The last decade there has been an enormous expansion in the area of wireless communication. As new services and devices are introduced, and more information is sent between an increasing number of users, more bandwidth is required and the spectrum becomes more limited. To increase capacity in cellular networks, cells can be made smaller and smaller. To be able to plan picocells, such as an indoor environment, in an efficient manner, it is important to have a more detailed understanding about the channel characteristics. Further ways to improve radio communication is to make use of more efficient encoding and receiving techniques, such as spread spectrum. Also when testing new techniques, knowledge about the channel characteristics and limitations are of interest. This thesis models the channel characteristics of an indoor deterministic environment with a simulator using ray tracing techniques. To make the environment as realistic as possible, the physical properties of construction materials are taken into account. The simulator is able to track each individual radio wave, making it possible to calculate interesting parameters such as received power, phase, and direction-of-arrival. The simulator operates in 2D-environments. A lot of work have been done to extend the simulator to a 3D-version, although some problems still remains to be solved.