For mobile communication system in an urban area, an accurate prediction model is important for site planning in order to reduce the amount of optimization done by trial and error. This paper presents the use of 3D ray tracing method to estimate the level of received power inside a university campus with 80 buildings in an area of 1.1 km² with UMTS base stations operating at 2162.6 MHz on the rooftop of the buildings, in order to determine the optimum placement of transmitting antennas with fewer infrastructures, while maintaining a good coverage, numerous simulations were conducted and the results were analyzed. The simulation result show a good coverage of 83.2% above the threshold, thus demonstrate the design effectiveness.