Multi-Carrier Waveform Modulation for High Spectral Efficiency
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Solution Overview
Problem
Current data communication systems face challenges in increasing data throughput and addressing signal degradation, particularly due to transmission path delay, interference, and non-linearity, with existing modulation techniques like Amplitude Modulation, Frequency Modulation, QAM, QPSK, PSK, and APSK having inefficiencies in power usage, bandwidth, and error rates.
Innovation Solution
The method involves periodic waveform modulation by encoding input digital data at selected phase angles of a sinusoidal waveform to create a modulated sinusoidal waveform with data notches, using a digital-to-analog converter to generate an encoded analog waveform, and employing carrier stacking to achieve high spectral efficiency, where adjacent modulated sinusoidal waveforms are separated by less than 15 Hz with sidebands at least 50 dB below the main signal power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional modulation techniques (AM, FM, QAM, QPSK, PSK, APSK) are used to increase data throughput, then data transmission capacity is improved, but spectral efficiency and power usage efficiency deteriorate
Solution Approach 1:
The patent changes the fundamental parameter of waveform modulation from conventional AM/FM/QAM/PSK to sine wave modulation with data notches. By encoding data as notches (zero-crossings) in the sine wave at specific phase angles, the system achieves higher spectral efficiency while maintaining data throughput. The modulation scheme uses phase angle and notch depth variations to encode multiple bits per symbol, improving spectral efficiency compared to conventional techniques.
Solution Approach 2:
The patent employs periodic sine wave modulation where data is encoded as periodic notches in the waveform. Each symbol period contains a complete sine wave cycle with notches positioned at specific phase angles. This periodic structure enables efficient spectral utilization while maintaining constant envelope properties, resolving the contradiction between data throughput and spectral efficiency.
2Productivity
If higher order QAM modulation is used to increase data rates, then data throughput is improved, but peak to average power ratio increases causing non-linearity issues
Solution Approach 1:
The patent changes the modulation approach from variable amplitude QAM to constant envelope sine wave modulation with notches. By encoding data in the presence/absence of notches at specific phase angles rather than varying amplitude levels, the system maintains constant peak power while achieving high data rates through phase and notch pattern encoding, thus eliminating the high PAPR problem of conventional QAM.
3Productivity
If QPSK modulation is used for data transmission, then data throughput is improved, but signal envelope fluctuation occurs causing synchronization complications and non-linearity
Solution Approach 1:
The patent changes from QPSK's variable envelope to constant envelope sine wave modulation. By using notches in the sine wave at specific phase angles to encode data instead of QPSK's phase transitions that cause envelope fluctuations, the system maintains stable signal envelope while achieving comparable or superior data throughput through multi-bit per symbol encoding.
Data Source
AI summary
A multi-carrier data communications system and method having high spectral efficiency. The method includes encoding input digital data at selected phase angles of a plurality of sinusoidal waveforms to create a plurality of modulated sinusoidal waveforms. An output analog waveform is generated where the output analog waveform includes a plurality of encoded analog communication signals corresponding to a plurality of digital representations of the plurality of modulated sinusoidal waveforms. The encoding is performed so that adjacent ones of the plurality of modulated sinusoidal waveforms are separated in frequency by less than 15 Hz and any sideband included within the output analog waveform is of a power at least 50 dB below a power of the encoded analog communication signal associated with the sideband.