| 1. |
- Varshney, Ambuj, et al.
(författare)
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Coordination of Wireless Sensor Networks using Visible Light
- 2015
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Ingår i: SenSys '15 Proceedings of the 13th ACM Conference on Embedded Networked Sensor Systems. - New York, NY, USA : ACM. - 9781450336314 ; , s. 421-422
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Konferensbidrag (refereegranskat)abstract
- Wireless sensor networks are often deployed indoors where artificial lighting is present. Indoor lighting is increasingly being composed of Light Emitting Diodes (LEDs) that offer the ability to precisely control the intensity and the frequency of the light carrier. This can be used to coordinate wireless sensor networks (WSN). The periodic variations in the light intensity can synchronise the clocks on the sensor nodes, while the ability to modulate the light carrier enables the transmission of control information like channel assignment or transmission schedules.We present Guidelight, a simple mechanism that uses controlled fluctuations in the light intensity to coordinate sensor nodes. Guidelight can wake-up or time synchronise sensor nodes or even send small bits of control information to them. All of these have separate dedicated solutions in WSN. Guidelight aims to provide a single solution to all these problems. Our initial experiments demonstrate the ability of Guidelight to trigger sensor nodes. We demonstrate Guidelight is able to trigger sensor nodes selectively at a mean error of 21 μ s.
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| 2. |
- Varshney, Ambuj, et al.
(författare)
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Directional Transmissions and Receptions for High-throughput Bulk Forwarding in Wireless Sensor Networks
- 2015. - 8
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Ingår i: Proceedings of the 13th ACM Conference on Embedded Networked Sensor Systems (SenSys '15). - New York, NY, USA : ACM. - 9781450336314 ; , s. 351-364
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Konferensbidrag (refereegranskat)abstract
- We present DPT: a wireless sensor network protocol for bulk traffic that uniquely leverages electronically switchable directional (ESD) antennas. Bulk traffic is found in several scenarios and supporting protocols based on standard antenna technology abound. ESD antennas may improve performance in these scenarios; for example, by reducing channel contention as the antenna can steer the radiated energy only towards the intended receivers, and by extending the communication range at no additional energy cost. The corresponding protocol support, however, is largely missing. DPT addresses precisely this issue. First, while the network is quiescent, we collect link metrics across all possible antenna configurations. We use this information to formulate a constraint satisfaction problem (CSP) that allows us to find two multi-hop disjoint paths connecting source and sink, along with the corresponding antenna configurations. Domain-specific heuristics we conceive ameliorate the processing demands in solving the CSP, improving scalability. Second, the routing configuration we obtain is injected back into the network. During the actual bulk transfer, the source funnels data through the two paths by quickly alternating between them. Packet forwarding occurs deterministically at every hop. This allows the source to implicitly "clock" the entire pipeline, sparing the need of proactively synchronizing the transmissions across the two paths. Our results, obtained in a real testbed using 802.15.4-compliant radios and custom ESD antennas we built, indicate that DPT approaches the maximum throughput supported by the link layer, peaking at 21 4 kbit/s in the settings we test.
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| 3. |
- Wei, Bo, et al.
(författare)
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dRTI : Directional Radio Tomographic Imaging
- 2015. - 8
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Ingår i: Proceedings of the 14th International Conference on Information Processing in Sensor Networks (IPSN '15). - New York, NY, USA : ACM. - 9781450334754 ; , s. 166-177
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Konferensbidrag (refereegranskat)abstract
- Radio tomographic imaging (RTI) enables device free localisation of people and objects in many challenging environments and situations. Its basic principle is to detect the changes in the statistics of radio signals due to the radio link obstruction by people or objects. However, the localisation accuracy of RTI suffers from complicated multipath propagation behaviours in radio links. We propose to use inexpensive and energy efficient electronically switched directional (ESD) antennas to improve the quality of radio link behaviour observations, and therefore, the localisation accuracy of RTI. We implement a directional RTI (dRTI) system to understand how directional antennas can be used to improve RTI localisation accuracy. We also study the impact of the choice of antenna directions on the localisation accuracy of dRTI and propose methods to effectively choose informative antenna directions to improve localisation accuracy while reducing overhead. Furthermore, we analyse radio link obstruction performance in both theory and simulation, as well as false positives and false negatives of the obstruction measurements to show the superiority of the directional communication for RTI. We evaluate the performance of dRTI in diverse indoor environments and show that dRTI significantly outperforms the existing RTI localisation methods based on omni-directional antennas.
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