Stefan P.  

Algorithms for Signal Drawbacks Mitigation in Fading Environment

Abstract: Signal propagation in the wireless medium is accompanied by various side effects and drawbacks such are multipath fading and shadowing. Mathematical characterization of these complex phenomenons, which describes various types of propagation environments, will be presented. First, various models, already known in the literature, such are: Rayleigh, Ricean, Hoyt, Nakagami-m, Weibull, α-μ, η-μ, and κ-μ fading model, used for the statistical modeling of multipath influence, will be introduced. Then, some of models for statistical modeling of shadowing influence, such are: long-normal and Gamma shadowing model, will be mentioned. Finally, some respect will be paid to composite models, which correspond to the scenario when multipath fading is superimposed on shadowing. Suzuki, Ricean-shadowing and Generalized K composite fading models have been discussed. Further analysis will be extended by introducing correlative fading models, considering exponential, constant and general type of correlation between random processes. Several performance measures related to the wireless communication system design, such are: average signal-to-noise ratio, outage probability, average symbol error probability, amount of fading, level crossing rate and average fade duration, will be defined and mathematically modeled. Basic concepts of several space diversity reception algorithms, such are: maximal ratio combining, equal gain combining, selection combining and switch-and stay combining, will be portrayed also, with emphases put to the reception performance measures evaluation. Necessity and the validity of space diversity reception algorithms usage, from the point of view of multipath fading and CCI influence mitigation, will be shown by first evaluating single-channel receiver performances for few general propagation models and then by presenting performance improvement at the receiver, achieved by appliance of diversity reception algorithms through the standard performance criterions. Also, necessity and validity of the macrodiversity algorithm reception usage, from the point of view of multipath fading and shadowing mitigation through the second order statistical measures at the output of the macrodiversity algorithm receiver, will be considered.