Changkyu Seol

Error control coding and signal processing for flash memories

With the rapid advances in the area of memory product, it has become more and more important to maintain its reliability while increasing the density and speed performance. Particularly, flash memory products have inherent difficulties in lengthening the limited lifetime due to the degradation of memory cell reliability caused by repeated read and/or write operations. To increase the benefits of high density flash memory, more advanced techniques such as multi-leveling the cell and signal processing has been adopted to the flash memory products. In this paper, arising challenges that leading engineers in semiconductor memory industries have confronted will be shared to further develop cutting-edge flash memory products.

Coverage analysis of downlink cellular orthogonal frequency-division multiple-access networks using moment generating functions

In this study, the coverage of downlink cellular orthogonal frequency-division multiple-access networks transmitting one quadrature-amplitude modulation symbol per hop is analysed. The coverage probability is first defined by using an upper bound on the bit error rate (BER) of a bit-interleaved coded modulation system. Moreover then, the moment generating functions of the legacy Gaussian and Laplacian metrics (LMs) for soft-decision decoding of an employed error-correcting code are derived for computing the upper bound on the BER and the corresponding coverage probability of the networks. Numerical results demonstrate that due to the impulsive nature of the inter-cell interference for moderate-to-small cell loads, the networks using the LM for soft-decision decoding significantly outperform those employing the legacy Gaussian metric in terms of the achievable cell radius and the amount of the average transmit power reduction.