System study on direct sequence spectrum of radio-frequency identification

This paper considers points of secure and anti-collision of the Radio-frequency identification (RFID) technology. Source symbols are represented by a special coding, termed Minimum Energy (ME) coding, which exploits redundant bits for saving power when transmitted via RF links with On-Off Keying (OOK). This ME coding is applied to Direct Sequence Spread Spectrum (DSSS) RFID tag in order to enhance security as well as to reduce collision. This synchronized DSSS RFID system is designed and simulation is conducted to verify the advantage of DSSS RFID and present the power efficiency enhance 4 dB, quantities are taken at Bit Error Rate (BER) of 10e-4. When the channel uses the ME coding combined with a DSSS code and OOK without FM0 encoding as is disclosed in the EPC-C1G2/ISO 18000-6 Type C standard. Finally, the maximum number of users in this Direct-Sequence Code Division Multiple Access (DS-CDMA) RFID system is calculated under the condition of successfully acquired.     

Check out the Rules: Towards Time-Efficient Rule Checking over RFID Tags

With the rapid proliferation of RFID technologies, RFID has been introduced to the applications like safety inspection and warehouse management. Conventionally a number of deployment rules are specified for these applications. This paper studies a practically important problem of rule checking over RFID tags, i.e., checking whether the specified rules are satisfied according to the RFID tags within the monitoring area. This rule checking function may need to be executed frequently over a large number of tags and therefore should be made efficient in terms of execution time. Aiming to achieve time efficiency, we respectively propose two protocols, CRCP and ECRCP. CRCP works based on collision detection, while ECRCP combines the collision detection and the logical features of the rules. Simulation results indicate that our protocols achieve much better performance than other solutions in terms of time efficiency.     

A Low-Cost RFID Authentication Protocol Against Desynchronization with a Random Tuple

Radio frequency identification (RFID) technology will become one of the most popular technologies to identify objects in the near future. However, the major barrier that the RFID system is facing presently is the security and privacy issue. Recently, a lightweight anti-desynchronization RFID authentication protocol has been proposed to provide security and prevent all possible malicious attacks. However, it is discovered that a type of desynchronization attacks can successfully break the proposed scheme. To overcome the vulnerability under the desynchronization attacks, we propose a low-cost RFID authentication protocol which integrates the operation of the XOR, build-in CRC-16 function, permutation, a random tuple and secret key backup technology to improve the security functionality without increasing any cost than the utralightweight protocols. The analysis shows that our proposal has a strong ability to prevent existing malicious attacks, especially the desynchronization attacks.     

A New Ultralightweight RFID Protocol for Low-Cost Tags: R^{2}AP

Several ultralightweight radio frequency identification (RFID) authentication protocols have been proposed in recent years. However, all of these protocols are reported later that they are vulnerable to various kinds of attacks (such as replay attack, de-synchronization attack, full disclosure attack, etc.) and/or have user privacy concerns. In this paper, we propose a new ultralightweight RFID protocol named reconstruction based RFID authentication protocol (R \(^{2}\) AP), which is based on the use of a new bitwise operation reconstruction. Operation reconstruction has three important properties: Hamming weight unpredictability, irreversibility and effectiveness. Some or all of these properties are absent in previous protocols and therefore has caused a lot of insecurity issues. The proposed R \(^{2}\) AP takes advantage of reconstruction to guarantee security of RFID system. Furthermore, we improve the Juels–Weis untraceability model so that the extended mathematic model can be used to analyze security functionality for ultralightweight RFID protocols. Our security analysis and performance evaluations demonstrate that (1) R \(^{2}\) AP can withstand all attacks mentioned in the paper and protect users’ privacy; (2) R \(^{2}\) AP is indeed an effective RFID protocol that can be implemented on low-cost tags.     

Simultaneous prediction of density and moisture content of wood by terahertz time domain spectroscopy

In this study, demonstration of simultaneous prediction of solid wood density and moisture content, both of which are critical in manufacturing operations, of 4 species (Aspen, Birch, Hemlock and Maple) was accomplished using terahertz time-domain spectroscopy (THz-TDS). THz measurements of wood at various moisture contents were taken for two orientations of the THz field (parallel and perpendicular) with respect to the visible grain. The real and imaginary parts of the dielectric function averaged over the frequency range of 0.1 to 0.2 THz had strong correlation with density and moisture content of the wood. We extend a model that has been applied previously to oven-dry wood to include the effects of moisture below the fiber saturation point by combining two effective medium models, which allows the dielectric function of water, air and oven-dry cell wall material to be modeled to give an effective dielectric function for the wood. A strong correlation between measured and predicted values for density and moisture content were observed.     

Low-Power Symmetrical Rectifier for Passive UHF RFID Transponder

Rectifier design is one of the challenging issues in passive radio-frequency identification (RFID) systems. Differential structures are good candidates as rectifiers to their high conversion efficiencies. In this paper, a novel structure is proposed to produce symmetrical power-supply utilizing differential circuit configuration simulated in 130nm CMOS technology. The proposed rectifier can provide 1.34 V DC power with 382% voltage conversion efficiency, thus demonstrated its higher performance over existing designs.     

Terahertz polarization beam splitter based on photonic crystal and multimode interference

We design a compact terahertz （THz） polarization beam splitter. Both plane wave expansion method and fi- nite-difference time-domain method are used to calculate and analyze the characteristics of the proposed device. The designed polarization beam splitter can split TE-polarized and TM-polarized THz waves into different propagation di- rections. The simulation results show that the extinction ratios are larger than 18.36 dB for TE polarization and 13.35 dB for TM polarization in the frequency range from 1.86 THz to 1.91 THz, respectively. The designed polarization beam splitter has the advantages of small size and compact structure with a total size of 4.825 mm×0.400 mm.     

Optical Properties of 3D Printable Plastics in the THz Regime and their Application for 3D Printed THz Optics

We characterize the terahertz (THz) properties of several materials which can be used for fused material deposition 3D printing. We identify Polystyrene as a material which shows a promising compromise between printability and THz transparency. Furthermore, printed THz lenses are presented and characterized.     

Sample Thickness Measurement with THz-TDS: Resolution and Implications

The accuracy of any measurement with terahertz time-domain spectroscopy (THz-TDS) depends strongly on knowing and supplying the precise sample thickness when processing the raw terahertz data. Sample thickness usually is estimated using other (non-THz) metrology and invariably involves some degree of uncertainty. It turns out that the terahertz data itself typically also contains information regarding sample thickness. However, there is limited systematic work addressing the following questions: What is the best method for extracting sample thickness from THz-TDS data? And, what is the thickness resolution obtainable with THz-TDS? In this study we demonstrate how these questions can be answered in general by answering them for a specific example: undoped silicon wafers. We determine the accuracy with which the exact thickness of nominally 500 μm silicon wafers can be measured using transmission mode THz-TDS. We analyze and compare the resolution of 5 different approaches for determining sample thickness using THz-TDS data, including two new methods and three methods proposed in the literature. The quantitative results and analyses of methods we present will be useful in developing far-infrared optical metrology. Conversely the quantitative results presented can be used to relate uncertainty in sample thickness to uncertainty in the measured terahertz data both in the time domain and frequency domain (phase and amplitude). Finally, a precise understanding of the relationship between sample thickness and THz-TDS data can be used to formulate superior THz-TDS data work-up methodologies.     

Characterization of in-situ terahertz detection by optical interaction in a periodically poled stoichiometric lithium tantalate nonlinear crystal

Terahertz waves are generated using a femtosecond laser pulse in a periodically poled stoichiometric lithium tantalate crystal and simultaneously detected via a non-collinear optical parametric interaction inside the same crystal. Real time up-conversion signal between the generated THz and an optic probe pulses is measured depending on the beam overlapped conditions using a general silicon-photodiode for the THz detection. The non-collinear geometry is to facilitate manipulated property of the position-dependent bandwidth at narrow and broad bandwidths of 45 GHz and 3.3 THz, respectively at the one crystal. Furthermore, an aperture effect at the detection part is characterized as the function of size and position owing to the spatial distribution of the frequency conversion signal and it is applied in optimization of the in-situ detection scheme.     

Terahertz Spectra of L-Ascorbic Acid and Thiamine Hydrochloride Studied by Terahertz Spectroscopy and Density Functional Theory

We have investigated the terahertz spectra of L-ascorbic acid and thiamine hydrochloride measured by terahertz time-domain spectroscopy (THz-TDS) and Fourier transform infrared spectroscopy (FTIR). The measured absorption spectra were demonstrated to be in good agreement with the results simulated by Density Functional Theory (DFT) using hybrid functional B3LYP with basis set of 6-31G (d), except with slight frequency shift and few peaks missing. We presented the comparison of measured spectra by the FTIR spectroscopy employing low temperature silicon bolometer as detector and the TDS system. The measured spectra of the L-ascorbic acid showed shoulder bands at 0.25, 1.1, 1.5, 1.82, 2.03, 2.30, 2.44, 2.67, 2.97, 3.12, and 3.40 THz, respectively. The spectra of the thiamine hydrochloride show shoulder bands at 0.48, 1.11, 1.57, 1.75, 1.92, 2.08, 2.31, 2.53, 2.69, 2.85, 3.12, 3.22, and 3.31 THz. Most absorption peaks of the two samples agree with the results simulated by Density Function Theory (DFT) method of Gaussian 09 software. In our work, more spectral peaks based on experimental and theoretical results were found in comparison to that of other groups, since we employed higher sensitive FTIR measurement system and considered the effect of number of molecule unit in simulation. The study suggests that the effect of intermolecular vibration is stronger than intramolecular interaction on the absorption bands in THz region.     

The Application of RFID Monitoring Technology to Patrol Management System in Petrochemical Industry

A lot of manufacturers tend to enhance the management efficacy and reduce the management costs by investing large resources in the research and development of radio frequency identification (RFID). For petrochemical industry, an effective, reliable, and secure patrol management system is primary. Nevertheless, traditional patrol management focuses on labor patrol that the field staff master in the corrosion, leakage, and pipe aging of production equipment. Although equipment inspection and patrol items are scheduled every day, some problems still need to be overcome. After completing traditional patrol tasks, extra time and manpower are required for organizing the patrol records and filling them into electronic document. In the process, it is likely to key in wrong data because of the numerous patrol items. Apparently, without systematic management, supervisors and shift leaders can hardly find out data errors and analyze the abundant data for complete risk evaluation and process security improvement. An RFID-based patrol management system suitable for petrochemical industry is proposed in this study. The system corresponds to the field environment requirements and regulations for petrochemical plants, integrates operation procedure and information procedure, and evaluates and includes various dimensions and variables through interviews and technological analyses to enhance the process security. Active processing equipment monitoring could enhance the preventive maintenance efficiency and promote the production capacity and industrial competitiveness.     

Improved Hydrogen Capping Effect in n-Type Crystalline Silicon Solar Cells by SiN(Si-Rich)/SiN(N-Rich) Stacked Passivation

The effect of hydrogen capping of SiN(Si-rich)/SiN(N-rich) stacks for n-type c-Si solar cells was investigated. Use of a passivation layer consisting of Si-rich SiN with a refractive index (n) of 2.7 and N-rich SiN with a refractive index of 2.1 improved the thermal stability. A single SiN passivation layer with a refractive index of 2.05 resulted in an initial lifetime of 200 μs whereas the layer with a refractive index of 2.7 resulted in a high initial lifetime of 2 ms, but the layer degraded rapidly after firing. A stacked passivation layer with refractive indices of 2.1 and 2.7 had a stable lifetime of 1.5 ms with an implied open-circuit voltage (iV _oc) of 720 mV after firing. The thermally stable passivation mechanism with changing amounts of Si–N and Si–H bonding was analyzed by Fourier-transform infrared (FTIR) spectroscopy. Incorporation of the SiN _x stack layer (2.7 + 2.1) into the passivated rear of n-type Cz silicon screen-printed solar cells resulted in energy conversion efficiency of 19.69%. Improved internal quantum efficiency in the long-wavelength range above 900 nm, with V _oc of 630 mV, is mainly because of superior passivation of the rear surface compared with conventional solar cells.     

Ant Optimized Link Quality for Ad Hoc on Demand Distance Vector

The wireless interfaces in Mobile Ad-Hoc Networks (MANETs) have limited transmission range and traffic is relayed through intermediate nodes to ensure intra node communication. Routing plays an important role in network reliability and performance. MANET’s characteristics like mobility and resource constraints adversely affect routing performance. A new MANET routing method based on Ad hoc On- demand Distance Vector (AODV) and Ant Colony Optimization is proposed in this paper. Ad hoc networks can emulate achievement of complex solutions with limited intelligence and individual capacity as seen in ant communities. A new link quality metric enhances AODV routing algorithm to enable it to handle link quality to evaluate routes between nodes.     

Simulation of Terahertz Generation from Lateral Diffusion Currents in Semiconductor Devices

In this paper we model the carrier dynamics and resulting THz emission from lateral diffusion currents within a semiconductor device which has been partially masked by a metallic mask. We present a numerical 1D model and a 1D Monte Carlo simulation which both demonstrate that regardless of the excitation laser spot shape we do not expect to see measurable THz emission in the direction of the optical pump propagation from lateral diffusion currents. Experimentally such devices do produce strong THz emission. We analytically investigate the role of the metal mask and we found that it suppresses the emission of dipoles that are in a region that is less than a wavelength away from the interface. The results from the numerical model are also included in a finite element analysis model of the geometry which predicts THz emission if and only if the metal mask is present.     

Channel Estimation in Long Term Evolution Uplink Using Minimum Mean Square Error-Support Vector Regression

In this paper, minimum mean square error-support vector regression (MMSE-SVR) is proposed, which is shown to be adequate for the estimation of the long term evolution (LTE) uplink channel with nonlinear features. MMSE-SVR was applied to estimate real channel environments such as the vehicular A channels defined by the International Telecommunication Union (ITU). The simulation results show that the proposed method has a better performance than the least squares support vector machine (LS-SVM) and the standard MMSE with linear and spline interpolation.     

Robust MMSE Design With Asynchronous Interference Mitigation in Cooperative Base Station Systems

This paper investigates minimum mean square error (MMSE) with asynchronous interference mitigation in cooperative base station systems. We consider the asynchronous transmission because of the different propagation times between the base station (BS) and mobile stations (BSs). Meanwhile, the channel quantization errors duo to channel quantization is taken into account in our analysis. The proposed scheme is robust to asynchronous interference and channel quantization errors in BSs cooperation systems. Simulations results show that proposed MMSE scheme achieve an improved performance compared with the conventional MMSE in BSs cooperative systems.     

Specific features of the hydride vapor-phase epitaxy of nitride materials on a silicon substrate

Specific features of the growth of the GaN/AlN/Si heterocomposite in which layers of Group-III element nitrides are grown on a silicon substrate by hydride vapor-phase epitaxy are studied. The effect of the temperature at which the AlN buffer layer is grown on diffusion processes at the heterointerfaces and on the quality of the epitaxial layers being grown is considered. It is shown that, with the epitaxial technique used, the buffer layer should be grown at high temperatures (1080°C) because the thickness of the component-mixing region is minimized in this case and abrupt interfaces are formed in the GaN/AlN/Si heterocomposite. The double-stage growth of gallium nitride on the high-temperature AlN buffer layer with a thickness of 300–400 nm makes it possible to obtain GaN layers with thicknesses of up to 0.3 μm without crack formation.     

Charge transport in Si-SiO2 and Si-TiO2 nanocomposite structures

The experimental data on dispersed Si-SiO₂ and Si-TiO₂ nanocomposite structures different in terms of physical, chemical, and insulator properties of oxide components are reported. The parameters of the nanocomposite structures are studied by FTIR spectroscopy and impedance spectroscopy. It is shown that, in such structures, the mechanisms of charge-carrier transport are defined by the properties of Si nanocrystallites and the corresponding oxide as well as by interaction processes at interfaces between grains.     

Mixing properties of mim diodes in the infrared

Point contact MIM diodes of different materials have been tested as harmonic mixers at 29 THz and 88 THz. From the analysis of the I-V static characteristic quantitative informations have been obtained about the effectiveness of the diodes as high order mixers.