Dispersive Filter Physical Layer Encryption
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Solution Overview
Problem
Current wireless communication security methods, particularly in the physical layer, are inadequate in protecting the air interface parameters such as modulation schemes from eavesdropping and interception, as they do not effectively secure the modulation scheme and phase components of RF signals.
Innovation Solution
A method involving a dispersive signal filter that alters the phase profile of data signals by introducing distortion, creating a unique non-linear phase spectrum that conceals the true modulation parameters, allowing only authorized receivers with a corresponding decrypting filter to recover the original signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional encryption techniques (scrambling, shared data encryption keys) are used at higher layers, then data security is improved, but air interface parameters such as modulation scheme remain susceptible to eavesdropping and interception
Solution Approach 1:
The patent segments the security protection into two distinct layers: upper layer data encryption (using conventional techniques) and physical layer parameter encryption (using the dispersive filter). This segmentation allows each layer to address specific security concerns - data content protection and modulation scheme protection respectively - thereby resolving the contradiction between data security and air interface parameter security.
Solution Approach 2:
The patent introduces a dispersive signal filter as an intermediary component at the physical layer that encrypts modulation parameters by altering their phase profiles. This intermediary operates independently from the conventional data encryption layer, providing an additional security mechanism that specifically protects air interface parameters from eavesdropping while maintaining compatibility with existing data encryption techniques.
2Object-affected harmful factors
If directional modulation or beam forming transmitters are used, then interception chance is reduced, but device complexity increases due to specific beam forming requirements
Solution Approach 1:
The patent replaces the complex mechanical beam forming system with a signal processing-based dispersive filter approach. Instead of using hardware-intensive directional modulation and beam forming transmitters, the invention uses a mathematical filter (dispersive filter) that achieves similar security goals by altering phase profiles in the frequency domain, thereby reducing device complexity while maintaining security effectiveness.
Solution Approach 2:
The patent changes the security mechanism from spatial parameter manipulation (directional modulation, beam forming) to phase parameter manipulation (dispersive filtering in frequency domain). By changing from modifying signal direction to modifying phase profiles, the system achieves interception resistance through simpler signal processing operations rather than complex hardware beam forming.
3Reliability
If DFT S OFDM is used for physical layer security, then security is improved, but peak-to-average power ratio increases leading to linearity and power efficiency trade-off problems
Solution Approach 1:
The patent changes the modulation approach from DFT S OFDM (which has high PAPR) to a dispersive filtering approach applied to standard modulation schemes. By operating in the frequency domain to modify phase profiles rather than using high-PAPR waveforms, the system maintains physical layer security while improving power efficiency and avoiding linearity constraints associated with high peak power signals.
Data Source
AI summary
Disclosed is a method of encrypting a data signal for providing to an input of a radio frequency transmitter, such as modulated baseband signals in the physical layer for wireless transmission. The method comprises receiving the data signal comprising one or more first frequency components with a first phase profile in a frequency band of interest; applying a dispersive encrypting signal filter to the data signal to generate an encrypted data signal comprising the one or more frequency components with a second phase profile, wherein the second phase profile is different to the first phase profile. Decryption is achieved by applying a decrypting filter to the encrypted data signal to substantially reverse the effect of the encrypting filter and recover the first phase profile.