Feedforward Receiver Reducing ISI via Joint Soft Values
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Solution Overview
Problem
Traditional wireless communication systems face challenges with high complexity and processing delays due to the separation of demodulation and decoding processes, particularly in handling inter-symbol interference (ISI), which leads to inefficient reuse of the demodulator and increased complexity in receivers like the turbo receiver.
Innovation Solution
A feedforward receiver is introduced, featuring an enhanced equalizer that generates joint soft values for modem bits and their previous bits, along with a decoder that uses side information to produce improved soft values, avoiding the reuse of the equalizer and simplifying the processing structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional separate demodulation and decoding processes are used, then device complexity is reduced, but processing delay increases and ISI handling efficiency deteriorates
Solution Approach 1:
The patent merges the demodulator and decoder into a unified structure where the demodulator generates joint soft values that inherently incorporate decoding information. The demodulator uses a trellis that combines channel decoding constraints with modulation detection, eliminating the need for separate iterative processing between demodulator and decoder, thus reducing processing delay while maintaining manageable complexity.
Solution Approach 2:
The demodulator performs preliminary decoding operations by incorporating code constraints directly into the soft value generation process. By pre-integrating the decoding logic into the demodulation stage through joint soft value computation, the system avoids subsequent iterative feedback loops, thereby reducing processing delay without significantly increasing complexity.
2Reliability
If iterative feedback processes are used, then ISI handling performance is improved, but device complexity and processing delay increase
Solution Approach 1:
The patent combines the demodulator and decoder functions into a single integrated demodulator that generates joint soft values. This merging eliminates the iterative feedback structure between separate demodulator and decoder, reducing device complexity while maintaining effective ISI handling through the unified trellis-based detection that incorporates both channel and modulation constraints.
3Productivity
If separate demodulator and decoder are used, then ease of manufacture is improved, but processing efficiency deteriorates due to equalizer reuse
Solution Approach 1:
The patent merges demodulation and decoding into a single demodulator unit that processes signals in one pass without requiring iterative equalizer reuse. This integration improves processing efficiency by eliminating redundant operations while maintaining implementation feasibility through a unified algorithmic approach that can be implemented in standard wireless receivers.
Data Source
AI summary
A feedforward receiver and method are described herein that address inter-symbol interference in received symbols by using an enhanced equalizer to generate joint soft values (joint information of a previous modem bit x′ and a modem bit x) and an enhanced decoder which uses the joint soft values and side information (bias about the previous modem bit x′) to output a more reliable information bit x.