34,581 research outputs found
An Iteratively Decodable Tensor Product Code with Application to Data Storage
The error pattern correcting code (EPCC) can be constructed to provide a
syndrome decoding table targeting the dominant error events of an inter-symbol
interference channel at the output of the Viterbi detector. For the size of the
syndrome table to be manageable and the list of possible error events to be
reasonable in size, the codeword length of EPCC needs to be short enough.
However, the rate of such a short length code will be too low for hard drive
applications. To accommodate the required large redundancy, it is possible to
record only a highly compressed function of the parity bits of EPCC's tensor
product with a symbol correcting code. In this paper, we show that the proposed
tensor error-pattern correcting code (T-EPCC) is linear time encodable and also
devise a low-complexity soft iterative decoding algorithm for EPCC's tensor
product with q-ary LDPC (T-EPCC-qLDPC). Simulation results show that
T-EPCC-qLDPC achieves almost similar performance to single-level qLDPC with a
1/2 KB sector at 50% reduction in decoding complexity. Moreover, 1 KB
T-EPCC-qLDPC surpasses the performance of 1/2 KB single-level qLDPC at the same
decoder complexity.Comment: Hakim Alhussien, Jaekyun Moon, "An Iteratively Decodable Tensor
Product Code with Application to Data Storage
Multi-track 2D joint signal detection and decoding for TDMR system using single parity-check coding.
Performance of 2D SOVA along and across track in shingled magnetic recording media
Serial Concatenation of Two Dimensional Soft Output Viterbi Algorithm (2D-SOVA) and regular Viterbi Algorithm (VA) for 2D equalisation and detection of Shingled Magnetic Recording (SMR) media provides excellent performance as compared to the use of 1 Dimensional (1D) maximum likelihood detector. In this paper, we implement and evaluate the performances of two versions of it. The first version performs 2D SOVA along the tracks to eliminate the effect of inter-symbol interference (ISI) and then the Viterbi detector across the tracks to remove inter-track interference (ITI). The second version carries out 2D-SOVA across the tracks and VA along the tracks. The results for high ITI and ISI show a better performance when using 2D-SOVA across the track with a small difference in computational complexity in favour of 2D-SOVA across the tracks
On Coding and Detection Techniques for Two-Dimensional Magnetic Recording
Edited version embargoed until 15.04.2020
Full version: Access restricted permanently due to 3rd party copyright restrictions. Restriction set on 15/04/2019 by AS, Doctoral CollegeThe areal density growth of magnetic recording systems is fast approaching the superparamagnetic limit for conventional magnetic disks. This is due to the increasing demand for high data storage capacity. Two-dimensional Magnetic Recording (TDMR) is a new technology aimed at increasing the areal density of magnetic recording systems beyond the limit of current disk technology using conventional disk media. However, it relies on advanced coding and signal processing techniques to achieve areal density gains. Current state of the art signal processing for TDMR channel employed iterative decoding with Low Density Parity Check (LDPC) codes, coupled with 2D equalisers and full 2D Maximum Likelihood (ML) detectors. The shortcoming of these algorithms is their computation complexity especially with regards to the ML detectors which is exponential with respect to the number of bits involved. Therefore, robust low-complexity coding, equalisation and detection algorithms are crucial for successful future deployment of the TDMR scheme.
This present work is aimed at finding efficient and low-complexity coding, equalisation, detection and decoding techniques for improving the performance of TDMR channel and magnetic recording channel in general. A forward error correction (FEC) scheme of two concatenated single parity bit systems along track separated by an interleaver has been presented for channel with perpendicular magnetic recording (PMR) media. Joint detection decoding algorithm using constrained MAP detector for simultaneous detection and decoding of data with single parity bit system has been proposed. It is shown that using the proposed FEC scheme with the constrained MAP detector/decoder can achieve a gain of up to 3dB over un-coded MAP decoder for 1D interference channel. A further gain of 1.5 dB was achieved by concatenating two interleavers with extra parity bit when data density along track is high. The use of single bit parity code as a run length limited code as well as an error correction code is demonstrated to simplify detection complexity and improve system performance.
A low-complexity 2D detection technique for TDMR system with Shingled Magnetic Recording Media (SMR) was also proposed. The technique used the concatenation of 2D MAP detector along track with regular MAP detector across tracks to reduce the complexity order of using full 2D detection from exponential to linear. It is shown that using this technique can improve track density with limited complexity. Two methods of FEC for TDMR channel using two single parity bit systems have been discussed. One using two concatenated single parity bits along track only, separated by a Dithered Relative Prime (DRP) interleaver and the other use the single parity bits in both directions without the DRP interleaver. Consequent to the FEC coding on the channel, a 2D multi-track MAP joint detector decoder has been proposed for simultaneous detection and decoding of the coded single parity bit data. A gain of up to 5dB was achieved using the FEC scheme with the 2D multi-track MAP joint detector decoder over un-coded 2D multi-track MAP detector in TDMR channel. In a situation with high density in both directions, it is shown that FEC coding using two concatenated single parity bits along track separated by DRP interleaver performed better than when the single parity bits are used in both directions without the DRP interleaver.9mobile Nigeri
ON REDUCING THE DECODING COMPLEXITY OF SHINGLED MAGNETIC RECORDING SYSTEM
Shingled Magnetic Recording (SMR) has been recognised as one of the alternative technologies
to achieve an areal density beyond the limit of the perpendicular recording technique,
1 Tb/in2, which has an advantage of extending the use of the conventional method
media and read/write head.
This work presents SMR system subject to both Inter Symbol Interference (ISI) and Inter
Track Interference (ITI) and investigates different equalisation/detection techniques in order
to reduce the complexity of this system.
To investigate the ITI in shingled systems, one-track one-head system model has been extended
into two-track one-head system model to have two interfering tracks. Consequently,
six novel decoding techniques have been applied to the new system in order to find the Maximum
Likelihood (ML) sequence. The decoding complexity of the six techniques has been
investigated and then measured. The results show that the complexity is reduced by more
than three times with 0.5 dB loss in performance.
To measure this complexity practically, perpendicular recording system has been implemented
in hardware. Hardware architectures are designed for that system with successful
Quartus II fitter which are: Perpendicular Magnetic Recording (PMR) channel, digital
filter equaliser with and without Additive White Gaussian Noise (AWGN) and ideal
channel architectures. Two different hardware designs are implemented for Viterbi Algorithm
(VA), however, Quartus II fitter for both of them was unsuccessful. It is found that,
Simulink/Digital Signal Processing (DSP) Builder based designs are not efficient for complex
algorithms and the eligible solution for such designs is writing Hardware Description
Language (HDL) codes for those algorithms.The Iraqi Governmen
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