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.

www.WirelessCommunication.NL

Chapter: Wireless Channels Section: Path Loss

Micro-Cellular Path Loss

Multipath in Micro-Cells

www.WirelessCommunication.NL © Jean-Paul M.G. Linnartz, 1993, 1995.

Chapter: Wireless Channels
Section: Path Loss