Partial Probabilistic Signal Shaping for Flexible FEC
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Solution Overview
Problem
Conventional probabilistic signal-shaping schemes limit the use of forward error correction (FEC) by being compatible only with systematic FEC codes and constrain the rate of the FEC code, restricting the flexibility and efficiency of error correction in communication systems.
Innovation Solution
A partial amplitude-shaping scheme is employed, where bit-words representing binary labels of transmitted amplitudes have a fixed number of most-significant bits (MSBs) generated using a shaping code and a fixed number of least-significant bits (LSBs) generated using an FEC code, allowing for increased flexibility in FEC code rates and compatibility with convolutional FEC codes like trellis-coded modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional probabilistic signal-shaping schemes are used, then energy savings through shaping gain are achieved, but the flexibility and efficiency of error correction are worsened due to limitations on FEC code rates and compatibility restrictions
Solution Approach 1:
The binary label of each transmitted amplitude is segmented into two distinct parts: MSBs (most significant bits) that are generated using a shaping code to provide energy savings, and LSBs (least significant bits) that are generated using an FEC code to provide error correction flexibility. This segmentation allows each part to be optimized independently, resolving the contradiction between energy efficiency and adaptability.
2Use of energy by moving object
If conventional probabilistic signal-shaping schemes are used, then shaping gain is achieved, but device complexity increases due to restrictions on FEC code selection and rates
Solution Approach 1:
By dividing the amplitude labeling into MSBs and LSBs with different encoding schemes, the patent simplifies the overall system design. The shaping encoder only needs to handle MSBs while the FEC encoder handles LSBs, distributing the complexity across two simpler, specialized components rather than one complex unified encoder.
Solution Approach 2:
The patent changes the parameter structure by separating the binary label into MSBs and LSBs with different generation methods. This parameter change allows the system to achieve shaping gain while simultaneously reducing complexity by enabling the use of simpler FEC codes with flexible rates that would not be available in conventional unified schemes.
3Use of energy by moving object
If conventional probabilistic signal-shaping schemes are used, then energy efficiency is improved, but the rate of FEC code is constrained, limiting error correction efficiency
Solution Approach 1:
The patent segments the error correction function from the energy optimization function by assigning MSBs to shaping code generation and LSBs to FEC code generation. This allows the FEC code to operate at optimal rates for error correction efficiency without being constrained by the energy efficiency requirements of the shaping scheme.
Solution Approach 2:
The patent applies partial shaping by only shaping the MSBs while leaving LSBs to be handled by flexible-rate FEC codes. This partial application of shaping allows the system to achieve sufficient energy efficiency while maintaining high error correction efficiency through the use of FEC codes operating at their optimal rates.
Data Source
AI summary
A communication system in which probabilistic signal shaping and FEC coding are jointly applied using a partial amplitude-shaping scheme, under which bit-words representing binary labels of the transmitted amplitudes may have (i) a fixed number of amplitude most-significant bits (MSBs) generated using a shaping code and (ii) a fixed number of amplitude least-significant bits (LSBs) generated using an FEC code, e.g., without the shaping code being applied thereto. In various embodiments, the transmitted constellation symbols can carry, as sign bits, some original information bits and/or the parity bits generated by FEC-encoding some combination of the MSBs, the LSBs, and said some original information bits. Some embodiments are compatible with convolutional FEC codes, such as the trellis-coded modulation. Some embodiments can be used in communication systems relying on discrete multi-tone modulation, such as the systems providing DSL access over subscriber lines.