Transmission of Traffic Information Using a Terrestrial Digital Multimedia Broadcasting System

This letter introduces an efficient transmission of traffic information through a terrestrial digital multimedia broadcasting system, which is a multimedia and mobility empowered option of the European digital audio broadcasting system. By adapting Korean characteristic traffic information into the transport protocol expert group messages in the traffic information delivery, a highly efficient traffic information system was implemented and tested in Korea.     

Enhanced-xVSB system development for improving ATSC terrestrial DTV transmission standard

This paper describes advanced dual stream system for improving mobile/pedestrian reception performance to the ATSC DTV 8-VSB transmission standard. E-xVSB system can transmit a mixture of normal (8-VSB) stream and enhanced (robust) stream. The robust stream has a higher threshold of visibility (TOV) compared to the standard stream, and legacy receivers ignore the robust packets. Thus, Enhanced-xVSB system is fully backward compatible with a current ATSC standard. For more robust transmission support, E-xVSB system adopts a reduced constellation method as well as enhanced trellis-coded modulation scheme. E-xVSB system supports a variety of enhanced modulation schemes: Pseudo-2VSB, Enhanced-4VSB, modified Enhanced-8VSB and Hybrid-VSB. Proposed system has been tested in the Lab, and the testing results are shown in this paper.     

Implementation of an SDR platform using GPU and its application to a 2?��?2 MIMO WiMAX system

Conventional communication systems have been implemented using digital signal processors (DSPs) and/or field programmable gate arrays (FPGAs), especially for software defined radio (SDR) functionality. We propose a scheme that uses a graphics processing unit (GPU) in place of the conventional DSPs or FPGAs for the implementation of an SDR-based communication system. The GPU, a high-speed parallel processor with multiple arithmetic logic units, is adopted for the signal processing of the physical layer required for the parallel processing in an SDR system. The compute unified device architecture (CUDA) based on the C language provides a software development kit (SDK) for the modem application of the GPU. Therefore we utilize the CUDA SDK to implement the real-time modem function. This paper presents an implementation of a 2 × 2 multiple-input multiple-output (MIMO) WiMAX system employing a GPU as the real-time modem. By installing a radio frequency module on top of the GPU modem, we implement a real-time transmission system for video data. The performance of the proposed GPU-based system is demonstrated by comparing its operation time against that of the conventional DSP-based system.     

ε‐Branched Flexible Side Chain Substituted Diketopyrrolopyrrole‐Containing Polymers Designed for High Hole and Electron Mobilities

Based on the integrated consideration and engineering of both conjugated backbones and flexible side chains, solution‐processable polymeric semiconductors consisting of a diketopyrrolopyrrole (DPP) backbone and a finely modulated branching side chain (ε‐branched chain) are reported. The subtle change in the branching point from the backbone alters the π?π stacking and the lamellar distances between polymer backbones, which has a significant influence on the charge‐transport properties and in turn the performances of field‐effect transistors (FETs). In addition to their excellent electron mobilities (up to 2.25 cm² V^?1 s^?1), ultra‐high hole mobilities (up to 12.25 cm² V^?1 s^?1) with an on/off ratio (I_on/I_off) of at least 10⁶ are achieved in the FETs fabricated using the polymers. The developed polymers exhibit extraordinarily high electrical performance with both hole and electron mobilities superior to that of unipolar amorphous silicon.     

Organic Semiconductor Cocrystal for Highly Conductive Lithium Host Electrode

In this work, a highly conductive organic cocrystal is investigated as an anode material for conducting agent‐free lithium‐ion battery (LIB) electrodes. A unique morphology of semiconducting fullerene (C₆₀) and contorted hexabenzocoronene (cHBC) is developed as a cocrystal that efficiently enhances the electron transfer during discharge and charge processes due to the formation of a well‐defined junction between C₆₀ and cHBC. In particular, the present study reveals the exact cocrystal phase of orthorhombic Pnnm using grazing incidence X‐ray diffraction characterization and computational methods. The detailed cocrystal structure analysis indicates that the columnar structure of C₆₀/cHBC cocrystal facilitates the reliable vacant sites for Li⁺ storage, which ultimately enhances the reversible capacity to 330 mAh g^–1 at 0.1 A g^–1 with long cyclability of 600 cycles in the absence of a conducting agent. Furthermore, the rate performance of the C₆₀/cHBC cocrystal anode is improved compared to that of the graphite anode, indicating that the cocrystal formation between C₆₀ and cHBC enhances the charge transport at a high current density. It demonstrates that the approach of this study can be a promising strategy for preparing conducting agent‐free organic cocrystal anodes, which also provides a viable design rule for high‐performance LIBs electrodes.     

Spatial Modulation

Spatial modulation (SM) is a recently developed transmission technique that uses multiple antennas. The basic idea is to map a block of information bits to two information carrying units: 1) a symbol that was chosen from a constellation diagram and 2) a unique transmit antenna number that was chosen from a set of transmit antennas. The use of the transmit antenna number as an information-bearing unit increases the overall spectral efficiency by the base-two logarithm of the number of transmit antennas. At the receiver, a maximum receive ratio combining algorithm is used to retrieve the transmitted block of information bits. Here, we apply SM to orthogonal frequency division multiplexing (OFDM) transmission. We develop an analytical approach for symbol error ratio (SER) analysis of the SM algorithm in independent identically distributed (i.i.d.) Rayleigh channels. The analytical and simulation results closely match. The performance and the receiver complexity of the SM-OFDM technique are compared to those of the vertical Bell Labs layered space-time (V-BLAST-OFDM) and Alamouti-OFDM algorithms. V-BLAST uses minimum mean square error (MMSE) detection with ordered successive interference cancellation. The combined effect of spatial correlation, mutual antenna coupling, and Rician fading on both coded and uncoded systems are presented. It is shown that, for the same spectral efficiency, SM results in a reduction of around 90% in receiver complexity as compared to V-BLAST and nearly the same receiver complexity as Alamouti. In addition, we show that SM achieves better performance in all studied channel conditions, as compared with other techniques. It is also shown to efficiently work for any configuration of transmit and receive antennas, even for the case of fewer receive antennas than transmit antennas.     

Creating Effective Nanoreactors on Carbon Nanotubes with Mechanochemical Treatments for High‐Areal‐Capacity Sulfur Cathodes and Lithium Anodes

Li‐S batteries can potentially deliver high energy density and power, but polysulfide shuttle and lithium dendrite formations on Li metal anode have been the major hurdle. The polysulfide shuttle becomes severe particularly when the areal loading of the active material (sulfur) is increased to deliver the high energy density and the charge/discharge current density is raised to deliver high power. This study reports a novel mechanochemical method to create trenches on the surface of carbon nanotubes (CNTs) in free‐standing 3D porous CNT sponges. Unique spiral trenches are created by pressures during the chemical treatment process, providing polysulfide‐philic surfaces for cathode and lithiophilic surfaces for anode. The Li‐S cells made from manufacturing‐friendly sulfur‐sandwiched cathodes and lithium‐infused anodes using the mechanochemically treated electrodes exhibit a strikingly high areal capacity as high as 13.3 mAh cm^?2, which is only marginally reduced even with a tenfold increase in current density (16 mA cm^?2), demonstrating both high “cell‐level” energy density and power. The outstanding performance can be attributed to the significantly improved reaction kinetics and lowered overpotentials coming from the reduced interfacial resistance and charge transfer resistance at both cathodes and anodes. The trench–wall CNT sponge simultaneously tackles the most critical problems on both the cathodes and anodes of Li‐S batteries, and this method can be utilized in designing new electrode materials for energy storage and beyond.     

Skin-like Omnidirectional Stretchable Platform with Negative Poisson's Ratio for Wearable Strain–Pressure Simultaneous Sensor

Conventional elastomeric polymers used as substrates for wearable platforms have large positive Poisson's ratios (≈0.5) that cause a deformation mismatch with human skin that is multidirectionally elongated under bending of joints. This causes practical problems in elastomer-based wearable devices, such as delamination and detachment, leading to poorly reliable functionality. To overcome this issue, auxetic-structured mechanical reinforcement with glass fibers is applied to the elastomeric film, resulting in a negative Poisson's ratio (NPR), which is a skin-like stretchable substrate (SLSS). Several parameters for determining the materials and geometrical dimensions of the auxetic-structured reinforcing fillers are considered to maximize the NPR. Based on numerical simulation and digital image correlation analysis, the deformation tendencies and strain distribution of the SLSS are investigated and compared with those of the pristine elastomeric substrate. Owing to the strain-localization characteristics, an independent strain-pressure sensing system is fabricated using SLSS with a Ag-based elastomeric ink and a carbon nanotube-based force-sensitive resistor. Finally, it is demonstrated that the SLSS-based sensor platform can be applied as a wearable device to monitor the physical burden on the wrist in real time.     

A 400-mA current-mode buck converter with a self-trimming current sensing scheme

A current-programmed mode (CPM) controller is designed for improved DC–DC converter control. The key building block of the CPM controller is an accurate current-sensing circuit. This paper proposes a lossless current-sensing technique to measure the inductor current by measuring the current through the power transistor. A self-trimming circuit is used to compensate for any inaccuracies caused by voltage and temperature variations. The measurement results validate the operation of the fabricated chip.