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Research
Among the most promising approaches proposed to
increase the storage density of magnetic media up to 1 Tbit/in2
and to circumvent the super-paramagnetic limit, is the use of
bit-patterned media . In bit-patterned media each bit is stored in a
single-domain magnetic island. In addition to addressing the
super-paramagnetic effect, because of the nonmagnetic region between
islands, bit-patterned media offers the advantages of reducing transition
and track edge noise, reducing or eliminating non-linear bit shift and
simplifying tracking. In high-density bit-patterned media, islands are
distributed closely. Therefore, inter-track interference (ITI) can have a
significant impact on the replay signal of the main data track. Also,
track misregistration (TMR) can increase ITI due to the read head sensing
the islands in the adjacent tracks. If the ITI is ignored, the channel
performance will degrade significantly. Therefore for patterned media,
both inter-symbol interference (ISI) and ITI have to be considered. In
this project, with concentrate on the 1 Tbit/in2 operating
point, we are designing and analyzing different methods of equalization
and detection to combat ITI and ISI on the performance of the channel in
terms of bit error rate (BER) against signal to noise ratio (SNR). In
bit-patterned media, the writing frequency and track positions are fixed
by the patterning of the islands. Fixed distribution of the islands and
utilizing the two-dimensional (2D) pulse response to model ISI and ITI, allow
us the advantage of using 2D approaches.
Holographic Data Storage system (HDS) is a promising digital
storage technology because of its potential for high data storage density, high
data rate and short access time. The ability to multiplex several pages into a
given volume of the medium leads to potentially high volumetric storage
densities. Also HDS uses a parallel two-dimensional or page-like format in
recording and retrieval leading to high data rates and short access times. When
the number of pages multiplexed in the same volume is increased, the diffraction
efficiency during read-back decreases, resulting in low Signal to Noise Ratio (SNR).
Furthermore, increasing the data density leads to more Inter symbol Interference
(ISI). In addition to low SNR and high ISI, optical and electronic noises affect
the Bit Error Rate (BER) adversely and thus limit the capacity of the HDS. Two
dimensional equalization and detection methods should be employed to mitigate
the effects of ISI and noise and to increase the storage capacity. In this
project we are developing channel models based on physical impairments in HDS.
We are also investigating different methods of identifying channels from
real data. We are designing and analyzing various two dimensional
equalization/detection methods. We will begin with simple equalization
techniques like linear equalization and then will consider advanced
methods based on partial response, decision feedback and nonlinear
equalization.
Education
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Ph.D. candidate,
Carnegie Mellon University (CMU),
Electrical and Computer Engineering (ECE)
Department, Pittsburgh, PA.
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M.S.,
Carnegie Mellon University (CMU),
Electrical and Computer Engineering (ECE)
Department, Pittsburgh, PA.
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B.S.,
Sharif (Arya-Mehr) University of Technology,
Tehran, Iran.
Advisor
Publications
J ournal Articles and Other
Refereed Papers
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S. Nabavi,
B.V.K. Vijaya Kumar, and J. A. Bain, “Two-Dimensional Pulse Response and Media Noise Modeling for Bit-Patterned Media,” IEEE Transactions on Magnetics, submitted.
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S. Nabavi,
and B.V.K. Vijaya Kumar, “Media Noise Modeling for Bit-Patterned Media,”
IEEE Global Communications Conference,
2008, submitted.
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S. Nabavi,
B.V.K. Vijaya Kumar, and James A. Bain, “Mitigating the Effects of Track Mis-Registration in Bit-Patterned Media,”
IEEE International Conference on Communications,
2008, accepted.
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S. Nabavi,
and B.V.K. Vijaya Kumar, “Two-Dimensional Generalized Partial Response Equalizer for Bit-Patterned Media,”
Proceeding
of
IEEE International Conference on Communications,
Pages: 6249 -6254, 2007.
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S. Nabavi, and
B.V.K. Vijaya Kumar, “Modifying Viterbi Algorithm to Mitigate Inter-track
Interference for Bit-Patterned Media,” IEEE Transactions on Magnetics,
Volume 43, Issue 6, Pages: 2274-2276, 2007.
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S. Nabavi, and B.V.K. Vijaya Kumar, “Application of Linear and Nonlinear Equalization Methods for Holographic Data Storage,”
Japanese Journal of Applied Physics (JJAP), Volume 45 (1), Issue 2B, Pages: 1079-1083,
2006.
Conference Papers
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S. Nabavi, B.V.K. Vijaya Kumar, and J. A. Bain, “Two-Dimensional Pulse Response and Media Noise Modeling for Bit-Patterned Media,”
Intermag 2008 conference, accepted.
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S. Nabavi,
and B.V.K. Vijaya Kumar, “Modifying Viterbi Algorithm to Mitigate Inter-track Interference for Bit-Patterned Media,”
Proceedings of the 10th joint MMM/Intermag conference, 2007.
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S. Nabavi,
and B.V.K. Vijaya Kumar, “Iterative Decision Feedback Equalizer Detector for Holographic Data Storage Systems,”
Proceedings of SPIE, Volume 6282, 62820T, 2006.
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S. Nabavi, and B.V.K. Vijaya Kumar, “Detection Methods for Holographic Data Storage Channels,”
Optical Data Storage (ODS) topical meeting, 2006.Holographic Data Storage Systems,” Proceeding of SPIE, Vol. 6282, 62820T, 2006.
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S. Nabavi, and B.V.K. Vijaya Kumar, “Comparative Evaluation of Equalization Methods for Holographic Data Storage Channels,”
International Symposium on Optical memory and Optical Data Storage (ISOM/ODS), 2005.
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L. Ramamoorthy,
S. Nabavi, and B.V.K. Vijaya Kumar, “Physical Channel Model for Holographic Data Storage Systems,”
The 17th annual meeting of IEEE, LEOS 2004, Volume 2, Pages: 997-999, 2004.
Awards
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Office:
Hamerschlag Hall B200
Phone: 412-268-4253
Email:
snabavi@ andrew.cmu.edu |
