Rain Spatial Classification

Method for Classification of Rain Spatial Characteristics

One of the most important characteristic of rain fields taking into account during planning of PMP radio systems in millimeter wave bands is their spatial and temporal non-uniform distribution. To fully describe the influence of the rainstorms on the PMP systems, the site diversity statistics of a system as a whole were investigated. Since the site diversity performance is highly dependent on the actual spatial distribution of the rain rate, based on the outage statistics the sophisticated classification of the rain spatial characteristics is determined. The new rainfall spatial parameter is derived.

Outage Improvements

The motivation to our approach was to offer simpler way to evaluate possibilities of the site diversity employment for specific scenarios instead of exhausting power balance calculations of every potential diversity connection. Using space-time simulations of a point-to-multipoint system in a specific area under specific rain conditions we investigated the behavior of the system as a whole. In order to describe as much accurate as possible influences of rainfalls on the system, an outage improvement probability function has been set as the main specific factor. The outage improvement probability can be defined as the ratio between the successful trials to establish the diversity link and total number of all main link outages. To reach an outage improvement statistic the simulations of the system performance during rain events were performed. The outage improvement statistic dependence on the angle separation and a ratio of the main and diverse link lengths (dmain/ddiv) have been derived for each rain scan. These particular statistics have been associated with more than one million of rain scans.

Rain Spatial Characteristics Classification

The main aim of this part of the thesis was to describe rain spatial distribution by particular parameters. From practical reasons it was necessary to utilize as little as possible parameters. Moreover, these parameters should be in some way linked with the performances of the point-to-multipoint systems utilizing the space diversity.

The result of the analyses is as follows: to derive the parameter cconst the only one parameter fully describing the rain rate spatial distribution is sufficient. The rainfall spatial parameter is expressed as the average area of rain cell considering all the 9 contour levels.


To asses its value for a particular rain scan, first the average areas of rain cell have to be derived for each contour threshold by dividing total rain occupied area by number of rain cells. Thereafter the resulting value of the rainfall spatial parameter can be obtained as the mean value of average rain cell areas for all contour levels. It could be opposed, that more appropriate spatial features of the rain could be used to describe the rain rate distribution. However, the whole process of determination of outage improvement probability would turn to a too difficult task.




Supported by

  • Time-space Simulations of MWS Systems in 42 GHz Band, Czech Science Foundation, grant no. GA102/04/2153, 2004-2006

Selected papers