Quaternion Amplitude Modulation for Fading Channel Robustness
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Solution Overview
Problem
Quadrature Amplitude Modulation (QAM) is limited to transmitting only two signal components, which restricts its ability to fully utilize spectral efficiency and robustness in communication systems, particularly in frequency-selective fading channels.
Innovation Solution
The proposed Quaternion Amplitude Modulation (Quat-AM) scheme processes and transmits four-dimensional signals using quaternions, combining four real-valued components and employing two different carrier frequencies to achieve frequency diversity and spectral shaping, allowing for robust signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If QAM transmits only two signal components over the same carrier frequency, then the modulation scheme remains simple and implementable, but spectral efficiency and robustness in frequency-selective fading channels are limited
Solution Approach 1:
The patent extends QAM from two-dimensional (I and Q components) to four-dimensional signaling by introducing two additional signal components. This is achieved by using quaternion mathematics where a complex signal z(t) is multiplied by another complex signal w(t), creating a four-dimensional output that spreads information across multiple dimensions and frequency components, thereby improving robustness against frequency-selective fading
Solution Approach 2:
The patent segments the four-dimensional signal into multiple components that are transmitted over different frequency bands. By separating the signal components and assigning them to different frequency regions, the system achieves frequency diversity, ensuring that if one frequency component is attenuated by fading, other components can still carry the information reliably
2Productivity
If QAM uses a single carrier frequency for transmission, then the implementation is straightforward, but frequency diversity cannot be exploited and spectral efficiency is constrained
Solution Approach 1:
The patent transitions from two-dimensional QAM to four-dimensional signaling by introducing an additional complex multiplication operation. This dimensional expansion allows the system to encode more information per symbol period, effectively doubling the spectral efficiency while maintaining a systematic approach through quaternion algebra
Solution Approach 2:
The patent introduces dynamic frequency allocation where different signal components are modulated onto different carrier frequencies. This dynamic approach allows the system to adapt to channel conditions by exploiting frequency diversity, selecting frequency bands that experience less fading, thereby improving overall spectral efficiency
Data Source
AI summary
According to an aspect of the present disclosure there is provided a communication device comprising circuitry configured to modulate a four-dimensional input signal by combining the four real-valued signal components of the input signal into a transformed signal and multiplying the transformed signal by carrier signals using two different carrier frequencies to obtain a transmit signal, and transmit the transmit signal.