Concatenated BCH-LDPC Codes for Adaptive Holographic Storage
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Solution Overview
Problem
Holographic data storage systems face challenges in maintaining high accuracy, reliability, and throughput due to noise, interference, and asymmetric signal statistics, which result in high bit error rates and low signal-to-noise ratios, necessitating powerful error correction codes.
Innovation Solution
The construction of concatenated codes using a Bose-Chaudhuri-Hocquenghem (BCH) outer encoder and low-density parity check (LDPC) or turbo inner encoder/decoder, with programmable code rates and correction powers to adapt to varying channel conditions, implemented on field-programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If error-correcting codes are used to improve data storage accuracy and reliability, then the bit error rate and sector error rate decrease, but the coding gain requirement increases and the system becomes more complex
Solution Approach 1:
The patent applies segmentation by dividing the error correction process into two distinct stages using concatenated codes: an inner code (BCH) that corrects errors at the bit level, and an outer code (LDPC or turbo) that corrects errors at the sector level. This segmentation allows each code to be optimized for its specific function, achieving high reliability without requiring a single overly complex code structure.
Solution Approach 2:
The patent implements the nested doll principle by nesting the inner BCH code within the outer LDPC or turbo code structure. The inner code operates first on the raw data, and its output becomes the input for the outer code. This nested arrangement allows multiple layers of error protection to work together, with each layer addressing different types of errors, thereby achieving high coding gain while managing complexity through hierarchical organization.
2Quantity of substance
If high storage densities are achieved by closely spacing pages and books, then the storage capacity increases, but the signal-to-noise ratio decreases and error rates increase
Solution Approach 1:
The patent merges two different error correction coding schemes (BCH and LDPC/turbo) into a unified concatenated code system. This combination allows the system to simultaneously achieve high storage density and maintain reliability, as the inner BCH code provides strong protection against the high error rates caused by dense packing, while the outer code provides additional protection and enables achieving the required coding gain for high-density holographic storage.
Solution Approach 2:
The patent uses composite materials analogy by creating a composite error correction code structure that combines the strengths of different coding schemes. The inner BCH code provides robust protection against random errors typical in high-density storage, while the outer LDPC or turbo code provides protection against burst errors and achieves high coding gain. This composite approach allows the system to maintain reliability even as storage density increases and signal-to-noise ratio decreases.
3Adaptability or versatility
If the holographic channel uses asymmetric signal statistics, then the storage system can operate, but the error rates increase and stronger error correction is needed
Solution Approach 1:
The patent applies dynamics by making the error correction system adaptive to the asymmetric channel conditions. The outer code (LDPC or turbo) is designed with programmable parameters that can be adjusted based on the specific asymmetric statistics of the holographic channel. This dynamic adaptation allows the system to maintain reliability despite the inherent asymmetry in the channel, as the code parameters can be optimized for the specific error characteristics observed in practice.
Data Source
AI summary
Systems and methods for constructing concatenated codes for data storage channels, such as holographic storage channels, are provided. The concatenated codes include an outer BCH code and an inner iteratively decodable code, such as an LDPC code or turbo code. The correction power and coding rate of one or both of the codes may be programmable based on the channel characteristics and the desired SNR coding gain. The correction power and/or coding rate of the inner and/or outer code may also be dynamically adjusted in real-time to compensate for time-varying error conditions on the channel.