Research Summary | Technical Focus  | Stanford Leadership

Technical Focus

The Center will focus on major projects with high potential payoffs for society. These projects will blend theory and experiment. They will leverage Stanford’s unique multi-discipline approach to position, navigation and time. They will culminate in a demonstration, and combine to serve our single overall purpose: centimeter accuracy anywhere anytime. Since much of the work will be performed at the Ph.D. level, projects will usually have a multi-year lifespan.

1. New Signals from GPS, Galileo, GLONASS.
   Within the decade, GPS will broadcast three civilian signals rather than the one signal used today. This frequency diversity will reduce our vulnerability to jamming and enable accurate estimation of ionospheric delays by the user equipment. The new European system, Galileo, plans to broadcast four frequencies, and the rejuvenated GLONASS will most certainly have multiple civil frequencies.
   
   
    
2. Inertial and clock technologies.
   Small precision user clocks will be integrated into the navigation system thereby largely eliminating one of the user unknowns. Precision atomic reference mass accelerometers and other new gyro technologies have the potential to dramatically improve satellite-tracking performance by decreasing the required tracking bandwidth.
   
   
   
    
3. Antenna arrays and spatial signal processing.
   Three dimensional beam steering antennas can be employed and integrated into the total solution. These techniques reduce signal power from accidental or malevolent jammers. They also assist users in cities or anywhere the signal obstructions.
   
   
   
    
4. Multidimensional, highly integrated signal processing sensors. Today’s GPS receivers track each satellite signal from a single antenna independently of the others. Our goal is to leverage the over-specified nature of the navigation solution. With Galileo, there may be 20 satellites in view. At the same time, the user need only solve for at most four unknowns – three dimensions of position and one dimension of time. Moreover, these four states have limited dynamics. Consequently, we will integrate satellite tracking with position estimation. In this way, weak satellites can be tracked based on the power in the strong satellites and the information provided by the other sensors. Many benefits will accrue including better operation in obstructed or jammed environments. This technique is called the vector delay lock loop and is the optimal way to integrate the information from the multi-sensor environment we foresee. This integrated processing can utilize the total power from all satellites in view simultaneously instead of attempting to track and acquire the signals one at a time.
    
5. Integrated semiconductor technology. Relevant advances in this area include low power mixed signal design, precision clock references, and MEMS devices. In addition, greater computational capabilities enable so-called software receivers that move an increasing fraction of the processing from hardware to software. Software receivers have greater flexibility with decreases in power and size.
    
   
    
6. Atmospheric and orbital science. Modeling studies of the various atmospheric and ionospheric delay and scintillation phenomena both in equatorial, polar, and other regions has the potential to improve navigation performance.

The Center’s research goals are ambitious. GPS does not work at all underwater. GPS operation indoors is very uncertain, and operation in urban areas is troubled by signal reflections and obstructions. GPS is easily jammed. The Center will seek technology that is low-cost, compact, easy-to-integrate, authenticated, secure, and requiring low power. This equipment will need to operate in difficult navigation environments: indoor, urban canyons, space, remote, mountainous terrain, jungle/foliage, undersea, underground and be resistant to EMI and jamming.

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