Software = EPICS
You can download the user's guide here (pdf document).Een Nederlandse versie van deze gebruikersinformatie kan je hier downloaden (pdf document).
Each environment is composed of different obstacles. To be able to calculate the received power or signal in a point or a trajectory of points in this environment, we have to take into account some electromagnetic phenomena such as penetrations, reflections, diffractions, ... and combinations of those phenomena.
For this purpose the program EPICS (Enhanced Propagation for Indoor Communication Systems) was developed by the propagation group of Telemic. By using this program, one is able to predict the amplitude of the received signal, the delay times of both carrier wave and modulation signal at certain places in the environment. Several electromagnetic phenomena are taken into account:
- direct ray taken into account the penetration through the obstructing walls; if the path is obstructed by a perfectly conducting plane, there will be no direct ray even though it is calculated to compare the current situation with a situation where there would be a direct ray
- penetration(s) through non perfectly conducting walls
- direct and diffuse reflections (up to 3 consecutive reflections are taken into account)
- diffractions (up to 2 consecutive diffractions are taken into account, using "slope-diffraction" when the polarization of the signal is parallel to the diffracting edges)
- combinations of diffraction and reflection or vice versa
Especially the diffractions and reflections will cause some adverse effects on the precision of indication of some navigation systems (ILS in air traffic, RDF in sea traffic). We can use this program to predict the maximal errors on such systems.
There are three important input files:
- Geometry of the problem, i.e. all obstacles represented by block shaped obstacles (or combination of blocks for more complex obstacles) with the properties of the "walls" (relative permittivity, loss tangent and thickness). For perfectly conducting planes the loss tangent is equal to or greater then 1.E+8; for non existing planes three zeroes have to be entered. This file also contains the position of the transmitting antenna.
- Antenna file (both transmitting and receiving antenna) with the antenna properties such as type of antenna (dipole or raster of dipoles, horn or microstrip antenna), dimensions of the antenna, transmitted power, position, ...
- Trajectory file for the receiving antenna.
If the program is run for a single receiving point, there is a possibility the program is run for a single receiving point, there is a possibility in the software to generate VRML (Virtual Reality Modeling Language) files. To do this you have to answer "yes" (by typing 1) to the question "Do you want the detailed information about all separate rays? (0:no, 1:yes)". Those VRML files allow the different rays between transmitter (tx) and receiver (rx) to be presented within the environment like shown in Fig. 1.
Fig.1: an example of a VRML output
If the trajectory contains more than one receiving point, the output files contains the received power (electric field components if no receiving antenna was used) which can be introduced to "Matlab" very easily.
Example of simulations/measurements done at Telemic
Fig. 2: Floor plan and comparization between measurements and simulations (no furniture)
The big difference between simulated and measured signal at about 12-13m along the trajectory simulated and measured signal at about 12-13m along the trajectory (horizontal axis) is due to the presence of metallic closets that were not introduced to the simulation.
Maintained by: Emmanuel Van Lil