Acoustic Spread Spectrum Proximity Pairing
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Solution Overview
Problem
Proximity pairing of endpoint devices in room environments is challenging due to the extreme multi-path nature of acoustic signals, leading to unreliable or inappropriate pairing, as direct path sound is often 20 dB below reverberant sound, making traditional communication methods unreliable.
Innovation Solution
The use of acoustic spread spectrum communications, specifically employing Prometheus Orthonormal Set (PONS) codes for generating pilot and data sequences, allows for reliable token exchange and ranging information derivation, enabling accurate pairing by computing separation distance based on time differences in transmit and receive times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional acoustic communication methods are used, then the system is simple, but reliability deteriorates due to multi-path interference and reverberation
Solution Approach 1:
The patent transforms traditional narrowband acoustic signals into wideband spread spectrum signals by modulating with pseudorandom codes. This changes the spectral parameters of the signal, distributing energy across a wider frequency range, which provides robustness against multipath interference and reverberation while maintaining communication reliability in challenging acoustic environments.
Solution Approach 2:
The patent introduces a temporal dimension to frequency-domain communication by using time-varying spread spectrum codes. The signal is spread across both time and frequency, creating a two-dimensional signal structure that allows the receiver to distinguish between direct and reflected paths through cross-correlation processing, thereby improving reliability without requiring complex spatial filtering.
2Area of stationary object
If acoustic signals are transmitted over long distances, then coverage area increases, but signal strength deteriorates due to path loss and reverberation
Solution Approach 1:
The patent employs periodic transmission of pilot sequences and data sequences at regular intervals. This periodic structure allows the receiver to accumulate energy over multiple cycles and use correlation processing to distinguish the transmitted signal from reverberation, enabling reliable communication at extended distances where direct path signal strength would otherwise be insufficient.
Solution Approach 2:
The patent maintains continuous transmission of spread spectrum signals with persistent pilot and data sequences. This continuous action allows the receiver to continuously track the signal and maintain synchronization over extended periods and distances, overcoming the fading and attenuation effects that would otherwise limit coverage area while maintaining adequate signal strength.
3Adaptability or versatility
If proximity pairing is performed in reverberant rooms, then functionality is achieved, but pairing accuracy deteriorates due to multi-path interference
Solution Approach 1:
The patent implements feedback mechanisms where endpoint devices exchange tokens and measure the time difference of arrival (TDOA) of acoustic signals. This feedback loop allows the system to continuously adjust and refine distance measurements, compensating for multipath interference and achieving accurate proximity pairing even in reverberant environments where traditional methods would fail.
Solution Approach 2:
The patent performs preliminary token exchange and signal transmission before final pairing decision. By pre-establishing communication channels and measuring signal characteristics in advance, the system can filter out spurious signals and identify genuine direct paths, ensuring high pairing accuracy while maintaining full proximity pairing functionality in challenging acoustic environments.
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
This approach effectively overcomes room reverberation and multi-path issues, ensuring reliable pairing of endpoint devices by using spread spectrum gain and zero-autocorrelation-zone properties of PONS codes, even in highly reverberant environments, allowing for secure channel establishment and accurate distance calculation.
Implementation Method 1
The present disclosure relates to proximity pairing of endpoints using acoustic spread spectrum communications
Implementation Method 2
specifically employing Prometheus Orthonormal Set (PONS) codes for generating pilot and data sequences
Implementation Method 3
using spread spectrum gain and zero-autocorrelation-zone properties of PONS codes
Implementation Method 4
computing a separation distance between the first endpoint device and the second endpoint device based on a time difference between the transmit time and the receive time
Data Source
AI summary
A first endpoint generates an acoustic spread spectrum signal including a pilot sequence and a data sequence representing a token synchronized to the pilot sequence, transmits the acoustic spread spectrum signal, and records a transmit time at which the acoustic spread spectrum signal is transmitted. A receive time at which a second endpoint received the acoustic spread spectrum signal transmitted by the first endpoint is received from the second endpoint along with an indication of a second token as recovered from the received acoustic spread spectrum signal by the second endpoint. A separation distance between the first endpoint and the second endpoint is computed based on a time difference between the transmit time and the receive time. The first endpoint is paired with the second endpoint when the token matches the second token and the computed distance is less than a threshold distance.