A strategy is presented for exploiting the frequency stability,
transmit location, and timing information of ambient radio-frequency “signals of opportunity” for the purpose of
navigating in deep urban and indoor environments. The
strategy, referred to as tightly-coupled opportunistic navigation
(TCON), involves a receiver continually searching
for signals from which to extract navigation and timing
information. The receiver begins by characterizing these
signals, whether downloading characterizations from a collaborative
online database or performing characterizations
on-the-fly. Signal observables are subsequently combined
within a central estimator to produce an optimal estimate
of position and time. A simple demonstration of the
TCON strategy focused on timing shows that a TCONenabled
receiver can characterize and use CDMA cellular
signals to correct its local clock variations, allowing it to
coherently integrate GNSS signals beyond 100 seconds.Aerospace Engineering and Engineering Mechanic
