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In this paper, we introduce Pulsar, a wireless time transfer platform that can achieve clock synchronization to better than five nanosecond between indoor or GPS-denied devices. Nanosecond-level clock synchronization is a missing capability for many real-time applications like next-generation wireless systems that leverage spatial multiplexing to improve channel capacity and provide services like...
In this paper, we address the problem of range-based beacon placement given a floor plan to support indoor localization systems. Existing approaches for trilateration require three or more beacons to determine a unique position solution. We show that with prior knowledge of the map and a model of beacon coverage, it is possible to uniquely localize with only two beacons. This not only reduces installation...
In this paper, we present the design and evaluation of a platform that can be used for time synchronization and indoor positioning of mobile devices. The platform uses the Time-Difference-Of-Arrival (TDOA) of multiple ultrasonic chirps broadcast from a network of beacons placed throughout the environment to find an initial location as well as synchronize a receiver’s clock with the infrastructure...
The omnipresence of indoor lighting makes it an ideal vehicle for pervasive communication with mobile devices. In this paper, we present a communication scheme that enables interior ambient LED lighting systems to send data to mobile devices using either cameras or light sensors. By exploiting rolling shutter camera sensors that are common on tablets, laptops and smartphones, it is possible to detect...
We demonstrate a Visual Light Communication (VLC) system [1] that enables LED lighting luminaires to communicate with cameras on mobile devices. Each LED pulses at a frequency above the humanly perceivable flicker threshold where cameras and photodiodes can still detect changes in light intensity. Our modulation scheme supports multiple light sources in a single collision domain, and works for both,...
Time synchronization in wireless sensor networks is important for event ordering and efficient communication scheduling. In this paper, we introduce an external hardwarebased clock tuning circuit that can be used to improve synchronization and significantly reduce clock drift over long periods of time without waking up the host MCU. This is accomplished through two main hardware sub-systems. First,...
In this demonstration, we show an energy measurement system that estimates the energy consumption of individual appliances using a wireless sensor network consisting of contactless electromagnetic field (EMF) sensors deployed near each appliance, and a whole-house power meter [1]. The EMF sensor can detect appliance state transitions within close proximity based on magnetic field fluctuations. Data...
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