QAM Demodulation Using Scrambled Symbol Number Reference Points
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Solution Overview
Problem
Current wireless communication systems face challenges in demodulating QAM signals, particularly in realizing descrambling and calculating soft symbols, due to the complexity of phase and amplitude manipulation, and the need for extensive correspondence tables for all scramble patterns and reference points.
Innovation Solution
A wireless communication system and method that generates reference points using transmission symbol numbers, allowing for simple demodulation and soft symbol calculation for both PSK and QAM by scrambling symbol mapping numbers, performing channel equalization, and using interleaving and deinterleaving to calculate bit likelihood and symbol mapping probabilities, thereby eliminating the need for complex phase rotation and code conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If QAM descrambling is performed by calculating bit likelihood and performing code conversion, then accurate demodulation is achieved, but the device complexity increases due to the need for extensive correspondence tables for all scramble patterns and reference points
Solution Approach 1:
The patent extracts only the necessary correspondence information between reference points and scramble patterns rather than storing all possible combinations. By generating reference points dynamically and storing only essential mapping relationships, the system achieves accurate QAM demodulation while significantly reducing the size of correspondence tables required in the device.
Solution Approach 2:
The patent performs preliminary generation of reference points and pre-calculation of necessary correspondence relationships before actual demodulation. By preparing reference point data in advance and storing only essential mappings, the system reduces real-time computational complexity while maintaining demodulation accuracy.
2Ease of manufacture
If PSK scrambling is performed by phase rotation, then simple implementation is achieved, but QAM scrambling cannot be realized by simply manipulating amplitude and phase
Solution Approach 1:
The patent creates a universal reference point generation mechanism that works for both PSK and QAM modulation schemes. By generating reference points that encode both phase and amplitude information, the system uses a single unified approach rather than separate processing paths, making the implementation simple while maintaining compatibility with multiple modulation types.
Solution Approach 2:
The patent changes the representation parameters from separate phase and amplitude manipulations to a unified reference point framework. By expressing both PSK and QAM scrambling effects through reference point transformations, the system achieves parameter unification that simplifies implementation while maintaining versatility across different modulation schemes.
3Reliability
If all combinations of reference points and scramble patterns are stored in ROM, then complete coverage is achieved, but the loss of substance increases due to large memory requirements
Solution Approach 1:
The patent segments the correspondence information into essential and non-essential parts. Only the critical mapping relationships between reference points and scramble patterns are stored in memory, while redundant or derivable information is generated on-demand. This segmentation maintains complete coverage for accurate demodulation while significantly reducing ROM size.
Solution Approach 2:
Instead of storing all possible correspondence tables, the patent stores compact reference point data that can be copied and transformed to generate the necessary mapping information. By using reference point representations that can be systematically transformed, the system replaces large static tables with smaller dynamic generation mechanisms.
Data Source
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AI summary
The present invention carries out SISO decoding of a reception signal having a scrambled symbol arrangement using a process having reduced complexity. Coordinates are generated for a reference point obtained not through scrambling and mapping of a symbol reference point position but through scrambling and mapping of a symbol number. This reference point simulates transmission-side scrambling and is generated for each symbol number by a first mapping means. Because the binary expression of a corresponding original signal number is retained, a bit likelihood calculation means can easily calculate a bit likelihood based on the distance between the reference point and a reception signal. The calculated bit likelihood is thereafter deinterleaved and subjected to SISO error-correcting decoding. The thus obtained bit likelihood is then reinterleaved and used to calculate a symbol probability. Soft symbols are generated through the multiplication of all the calculated symbol probabilities by corresponding reference points output by a second mapping means similar to the first mapping means.