| 1. |
- Varshney, Ambuj, et al.
(författare)
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Judo : Addressing the Energy Asymmetry of Wireless Embedded Systems Through Tunnel Diode based Wireless Transmitters
- 2022
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Ingår i: MobiSys '22. - New York : Association for Computing Machinery (ACM). - 9781450391856 ; , s. 273-286
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Konferensbidrag (refereegranskat)abstract
- The radio transmitter is the most power-consuming component of a wireless embedded system. We present Judo, a radio transmitter that enables power balance between the wireless transmission, sensing, and processing tasks of a wireless embedded system. Judo transmitters leverage the fact that modern radio transceivers offer high receive sensitivity at low power. Therefore, even if the radio transmitter emits a weak signal, the link budget and transmission range will often remain high. With this key insight, we revisit the radio transmitter architecture by dramatically reducing the radiated power and hence the overall power draws. Specifically, Judo transmitter uses a tunnel diode oscillator to integrate the stages of a radio transmitter into a single energy-efficient step. In this step, baseband signals are generated and mixed using peak power below 100 μW. However, we sacrifice stability of tunnel diode oscillator for low-power consumption. We use the injection-locking phenomenon to stabilise the tunnel diode oscillator with an external carrier signal. Based on this novel architecture, we implement a transmitter that supports frequency-shift keying as a modulation scheme. Judo transmits over distances greater than 100 m at a bit rate of 100 kbps. It does so with an emitter device providing the carrier signal, and located at a distance of more than 100 m from Judo transmitter. In terms of critical link metrics, it outperforms the radio transmitters commonly used in wireless embedded systems.
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| 2. |
- Yan, Wenqing, Ph.D. Student, 1994-, et al.
(författare)
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Enabling L3 : Low cost, Low complexity and Low Power Radio Frequency Sensing using Tunnel Diodes
- 2022
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Ingår i: MobiCom '22. - New York : Association for Computing Machinery (ACM). - 9781450391818 ; , s. 913-915
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Konferensbidrag (refereegranskat)abstract
- The past decade has seen a great interest in developing radio frequency sensing technology and its applications. At a basic level, these systems operate by tracking changes in the wireless signal reflected from a physical object. These reflections contain a wealth of information about the object, such as its motion and material. However, existing radio frequency sensing solutions are constrained by the complexity of the deployment and their high power consumption. This is because these systems extract weak reflections in presence of a strong incident signal. This paper introduces a new radio frequency sensing modality that allows tracking of the incident signal and not reflections from the object. This allows us to simplify the receiver and algorithm design significantly. We design the system using tunnel diode oscillators to generate a high-frequency carrier signal at only tens of microwatts of power consumption. The critical contribution that we make is to show that the frequency of the tunnel diode oscillator is sensitive to the physical environment. As an example, we demonstrate that performing simple hand gestures near the tunnel diode oscillator causes notable changes to its frequency. Thus, the receiver tracks the frequency of the carrier signal generated by the tunnel diode oscillator, and not reflections from physical objects. It enables inferring of sensing information using a commodity receiver costing only a few USD. Our system enables radio frequency sensing at low cost, complexity and power.
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