LDPC Code Optimization for Bandwidth-Constrained Turbo Equalization
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Solution Overview
Problem
Conventional communication systems face limitations in achieving high spectral efficiency and capacity due to bandwidth constraints, leading to increased complexity and power consumption in equalizers, especially in wideband systems with high throughput.
Innovation Solution
The implementation of a bandwidth constrained equalized transport (BCET) system that intentionally introduces memory into signals using pulse-shaping filters and optimized low-density parity-check (LDPC) error control codes, combined with iterative turbo equalization, to enhance information rates and reduce system complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional communication systems use traditional modulation formats without memory, then the system design is simpler, but the spectral efficiency cannot approach the Shannon limit
Solution Approach 1:
The patent changes the fundamental parameter of the channel by intentionally introducing memory effects through pulse-shaping filters that create controlled inter-symbol interference. This transforms the memoryless channel into a channel with memory, enabling the system to achieve spectral efficiencies closer to the Shannon limit while using iterative decoding techniques to manage the increased complexity
Solution Approach 2:
The patent implements iterative turbo equalization where the decoder and equalizer exchange information multiple times. The decoder provides feedback about estimated transmitted symbols to the equalizer, which refines its equalization based on this feedback. This iterative feedback mechanism enables the system to achieve near-Shannon-limit performance by progressively improving estimation accuracy
2Reliability
If error control coding is added to improve performance near Shannon limit, then spectral efficiency improves, but system complexity and power consumption increase
Solution Approach 1:
The patent merges the channel equalization and error correction decoding into a unified iterative turbo equalization framework. Instead of treating them as separate sequential stages, the equalizer and decoder are combined into a joint iterative processing structure where they exchange soft information, reducing overall system complexity while improving performance
Solution Approach 2:
The patent introduces an intermediary iterative exchange mechanism between the equalizer and decoder. Soft information (log-likelihood ratios) serves as the intermediary medium that allows the equalizer and decoder to cooperate and refine their estimates together, achieving better performance with manageable complexity
3Reliability
If iterative decoding is used to improve reliability, then error correction performance improves, but processing latency and power dissipation increase
Solution Approach 1:
The patent applies partial iteration by allowing the turbo equalization loop to terminate early when convergence is achieved. Instead of always performing a fixed number of iterations, the system performs only as many iterations as needed to reach the desired accuracy level, reducing average latency and power consumption while maintaining high reliability
Data Source
AI summary
In some embodiments, a bandwidth constrained equalized transport (BCET) communication system comprises a transmitter that transmits a signal, a communication channel that transports the signal, and a receiver that receives the signal. The transmitter can comprise a pulse-shaping filter that intentionally introduces memory into the signal, and an error control code encoder that is a low-density parity-check (LDPC) error control code encoder. The error control encoder comprises code that is optimized based on the intentionally introduced memory into the signal, a code rate, a signal-to-noise ratio, and an equalizer structure in the receiver. In some embodiments, the communication system is bandwidth constrained, and the transmitted signal comprises an information rate that is higher than for an equivalent system without intentional introduction of the memory at the transmitter.