Efficient Two-Write WOM-Codes for Non-Volatile Memories

A write once memory (WOM) is defined as a class of storage medium, with each storage element known as a cell, that contains information. In the context of a WOM, there is an added constraint whereby the cells can only move irreversibly from a lower state to a higher state. One of the major challenges faced by non-volatile memories (NVM) is the limited number of erasure operations allowed before a cell is deemed as unreliable. In this letter, we propose a critical criterion to design binary WOM-codes with coding efficiencies higher than the state of the art codes. We further propose high-rate non-binary WOM-codes which are constructed based on these efficient binary WOM-codes. We show that the WOM-codes designed using the proposed criterion achieves a coding efficiency improvement of 2% for the binary codes and 0.2% for the non-binary codes.