A mixed ray launching/tracing method for full 3-D UHF propagation modeling and comparison with wide-band measurements

The growth of radio communication services has stimulated interest in ray propagation modeling, particularly in urban areas. The main drawback of these methods is lengthy computation time due to three-dimensional (3-D) space analysis. The model geometrical ray implementation for mobile propagation modeling (GRIMM) presented here splits the 3-D ray construction problem into two successive two-dimensional (2-D) stages without loss of generality compared with brute-force 3-D ray methods. The gain in time and simplicity enables consideration of large areas typical of a cellular environment. The reflections and diffractions (vertical or horizontal) are taken in any order, and their number can be taken large enough to meet convergence. After the description of the model, the results of simulation are compared with a set of 1465 mean power-delay profiles measured over a 30-MHz band at 900 MHz in a cellular environment for mobile positions almost uniformly spread within a 3-km radius from the base station. The model is shown to be very accurate for path-loss prediction with a mean error of about 1 dB and a standard deviation lower than 5 dB. The wide-band evaluation was performed on the delay spread (DS). This parameter was correctly predicted in about 75% of cases.