Wider Adoption of Radio Interferometric Positioning in Wireless Sensor Applications
Self-location awareness of sensors plays a significant role in many Wireless Sensor
Network (WSN) applications such as sensor network-based counter-sniper systems, habitat
monitoring in the wild, and energy-efficient surveillance system. Positioning using
Received Signal Strength (RSS) and trilateration are suitable for sensor networks but
can only provide coarse location information. ... read moreOn the other hands, methods relying on
Time Difference of Arrival (TDOA), Time of Flight (TOF), and Angle of Arrival (AOA) are
more accurate than the RSS methods but need expensive specialized hardware. Radio
Interferometric Positioning Systems (RIPS) provides centimeter accuracy, but is still
not widely adopted in wireless sensor applications due to the limited set of suitable
radio platforms. As a result, sensor localization remains a challenging problem. The
objective of this dissertation is to decrease hardware requirements for Radio
Interferometric Positioning while providing sufficient positioning accuracy so that this
technology can be realized on a broader set of radio platforms and be widely adopted in
a variety of wireless sensor applications. The basic idea behind RIPS is to calculate
the position from the phase of an interference signal created by two unmodulated signals
at slightly different frequencies. The original RIPS has stringent hardware requirements
on the radio platform, including fine frequency tuning, 2-Frequency-Shift-Keying (2-FSK)
modulation, and continuous RSS reporting. As a result, only the discontinued Mica2 with
CC1000 has been proven to support RIPS so far. As a successor of RIPS, Stochastic Radio
Interferometric Positioning System (SRIPS) shortens the measurement time of RIPS at a
price of decreasing the positioning accuracy from 3 cm to 30 cm. Many current radio
platforms cannot support RIPS/SRIPS because of removal of hardware features needed by
these methods, such as the replacement of 2-FSK modulation with Direct Sequence Spread
Spectrum Offset-Quadrature Phase Shift Keying (DSSS O-QPSK) modulation. Hence, we
introduce Stochastic Radio Interferometric Positioning System with Modulated Signals
(SRIPS-MS) to realize Radio Interferometric Positioning on a broader set of radio
platforms for a wider adoption of Radio Interferometric Positioning in wireless sensor
applications, by altering FSK modulation phase to DSSS O-QPSK modulation, with measured
positioning accuracy as 25 cm. In the first part of this dissertation, we present
mathematical models of SRIPS-MS based on a signal propagation model in free space and
signal processing principles to circumvent the hardware restriction problem in the
original RIPS. We perform a theoretical demonstration of the proposed SRIPS-MS by
deriving the equation between the phase offset and the distance relationship. In the
second part of this dissertation, extensive Matlab simulations are performed to study
the performance of SRIPS-MS with different parameter settings in a variety of scenarios.
DSSS O-QPSK packet-related parameters are carefully examined and the parameter settings
yielding the most accurate phase offsets are chosen for hardware experiments of
SRIPS-MS. The third part of this dissertation focuses on designing and implementing a
hardware prototype of SRIPS-MS based on CC2420. Experiments in a 20 m × 20 m
experimental set-up show that SRIPS-MS CC2420 implementation provides better accuracy
than SRIPS (from 25 cm to 30 cm).
Thesis (Ph.D.)--Tufts University, 2018.
Submitted to the Dept. of Electrical Engineering.
Advisor: Chorng Hwa Chang.
Committee: Alva Couch, Byung Guk Kim, and Mohammed Afsar.
Keyword: Computer engineering.read less