Gray-Mapped Distribution Matching for Spectrally Efficient PAS
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Solution Overview
Problem
Existing wireless communication systems face challenges in improving signal transmission efficiency, reliability, and coverage due to complex and dynamic environments, which can attenuate or block signals, and there is a need for techniques to enhance spectral efficiency and reduce redundant transmissions.
Innovation Solution
The implementation of probabilistic amplitude shaping (PAS) with Gray mapping in the transmitter and receiver architecture, which adjusts the probability of constellation points to mimic a capacity-achieving distribution, allowing for variable-to-fixed distribution matching and reducing signaling overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional modulation techniques are used, then the system is simple to implement, but spectral efficiency is limited due to the shaping gap
Solution Approach 1:
The patent applies probabilistic amplitude shaping by changing the probability distribution parameters of constellation points in the modulation scheme. Instead of uniform distribution, different probabilities are assigned to different amplitude levels, transforming the statistical parameters to achieve capacity-achieving distribution and close the shaping gap, thereby improving spectral efficiency
Solution Approach 2:
The patent introduces variable-to-fixed distribution matching where the input bit rate is variable and the output symbol rate is fixed. The system dynamically adapts the number of information bits to be transmitted based on channel conditions and QoS requirements, allowing flexible rate adaptation while maintaining fixed frame structure for efficient processing
2Productivity
If probabilistic amplitude shaping is implemented, then spectral efficiency increases, but the complexity of encoding and decoding processes increases
Solution Approach 1:
The patent segments the encoding process into distinct functional blocks: arithmetic encoder for distribution matching, separate mapper for constellation assignment, and layered structure for variable-to-fixed rate adaptation. This modular segmentation allows each component to be optimized independently and facilitates implementation using standard coding libraries
Solution Approach 2:
The patent introduces an arithmetic decoder as an intermediary component that bridges the gap between the probabilistic amplitude shaping encoder and the standard demapper. This intermediary performs the reverse transformation, converting received symbols back to the original bit sequence while maintaining compatibility with existing decoding algorithms
3Adaptability or versatility
If variable-to-fixed distribution matching is used, then rate adaptation flexibility improves, but processing complexity increases
Solution Approach 1:
The patent implements variable-to-fixed distribution matching where the input bit block length varies according to channel conditions and QoS requirements, while the output symbol block length remains fixed. This dynamic adaptation at the input stage allows flexible rate control without requiring complex adjustments throughout the entire transmission chain
Solution Approach 2:
The system changes the parameter of information bit length (k) dynamically based on channel quality and service requirements, while keeping the modulation order and symbol block length fixed. This single parameter change at the input stage simplifies the overall system design compared to adapting multiple parameters throughout the transmission chain
4Reliability
If Gray mapping is applied, then error performance improves in variable-to-fixed distribution matching, but implementation complexity increases
Solution Approach 1:
The patent applies Gray mapping which creates an asymmetric relationship between adjacent constellation points and their corresponding bit patterns. Specifically, adjacent constellation points differ by only one bit in their binary representation, creating an asymmetric error protection scheme where single-bit errors are minimized, thereby improving error performance in variable-to-fixed distribution matching
Data Source
AI summary
Certain aspects of the present disclosure provide a method for wireless communications by a transmitter. The method generally includes obtaining a first block of information bits from a buffer, generating a first sequence of probabilistic amplitude shaped (PAS) symbols, from the first block of information bits, using a demapper function and an arithmetic decoder function, transmitting the first sequence of PAS symbols to a receiver, combining a first subset of the first block of information bits, identified by an arithmetic encoder function and a mapper function, with a second block of information bits from the buffer, generating a second sequence of PAS symbols, from the combined first subset of the first block of information bits and second block of information bits, using the demapper function and the arithmetic decoder function, and transmitting the second sequence of PAS symbols to the receiver.