FSK Signal Generation in OFDM Sub-Carriers
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Solution Overview
Problem
Current wireless communication technologies face challenges in efficiently generating frequency shift keying (FSK) signals within orthogonal frequency division multiplexing (OFDM) signals, leading to distortion and interference, particularly when transmitting to devices like IoT sensors that require low data rates and operate in unlicensed bands like the 2.4 GHz ISM band.
Innovation Solution
A method is introduced to generate FSK signals by assigning a set of adjacent sub-carriers and selecting a phase for each FSK symbol such that the phase difference between consecutive symbols meets a criterion, minimizing distortion and discontinuities, thereby reducing out-of-band emissions and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If FSK signals are generated within OFDM signals using conventional methods, then transmission to IoT devices is enabled, but distortion and discontinuities occur in the FSK signal
Solution Approach 1:
The patent applies local quality by treating FSK sub-carriers differently from regular OFDM sub-carriers. Specifically, the FSK signal generation uses a dedicated process where only certain sub-carriers are activated to carry FSK modulation, while maintaining the OFDM structure. This localized approach ensures that FSK signal quality is optimized independently within the broader OFDM framework, preventing distortion and discontinuities that would affect the entire signal.
Solution Approach 2:
The patent segments the OFDM signal into distinct components: FSK-modulated sub-carriers and regular OFDM sub-carriers. By dividing the frequency spectrum into specific sub-carrier assignments for FSK, the system can generate FSK signals with proper phase continuity and frequency hopping without interfering with the overall OFDM signal structure, thereby eliminating distortion and discontinuities.
2Productivity
If FSK signals are generated within OFDM signals, then spectrum efficiency is improved, but out-of-band emissions and interference with adjacent channels increase
Solution Approach 1:
The patent converts the potential harm of out-of-band emissions into a benefit by carefully controlling the spectral characteristics of FSK sub-carriers. Through proper windowing and pulse shaping techniques applied to the FSK modulation process, the method ensures that energy is concentrated within the allocated bandwidth while suppressing out-of-band emissions. This transforms what could be harmful interference into an efficient spectrum utilization approach.
3Ease of manufacture
If phase selection is not optimized for FSK symbols, then signal generation is simplified, but discontinuities and distortion increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal phase values for FSK symbols in lookup tables before transmission. The phase selection process uses these pre-computed values to ensure continuous phase transitions between symbols, avoiding discontinuities and distortion. This preliminary preparation maintains signal quality without adding real-time computational complexity during actual signal generation.
Data Source
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AI summary
A method is disclosed of generating a frequency shift keying (FSK) signal comprised in an orthogonal frequency division multiplexing (OFDM) signal comprising a plurality of sub-carriers. The FSK signal comprises FSK symbols wherein each FSK symbol has a corresponding FSK symbol frequency. The method comprises assigning (310) a set of adjacent sub-carriers to transmission of the FSK signal (wherein the set is a sub-set of the plurality of sub-carriers), and associating each FSK symbol frequency with a corresponding sub-carrier in the set of adjacent sub-carriers. The method also comprises selecting (330), for each FSK symbol (201, 202, 203) to be transmitted, an FSK symbol phase such that an FSK signal phase at a start (252) of the FSK symbol (202) to be transmitted meets a phase difference criterion in relation to the FSK signal phase at an end (251) of an immediately previous FSK symbol (201). The method further comprises generating (340) the FSK signal comprising the FSK symbol to be transmitted by modulating the sub-carrier corresponding to the FSK symbol frequency based on the selected FSK symbol phase and muting the remaining sub-carriers of the set. Corresponding arrangement, access point and computer program product are also disclosed.