Several possible approaches to creating a model for predicting satellite signal levels inside buildings are examined. These models make use of resonant cavity modes and vector ray addition. The cavity mode approach yields inconclusive results because of a problem with uniqueness, there are too many potential modes and no obvious way to decide between them. The ray model uses vector representation. It tracks changes, and combines rays at the receiver. Signal levels are normalized to free space values. An algorithm for the construction of such a model is developed and results are obtained. A three ray model, incorporating LOS, floor, and ceiling reflected rays gives reasonable agreement with experimental data. The types of information needed are the room height, the receiver height, if the receiver is in the vicinity of a window, and the elevation angle of the satellite. This model shows that a user has to move only a small distance to find an area where fading is brought to acceptable levels. / Master of Science