Hierarchical Probabilistic Shaping Circuit for Smaller LUT Encoding
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Solution Overview
Problem
Conventional probabilistic shaping encoding circuits face performance degradation and increased circuit scale when the number of input/output bits of each lookup table (LUT) is small, deviating from the Shannon limit or requiring higher SNR for a given transmission capacity.
Innovation Solution
A probabilistic shaping encoding circuit with a hierarchical lookup table structure, incorporating distribution and address replacing circuits between LUTs, reduces circuit scale while maintaining performance by optimizing bit string conversions and signal point arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of input/output bits of each LUT is increased to prevent performance degradation, then the probabilistic distribution shaping performance is improved, but the circuit scale increases
Solution Approach 1:
The patent divides a large LUT into multiple smaller LUTs arranged in a hierarchical structure. Instead of using one large LUT with many input/output bits, the system segments it into multiple smaller LUTs, each handling a portion of the addressing space. This segmentation maintains the required probabilistic distribution shaping performance while reducing the circuit scale of individual LUTs and allowing parallel or cascaded operation.
2Device complexity
If the number of input/output bits of each LUT is decreased to reduce circuit scale, then the circuit complexity is reduced, but performance degradation occurs and deviation from Shannon limit increases
Solution Approach 1:
The patent implements a nested hierarchical structure where smaller LUTs are organized within a larger hierarchical framework. Multiple levels of LUTs are nested, with each level managing a specific portion of the address space and probability distribution. This nesting allows the system to achieve high-performance probabilistic shaping through coordinated operation of smaller units, avoiding the need for a single large LUT while maintaining Shannon limit performance.
3Reliability
If the number of input/output bits of each LUT is increased to maintain performance, then the transmission capacity vs SNR relationship approaches Shannon limit, but the circuit scale and resource requirements increase
Solution Approach 1:
The patent segments the probability distribution shaping function across multiple smaller LUTs, each with fewer input/output bits. By dividing the overall addressing space and probability distribution management across multiple units, the system achieves the required performance (approaching Shannon limit) without concentrating all resources in a single large LUT, thus reducing peak circuit resource requirements.
Solution Approach 2:
The patent combines multiple smaller LUTs to collectively perform the function of a single large LUT. Through hierarchical organization and coordinated operation of multiple LUTs, the system merges their individual capabilities to achieve the overall probabilistic distribution shaping performance required for near-Shannon-limit transmission capacity, while distributing the circuit resources across multiple units.
Data Source
AI summary
Each of the lookup tables is hierarchized in a tree shape, each of the transmission source address bit strings obtained by the m-th distribution circuit of the layer x corresponds to designation information designating a combination of signal point groups in a signal space managed by each of a plurality of lookup tables of the layer x, each of the transmission shaping bit strings generated by the (2m−1)-th lookup table of the layer x and the 2m-th lookup table of the layer x corresponds to designation information designating a combination of signal point groups in a signal space managed by each of a plurality of lookup tables of a layer immediately below or signal point information indicating a signal point arrangement of the signal space.