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As small-scale fading is a spatial phenomenon, the movement of objects in the environment around static sensor nodes can induce significant fades. However, there have not been many works characterizing small-scale fading due to environmental factors for ground-surface wireless communications. We first measure the temporal fading characteristics experienced by antennas located just 1.5 cm above the surface of the ground due to wind-blown foliage or human movement in the environment for a narrowband channel in the 400-MHz frequency band. We then compare the extracted data to existing distributions and show that fading due to wind-blown foliage can be modeled as a Nakagami-m distribution, with wind speed and excess path-loss-dependent m shape factors. The \alpha-\mu distribution best characterizes the small-scale fading of a single human pedestrian, which is shown to have a repeatable pattern and can be up to 40 dB below the no-fading mean, whereas the Rician distribution, with an excess path-loss-dependent K-factor, can be used to characterize fading from multiple human pedestrians. We also report the second-order statistics of the average fade duration and the level crossing rate for fading caused by wind-blown foliage and multiple human pedestrians. Finally, we discuss the significance of the results on wireless sensor network protocol design and applications. [ABSTRACT FROM PUBLISHER]

Land mobile satellite (LMS) channels at the L (1/2 GHz) and S (2/4 GHz) frequency bands are mainly affected by propagation effects due to the local environment of a mobile terminal, such as multipath, shadowing, and blockage. Future systems for mobile satellite services (MSS) will operate at higher frequency bands, such as Ku (12/14 GHz) and Ka (20/30 GHz), where the tropospheric propagation effects also play an important role. Experimental campaigns conducted so far for Ku/Ka-band LMS channels have not considered any possible correlation between the tropospheric and local environment propagation effects. However, recent experimental work has indicated that these fading effects are not independent. As a first analytical approach to this open problem, a novel statistical analysis is presented in this paper. Emphasis is put on Ku/Ka-band LMS channels whose fading events can be modeled by the Ricean distribution with a relatively high K-factor. A novel analytical relationship between the Ricean K-factor and the rain attenuation effects is derived, and based on them, an analytical statistical prediction model for the distribution of the Ricean K-factor is derived. Particular attention is paid to the rainfall spatial inhomogeneity, as well as to the different effects of the climatic area of interest (temperate versus tropical) on the Ricean K-factor statistics. Thus, the presented analysis considers both spatially correlated bivariate lognormal and gamma statistics for the accurate characterization of rain attenuation. The proposed models are flexible and incorporate the impact of several critical operational, climatic, and geometrical parameters of an LMS channel on its multipath behavior under rainfall conditions. Useful numerical results are provided, specific future planned work is outlined, and the need for further experimental verification data is also pointed out. [ABSTRACT FROM AUTHOR]

A propagation model is needed to evaluate the performance of handover in mobile-communication systems. Generally, the received signal level from base stations (BSs) is calculated assuming path loss, and a lognormal (shadow)-fading model is used for evaluating intercell handover. The lognormal fading was assumed to be uncorrelated between cells. However, since the correlation between sectors is not clarified, an appropriate shadow-fading model to evaluate intersector handover has not yet been proposed. To obtain shadow-fading characteristics between neighboring sectors, the change in signal level and the direction of arrival of incoming waves at a BS must be clarified. This paper proposes a simple model of incoming waves to evaluate the performance of intersector handover. The validity of the proposed model is confirmed by comparing the difference between signal levels in BS sectors that are calculated using the proposed model and the measured power azimuth spectrum. [ABSTRACT FROM AUTHOR]

This paper introduces a fading model, which explores the nonlinearity of the propagation medium. It derives the corresponding fading distribution—the α-μ distribution-which is in fact a rewritten form of the Stacy (generalized Gamma) distribution. This distribution includes several others such as Gamma (and its discrete versions Erlang and central Chi-squared), Nakagami-m (and its discrete version Chi), exponential, Weibull, one-sided Gaussian, and Rayleigh. Based on the fading model proposed here, higher order statistics are obtained in closed-form formulas. More specifically, level-crossing rate, average fade duration, and joint statistics (joint probability density function, general joint moments, and general correlation coefficient) of correlated α-μ variates are obtained, and they are directly related to the physical fading parameters. [ABSTRACT FROM AUTHOR]

Stochastic properties of the binary channel that describe the successes and failures of the transmission of a modulated signal over a time-correlated flat-fading channel are considered for investigation. This analysis is employed to develop κth-order Markov models for such a bunt channel. The order of the Markov model that generates accurate analytical models is estimated for a broad range of fading environments. The parameterization and accuracy of an important class of hidden Markov models, known as the Gilbert-Elliott channel (GEC), are also investigated. Fading rates are identified in which the κth-order Markov model and the GEC model approximate the fading channel with similar accuracy. The latter model is useful for approximating slowly fading processes, since it provides a more compact parameterization. [ABSTRACT FROM AUTHOR]

Investigates the correlation properties of shadow fading as a function of angle between two personal communication services-based stations over urban, light urban and suburban terrain. Analysis of interference; Relationship between shadow fading and angles; Information on distance correlation instruments.