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 SBIR effort, NAVSYS proposes to develop a design for a GPS Distributed Aperture Processing (GDAP) system which uses composite GPS and intra-network ranging measurements from a network of GPS users to combine the respective satellite signals that they are tracking and allow operation in a degraded environment. We shall develop and demonstrate the algorithms and techniques that will be employed using the GDAP approach to overcome jamming, multipath and signal blockage conditions, using our in-house simulation tools. A design shall also be developed to implement GDAP on a network of Software Defined Radios under the Phase II effort.