JPL's Wireless Communication Reference Website

Chapter: Wireless Propagation Channels

Radio Propagation Models

Mobile communication is burdened with particular propagation complications, making reliable wireless communication more difficult than fixed communication between and carefully positioned antennas. The antenna height at a mobile terminal is usually very small, typically less than a few meters. Hence, the antenna is expected to have very little 'clearance', so obstacles and reflecting surfaces in the vicinity of the antenna have a substantial influence on the characteristics of the propagation path. Moreover, the propagation characteristics change from place to place and, if the terminal moves, from time to time.

Statistical propagation models

In generic system studies, the mobile radio channel is usually evaluated from 'statistical' propagation models: no specific terrain data is considered, and channel parameters are modelled as stochastic variables. Three mutually independent, multiplicative propagation phenomena can usually be distinguished: multipath fading, shadowing and 'large-scale' path loss. The large-scale effects determine a power level averaged over an area of tens or hundreds of metres and therefore called the 'area-mean' power. Shadowing introduces additional fluctuations, so the received local-mean power varies around the area-mean. The term 'local-mean' is used to denote the signal level averaged over a few tens of wave lengths, typically 40 wavelengths. This ensures that the rapid fluctuations of the instantaneous received power due to multipath effects are largely removed.

Radiated powerArea-mean power Local-mean power Instantaneous power
Attenuation due to PathlossFluctuations due to ShadowingFluctuations due to Multipath Fading

 

More pages on propagation

Detailed discussions

Data Bases

We are building a library of measured reference channels. We invite propagation researchers to make measurements available to others. This will allow researchers and designers to make better comparisons with simulations and system proposals by their collegues. Propagation reseachers can compare their measurements with work by others. This CD-ROM provides an excellent opportunity to build such reference library.

 

Bibliography

Slides

The radio wave propagation slide shows lead you through this topic.

Exercises



JPL's Wireless Communication Reference Website 1993, 1995, 1999.