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14
New Analytical Models and Probability Density Functions for Fading in Wireless Communication
 IEEE Transactions on Communications
, 2002
"... Abstract—This paper presents new envelope probability density functions (pdfs) that describe smallscale, local area fading experienced by narrowband wireless receivers. The paper also develops novel pdfs that describe the local area fading of two specular multipath components in the presence of ..."
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Abstract—This paper presents new envelope probability density functions (pdfs) that describe smallscale, local area fading experienced by narrowband wireless receivers. The paper also develops novel pdfs that describe the local area fading of two specular multipath components in the presence of other diffusely propagating waves. These pdfs are studied in the context of classical fading pdfs such as the Rayleigh, Rician, and other distributions. Index Terms—Envelope detection, fading channels, mobile communications, multipath channels, propagation, scattering. I.
Efficient BER Analysis of OFDM System over Nakagamim Fading Channel 1 Mukesh Kumar Mishra,
"... In this paper, we present an efficient technique for the BER of OFDM system over Nakagami–m fading channels, using well known characteristics function based analysis approach. The average BER expressed in terms of the higher transcendental function such as the confluent hyper geometric functions. Ou ..."
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In this paper, we present an efficient technique for the BER of OFDM system over Nakagami–m fading channels, using well known characteristics function based analysis approach. The average BER expressed in terms of the higher transcendental function such as the confluent hyper geometric functions. Our numerical results show that depending on the number of channel taps, the BER performance may degrade with increasing values of Nakagami–m fading parameters.
Characterization of Spectral Density of Wind Farm Power Output
"... Abstract — In this work, the power oscillations during continuous operation of a whole wind farm and a single turbine are characterized for timescales in the range of minutes to fractions of seconds. A stochastic model is derived in time and frequency domains to link the overall behavior of a large ..."
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Abstract — In this work, the power oscillations during continuous operation of a whole wind farm and a single turbine are characterized for timescales in the range of minutes to fractions of seconds. A stochastic model is derived in time and frequency domains to link the overall behavior of a large number of wind turbines from the operation of a single turbine. A literature review on experimental data of Power Spectral Densities (PSD) and periodograms (averaged spectrum) of power output from wind turbines and wind farms are presented. The variability of PSD is also studied through spectograms (joint timefrequency domain) Index Terms—wind, flicker, fluctuation, stochastic process. List of acronyms
On the Utility of Laguerre Series for the Envelope PDF in Multipath Fading Channels
"... Abstract — It is well known that multipath fading significantly affects the performance of communication systems. In order to incorporate the impact of this random phenomenon on system analysis and design, in many cases we need to calculate the probability density function (PDF) of the received sign ..."
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Abstract — It is well known that multipath fading significantly affects the performance of communication systems. In order to incorporate the impact of this random phenomenon on system analysis and design, in many cases we need to calculate the probability density function (PDF) of the received signal envelope in multipath fading channels. In this paper, we consider a general multipath fading channel with arbitrary number of paths, where the amplitudes of multipath components are arbitrary correlated positive random variables, independent of phases, whereas the phases are independent and identically distributed random variables with uniform distributions. Since the integral form of the envelope PDF for such a general channel model is too complicated to be used for analytic calculations, we propose two infinite expansions for the PDF, a Laguerre series and a power series. Based on the tight uniform upper bounds on the truncation error of these two infinite series, we show that the Laguerre series is superior to the power series due to the fact that for a fixed number of terms, it yields a smaller truncation error. This Laguerre series with a finite number of terms, which expresses the envelope PDF just in terms of simple polynomialexponential kernels, is particularly useful for mathematical performance prediction of communication systems in those indoor and outdoor multipath propagation environments, where the number of strong multipath components is small.
Performance of MIMO Schemes with Partial Channel Knowledge
"... Multiple antenna techniques are used to enhance wireless links and therefore have been studied extensively. Many practical systems differ from the ideal schemes discussed in the literature. One example is the lack of precise channel information at the transmitter. We evaluate analytically the perfor ..."
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Multiple antenna techniques are used to enhance wireless links and therefore have been studied extensively. Many practical systems differ from the ideal schemes discussed in the literature. One example is the lack of precise channel information at the transmitter. We evaluate analytically the performance of several multiple input multiple output (MIMO) techniques that use partial channel knowledge. Specifically, we analyze schemes which are used in Worldwide Interoperability for Microwave Access (WiMAX) and are also supported by Long Term Evolution (LTE) systems. All the results are supported by simulations.
A ClosedForm Solution for the Distribution of the Sum of Nakagamim Random Phase Vectors
"... Abstract — The distribution of the modulus of the sum of random phase vectors, is of great practical importance in several applications which deal with sums of sinusoidal signals (wireless multipath transmissions, radars, optical communications, etc). In this letter, simple closedform expressions a ..."
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Abstract — The distribution of the modulus of the sum of random phase vectors, is of great practical importance in several applications which deal with sums of sinusoidal signals (wireless multipath transmissions, radars, optical communications, etc). In this letter, simple closedform expressions are presented for the probability density function (PDF), the cumulative distribution function (CDF), the moment generating function (MGF) and the moments of the envelope distribution of the sum of L nonidentical random Nakagamim phase vectors with integer fading parameters. Moreover, the average over this distribution of the Gaussian Qfunction and of the squared Qfunction, are also presented in closedform. Index Terms — Nakagamim fading channels, sum of random phase vectors, selective fading, Gaussian Qfunction, OFDM, coherent modulation.
Leveraging Deliberately Generated Interferences for Multisensor Wireless RF Power Transmission
"... Abstract—Wireless RF power transmission promises batteryless, resilient, and perpetual wireless sensor networks. Through the action of controllable Energy Transmitters (ETs) that operate atadistance, the sensors can be recharged by harvesting the radiated RF energy. However, both the charging ra ..."
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Abstract—Wireless RF power transmission promises batteryless, resilient, and perpetual wireless sensor networks. Through the action of controllable Energy Transmitters (ETs) that operate atadistance, the sensors can be recharged by harvesting the radiated RF energy. However, both the charging rate and effective charging range of the ETs are limited, and thus multiple ETs are required to cover large areas. While this action increases the amount of wireless energy injected into the network, there are certain areas where the RF energy combines destructively. To address this problem, we propose a dutycycled randomphase multiple access (DRAMA). Nonintuitively, our approach relies on deliberately generating random interferences, both destructive and constructive, at the destination nodes. We demonstrate that DRAMA optimizes the power conversion efficiency, and the total amount of energy harvested. Through realtestbed experiments, we prove that our proposed scheme provides significant advantages over the current state of the art in our considered scenario, as it requires up to 70 % less input RF power to recharge the energy buffer of the sensor in the same time. I.
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"... Abstract — In this paper, 1 a new distribution, named POCA, is introduced for modeling envelope fluctuations due to fast fading in indoor environments. The main motivation has been the small number of scatterers in those environments, which makes the central limit theorem invalid for inphase and qu ..."
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Abstract — In this paper, 1 a new distribution, named POCA, is introduced for modeling envelope fluctuations due to fast fading in indoor environments. The main motivation has been the small number of scatterers in those environments, which makes the central limit theorem invalid for inphase and quadrature components. Hence they are no longer Gaussian and envelope is not Rayleighdistributed. POCA, the new envelope distribution, 1 is obtained by assuming t distribution for inphase and quadrature components. In this comment, first a short summary of three possible approaches for deriving the envelope distribution for indoor channels, where the number of scatterers is usually small, has been provided. Thereafter, based on various detailed theoretical considerations and also measurement results, 1 the deficiency of POCA for prediction of rapid envelope variations in indoor channels has been demonstrated. Having the number of scatterers large is the main assumption in modeling the envelope probability density function (PDF) for fast fading (or local fading, if spatial variations are concerned instead of temporal fluctuations). Whenever other conditions of central limit theorem (CLT), like independence of multipath components received from scatterers, etc. are met, the inphase (I) and quadrature (Q) components of the received signal become Gaussian variables. In
Tri T. Ha Approved for public release; distribution is unlimitedREPORT DOCUMENTATION PAGE Form Approved OMB No. 0704
, 2001
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