29,530 research outputs found
Advanced Algorithms for Satellite Communication Signal Processing
DizertaÄnĂ prĂĄce je zamÄĆena na softwarovÄ definovanĂ© pĆijĂmaÄe urÄenĂ© k ĂșzkopĂĄsmovĂ© druĆŸicovĂ© komunikaci. KomunikaÄnĂ kanĂĄly druĆŸicovĂœch spojĆŻ zahrnujĂcĂch komunikaci s hlubokĂœm vesmĂrem jsou zatĂĆŸeny vysokĂœmi ĂșrovnÄmi ĆĄumu, typicky modelovanĂ©ho AWGN, a silnĂœm DopplerovĂœm posuvem signĂĄlu zpĆŻsobenĂœm mimoĆĂĄdnou rychlostĂ pohybu objektu. DizertaÄnĂ prĂĄce pĆedstavuje moĆŸnĂ© postupy ĆeĆĄenĂ vĂœpoÄetnÄ efektivnĂ digitĂĄlnĂ downkonverze ĂșzkopĂĄsmovĂœch signĂĄlĆŻ a systĂ©mu odhadu kmitoÄtu nosnĂ© ĂșzkopĂĄsmovĂœch signĂĄlĆŻ zatĂĆŸenĂœch DopplerovĂœm posuvem v ĆĂĄdu nĂĄsobkĆŻ ĆĄĂĆky pĂĄsma signĂĄlu. Popis navrhovanĂœch algoritmĆŻ zahrnuje analytickĂœ postup jejich vĂœvoje a tam, kde je to moĆŸnĂ©, i analytickĂ© hodnocenĂ jejich chovĂĄnĂ. Algoritmy jsou modelovĂĄny v prostĆedĂ MATLAB Simulink a tyto modely jsou vyuĆŸity pro ovÄĆenĂ vlastnostĂ simulacemi. Modely byly takĂ© vyuĆŸity k experimentĂĄlnĂm testĆŻm na reĂĄlnĂ©m signĂĄlu pĆijatĂ©m z druĆŸice PSAT v laboratoĆi experimentĂĄlnĂch druĆŸic na Ășstavu radioelektroniky.The dissertation is focused on software defined receivers intended for narrowband satellite communication. The satellite communication channel including deep space communication suffers from a high level of noise, typically modeled by AWGN, and from a strong Doppler shift of a signal caused by the unprecedented speed of an object in motion. The dissertation shows possible approaches to the issues of computationally efficient digital downconversion of narrowband signals and the carrier frequency estimation of narrowband signals distorted by the Doppler shift in the order of multiples of the signal bandwidth. The description of the proposed algorithms includes an analytical approach of its development and, if possible, the analytical performance assessment. The algorithms are modeled in MATLAB Simulink and the models are used for validating the performance by the simulation. The models were also used for experimental tests on the real signal received from the PSAT satellite at the laboratory of experimental satellites at the department of radio electronics.
Performance of an Echo Canceller and Channel Estimator for On-Channel Repeaters in DVB-T/H Networks
This paper investigates the design and performance of an FIR echo canceller for on-channel repeaters in DVB-T/H network within the framework of the PLUTO project. The possible
approaches for echo cancellation are briefly reviewed and the main guidelines for the design of such systems are presented. The main system parameters are discussed. The performance of an FIR echo canceller based on an open loop feedforward approach for channel estimation is tested for different radio channel conditions and for different number of taps of the FIR filter. It is shown that a minimum number of taps is recommended to achieve a certain mean rejection ratio or isolation depending on the type of channel. The expected degradation in performance due to the use of fixed point rather than floating point arithmetic in hardware implementation is presented for different number of bits. Channel estimation based on training sequences is investigated. The performance of Maximum Length Sequences and Constant Amplitude Zero Autocorrelation (CAZAC) Sequences is compared for different channels. Recommendations are given for training sequence type, length and
level for DVB-T/H on-channel repeater deployment
Modeling of wide-band MIMO radio channels based on NLoS indoor measurements
Link to published version (if available)
Universality and Realistic Extensions to the Semi-Analytic Simulation Principle in GNSS Signal Processing
Semi-analytic simulation principle in GNSS signal processing bypasses the bit-true operations at high sampling frequency. Instead, signals at the output branches of the integrate&dump blocks are successfully modeled, thus making extensive Monte Carlo simulations feasible. Methods for simulations of code and carrier tracking loops with BPSK, BOC signals have been introduced in the literature. Matlab toolboxes were designed and published. In this paper, we further extend the applicability of the approach. Firstly, we describe any GNSS signal as a special instance of linear multi-dimensional modulation. Thereby, we state universal framework for classification of differently modulated signals. Using such description, we derive the semi-analytic models generally. Secondly, we extend the model for realistic scenarios including delay in the feed back, slowly fading multipath effects, finite bandwidth, phase noise, and a combination of these. Finally, a discussion on connection of this semi-analytic model and position-velocity-time estimator is delivered, as well as comparison of theoretical and simulated characteristics, produced by a prototype simulator developed at CTU in Prague
Communication Subsystems for Emerging Wireless Technologies
The paper describes a multi-disciplinary design of modern communication systems. The design starts with the analysis of a system in order to define requirements on its individual components. The design exploits proper models of communication channels to adapt the systems to expected transmission conditions. Input filtering of signals both in the frequency domain and in the spatial domain is ensured by a properly designed antenna. Further signal processing (amplification and further filtering) is done by electronics circuits. Finally, signal processing techniques are applied to yield information about current properties of frequency spectrum and to distribute the transmission over free subcarrier channels
Preprint: Using RF-DNA Fingerprints To Classify OFDM Transmitters Under Rayleigh Fading Conditions
The Internet of Things (IoT) is a collection of Internet connected devices
capable of interacting with the physical world and computer systems. It is
estimated that the IoT will consist of approximately fifty billion devices by
the year 2020. In addition to the sheer numbers, the need for IoT security is
exacerbated by the fact that many of the edge devices employ weak to no
encryption of the communication link. It has been estimated that almost 70% of
IoT devices use no form of encryption. Previous research has suggested the use
of Specific Emitter Identification (SEI), a physical layer technique, as a
means of augmenting bit-level security mechanism such as encryption. The work
presented here integrates a Nelder-Mead based approach for estimating the
Rayleigh fading channel coefficients prior to the SEI approach known as RF-DNA
fingerprinting. The performance of this estimator is assessed for degrading
signal-to-noise ratio and compared with least square and minimum mean squared
error channel estimators. Additionally, this work presents classification
results using RF-DNA fingerprints that were extracted from received signals
that have undergone Rayleigh fading channel correction using Minimum Mean
Squared Error (MMSE) equalization. This work also performs radio discrimination
using RF-DNA fingerprints generated from the normalized magnitude-squared and
phase response of Gabor coefficients as well as two classifiers. Discrimination
of four 802.11a Wi-Fi radios achieves an average percent correct classification
of 90% or better for signal-to-noise ratios of 18 and 21 dB or greater using a
Rayleigh fading channel comprised of two and five paths, respectively.Comment: 13 pages, 14 total figures/images, Currently under review by the IEEE
Transactions on Information Forensics and Securit
A Software-Defined Channel Sounder for Industrial Environments with Fast Time Variance
Novel industrial wireless applications require wideband, real-time channel
characterization due to complex multipath propagation. Rapid machine motion
leads to fast time variance of the channel's reflective behavior, which must be
captured for radio channel characterization. Additionally, inhomogeneous radio
channels demand highly flexible measurements. Existing approaches for radio
channel measurements either lack flexibility or wide-band, real-time
performance with fast time variance. In this paper, we propose a correlative
channel sounding approach utilizing a software-defined architecture. The
approach enables real-time, wide-band measurements with fast time variance
immune to active interference. The desired performance is validated with a
demanding industrial application example.Comment: Submitted to the 15th International Symposium on Wireless
Communication Systems (ISWCS 2018
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