In this article, we provide a novel, expanded, and adapted pruning approach for the Simplified Volterra Series (SVS) model that makes it applicable to a wider range of Power Amplifiers (PAs). The proposed Modified SVS (MSVS) model is then applied in a Digital Predistortion (DPD) architecture to linearize a 25 W Gallium Nitride (GaN) RF PA. A comprehensive and detailed experimental hardware setup is designed for the in-depth testing and validation of the proposed model based DPD architecture, covering PA characterization, model coefficients extraction, and linearization. Our proposed MSVS based DPD significantly reduces the computational cost by at least 60% compared to widely referenced models in the literature while maintaining an optimal balance between accuracy and complexity. Experimental results performed using Long Term Evolution (LTE) signals show a modeling accuracy of -37 dB in terms of Normalized Mean Square Error (NMSE) and a 14 dB reduction in out-of-band distortion in terms of Adjacent Channel Power Ratio (ACPR), compared to the no DPD configuration.

This paper addresses the effects of Middleton Class-A noise on a binary OFDM-based communication system and proposes a full theoretical study of its statistics. The simulation approach for the Class-A noise, which confirms a previous research work, is based on symbol-wise transmission. Analytical formulations for the statistics of the noise power at the output of the OFDM demodulator and of the error probability are established, and validated by the simulation results. It is concluded that the variance of the impulse noise power, as well as the error floor in the Bit Error Rate (BER) curves are closely related to not only the impulsive index A, but also to the FFT block size N. The error floor decreases when the product of the impulsive index and the FFT block size, AN, increases. The asymptotic value of the error floor is given by the BER for an additive white Gaussian noise channel with noise variance equal to the average variance of the Class-A impulse noise.

Summary In this article, we propose a new criterion for a switching algorithm to be used in MIMO‐OFDM systems. The switching algorithm, which selects between spatial multiplexing and MIMO diversity using the Demmel condition number as selection metrics, is first analyzed. Then, we show the limitation of this criterion, when increasing the receive antenna number. As a solution, we propose multiantenna processing and SNR switching criterion as a novel selection metric. The channel between the transmitter and the receiver is assumed a Rayleigh‐fading channel. Simulations results show that the proposed switching algorithm improves the performances in terms of bit error rate (BER) for symmetric and asymmetric MIMO systems. The gain is about 3 dB at BER = 10 −4 in (4×4) architecture and 2 dB at BER = 10 −4 in (3×2) architecture.

We propose a novel simulation approach of the Middleton Class-A model for impulsive noise generation considering symbol-wise transmission in a real Power Line Communication environment. Then, we validate the proposed approach for both single carrier binary FSK based-and multi-carrier OFDM-based communication systems. Established analytical formulations and obtained simulation results for the impulsive noise variance distribution and the communication system error probability show that in a binary FSK system, the second order of the noise variance per symbol, as well as the error floor, are closely related to the impulsive index A. The error floor decreases when A becomes large, and its asymptotic value is equal to the Bit Error Rate (BER) for an additive white Gaussian noise channel with noise variance equal to the average variance of the impulse noise. However, in an OFDM-based system, the noise variance per symbol at the output of the demodulator, as well as the error floor in the BER curves, are fixed and independent of the impulsive index A. The proposed analysis allows us to compare binary FSK and OFDM under the same theoretical noise conditions.

SummaryThis paper proposes a coded modulation scheme based on frequency shift keying (FSK) modulation and a simple binary permutation code. FSK detection is based on the knowledge of the probability density function (PDF) of the noise and the attenuation of the channel, called FSK “Soft‐Decision” (FSK/SD) detection. We introduce an approximation of the FSK/SD, called FSK “Select Largest” (FSK/SL). We compare the FSK/SL detection with the classical PDF‐based detection techniques, such as FSK/SD and spread‐FSK (SFSK), for both coded and uncoded transmission. As a practical application, we use the power line communication (PLC) channel. We analyze and compare the performances for a narrowband PLC channel with attenuation and impulse noise.

Recognizing whether the current place has been visited before or not is an important task in robotic navigation, since it helps to reduce the inconsistencies produced by the inherent noise of navigation sensors. When a camera is used as input for navigation, this process is known as visual loop closure detection. Under this context, in this work we propose a loop closure detection method based on superpixels and a Bag of Words scheme. A novel image description method for superpixels is proposed. Our approach also makes use of the concept of dynamic islands, which allows us to group images close in time and to avoid images taken from the same place to compete among them as loop closure candidates. The proposed method is validated using several outdoor public image sequences and compared to other state-of-the-art solutions.

This paper presents a novel low-complexity fully parametric frequency-dependent impulse noise model for Narrow-Band PLC in the frequency band below 500 kHz. The statistical characterization of measured noise in terms of impulse temporal waveform and the average PSD allowed to confirm the limitations of the commonly used Middleton class-A model due to its flat PSD that is not matching measurements results. To improve the impulse noise model matching with measurement results, a two-state model using impulses in the form of damped sinusoids is proposed. Comparison of the time and frequency characteristics of the proposed model with measurement show the presence of modeled pulses with shapes close to the measured noise, as well as a good matching in the average PSD. Simulation results in using the proposed model for FSK and OFDM systems design show good accuracy to the measured noise, in terms of detector outputs in 2-FSK, bit error rates and fraction of errors per sub-band in the OFDM-based transmission. (C) 2019 Published by Elsevier GmbH.

This contribution proposes a coding procedure for the binary frequency shift keying (FSK) modulation, to combat the severe narrowband power line communication (NB-PLC) channel constraints, in particular, the impulse noise (IN). The coding procedure is composed of a short 2-error correcting Bose-Chaudhuri-Hocquenghem (BCH) block code concatenated with a permutation code (PC) with a minimum distance of dmin = 2. The parameters of the BCH codes are optimized to delete the error floor (EF) effect caused by the IN. Three different decision techniques are compared, which are FSK select largest (FSK/SL), FSK soft decision (FSK/SD), and spread FSK (SFSK). The proposed concatenated codes scheme using FSK/SL gives the same performance results achieved by FSK/SD while keeping low computational complexity. The system removes the EF and gives a Bit Error Rate (BER) = 10-5 at Signal-to-Noise Ratio (SNR) = 15.6 dB under realistic PLC channel transfer function and IN conditions, gaining more than 10 dB over the PC only system.

•We performed a Systematic Literature Review about vision-based serious games and virtual reality systems in motor rehabilitation.•We conducted the search using Kitchenham guidelines and assessed the included studies using Downs and Black checklist.•We investigated the feasibility and effectiveness of vision-based technologies in motor rehabilitation.•We proposed a research methodology that assists engineers to better design and report their clinical trials.

This paper analyzes the LTE transmitter imperfections and their effects on modulation accuracy and output spectrum emissions. The Error Vector Magnitude (EVM), Adjacent Channel Leakage Ratio (ACLR) and their analytical expressions based on the specifications of the electronics components of the LTE transmitter are detailed. Using these predictor equations, a complete LTE transmitter dimensioning meeting LTE standard requirements is provided. The analytical results are also validated by an experimental set up based on AD9361 SDR board and GaN Power Amplifier (PA) from Analog Devices.

This paper proposes a random channel generator for the narrowband power line communication (PLC). Based on the top-down approach, an analytical formulation with a limited set of parameters is established for the PLC channel transfer function in the frequency band below 500 kHz. Then, the extracted parameters deduced from measurements are fitted with proper distribution functions. The top-down random channel generator is validated through the comparison between measured and generated channels in terms of time-frequency characterization metrics, especially the average channel attenuation, the root mean square (RMS) delay spread and the coherence bandwidth. Obtained results show the good agreement between the proposed modeled channels and the experimental ones with very close mean values and distributions of the main metrics.

In this paper, we compare FSK, SFSK and OFDM modulation techniques performances, widely used for narrow band powerline communication systems. The signals are modulated using binary and quaternary mappings, then exposed to realistic measured narrowband PLC channel attenuation and noise. 4-SFSK proves to have the best BER performances, achieving BER lower than 10 -5 under the channel effect for SNRs higher than 18 dB while OFDM-QPSK is limited to 10 -3 .

We aimed at determining the effects of prototype games on older adults attending a rehabilitation program in an elderly house in this work. We conducted an initial case study where two participants underwent a 5-week intervention. Feasibility was assessed by examining recruitment, adherence, and safety. The Tinetti balance test was used as pretest and posttest assessments. Results show that adherence was very high and no adverse effects were registered during the sessions. The included participants also reported enjoyment during the playtime and exhibited improvements in Tinetti scores. The findings suggest that game-based rehabilitation can be useful for improving balance in elderly people and can be incorporated in a fall prevention program.

This paper details the design of a Digital Predistorter (DPD) based on the Simplified Volterra Series (SVS) model. Our main contributions concern first the design of the predistorter unit using the Look Up Table (LUT) method without additional algorithms to decrease the high number of coefficients required for the PA model. Then, a Matlab and Modelsim cosimulation approach is discussed and performed to evaluate the proposed DPD architecture, in particular synthesis results are presented in terms of required Field Programmable Gate Array (FPGA) resources to implement the proposed predistorter. In addition, the performances of the proposed design are verified using a class AB GaN Power Amplifier (PA) driven by one carrier Long Term Evolution-Advanced (LTE-A) signal with 20 MHz channel bandwidth. It is proven that the LUT predistorter occupies only 55 % of the multipliers (DSP48E1) available in the Zynq-7000 FPGA. Also, the Adjacent Channel Power Ratio (ACPR) attains more than -45 dB.

In Wireless GNSS navigation, there is a high demand for a potential multi-standard receiver capable to improve the performance and decrease the complexity. The key solution to achieve a better accuracy position is to integrate new structure based on RF sampling (RFS). In this paper, this novel structure is introduced, analyzed and implemented using discrete components. Notably, the proposed architecture has the potential to be reconfigured in a sample, flexible and cost-effective manner. To evaluate the operational and the functionality of the designed receiver, experimental tests are accomplished. Three kinds of signals are expound 1) recorded signals reproducing the original ones are played. It can be arranged in such a way that signal is recorded on a standalone device, such as the one by Spirent system 2) simulated signals arranged by the Rohde & Schwarz systems including PRN code of satellites (4,10,31) 3) using a real constellation of GPS L1 while testing signals from GPS antenna. The GPS RF signal tested which assume values in band L1 (fc=1575.42 Mhz) and L2 (fc=1227.6MHz) is down converted to intermediate frequency signals (FIF) at a rate sampling frequency (Fs) varied with the RF signal's input. The resulting signal crossing the RF front end and a BandPass sample (BPS) ADC device is acquired by employing the parallel code phase search acquisition algorithm (PCPA) which can determine visible satellites then tracked and used them for positioning. The experimental sensitivity measured for the R&S is -110 dBm and -95 dBm for Spirent simulator.

Global Navigation Satellite Systems (GNSS) are widespread around the world providing users with several services from GPS, GLONASS, GALILEO and BEIDOU satellites. Localization and positioning applications use GNSS receivers to find navigation position. Thus, the implementation of a reconfigurable multi-constellation receiver should be highlighted. This paper presents a reconfigurable GNSS receiver setup based on the sub-sampling architecture. First, the evaluation of the sampling frequencies for different scenarios is performed in order to include various standards at the same time. Then, experimental assessment to detect the visible satellites while handling GPS and GLONASS signals are successfully established and it validates the proposed multi standard GNSS sub-sampling receiver operation for GPS and GLONASS.

A novel reconfigurable dual-bandpass filter with independently controlled center frequencies and fixed bandwidths is presented. It was designed to be integrated as a radio frequency anti-aliasing filter in a reconfigurable multi-bandpass sampling global navigation satellite system (GNSS) receiver. The center frequency tuning ranges are 1190–1210 MHz and 1560–1590 MHz in the lower and the upper L-bands, respectively, with a fixed bandwidths of 35 MHz. Varactor tuning technology associated with open loop stub loaded resonator microstrip topology were investigated to achieve these goals. The proposed dual-bandpass filter design showed the agility to independently control the center frequencies in the two L-bands and to deactivate one of the passbands. Furthermore, it shows enough flexibility to adapt to the deployment of new GNSS standards specifications. It exhibits on all the tuning ranges an insertion and a return losses of less than 4.5 dB and more than 10 dB, respectively.

We have developed a multi-standard GNSS (Global Navigation Satellite System) receiver including the simultaneous detection of the four current constellations: GPS, GLONASS, Galileo and Beidu. The technique used is sub-sampling, which simplifies the receiver architecture. A special feature of our implementation is that the "indoor" aspect is already taken into account at the design stage. The latter is further considered by the use of pseudo-satellites ("pseudolites") of particular architecture, the "Grin-Locs". In our case, we have adapted the frequency bands of the various constellations in order to include the associated indoor constraints in our sub-sampling design. This article presents the problem of indoor using Grin-Locs and the performances obtained with our multi-standard subsampling receiver in phase measurements of signals for indoor positioning.

The purpose of this paper is to compare two estimation methods when identifying the coefficients of the Simplified Volterra Series (SVS) model, in order to linearize a class AB GaN Power Amplifier (PA) driven by a 20-MHz LTE-A signal. First, a Digital Predistorter (DPD) design using the cholesky decomposition based inversion method and the Least Square QR (LSQR) algorithm is carried out, and next the performances of each method are analyzed in terms of computational complexity and suppressing distortions capability. The co-simulation test results show that the LSQR performs better than Cholesky decomposition in terms of Adjacent Channel Power Ratio (ACPR) and Normalized Mean Square Error (NMSE) by a margin of 3 dB and 4 dB, receptively.

In this paper, two decision methods for the quaternary conventional and spread frequency shift keying (4-FSK and 4-SFSK) are detailed and their extension to the coded 4-FSK and 4-SFSK using the permutation coding are proposed. The performance results of the different methods are studied under the real indoor narrowband PLC (NB PLC) channel attenuation and impulse noise. The BER performances of the different techniques prove that the coded 4-FSK using the Select Largest decoding method achieves the best performance results in the NB-PLC environment while having a low complexity, in comparison with SFSK system. The proposed decoding scheme C FSK/SL gives an error floor equal to 2×10−4 while SFSK achieves 1.5×10−3 under the PLC channel and impulse noise effects.