Exact closed-form expressions for the distribution, the level-crossing rate, and the average duration of fades of the capacity of OSTBC-MIMO channels

This paper deals with some important statistical properties of the channel capacity of multiple-input-multiple-output (MIMO) systems with orthogonal space-time block code (OSTBC) transmission. We assume that all the subchannels are uncorrelated. For OSTBC-MIMO systems, exact closed-form expressions are derived for the probability density function (PDF), the cumulative distribution function (CDF), the level-crossing rate (LCR), and the average duration of fades (ADF) of the channel capacity. Furthermore, it will be shown that these exact closed-form expressions can be used to characterize the channel capacity of single-input-multiple-output (SIMO) and multiple-input-single-output (MISO) systems. In addition, a Gaussian approximation to the exact LCR of the capacity of OSTBC-MIMO systems is derived. The correctness of the derived closed-form expressions and the approximation is confirmed by simulations. © 2009 IEEE. (22 refs.

On the Statistical Properties of Selection Combining Cooperative Diversity over Double Rice Fading Channels

Abstract-This paper investigates the statistical properties of selection combining (SC) cooperative diversity over double Rice narrow-band fading channels under the transparent or amplifyand-forward (AF) strategy. It is assumed that the source, the destination, and relay stations are all equipped with single antenna. The Doppler power spectral density, associated with each of the double Rice fading processes, is considered to be symmetrical about the carrier frequency. Under the above conditions, analytical integral expressions are derived for the probability density function (PDF) and the cumulative distribution function (CDF) of the SC fading envelopes. Also, expressions for the level crossing rate (LCR) as well as the average duration of fades (ADF) are determined. For some cases, the integral expressions are shown to be approximated using the Laplace's method of integration. The approximations are verified to be accurate when the number of relay stations is large. The obtained results include those corresponding to the double Rayleigh and combined Rayleigh×Rice models as special cases of the double Rice fading channel. The validity of all the presented theoretical results are checked by computer simulations. Index Terms-Double Rice fading channels, selection combining (SC) cooperative diversity, probability density function (PDF), cumulative distribution function (CDF), level crossing rate (LCR), average duration of fades (ADF)

Estimation of the Velocity of a Walking Person in Indoor Environments from mmWave Signals

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Level-crossing rate and average duration of fades of non-stationary multipath fading channels

The level-crossing rate (LCR) and average duration of fades (ADF) are important statistical quantities describing the fading behaviour of mobile radio channels. To date, these quantities have only been analysed under the assumption that the mobile radio channel is wide-sense stationary, which is generally not the case in practice. In this paper, we propose a concept for the analysis of the LCR and ADF of non-stationary channels. Rice's standard formula for the derivation of the LCR of wide-sense stationary processes is extended to a more general formula enabling the computation of the instantaneous LCR of non-stationary processes. The application of the new concept results in closed-form expressions for the instantaneous LCR and ADF of non-stationary multipath flat fading channels. The contribution of this paper is of central importance for the statistical characterization of non-stationary mobile radio channels.acceptedVersionnivå

Estimation of the Velocity of a Walking Person in Non-Stationary Indoor Environments from the Received RF Signal

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On the Consistency of Non-Stationary Multipath Fading Channels with Respect to the Average Doppler Shift and the Doppler Spread

This paper is concerned with the consistency of non-stationary multipath fading channels. We introduce conditions under which a channel model is consistent w.r.t. the average Doppler shift and the Doppler spread. The conditions are applied to two classes of non-stationary channel models. The first class, which is termed Class A, is characterized by channel models based on an integral relationship between the path phases and the associated time-variant Doppler frequencies. The second class of models, called the Class B models, emerges from standard sum-of-cisoids (SOC) models by replacing the time-independent Doppler frequencies by time-dependent Doppler frequencies. It is shown that the Class A models fulfil the consistency conditions, while the Class B models are inconsistent. The majority of existing non- stationary channel models with time-dependent Doppler frequencies fall in the Class B category, meaning that these models suffer from a lack of physical soundness. The importance of the paper comes from the fact that it provides guidelines for the design of consistent and physically reasonable non-stationary channel models.acceptedVersionnivå

A Geometry-Based Underwater Acoustic Channel Model Allowing for Sloped Ocean Bottom Conditions

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A Non-Stationary Mobile-to-Mobile Channel Model Allowing for Velocity and Trajectory Variations of the Mobile Stations

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A non-WSSUS mobile-to-mobile channel model assuming velocity variations of the mobile stations

This paper aims to characterize the effects that the velocity variations of the mobile stations (MSs) produce on the correlation properties of non-stationary time-frequency (TF) dispersive mobile- to-mobile (M2M) fading channels. Toward that end, we propose a novel geometrical model for non-wide-sense stationary uncorrelated scattering (non-WSSUS) M2M channels that incorporates such variations following a plane wave propagation approach. Capitalizing on the mathematical simplicity of this approach, we derive a general expression for the four-dimensional (4D) TF correlation function (TFCF) of the proposed channel model. From this expression, we analyze the influence of the MSs' acceleration#x002F;deceleration on the channel's correlation properties. Some simulation examples illustrating our findings are presented for the particular case of the geometrical one-ring scattering model. The proposed channel model can be used as a reference to study the performance of emerging vehicular communication systems in safety-threatening scenarios, such as when a MS is forced to break suddenly.acceptedVersionnivå

Effect of reduced tillage under various mulch types on soil fertility and yield of an organic pepper crop

The effects of mulching on soil characteristics and plant development for pepper crops conducted in organic farming were studied in the Sahel coast of Tunisia. The types of mulching used for tests are straw mulching, compost mulching, and plastic mulching which were compared with bare soil without mulching (control). The soil characteristics under these different mulching systems were evaluated by soil physical and biological parameters such as penetration resistance at 0-60 cm layer, microbial biomass, organic matter, and water content at 0-20 cm layer. Measurements were performed every week for 50 days. The obtained results showed that compost mulching led to a better growth rate and improved the structural and water state of cultivated soil by decreasing its resistance to penetration and increasing its organic matter content. It can be concluded that the "Beldi" organic pepper crop under conservation tillage and compost mulching has presented the best combination thus leading to motivating results such as the positive effects of soil physical properties and microbial biomass on the final crop yield