Micro-Cellular Path Loss

Propagation models proposed for micro-cellular communication, model path loss with a transition from free-space propagation to groun wave propagation if

d < 4h_r h_t, where d is the distance of the radio link under study, h_r and h_t are the heights of the receiving and transmitting antenna respectively, and

is the wavelength of the transmitted wave.

Various models have been proposed, e.g. a step-wise transition from "20 log d" to "40 log d" at a certain (turnover) distance.

Harley suggested a smooth transition, with

where r is a normalized distance, r_g is the normalized turnover distance, and is the local-mean power (i.e., received power averaged over a few meters to remove to effect of multipath fades). Studies indicate that actual turnover distances are on the order of 800 meters around 2 GHz.
Other models, such as a stepwise transition, have been proposed. Empirical values for the path loss exponents and their intervals of validity have been reported in many papers.

A smooth transition is often considered in theoretical system studies.

Multipath in Micro-Cells

The micro-cellular propagation channel typically is Rician fading: it contains a dominant direct component, with an amplitude determined by path loss, a set of early reflected waves adding (possibly destructively) with the dominant wave, and intersymbol interference caused by the excessively delayed waves, adding incoherently with the dominant wave.

JPL's Wireless Communication Reference Website

Chapter: Wireless Channels Section: Path Loss

Micro-Cellular Path Loss

Multipath in Micro-Cells

JPL's Wireless Communication Reference Website © Jean-Paul M.G. Linnartz, 1993, 1995.

Chapter: Wireless Channels
Section: Path Loss