A thorough millimeter-wave measurement campaign is carried out in an indoor environment with an aim at characterizing the short-term fading channel behavior. The measurements are conducted in a variety of scenarios, with frequencies ranging from 55 GHz to 65 GHz, in line-of-sight and non-line-of-sight conditions, and combinations of horizontal and vertical polarizations at both transmitter and receiver. A number of fading models are tested, namely Rayleigh, Rice, Nakagami-m, α-μ, κ-μ, η-μ, and α-η-κ-μ. The statistics under analysis are those characterizing the fading amplitude and the frequency selectivity. In particular, the probability density and cumulative distribution functions for the former and level crossing rate per bandwidth unit for the latter are the respective first-and second-order statistics used. To this end, from the experimental data, the parameters of the models are estimated and the corresponding theoretical curves are plotted and compared with the empirical ones. Whereas the required theoretical formulations of the first-order statistics of these models are already well known, those of the second-order statistics as well as these fitting process.

Recent standardization of portions of the millimeter-wave (mm-wave) band for fifth-generation (5G) operation has called for further research on how short-term fading behaves in that unexplored part of the spectrum. With such a target, this paper reports on a thorough measurement campaign conducted in an indoor environment characterized by rich-multipath scattering, a part of a modern building, with floor and ceiling constructed of reinforced concrete over steel plates with wood and plasterboard-paneled walls. Particularly, measurements have been performed in a variety of scenarios, under line-of-sight (LoS) and non-line-of-sight (nLoS) conditions, for a wide range of frequencies, namely from 25 to 40 GHz- a span of 15 GHz- therefore, including 26, 28 and 39 GHz. First and second order statistics of representative fading models, namely Rayleigh, Rice, Nakagami, folded normal, α- μ, η- μ, κ- μ, and α- η- κ- μ have been investigated. The metrics used in the analysis were the normalized mean square error (NMSE), the Kolmogorov-Smirnov (KS), and the Akaike information criterion (AIC). Additionally, the study of the κ- μ model is advanced, in which new, exact, simple closed-form expressions for probability density function, cumulative distribution function, and level crossing rate are derived for some particular cases, namely for μ = n+ 1/2 in which n ∈ \mathbb N.

The aim of this paper is twofold: 1) to show that the newly proposed α-η-κ-μ complex fading model provides the best fit for the envelope of a signal propagated in a millimeter wave in a given scenario and 2) to further improve the knowledge of this fading model through the derivation of some of its higher order statistics. The fitting process is carried out based on some field measurements campaigns conducted by independent research groups at the 28 GHz band as well as at the 60 GHz band available elsewhere in the literature. The higher order statistics concern the time derivative of the whole α-η-κ-μ process with a view at obtaining important metrics, such as level crossing rate, average fade duration, and phase crossing rate. An extensive number of exact formulations for the corresponding statistics are derived. Through a small sample of plots, the flexibility provided by the physically based model becomes evident, showing its potential to be used in a variety of propagation scenarios.

This letter introduces a novel binary digital modulation scheme called oodn modulation, in which bit 1 is transmitted as a digital complex awgn, while bit 0 is represented by silence. Closed-form expressions for the bep under awgn channels are derived, and the analysis is extended to fading environments modeled by the κ-μ distribution, which encompasses both los and nlos conditions. The performance of oodn is evaluated and compared against conventional binary modulations, including bpsk and ook, and also with the recently proposed noisemod, demonstrating excellent bep performance. All analytical results are validated through Monte Carlo simulations, including scenarios based on practical mmwave channel models. The proposed technique represents a promising solution for low-complexity and ultra-low-power transceivers.

This work compares the statistical fitting performance of the fading models α-μ, Nakagami-Lognormal, Generalized-K, and Fisher-Snedecor, to field measurements conducted at 1.8 GHz in a composite fading environment. The aim is to investigate whether a substantially easily computable, simpler model, namely α-μ, can be used instead of more intricate ones, namely, Nakagami-Lognormal, Generalized-K, and Fisher-Snedecor, the former first explicitly derived for that scenario and the latter three obtained as an approximation of it. The comparison uses metrics such as normalized mean square error (NMSE) and the modified Kolmogorov-Smirnov test (modified K-S). In overwhelmed cases, α-μ. outperformed all the other models or, otherwise, gave a comparable performance.