This paper provides simple, exact, new closed-form expressions for the generalized phase crossing rate of Nakagami-m fading channels. Sample numerical results obtained by simulation are presented that validate the formulations developed here. A special case of this formulation is the Rayleigh case, whose result agrees with that obtained elsewhere in the literature. In passing, several new closed-form results concerning the statistics of the envelope, its in-phase and quadrature components, phase, and their time derivatives are obtained. 相似文献
Exact expressions for the level crossing rate and average fade duration of M-branch equal-gain and maximal-ratio combining systems in a Weibull fading environment are presented. The expressions apply to unbalanced, nonidentical, independent diversity channels. In addition, new closed-form solutions for some special cases are obtained. 相似文献
The Brazilian Solar Resource Atlas CD-ROM is intended to be a tool for solar system design, delivering information that relies on a large interactive database, including, also, a modern device for calculating the solar radiation collected by planes inclined at different tilt angles or tracking the sun around one or two axes. The spatial distribution of the daily solar radiation, monthly and yearly averaged, that hits Brazil is presented in 13 colored maps, together with the methodological procedures used for harmonizing the information and designing the maps. A map containing the location of pyranometric and actinographic terrestrial stations, the information which was used for designing the maps, is also presented. The period of collected data runs from 1978 to 1990. Similarly, the atlas contains 13 colored maps, including daily insolation, monthly and yearly averaged, in addition to the map containing the location of the heliographic stations. The CD-ROM stores a database that includes over 500 stations located in Brazil and on the borders of its neighboring countries. The information is given either as daily, monthly average global solar radiation, or daily, monthly average insolation. A search device is included in the database, allowing to navigate over the maps or to select a desired location. The information may be printed as a report. The CD-ROM also includes a software to perform the following calculations: solar radiation estimates on a fixed plane at any inclination on North-South orientation; estimates of solar radiation collected by a plane tracking the sun about one or two axes; generation of synthetic series based on Markov’s Transition Matrixes. 相似文献
In this paper, we present several important details in the process of legacy code parallelization, mostly related to the problem of maintaining numerical output of a legacy code while obtaining a balanced workload for parallel processing. Since we maintained the non-uniform mesh imposed by the original finite element code, we have to develop a specially designed data distribution among processors so that data restrictions are met in the finite element method. In particular, we introduce a data distribution method that is initially used in shared memory parallel processing and obtain better performance than the previous parallel program version. Besides, this method can be extended to other parallel platforms such as distributed memory parallel computers. We present results including several problems related to performance profiling on different (development and production) parallel platforms. The use of new and old parallel computing architectures leads to different behavior of the same code, which in all cases provides better performance in multiprocessor hardware.
We propose a simple accurate method for generating autocorrelated Nakagami-m envelope sequences. The method allows for arbitrary values of fading parameter and nonisotropic fading scenarios. In essence, Nakagami-m samples are first drawn and then rearranged to match the Nakagami-m autocorrelation. The rearrangement is made in accordance with the rank statistics of an underlying Rayleigh reference sequence with the desired autocorrelation. Examples illustrate the excellent performance of the new method 相似文献
This paper specializes and parameterizes the general result presented elsewhere in the literature in order to introduce, fully characterize, and investigate the Symmetrical /spl eta/-/spl kappa/ Distribution, a general distribution used to describe the statistical variation of the envelope in a fast fading environment. It proposes estimators for the involved parameters and uses field measurements to validate the distribution. In spite of its specialization, the Symmetrical /spl eta/-/spl kappa/ Distribution still includes, as special cases, important distributions such as Rayleigh, Rice, Hoyt, Nakagami-q, and One-Sided Gaussian. The fact that the Symmetrical /spl eta/-/spl kappa/ Distribution has one more parameter than the well-known distributions renders it more flexible. Of course, in situations in which those distributions included in it give good results a better fitting is given by the Symmetrical /spl eta/-/spl kappa/ Distribution. In addition, in many other situations in which these distributions give poor results a good fitting may be found through the Symmetrical /spl eta/-/spl kappa/ Distribution. More specifically, its nonmonomodal feature finds applications in several circumstances, examples of which are given in this paper. 相似文献
This work summarizes recently published information on the solar resource of Brazil. We describe the spatial distribution of solar radiation and its relationship with climatic and geographical conditions. In order to harmonize the information in terms of type of instruments, time recording period and data processing methods, a careful selection of records from the data base was made. Density of recording stations is reasonable in the south, southeast and northeast regions of the country, while in the west center and north regions the density of stations is rather poor. The procedure to elaborate the maps of daily solar radiation, monthly and annual average is described. Consideration of the measuring period of the monthly averages, used to elaborate the contour maps, shows that they meet the requirement that 90% of averages are inside the strip of ±7.5%, centralized on the average of very long period measurements. We present one map with the localization of the recording stations and one annual and 12 monthly contour maps, describing daily solar radiation levels over the whole territory. Spacing among the contour lines is (±2 MJm2 day). Annual average of solar radiation lies within the interval of ((18±2) MJm2 day), except in the northeast region where values higher than (20 MJm2 day) are found. Two regions with levels of (16 MJm2 day) are also observed. The highest monthly average values (24 MJm2 day) are observed in the state of Rio Grande do Sul, southern end of the country, in the summer season (December and January). The lowest values in the country (8 MJm2 day) are observed in June and July (winter in the southern hemisphere), on the extreme south coastline of the same state, Rio Grande do Sul, below 32° south latitude. 相似文献