Sheida Nabavi

Welcome to my website

Hello,

I'm a postdoc Fellow in ECE department at Carnegie Mellon University (CMU). I got my PhD in December 2008. My advisor is professor Kumar. My main interest is signal processing and digital communications. Now, I'm working on signal processing (modeling, equalization and detection) for bit-patterned media recording channels. Here you can find some information about my research, education, awards and publications.

  

Research                                                                        

  • Equalization and Detection for bit-patterned media to mitigate inter-track interference

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 and beyond operating points, 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.

 

  • Modeling, Equalization and Detection for Holographic Data Storage Systems

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

Advisor

Publications

Journal Articles and Other Refereed Papers

  • S. Nabavi, B. V. K. Vijaya Kumar, J. A. Bain, C.Hogg, and S. Majetich, "Application of Image Processing to Characterize Media Noise in Bit-Patterned Media, " IEEE Transactions on Magnetics, 2009, under preparation.

  • S. Nabavi,, and B. V. K. Vijaya Kumar, " An Analytical Approach for Performance Evaluation of Bit-Patterned Media Channels,"  IEEE Journal on Selected Areas in Communications, 2009, submitted.

  • 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, Volume 44, Issue 11, Pages: 3789-3792, 2008..

  • S. Nabavi, B.V.K. Vijaya Kumar, and James A. Bain, “Mitigating the Effects of Track Mis-Registration in Bit-Patterned Media,” Proceedings of  IEEE International Conference on Communications, Pages: 2061-2065, 2008.

  • S. Nabavi, and B.V.K. Vijaya Kumar, “Two-Dimensional Generalized Partial Response Equalizer for Bit-Patterned Media,” Proceedings of IEEE International Conference on Communications, Pages: 6249 -6254, 2007.

  • 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.

  • 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  

  •  S. Nabavi, B. V. K. Vijaya Kumar, J. A. Bain, C.Hogg, and S. Majetich, "Characterization of Patterning Noise in Self-Assembled Nano-masks for Bit-Patterned Media Using Image Processing, " Proceedings of Intermag 2009 conference, submitted. 

  • S. Nabavi, B.V.K. Vijaya Kumar, and J. A. Bain, “Two-Dimensional Pulse Response and Media Noise Modeling for Bit-Patterned Media,” Proceeding of Intermag 2008 conference.  

  • 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.  

  • S. Nabavi, and B.V.K. Vijaya Kumar, “Iterative Decision Feedback Equalizer Detector for Holographic Data Storage Systems,” Proceedings of SPIE, Volume 6282, Pages: 62820T.1-62820T.8, 2006.

  • S. Nabavi, and B.V.K. Vijaya Kumar, “Detection Methods for Holographic Data Storage Channels,” Optical Data Storage (ODS) topical meeting, Pages:156-158, 2006.

  • 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), Paper TuB8, 2005.

  • 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

  • Best student paper award at the International Symposium on Optical Memory and Optical Data Storage (ISOM/ODS) 2005.

 

    

 

  Office: Hamerschlag Hall B200
   Phone: 412-268-4253
    Email: snabavi@ andrew.cmu.edu