Wi-Fi may soon come on a lamppost near you

As Wi-Fi is more widespread in cities and perhaps at higher frequencies, it may depend on an abundance of urban assets: street lighting poles.

To ensure that these networks work well, researchers from the National Institute of Standards and Technology (NIST) have developed and validated new model this will help wireless providers analyze how high to attach Wi-Fi equipment to light poles.

In general, the NIST team found that the optimal height depends on the transmission frequency and antenna design. Mounting equipment at lower altitudes of about 4 meters is better for traditional wireless systems with omnidirectional antennas, while higher places 6 or 9 meters above are better for the latest systems such as 5G using more high frequencies of millimeter waves and narrow beam antennas.

International Group, Telecom Infra project, encourages the idea of ​​providing Wi-Fi access in the unlicensed 60 GHz band by installing access points on light poles. A technical challenge is that the signals in this band, which are higher than the frequencies of traditional mobile phones, are rare and tend to be distracted by rough surfaces.

So far, measurements of urban channels at 60 GHz have yielded limited data. NIST has developed a channel tracking model that recognizes the rare, scattered characteristics of these signals and uses a new algorithm to analyze measured paths that extends beyond the usual delay parameters and signal angles to include receiver locations. The prediction accuracy of the model is comparable to that of more sophisticated methods.

NIST researchers traveled to downtown Boulder, Colorado, to test their model against actual canal measurements. Measurements were recorded at 4, 6 and 9 meters of antenna height to investigate trade-offs. The model matches very well with the actual measurements.

“We tested the model we developed and used measurements from the city center to further prove this point,” said Derek Kaudil, an electronics engineer working on the project at NIST. “This work shows that using our model, someone as a cell provider can take into account the various advantages and disadvantages of 60 GHz access points and signals for lighting poles in urban environments.

The team uses NIST’s personalized equipment, called a siren, with a stationary mast-mounted transmitter and a mobile receiver on the roof of the van. The transmitter and receiver are covered with a set of electronically switched antennas with defined 3D radiation patterns. The signal can accurately measure many characteristics of the radio channel and has a unique ability to measure the dynamics of time – how the properties of the waves change over time as the receiver moves – on a millimeter wave channel, even when in motion.

Researchers were particularly interested in data on how signals propagate in physical space. Large spreads are generally considered bad because they show more signals and more interference. In general, it is better to have a clear path for communication.

“Our data show that these spreads are wider at higher altitudes,” said NIST engineer Jelena Senic. “This means that with fewer obstacles between the transmitter and receiver, power is more distributed in space.”

For conventional wireless systems with omnidirectional antennas, shorter distances are preferable to avoid interference, which means that Wi-Fi equipment must be mounted at a lower height on lampposts.

“However, next-generation wireless systems will operate at millimeter-wave frequencies and must use highly directional antennas with very narrow beams or pencil beams,” Senik said. “With this configuration, the transmitter and receiver will direct their narrow beams to find the best possible connection; that is, the path of propagation that has maximum power. In this case, greater angular scattering is preferable because it will provide diversity in the space; that is, the transceivers will have the ability to direct the beams in more directions to find the best connection. “

NIST researchers went even further and recorded the measurement data on NIST’s campus to confirm that the new model could be applied in a variety of settings. The results on campus were comparable to the city center, which proves that the model can be summarized for different environments and uses.

Reports: SY Jun, C. Lai, D. Caudill, J. Wang, J. Senic, N. Varshney and C. Gentile. Quasi-deterministic channel propagation model for 60 GHz urban WiFi access from light poles. IEEE antennas and letters for wireless distribution. Published online April 29, 2022 DOI: 10.1109 / LAWP.2022.3171503