Time Modulation-Based Multi-User Covert Communication

Area of Science:

• Electrical Engineering
• Information Theory
• Signal Processing

Background:

• Multi-antenna systems enhance covert communication but increase complexity.
• Time-modulated arrays (TMA) offer low-complexity, energy-efficient covert communication using a single RF chain.
• Harmonics from TMAs cause signal leakage, aiding warden detection.

Purpose of the Study:

• To develop a warden's detection model for TMA-based covert communication.
• To analyze signal leakage characteristics and power distribution.
• To derive a computable upper bound for Kullback-Leibler (KL) divergence for covert constraint analysis.

Main Methods:

• Binary hypothesis testing model for warden detection.
• Derivation of a computable upper bound for KL divergence.
• Optimization problem formulation to maximize minimum covert transmission rate.
• Genetic algorithm (GA) for joint design of time modulation, power allocation, and spatial phase.

Main Results:

• Characterization of statistical properties and power distribution of harmonic-induced leakage.
• Effective suppression of signal leakage through the proposed scheme.
• Improved covert transmission performance and rates.

Conclusions:

• The proposed method effectively mitigates signal leakage in TMA-based covert communication.
• The genetic algorithm-based joint design optimizes system parameters for enhanced covertness and efficiency.
• This approach provides a viable solution for low-complexity, energy-efficient covert communication systems.