# September 2011, Volume 20, Number 3

**M. Simunek, P. Pechac, F. P. Fontan**
[references] [full-text]

Excess Loss Model for Low Elevation Links in Urban Areas for UAVs

In this paper we analyze the link between an UAV and a ground control station in an urban area. This link shows a unique geometry which is somewhere in between the purely terrestrial (e.g., a macro-cell channel) and the land mobile satellite case (LMS). We describe a measurement campaign which reproduces the UAV link conditions and shows how the excess loss is mainly dependent on the elevation angle and fairly independent of the distance. Finally, we propose a simple physical model for predicting the excess loss based on a combination of diffracted and reflected components. Results from this model are in good agreement with the measurements.

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- CERASOLI, C. An analysis of unmanned airborne vehicle relay coverage in urban environments. In Military Communications Conference (MILCOM). Orlando (USA), 2007, p. 1 - 7.
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Keywords: UAV, channel modeling, low elevation, urban area, path loss, diffraction

**J. Lacik**
[references] [full-text]

Acceleration of Marching on in Time Method for TD-EFIE by Equivalent Dipole Moment Method and its Analysis

The paper is focused on the application of the equivalent dipole moment (EDM) method to accelerate the marching on in time (MOT) method for the time domain electric field integral equation (TD-EFIE). The implicit MOT scheme with the EDM method for the TD-EFIE is derived and analyzed. It is shown that the derived scheme is faster than the conventional one, even if it is not used for modeling electrically large structures. Since the conventional implicit MOT scheme for the TD-EFIE is sensitive to small changes of its coefficients, the full-value using of the MOT scheme with the EDM approximation requires an appropriate technique (e.g. a preconditioning) to obtain a well-conditioned scheme.

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- YUAN, J., GU, CH., HAN, G. A hybrid equivalent dipole moment and adaptive modified characteristic basis function method for electromagnetic scattering by multilayered dielectric bodies. International Journal of RF and Microwave Computer-Aided Engineering, 2009, vol. 19, no. 6, p. 685-691.
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- SHI, Y., XIA, M. Y., CHEN, R. S., MICHIELSSEN, E., LU, M. Stable electric field TDIE solvers via quasi-exact evaluation of MOT matrix elements. IEEE Transactions on Antennas and Propagation, 2011, vol. 59, no. 2, p. 574-585.
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Keywords: Marching on in time method, time domain electric field integral equation, equivalent dipole moment method.

**F. Dvorak, J. Diblik**
[references] [full-text]

Study of the Temperature Turbulences Effect upon Optical Beam in Atmospheric Optical Communication

The paper deals with the study of the effect of temperature turbulences upon the optical beam. The polarization parameters of optical radiation sources and different optical beam states of polarization have been investigated. The obtained polarization parameters are projected on the Poincare sphere by means of Stokes vectors. The optical power distribution curves of optical beams are processed into diagrams. The horizontal and vertical components of linearly and circularly polarized optical beams have been studied. The turbulence flux has vertical direction and the optical beam is propagating through an atmosphere environment with three different states of turbulence. The evaluation of the obtained data was done by means of variance and correlation functions computing. Different rates of effect of temperature turbulences upon horizontal and vertical components were found. To reduce the rate of effect the advantage of an optical beam with circular polarization has been proposed.

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Keywords: Temperature turbulences, optical beam, state of polarization, Poincare sphere, variance, cross correlation function.

**A. F. Yagli**
[references] [full-text]

MRFD Method for Scattering From Three Dimensional Dielectric Bodies

A three-dimensional multiresolution frequency domain (MRFD) method is established to compute bistatic radar cross sections of arbitrarily shaped dielectric objects. The proposed formulation is successfully verified by computing the bistatic radar cross sections of a dielectric sphere and a dielectric cube. Comparing the results to those obtained from the finite difference frequency domain (FDFD) method simulations and analytic calculations, we demonstrated the computational time and memory advantages of MRFD method.

- KUZU, L., DEMIR, V., ELSHERBENI, A. Z., ARVAS, E. Electromagnetic scattering from arbitrarily shaped chiral objects using the finite difference frequency domain method. Progress in Electromagnetics Research, 2007, vol. 67, p. 1 - 24.
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- ALKAN, E., DEMIR, V., ELSHERBENI, A. Z., ARVAS, E. Dual-grid finite-difference frequency-domain method for modeling chiral medium. IEEE Transactions on Antennas and Propagation, 2010, vol. 58, no. 3, p. 817 - 823.
- YAGLI, A. F., GOKTEN, M., IMECI, S. T., KUZU, L. Scattering from gyrotropic bodies using FDFD method. International Journal of RF and Microwave Computer-Aided Engineering, 2011, vol. 21, no. 1, p. 77 - 84.
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- GOKTEN, M., ELSHERBENI, A. Z., ARVAS, E. Electromagnetic scattering analysis using the two-dimensional MRFD formulation. Progress in Electromagnetics Research, 2008, vol. 79, p. 387 – 399.
- GOKTEN, M., ELSHERBENI, A. Z., YAGLI, A. F. Efficient analysis of two-dimensional RCS scattering analysis using the MRFD technique. In ACES Conf. Williamsburg (VA), 2011.
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Keywords: FDFD method, MRFD method, electromagnetics, scattering

**F. Boukerroum, F. Djahli**
[references] [full-text]

Simple and Accurate Method for Microwave Noise Parameters Calculation

This paper proposes a new method for microwave two-port noise parameters values extraction. The method is based on a set of simple and accurate formulas witch allows the noise characterization without any optimization procedure. The measurements were performed using a system based on a short cascaded with a long transmission line and a passive two-port designed to exhibit versus frequency a behavior close to a transistor. The results presented for a measurement example show good agreement with those obtained using an optimization procedure. The new extraction method based on the frequency variation noise measurement principle and used with a simple hardware can be a practical tool for workers in the field.

- MEYS, R. P., BOUKERROUM, F. Broadband noise system allows measurements according to both standard methods. IEEE Transactions on Instrumentation and Measurements, 2011, vol. 60, no. 4, p. 1316 – 1327.
- MEYS, R. P., BOUKERROUM, F. Calibrating broadband highly mismatched noise sources. IEEE Transactions on Instrumentation and Measurements, 2011, vol. 60, no. 4, p. 1328 – 1333.
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Keywords: Noise measurement, noise parameters, noise wave model.

**W. Jaikla ,P. Prommee**
[references] [full-text]

Electronically Tunable Current-mode Multiphase Sinusoidal Oscillator Employing CCCDTA-based Allpass Filters with Only Grounded Passive Elements

This study describes the design of a multiphase sinusoidal oscillator (MSO) using CCCDTA-based allpass filters with grounded capacitors. The oscillation condition and oscillation frequency can be electronically/orthogonally controlled. The proposed MSO provides 2n (n>2) phase signals that are equally spaced in phase and of equal amplitude. The circuit requires one CCCDTA, one electronic resistor and one grounded capacitor per phase and no additional current amplifier and floating elements. High output impedances of the configuration enable the circuit to be cascaded to the current-mode circuit without additional current buffers. The effects of the non-idealities of the CCCDTA-allpass sections were also studied. The results of PSPICE simulations using CMOS CCCDTA are presented, demonstrating their consistency with theoretical assumptions.

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- KLAHAN, K., TANGSRIRAT, W., SURAKAMPONTORN, W. Realization of multiphase sinusoidal oscillator using CDBAs. IEEE Asia-Pacific Conf. Circ. Sys., 2004, p. 725–728.
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Keywords: Multiphase Sinusoidal Oscillator, CCCDTA, current-mode

**P. Prommee, N. Prapakorn, M.N.S. Swamy**
[references] [full-text]

Log-Domain Current-mode Quadrature Sinusoidal Oscillator

A log-domain current-mode quadrature sinusoidal oscillator based on lossless integrators is presented. The circuit is a direct realization of a first-order differential equation for obtaining the lossy and lossless integrators. Each of the log-domain lossless integrators is realized by using only NPN transistors and a grounded capacitor for achieving low-power and fast response. The proposed oscillator uses two-lossless integrator loop which can be electronically tuned through bias currents. A validated BJT model which is used in SPICE simulation operated from a single power supply as low as 2.5V. The oscillation frequency is controlled over four decades of frequency. The total harmonic distortions for two-phases QSO (12MHz) is obtained around 0.93% which enables fully integrated in telecommunication systems. The proposed circuit is also suitable for high-frequency applications. Nonideality studies are included and PSpice simulation results confirm the theoretical results.

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Keywords: Log-domain filtering, high-frequency, low-voltage, electronically-controlled, quadrature oscillator

**J. W. Horng, Z. R.Wang, T. Y. Yang**
[references] [full-text]

Single ICCII Sinusoidal Oscillators Employing Grounded Capacitors

Two inverting second-generation current conveyors (ICCII) based sinusoidal oscillators are presented. The first sinusoidal oscillator is composed of one ICCII, two grounded capacitors and two resistors. The oscillation condition and oscillation frequency can be orthogonally controllable. The second sinusoidal oscillator is composed of one ICCII, two grounded capacitors and three resistors. The oscillation condition and oscillation frequency can be independently controllable through different resistors.

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Keywords: Sinusoidal oscillator, current conveyor, active circuit

**B. Metin**
[references] [full-text]

Supplementary Inductance Simulator Topologies Employing Single DXCCII

In this study, six grounded inductance simulator circuits are presented including additional useful features in comparison to previous dual-X current conveyor (DXCCII) based implementations. To demonstrate the performance and usefulness of the presented circuits, one of them is used to construct a fifth order Butterworth high-pass filter and a current-mode multifunction filter as application examples. Simulation results are given to confirm the theoretical analysis. The derived DXCCII and its applications are simulated using CMOS 0.35 μm technology.

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Keywords: DXCCII, inductance simulator, dual-X current conveyor

**J. Valsa, P. Dvorak, M. Friedl**
[references] [full-text]

Network Model of the CPE

Analysis of fractal systems (i.e. systems described by fractional differential equations) necessitates to create an electrical analog model of a crucial subsystem called Constant Phase Element (CPE). The paper describes a possible realization of such a model, that is quite simple and in spite of its simplicity makes it possible to simulate the properties of ideal CPEs. The paper also deals with the effect of component tolerances on the resultant responses of the model and describes several typical model applications.

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Keywords: Fractional differential equations, Constant Phase Element, Warburg impedance

**F. Kaçar, H. Kuntman**
[references] [full-text]

CFOA-Based Lossless and Lossy Inductance Simulators

Inductance simulator is a useful component in the circuit synthesis theory especially for analog signal processing applications such as filter, chaotic oscillator design, analog phase shifters and cancellation of parasitic element. In this study, new four inductance simulator topologies employing a single current feedback operational amplifier are presented. The presented topologies require few passive components. The first topology is intended for negative inductance simulation, the second topology is for lossy series inductance, the third one is for lossy parallel inductance and the fourth topology is for negative parallel (-R) (-L) (-C) simulation. The performance of the proposed CFOA based inductance simulators is demonstrated on both a second-order low-pass filter and inductance cancellation circuit. PSPICE simulations are given to verify the theoretical analysis.

- AWAD, A., SOLIMAN, A. M. Inverting second generation current conveyors: the missing building blocks, CMOS realizations and applications. International Journal of Electronics, 1999, vol. 86, no. 4, p. 413 – 432.
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- YUCE, E., MINAEI, S., CICEKOGLU, O. Novel floating inductance and FDNR simulators employing CCIIs. Journal of Circuits, Systems and Computers, 2006, vol. 15, p. 78 – 81.
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- KACAR, F. New lossless inductance simulators realization using a minimum active and passive components. Microelectronics Journal, 2010, vol. 41, no. 2 – 3, p. 109 – 113.
- YUCE, E., MINAEI, S., CICEKOGLU, O. Limitations of the simulated inductors based on a single current conveyor. IEEE Transactions on Circuits and Systems-I, 2006, vol. 53, no. 12, p. 2860 – 2867.
- YUCE, E. On the implementation of the floating simulators employing a single active device. International Journal of Electronics and Communications (AEU), 2007, vol. 61, no. 7, p. 453–458.
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- YUCE, E. Grounded inductor simulators with improved low frequency performances. IEEE Transactions on Instrumentation and Measurement, 2008, vol. 57, no. 5, p. 1079 – 1084.
- YUCE, E. Novel lossless and lossy grounded inductor simulators consisting of a canonical number of components. Analog Integrated Circuits and Signal Processing, 2009, vol. 59, no. 1, p. 77 – 82.
- YUCE, E., MINAEI, S. A modified CFOA and its applications to simulated inductors, capacitance multipliers, and analog filters. IEEE Transactions on Circuits and Systems I, 2008, vol. 55, no.1, p. 254 – 263.
- MINAEI, S., CICEKOGLU, O., KUNTMAN, H., TURKOZ, S. Electronically tunable, active only floating inductance simulation. International Journal of Electronics, 2002, vol. 89, no. 23, p. 905 – 912.
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Keywords: CFOA, inductance simulators, filters, analog integrated circuit.

**A. Yeşil, F. Kacar, H. Kuntman**
[references] [full-text]

New Simple CMOS Realization of Voltage Differencing Transconductance Amplifier and Its RF Filter Application

The voltage differencing transconductance amplifier (VDTA) is a recently introduced active element for analog signal processing. However, the realization of VDTA is not given by any author yet. In this work, a new and simple CMOS realization of VDTA is presented. The proposed block has two voltage inputs and two kinds of current output, so it is functional for voltage- and transconductance-mode operation. Furthermore, VDTA exhibits two different values of transconductance so that there is no need to external resistors for VDTA based applications which seems to be a good advantage for analog circuit designer. A CMOS implementation of VDTA and a voltage-mode VDTA based filter are proposed and simulated. An application example of fourth order flat-band band-pass amplifier is given and the performance of the circuit is demonstrated by comparing the theory and simulation.

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- UYGUR, A., KUNTMAN, H. Seventh-order elliptic video filter with 0.1 dB pass band ripple employing CMOS CDTAs. AEU: International Journal of Electronics and Communications, 2007, vol. 61, no. 5, p. 320 – 328.
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Keywords: Voltage differencing transconductance amplifier, voltage mode filter, CMOS integrated circuit.

**A. Lahiri**
[references] [full-text]

New CMOS-based Resistor-less Current-mode First-order All-pass Flter Using Only Ten Transistors and One External Capacitor

This paper proposes a new, compact CMOS realization of current-mode (CM) first-order all-pass filter (APF) using no external resistors. The circuit is created using only ten transistors and one external capacitor. The circuit uses lower number of transistors as compared to previously reported CM APFs using active building block (ABB) based approach. A comparison with previously reported CM APFs in terms of number of transistors and current consumption has been provided. As a design example, a 512 kHz pole-frequency (at typical process and 27ºC) CM APF is designed in 40nm CMOS technology and validated through SPICE simulations.

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Keywords: analog circuits, current-mode (CM), first-order all-pass filter (APF), resistor-less

**Y. Li**
[references] [full-text]

Current-Mode Sixth-Order Elliptic Band-Pass Filter Using MCDTAs

In this paper, a modified CDTA (MCDTA) is presented and the current-mode second-order band-pass, high-pass notch, and low-pass notch circuits using MCDTAs are given. Moreover, a current-mode sixth-order elliptic band-pass filter is realized by means of cascade method. Having used six MCDTAs, six grounded capacitors and two resistors, the circuit is easy to be integrated, of which the parameters can be electronically adjusted by tuning bias currents. It is noted that the results of circuit simulations are in agreement with theory.

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Keywords: Sixth-order elliptic band-pass filter, current mode, electronic adjusting, MCDTA.

**J. Satansup, W. Tangsrirat**
[references] [full-text]

Single-Input Five-Output Electronically Tunable Current-Mode Biquad Consisting of Only ZC-CFTAs and Grounded Capacitors

This paper presents an electronically tunable current-mode biquadratic filter constructing with four Z-copy current follower transconductance amplifiers (ZC-CFTAs) and only two grounded capacitors. The presented filter can realize all the five standard biquadratic functions simultaneously without requiring any component matching conditions and connecting any relevant output currents. The circuit has one low-impedance input and five high-impedance outputs, resulting in easy cascadability in current-mode. Also, the developed circuit exhibits the advantage of non-interactive electronic control of the natural angular frequency and the quality factor Q along with low incremental active and passive sensitivities. Computer simulation results using PSPICE program are given to confirm the validity of the theoretical prediction and to point out the attractive performance of the circuit.

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- TANGSRIRAT, W. Single-input three-output electronically tunable universal current-mode filter using current follower transconductance amplifiers. Int. J. Electron. Commun. (AEU), doi: 10.1016/j.aeue.2011.01.002.
- BIOLEK, D., BIOLKOVA, V., BAJER, J. Single-input multioutput resistorless current-mode biquad. In Proc. ECCTD’99. Antalya (Turkey), 2009, p. 225-228.
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Keywords: Z-Copy Current Follower Transconductance Amplifier (ZC-CITA), biquad filter, current-mode circuit, electronically tunable.

**R. Arslanalp, A. T. Tola, E. Yuce**
[references] [full-text]

Novel Resistorless First-Order Current-Mode Universal Filter Employing a Grounded Capacitor

In this paper, a new bipolar junction transistor (BJT) based configuration for providing first-order resistorless current-mode (CM) all-pass, low-pass and high-pass filter responses from the same configuration is suggested. The proposed circuit called as a first-order universal filter possesses some important advantages such as consisting of a few BJTs and a grounded capacitor, consuming very low power and having electronic tunability property of its pole frequency. Additionally, types of filter response can be obtained only by changing the values of current sources. The suggested circuit does not suffer from disadvantages of use of the resistors in IC process. The presented first-order universal filter topology does not need any passive element matching constraints. Moreover, as an application example, a second-order band-pass filter is obtained by cascading two proposed filter structures which are operating as low-pass filter and high-pass one. Simulations by means of PSpice program are accomplished to demonstrate the performance and effectiveness of the developed first-order universal filter.

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Keywords: Current-mode, Universal filter, Resistorless, BJT

**J. Dolezal, J. Stastny, P. Sovka**
[references] [full-text]

Exploiting Temporal Context in High-Resolution Movement-Related EEG Classification

The contribution presents an application of a movement-related EEG temporal development classification which improves the classification score of voluntary movements controlled by closely localized regions of the brain. A dynamic Hidden Markov Model-based (HMM) classifier specifically designed to capture EEG temporal behavior was used. Surprisingly, HMM classifiers are rarely used for BCI design despite of their advantages. Because of this we also experimented with Learning Vector Quantization, Perceptron, and Support Vector Machine classifiers using a feature space which captures the temporal dynamics of the data. The results presented in this work show that HMM achieves the best performance due to an a priori information on physiological behavior of EEG inserted to the HMM classifier. Feature extraction process and problems with classification were analyzed as well. Classification scores of 66.7% – 94.7% were achieved in our experiments.

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Keywords: Brain-Computer Interface, EEG classification, electroencephalography, neural network applications, Hidden Markov Models.

**P. Varahram, B. M. Ali**
[references] [full-text]

A Low Complexity Partial Transmit Sequence for Peak to Average Power Ratio Reduction in OFDM Systems

Partial transmit sequence (PTS) is one of the most important techniques for reducing the peak to average power ratio (PAPR) in OFDM systems. This paper presents a low complexity PTS scheme by applying a new phase sequence. Unlike the conventional PTS which needs several inverse fast Fourier transform (IFFT) operations, the proposed technique requires half IFFT operations only at the expense of slight PAPR degradation. Simulation and results are examined with QPSK modulation and OFDM signal and power amplifier with memory effects.

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Keywords: CCDF, digital predistortion, Orthogonal frequency division multiplexing, partial transmit sequence, peak to average power ratio

**A. Ozen**
[references] [full-text]

A Novel QAM Technique for High Order QAM Signaling

The paper proposes a novel spread quadrature amplitude modulation (S-QAM) technique with high SNR improvement for high-order QAM channels. Simulated and experimental bit error rate (BER) performance analyses of the proposed technique in blind and non-blind equalizers are obtained by using single carrier (SC) WiMAX (IEEE 802.16-2004) radio. Instead of using any one particular type of channel profile, this study concentrates on true frequency selective Rayleigh fading channels in the real-time WiMAX radio environment around 3.5 GHz. The Constant Modulus Algorithm (CMA) blind equalizer has been compared with the popular non-blind equalizers, Recursive Least Squares (RLS) and Least Mean Squares (LMS) algorithm, as benchmarks. It has been proven in experimental and simulated channels that CMA blind equalizer, using the proposed technique, can be considered as a low complexity, spectrum efficient and high performance time domain equalizations to be embedded in a transceiver for the next generation communications. Furthermore the proposed technique has also reduced approximately till 5 dB and 7.5 dB performance differences between non-blind and blind equalizers for 16-QAM and 64-QAM, respectively. The simulation results have demonstrated that the simulated and experimental studies of the proposed technique are compatible with each other and extremely satisfying.

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Keywords: Experimental BER, adaptive blind training, WiMAX (IEEE 802.16-2004), constant modulus algorithm, S-QAM.

**B. Hrusovsky, J. Mochnac, S. Marchevsky**
[references] [full-text]

Error Concealment Method Based on Motion Vector Prediction Using Particle Filters

Video transmitted over unreliable environment, such as wireless channel or in generally any network with unreliable transport protocol, is facing the losses of video packets due to network congestion and different kind of noises. The problem is becoming more important using highly effective video codecs. Visual quality degradation could propagate into subsequent frames due to redundancy elimination in order to obtain high compression ratio. Since the video stream transmission in real time is limited by transmission channel delay, it is not possible to retransmit all faulty or lost packets. It is therefore inevitable to conceal these defects. To reduce the undesirable effects of information losses, the lost data is usually estimated from the received data, which is generally known as error concealment problem. This paper discusses packet loss modeling in order to simulate losses during video transmission, packet losses analysis and their impacts on the motion vectors losses.

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Keywords: Packet, loss, error concealment, particle filter

**H. Yuan, Z. Bao, A. Hu**
[references] [full-text]

Power Ramped-up Preamble RF Fingerprints of Wireless Transmitters

In this paper, we propose a novel kind of RF fingerprints (RFF) with better discriminability than typical RFF for identifying preamble-based wireless transmitters. First, the equivalent model of RFF identification system is built. Then, the typical RFF are analyzed with the built model and the novel RFF, which is transformed from preamble signal when its power is ramped up, is presented. Finally, the discriminability of the proposed RFF and typical RFF is experimentally evaluated with Wi-Fi 802.11b devices. The proposed RFF can be integrated into fusion identification of preamble-based wireless devices with multiple RFF.

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Keywords: Non-cryptographic authentication, hardware security, device identification, RF fingerprints, power ramped-up, fusion identification, RF fingerprinting, transmitter identification

**A. Aggelis, E. T. Sarris**
[references] [full-text]

Location Privacy on DVB-RCS using a “Spatial-Timing” Approach

DVB-RCS synchronization scheme on the Return Channel requires the RCSTs to be programmed with their location coordinates with an accuracy of no more than a few kilometers. RCSTs use this location information in their ranging calculation to the servicing satellite. For certain users this location information disclosure to the network operator can be seen as a serious security event. Recent work of the authors overcame this requirement by cloaking the location of an RCST in such a way (based on "spatial/geometric" symmetries of the network) that the respective ranging calculations are not affected. In this work we argue that timing tolerances in the Return Channel synchronization scheme, accepted by the DVB-RCS standard, can be used in combination to the "spatial" method, further enhancing the location privacy of an RCST. Theoretical findings of the proposed "spatial-timing" approach were used to develop a practical method that can be used by workers in the field. Finally this practical method was successfully tested on a real DVB-RCS system.

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Keywords: DVB-RCS security, location privacy, satellite communications, data cloaking, spatial accuracy, timing tolerances