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 become less reliable and the probability it may be distorted by different types of errors increases. Previous works have dealt with q-ary codes handling different types of errors with specifi c restrictions, though none have focused on the general combination of allowing both symmetric and asymmetric errors to occur simultaneously. This work 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 amalgamated 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. Furthermore, the new construction is generalized to a code structure capable of correcting multiple errors with various magnitudes that occur with different probabilities. The impact of adding feedback to the system is also examined. The new construction outperforms the conventional single-alphabet code in terms of code rate and decoding error probability.
* The research presented in the seminar was carried out towards the M.Sc. degree, with the supervision of Dr. Osnat Keren