QAM Symbol Shaping for Finer Data Rate Control
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Solution Overview
Problem
Current data transmission using quadrature amplitude modulation (QAM) is limited by the number of constellation points, which can lead to difficulties in distinguishing symbols due to noise and channel impairments, and requires costly equipment for increased data rates, with limited granularity in transmission rate adjustments.
Innovation Solution
Implementing probabilistic constellation shaping in QAM schemes, allowing for the selection of symbols based on energy levels and their relationships to achieve higher granularity in data transmission rates, reducing costs by favoring lower power symbols and adjusting symbol probabilities to improve signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of constellation points in QAM is increased to achieve higher data rates, then data transmission capacity is improved, but the difficulty in distinguishing symbols due to noise and channel impairments increases
Solution Approach 1:
The patent changes the energy distribution parameter among constellation points by introducing probabilistic constellation shaping. Instead of uniform energy distribution, the system assigns different probabilities to different constellation points based on their energy levels, allowing optimization of the trade-off between data rate and symbol distinguishability.
Solution Approach 2:
The patent applies local quality by treating different constellation points differently based on their energy levels. Low-energy constellation points are assigned higher probabilities while high-energy points are assigned lower probabilities, creating non-uniform local characteristics across the constellation that improve overall system performance.
2Device complexity
If conventional QAM schemes are used with fixed constellation points, then system complexity is kept simple, but the granularity in transmission rate adjustments is limited
Solution Approach 1:
The patent introduces dynamics by making the constellation point selection probabilistic rather than fixed. The system can dynamically adjust the probability distribution across constellation points based on channel conditions and desired data rates, enabling fine-grained transmission rate adjustments without changing the overall constellation structure.
3Reliability
If higher power symbols are used to improve signal strength, then signal-to-noise ratio is improved, but transmission costs increase
Solution Approach 1:
The patent changes the energy distribution parameter by assigning different probabilities to constellation points based on their energy levels. The system optimizes the balance between using higher energy symbols (for better SNR) and lower energy symbols (for reduced cost) by adjusting the probability distribution according to channel conditions and cost constraints.
Data Source
AI summary
An example method may include obtaining multiple symbols each associated with a different state in a quadrature amplitude modulation scheme used for transmission of a data signal. The method may further include determining a sequence of symbols of the multiple symbols for a first portion of the data signal. The determining may include selecting an index value from multiple index values for the first portion of the data signal. The determining may also include obtaining energy states of multiple sequences of the symbols using the energy levels of the symbols. The determining may further include obtaining a relationship between the energy levels of the symbols, the energy states of the multiple sequences of the symbols, and the multiple index values. The determining may further include selecting the sequence of symbols based on the relationship and the index value for the first portion of the data signal.