Assistance, channel, and networking models for A-GPS simulators, and extensions

Huang, Grant
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The U.S. Global Positioning System (GPS) has an established reputation as a robust global technology allowing users to determine their locations using receivers incorporated in various devices including cell phones, PDAs, and watches. While GPS works well in open sky environments, location finding in weak-signal conditions, such as urban canyons and indoors, is challenging and has been the subject of extensive research. Assisted-GPS (A-GPS) is one of the concepts that help receivers acquire weaker signals by exploiting assistance data received from wireless networks, such as orbital parameters, and coarse time and location references. A-GPS is currently standardized technology in cellular communication since it evolved as a natural integration of GPS and wireless communication. Receiver technology developers work on more sensitive algorithms for enabling positioning in weak signal environments and typically rely on signal simulators for testing real-world scenarios. As the terrestrial assistance data channel becomes a foundational link for A-GPS, the statistical modeling of information delivery delays should be addressed for more adequate simulations as channel delays affect receiver operations. In particular, delays contribute to receiver response typically defined as a Time-to-First-Fix (TTFF). The main aspect of the dissertation is to study A-GPS channels by (a) developing a testbed for A-GPS simulation that includes a conventional GPS simulator integrated with an advanced channel model simulator and assistance data delivery over the Internet accessed through wireless links; (b) using the testbed to suggest channel delay measurement methodology; (c) conducting channel measurement campaigns and collecting representative data; and (d) proposing channel models that can be incorporated in A-GPS simulators for generating more realistic assistance communication scenarios for receiver testing. Different from conventional approaches, this dissertation promotes measurements of complete cycle delays including physical propagation and network delays due to data losses. It makes proposed methodology broader and applicable for other communication technologies. A case study of network channel delay modeling is conducted for Power Line Communications (PLC), which is also sensitive to delays in interactive applications (e.g. videoconferencing, remote control systems, online games). PLC emerged as a competitive technology for indoor broadband communications exploiting the existing power line infrastructure for data transmissions. The proposed network channel delay models are essentially based on testbeds for conducting measurement campaigns. The last aspect of the dissertation is the accessibility of testbed platforms for education, training, and resource sharing. Broader access to unique testbeds and experimentation labs in general is an essential component of engineering research, collaboration, and learning. However, high equipment and maintenance costs constrain experimentation infrastructure. Software simulators, based on mathematical models, address this problem to some extent, but interaction with real systems provides a richer and more authentic experience and is often the only available choice. This dissertation presents a recent initiative on designing a remote experimentation platform named eComLab for radio-communication enabling broader access. It addresses two goals: sharing testbeds for research needs and allowing practical educational lab offerings using limited equipment resources.

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Assisted-GPS, MS-based, Network delays, Power line communications, Remote experimentation platform, Secure user plane location, MS-assisted, A-GPS, SUPL
Electrical and Computer Engineering