Battery-free Communication System for Over 100,000 Simultaneous Internet Connectivity

Massive connectivity is a key to Internet of Things (IoT). However, IoT is unable to live up to the scale due spectrum shortage and high energy consumption. This research is the first battery-free communication system supporting hundreds of thousands of simultaneous Internet connectivity.

Article | Spring 2023

With the Internet of Things (IoT) anticipated to grow up to a trillion devices by 2035 and 6G aiming at 10/m2 density, massive connectivity has long been considered a key to the success of IoT. However, the current IoT is unable to live up to the scale, due to the shortage of the spectrum and high energy consumption (thus short battery life). This study presents a new battery-free communication that supports hundreds of thousands of simultaneous communications. It uses a backscatter system that communicates by reflecting the signals in the air, instead of generating its own signal, consuming only 7 microwatts of power. The system runs without batteries via energy harvesters. It can operate over 40 years with a single coin cell battery.

The system operates in the millimeter wave band (> 24GHz), offering an abundant spectrum resource ranging up to 14 GHz bandwidth in the 60 GHz carrier.; A bandwidth over two orders of magnitude greater than 26 MHz and 100 MHz in the popular 900 MHz and 2.4 GHz carriers, respectively. A substantial downside of the millimeter wave is the severe signal attenuation due to the high frequency, which makes backscatter signals particularly error-prone, as they are inherently low in power. The study proposes a new signal processing that exploits the interplay between the backscatter signal and the radar to boost the signal quality by over seven orders of magnitude. In addition, the signal processing improves the connectivity by tens of thousands over 5G/6G, paving a practical pathway to massive IoT.

To enable massive-scale simultaneous communication, the system leverages the distance-frequency relationship in the radar to automatically allocate channels to the devices according to the devices’ physical locations. This avoids any coordination cost and the channel switching overhead for the devices, enabling the low-power and low-end devices to exploit the wide millimeter wave bandwidth without the power-hungry components (e.g., high-frequency local oscillators) and without the complicated network protocol for coordination. The system scales to hundreds of thousands of simultaneous connectivity.