Search results for "Computer Science::Information Theory"
showing 10 items of 272 documents
On the Problems of Symbol-Spaced Tapped-Delay-Line Models for WSSUS Channels
2007
Article from the journal: Wireless Communications and Mobile Computing The deposited fulltext is a preprint of the definitive article at Wiley Interscience http://dx.doi.org/10.1002/wcm.683 This paper analyzes the validity and statistical behavior of symbol-spaced tapped-delay-line (SSTDL) models for wide-sense stationary uncorrelated scattering (WSSUS) mobile radio channels. SSTDL models are obtained by sampling the channel impulse response (CIR) in delay domain at a rate equal to the reciprocal of the symbol duration. They were proposed more than four decades ago as canonical channel models for band-limited timevariant linear (TVL) systems, and are nowadays widely in use for assessing the…
A Novel Method of Distance Measurement Based on Pulse Position Modulation and Synchronization of Chaotic Signals Using Ultrasonic Radar Systems
2009
This paper deals with a novel method of transmission and receipt of a signal based on both the property of two chaotic systems generating the same chaotic signal when they are synchronized and the property of pulse position modulation (PPM) to be insensitive to the distortions of the transmission channel. The method is discussed in the context of ultrasonic radar systems, in which the transmitter and receiver, which consist of ultrasonic sensors, are near each other, and the received signal consists of the transmitted signal reflected by an obstacle. A reference sinusoidal signal is superimposed to a chaotic signal generated by a master chaotic system, and the whole signal is modulated acco…
Modelling the Doppler Power Spectrum of Non-Stationary Underwater Acoustic Channels Based on Doppler Measurements
2017
This paper proposes a non-stationary time-continuous simulation model for wideband shallow underwater acoustic (UWA) channels based on measured Doppler power spectrums (DPSs). Measurement-based channel simulators are essential for the test, optimization, and performance analysis of UWA communication systems. The aim is to fit the DPS of the simulation model to that of the measured UWA channel. The performance of the designed UWA channel simulator is assessed by comparing the average Doppler shift and Doppler spread of the channel simulator with the corresponding quantities of the measured UWA channel. The results of the assessment show a good match between the statistical quantities of the …
A Non-Stationary MIMO Vehicle-to-Vehicle Channel Model Derived from the Geometrical Street Model
2011
In this paper, we derive a non-stationary multiple-input multiple-output (MIMO) vehicle-to-vehicle (V2V) channel model from the geometrical street model. Single-bounce scattering is assumed for both fixed and moving scatterers. The high mobility of the transmitter, the receiver, and the surrounding vehicles results in time-variant angles-of-departure (AODs) and angles-of-arrival (AOAs). This fact makes the model non-stationary. Starting from the geometrical model, an analytical expression is derived for the channel gain taking into account the impact of fixed and moving scatterers. The statistical properties of the proposed channel model are studied. Analytical solutions are provided for th…
Detection of defective elements in an X band array antenna from its near field measurements
2007
An algorithm has been used to detect defective elements errors in array antennas. It has been applied to an X band slot array antenna and good results have been obtained. These have enabled the detection of errors in the manufacture process. We have used spherical near field measurements of the radiated field of the antenna. Then, once the equivalent currents are be obtained, an analysis of these results will be made in order to detect possible mistakes.
The design of measurement-based underwater acoustic channel simulators using the INLSA algorithm
2015
This paper utilizes the iterative nonlinear least square approximation (INLSA) algorithm for designing measurement-based wideband shallow underwater acoustic (UWA) channel simulators. Measurement-based channel simulators are essential for the test, optimization, and performance analysis of UWA communication systems. The aim is to fit the time-variant channel impulse response (TVCIR) of the simulation model to that of the measured UWA channel. The performance of the designed UWA channel simulator is assessed by comparing the time-frequency correlation function (TFCF), the power delay profile (PDP), and the probability density function (PDF) of the channel envelope with the corresponding quan…
Nash codes for noisy channels
2012
This paper studies the stability of communication protocols that deal with transmission errors. We consider a coordination game between an informed sender and an uninformed decision maker, the receiver, who communicate over a noisy channel. The sender's strategy, called a code, maps states of nature to signals. The receiver's best response is to decode the received channel output as the state with highest expected receiver payoff. Given this decoding, an equilibrium or "Nash code" results if the sender encodes every state as prescribed. We show two theorems that give sufficient conditions for Nash codes. First, a receiver-optimal code defines a Nash code. A second, more surprising observati…
The DMT of Real and Quaternionic Lattice Codes and DMT Classification of Division Algebra Codes
2021
In this paper we consider the diversity-multiplexing gain tradeoff (DMT) of so-called minimum delay asymmetric space-time codes. Such codes are less than full dimensional lattices in their natural ambient space. Apart from the multiple input single output (MISO) channel there exist very few methods to analyze the DMT of such codes. Further, apart from the MISO case, no DMT optimal asymmetric codes are known. We first discuss previous criteria used to analyze the DMT of space-time codes and comment on why these methods fail when applied to asymmetric codes. We then consider two special classes of asymmetric codes where the code-words are restricted to either real or quaternion matrices. We p…
Semi-analytic single-channel and cross-channel nonlinear interference spectra in highly-dispersed WDM coherent optical links with rectangular signal …
2013
We provide new single-integral formulas of the power spectral density of single-channel and cross-channel nonlinear interference in highly-dispersed coherent optical links for which the Gaussian Noise model [1], [2] applies.
An Electrical Tuner to Command Optical NanoAntennas
2010
Optical antennas are passive device where fabrication designs decide operating frequency, gain and emission diagram. By introducing an electrically controllable load medium for the antenna, these characteristics can be externally controlled.