1,354,496 research outputs found
Symbol Error Probability Analysis of DFrFT-based OFDM Systems with CFO and STO in Frequency Selective Rayleigh Fading Channels
No full textLocalization of a Nano-transmitter in a Diffusive MC System with Multiple Fully-absorbing Receivers
No full textThis paper presents new results about localization of a pointwise transmitter in a molecular communication (MC) diffusive channel by means of a spherical array whose elements are fully-absorbing (FA) receivers. The performance of two different spherical arrays is analyzed to estimate the position of the transmitter that differ in the configuration of the FA receivers on their surface. The proposed localization method relies on a model that has been recently developed to predict the temporal asymptotic cumulative number of molecules absorbed by each of the FA receivers. The approach first estimates the distances between the transmitter and the FA receivers and then use them in a multilateration technique. One of the most promising applications of localization in telemedicine is targeted-drug delivery, which is realized by means of nano-robots. Numerical results are used to demonstrate the accuracy of the proposed method
Design of DGT-based linear and non-linear equalizers for GFDM transmission
No full textThis paper exploits the parallelism between Discrete Gabor Transform (DGT) and Generalized Frequency-Division Multiplexing (GFDM) that exists when the synthesis function, i.e. the pulse shaping filter, and the analysis function, i.e. the receiving filter, satisfy the Wexler–Raz identity. Choosing functions that satisfy the Wexler–Raz condition allows optimal symbol-by-symbol detection for a DGT-based GFDM receiver in case of transmission over an additive white Gaussian noise channel. However, multipath fading is the major problem of the wireless communication channel, hence, when transmission takes place over frequency selective channel, symbol-by-symbol detection is no longer optimal due to interference generated among the transmitted symbols. In this work, we deal with the design of linear and non-linear receivers for DGT-based GFDM transmission over a frequency selective channel that allows a good trade-off between complexity and performance. Different equalization schemes to mitigate distortions, such as Maximum Likelihood, Zero-Forcing and Minimum Mean-Squared Error, are developed and analyzed. Monte Carlo simulations are used to evaluate the error rate performance achieved with the considered design. A comparison is done with other works in the literature
Communication in Implantable Medical Devices: FEM Simulation to Evaluate the Coating Effects on Transmission
No full textImplantable medical devices hold great promise for treating nervous system disorders. However, their small size requires communication with an external device to process electrophysiological signals. The transmission of these signals is often hindered by biocompatible encapsulation materials and surrounding biological tissues. This study uses FEM simulations in COMSOL Multiphysics to assess how the device’s coating and biological tissues affect 2.4 GHz data transmission, a frequency within the ISM band for implantable device communications. A compact Planar Inverted-F Antenna (PIFA) is used, and S11/S22 parameters are calculated to assess transmission efficiency. Since the coating layer hinders transmission depending on its thickness and material properties, simulations were conducted using three different body types representing varying Body Mass Index (BMI) levels to account for inter-patient variability. Implant safety was evaluated by calculating the Specific Absorption Rate (SAR) and the local temperature increase. The results presented in this work serve as a pilot study to assess the effects of encapsulation materials on wireless communication in implantable devices, laying the groundwork for future ex vivo and in vivo research
Feedback method for estimation and compensation of carrier frequency offset in LTE uplink
No full textLong Term Evolution (LTE) is getting popularity among cellular service providers throughout the World and it is going to dominate cellular systems in coming years. According to 3GPP specifications, LTE adopts Orthogonal Frequency-Division Multiplexing (OFDM) as modulation scheme in the downlink. The problem of systems based on OFDM is that they are prone to Carrier Frequency Offset (CFO). In uplink, LTE uses Single-Carrier Frequency Division Multiple Access (SC-FDMA) instead of OFDM. The main reason of its use is the better peak-to-average power ratio performance in comparison to OFDM, a property required in uplink to increase the duration of the battery of the user device. As OFDM, also SC-FDMA suffers with the problem of CFO. In this paper, a CFO estimation method for LTE uplink is analyzed and simulated by using MATLAB. The proposed method, termed feedback method, uses demodulation reference signals to estimate the CFO. After estimation of CFO, its effect is compensated in time-domain by multiplication with a linear phase
Weighting peer reviewers
No full textOur scientific community faces a sort of paradox. A large bulk of work has been done on data-oriented techniques devised to improve peer reputation and knowledge extraction from data, so as to improve trustworthiness of digital services involving coordination and cooperation among heterogeneous peers. But, perhaps surprisingly, to the best of our knowledge, such techniques have rarely been applied to the (for our own community, crucial) process of reducing noise in the process of peer reviewing our own papers. Goal of this work is to provide initial insights on the applicability of methodologies and tools from inferential statistical to the field of peer review quality control. Our contribution is threefold. First, we propose a statistical model where each technical program committee member (reviewer) is characterized as random noise added to the “actual” value of the paper. Second, we provide an iterative data-oriented approach based on Expectation-Maximization devised to estimate mean value and variance of the noise added by each reviewer; our approach uses only the ratings provided by the reviewers themselves and does not rely on any additional source of a-priori knowledge. Third, we make use of the estimated mean values and variances to improve the accuracy of paper's evaluation and ranking
GFDM Pre-coding and Decoding in a Gabor Setting
No full textThe Gabor transform interpretation of the Generalized Frequency-Division Multiplexing (GFDM) leads to a modeling of the effect of the multipath channel as a Multiple-Input Multiple-Output (MIMO) system on each sub-carrier. In this paper, such a modeling is used to propose new pre-coding and decoding design approaches. Two different power allocation strategies based on a joint transmitter and receiver linear design are introduced. By exploiting the circularity of the resulting MIMO channel on each sub-carrier, an eigendecomposition can be implemented, once and for all, by computing the Discrete Fourier transform. The first proposed power allocation approach guarantees fairness among sub-carriers, while the second minimizes the error rate at the price of unfairness. The benefits achieved by the two approaches are demonstrated by numerical simulations and by comparison with other GFDM equalization and pre/de-coding schemes that, in contrast to the proposed one, work on a sub-symbol basis
Blind iterative singular vectors estimation and adaptive spatial loading in a reciprocal MIMO channel
No full textIn this paper spatial loading in a reciprocal time-varying multiple-input multiple-output (MIMO) channel is considered. We take inspiration from a blind iterative algorithm proposed in the literature to estimate the singular vectors associated to the dominant singular value to perform beamforming. Starting from that, we introduce an iterative algorithm that can estimate all the singular vectors and the associated singular values of the channel matrix. Then the estimated singular vectors are used to transmit over the parallel sub-channels and the associated singular values are considered to implement the rate and power loading algorithm described in this paper. A procedure based on the joint use of the two considered algorithms can be adopted to adaptively maximize the total rate for a given error rate performance and a given constraint on the average transmitted power. Simulation results are used to demonstrate the effectiveness of our approach compared to blind iterative beamforming transmission
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