As the demand of wireless personal communications networks increases, detailed chracteristics of indoor radio propagation in UHF band are required. In this paper, multipath fading characteristics at 1 GHz in an indoor mobil (walking speed) channel are investigated. By using a computer-controlled antenna scanner, signal strength was measured at 1400 points with a quarter wavelength resolution, which forms a two-dimensional fading map. The fading characteristics were found to be mainly dominated by the signals through the LOS path and the reflected paths due to two side-walls and one front-wall. It is analytically shown that middle-scale (over three wavelengths) fading is caused by the reflection from the side-walls, and periodical small-scale (equal to or less than a wavelength) fading is caused by the reflection from the front-wall. A software simulator based on geometric optics was developed in order to predict the measured fades. A modified algorithm for the two-dimensional ray launching technique which removes the necessity of checking the "multiple-counted rays" is presented. Comparison between measurements and predictions shows good agreement highlighting the usefulness of the two-dimensional simulator as a tool for channel design.