Abstract-A simple and computationally inexpensive analytical approach to the evaluation of the short-term fading depth dependence on system bandwidth and environment characteristics is proposed. The approach, accounting for the maximum difference in propagation path length and having the Rice factor as a parameter, is derived from fitting simulated data from a model in the literature. Application examples are presented for global system for mobile communications (GSM), universal mobile telecommunications systems (UMTS), high-performance radio local area network (HIPERLAN), and mobile broadband systems (MBS), which give some insight into the fading depth observed under different conditions regarding system bandwidth and environment characteristics. Macro, micro, and picocell environments are considered. In the microcellular environment, the fading depth experienced by UMTS is below the one for GSM by 0.1 to 5.5 dB, while in the picocellular one, the difference between GSM and UMTS is not significant, being almost independent of environment characteristics. When considering HIPERLAN or systems with larger bandwidths, the fading depth, both in micro and picocellular environments, is smaller than the one verified by UMTS; however, there is an increased dependence on environment characteristics. In the macrocellular environment, the fading depth experienced by UMTS is about 6 to 11 dB below the one for GSM. Hence, different short-term fading margins should be considered for each system and working environment.Index Terms-Equivalent received bandwidth, mobile communication systems, Ricean fading, short-term fading, wide-band systems.

With the increasing development of 5G and Body Area Network based systems being implemented in unusual environments, propagation inside metallic structures is a key aspect to characterize propagation effects inside ships and other similar environments, mostly composed of metallic walls. In this paper, indoor propagation inside circular metallic structures is addressed and fast fading statistical distributions parameters are obtained from simulation, being assessed with measurements at 2.45 GHz in a passenger ferry discotheque with an 8 m diameter circular shape. It is observed that, in this kind of environments, second order reflections are particularly relevant due to the walls' high reflective nature. Globally, it is concluded that the Rayleigh distribution can be used to characterize fast fading effects with no significant loss of accuracy compared to the Rice one, since a low value of the Rice parameter is observed, being below 3.1 dB, even under Line-of-Sight conditions. Moreover, it is observed that, from the fast fading viewpoint, the best transmitter position is at the circle center. INDEX TERMS Body area networks, fading characterization, metallic structures, propagation modelling.