Electrical Engineering-Systems Dept.

סמינר מחלקתי

You are invited to attend a lecture by

Eyal En Gad

(Graduate Student at the California Institute of Technology)

on the subject:

Rank-Modulation Rewriting Codes for Flash Memories

Current flash memory technology supports a relatively small number of write-erase cycles. This technology is effective for consumer devices (smartphones and cameras) where the number of write-erase cycles is small, however, it is not economical for enterprise storage systems that require a large number of lifetime writes. 

In this talk I will present a novel approach for alleviating this problem. The approach consists of the efficient integration of two key ideas: (i) improving reliability and endurance by representing the information using relative values via the rank modulation scheme and (ii) increasing the overall (lifetime) capacity of the flash device via rewriting codes, namely, performing multiple writes per cell before erasure. 

We propose a new scheme that combines rank-modulation with rewriting. The key benefits of the new scheme include: (i) the ability to store close to 2 bits per cell on each write, and rewrite the memory close to q times on average, where q is the number of levels in each cell, (ii) efficient encoding and decoding algorithms that use the recently proposed polar WOM codes, and (iii) since our scheme requires large values of q that are not feasible in current technologies, we propose a new circuit-level architecture that enables a large q value and is using existing device technologies.

The talk is based on joint work with Eitan Yaakobi, Anxiao (Andrew) Jiang and Jehoshua Bruck.