Performance Enhancement of Hybrid TDOA/AOA Using Multipath Delay Estimation

Wireless Personal Communications - Wireless solar blind ultraviolet (UV) scattering communication is a new type of atmosphere optics communication technology with the important and potential...     

New Organic Nonlinear Optical Polyene Crystals and Their Unusual Phase Transitions

A series of new nonlinear optical chromophores based on configurationally locked polyenes (CLPs) with chiral pyrrolidine donors are synthesized. All CLP derivatives exhibit high thermal stability with decomposition temperatures T_d at least > 270 °C. Acentric single crystals of enantiopure D ‐ and L ‐prolinol‐based chromophores with a monoclinic space group P2₁ exhibit a macroscopic second‐order nonlinearity that is twice as large than that of analogous dimethylamino‐based crystal. This is attributed to a strong hydrogen‐bonded polar polymer‐like chain built by these molecules, which is aligned along the polar crystallographic b‐axis. Five α‐phase CLP crystals with different donors grown from solution exhibit a reversible or irreversible thermally induced structural phase transition to a β‐phase. These phase transitions are unusual, changing the crystal symmetry from higher to lower at increasing temperatures, for example, from centrosymmetric to non‐centrosymmetric, enhancing their macroscopic second‐order nonlinear optical properties.     

Relations among Security Models for Authenticated Key Exchange

Usually, key‐establishment protocols are suggested in a security model. However, there exist several different security models in the literature defined by their respective security notions. In this paper, we study the relations between the security models of key establishment. For the chosen security models, we first show that some proven key‐establishment protocols are not secure in the more restricted security models. We then suggest two compilers by which we can convert a key‐establishment protocol that is secure in a specific security model into a key‐establishment protocol that is still secure in a more restricted security model.     

Ku-band stop filter implemented on a high resistivity silicon with inverted microstrip line photonic bandgap (PBG) structure

We have developed the inverted microstrip line photonic bandgap (IML-PBG) structure using the surface micro-machining technology on the high resistivity silicon (HRS) substrate. Because, when the IML was fabricated, the holes for removing a sacrificial layer were necessary, we have introduced these holes into the PBG structure for the Ku-band stop filter (BSF). Rectangular spiral PBG structure showed the notch characteristics and the array with suitable distance showed the stop band with under -20 dB from 15 to 19 GHz and under -3 dB pass-band loss.     

KWTA networks and their applications

Winner-Take-All (WTA) or K-Winner-Take-All (KWTA) networks have been frequently used as the basic building blocks of complex neural networks. This paper introduces a new selection rule for network connections that implements stable KWTA networks. To widen the applications of WTA networks, a new class of WTA networks is proposed, and their efficient design methods are presented. We demonstrate the properties of the generalized class of WTA networks, through three application examples.     

3D Localization for Launch Vehicle Using Virtual TOA and AOA of Ground Stations

Wireless Personal Communications - Generally, a ground telemetry station for a launch vehicle (LV) includes a tracking function only; therefore, position measurements for LV depend on received...     

A Framework for MPEG‐4 Contents Delivery over DMB

Digital Multimedia Broadcasting (DMB) is an upcoming standard in Korea used to provide mobile multimedia broadcasting service based on the Eureka‐147 Digital Audio Broadcasting (DAB) system. The current dominant multimedia coding standard, MPEG‐4, is foreseen to play an important role in forthcoming DMB services. However, the current approaches for transporting MPEG‐4 content over DMB networks are not optimized. To address this issue we propose a novel MPEG‐4 stream multiplexer, called M4SMux, which provides better stream multiplexing and delivery over DMB networks. M4SMux features an MPEG‐4 elementary‐stream interleaving mechanism that reduces the multiplexing overhead and a multiplex configuration mechanism that utilizes M4SLinkTable for easy content access. In addition, we propose an error correction method which enhances transport efficiency.     

Analysis of the hemispheric asymmetry using fractal dimension of a skeletonized cerebral surface

We investigated hemispheric asymmetry using the fractal dimension (FD) of the skeletonized cerebral surface. Sixty-two T1-weighted magnetic resonance imaging volumes from normal Korean adults were used. The skeletonization of binary volume data, which corresponded to the union of the gray matter and cerebrospinal flow classified by fuzzy clustering, was performed slice by slice in the sagittal direction, and then skeletonized slices were integrated into the three-dimensional (3-D) hemisphere. Finally, the FD of the 3-D skeletonized cerebral surface was calculated using the box-counting method. We measured the FD of the skeletonized cerebral surface and the volumes of intracranial gray matter and white matter for the whole hemispheres and obtained the hemispheric asymmetries of each measurement. The FD, the gray matter, and the white matter volumes for the whole hemispheres decreased in the old group. The asymmetry of the FD revealed a significant right-greater-than-left asymmetry showed rightward, but did not change according to age and gender. None of the intracranial gray matter or white matter volumes showed any significant asymmetric changes. It could be said that the FD of the skeletonized cerebral surface is a novel measure of cerebral asymmetry.     

Effect of tap spacing on the performance of direct-sequencespread-spectrum RAKE receiver

The effect of tap spacing on the performance of a RAKE receiver is analyzed analytically in a frequency-selective fading channel. A continuous time multipath fading channel model is used for the analysis, and the expression of the correlation between the desired signals, interference signals, and noise signals at the output of each branch of the RAKE receiver is derived for various chip waveforms. Since the noise components of each branch signal are correlated to each other, an optimum combining rule based on the maximum-likelihood criterion is derived to gain utmost performance. It is shown that the performance of the system can be improved by setting the tap spacing of the RARE receiver below the chip duration when the bandwidth of the transmitted signal is larger than the inverse of the chip duration. Also, it is shown that the normalized capacity of the system can be increased by using a chip waveform occupying wider bandwidth, which takes advantage of the increased diversity gain merits of a wide-band code-division multiple-access system at the same chip rate. It is noted that the derived combining rule gives diversity gain against the fading process as well as noise whitening processing gain against multiple-access interference at the same time     

Broad-band erbium-doped fiber amplifier with double-passconfiguration

We demonstrate a broad-band silica-based erbium-doped fiber amplifier (EDFA) with double-pass configuration. The signal gain and noise figure are obtained more than 24 dB and less than 6 dB, respectively, for 1526-1562 nm and 1569-1605 nm. The same signal gain can be achieved with 53% less pump power and 45% shorter erbium-doped fiber length, compared to a conventional parallel type EDFA. Furthermore, the noise figure and power conversion efficiency are improved for the wavelength range