Streetlight Wi-Fi Hotspots: A Bright Idea

Wi-Fi deployed via streetlights—the vision of an international consortium founded by Intel, Facebook, Nokia and others—may one day help augment wireless access throughout cities. However, much remains unknown about the most apt placement for these access points. Now a novel algorithm could help telecommunications companies discover how to best install this infrastructure, a new study finds.

The international Telecom Infra Project envisions making public Wi-Fi available via the 60-gigahertz frequency band (ranging from 57 to 73 GHz) by installing access points on light poles. This band is unlicensed, and the IEEE 802.11ay standard for 60-GHz Wi-Fi released in 2021 supports up to 8.64 GHz of bandwidth.

A challenge that comes along with using 60-GHz signals is that oxygen absorption exacerbates attenuation, thus limiting their range. If wireless links using these frequencies are relatively short—less than 100 meters—they may still prove useful in dense urban areas. However, much remains unknown about the best way to use such transmissions in cities, such as the ideal height for access points to avoid obstructions that might scatter these signals.

In the new study, researchers at the National Institute of Standards and Technology (NIST) in Gaithersburg, Md., developed a model for tracking 60-GHz signals that accounted for wide variances in light poles’ height. It uses a new algorithm for analyzing transmission paths that goes beyond usual parameters such as signal angles and delays to include receiver locations.

The scientists detailed their findings in a paper published in the August issue of IEEE Antennas and Wireless Propagation Letters.

The scientists tested their model in downtown Boulder, Colo., with a stationary transmitter mounted on a mast and a mobile receiver on the roof of a van. They measured signals at 4-, 6-, and 9-meter antenna heights, reflecting the ways in which light-pole heights can vary within and between cities.

The researchers found that their model predicted real-world measurements very well, with an accuracy comparable to that of more complicated methods. In general, the scientists found that the optimal height for Wi-Fi signals depended on the transmission frequency and antenna design. Attaching equipment at lower heights (about 4 meters above street level) proved better for traditional wireless systems with omnidirectional antennas, whereas higher locations 6 or 9 meters up were better for the latest systems such as 5G that use higher, millimeter-wave frequencies and narrow-beam antennas. [READ MORE]