Fading distribution

About: Fading distribution is a research topic. Over the lifetime, 5732 publications have been published within this topic receiving 114193 citations.

ANN based Rayleigh multipath fading channel estimation of a MIMO-OFDM system

Abstract: Multiple-Input Multiple-Output (MIMO) technology using Orthogonal Frequency Division Multiplexing (OFDM) together called MIMO-OFDM has emerged as the viable alterative to meet the demands of greater bandwidth and quality of service of the ever expanding mobile communication networks. For MIMO-OFDM systems channel estimation is one of the challenging issues. Statistical characteristics of wireless channels is partially covered by the Rayleigh distribution. It best represents the condition where there are secondary reflections due to high rise structures are always threatening to degrade communication quality. An ANN can be used to provide an estimate of the channel to minimize some of the deficiencies of multi-user transmission under Rayleigh multipath fading. The ANN can be trained to tackle such fading and associated disturbance and improve reception of MIMO-OFDM systems by providing superior Bit Error Rate (BER)s.

Level crossing rate of Nakagami-m fading signal: field trials and validation

Abstract: Field trial measurements are used to validate the level crossing rate formula derived in an exact manner recently for the Nakagami-m signal. The formula reveals an excellent fit to measurements in situations other than those for which the Rice model is more appropriate.

Microwave Radio obstruction fading

Abstract: The occurrence of obstruction fading on line-of-sight microwave radio paths can require tower heights that are substantially larger than those needed for transmission in a normal atmosphere In this paper, we show that the occurrence probability of obstruction fading can be estimated from the probability distribution of positive vertical refractivity gradients The occurrence of positive refractivity gradients is related to general meteorological variables in a companion paper The work summarized is part of a recent effort that has resulted in a new tower-height design method where tower-height requirements are quantitatively determined from transmission performance requirements

Closed-Form Analysis of Equal-Gain Diversity in Wireless Radio Networks

Abstract: This paper deals with the performance of predetection equal-gain combining (EGC) receivers operating over multipath fading plus cochannel interference (CCI) and additive white Gaussian noise channels. The desired components of the received signals are considered to experience independent but not-necessarily identically distributed Nakagami-m fading, while the interferers are subject to independent Rayleigh fading. The analysis is not only limited to equal average fading power interferers, but the case of interferers with distinct average powers is also examined. By following the coherent interference power calculation, novel closed-form expressions for the moments of the EGC output signal-to-interference-plus-noise ratio (SINR) are derived, which are being used to study the performance of the average output SINR. Furthermore, by assuming an interference-limited fading scenario, novel closed-form union performance bounds are derived. More specifically, tight upper bounds for the outage and average symbol error probability for several constant envelope modulation schemes, and lower bounds for the Shannon average spectral efficiency, are provided. Numerical results demonstrate the effect of the number of interferers, the number of the receiver branches, and the severity of fading on the EGC receiver performance. Computer simulations have been also performed to verify the tightness of the proposed bounds and the correctness of the mathematical analysis. It is shown that the performance of cellular radio systems in the uplink is degraded mainly from the first-tier CCI of the adjacent cells

The Rate of Fading in Propagation through a Turbulent Atmosphere

Abstract: Fading rate is defined to be the number of times per minute that the envelope of the received field crosses its median level with a positive slope. This definition of fading rate is equally useful for ionospheric or tropospheric propagation studies. Furthermore, it may be used with equal facility on short transmission paths where the ground wave component of the received field predominates and on the longer transmission paths where the scattered component of the received field predominates. It is shown that this definition of fading rate provides a quantity which is numerically related to the parameters of the propagation medium under certain conditions which are normally satisfied in either ionospheric or tropospheric propagation studies. The pertinent parameters of the propagation medium in beyond-the-horizon transmission are the location and shape of the scattering volume and the turbulent and drift velocities of the scatterers. An extensive discussion is given of the shape of the tropospheric scattering volume for beyond-the-horizon transmission. An analysis is then given of some fading rate data obtained in the National Bureau of Standards tropospheric propagation program in the 92 to 1046 mc range of frequencies on transmission paths 70, 97, 226, and 394 miles in length. Finally an analysis is given for within-the-horizon propagation. In this case it is advantageous to define fading rate as the number of times per minute that the phase of the received field crosses its median level with a positive slope.