Short-Message Communication With PAS and Trellis Coding
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Solution Overview
Problem
Existing digital communication systems struggle to efficiently transmit short block-length messages, as capacity-approaching codes like LDPC and Polar codes perform poorly at short block-lengths, failing to exceed Polyanskiy's Random Coding Union (RCU) bound.
Innovation Solution
A communication system utilizing a trellis-coded-modulation (TCM) encoder with a distribution matcher, error detection encoder, and convolutional encoder to process short messages, optimizing performance metrics such as frame error rate, combined with probabilistic amplitude shaping (PAS) to achieve transmission rates beyond the RCU bound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If capacity-approaching codes like LDPC and Polar codes are used, then transmission rate approaches Shannon limit, but performance deteriorates at short block-lengths
Solution Approach 1:
The patent changes the code parameters by using convolutional codes with specific constraint lengths (K=3, K=7, K=15) and rates (2/3, 3/4) optimized for short block-length performance, rather than using fixed parameters of LDPC or Polar codes. This parameter adaptation allows the system to achieve reliable performance at short block-lengths while maintaining high transmission rates through probabilistic amplitude shaping.
Solution Approach 2:
The patent implements dynamic adaptation by selecting different convolutional code rates and constraint lengths based on the message length and channel conditions. The system dynamically adjusts coding parameters and uses probabilistic amplitude shaping to optimize performance for each specific transmission scenario, rather than relying on a fixed code structure.
2Productivity
If Trellis Coded Modulation is used, then short message transmission is enabled, but decoding complexity increases
Solution Approach 1:
The patent replaces complex mechanical decoding operations with probabilistic amplitude shaping and simplified convolutional code decoding. Instead of using complex Trellis Coded Modulation decoding, the system uses probability distribution matching and amplitude shaping to achieve efficient short message transmission with lower decoding complexity.
Solution Approach 2:
The patent segments the transmission process into distinct stages: probabilistic amplitude shaping, convolutional code encoding, and simplified decoding. This segmentation allows each stage to be optimized independently, reducing overall system complexity while maintaining high transmission efficiency for short messages.
3Reliability
If error detection code is added, then reliability is improved, but message length increases
Solution Approach 1:
The patent applies partial error detection using convolutional codes with specific rates (2/3, 3/4) that provide sufficient error detection capability for short messages without requiring excessive overhead. The probabilistic amplitude shaping provides additional error detection functionality with minimal additional bits, achieving reliable transmission with minimal impact on message length.
Data Source
AI summary
Communication systems and methods are disclosed that utilize Probability Amplitude Shaping (PAS) and Trellis Coded Modulation (TCM) to transmit short block-length messages. While capacity-approaching codes, such as Low Density Parity Check (LDPC) codes, Turbo codes, and Polar codes, can achieve data rates approaching the Shannon limit at large block-lengths, the performance of these codes can deteriorate dramatically at short block-lengths. Communication systems configured in accordance with various embodiments of the invention can utilize classical codes to encode short block-length messages to achieve communication rates exceeding Polyanskiy's Random Coding Union bound. In several embodiments, message bits are transmitted using a TCM system in which message bits that have been previously encoded by an error detection code are encoded using a convolutional code (CC). In a number of embodiments, the error detection code and the CC are obtained via a joint optimization with respect to a Frame Error Rate bound.