With businesses, governments, and individuals increasingly dependent on the Internet, understanding its reliability is more important than ever. Network outages vary in scope and cause, from the intentional shutdown of the Egyptian Internet in February 2011, to outages caused by the effects of March 2011 earthquakes on undersea cables entering Japan, to the thousands of small, daily outages cau...

In this paper, we propose a novel positioning solution for land vehicles which is highly reliable and cost-efficient. The proposed positioning system fuses information from the MEMS-based reduced inertial sensor system (RISS) which consists of one vertical gyroscope and two horizontal accelerometers, low-cost GPS, and supplementary sensors and sources. First, pitch and roll angle are accurately...

This document describes our analysis of Internet outages during the October 2012 Hurricane Sandy. We assess network reliability by pinging a sample of networks and observing those that respond and then stop responding. While there are always occasional network outages, we see that the outage rate in U.S. networks doubled when the hurricane made landfall, then took about four days to recover. We...

Electricity is cited as one of the biggest impediments to firm growth in developing countries. In the World Bank Enterprise Survey (2006), 35.2% of Indian firms list electricity as the single biggest obstacle to business and report that power outages result in losses equivalent to 6.6% of annual sales. However, some businesses can adjust their means of production to cope with electricity shorta...

When power grids are heavily stressed with a bulk power transfer, it is useful to have a fast indication of the increased stress when multiple line outages occur. Reducing the bulk power transfer when the outages are severe could forestall further cascading of the outages. We show that synchrophasor measurements of voltage angles at all the area tie lines can be used to indicate the severity of...

The precise point positioning service on B2b signal (PPP-B2b) is a real-time decimeter-level provided by the BeiDou-3 Global Navigation Satellite System (BDS-3). provides users with high-precision orbit and clock corrections through geostationary (GEO) satellites, which means that PPP-B2b would be unusable if GEO satellites were blocked. In this study, performance of results during outages are ...

Natural and anthropogenic hazards are frequently responsible for disaster events, leading to damaged physical infrastructure, which can result in loss of electrical power for affected locations. Remotely-sensed, nighttime satellite imagery from the Suomi National Polar-orbiting Partnership (Suomi-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB) can monitor power outag...

The Wide Area Augmentation System (WAAS) became operational on July 10, 2003. Currently this system provides en-route through non-precision approach guidance. Further, the signals are capable of providing vertical guidance to bring an aircraft within 250 feet of the ground. WAAS offers significant benefit to both aviation and non-aviation users. However, the vertical guidance availability is vu...

In ultra-tight GPS/INS integration, a Doppler signal derived from INS navigation data and GPS satellite ephemeris is integrated with the receiver tracking loops to remove the dynamics from the GPS signal. It is well known that this integration architecture provides several advantages such as improved S/N ratio, better ‘immunity’ to interference and jamming signals, lower order tracking loops ev...

BACKGROUND Gavi recommends solar refrigerators for vaccine storage in areas with less than eight hours of electricity per day, and WHO guidelines are more conservative. The question remains: Can solar refrigerators provide value where electrical outages are less frequent? METHODS Using a HERMES-generated computational model of the Mozambique routine immunization supply chain, we simulated the...