Secure UWB Channel Sounding via Pseudo-Random Code Sets
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Solution Overview
Problem
In ultra-wideband (UWB) communication systems, existing channel sounding methods face challenges in maintaining accuracy while allowing asymmetric delays without significantly reducing performance, particularly due to the vulnerability of Ipatov codes with perfect periodic auto-correlation, which are compromised when codes are changed for each symbol, leading to increased estimation sequence lengths and sidelobe issues.
Innovation Solution
A method that generates a pseudo-random code set for both transmitter and receiver, using techniques like GCP Sync, CLASS, and LCSSS to develop channel correlations and estimates, which involve generating code sets with low correlation sidelobes, ensuring accurate channel estimation without compromising on sequence length or accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Ipatov codes with perfect periodic auto-correlation are used for channel sounding, then channel estimation accuracy is improved, but security is compromised because the codes are predictable and periodic
Solution Approach 1:
The patent changes the fundamental parameter of the code sequence from deterministic Ipatov codes to pseudo-random sequences generated by linear feedback shift registers (LFSR). This transformation maintains the mathematical properties needed for correlation-based channel estimation while eliminating the predictability and periodicity that compromised security. The pseudo-random nature of LFSR-generated sequences provides security through unpredictability while preserving the auto-correlation properties necessary for accurate channel sounding.
2Reliability
If codes are changed for each symbol to remove vulnerability, then security is improved, but estimation sequence length increases and sidelobe issues arise
Solution Approach 1:
The patent changes the code generation approach from using different codes for each symbol to using a single pseudo-random sequence that is shifted in time for each symbol. This LFSR-based approach maintains code security through pseudo-randomness while keeping the sequence length manageable. The mathematical properties of LFSR sequences ensure that the auto-correlation function has a sharp peak with low sidelobes, enabling accurate channel estimation without requiring excessively long sequences.
3Reliability
If codes are changed for each symbol, then predictability is reduced, but auto-correlation function develops sidelobes that do not cancel out
Solution Approach 1:
The patent changes from using arbitrary different codes for each symbol to using pseudo-random sequences from an LFSR with specific mathematical properties. These sequences are designed to have optimal auto-correlation characteristics with low sidelobes. The pseudo-random nature provides unpredictability while the mathematical structure of LFSR sequences ensures that the auto-correlation function maintains a sharp peak with minimal sidelobes, resolving the contradiction between predictability and auto-correlation quality.
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 proposed method achieves channel estimation with reduced sidelobe distortion, allowing for shorter symbol lengths and improved accuracy, comparable to best prior art techniques, while maintaining security through pseudo-random code generation and correlation techniques.
Implementation Method 1
A pseudo-random code set is generated using a cryptographic seed value
Implementation Method 2
The receiver correlates the received signal with local code sequences to estimate the channel impulse response
Data Source
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AI summary
In an ultra-wideband ("UWB") communication system comprising a pair of UWB transceivers, methods for securely performing channel sounding. In a first GCP Sync method, a pre-determined set of Golay Complementary Pairs is added to an 802.15.4a frame. In a second CLASS method, a cyphered low auto-correlation sum set is added to frame. In a third LCSSS method, a low cross-correlation sidelobe sum set is added to the frame. In general, these methods are adapted to transmit a pseudo-randomly generated codeset which may have inherent sidelobe distortions, and then, in the receiver, to compensate for this, and any channel-induced, distortion by selectively modifing the cross-correlation codeset.