Ji-Woong Choi

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—The performance of channel estimation in orthogonal frequency division multiplexing (OFDM) systems significantly depends on the pilot signal, which is usually scattered in time and frequency domains. For a given pilot density, the authors optimally design the pilot pattern so as to minimize the mean squared error (MSE) of the channel estimate with the use(More)
—The efficient service of a tremendous number of machine-type devices with heterogeneous traffic types may consider simple random access as a solution. For more rigorous analysis of system performance in multicell environments, it is required to consider not only the packet collisions within the same cell but also the interference from other cells. This(More)
Noncoding small regulatory RNA molecules control gene expression and microRNAs provide one of the best examples in eukaryotes. However, bacterial RNAs of comparable size to eukaryotic microRNAs have received little attention. Here, we demonstrate the existence of microRNA-size, small RNAs (msRNAs) in the model bacterium Escherichia coli. We examined the(More)
In the present study, we investigated the possible mechanisms of cellular injury induced by zinc in rat primary astrocytes and C6 glioma cells. Reactive oxygen species (ROS) production, cellular glutathione (GSH) level and mitochondrial transmembrane potential were examined. Exposure to 200-300 microM Zn2+ for 24 h resulted in significant lactate(More)
– In order to achieve the goals of business, various channel of communications to customers have to be developed through technology. In the present day banking, total automation of banking operation and is an imperative for all banks to attract more customers, provide efficient service and survive the competition ,apart from achieving the profit ,which is(More)
The performance of channel estimation in OFDM systems significantly depends on the pilot signal, which is usually scattered in the time and frequency domains. For a given pilot density, we analytically design the optimum pilot pattern that minimizes the mean square error of the channel estimate obtained with the use of general interpolators. The analytic(More)
—When a preamble signal is repeated multiple times in OFDM systems, we derive joint maximum likelihood (ML) estimation of the frame timing (FT) and carrier frequency offset (CFO). Unlike conventional estimators which use correlation of adjacent repetition patterns only or some specific sets of patterns, the joint ML estimation exploits correlation of any(More)
NEMO accelerates the handover procedure through tunneling, it may cause a serious burden of the tunnel between Mobile Access Gateways (MAGs). This is because all packets destined for Mobile Network Nodes (MNNs) are forwarded to a New MAG (NMAG) through the tunnel between MAGs. This problem becomes more critical, as the number of MNNs is large and there(More)