# Design of Covert Communication Waveform Based on Phase Randomization

## TL;DR

This paper introduces a new wireless communication system that hides data by making signals look like random noise, making it harder for unauthorized users to detect or intercept.

## Contribution

The novel contribution is the Noise-like Multi-Carrier Random Phase Communication System (NRPCS) that enhances communication secrecy through increased signal randomness.

## Key findings

- NRPCS significantly improves Low Probability of Detection (LPD) and Low Probability of Interception (LPI) compared to traditional methods.
- Unauthorized eavesdroppers cannot effectively demodulate NRPCS signals without knowing the modulation scheme.
- The system exhibits noise-like behavior through time-domain and spectral analyses.

## Abstract

Covert wireless communication is designed to securely transmit hidden information between two devices. Its primary objective is to conceal the existence of transmitted data, rendering communication signals difficult for unauthorized parties to detect, intercept, or decipher during transmission. In this paper, we propose a Noise-like Multi-Carrier Random Phase Communication System (NRPCS) to enhance covert wireless communication by significantly complicating the detection and interception of transmitted signals. The proposed system utilizes bipolar modulation and Cyclic Code Shift Keying (CCSK) modulation, complemented by a random sequence generation mechanism, to increase the randomness and complexity of the transmitted signals. A mathematical model of the NRPCS waveform is formulated, and detailed analyses of the system’s time-domain basis functions, correlation properties, and power spectral characteristics are conducted to substantiate its noise-like behavior. Simulation results indicate that, compared to traditional fixed-frequency transmission methods, NRPCS substantially improves both the Low Probability of Detection (LPD) and the Low Probability of Interception (LPI). Further research results demonstrate that unauthorized eavesdroppers are unable to effectively demodulate signals without knowledge of the employed modulation scheme, thus significantly enhancing the overall security of communication.