3D Printed Reflector Improves WiFi Signal and Security in Interior Spaces

Have you ever been stuck waiting somewhere, like a doctor’s office, and really just wanted to check your email while you were sitting there, but the WiFi signal was just too weak? It can be a frustrating situation, especially when the alternative is flipping through really old magazines – they never seem to have current issues at doctor’s offices, I don’t know why. Improving wireless performance inside buildings can be tough, due to complex interactions of radio signals with the surrounding environment. Current wireless signal optimization solutions include using directional antennae to concentrate the signal, but this approach can be expensive, not to mention difficult to configure correctly. But a collaborative team of researchers, led by Dartmouth College, is working to fix this problem so you’re not stuck without a good WiFi signal.

In addition to Dartmouth, which was most recently working on super-strong 4D materials, researchers from Columbia University, the University of Washington, and UC Irvine worked together to use 3D printing technology to inexpensively optimize wireless coverage for indoor spaces with lots of rooms, like your home or office. As an added benefit, by using their solution to improve wireless signal strength, wireless security can also be increased. Their work builds upon studies that placed an aluminum can behind a WiFi access point in order to strengthen the signal in a specific direction.

In a project dubbed WiPrint, the team created an inexpensive, customized, 3D printed reflector that will actually direct wireless signals to where users really need them. They presented their research paper, titled “Customizing Indoor Wireless Coverage via 3D-Fabricated Reflectors,” earlier this week in the Netherlands at ACM’s BuildSys 2017; co-authors include Xi Xiong, Justin Chan, Ethan Yu, Nisha Kumari, Ardalan Amiri Sani, Changxi Zheng, and Xia Zhou.

According to the abstract, “Judicious control of indoor wireless coverage is crucial in built environments. It enhances signal reception, reduces harmful interference, and raises the barrier for malicious attackers. Existing methods are either costly, vulnerable to attacks, or hard to configure. We present a low-cost, secure, and easy-to-configure approach that uses an easily-accessible, 3D-fabricated reflector to customize wireless coverage. With input on coarse-grained environment setting and preferred coverage (e.g., areas with signals to be strengthened or weakened), the system computes an optimized reflector shape tailored to the given environment. The user simply 3D prints the reflector and places it around a Wi-Fi access point to realize the target coverage. We conduct experiments to examine the efficacy and limits of optimized reflectors in different indoor settings. Results show that optimized reflectors coexist with a variety of Wi-Fi APs and correctly weaken or enhance signals in target areas by up to 10 or 6 dB, resulting to throughput changes by up to -63.3% or 55.1%.”

It’s important to customize wireless network coverage inside buildings, so signal reception in areas where it’s being used the most can be improved, while being weakened in others. When WiFi signals are shaped, users can reduce the impact of interior layouts and building materials, which deadens the signal, and increase wireless efficiency.

Xia Zhou

“Through this single solution, we address a number of challenges that plague wireless users. Not only do we strengthen wireless signals, we make those same signals more secure,” Zhou, an assistant professor of computer science at Dartmouth, explained.

“With a simple investment of about $35 and specifying coverage requirements, a wireless reflector can be custom-built to outperform antennae that cost thousands of dollars.”

The researchers designed an algorithm that would optimize a reflector’s 3D shape in order to target wireless coverage, and determined a way to simulate how radio signals spread and interact with other objects. Once the system has wireless access point locations, the desired signal target area, and information on a specific interior space, it takes less than half an hour to compute an optimized reflector shape.

The researchers then edited the reflector using Blender, and 3D printed it on a MakerBot 3D printer. The signal reflector is comprised of plastic and a thin layer of metal, and once they had investigated the layout of the specified interior space, and target areas to weaken or strengthen the strength of the wireless signal, the team placed the “computationally optimized” reflector around a wireless router, where it then redirects wireless signals to the chosen coverage areas.

The team tested their reflector with several off-the-shelf WiFi access points, and in two different interior spaces, before reporting back that their 3D printed device worked like a charm – it was easy to use, provided strong physical security, and was inexpensive to create. The researchers discovered that the reflector was able to decrease wireless signal strength by up to 10 dB where it’s not needed, which increases the signal in areas where it is needed.

This type of system also makes it hard for would-be attackers to hack the signal by physically confining it to limited areas, which also means reduced WiFi interference. However, the current design of the 3D printed reflector has a static shape, which limits it, so the team is now working on reflectors made using different materials, so it will be able to adapt its shape automatically when the interior layout is changed; they will also study higher frequency bands for the reflector, like visible light and millimeter waves.

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[Source: EurekAlert / Images: Dartmouth College]