MIT Researchers Develop Smart Surface to Boost Signal Strength Without Adding Extra Antennas

Achieving high-speed 5G internet without more efficient ways of delivering wireless signals is a challenging task. One solution is the addition of extra antennas to either the transmitter (i.e., Wi-Fi access points and cell towers) or the receiver (such as a phone or laptop). But its implementation is difficult, as companies are increasingly producing smaller and smaller devices, including a new wave of “internet of things” systems. And yet, while high-speed 5G internet has indeed slowly been rolling out across the globe, many barriers remain that have prevented widespread adoption.

Researchers from MIT's Computer Science and Artificial Intelligence Laboratory (CSAIL) are working towards achieving high-speed 5G internet without adding extra antennas to either the transmitter or the receiver. To tackle this issue, the CSAIL team has proposed an idea, rather than focusing on the transmitters and receivers, what if we could amplify the signal by adding antennas to an external surface in the environment itself? They are developing a new system called RFocus, a software-controlled “smart surface” that uses more than 3,000 antennas to maximize the strength of the signal at the receiver. Tests showed that RFocus could improve the average signal strength by a factor of almost 10. Practically speaking, the platform is also very cost-effective, with each antenna costing only a few cents. The antennas are inexpensive because they don’t process the signal at all; they merely control how it is reflected. 

According to Venkat Arun, Lead Author and a Ph.D. student, ‘the project represents what is, to the team’s knowledge, the largest number of antennas ever used for a single communication link.’ While the system could serve as another form of the WiFi range extender, the researchers say its most valuable use could be in the network-connected homes and factories of the future. 

For example, imagine a warehouse with hundreds of sensors for monitoring machines and inventory. MIT Professor Hari Balakrishnan stated that ‘systems for that type of scale would normally be prohibitively expensive and/or power-intensive, but could be possible with a low-power interconnected system that uses an approach like RFocus.’ In a new paper on RFocus that will be presented next month at the USENIX Symposium on Networked Systems Design and Implementation (NSDI) in Santa Clara, California, Professor Balakrishnan also added, ‘The core goal here was to explore whether we can use elements in the environment and arrange them to direct the signal in a way that we can actually control. If you want to have wireless devices that transmit at the lowest possible power, but give you a good signal, this seems to be one extremely promising way to do it.’

RFocus is a two-dimensional surface composed of thousands of antennas that can each either let the signal through or reflect it. The state of the elements is set by a software controller that the team developed with the goal of maximizing the signal strength at a receiver. According to Venkat Arun, ‘The biggest challenge was determining how to configure the antennas to maximize signal strength without using any additional sensors since the signals we measure are very weak.’

The researchers aren’t the first to explore the possibility of improving internet speeds using the external environment. A team at Princeton University led by Professor Kyle Jamieson also proposed a similar scheme for the specific situation of people using computers on either side of a wall. Balakrishnan also added that ‘the goal with RFocus was to develop an even more low-cost approach that could be used in a wider range of scenarios.’

Smart surfaces give us literally thousands of antennas to play around with. The best way of controlling all these antennas, and navigating the massive search space with all the possible antenna configurations, are just two really challenging open problems.

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