous uniform frequency allocation results in a higher average ESC compared to discrete allocation, offering insights into practical implementation preferences.

Implications and Future Directions

The implications of this research extend across both theoretical and applied dimensions. Theoretically, the RFDA-DM-AN approach offers a new perspective on employing random frequency diversity to decouple angle and range correlations, a significant advancement over existing linear frequency diverse arrays (LFDA) and phased arrays. Practically, the ability to secure wireless communications effectively without needing precise eavesdropper location information is particularly attractive in scenarios where eavesdroppers are passive and undetectable.

Furthermore, as the RFDA-DM-AN scheme allows dynamic and robust secure transmissions, it has potential applications in next-generation wireless networks, particularly in IoT and vehicular network scenarios where security is paramount. Also, the scalability of the proposed approach makes it a promising candidate for implementations in massive MIMO systems.

Potential future research directions could focus on exploring the trade-offs between randomness in frequency allocation and computational complexity, the impacts of the proposed technology in realistic multi-hop networks, and its integration with other evolving secure communication protocols. As RF technologies advance, incorporating hardware-based innovations to further enhance this security framework could be an exciting area for ongoing investigation.