Optical Receiver LLR Mapping for High-Dimensional Soft Decoding
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Solution Overview
Problem
As the number of dimensions in modulated signals increases, it becomes difficult to reduce the processing amount of soft decision, particularly due to the large size of look-up tables required for log-likelihood ratio computations in error correction coding, such as LDPC coding, which leads to increased circuit size and power consumption.
Innovation Solution
An optical reception apparatus that generates and processes optical modulated signals by encoding bit sequences, where the log-likelihood ratio of the second bit sequence is computed using a symbol output unit, and then used to compute the log-likelihood ratio of the first bit sequence, allowing for decoding of the transmission bit sequence with reduced processing through a correspondence relationship between the bit sequences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of dimensions of modulation is increased, then the communication capacity is improved, but the size of the look-up table increases
Solution Approach 1:
The patent segments the bit sequence into multiple groups and processes each group separately through multiple computation units. Instead of computing LLR for all bits simultaneously using a large look-up table, the system divides the computation into smaller independent units, each handling a subset of bits. This segmentation allows the use of smaller look-up tables while maintaining the ability to handle high-dimensional modulation signals.
Solution Approach 2:
The patent introduces a new computational dimension by processing multiple bit groups in parallel through multiple computation units. Rather than increasing the size of a single look-up table to handle higher dimensions, the system adds computational units along a new dimension (parallel processing), thereby handling high-dimensional signals without proportionally increasing look-up table size.
2Quantity of substance
If the number of dimensions of modulation is increased, then the communication capacity is improved, but the circuit size increases
Solution Approach 1:
The circuit is segmented into multiple computation units, each handling a specific group of bits. This modular segmentation allows the overall circuit to handle high-dimensional modulation without requiring a single large monolithic circuit. Each computation unit can be implemented with compact logic, and their parallel arrangement efficiently utilizes circuit area.
Solution Approach 2:
Each computation unit processes only a partial set of bits (a specific group) rather than all bits in the sequence. This partial action approach allows the circuit to achieve the necessary processing capability through multiple specialized units rather than one unit that would require excessive circuit area to handle all bits comprehensively.
3Quantity of substance
If the number of dimensions of modulation is increased, then the communication capacity is improved, but the power consumption increases
Solution Approach 1:
The power consumption is segmented and distributed across multiple computation units rather than concentrated in a single unit. Each computation unit processes a subset of bits and can be powered down or operated at lower power when not actively processing, reducing overall power consumption compared to a single high-capacity unit that must remain fully powered to handle all bits.
Solution Approach 2:
Each computation unit performs partial processing on only its assigned bit group rather than excessive processing on all bits. This partial action reduces the computational workload and associated power consumption for each unit, and the distributed architecture allows for more efficient power management across the system as a whole.
Data Source
AI summary
An optical transmission apparatus (100) generates a second bit sequence B by encoding a first bit sequence b having forward error correction coding performed on a transmission bit sequence, maps the second bit sequence to a transmission symbol signal, and transmits an optical modulated signal generated by modulating an optical carrier wave into the transmission symbol signal. A symbol output unit (2020) generates a received symbol signal by demodulating an optical modulated signal received by an optical reception apparatus (2000). A first computation unit (2040) computes LLR(Bi) which is a log-likelihood ratio (LLR) of each bit Bi of the second bit sequence, using the received symbol signal. A second computation unit (2060) computes a log-likelihood ratio LLR(bi) of each bit bi of the first bit sequence from the LLR(Bi). A correspondence relationship between each bit of the first bit sequence and each bit of the second bit sequence is used in this computation. A decoding unit (2080) decodes the transmission bit sequence using the LLR(bi).