Novel ray-tracing approach for fast calculation of the impulse response on diffuse IR-wireless indoor channels

Abstract

In this paper, a modified Monte Carlo algorithm for the calculation of the impulse response on infrared wireless indoor channels is presented. This work follows a guideline of studies about the infrared wireless diffuse data communications systems. As is well known, the characteristics of the room where the IR diffuse channel is implemented determine some problems in the communication as can be multipath penalty over the maximum band rate or hidden station situations. Classical algorithms require high computational effort to calculate the impulse response in a regular size room. Monte Carlo offers the possibility of validating the assumptions made for these classic algorithms (basically, the lambertian nature of all reflections) with a computational complexity that is decided by the accuracy desired by the user. It is also an structure that can be easily assumed by a parallel computer architecture. In the other hand, its main drawback is that, for a regular sized room, we need to send much more rays than the components that we receive. This is due to the fact that usually rays are not intercepted by the receiver. We have developed a mixed Monte Carlo-Deterministic algorithm which assures that each ray contributes to the final channel response function each time it rebounds with an obstacle. It increases dramatically the number of contributions and reduces, in the same way, the time required for an accurate simulation. Extensive simulation results are presented. They are compared both with other simulation methods and with measured values. We will demonstrate that the method presented here is much faster than Monte Carlo classical simulation schemes. It can be used like a method of simulation itself or as a validation algorithm for other comparative studies of pulse broadening.