Person:
Fekri, Faramarz

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    Volumetric storage limits and space-volume multiplexing trade-offs for holographic channels
    (Georgia Institute of Technology, 2010-01) Srinivasa, Shayan G. ; Momtahan, Omid ; Karbaschi, Arash ; McLaughlin, Steven W. ; Fekri, Faramarz ; Adibi, Ali
    We consider M-ary signaling in page-oriented holographic storage systems that multiplex pages using three methods: conventional angular multiplexing throughout the volume, localized recording, and a combination of angular multiplexing within localized recording. We study the mutual information transfer, which is increasingly easy to achieve in practice, between the recorded and recovered data, and use it to assess the storage density in these systems. We use the existing holographic channel model for the dominant Rician noise case for deriving the mutual information bound on the capacity and examine the interplay between the storage density and the number of recorded pages within the medium. We quantify through information-theoretical analysis that it is possible to obtain considerably higher storage capacities using gated localized holography than what can be achieved in conventional volume holography with angular multiplexing by appropriately optimizing the number of intensity levels for a given material constant and signal-to-noise ratio.
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    Low density parity check coding: applications and new challenges
    (Georgia Institute of Technology, 2009-03-18) Fekri, Faramarz
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    Low-density parity-check codes for volume holographic memory systems
    (Georgia Institute of Technology, 2003-02) Pishro-Nik, Hossein ; Rahnavard, Nazanin ; Ha, Jeongseok ; Fekri, Faramarz ; Adibi, Ali
    We investigate the application of low-density parity-check (LDPC) codes in volume holographic memory (VHM) systems. We show that a carefully designed irregular LDPC code has a very good performance in VHM systems. We optimize high-rate LDPC codes for the nonuniform error pattern in holographic memories to reduce the bit error rate extensively. The prior knowledge of noise distribution is used for designing as well as decoding the LDPC codes. We show that these codes have a superior performance to that of Reed-Solomon (RS) codes and regular LDPC counterparts. Our simulation shows that we can increase the maximum storage capacity of holographic memories by more than 50 percent if we use irregular LDPC codes with soft-decision decoding instead of conventionally employed RS codes with hard-decision decoding. The performance of these LDPC codes is close to the information theoretic capacity
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    Finite-field wavelet transforms and their application to error-control coding
    (Georgia Institute of Technology, 2000-08) Fekri, Faramarz