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Theses Doctoral

Next Generation Emergency Call System with Enhanced Indoor Positioning

Song, Wonsang

The emergency call systems in the United States and elsewhere are
undergoing a transition from the PSTN-based legacy system to a new
IP-based system. The new system is referred to as the Next Generation
9-1-1 (NG9-1-1) or NG112 system. We have built a prototype NG9-1-1
system which features media convergence and data integration that are
unavailable in the current emergency calling system.
The most important piece of information in the NG9-1-1 system is the
caller's location. The caller's location is used for routing the call
to the appropriate call center. The emergency responders use the
caller's location to find the caller. Therefore, it is essential to
determine the caller's location as precisely as possible to minimize
delays in emergency response. Delays in response may result in loss
of lives.

When a person makes an emergency call outdoors using a mobile phone,
the Global Positioning System (GPS) can provide the caller's location
accurately. Indoor positioning, however, presents a challenge. GPS
does not generally work indoors because satellite signals do not
penetrate most buildings. Moreover, there is an important difference
between determining location outdoors and indoors. Unlike outdoors,
vertical accuracy is very important in indoor positioning because an
error of few meters will send emergency responders to a different
floor in a building, which may cause a significant delay in reaching
the caller.
This thesis presents a way to augment our NG9-1-1 prototype system
with a new indoor positioning system. The indoor positioning system
focuses on improving the accuracy of vertical location. Our goal is
to provide floor-level accuracy with minimum infrastructure support.
Our approach is to use a user's smartphone to trace her vertical
movement inside buildings. We utilize multiple sensors available in
today's smartphones to enhance positioning accuracy.
This thesis makes three contributions. First, we present a hybrid
architecture for floor localization with emergency calls in mind. The
architecture combines beacon-based infrastructure and sensor-based
dead reckoning, striking a balance between accurately determining a
user's location and minimizing the required infrastructure. Second,
we present the elevator module for tracking a user's movement in an
elevator. The elevator module addresses three core challenges that
make it difficult to accurately derive displacement from acceleration.
Third, we present the stairway module which determines the number of
floors a user has traveled on foot. Unlike previous systems that
track users' foot steps, our stairway module uses a novel landing
counting technique.
Additionally, this thesis presents our work on designing and
implementing an NG9-1-1 prototype system. We first demonstrate how
emergency calls from various call origination devices are identified,
routed to the proper Public Safety Answering Point (PSAP) based on the
caller's location, and terminated by the call taker software at the
PSAP. We then show how text communications such as Instant Messaging
and Short Message Service can be integrated into the NG9-1-1
architecture. We also present GeoPS-PD, a polygon simplification
algorithm designed to improve the performance of location-based
routing. GeoPS-PD reduces the size of a polygon, which represents the
service boundary of a PSAP in the NG9-1-1 system.

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More About This Work

Academic Units
Computer Science
Thesis Advisors
Schulzrinne, Henning G.
Degree
Ph.D., Columbia University
Published Here
July 7, 2014
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