Investigation of Massive Mimo Scenarios Involving Rooftop Propagation by Bidirectional Ray-Tracing

Abstract

The average downlink data-rate in massive Multiple Input Multiple Output (MIMO) networks within realistic urban environments is characterized by means of ray-tracing simulations. The links between the receivers and transmitters are mostly established through rooftop propagation, which requires special treatment due to multiple diffractions near the optical boundaries. The bidirectional ray-tracing method is utilized in order to simulate these effects accurately. The average downlink data-rate is also calculated according to an empirical rooftop propagation model and the differences as well as the similarities with the bidirectional ray-tracing results are demonstrated. Additionally, an iterative Shooting and Bouncing Rays (SBR) algorithm, which improves the computational efficiency of the bidirectional ray-tracing, is introduced. The algorithm aims to maximize the number of rays, which contribute to the result, by setting specific launch directions. The results show that noticeable improvements in the computation time are possible.

Comparison of SBR and MLFMM techniques for the computation of RCS of a fighter aircraft

“…However, to reduce the simulation time while maintaining reasonable accuracy, the SBR method, a technique which computes the RCS in the optical regime, has long been developed [12]. SBR employs a combination of geometric optics (GO) and PO techniques, and by combining both methodologies, SBR performs calculations by originating numerous optical ray tubes [13, 14]. Each corner ray of the ray tube is traced using GO where the wave front parameters such as the magnitude, phase, and direction are superimposed on the rays.…”