Light Emitting Diodes (LEDs) are used in consumer electronics, toys, light bulbs, cars, and monitors. With LEDs, it is possible to control light brightness at a frequency much higher than conventional light bulbs: LEDs can be switched on and off at very high rates. As result, LED-based lighting can be used for wireless communication services by modulating the intensity of the emitted light. Further, LEDs can also be used as receivers just like photodiodes. We call this concept Visible Light Communication (VLC) with LED-to-LED networking. Significant research contributions have been achieved by Disney Research in the area of networked systems for VLC. VLC creates opportunities for low-cost, safe, and environmentally friendly wireless communication solutions. We focus on connected toys and light bulb networks. Our work targets a full system design that spans from hardware prototypes to communication protocols, and applications.


  • 5+ Publications, 2 pending patents, 1 SIGGRAPH Etech, several invited talks
  • Project page on DR website: link
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  • The acoustic capabilities (i.e. microphone) and the fast processors of modern smartphones allow for the transmission of data to groups of such devices through the audio channel. We discuss an acoustic data transmission system for broadcast communication to a multitude of smartphones without the need of a radio access point. Acoustic data transmission is particularly attractive in scenarios that involve sound systems (e.g., movie theaters or open-air film festivals). We discuss different techniques to hide data in sound tracks and how to form a microphone array from a collection of smartphones in the same location. Collaborating smartphones share (using their radio interfaces to form an ad hoc network) the received data streams to jointly correct errors. With a testbed of up to four smartphones, we demonstrate how the robustness and reliability of a downlink broadcast via an acoustic communication system can be improved by collaboration between spatially distributed devices. With field tests in different scenarios, we investigate the potential gain of the collaboration in a real environment.


  • 2+ Publications, 1 pending patent, 1 SIGGRAPH Mobile
  • Project page on DR website: link
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  • User localization with mobile devices remains a challenging research problem if the environment or required accuracy exceed what can be supported by satellite navigation (GPS). In this paper, we present a hybrid system that performs real time localization on a mobile device, using the audio signals emitted by nearby loudspeakers. We propose a particle filter-based combination of CRC-based audio watermarking and audio fingerprinting as a hybrid.


  • 1 Publication


  • A novel approach for pairing RFID-enabled devices is introduced and evaluated in this work. Two or more devices are moved simultaneously through the radio field in close proximity of one or more RFID readers. Gesture recognition is applied to identify the movements of the devices, to mark them as a pair. This application is of interest for social networks and game applications in which play patterns with RFID-enabled toys are used to establish virtual friendships. In wireless networking, it can be used for user-friendly association of devices. The approach introduced here works with off-the-shelf passive RFID tags, as it is software-based and does not require hardware or protocol modifications. Every RFID reader constantly seeks for tags, thus, as soon as one tag is in its vicinity, the reader reports the presence of the tag. Such binary information is used to recognize the movement of tags and to pair them, if the gesture patterns match each other. We show via experimental evaluation that this feature can be easily implemented. We determine the required gesture interval duration and characteristics for accurate gesture and matching detection.


  • 1 Publication
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  • Project video: link


  • This work introduces a customized medium access control protocol, called DrxMAC, for resource-constrained radio devices. The protocol is based on a time-slotted communication scheme with a simple automated slot allocation based on device identities. DrxMAC deploys an in-slot listen-before-talk approach to maximize the slot usage when a slot is shared by multiple devices. The objective of our protocol is to minimize the use of the memory footprint and battery consumption. Further, it should be scalable even without support of a network infrastructure. DrxMAC is evaluated with a testbed implementation on Nordic Semiconductor’s nRF24LE1 (nRF24L) radio system on a chip. This system is often used for low-latency, low-throughput communication in consumer electronics such as wearables, wireless keyboards, or game controllers. It has recently been used in a large roll-out of wearable beacon devices that enable new personalized applications in entertainment theme parks. Such theme parks are controlled environments and can serve as model environment for smart cities. We believe that introducing adhoc networking for the wearable devices (as enabled by DrxMAC) will open the path towards new applications not only for theme parks but related applications in smart cities. We argue that our customized protocol approach improves the coverage range of such wearables and outperforms existing state-of-art protocols in terms of resource and energy efficiency. We compare different configurations and existing standard protocols proposed for sensor networks and the Internet-of-Things, and analyze the performance of our DrxMAC testbed implementation with focus on packet delivery ratio, energy consumption, and scalability.


  • 1 Publication
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  • Bluetooth Low Energy (BLE) is a wireless personal area network technology designed to provide low-power connectivity to smartphones and wearable devices. To transmit bidirectional data, devices must first discover each other via broadcasted beacons on one of three predefined advertisement frequency channels, and then start a pairing process. Usually, the pairing process requires manual intervention that might result in undesirable user experiences. If security and privacy requirements allow, communication sessions could be limited to the advertisement channels only, without pairing the devices. Further, the use of only advertisement channels without pairing devices enables scenarios in which different radio systems can also join the communication. For example, the nRF24L01+ radio system can be programmed to communicate using the advertisement channels defined by BLE. This is relevant because the nRF24L01+ radio system is a popular technology for the Internet of Things and for location-based services with wearable devices in smart cities. This paper evaluates a two-way communication protocol between the nRF24L01+ and BLE devices, using only advertisement frames. We show a practical protocol implementation and use an experimental testbed to evaluate its performance. The evaluation shows that it is possible to build a simple and reliable communication protocol that works in both directions.


  • 1 Publication
  • Project page on DR website: link


  • Bluetooth devices are usually grouped in small clusters called personal area networks (PANs), with a central device that handles the communication of the other nodes in a star topology. The population of Bluetooth PANs is limited to 8 devices, but applications often want to involve a larger number of mobile devices. E.g., entertainment theme parks or interactive installations might employ a large number of devices, as long as they are off the-shelf devices, without any hardware modification. In those scenarios, a PAN must be extended to become a low-cost cellular network for consumer products. We explore the design of such a cellular network of Bluetooth nodes. The paper discusses the practical aspects of a wireless control system for a large number of devices and reports the experience obtained from implementing a proof-of-concept system. The prototype implementation is based on Bluetooth dongles, which act as cellular base stations, and Sphero robotic balls, which are low-cost consumer mobile robots. This wireless control system allows the robots to be controlled by a single device; it is modular and scalable, further, it offers handover and localization services typical of common cellular networks.


  • 1 Publication
  • Project page on DR website: link