Update - RF Propagation
I have made some good progress towards simulating the propagation of
radio waves in urban environments. Here are some of the
Model Acquisition and
I acquired some RF propagation measurement data collected in Munich
Germany, including: a building database, collection routes, and signal
strength measurement values along the routes. The building
database was not in a standard format, and so I had to write some
custom code to convert the data into a standard .obj file format.
Below is a rendered image of the resulting building data.
Note the cathedral on the right-hand side of the image.
All of the buildings are just extrusions to a certain height
for a given polygon footprint. I am ignoring ground elevation
changes initially, and assuming the ground is a flat plane.
Later I hope to incorporate terrain for better results.
I obtained the RESound code used by GAMMA for sound propagation
simulation. It was not trivial to get the correct version of
Visual Studio installed, and get all the settings correct so that
RESound could build and run on my laptop. I also spent some
time learning how to navigate RESound's GUI, and how to use the many
options, and configuration files. In addition I familiarized
myself with the audio ray tracing engine which is a part of RESound.
Munich in RESound
I imported the Munich model into RESound, and created the necessary
source, position, and other configuration files. Several
configurable values had to be tweaked in order to get RESound to work
well for the urban model, including: reflection order, number of rays
cast, and max attenuation distance. The image below shows
several specular reflection paths resulting from tracing a source (red)
and receiver (yellow) in the same open area of the Munich model.
I traced only specular reflection path, as diffraction is
currently not working in the RESound ray tracing code (expected to be
fixed very soon).
The following is another screenshot from the Munich model inside of
RESound, but this time the receiver is further down the street along
the data collection route. Notice that the signal must
reflect at least 4 or 5 times to reach the receiver. Without
diffraction it is difficult to get good results with the receiver
further away, since it becomes more and more difficult to find a
specular path through the city. Diffraction would allow
the rays to diffract over the buildings. I can now obtain a
of propagation paths for a given source and receiver, next I need to
calculate the path loss due to each path.
I have also continued reading papers dealing with urban RF propagation.
There are several interesting methods, including dominant
prediction, which are of interest.
The following is a list of the next steps for this project:
- Determine the propagation
loss along each ray path (assume
initially that all surface interactions cause 6 dB loss)
- Determine the total
propagation loss or mean field strength at a
- Graph, and compare to
- Get diffraction working
- Fine tune simulation
parameters for RF propagation.
- Reduce errors and