Doppler Spread Spectrum Research Articles

АНАЛИЗ ИСПОЛЬЗОВАНИЯ ФИЛЬТРА КАЛМАНА В ПРОЦЕДУРЕ ДЕТЕКТИРОВАНИЯ СИГНАЛА В СИСТЕМЕ С MIMO И ПРИЕМНИКОМ ПРЯМОГО ПРЕОБРАЗОВАНИЯ

Introduction: The procedure for detecting a quadrature amplitude modulation (QAM) signal in a communication system with multiple transmitting and receiving antennas (MIMO) is considered, which consists of two stages: obtaining soft solutions using the recurrent Kalman filtering algorithm, finding hard solutions by criterion of minimum distance between soft decision vectors and possible information symbols on each receiving antenna. The Kalman algorithm evaluates symbols at i-th time point in iterations. A comparison is made of noise immunity of QAM signal reception obtained using the Zero Forcing methods, the minimum mean square error (RMS), and recurrent Kalman procedure. Signal processing takes place under channel conditions with Rayleigh fading and Doppler spread spectrum. Cases are considered when the channel matrix is known exactly and when it is estimated by least squares method (LSM) using a first-order polynomial approximation for channel matrix elements. The channel matrix takes into account not only signal distortions due to the propagation medium, but also distortions obtained in the direct conversion receiver, such as amplitude and phase imbalance between signal quadratures, frequency shift due to non-ideal demodulation procedure, as well as DC drift. Result: The computational complexity of the detector based on Kalman algorithm is analyzede.

Doppler Spectrum Analysis for the Prediction of Rotating Mode Stirrer Performances in Reverberation Chamber

This paper presents how the Doppler spectrum (DS) induced by rotating mode stirrers can be used in order to assess and optimize their performances when used in reverberation chambers. Indeed, a rotating mode stirrer acts as a diffracting structure whose performances are related to the DS spread. The performances of such stirrers are shown to be predictable by analyzing their DS in free space from numerical simulations using full-wave solvers with reasonable computation times. This allows the geometry of a future mode stirrer to be optimized before being built and installed in the chamber.

Ocean Surface Wind Direction Inversion Using Shipborne High-Frequency Surface Wave Radar

Shipborne high-frequency surface wave radar (SHFSWR) has exhibited great advantages over onshore HFSWR (OHFSWR) in ocean remote sensing. Unlike OHFSWR, SHFSWR suffers the problem of Doppler spectrum spread owing to platform movement, which is a great challenge preventing the extraction of ocean surface parameters for SHFSWR. To address this challenge, in this letter, the mathematical model of ocean surface wind direction is first investigated based on the first-order SHFSWR cross section. Furthermore, a method for the wind direction inversion without ambiguity from the spread Doppler spectrum is proposed using a single receiving antenna. Meanwhile, the wind directions of the sea area covered by radar can be obtained by sequentially utilizing the proposed method, which is more appropriate for the application of SHFSWR with limited deck space and less cost. Experimental results of the real data collected in Taiwan Strait preliminarily verify the detection accuracy and the distance limit of the wind direction inversion, as the root-mean-square error and the detection range are 9.85° and 120 km, respectively

Optimal complex exponentials BEM and channel estimation in doubly selective channel

Over doubly selective channel, the optimal complex exponentials BEM (CE-BEM) is required to characterize the transmission in transform domain in order to reducing the huge number of the estimated parameters during directly estimating the impulse response in time domain. This paper proposed an improved CE-BEM to alleviating the high frequency sampling error caused by conventional CE-BEM. On the one hand, exploiting the improved CE-BEM, we achieve the sampling point is in the Doppler spread spectrum and the maximum sampling frequency is equal to the maximum Doppler shift. On the other hand we optimize the function and dimension of basis in CE-BEM respectively ,and obtain the closed solution of the EM based channel estimation differential operator by exploiting the above optimal BEM. Finally, the numerical results and theoretic analysis show that the dimension of basis is mainly depend on the maximum Doppler shift and signal-to-noise ratio (SNR), and if fixing the number of the pilot symbol, the dimension of basis is higher, the modeling error is smaller, while the accuracy of the parameter estimation is reduced, which implies that we need to achieve a tradeoff between the modeling error and the accuracy of the parameter estimation and the basis function influences the accuracy of describing the Doppler spread spectrum after identifying the dimension of the basis.

DOPPLER SPREAD SPECTRUM OF A CIRCULARLY MOVING RECEIVER IN AN ANECHOIC AND A REVERBERATION CHAMBER

The Doppler phenomena caused by a moving receiver or environmental scatters around a receiver were emulated in an AC (Anechoic Chamber) and a RC (Reverberation Chamber) using platform and mode stirring. In order to verify the emulated Doppler spread spectrum, the measured results in the AC and the RC were investigated by incorporating Jakes's and 802.11 TGn Doppler models, respectively.

Characteristic and Modeling of Human Body Motions for Body Area Network Applications

Many current and future medical devices are wearable and human body is used as a carrier for wireless communication, which implies human body to be a crucial part of the transmission medium in body area networks (BANs). In order to understand the propagation characteristics around human body, the statistical model is derived for communication links in the medical implant communication service band, industrial scientific medical band and ultra-wideband based on the narrowband measurement. The channel model of diffracting components around human body were different from one scenario to another. Moreover, second order statistics, including level crossing rate and fade duration, are presented for each scenario to evaluate the link quality and outage performance for on-body to on-body scenario. Using a network analyzer, Doppler spread spectrum in frequency domain and coherence time in time domain from temporal variations of human body movements are also analyzed from diverse perspectives. Additionally, the shape of Doppler spread spectrum is fitted to describe the relationship of power and frequency. The proposed on-body to on-body channel model for human body motions can be used to better design wireless network protocols for BANs.

Spectral Properties of Modulated Signal in the Doppler Domain in Urban Radio Channels With Fading

We examine propagation of frequency modulated (FM ) radio signals in the urban environments for different elevations of base station (BS) and mobile subscriber (MS) antennas, below and above the rooftops, based on the stochastic multi-parametric approach. We concentrate our attention on the spectral properties of signal power variations in the frequency domain and describe them based on the Doppler-spread spectrum of bandpass signal power. In the framework of the stochastic approach, the total signal power, the correlation function, the Ricean K-parameter of fading, and the scale of correlation of different spectral components of the modulated signal are analyzed. A practical aspect of relationship between the correlation scale of any two components of the FM signal and the coherent bandwidth of the urban channel with fading is examined via prism of special experiment. New effects of buildings' density and the elevation of BS antenna on above characteristics of the FM signal are examined numerically. It is found that, depending on various scenarios occurring in the urban scene, the buildings' density and the elevation of BS antenna can significantly distort the modulated signal within radio link with fading.

Characterizing the Impact of Moving Mode-Stirrers on the Doppler Spread Spectrum in a Reverberation Chamber

A moving mode-stirrer in a reverberation chamber (RC) not only changes the field distributions within the reverberation chamber, but also causes a Doppler effect. In this letter, the Doppler spread spectrum of a received signal in a reverberation chamber is characterized according to the radius and rotational velocity of the mode-stirrers and TX antenna positions.

Advanced and Applications in Vehicular Ad Hoc Networks

Recently there is a strong interest in developing networking techniques and important applications for moving vehicles, to enable wireless communication between roadside and vehicles or between vehicles. Vehicular ad hoc networks (VANETs) using all kinds of wireless technologies has recently received considerable attention. The goal of this special issue is to explore the development of wireless vehicular ad hoc network technologies about communication, networking, and applications. The communication protocol design will affect the performance results. A good communication protocol design can achieve highly reliable, highly scalable, and high performance. In aspect of networking, there are many challenges that how to offer quality of service, build high performance routing, provide mobility management, and create secure vehicular ad hoc networks. VANET safety applications include safety warnings and collision avoidance. It is important to improve the non-safety applications and reduce the occurrence of collision. VANETs present a highly active field of research, development, standardization and field trials. Throughout the world, there are many national/ international projects from government, industry, and academia devoted to VANETs, for example consortia like VSC (US), C2CCC (Europe) and InternetITS (Japan), standardization efforts like IEEE 802.11p (WAVE) and field trials like the large-scale Vehicle Infrastructure Integration Program (VII) in the US. The call for papers for this Special Issue attracted more than 50 submissions from Asia, Europe, and the US covering many topics this Special Issue focuses on. Each paper was carefully evaluated by at least two reviewers. Based on the review results, we selected 13 high quality research papers to be included in this Special Issue. We strongly believe that the selected papers will make a significant contribution to researchers, practitioners, and students working in the area of the VANET. Our special thanks go to Dr. Imrich Chlamtac (Editor-inChief) and Katiuscia Buonaiuto for their valuable support throughout the preparation of this Special Issue. We would like to thank all authors who have submitted papers to the Special Issue and in particular those whose papers have been accepted for this Special issue. Assistance from the editorial staff of the Mobile Networks and Applications journal is also very much appreciated. Finally, the Guest Editors wish to gratefully acknowledge all those who have generously given their time to review the papers submitted for consideration for this SI. The thirteen accepted papers are divided into three categories. Two papers relate to channel modeling or access. “Channel Modeling and Inter-Carrier Interference Analysis for V2V Communication Systems in FrequencyDispersive Channels” by Hsiao-Hwa Chen et al. presents a practical model to characterize V2V communication channel and its corresponding Doppler spread spectrum is derived. “Cooperative and Opportunistic Channel Access for Vehicle to Roadside (V2R) Communications” by Wanjiun Liao et al. proposes a new mechanism called Proxy-based Vehicle to exploit cooperative and opportunistic forwarding between any H.-C. Chao (*) National Ilan University, I-Lan, Taiwan e-mail: hcc@niu.edu.tw

Channel Modeling and Inter-Carrier Interference Analysis for V2V Communication Systems in Frequency-Dispersive Channels

Vehicle-to-vehicle (V2V) communication has attracted much attention recently. In V2V communications mobility plays a major role in yielding frequency dispersion of the channels, and thus accurately modeling of Doppler effect becomes a challenging issue as the two fundamental assumptions of the Jack's model may not be valid due to time-varying channel characteristics in V2V communication systems. In this paper, we present a practical model to characterize V2V communication channel and its corresponding Doppler spread spectrum is derived. In addition, we will study the impact of inter-carrier interference (ICI) generated in an orthogonal frequency division multiplexing (OFDM) based V2V communication system. Compared with the classical Jake's channel model, our proposed new channel model is more accurate and fits in particular well for the performance assessment of vehicle-to-vehicle communication systems.

Spectral properties of signal fading and Doppler spectra distribution in urban mobile communication links

AbstractIn this work, we continue the analysis of a probabilistic approach and the corresponding stochastic multi‐parametric model of wave propagation, in built‐up areas with randomly distributed buildings. We have concentrated on the spectral properties of signal strength spatial variations and on Doppler spread spectrum distribution of signal power. The analysis is based on a unified stochastic approach of radio wave propagation above the built‐up terrain with applications to mobile communications. We analyze the signal power spectrum of spatial frequencies and the signal power distribution in the Doppler domain for moving vehicles, taking into account a Doppler shift proportional to the vehicle antenna speed relative to the base station. The comparison between the theoretical prediction and experimental data was motivated by the proposed stochastic model and other existing statistical models to verify the signal power distribution in the Doppler domain for various urban environments and terminal heights with respect to building rooftops. New effects of terrain features on signal spectrum are obtained, examined and compared with existing models. Copyright © 2006 John Wiley & Sons, Ltd.