Adaptive Modulation for Wireless Block Edge Spectral Emissions
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Solution Overview
Problem
Wireless communication systems often experience excess spectral emissions at block edges, leading to interference with other transmissions and non-compliance with regulatory limits, typically addressed by reducing transmission power which results in lower quality and reduced coverage.
Innovation Solution
A wireless communication device equipped with a block edge detector and modulator selector that adjusts modulation using alternative lookup tables to smooth phase trajectory shifts, reducing spurious emissions without lowering transmission power, by switching to a modulation with smaller spectral emissions when approaching a block edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If transmission power is reduced to comply with spectral emission limits at block edges, then regulatory compliance is achieved, but signal quality and coverage are degraded
Solution Approach 1:
The patent changes the modulation parameter (spectral mask characteristics) adaptively based on frequency position. When approaching block edges, the system switches to a modulation scheme with a spectral mask that has lower sidelobes, thereby reducing spectral emissions without reducing transmission power. This resolves the contradiction by modifying the signal's spectral parameters rather than its power level.
Solution Approach 2:
The patent implements dynamic modulation selection based on real-time detection of block edge proximity. The system continuously monitors frequency position and adaptively switches between different modulation schemes (e.g., GMSK with different BT values or different spectral masking filters). This dynamic adaptation allows the system to maintain high signal quality in channel centers while complying with emission limits at block edges.
2Object-generated harmful factors
If transmission power is reduced to minimize interference at block edges, then interference with other transmissions is decreased, but coverage area is reduced
Solution Approach 1:
The patent changes the spectral parameters of the transmitted signal by selecting different modulation schemes with appropriate spectral masks. This allows the system to confine spectral emissions within regulatory limits at block edges while maintaining full transmission power, thereby preserving coverage area without causing excessive interference to adjacent channels.
3Device complexity
If a fixed spectral mask is used for all transmissions, then system simplicity is maintained, but regulatory compliance at block edges cannot be ensured
Solution Approach 1:
The patent implements a dynamic modulation selection mechanism that adapts the spectral mask based on detected block edge proximity. The system includes a block edge detector that monitors frequency position and triggers modulation scheme changes when necessary. This dynamic approach ensures regulatory compliance at block edges while maintaining system simplicity through automated detection and pre-configured modulation alternatives.
Solution Approach 2:
The system performs self-adjustment by automatically detecting block edge conditions and selecting appropriate modulation schemes without external intervention. The block edge detector and modulator selector work autonomously to ensure compliance, eliminating the need for complex external control mechanisms while maintaining spectral emission limits.
Data Source
AI summary
A block edge detector (310) determines (510) whether a wireless communication transmission with a first modulation having excess spectral emissions will be transmitted at a frequency on a block edge (120). In response, a modulator selector (320) changes (530) the wireless communication transmission to a second modulation with lessened spectral emissions. Preferably, the second modulator (340) is operably coupled to an alternative lookup table (360) wherein phase trajectory entries likely to cause excess spectral emissions such as spurious emissions are smoothed. The entries may be smoothed by filtering, non-linear extrapolation, and/or linear extrapolation. Alternatively, the second modulator (340) uses an alternative lookup table (360) that is a GMSK modulator with BT less than 0.3.