Wabot-House Research Laboratory is working on a project that will enable integrating robots into our everyday life. We believe that a "structured environment" (SE) will be one of most important concepts for this project. An SE generally means that objects near people that have some database or intelligence provide certain information to those people. An SE will also assist robot recognition or movement planning. Now, we focus on a global positioning system (GPS), which is a global SE that gives users or robots their positions whenever and wherever they are outdoors all over the world. GPS will strongly support robot self-positioning. However, GPS has the problem that it cannot be used when the robots are indoors. To solve this problem, we experimentally mounted four pseudolites ('pseudo' means imitated and 'lite' means satellite) in our laboratory and developed indoor GPS. The system worked well unless the robot was near the wall, where cycle slip often occurred. To examine the characteristics and reason for cycle slip, we measured the radio-wave environment in the laboratory. The first half of this paper introduces this system. The last reports results and findings about this experiment.