Generalized Exponential Decay Model for Power–Delay Profiles of Multipath Channels (original) (raw)
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Theory of multipath shape factors for small-scale fading wireless channels
IEEE Transactions on Antennas and Propagation, 2000
This paper presents a new theory of multipath shape factors that greatly simplifies the description of small-scale fading statistics of a wireless receiver. A method is presented for reducing a multipath channel with arbitrary spatial complexity to three shape factors that have simple intuitive geometrical interpretations. Furthermore, these shape factors are shown to describe the statistics of received signal fluctuations in a fading multipath channel. Analytical expressions for level-crossing rate, average fade duration, envelope autocovariance, and coherence distance are all derived using the new shape factor theory and then applied to several classical examples for comparison. Index Terms-Angle of arrival, diversity, fading channels, mobile communications, multipath channels, propagation, scattering. I. INTRODUCTION T HE motion in space of a wireless receiver operating in a multipath channel results in a communications link that experiences small-scale fading. The term small-scale fading describes the rapid fluctuations of received power level due to small subwavelength changes in receiver position [1]. This effect is due to the constructive and destructive interference of the numerous multipath waves that impinge upon a wireless receiver [2]. The resulting signal strength fluctuations affect, in some way, nearly every aspect of receiver design: dynamic range, equalization, diversity, modulation scheme, and channel and error-correction coding. Due to its random unpredictable nature, small-scale fading is always studied as a stochastic process. Numerous researchers have measured and analyzed the first-order statistics of these processes, which mostly involves the characterization of smallscale fading with a probability density function (PDF) [3]-[5]. The autocorrelation statistics of fading processes or secondorder statistics have also been studied [6], [7]. Second-order statistics include measures of a process such as power spectral density (PSD), level-crossing rate, and average fade duration. Second-order statistics are heavily dependent on the angles-of-arrival of received multipath. Traditionally, most second-order statistics have been studied using an omnidirectional azimuthal propagation model [2]. That is, multipath waves are assumed to arrive at the receiver with equal power
Methods for modeling of specified and measured multipath power-delay profiles
IEEE Transactions on Vehicular Technology, 2002
In this paper, five fundamental methods are proposed to model the multipath power-delay profile of frequency-selective indoor and outdoor wireless channels. Three of them are new, and the other two are well known, but their performance, however, has not been studied in detail up until now. All procedures are universally valid so that they can be applied to any specified or measured multipath power-delay profile. The performance of the proposed methods is investigated with respect to important characteristic quantities such as the frequency correlation function (FCF), average delay, and delay spread. The method found to perform best is the so-called-norm method (LPNM). This procedure is applied to measurement data of multipath power-delay profiles collected in different propagation environments. It is shown that the realization complexity of tapped-delay line-based simulation models for fading channels can be reduced considerably by using the LPNM. This is a great advantage for the development and specification of channel models for future wireless systems. Index Terms-Deterministic channel modeling, mobile radio channels, multipath channels, multipath power-delay profile, tapped-delay line model.
IJERT-Analysis of proposed power delay profile pdp for mimo ofdm systems IJERTV2IS
International Journal of Engineering Research and Technology (IJERT), 2013
https://www.ijert.org/analysis-of-proposed-power-delay-profile-pdp-for-mimo-ofdm-systems https://www.ijert.org/research/analysis-of-proposed-power-delay-profile-pdp-for-mimo-ofdm-systems-IJERTV2IS100731.pdf The aim of this paper is to investigate the OFDM scheme, and realize a fully functional system and analyzing how it is reducing the inter-symbol interference caused by the multipath fading channels and different effects and estimating, evaluating the performance of it. The paper proposes a power delay profile (PDP) estimation technique for linear minimum mean square error (LMMSE) channel estimator of multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. For practical applications, only the pilot symbols of all transmit antenna ports are used in estimating the PDP. The distortions caused by null subcarriers and an insufficient number of samples for PDP estimation is also considered. The proposed technique effectively reduces the distortions for accurate PDP estimation. Simulation results show that the performance of LMMSE channel estimation using the proposed PDP estimate approaches that of Wiener filtering due to the mitigation of distortion effects
Stochastic models for long-term multipath fading channels and their statistical properties
Conference on Decision and Control, 1999
This paper discusses the use of stochastic differential equations and point processes to model the long-term fading effects during transmission of electromagnetic waves over large areas, which are subject to multipaths and power loss due to long distance transmission and reflections. When measured in dB's, the power loss follows a mean reverting Ornstein-Uhlenbeck process, which implies that the power loss is log-normally distributed. The arrival times of different paths are modeled using non-homogeneous Poisson counting processes and their statistical properties of the multipath power loss are examined. The moment generating function of the received signal is calculated and subsequently exploited to derive a central limit theorem, and the second-order statistics of the channel.
Joint Modeling of Received Power, Mean Delay, and Delay Spread for Wideband Radio Channels
IEEE Transactions on Antennas and Propagation
We propose a multivariate log-normal distribution to jointly model received power, mean delay, and root mean square (rms) delay spread of wideband radio channels, referred to as the standardized temporal moments. The model is validated using experimental data collected from five different measurement campaigns (four indoor scenarios and one outdoor scenario). We observe that the received power, the mean delay, and the rms delay spread are correlated random variables, and therefore, should be simulated jointly. Joint models are able to capture the structure of the underlying process, unlike the independent models considered in the literature. The proposed model of the multivariate log-normal distribution is found to be a good fit for a large number of wideband data sets.
Analysis of Multipath Propagation based on Cluster Channel Modelling Approach
The computer simulation approach with an emphasis on the propagation modelling for wireless channels for current and future communication systems is a powerful tool to asses the performance of systems without the need of building them. This paper presents a clustering approach geometry-based channel model, and employs it to derive the power density function (PDF) of the Angle of Arrival (AOA) of the multipath signal components. To evaluate the theoretical clusters PDF in angular domain proposed, we make computer simulations for the geometry-based channel model proposed and compared it with experimental results published in the literature showing good agreement. The clusters PDF derived can be used to simulate the power-delay-angle profile (PDAP) and to quantify second order statistics, i.e., power angular spectrums (PAS) and the associated angular spreads (Ass) for a given elliptical shape of the cluster.
IEEE Transactions on Vehicular Technology, 1991
This paper presents typical and worst case root mean square (rms) delay spreads, excess delay spreads (10 dB) and mean channel path loss at 900 MHz in four European cities using typical cellular and microcellular antenna locations. A power law propagation model is used to determine how the mean wide-band channel path loss changes as a function of distance between a base and a mobile. It is shown that a change in reference distance from 1 km to 100 m can change the perceived propagation power law exponent from 3.0 to 2.7, where free space propagation is assumed from the transmitter to the reference distance. The data reveal that for microcellular sites with low base antennas, rms delay spreads are less than 2 ps with excess delay spreads (10 dB) less than 6 ps. When high base station antennas are used, rms delay spreads are generally less than 8 ps and excess delay spreads (10 dB) are less than 16 ps. The worst case measurement with line-of-sight to the Frankfurt skyline produced a multipath component 7 dB below the direct component at an excess delay of 51.3 ps. The worst case rms delay spread is 19.6 ps. Radar cross sections (RCS) of common scatterers in cellular and microcellular radio channels are shown to range between-4.5 and +55.7 dBm2.
Power delay profile and noise variance estimation for OFDM
IEEE Communications Letters, 2006
In this letter, we present cyclic-prefix (CP) based noise-variance and power-delay-profile estimators for Orthogonal Frequency Division Multiplexing (OFDM) systems. Signal correlation due to the use of the CP is exploited without requiring additional pilot symbols. A heuristic estimator and a class of approximate maximum likelihood (ML) estimators are proposed. The proposed algorithms can be applied to both unitary and non-unitary constellations. These algorithms can be readily used for applications such as minimum mean-square error (MMSE) channel estimation.
Evaluation of metrics for characterising the dispersion of the mobile channel
1996
This paper analyses the suitability of RMS delay spread and coherence bandwidth when characterising system Quality-of-Service of QPSK operating in a variety of wideband mobile channels. It is demonstrated that RMS delay spread is unduly affected by the presence of relatively weak signals with large excess delay, limiting it's effectiveness when characterising time dispersion. Coherence bandwidth is shown to offer a more general dispersion metric.