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TV White-Space Networks Get Smart

Bell Labs, Rice University test white-space network hardware

4 min read

27 July 2011—Many technorati still remember what happened to Steve Jobs a year ago. During a demo of the then new iPhone 4, the usually smooth showman was thwarted on stage by his company’s Wi-Fi network, which was clogged by the data demands of the reporters and bloggers in the room.

The failed demo was one of the more visible examples of the need for more wireless bandwidth—a sort of "super Wi-Fi," or as Google founder Larry Page likes to call it, "Wi-Fi on steroids." Such an offering could arrive as a result of the U.S. Federal Communications Commission’s (FCC) release of rules for commercial use of unlicensed television spectrum last year. Several telecom regulatory agencies in other countries plan to follow suit: Brazilian telecommunications regulator Anatel; the Telecom Regulatory Authority of India (TRAI); the State Administration of Radio, Film, and Television in China; and the Infocomm Development Authority of Singapore have all shown interest in freeing up their TV spectrum for use in wireless broadband services.

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Metamaterials Could Solve One of 6G’s Big Problems

There’s plenty of bandwidth available if we use reconfigurable intelligent surfaces

12 min read
An illustration depicting cellphone users at street level in a city, with wireless signals reaching them via reflecting surfaces.

Ground level in a typical urban canyon, shielded by tall buildings, will be inaccessible to some 6G frequencies. Deft placement of reconfigurable intelligent surfaces [yellow] will enable the signals to pervade these areas.

Chris Philpot

For all the tumultuous revolution in wireless technology over the past several decades, there have been a couple of constants. One is the overcrowding of radio bands, and the other is the move to escape that congestion by exploiting higher and higher frequencies. And today, as engineers roll out 5G and plan for 6G wireless, they find themselves at a crossroads: After years of designing superefficient transmitters and receivers, and of compensating for the signal losses at the end points of a radio channel, they’re beginning to realize that they are approaching the practical limits of transmitter and receiver efficiency. From now on, to get high performance as we go to higher frequencies, we will need to engineer the wireless channel itself. But how can we possibly engineer and control a wireless environment, which is determined by a host of factors, many of them random and therefore unpredictable?

Perhaps the most promising solution, right now, is to use reconfigurable intelligent surfaces. These are planar structures typically ranging in size from about 100 square centimeters to about 5 square meters or more, depending on the frequency and other factors. These surfaces use advanced substances called metamaterials to reflect and refract electromagnetic waves. Thin two-dimensional metamaterials, known as metasurfaces, can be designed to sense the local electromagnetic environment and tune the wave’s key properties, such as its amplitude, phase, and polarization, as the wave is reflected or refracted by the surface. So as the waves fall on such a surface, it can alter the incident waves’ direction so as to strengthen the channel. In fact, these metasurfaces can be programmed to make these changes dynamically, reconfiguring the signal in real time in response to changes in the wireless channel. Think of reconfigurable intelligent surfaces as the next evolution of the repeater concept.

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