Introduction

The wave propagation inside buildings is characterized by multi-path propagation. Empirical models like the Multi Wall Model do not consider propagation phenomena like reflection, wave guiding effects in corridors and diffractions at vertical or horizontal wedges. Ray optical models consider these effects.

There are two ray optical approaches: Ray Launching and Ray Tracing.

Ray Tracing

With this method, the received power at each receiver pixel R is computed independently from other receiver pixels. For the determination of reflected rays, images of the transmitter are determined, i.e. the image of the transmitter (T) relative to the the reflecting plane (T' or T''). The computation time is very high because each pixel is computed individually - but the accuracy is also very high because all relevant objects (also diffraction wedges) are considered.

WinProp offers two Ray Tracing Models:

• 3D Standard Ray Tracing (SRT)

• 3D Intelligent Ray Tracing (IRT)

Click on the links to get more information about the differences between the two ray tracing models.

Schematic figure for Ray Tracing

Ray Launching

In this method, the transmitting angle of the rays will be increased stepwise. After the "launching" from the transmitter the propagation of each ray is computed individually. After an intersection with a reflecting wall, the reflecting ray will be computed and traced further. After an intersection with a wedge, the rays of the diffraction cone will be computed with a given angle increment. Each time a ray intersects the prediction plane, the field strength values are accumulated at this pixel. The summation of the total received power is given by the square root of the added squares from each contribution. The tracing of a ray stops, if a defined number of interactions is reached or if the path loss of the ray is above a certain threshold.

The disadvantages of this method are the constant angle increment between two adjacent rays (so that it is not always sure that the wedges are reached by rays) and the huge number of new rays after each diffraction. Because of this disadvantages, a Ray Launching is not offered by WinProp.

Schematic figure for Ray Launching

Download a brochure with all urban prediction models.

See a comparison between different urban prediction models.

Read more about the 3D Urban Standard Ray Tracing.

Read more about the 3D Urban Intelligent Ray Tracing.

3D SRT

The Standard Ray Tracing works in full 3D mode. No proprocessing of the database is required. More information can be found here.

3D IRT

The Intelligent Ray Tracing is a rigorous 3D model. A preprocessing of the database guarantees very short computation times. More information can be found here.