Ray Tracing for Channel Modelling

The use of ray tracing in computer graphics for modelling in the visible light spectrum is well known. The technique is based on casting a series of ``rays'' of light from a source, and tracing the rays as they reflect off objects in some scene. To produce an image from this series of rays, the surfaces of the lit scene are projected towards a point through an observation plane. The image created on this plane is then displayed on a screen, or other medium, to the user of the system.

A similar technique may be used for radio propagation, where the rays are normal to the surfaces of equal signal power, and lie in the direction of propagation. By creating a number of images that are the result of reflections and diffractions of the electromagnetic waves off surfaces in the environment, and using ray based techniques, the effect of a transmitted signal on a receiver may be determined.

Due to the complexities of modelling a dynamic environment using a ray tracing technique, it is only practical to simulate the fading channel of a mobile system by moving either the transmitter or the receiver around the environment. The results of this process may be presented in terms of the signal power that would be experienced by a receiver moving through this environment, or in a more detailed form showing the multipath nature of the environment, and the changing channel impulse response as the receiver moves around the environment.