Inkyu Lee

Sphere decoding for multiple antenna systems has been shown to achieve near-ML performance with low complexity. However, the achievement of such an excellent performance-complexity tradeoff is highly dependent on the initial choice of sphere radius. We present a new sphere decoding algorithm which is even less computationally complex than the original sphere decoder. Moreover, the complexity of the new sphere decoder is relatively insensitive to the initial choice of sphere radius. Thus, by maki

This paper investigates unmanned aerial vehicle (UAV) enabled secure communication systems where a mobile UAV wishes to send confidential messages to multiple ground users. To improve the security performance, a cooperative UAV is additionally considered that transmits the jamming signal. In this system, we maximize the minimum secrecy rate among the ground users by jointly optimizing the trajectory and the transmit power of the UAVs as well as the user scheduling. To efficiently solve this nonc

The performance of a serially concatenated system which includes a channel with memory preceded by a precoder as a rate-1 inner coder is presented. The effect of different precoders on the maximum-likelihood bit-error performance is analyzed. The precoder weight gain, which explains the good bit-error rate (BER) performance, is identified through a union bound analysis. Precoders are divided into two groups based on an analysis of the Euclidean distance and its multiplicity, and each precoder gr

The discrete multitone (DMT) modulation is considered to be a viable transmission scheme for high-speed subscriber loop. In this paper, the fast algorithm for computing the equalizer settings derived in [1] is extended and applied for the DMT in high-speed subscriber loop. The channel pulse response is assumed to be given by the channel identification method, and then the equalizer filter settings are computed. In simulations, a fast algorithm for the symbol spaced equalizer in a colored noise c

A novel fast algorithm for computing the minimum MSE decision feedback equalizer settings is proposed. The equalizer filters are computed indirectly, first by estimating the channel, and then by computing the coefficients in the frequency domain with the discrete Fourier transform (DFT). Approximating the correlation matrices by circulant matrices facilitates the whole computation with very small performance loss. The fractionally spaced equalizer settings are derived. The performance of the fas

A simple partial erasure model based on the effective reduction of the transition width in a magnetic recording system is presented. This model predicts nonlinear distortion accurately at high recording densities. This paper proposes several detection schemes incorporating this nonlinear model, and compares the performance with receivers designed for a linear channel. Simulations show that the nonlinear equalized maximum likelihood (EML) receiver outperforms other detectors in a nonlinearity-dom

Extracellular vesicles (EVs) are nanovesicles that are naturally released from cells in a lipid bilayer-bound form. A subset population with a size of 200 nm, small EVs (sEVs), is enticing in many ways. Initially perceived as mere waste receptacles, sEVs have revealed other biological functions, such as cell-to-cell signal transduction and communication. Besides their notable biological functions, sEVs have profound advantages as future drug modalities: (i) excellent biocompatibility, (ii) high

A novel architecture design to speed up the Viterbi algorithm is proposed. By increasing the number of states in the trellis, the serial operation of a traditional add-compare-select unit is transformed into a parallel operation, thus achieving a substantial speed increase. The proposed architecture would increase the speed by 33% at the expense of a fairly modest increase in area, thus becoming an attractive approach in high-speed applications. A simple example is shown to illustrate the propos

Space-time coding techniques are methods to improve transmission efficiency in radio channels by using multiple transmit and/or receive antennas. Bit-interleaved coded modulation gives good diversity gains with higher order modulation schemes using well known binary convolutional codes. By using orthogonal frequency division multiplexing (OFDM), wideband transmission can be achieved over frequency selective fading radio channels. In this paper, we combine these three ideas into a family of flexi

It has recently been shown that the capacity for multi-antenna dispersive radio channels is considerably higher than single receive and transmit antenna systems. In this article we demonstrate that high data rates can be achieved at low power levels for systems where the number of transmit antennas is typically larger than the number of receive antennas. We use bitinterleaved coded modulation, iterative decoding, and OFDM system building blocks for a flexible class of space-time coding systems w

This paper presents design and analysis of an HID lamp ballast for fast turn on characteristics and stable operation. It produces a high open circuit voltage for the ignition and it is controlled to effectively supply the power required to shorten the warm-up period after the breakdown. The lamp modeling by empirical data is presented. It is very effective in the design of the control loop in the steady-state operating region. A stable operation of the lamp power regulation in the steady state i

In this letter, we optimize tap spacings in a tapped delay line equalizer. We derive a set of nonlinear equations for the optimum tap spacings and tap weights for the decision feedback equalizer. A recursive numerical technique is used to obtain the optimum settings. With optimized tap spacings, the proposed solutions provide a performance upper bound for the decision feedback equalizer for a given number of taps.

A novel architecture design to speed up the Viterbi algorithm is proposed. By doubling the number of states in the trellis, the serial operation of a traditional add-compare-select (ACS) unit is transformed into a parallel operation, thus achieving a substantial speed increase. The use of the proposed architecture would increase the speed by 33% at the expense of a fairy modest increase in area, thus removing the Viterbi detector/decoder from the worst case speed bottleneck path in most high-spe

The use of RFID technology has come to a hot issue. There are many potential applications using RFID. In this paper we focused on RFID in the pharmaceutical supply chain, especially of Korea. First, we looked around RFID and related issues. And we examined the pharmaceutical supply chain in Korea and considerations to adopt RFID into the pharmaceutical supply chain. Finally, based on this study, we offered some suggestions to facilitate adoption of RFID into pharmaceutical supply chains in Korea

As the length of a channel response increases, the complexity of implementing the Maximum Likelihood Sequence Detector (MLSD) grows exponentially. Equalized Maximum Likelihood (EML) has been proposed to approach optimum performance with significantly reduced complexity. In this scheme, the performance degradation due to the colored error sequence is taken into account. A comparison with Partial Response Maximum Likelihood (PRML) is made for a magnetic recording channel. Our results indicate that