Using Glass Windows to Boost Mobile Signals

Photograph by Michael Betts

Ericsson engineers have begun experimenting with a new type of cell site—one embedded inside a window. As demand for mobile data grows, networks must get denser. That means building ever-smaller cells and putting them much closer to mobile users. Why not take advantage of the glass surfaces that cover our homes, businesses, and vehicles?

At CTIA Wireless this week, Ericsson networked society evangelist Mats Guldbrand gave me a demo of the technology at the equipment maker’s booth. Basically, a small antenna element is embedded into a pane of shielded glass. That antenna can pick up Wi-Fi or cellular signals from nearby phones, tablets, and laptops and then aggregate those connections, sending them as a combined transmission to the nearest LTE cell tower.

Guldbrand provided as an example a bus containing 50 people, all surfing the internet on smartphones. With each device trying to connect separately to the same tower, you wind up with a big mess: Not only are all those signals interfering with one another, the network is trying to manage 50 simultaneous hand-overs among cell towers. The network might be able to pull it off, but everyone’s experience suffers, Guldbrand says.

If those 50 devices, however, were all connecting to a localized antennae embedded in the vehicle’s windows, the bus could then link to the cellular network through a single transmitter mounted on its roof. It would be much easier for the cellular base station to handle a single, high-capacity connection than a bunch of smaller connections. Everyone in the bus would experience greater speeds and more resilient links; because each device wouldn’t be reaching out to a distant tower, their device battery lives would be enhanced.

This might sound a bit like the repeater or range-booster kits you can buy to enhance your cellphone’s signal at home, but this technology is designed to integrate closely with the network. Ordinarily, a repeater would create all kinds of interference in a crowded network; by using shielded glass, Ericsson can limit the number of competing transmissions bouncing around the cell. The treated windows (and the steel frame) block signals trying to escape the bus, turning it into a kind of Faraday Cage on wheels.

Forthcoming LTE-Advanced technologies will introduce network relay points mounted on bus rooftops and utility poles that would route signals within the cell. The principle is simple: If you can narrow the distance between network hops, you get more resilient and higher-capacity connections.

Ericsson has further plans for connected glass. Guldbrand says that as long as the windows are networked, you could embed all kinds of technology into their surfaces. As part of the demo, Guldbrand showed me a pane of plain glass with an infrared field on its surface. When you interrupt the field with your hand at specific points, you can trigger such actions as turning the lights on and off or skipping among songs on the stereo. Not only might the windows in your future home access the internet, they could replace your light switches and remote controls.

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