The next evolutionary step in biological signal monitoring will be enabled by wireless communication. Low power and cost-efficient wireless transceivers are currently being employed for implantable medical devices (IMDs), in addition to military and civilian applications such as monitoring, surveillance, and home automation. The major goal of this paper is to do a thorough and realistic link budget analysis for an implantable wireless transceiver operating in the 3–5 GHz ultrawideband frequency with a link distance of 2 m (which includes 10 mm of brain tissue layer and 1.99 m of air medium), data rate of 100 Mbps with On-Off keying (OOK) modulation, and a minimum receiver sensitivity of −58.01 dBm. The proposed power budget analysis is particularly well suited for distributed brain implant applications as it models the path loss including the tissue layer without compromising the spectrum regulation imposed by the Federal Communications Commission (FCC) for UWB communication.
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Pushing the Physical Limits of IoT Devices with Programmable Metasurfaces
Small, low-cost IoT devices are typically equipped with only a single, low-quality antenna, significantly limiting communication range and link quality. In particular, these antennas are typically linearly polarized and therefore susceptible to polarization mismatch, which can easily cause 10-15 dBm of link loss on communication to and from such devices. In this work, we highlight this under-appreciated issue and propose the augmentation of IoT deployment environments with programmable, RF-sensitive surfaces made of metamaterials.
Our smart meta-surface mitigates polarization mismatch by rotating the polarization of signals that pass through or reflect off the surface. We integrate our metasurface into an IoT network as LLAMA, a Low-power Lattice of Actuated Metasurface Antennas, designed for the pervasively used 2.4 GHz ISM band. We optimize LLAMA’s metasurface design for both low transmission loss and low cost, to facilitate deployment at scale. We then build an end-to-end system that actuates the metasurface structure to optimize for link performance in real time. Our experimental prototype-based evaluation demonstrates gains in link power of up to 15 dBm, and wireless capacity improvements of 100 and 180 Kbit/s/Hz in through-surface and surface-reflective scenarios, respectively, attributable to the polarization rotation properties of LLAMA’s metasurface.
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- NSF-PAR ID:
- 10177065
- Date Published:
- Journal Name:
- Proceedings of the USENIX NSDI Symposium
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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