@misc{MSWBX20,
    author = { John Meklenburg and
               Michael Specter and
               Michael Wentz and
               Hari Balakrishnan and
               Anantha Chandrakasan and
               John Cohn and
               Gary Hatke and
               Louise Ivers and
               Ronald Rivest and
               Gerald Jay Sussman and
               Daniel Weitzner},
     title = { {SonicPACT}: An Ultrasonic Ranging Method for the
               {Private Automated Contact Tracing (PACT)} Protocol},
     date = { 2020-11-09 },
     OPTyear = { 2020 },
     OPTmonth = { November 9, },
     url = { https://pact.mit.edu/wp-content/uploads/2020/11/SonicPACT_Final_v2-with-logos-revA.pdf },
     note = { {PACT} Technical Report No. 2 },
     urla = { <a href="https://arxiv.org/abs/2012.04770">arXiv</a> },                                    
     abstract = {
     Throughout the course of the COVID-19 pandemic, several countries have developed and released
     contact tracing and exposure notification smartphone applications (apps) to help slow the spread
     of the disease. To support such apps, Apple and Google have released Exposure Notification
     Application Programming Interfaces (APIs) to infer device (user) proximity using Bluetooth
     Low Energy (BLE) beacons. The Private Automated Contact Tracing (PACT) team has shown
     that accurately estimating the distance between devices using only BLE radio signals
     is challenging. This paper describes the design and implementation of the SonicPACT
     protocol to use near-ultrasonic signals on commodity iOS and Android smartphones to
     estimate distances using time-of-flight measurements. The protocol allows Android and
     iOS devices to inter-operate, augmenting and improving the current exposure notification
     APIs. Our initial experimental results are promising, suggesting that SonicPACT should be
     considered for implementation by Apple and Google. },
}