A deeply integrated adaptive GPS-based navigator with extended range code tracking

Abstract

This paper presents a new approach to GPS-based navigation which offers significant improvement in antijam capability over traditional designs.The algorithms may be implemented at low cost in software in existing and future GPS receivers using, as inputs, postcorrelation I and Q data and, optionally, raw data from other sensors. Traditional systems are not optimal at high jammer-to-signal (J/S) ratios as a consequence of modular design, use of traditional fixed-gain or gainscheduled tracking loops, and use of artificial moding logic. The approach described here employs a nonlinear filter that operates efficiently at all J/S levels. Filter gains continuously adapt to changes in the J/S environment, and the error covariance propagation is driven directly by measurements to enhance robustness under high jamming and dynamics conditions. Extended-range correlation may be optionally included to increase the code tracking loss-of-lock threshold under high jamming scenarios. Computational complexity is comparable to an extended Kalman filter.Results of hardware-in-the-loop simulations are presented which demonstrate improvements of 15 dB or more in antijam capability relative to traditional designs.

Multi-modal and inertial sensor solutions for navigation-type factor graphs

“…Since Kalman filters assume that all process inputs and observational measurements are statistically independent, the tightly coupled scheme directly predicts and measures individual satellite time-of-flight range measurements in one centralized Kalman filter [229]. The deeply coupled system, Gustafson et al [80], establishes bi-directional data fusion by using the inertial solution to predict where GPS correlator tracking loops should find satellite ranging signals.…”

Navigation sensors and systems in GNSS degraded and denied environments

“…9). [23][24][25][26] In this approach, the problem is formulated directly as an estimation problem in which the optimum (minimum-variance) solution is sought for each component of the multidimensional navigation state vector. By formulating the problem in this manner, the navigation algorithms are derived directly from the assumed dynamical models, measurement models, and noise models.…”

Unified approach to ultra-tightly-coupled GPS/INS integrated navigation system

“…IEEE ABSS has been one of!be co-spcIDI01'8 of this coa1ereace for many yem. [3,4]. Among mem, mc lUUtIC:lY-CUUPlW IiYIiICW lli wc simplest and cann ot give integrated navigation solutions when the number of satellites in view is less than four.…”

“…The ultra-tightly-coupled system has a highly complex integration Ka1man filter which includes the code and carr ier tracking loops and the output of the SDINS (Strap-Down INS) directly derives replica signal generators. We know that the ultra-tightly-coupled system provides highly accurate navigation outputs with strong anti-jamm ing capability [3,4]. Other sensors such as vision sensor [5,6], RFID (Radio Frequency IDentification) [7], altimeter [8], atti tude output from attitude determinati on GPS [9] and differentiated carri er-phase output from GPS [10] are sometimes integrated with INS and/or GPSIINS.…”

“…Many ultra-tightly-coupled GPSlINS systems can be found in literature [2,11,12]. Horslund and Hooker [2] proposed an ultra-tigh t ly-coupled system which uses a code discriminato r and a carr ier discriminator in order to generate input to the integration Ka1man filter.…”