Amalgamated q-ary codes for multi-level flash memories

A flash memory is a non-volatile memory based on electron storing mechanism. A multi-level flash memory cell can store one of q symbols (q >; 2). As q increases, the data becomes less reliable and the probability it may be distorted by different types of errors increases. This paper presents an amalgamated q-ary code capable of correcting a mixture of t
_s
symmetric errors and additional t
_a
asymmetric errors of limited magnitude l. In the proposed code, each q-ary codeword is composed of n multi-bit symbols, each multi-bit (i.e. q-ary) symbol is viewed as two sub-symbols over two different alphabets. The new construction has higher code rate than the conventional single-alphabet code.