Ternary Signal Storage Device Viterbi Equalizer Intersymbol Interference
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Solution Overview
Problem
Conventional magnetic recording systems face issues with intersymbol interference when increasing recording density, leading to incorrect reproduction of information bits due to the use of only two signal levels.
Innovation Solution
A storage device and controller configuration that converts user data into three-ary symbols, allowing for three signal levels (+1, −1, and 0) to be recorded, using a Viterbi equalizer and LDPC decoder to perform simultaneous equalization and decoding, thereby increasing information density without degrading reproduction accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If recording density is increased in a conventional magnetic recording system, then storage capacity is improved, but intersymbol interference occurs causing incorrect reproduction
Solution Approach 1:
The patent changes the signal level parameter from binary (two levels) to ternary (three levels), allowing the recording medium to represent three distinct signal levels. This parameter change enables higher recording density while maintaining reproduction accuracy by reducing intersymbol interference through the additional signal level dimension.
2Device complexity
If only two signal levels are used, then device complexity is reduced, but information density is limited
Solution Approach 1:
The patent transitions from a binary signal system to a ternary signal system, changing the number of signal levels from two to three. This parameter change increases information density by allowing more distinct signal states while the Viterbi equalizer manages the increased complexity through systematic state tracking and likelihood calculation.
3Quantity of substance
If three-ary symbols are used to increase information density, then recording capacity is improved, but equalization complexity increases
Solution Approach 1:
The Viterbi equalizer employs feedback mechanisms by calculating likelihoods based on observed signal levels and using this information to determine the most probable transmitted symbols. The systematic feedback loop processes symbol sequences and adjusts decisions based on actual signal observations, managing the complexity of ternary symbol equalization.
Solution Approach 2:
The patent introduces an intermediary processing layer between the physical signal and the data interpretation, using the Viterbi equalizer as a mediator that processes the ternary symbols through a trellis diagram with multiple states. This intermediary structure simplifies the overall system by providing a systematic approach to handling the increased complexity of three-level signaling.
Data Source
AI summary
According to one embodiment, a storage device includes a data conversion unit that coverts user data of n bits, into m three-ary symbols, a recording medium that records the symbols as a signal of any one of three levels corresponding to values of the symbols, and a Viterbi equalizer that performs equalization of the m symbols simultaneously based on a signal read from the recording medium while setting the number of states as a power of 3 and using a trellis diagram having 2n branches, and calculates 2n likelihoods.