Current flash memory technology is focused onudcost minimization of the stored capacity. However, the resultingudapproach supports a relatively small number of write-eraseudcycles. This technology is effective for consumer devices (smartphonesudand cameras) where the number of write-erase cycles isudsmall, however, it is not economical for enterprise storage systemsudthat require a large number of lifetime writes.ududOur proposed approach for alleviating this problem consists ofudthe efficient integration of two key ideas: (i) improving reliabilityudand endurance by representing the information using relativeudvalues via the rank modulation scheme and (ii) increasing theudoverall (lifetime) capacity of the flash device via rewriting codes,udnamely, performing multiple writes per cell before erasure.ududWe propose a new scheme that combines rank-modulationudwith rewriting. The key benefits of the new scheme include: (i)udthe ability to store close to 2 bits per cell on each write, andudrewrite the memory close to q times, where q is the numberudof levels in each cell, and (ii) efficient encoding and decodingudalgorithms that use the recently proposed polar WOM codes.
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