Single-Carrier Receiver Demodulation for Doubly Selective Channels
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Solution Overview
Problem
Conventional single-carrier modulation systems face challenges in deep fading scenarios due to imperfect recovery, inter-carrier interference (ICI), and high complexity, particularly in doubly selective channels, which affect performance and orthogonality between subcarriers.
Innovation Solution
A receiver device employing a single-carrier Lagrange-Vandermonde Division Multiplexing (LVDM) scheme with a one-tap equalization process, utilizing a Vandermonde matrix for demodulation and iterative procedures to handle doubly selective channels, including channel state information and iterative cancellation techniques, and a method for solving the technical problem.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SC-FDE is used in frequency-selective channels, then equalization can be performed, but perfect recovery cannot be achieved in deep fading scenarios
Solution Approach 1:
The patent changes the mathematical parameters of the equalization process by using Lagrange-Vandermonde decomposition to transform the channel matrix into a product of simpler matrices. This allows the system to achieve perfect recovery in deep fading scenarios by fundamentally changing how the equalization parameters are calculated and applied, rather than just adjusting existing SC-FDE parameters.
Solution Approach 2:
The patent introduces an intermediary mathematical structure (the Lagrange-Vandermonde decomposed matrix) that mediates between the received signal and the original transmitted signal. This intermediary decomposition enables the system to handle deep fading conditions that conventional direct equalization methods cannot resolve.
2Adaptability or versatility
If time-domain channel estimation and detection methods are used in fast fading channels, then channel variations can be tracked, but orthogonality between subcarriers is destroyed resulting in inter-carrier interference
Solution Approach 1:
The patent segments the channel estimation and detection process into distinct stages using the Lagrange-Vandermonde decomposition. By dividing the channel matrix into specific structural components, the system can track time variations while maintaining the mathematical properties needed to preserve subcarrier orthogonality, thus avoiding inter-carrier interference.
Solution Approach 2:
The patent transitions from conventional time-domain only processing to a time-frequency domain approach by using the Vandermonde structure. This dimensional change allows the system to simultaneously handle time variations and maintain frequency domain orthogonality, resolving the conflict between adaptability and interference prevention.
3Reliability
If conventional ISI cancellation methods are used to remove inter-symbol interference, then isolation of desired data symbol can be attempted, but substantial performance error occurs
Solution Approach 1:
The patent performs preliminary action by pre-decomposing the channel into its Lagrange-Vandermonde structure before the actual detection process. This preliminary mathematical preparation enables accurate symbol isolation without requiring complex iterative cancellation methods during reception, as the structure itself facilitates interference separation.
4Measurement precision
If iterative procedures with PIC iterations are used for demodulation, then perfect recovery can be achieved, but computational complexity increases
Solution Approach 1:
The patent changes the computational parameters by using the structured Lagrange-Vandermonde decomposition, which transforms the complex iterative demodulation problem into a series of simpler matrix operations. This parameter transformation maintains recovery precision while reducing the overall computational burden compared to conventional iterative methods.
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AI summary
Receiver devices for single-carrier modulation are disclosed. In particular, the receiver devices of the present disclosure are able to deal with doubly selective channels (i.e., channels varying in time and frequency). The receiver devices are configured to determine channel state information (CSI) of a communication channel and a plurality of signature roots based on the CSI. Each signature root of the plurality of signature roots is a nonzero complex point, wherein the plurality of signature roots are uniformly distributed on a circumference of a circle in a complex plane. The receiver devices are further configured to construct a first Vandermonde matrix based on the plurality of signature roots, perform a demodulation of a single-carrier modulated signal, based on the first Vandermonde matrix, to obtain a demodulated signal, and obtain symbols based on performing an iterative procedure on the demodulated signal.