Microwave Link Physical-Layer Security Using Beamformed Noise

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Solution Overview

Problem

Microwave radio links are vulnerable to eavesdropping due to their directional nature, making it difficult to secure data transmission against potential attackers, especially with the threat of quantum computers compromising classical cryptography.

Innovation Solution

Implementing additional noise components on the physical layer of microwave links to enhance security, using methods like Physical Layer Security (PLS) and quantum-safe cryptography, ensuring the legitimate receiver has better reception quality than potential eavesdroppers, and dynamically adjusting transmission parameters to counter eavesdropping attempts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If encryption techniques are used to secure microwave radio links, then communication security is improved, but quantum computers may compromise this security in the future

Engineering Contradiction:
Improvecommunication securityVSAvoidresistance to quantum computing threats
Core Design Contradiction:
ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent segments the security approach into two layers: physical layer security (PLS) using noise components and directional beamforming, and cryptographic encryption. This segmentation allows the system to combine immediate physical layer protection with cryptographic security, creating a defense that is resilient to quantum computing threats that may break traditional encryption.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent applies preliminary action by inserting noise components into the signal at the physical layer before transmission. This pre-established physical layer security creates a foundation that protects against eavesdropping independently of cryptographic methods, ensuring security even before quantum computers become a practical threat to encryption.

Inventive Principle:
Principle #10Preliminary action

2Reliability

If additional noise components are inserted into the message, then eavesdropping protection is improved, but signal quality for the legitimate receiver may deteriorate

Engineering Contradiction:
Improveeavesdropping protectionVSAvoidsignal quality
Core Design Contradiction:
ReliabilityVSMeasurement precision

Solution Approach 1:

The patent applies local quality by creating different signal conditions for different spatial locations. The legitimate receiver located within the narrow directional beam experiences high signal quality, while potential eavesdroppers outside the beam experience degraded signal quality due to the combination of directional attenuation and inserted noise components. This spatial differentiation allows security improvement without compromising legitimate communication quality.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent changes the parameter of signal composition by inserting noise components with specific characteristics that are removable by the legitimate receiver through knowledge of the insertion process. The noise is designed to degrade eavesdropping attempts while maintaining recoverable signal quality for authorized receivers through parameter-based signal processing.

Inventive Principle:
Principle #35Parameter changes

3Productivity

If the microwave antenna beam is focused into a narrow band, then transmission distance and data rate are improved, but eavesdropping possibilities within the beam area increase

Engineering Contradiction:
Improvedata transmission rateVSAvoideavesdropping risk
Core Design Contradiction:
ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful effect of concentrated energy in a narrow beam into a benefit by using the same directional focusing to create a security mechanism. The narrow beam, which could be exploited for eavesdropping, becomes a security feature because inserting noise into this concentrated beam creates a situation where only receivers within the beam can achieve sufficient signal quality, while external eavesdroppers experience degraded signals despite the beam's concentration.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentEP4668814A1Methods, apparatuses and computer programs for a transmitter and a receiver and for securing a radio link, transmitter, receiver, relay station, radio system
Publication Date: 2025.12.24 DEUTSCHE TELEKOM AG
  • EP4668814A1 patent drawingFigure 1
  • EP4668814A1 patent drawingFigure 2
  • EP4668814A1 patent drawingFigure 3

AI summary

The present disclosure relates to methods, devices, and computer programs for a transmitter and a receiver and for securing a microwave link, a transmitter, a receiver, a relay station, and a microwave link system. The method (10) for a transmitter (300) and for securing a microwave link between the transmitter (300) and a receiver (400) in a microwave link system (500) comprises aligning (11) a microwave antenna beam such that the receiver (400) is located in a main direction of radiation of the antenna beam and inserting (12) on the physical layer additional noise components into a message for the receiver (400) in order to obtain a protected message for the receiver (400). The method further comprises transmitting (13) the protected message to the receiver (400) via the antenna beam.