Next Generation Emergency Call System with Enhanced Indoor Positioning
Creators: Song, Wonsang
Publisher: name: Columbia University
Year: 2014
Subjects: Computer science

description: 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.