ABSTRACT:
Parallel visibility, Fresnel-zones and radio propagation calculation using graphics processing units
Three parallel algorithms were formulated: modified R2 parallel algorithm for calculating visibility (R2-P), algorithm for calculating Fresnel zone clearance (FZC), algorithm for calculating Fresnel zone transverse intersection between the transmitter and the receiver (FZTI). The R2 parallel algorithm was developed based on the established R2 sequential algorithm for computing visibility. Calculation time is reduced from the order of a few minutes to the order of a couple of seconds. This, in practice, means that there is a possibility of interactive work. In addition to the viewshed, Fresnel zone clearance is very useful for planning the radio coverage. The algorithm for each point of the terrain calculates the first clear Fresnel zone. The result is a digital map with the plotted areas of Fresnel zone clearance. This map provides better information about the radio signal than just a calculation of the viewshed. With modifications, such as the introduction of the Friis transmission equation and consideration of the radiation pattern, the algorithm becomes a simple radio propagation model and thus is suitable for the calculation of radio coverage. Calculation of the radio propagation is compared with the measured values on a field for frequencies of 90 MHz (FM), 800 MHz (LTE) and 1800 MHz (LTE). The algorithm for calculating Fresnel zone transverse intersection between the transmitter and the receiver produces an image of Fresnel zones, which represents the mathematical section of all scale cross-sectional Fresnel zones along the transmission path. The result is a visual image that shows the characteristics of the radio link in terms of masking individual Fresnel zones. All three algorithms were implemented as GRASS GIS modules and can be used on any PC.