IRS-Assisted Covert Wireless Links Using Friendly Jamming
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Solution Overview
Problem
Existing covert communication techniques for intelligent reflecting surface-assisted wireless networks face challenges in controlling noise uncertainty and optimizing transmission strategies to ensure covertness and maximize achievable rates, especially when instantaneous channel information is unavailable.
Innovation Solution
A novel covert communication method using a friendly jammer and intelligent reflecting surface (IRS) that optimizes transmission probability, transmit power, and reflection matrix to enhance the achievable rate at a client while ensuring covertness, employing one-dimensional line search methods to reduce computational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional covert communication methods optimize transmission probability at an agent, then the achievable rate at a client is improved, but the covertness requirement cannot be satisfied due to noise uncertainty
Solution Approach 1:
An intelligent reflecting surface (IRS) is introduced as an intermediary component to reflect and redirect radio frequency signals between the agent and client. The IRS comprises multiple programmable elements that can independently adjust phase and amplitude, creating a controllable reflection path that enhances signal strength for legitimate communication while maintaining covertness against adversaries who cannot control or predict the IRS reflections.
Solution Approach 2:
The system dynamically adjusts multiple parameters including transmission probability at the agent, transmit power levels, IRS reflection coefficients (phase and amplitude for each element), and jamming power. By optimizing these parameters jointly, the system achieves near-optimal covert communication performance that satisfies both achievable rate and covertness requirements despite noise uncertainty at the adversary side.
2Reliability
If a friendly jammer is introduced to confuse the adversary, then the covertness is improved, but the computational complexity increases
Solution Approach 1:
Instead of optimizing all possible parameters simultaneously, the system employs a two-stage approach: first optimizing the IRS reflection coefficients to maximize signal strength at the client, then optimizing the jamming power and transmission probability. This partial optimization sequence reduces computational complexity while achieving near-optimal covert communication performance.
Solution Approach 2:
The optimization problem is segmented into separate sub-problems: (1) IRS reflection matrix optimization, (2) jamming power optimization, and (3) transmission probability optimization. Each sub-problem is solved independently using appropriate algorithms, reducing the overall computational burden compared to joint optimization of all parameters simultaneously.
3Productivity
If instantaneous channel information is used for optimization, then the achievable rate is maximized, but the system becomes vulnerable to detection by the adversary
Solution Approach 1:
The system performs preliminary channel estimation and statistics collection during idle periods or through pilot signals before actual covert communication begins. The IRS reflection coefficients are pre-optimized based on channel statistics rather than instantaneous channel states, allowing the system to achieve good performance while avoiding detection since the adversary cannot observe the pre-computed reflection patterns.
Solution Approach 2:
Instead of using instantaneous channel information that would be detected by adversaries, the system uses statistical channel information (mean and covariance) as a copy or approximation of the actual channel states. This statistical approach maintains achievable rate performance while ensuring covertness since the statistics do not reveal real-time communication conditions.
4Reliability
If joint optimization of transmission probability, power, and reflection matrix is performed, then the covert performance is improved, but the computational overhead increases
Solution Approach 1:
The system employs dynamic optimization where the IRS reflection coefficients are adjusted in real-time based on channel conditions, while transmission probability and power levels are optimized at a slower timescale. This dynamic approach allows the system to adapt to changing conditions while reducing computational overhead by not re-optimizing all parameters at every time instant.
Solution Approach 2:
The optimization is performed in stages with varying levels of detail: IRS reflection coefficients are optimized with fine granularity, while transmission probability and power are optimized with coarser granularity. This partial optimization approach achieves near-optimal covert performance with significantly reduced computational overhead compared to full joint optimization.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method achieves near-optimal performance with low computational complexity by optimizing transmission strategies using statistical channel information, providing secure communication links with enhanced covertness and increased data rates.
Implementation Method 1
providing an intelligent reflecting surface (IRS) to reflect wireless radio frequency (RF) communication signals transmitted from the agent device to the client device
Implementation Method 2
providing a jamming device which radiates jamming signals with random power to confuse the adversary device in detecting the existence of the communication
Data Source
AI summary
We disclose a novel methodology and wireless network for covert wireless RF communications between an agent device and a client device in the presence of an adversary device which attempts to detect the existence of the transmission of the RF communication between the agent and client. The methodology comprises: providing an intelligent reflecting surface (IRS) to reflect wireless radio frequency (RF) communication signals transmitted from the agent device to the client device, the IRS comprising a two-dimensional array of individually controllable RF reflecting elements; providing a jamming device which radiates jamming signals with random power to confuse the adversary device in detecting the existence of the communication between the agent device and the client device; and establishing a covert RF communication link between the agent device and the client device using the IRS that optimizes the transmission probability, transmit power at an agent, and the reflection matrix of an IRS for covert RF communications.