A SUPL based A-GPS simulator support for indoor positioning
During recent years location technologies have emerged as a research area with many possible applications and potential impacts in wireless communications, surveillance, and military equipment, etc. This is essentially driven by the success of US Global Positioning System (GPS) and the development of other Global Navigation Satellite Systems (GNSS). Conventional GPS receivers are designed to operate in open-sky environments and have difficulty dealing with signal blockage from buildings and foliage which deteriorates their performance in urban canyons, indoors, and underground. This is mainly due to additional attenuations and multipath distortions of satellite signals which are already weakened due to long distance propagation losses.
In recent years, engineers have developed receivers that perform satisfactorily even with severely attenuated signals by providing external assistance such as satellite orbit parameters, reference time and coarse locations. This approach known as Assisted GPS (A-GPS) significantly facilitates the acquisition of satellite signals, relieves the receiver from the data demodulation tasks, and overall increases start-up sensitivity by as much as 25dB when used in combination with massive correlators. A-GPS is one of the standardized technologies for safety applications. US Federal Communication Commission Enhanced 911 (E911) Mandate seeks to improve the effectiveness and reliability of wireless 911 services by providing emergency services personnel with location information that will enable them to dispatch assistance to wireless 911 callers much more quickly.
In A-GPS technology, the assistance data which consists of coarse time, coarse location, ephemeris and almanac data is generated offline and it is transferred to the receivers through communication links. A typical receiver development relies on testing and tuning using GPS simulators. As the A-GPS technology relies on a network involvement for assistance delivery the simulation of A-GPS is very challenging. This thesis provides an approach to overcome the aforementioned limitation and develops A-GPS extension for conventional GPS simulators in accordance to a state-of-the-art standard---Secure User Plane Location (SUPL) protocol. It is a User Plane location protocol which makes use of user data channels such as Internet Protocol (IP) link to enable location based services.
Another research topic in this thesis is a cost-efficient block-correlator algorithm and Labview-based implementation for so-called software GPS receivers. Software GPS receiver (GPS SDR) is a very attractive concept suitable for various hosting platforms. Computational complexity is the main challenge in implementing such receivers as advanced receivers should have hundreds to thousands of correlators. This thesis presents block correlators capable of processing several correlations at a cost of one. The correlators is incorporated in a GPS receiver tracking loop and tested with NI GPS simulator.