Symbol Waveform Hopping for Low-Intercept Secure Communications
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Solution Overview
Problem
Existing communication systems face challenges in securing data transmission with low probability of intercept and low probability of detection (LPI/LPD) due to advancements in signal processing capabilities of adversaries, necessitating enhanced security measures.
Innovation Solution
Implementing Symbol Waveform Hopping (SWH) by switching between multiple symbol waveforms in a data stream, using polynomial symbol waveforms (PSWs) with predetermined sequences known to the transmitter and receiver, to confuse potential adversaries about the modulation format.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional encryption and frequency-hopping spread spectrum are used, then data security is improved, but adversaries with advanced signal processing capabilities can still intercept and detect communications
Solution Approach 1:
The patent applies dynamics by making the modulation format dynamic rather than static. The system switches between multiple modulation formats (e.g., BPSK, QPSK, 8-PSK, 16-QAM) according to a pseudorandom sequence, causing the transmission characteristics to change continuously. This dynamic adaptation prevents adversaries from using fixed signal processing techniques to detect or intercept communications, as the signal properties vary over time according to the hopping sequence.
Solution Approach 2:
The patent implements parameter changes by varying key modulation parameters including the type of modulation (phase-shift, quadrature amplitude modulation), the number of symbols per constellation point, and the waveform characteristics. These parameter changes occur according to a pseudorandom sequence known to both transmitter and receiver, transforming the communication signal into a form that appears random to adversaries while maintaining decodability for authorized receivers.
2Reliability
If multiple modulation formats are switched during transmission, then low probability of intercept/detection is improved, but system complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-establishing a pseudorandom hopping sequence at both the transmitter and receiver before communication begins. This sequence determines the timing and selection of modulation format switches. By preparing this sequence in advance and ensuring both ends have identical copies, the system avoids the need for complex real-time negotiation or synchronization protocols during active transmission, reducing operational complexity while maintaining security.
3Difficulty of detecting and measuring
If symbol waveforms change randomly every symbol time, then adversary recognition difficulty is improved, but transmission performance stability may deteriorate
Solution Approach 1:
The patent carefully selects which modulation parameters to change and which to maintain. While the modulation format type (e.g., transitioning from BPSK to QPSK) and constellation size vary according to the hopping sequence, other critical parameters such as symbol rate, pulse shaping filter characteristics, and power normalization are kept consistent. This selective parameter change approach maintains transmission performance stability while achieving the desired recognition difficulty for adversaries.
Data Source
AI summary
Systems, devices, and methods of the present invention facilitate secure communication by changing sets of symbol waveforms used transmit data in particular symbol times defined herein as Symbol Waveform Hopping. SWH may be enabled by selecting two or more modulation formats that have sufficiently comparable communication performance (e.g., occupied bandwidth and signal power efficiency) to enable successful sending of data between a transmitter and receiver employing SWH, but characterized by symbol waveform alphabet that include different symbol waveform, so that the overall transmission/communication performance of data stream in a signal transmission channel of the system is not significantly affected by switching between modulation formats, but one symbol waveform alphabet is not reliably able to receive signals sent using the other alphabets. Some or all of the symbol waveforms in each alphabet may not be present in other alphabets.