Codes Correcting Asymmetric/Unidirectional Errors along with Bidirectional Errors of Small Magnitude

Abstract

Dominant error sources in multi-level cell NAND Flash memories shift threshold voltage levels to either positive or negative values, thus errors are modeled by nonbinary unidirectional channels. However, bidirectional errors can also be caused when positive and negative errors have equivalent significance. Compared to unidirectional cases, error magnitude of bidirectional errors are considered to be small. In this correspondence, novel error correcting codes which correct limited magnitude asymmetric/unidirectional errors along with bidirectional errors of relatively small magnitude are presented. They can be used to reduce encoding and decoding complexity compared to conventional symmetric error correcting codes.

SEDC-Based Hardware-Level Fault Tolerance and Fault Secure Checker Design for Big Data and Cloud Computing

“…Only 14.42% of these injected faults resulted in bidirectional errors (BEs), while most of the faults caused unidirectional errors (UEs). This also proved the fact that most of the errors in VLSI circuits result in UEs at the output [19][20][21]. Even though SEDC is an AUED scheme, and it provides 100% fault coverage against UEs, it also successfully detected 47.62% of the BEs, as shown in Table 5.…”

“…Transient faults or soft errors are transient-induced events on memory and logic circuits caused by the striking of rays emitted from an IC package and high energy alpha particles from cosmic rays [14][15][16][17][18]. Also, in multilevel cell memories like NAND Flash memories, these errors are mostly caused by cell-to-cell interference and data retention errors [19]. Physical protection such as shielding, temperature control, and grounding circuits are not always feasible; hence, in such cases, concurrent error detecting (CED) methods are employed for protection against these errors.…”

“…Since CED circuits add to the overall area and delay of the system, the selection of appropriate error detecting, and even error correcting, circuits for a particular application leads to an efficient design [18]. It has been reported that the biggest portion of errors that occur in VLSI circuits and memories are related to unidirectional errors (UE) [19][20][21] because these errors shift threshold voltage levels to either the positive or negative side [22], causing the circuit node logic from "0" to "1" or from "1" to "0," but not both at the same time.…”