# Model-Based Detector for SSDs in the Presence of Inter-cell Interference

## TL;DR

This paper introduces a novel model-based detector for SSDs that accounts for inter-cell interference, significantly reducing bit error rates through advanced channel modeling and iterative decoding techniques.

## Contribution

The paper proposes a finite-state Markov channel model and an iterative detection scheme to improve error correction in SSDs affected by inter-cell interference.

## Key findings

- Achieves up to 99.99% BER reduction with high-precision output.
- Iterative detector-decoder scheme improves performance in quantized output scenarios.
- Model accurately captures inter-cell interference effects, enhancing decoding accuracy.

## Abstract

In this paper, we consider the problem of reducing the bit error rate of flash-based solid state drives (SSDs) when cells are subject to inter-cell interference (ICI). By observing that the outputs of adjacent victim cells can be correlated due to common aggressors, we propose a novel channel model to accurately represent the true flash channel. This model, equivalent to a finite-state Markov channel model, allows the use of the sum-product algorithm to calculate more accurate posterior distributions of individual cell inputs given the joint outputs of victim cells. These posteriors can be easily mapped to the log-likelihood ratios that are passed as inputs to the soft LDPC decoder. When the output is available with high precision, our simulation showed that a significant reduction in the bit-error rate can be obtained, reaching $99.99\%$ reduction compared to current methods, when the diagonal coupling is very strong. In the realistic case of low-precision output, our scheme provides less impressive improvements due to information loss in the process of quantization. To improve the performance of the new detector in the quantized case, we propose a new iterative scheme that alternates multiple times between the detector and the decoder. Our simulations showed that the iterative scheme can significantly improve the bit error rate even in the quantized case.