Compressed Rank Modulation
Qing Li · 2012
We propose a generalization of Rank Modulation (RM) scheme, Compressed Rank Modulation (CRM) scheme for nonvolatile memories. CRM stores information in the multiset permutation induced by the charge levels of N =nΣi=1micells: set the ranks of the first m1highest charge level cells as 1, the ranks of the next m2highest charge level cells are 2, and the ranks of the last mnhighest charge level cells are n. The only allowed charge-placement method is the minimal-push-up aiming to minimize the increase of highest charge levels, and such minimization of highest charge level increase is defined as rewriting cost. CRM achieves a higher capacity comparing with RM, and maintains its advantages meanwhile. The closed-form formula for rewriting cost, sizes of balls, asymptotical rate analysis for rewriting codes, and one rewriting code construction are presented.