Low Correlation Signal Formats for Spectrum Sharing
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Solution Overview
Problem
Existing techniques for sharing the frequency spectrum, such as Detect and Avoid (DAA), are ineffective in allowing secondary users to use licensed bands reserved for primary users, and do not provide sufficient access to licensed bands, leading to interference issues when transmitting new signals.
Innovation Solution
Developing new signal formats with characteristics that have low correlation with existing signals, such as modulation schemes and code sequences, to enable secondary users to transmit without disrupting existing signals, even in licensed or unlicensed spectrum, by analyzing the properties and parameters of the existing signals and receivers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Detect and Avoid (DAA) techniques are used to monitor channels before transmission, then interference with existing signals is prevented, but the available spectrum for secondary users is severely limited and access to licensed bands is insufficient
Solution Approach 1:
The patent changes the signal parameters (modulation scheme, code sequence, symbol rate) of secondary users to create signals with low correlation to existing primary user signals. This allows secondary signals to coexist in the same frequency band without corrupting primary signal reception, thereby resolving the contradiction between interference prevention and spectrum access.
Solution Approach 2:
The patent introduces signal correlation analysis as an intermediary mechanism to determine whether a channel is suitable for secondary transmission. By analyzing the correlation between potential secondary signals and existing primary signals, the system can identify opportunities for spectrum sharing that DAA alone would miss, while still preventing interference.
2Productivity
If new signals are transmitted in the same channel as existing signals, then spectrum efficiency is improved, but interference and signal corruption occur
Solution Approach 1:
The patent applies parameter changes by selecting specific modulation schemes, code sequences, and symbol rates for secondary signals that minimize correlation with primary signals. This allows both signals to occupy the same frequency channel simultaneously without causing harmful interference, thus improving spectrum efficiency while preventing signal corruption.
Solution Approach 2:
The patent employs dynamic signal parameter selection where secondary users adjust their transmission parameters based on the detected characteristics of primary user signals. This dynamic adaptation enables efficient spectrum sharing by continuously optimizing the correlation properties of secondary signals relative to primary signals in real-time.
3Reliability
If channel monitoring is performed to detect existing signals, then transmission interference is avoided, but spectrum utilization is reduced due to conservative channel avoidance
Solution Approach 1:
The patent introduces signal correlation as an intermediary criterion for channel selection. Instead of simply avoiding channels with detected primary signals (DAA approach), the system evaluates the correlation between potential secondary signals and primary signals. This intermediary mechanism enables secondary users to access channels that DAA would reject, increasing available spectrum while maintaining transmission reliability through low-correlation signal design.
Solution Approach 2:
The patent changes the decision-making parameters for channel selection from binary presence/absence detection (DAA) to continuous correlation analysis. By measuring the correlation coefficient between secondary and primary signals, the system can make more nuanced decisions about channel suitability, thereby increasing spectrum utilization while preserving transmission reliability.
Data Source
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AI summary
A computing system in which devices communicate wirelessly as secondary users in a band assigned to primary users. The computers communicate using new signals developed to reduce disruption to primary users of the band. The new signals may be produced by sensing, or otherwise determining, signals used by primary users and developing signals using a modulation scheme or other signal parameters that provides little disruption to primary users. These techniques make available to users unused and/or underused portions of the radio spectrum, such as whitespaces between television channels. The new signals may be generated by software defined radios within the computing devices or by switching between modulation schemes supported by conventional wireless network interface card.