Multiple Layer Overlay Modulation for Spectral Efficiency
Solution Overview
Problem
Current communication systems face limitations in bandwidth utilization efficiency, particularly due to the fixed time or frequency modeling of signals, which restricts the capacity and spectral efficiency of communication links.
Innovation Solution
The Multiple Level Overlay (MLO) modulation technique extends the in-phase and quadrature phase dimensions of the signal space by using orthogonal signals with minimal time-bandwidth products, allowing for denser packing and increased information-carrying capacity within allocated channels, enabling the overlay of signals in both time and frequency domains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional QAM modulation is used with fixed time or frequency modeling, then the system is simple to implement, but bandwidth utilization efficiency is limited
Solution Approach 1:
The patent transitions from traditional one-dimensional time or frequency signal modeling to two-dimensional time-frequency plane modeling. By treating the time-frequency plane as a notional two-dimensional space and using wavelet transforms, the system can overlay multiple orthogonal signals in both time and frequency domains simultaneously, dramatically increasing bandwidth utilization efficiency beyond conventional QAM limits
Solution Approach 2:
The patent segments the signal representation into multiple orthogonal wavelet basis functions that operate in the time-frequency plane. Each wavelet component carries independent information, allowing parallel transmission of multiple data streams through orthogonal signaling, thereby improving spectral efficiency without requiring additional bandwidth
2Productivity
If more orthogonal signals are overlaid to increase spectral efficiency, then bandwidth utilization improves, but signal interference and detection difficulty increase
Solution Approach 1:
The patent introduces wavelet transforms as an intermediary tool that enables orthogonal signal separation in the time-frequency domain. The wavelet basis functions act as mediators that allow multiple signals to be overlaid orthogonally while providing a mathematical framework for clean separation and detection at the receiver, preventing interference despite high signal density
Solution Approach 2:
The patent changes the fundamental parameters of signal representation by using wavelet transforms that provide time-frequency localization. This transforms the detection problem from separating signals in pure time or pure frequency domains to separating signals in a joint time-frequency space, where orthogonal wavelet basis functions enable clear distinction between overlaid signals even at high densities
Data Source
AI summary
The present invention provides for a communication system and method that overlays signals which are simultaneously mutually orthogonal in both the time and frequency domains, thereby enhancing spectral efficiency. Whereas commonly used sinusoids provide only two mutually orthogonal functions (sine and cosine), certain polynomials provide multiple orthogonal functions, which are also finite in both time and frequency. Using multiple orders of the orthogonal functions allows overlaying signals within a symbol to generate a modulated signal carrying more information than with traditional QAM. Correlating a received signal with locally generated replicas of the orthogonal functions allows demodulation of the signal. This modulation is applicable to twisted pair, cable, fiber, satellite, broadcast and all types of wireless access. The method and system are compatible with many current and future multiple access systems, including EV-DO, UMB, WiMax, WCDMA (with or without MBMS/MIMO), HSPA Evolution, and LTE.