No more changing or charging batteries? Ericsson and the Massachusetts Institute of Technology (MIT) have teamed up to develop techniques for absorbing energy from the environment for the Internet of Things (IoT). “Energy harvesting” naturally produces very little energy; other research groups have already tried to crack this nut. With Zero Energy Devices, the partners are now coining another term with a focus on mobile radio devices and networks for industrial applications.
For 4G and 5G networks, various specifications for frugal radio operation have already been written down and in some cases also implemented (massive machine-type communication, e.g. for remote meter reading). NarrowBand Internet of Things (NB-IoT) and LTE for machines (LTE-M) are designed for data rates of a few hundred kilobits per second and, under optimal conditions, can get by with a button cell for up to ten years.
However, the approach is uneconomical if you have to change the batteries of tens of thousands of devices on a regular basis. In addition, the battery life depends on the length of the transmission and reception intervals: It drops significantly if an NB-IoT or LTE-M device communicates every few minutes.
Ericsson describes in one Blog post the challenges for zero-energy devices that are supposed to get by without batteries. They obtain the energy required for operation from the environment – from vibrations, light, temperature gradients or high-frequency waves such as those emitted by TV transmitters and cell phone base stations. You collect them, but Ericsson does not comment on the storage method.
Where is the energy limit?
Such radio modules could be placed in shipping packages in order to simplify storage and also to report the temperature or humidity inside the packaging. Another scenario is the monitoring of environmental parameters at remote locations.
Previous energy harvesting methods often only take a few microwatts from the environment, which is far below the need for today’s more economical devices. Even the most economical transceivers need energy in the milliwatt range.
The low energy level results in an upper limit for the amount of data that can be transmitted. Although it depends heavily on the radio distance and the conditions, it is usually only a few bytes. One trick to get by with the limited energy supply is to spark less often. However, because the availability of energy and the quality of the transmission channel fluctuate over the course of the day or year, the devices are in principle only available sporadically. Completely new specifications for the physical transmission layer are therefore required.
Authentication and encryption are also major challenges. According to Ericsson, the energy required to encrypt the device identity (IMSI) alone requires as much energy in current NB-IoT devices as current energy harvesting techniques only collect within days. Therefore want Ericsson and MIT develop new, more energy-efficient security mechanisms. Completely new circuits that can manage with the low amounts of energy are also required.
In c’t 24/2021 we present our optimal PC 2022 to you. In addition to a detailed purchase advice, we describe two concrete construction proposals: an expandable, quiet all-rounder and a cheap mini-PC. We also tested music streaming services and looked at what 3D sound was good for. You will find issue 24/2021 from November 5th in Heise shop and at the well-stocked newspaper kiosk.