A Solution for Internet-Based GPS Assistance Provision

Assisted GPS (A-GPS) is an advancement of the standard satellite positioning GPS concept in which either full or partial set of navigation data is provided to GPS receiver in order to improve satellite positioning signals acquisition and end-user position estimate calculation. In a classical A-GPS concept, GPS almanac is broadcast using private or public wireless communications networks (radio beacons, Radio Data System, etc.). Additionally, a provision of accurate GPS time can be arranged in a way that eliminates the need for calculation of the user clock correction as the fourth un-known in the GPS position calculation process. Here we address the solution for provision of Internet-based GPS assistance, with particular scope given to implementation in location-based services (LBS) development. The presented solution is based on a client-server architecture and data transfer using the mobile Internet. Assuming trusted authorities provide accurate GPS satellite almanac on the Internet, almanac data can be acquired and stored locally by the positioning server on regular basis. During position reporting sessions, either mobile client or positioning server can initiate the procedure for GPS assistance delivery to mobile client, if the case of need is identified. The particular Internet-based GPS assistance solution presented in this article utilises the XML-based protocol (XLRP – XML Location Reporting Protocol) for position reporting, that supports two scenarios for GPS assistance procedure initiation. First, the mobile client can detect problems with satellite signals acquisition and initiate the assistance procedure. On the other hand, the positioning server can detect deterioration in positioning performance and offer GPS assistance to the mobile client. After initial negotiations, stored GPS almanac is sent to the mobile client, where it is transferred to the GPS receiver. Presented solution provides platform-independent means for GPS assistance provision. It is especially suitable for and enhances further the capabilities of LBS core system, allowing LBS solution design with a number of quality-of-service (QoS) levels determined by the quality of positioning assistance.