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Ripple Credit System Could Help or Harm Bitcoin

Decentralized, peer-to-peer credit could either be the exchange Bitcoiners want—or the nascent currency’s first credible competition

6 min read
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Photo: Getty Images

14 January 2013—This Christmas season I bought my very first bitcoins. The idea was to give them as gifts to my family, thus setting the Pecks out on the adventure of figuring out how Bitcoin—the four-year-old decentralized, stateless cryptocurrency—works and why it might be important. I enjoy giving homework as a present.

The adventure, however, turned out to be my own, as I first had to find a way to get some bitcoins. Apparently there are a few ways: You can join the network that creates bitcoins and mint them at a slow, unpredictable pace. You can accept them as payment. You can buy them from a centralized exchange. Or you can find a random stranger online who wants to sell them and meet up with him on the street. I chose the latter, an option that landed me in a coffee shop three days before Christmas, handing over US $100 cash to a man I had never met, whose father had promised to immediately transfer me bitcoins from his home in the Caribbean.

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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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