NavTrack™ : Navigation performance enhancement in degraded reception environments

This product maximizes GPS satellite navigation accuracy, continuity and integrity in challenging environments that include one or more of the following conditions: a) multiple attenuated or blocked signals, b) high dynamics, and c) electrical interference. Under these operational conditions, NavTrack™ supports sub-meter differential accuracies where conventional receivers either fail to navigate at all or experience errors of tens of meters. The key to this performance advantage is the employment of TISI’s patented IDN signal processing technology in the critical carrier tracking functions of the receiver.

The figures above contrast signal processing in a conventional receiver with a NavTrack™ based receiver with IDN technology. The conventional structure is built around a set of decoupled tracking loops, one for each satellite. Signal flow in each loop begins with the correlator bank,  where spread spectrum codes are correlated against the incoming GPS signals. At the completion of each correlation interval, the I and Q correlator outputs are passed to local code and carrier detectors. In this detection process, current misalignments between local and incoming signals are estimated. Unfortunately, in blockage, spoofing, strong multipath, and  jamming,  a degradation of these individual parameter estimates is inevitable, causing individual channels to break down.  In mitigating the problems associated with the conventional loops and error detectors, TISI reformulated the GPS reception problem, casting it into the proper framework of non-linear vector waveform estimation. From this perspective, we see that the line-of-sight processes to be tracked in the multi-satellite context are highly correlated due to vehicle motion and receiver clock drift. In the optimal receiver structure, therefore, the inter-satellite line-of-sight correlations are utilized in performing the non-linear parameter extractions across all satellites in the system.

In a conventional receiver, as more satellites become available the tracking performance on each satellite fails to improve. Consequently, signal outages immediately inflict tracking damage on attenuated satellites, irrespective of the number of satellites available. By contrast, the NavTrack™ processor employs its central estimator and other satellites to prevent tracking damage. The NavTrack™ receiver uses the raw correlator data from each satellite to update the parameter estimates and tracking for all satellites. Inherently, the NavTrack™ I/Q optimal combining technique utilizes satellite geometry and ephemeris data within the tracking process. Since navigation related data is inherent to the tracking function, the underlying process is called Integrated Demodulation/Navigation. The papers section gives additional details of system implementation and advantages across a variety of application areas.

TISI is working with established receiver manufacturers in bringing its NavTrack™ technology to high priority civilian and military GPS market segments. In support of these efforts, TISI has developed a variety of software and hardware development tools that are further discussed in the Products section.

Following the execution of a two-way non-disclosure agreement,  the embedding, licensing, and royalty arrangements are typically established. The embedding agreement establishes milestones and deliverables for both parties aimed at implementing NavTrack™ functions into the host GPS receiver system. Associated with the embedding processes is technology licensing which allows for the production and sale of NavTrack™ enhanced units into one or more specified market segments. In some circumstances, this may be negotiated as an exclusive licensing agreement.

TISI can also work with an electronics manufacturer to develop a complete GPS receiver design. Generally, the basis of such an approach is built around an existing GPS chip set and CPU,  with TISI’s contribution involving receiver software design, software development, and integration.

Markets

TISI has implemented civilian and military receivers (in both unaided and aided configurations) in establishing reference platforms for the licensing and co-development of next-generation receiver products. TAGR, TISI Advanced GPS Receiver, is a C/A code unit for non-military applications, while TAGR-M is a P/Y code unit meeting the needs of the military. These units are further discussed in the Products section. Civilian and military market opportunities for NavTrack™ are discussed below.