Demodulation Method for Relay Communication Systems
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Solution Overview
Problem
The relay cooperative communication system using Complex Field Network Coding (CFNC) faces difficulties in actual implementation due to a sharp increase in computational load when high-order modulation methods are used, as the Maximum Likelihood Decision (MLD) method requires processing a large number of signal combinations, making real-time processing challenging.
Innovation Solution
A demodulation method that reduces computational complexity by comparing Channel Frequency Response (CFR) powers to select M reference signals and corresponding signals, estimating transmission signals using reduced pairs, thereby reducing the number of signal pairs to be considered from M2 to M, and implementing this in a reception apparatus with an FFT unit and MLD unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Maximum Likelihood Decision (MLD) method is used to demodulate signals in relay cooperative communication system using CFNC, then signal demodulation performance is improved, but computational load increases sharply when high-order modulation methods are used
Solution Approach 1:
The patent segments the signal processing task by separating the demodulation process into two stages: first performing FFT to convert time-domain signals to frequency-domain, then applying MLD only to the frequency-domain signals. This segmentation allows the system to handle high-order modulation by processing signals in the frequency domain where the computational complexity of MLD is reduced from O(M²) to O(M), thus maintaining signal demodulation performance while reducing computational load.
2Productivity
If high-order modulation methods are used to increase data transmission rate, then productivity is improved, but computational complexity increases by geometrical progression making real-time processing difficult
Solution Approach 1:
The patent replaces the conventional time-domain MLD approach with a frequency-domain processing approach using FFT. This substitution transforms the mechanical signal processing operation from time-domain to frequency-domain, where the computational complexity of MLD is reduced. The FFT-based approach allows high-order modulation to be processed with O(M) complexity instead of O(M²), enabling real-time processing of high-data-rate transmissions.
3Measurement precision
If MLD method processes all M×M signal combinations to achieve best demodulation performance, then measurement precision is improved, but loss of time increases due to inability to review all combinations in real time
Solution Approach 1:
The patent applies preliminary action by performing FFT transformation on the received signals before applying MLD. This preliminary frequency-domain transformation prepares the signals in a form that reduces the computational complexity of subsequent MLD processing. By pre-processing signals in the frequency domain, the system can estimate transmitted signals with O(M) complexity instead of O(M²), achieving accurate signal estimation within real-time constraints.
Data Source
AI summary
Disclosed are a method for demodulating received signals and an apparatus therefore which can maintain quality of signals and can reduce computational complexity. A demodulation method of a receiving device for receiving a plurality of signals modulated through a M-ary (M is a natural number of 1 or more) modulation method includes: comparing channel frequency response power of a first channel with channel frequency response power of a second channel, selecting M reference signals on the basis of the compared result, selecting corresponding signals paired with respective selected M reference signals, and estimating transmitting signals from the M signal pairs including pairs of the reference signal and the corresponding signal. Accordingly, the computational complexity is reduced from O (M2) to O (M).