FTN Demodulation Layering for High-Order Modulation Complexity
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Solution Overview
Problem
Current Faster-than-Nyquist (FTN) demodulation algorithms face complexity issues with high-order modulation modes, making it difficult to achieve high spectrum efficiency, especially when performing demodulation for high-order modulation schemes due to exponential increases in the number of states and branch transfers.
Innovation Solution
The use of a layering technology that implements multi-layer low-order modulation and concurrent transmission, allowing for FTN demodulation with relatively low complexity by generating state transition lattice diagrams and calculating log-likelihood ratios for each layer, effectively reducing interference and noise impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-order modulation mode is used to improve spectrum efficiency, then spectrum efficiency is improved, but demodulation complexity increases exponentially due to exponential increase in quantity of states and branch transfers
Solution Approach 1:
The patent segments the high-order modulation demodulation problem into multiple low-order modulation layers. Each layer is demodulated separately using simplified FTN demodulation algorithms, avoiding the exponential complexity of direct high-order modulation demodulation while maintaining equivalent spectrum efficiency through multi-layer concurrent transmission
Solution Approach 2:
The patent transforms the single high-order modulation dimension into multiple low-order modulation layers, adding a layer dimension to the system. This dimensional transformation allows each layer to be processed independently with lower complexity algorithms, effectively resolving the complexity-spectrum efficiency trade-off
2Measurement precision
If BCJR algorithm is applied to high-order modulation mode, then demodulation accuracy is improved, but quantity of states and branch transfers increases exponentially making it inapplicable
Solution Approach 1:
The patent divides the high-order modulation signal into multiple low-order modulation layers, allowing the BCJR algorithm to be applied to each layer separately with manageable state and branch transfer quantities, rather than attempting to apply it directly to the entire high-order modulation signal which would result in exponential complexity
Solution Approach 2:
The patent applies FTN demodulation partially to each low-order modulation layer rather than attempting complete demodulation of the entire high-order signal at once. This partial action approach makes the demodulation process tractable while maintaining overall system performance
Data Source
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Figure 2b
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AI summary
An FTN-based communication method and a related apparatus are disclosed. The method includes: receiving, by a receiving apparatus, a signal concurrently sent by using K layers, and converting the signal into to-be-processed symbols, where K is a positive integer greater than 1, and powers corresponding to a first layer to a Kth layer increase successively; and for an ith layer in the K layers, where i is greater than or equal to 1 and less than or equal to K, performing the following steps: separating, by the receiving apparatus, an ith-layer to-be-processed symbol from the to-be-processed symbols; performing, by the receiving apparatus, FTN demodulation on the ith-layer to-be-processed symbol, to obtain an ith-layer demodulated symbol; and making, by the receiving apparatus, decision based on the ith-layer demodulated symbol, to obtain an ith-layer decision result.