Encrypted PPM Pulse Timing for Low-Power Secure Radio Links
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Solution Overview
Problem
Existing PPM signal transmission methods are vulnerable to eavesdropping and unauthorized decoding, and they consume high energy while requiring high processing speeds.
Innovation Solution
Implementing a method and device that encrypt PPM signals by time-shifting pulses based on predefined offsets known only to authorized receivers, using low-clock-speed microcontrollers and power-efficient oscillators, and incorporating encryption at the physical layer to secure communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PPM signals are transmitted using conventional encoding methods, then energy consumption is reduced through pulsed transmission, but security is compromised due to vulnerability to eavesdropping and unauthorized decoding
Solution Approach 1:
The patent applies preliminary action by pre-defining multiple temporal positions for pulses within each PPM symbol period and pre-establishing encryption keys for different receivers. The transmitter pre-encrypts the PPM signal by selecting specific temporal positions based on the encryption key, so that when the signal is transmitted, the authorized receiver can correctly interpret the pulse positions while unauthorized receivers cannot decode the information. This preliminary preparation of encryption schemes resolves the contradiction by enabling security without requiring complex real-time encryption processing.
Solution Approach 2:
The patent changes the temporal position parameter of pulses within the PPM signal as the encryption mechanism. Instead of using conventional encryption algorithms that require high processing speeds, the system encrypts information by varying which predefined temporal position a pulse occupies based on the encryption key. This parameter-based encryption approach maintains low energy consumption and simple device architecture while achieving reliable security, thus resolving the technical contradiction between security and device complexity.
2Adaptability or versatility
If multiple receivers are served by a single transmitter using conventional broadcasting, then coverage is improved, but security is worsened as any receiver can decode the signal
Solution Approach 1:
The patent applies segmentation by dividing the PPM signal into multiple segments, each with pulses at different predefined temporal positions that correspond to different encryption keys. Each authorized receiver is assigned a specific encryption key that enables it to correctly interpret pulses at particular temporal positions. This segmentation allows a single transmitter to securely serve multiple receivers simultaneously, as each receiver can only decode segments encrypted with its assigned key, thus resolving the contradiction between multi-receiver capability and signal security.
Solution Approach 2:
The patent implements universality by designing a single PPM transmitter that can generate encrypted signals for multiple different receivers using the same hardware architecture. The transmitter contains a set of predefined temporal positions and can switch between different encryption schemes based on which receiver is the intended target. This multi-functional capability allows one transmitter to serve multiple receivers securely without requiring separate transmitters for each receiver, resolving the contradiction between adaptability and security.
3Reliability
If encryption is implemented at higher protocol layers, then security is achieved, but energy consumption increases and processing speed requirements increase
Solution Approach 1:
The patent replaces complex cryptographic processing with a simpler temporal position selection mechanism. Instead of using conventional encryption algorithms that require intensive computational operations and high processing speeds, the system encrypts PPM signals by selecting from a set of predefined temporal positions based on a simple key lookup. This substitution of mechanical/computational complexity with temporal positioning logic dramatically reduces energy consumption while maintaining security, resolving the contradiction between security and energy usage.
Solution Approach 2:
The patent utilizes the periodic structure of PPM signals by defining multiple predefined temporal positions within each symbol period. The encryption mechanism periodically selects from these predefined positions based on the encryption key, aligning with the natural periodicity of the PPM modulation scheme. This approach leverages the existing periodic action of the communication protocol to implement security without adding extra processing steps, thereby maintaining low energy consumption while achieving reliable security.
Data Source
AI summary
Methods and devices for the communication of encrypted PPM signals for a radio communication system. There is a step of PPM encoding of an information item to be transmitted in which each symbol of an alphabet of symbols used to compose the information item to be transmitted is assigned a respective predefined temporal position of one pulse with respect to the preceding pulse of an original sequence of PPM pulses. There is a step of encryption, particularly at the physical layer, wherein at least one of the pulses of the transmitted sequence is time-shifted, according to a corresponding offset that is known only to authorized receivers, with respect to its predefined temporal position in the original sequence. The offset is such that the time-shifted pulse is not located, with respect to the pulse that precedes it, in any of the predefined temporal positions that are provided in the PPM encoding.