Robust Distributed GPS Apertures

The DoD is heavily dependent on the Global Positioning System (GPS) for worldwide military operations. The GPS signal is subject to a variety of potential degradations, such as path loss (e.g., foliated or indoor environments), multipath (e.g., urban canyon or in-building), and interference (intentional or unintentional). There are many military applications where a group of GPS users may operate together in a denied or degraded GPS environment. Using the traditional GPS receiver approach, individual or all users may be denied the ability to navigate in such an environment, even though each user may be intermittently receiving useful satellite signal information. Under this Phase II project, NAVSYS proposes to develop a GPS Distributed Aperture Processing (GDAP) system which uses observations from a network of Software Defined Radios to combine the GPS satellite signals they are tracking with intra-network ranges and TDOA observations from Signals of Opportunity to allow navigation operation in a degraded environment. We shall develop and demonstrate a system using the GDAP approach to overcome GPS jamming, multipath and signal blockage conditions in an urban environment.