Polymorphic radios

Abstract

Duty-cycling has emerged as the predominant method for optimizing power consumption of low-power radios, particularly for sensors that transmit sporadically in small bursts. But duty-cycling is a poor fit for applications involving highrate sensor data from wearable sensors such as IMUs, microphones, and imagers that need to stream data to the cloud to execute sophisticated machine learning models.We argue that there is significant room to optimize lowpower radios if we can take advantage of channel dynamics in short-range settings. However, we face challenges in designing radios that are efficient at power levels between µWs and mWs to take advantage of periods of good signal strength and nimble to deal with highly dynamic channels resulting from body movements. To achieve this, we propose radio polymorphism, a radio architecture with tightly integrated passive and active components that allows us to turn high channel dynamics to our advantage. We leverage passive modes in myriad ways within the network stack, from minimizing data transfer and control overheads to improving rate selection and enabling channel-aware opportunistic transmission. We instantiate our design in a full hardwaresoftware prototype, Morpho, and demonstrate up to an order of improvement in efficiency across diverse scenarios and applications.

Demo

“…B4: passive RF receivers are affected by false detections, as any ambient traffic within the frequency band would trigger simple envelope detectors. B5: the sensitivity of a passive receiver is very low, in the order of -50 dBm [94,95].…”

“…In fact, tags need to harvest a minimum amount of energy to turn on (harvesting threshold). A tag typically needs a few tens of µW to turn on and begin operation [94], hence the range is usually limited by whether such energy can be obtained from the harvesting source. This presents a scalability challenge: we need dense deployments of high-power RF emitters for ubiquitous harvesting.…”

“…Morpho was presented in [94] to integrate active radio components like oscillators and active amplifiers with passive radio components like backscatter reflectors and envelope detectors. Similar interest has emerged to understand the interaction between radio and acoustic [118].…”