Multi-Carrier On-Off Keying Signal PSD Flattening
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Solution Overview
Problem
The existing multicarrier On-Off Keying (MC-OOK) signal generation for wake-up packets in wireless communication systems suffers from spectral lines in the Power Spectral Density (PSD), which limits the maximum transmit power due to regulatory constraints, and lacks spectral flatness, resulting in reduced output power.
Innovation Solution
Applying complex conjugation randomly to the basic baseband waveform and using a shift register mechanism to generate binary randomized sequences for phase rotations, which flattens the PSD and eliminates spectral lines, thereby increasing output power while maintaining low implementation complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional MC-OOK signal generation is used, then the implementation complexity is low, but spectral lines appear in the PSD which limits maximum transmit power
Solution Approach 1:
The patent applies dynamic phase rotation to the MC-OOK signal by randomly selecting from multiple phase values (0, π/2, -π/2, π) for each symbol. This dynamic transformation converts the static spectral structure into a moving one, dispersing concentrated spectral lines across a broader frequency range and achieving spectral flatness while maintaining low implementation complexity through simple phase shifters.
Solution Approach 2:
The patent changes the phase parameter of the MC-OOK signal by introducing random phase shifts from the set {0, π/2, -π/2, π}. This parameter transformation modifies the spectral characteristics of the signal, converting sharp spectral lines into a flatter power spectral density distribution, thereby enabling higher transmit power within regulatory limits.
2Reliability
If the same OFDM symbol is used for all data symbols to generate ON part, then coherent reception is enabled and PAPR is reduced, but spectral lines are created in the PSD
Solution Approach 1:
The patent introduces dynamic phase rotation to the repeated OFDM symbols, transforming the static spectral structure into a dynamic one. By randomly selecting phase values for each symbol while maintaining the same underlying OFDM structure, the patent preserves coherent reception capabilities through the consistent symbol format while dispersing spectral lines through the random phase transformations.
Solution Approach 2:
The patent extracts the harmful spectral line component by applying phase rotation that separates the spectral energy from concentrated lines. The phase rotation operation effectively removes the harmful spectral concentration while preserving the useful signal structure, allowing the same OFDM symbol to be reused without creating spectral lines.
3Object-generated harmful factors
If phase randomization is applied to eliminate spectral lines, then PSD flatness is improved, but implementation complexity increases
Solution Approach 1:
The patent implements dynamic phase rotation using a simple random selection mechanism from a predefined phase set {0, π/2, -π/2, π}. This dynamic approach achieves spectral flatness through minimal complexity operations, as it only requires phase shifters and random number generation rather than complex signal processing algorithms.
Solution Approach 2:
The patent changes the phase parameter through random selection from discrete values, which is computationally simple and hardware-efficient. This parameter transformation achieves PSD flatness without requiring complex mathematical operations, maintaining low implementation complexity while effectively eliminating spectral lines.
Data Source
AI summary
A method of transmitting an On-Off Keying, OOK, signal includes an ON waveform and an OFF waveform forming a pattern representing transmitted information. The method includes obtaining a basic baseband waveform; scrambling the basic baseband waveform by applying a first binary randomised sequence where one of the binary values cause transformation to a complex conjugate, modulating the information to be transmitted by applying the scrambled basic baseband waveform for the ON waveform and applying no waveform for the OFF waveform; and transmitting the modulated information.