Chirp Spread Spectrum Preamble with Narrow-Band Data Body
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Solution Overview
Problem
Chirp Spread Spectrum (CSS) networks face limitations in spectral efficiency and capacity as the number of nodes increases, with existing modulation techniques either consuming high power, requiring complex processing, or suffering from increased collision probabilities due to frequency drift in local oscillators.
Innovation Solution
A wireless communication method that combines a chirp spread spectrum preamble with a narrow-band data body, allowing for increased spectral efficiency by reducing bandwidth and spreading factor, while maintaining compatibility with legacy equipment and reducing collision probabilities through orthogonal signal handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If CSS modulation is used for long-range communication, then transmission range is improved, but spectral efficiency deteriorates
Solution Approach 1:
The transmission signal is segmented into two distinct parts: a CSS preamble for synchronization and a narrow-band body for data transmission. The preamble uses wide bandwidth CSS modulation for robust synchronization over long ranges, while the body uses narrow-band modulation for efficient spectral utilization, thus resolving the contradiction between range and spectral efficiency
Solution Approach 2:
Different modulation qualities are applied to different parts of the transmission: the preamble portion uses high-bandwidth CSS for optimal synchronization performance, while the data body uses narrow-band modulation for optimal spectral efficiency. Each part is optimized for its specific function, achieving both long range and high spectral efficiency
2Reliability
If carrier sense protocols are implemented to avoid collisions, then collision probability is reduced, but power consumption increases
Solution Approach 1:
The CSS preamble acts as an intermediary signal that enables direct detection and synchronization without requiring complex carrier sense protocols. The distinctive chirp characteristics of the preamble allow receivers to detect and synchronize to transmissions directly, avoiding the need for additional carrier sense listening periods and reducing power consumption while maintaining collision avoidance
3Productivity
If narrow-band modulation is used for spectral efficiency, then bandwidth usage is improved, but collision probability increases due to frequency drift
Solution Approach 1:
Time synchronization is performed preliminarily using the CSS preamble before the narrow-band data transmission begins. The preamble establishes accurate time and frequency reference, compensating for oscillator drift before the narrow-band body transmission, thus preventing collisions while maintaining spectral efficiency
Data Source
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AI summary
A wireless communication method between a plurality of end-points by a plurality of base stations, based on frames that have a chirp spread spectrum,CSS,-modulated preamble followed by a data body modulated at a narrower bandwidth, either by CSS or by an ultra-narrowband, UNB modulation. The system facilitates avoidance or mitigation of collision between packets and allows increase in network capacity, while maintaining the simplicity of detection inherent to CSS modulation.